resistant material. If slipping hazards cannot be eliminated, slip-
resistant footwear or handrails and stair rails meeting the
requirements of Subpart D of this part may be used instead of slip-
resistant material.
    (ii) Equipment on which employees stand to spray while the vehicle
is in motion shall be equipped with guardrails around the working area.
The guardrail shall be constructed in accordance with Subpart D of this
part.
    (4) Stump cutters. (i) Stump cutters shall be equipped with
enclosures or guards to protect employees.
    (ii) Each employee in the immediate area of stump grinding
operations (including the stump cutter operator) shall wear personal
protective equipment as required by Subpart I of this part.
    (5) Gasoline-engine power saws. Gasoline-engine power saw
operations shall meet the requirements of Sec.  1910.266(e) and the
following:
    (i) Each power saw weighing more than 6.8 kilograms (15 pounds,
service weight) that is used in trees shall be supported by a separate
line, except when work is performed from an aerial lift and except
during topping or removing operations where no supporting limb will be
available.
    (ii) Each power saw shall be equipped with a control that will
return the saw to idling speed when released.
    (iii) Each power saw shall be equipped with a clutch and shall be
so adjusted that the clutch will not engage the chain drive at idling
speed.
    (iv) A power saw shall be started on the ground or where it is
otherwise firmly supported. Drop starting of saws over 6.8 kilograms
(15 pounds), other than chain saws, is permitted outside of the bucket
of an aerial lift only if the area below the lift is clear of
personnel.

    Note to paragraph (r)(5)(iv): Paragraph (e)(2)(vi) of Sec.
1910.266 prohibits drop starting of chain saws.

    (v) A power saw engine may be started and operated only when all
employees other than the operator are clear of the saw.
    (vi) A power saw may not be running when the saw is being carried
up into a tree by an employee.
    (vii) Power saw engines shall be stopped for all cleaning,
refueling, adjustments, and repairs to the saw or motor, except as the
manufacturer's servicing procedures require otherwise.
    (6) Backpack power units for use in pruning and clearing. (i) While
a backpack power unit is running, no one other than the operator may be
within 3.05 meters (10 feet) of the cutting head of a brush saw.
    (ii) A backpack power unit shall be equipped with a quick shutoff
switch readily accessible to the operator.
    (iii) Backpack power unit engines shall be stopped for all
cleaning, refueling, adjustments, and repairs to the saw or motor,
except as the manufacturer's servicing procedures require otherwise.
    (7) Rope. (i) Climbing ropes shall be used by employees working
aloft in trees. These ropes shall have a minimum diameter of 12
millimeters (0.5 inch) with a minimum breaking strength of 10.2
kilonewtons (2,300 pounds). Synthetic rope shall have elasticity of not
more than 7 percent.
    (ii) Rope shall be inspected before each use and, if unsafe (for
example, because of damage or defect), may not be used.
    (iii) Rope shall be stored away from cutting edges and sharp tools.
Rope contact with corrosive chemicals, gas, and oil shall be avoided.
    (iv) When stored, rope shall be coiled and piled, or shall be
suspended, so that air can circulate through the coils.
    (v) Rope ends shall be secured to prevent their unraveling.
    (vi) Climbing rope may not be spliced to effect repair.
    (vii) A rope that is wet, that is contaminated to the extent that
its insulating capacity is impaired, or that is otherwise not
considered to be insulated for the voltage involved may not be used
near exposed energized lines.
    (8) Fall protection. Each employee shall be tied in with a climbing
rope and safety saddle when the employee is working above the ground in
a tree, unless he or she is ascending into the tree.
    (s) Communication facilities. (1) Microwave transmission. (i) The
employer shall ensure that no employee looks into an open waveguide or
antenna connected to an energized microwave source.
    (ii) If the electromagnetic-radiation level within an accessible
area associated with microwave communications systems exceeds the
radiation-protection guide specified by Sec.  1910.97(a)(2), the
employer shall post the area with warning signs containing the warning
symbol described in Sec.  1910.97(a)(3). The lower half of the warning
symbol shall include the following statements, or ones that the
employer can demonstrate are equivalent: ``Radiation in this area may
exceed hazard limitations and special precautions are required. Obtain
specific instruction before entering.''
    (iii) When an employee works in an area where the electromagnetic
radiation could exceed the radiation-protection guide, the employer
shall institute measures that ensure that the employee's exposure is
not greater than that permitted by that guide. Such measures may
include administrative and engineering controls and personal protective
equipment.
    (2) Power-line carrier. The employer shall ensure that employees
perform power-line carrier work, including work on equipment used for
coupling carrier current to power line conductors, in accordance with
the requirements of this section pertaining to work on energized lines.

    (t) Underground electrical installations. This paragraph provides
additional requirements for work on underground electrical
installations.
    (1) Access. The employer shall ensure that employees use a ladder
or other climbing device to enter and exit a manhole or subsurface
vault exceeding 1.22 meters (4 feet) in depth. No employee may climb
into or out of a manhole or vault by stepping on cables or hangers.
    (2) Lowering equipment into manholes. (i) Equipment used to lower
materials and tools into manholes or vaults shall be capable of
supporting the weight to be lowered and shall be checked for defects
before use.
    (ii) Before anyone lowers tools or material into the opening for a
manhole or vault, each employee working in the manhole or vault shall
be clear of the area directly under the opening.
    (3) Attendants for manholes and vaults. (i) While work is being
performed in a manhole or vault containing energized electric
equipment, an employee with first-aid training shall be available on
the surface in the immediate vicinity of the manhole or vault entrance
to render emergency assistance.
    (ii) Occasionally, the employee on the surface may briefly enter a
manhole or vault to provide nonemergency assistance.

    Note 1 to paragraph (t)(3)(ii): Paragraph (e)(7) of this section
may also require an attendant and does not permit this attendant to
enter the manhole or vault.

    Note 2 to paragraph (t)(3)(ii): Paragraph (l)(1)(ii) of this
section requires employees entering manholes or vaults containing
unguarded, uninsulated energized lines or parts of electric
equipment operating at 50 volts or more to be qualified.

    (iii) For the purpose of inspection, housekeeping, taking readings,
or similar work, an employee working alone may enter, for brief periods
of time, a manhole or vault where energized cables or equipment are in
service if the employer can demonstrate that the employee will be
protected from all electrical hazards.
    (iv) The employer shall ensure that employees maintain reliable
communications, through two-way radios or other equivalent means, among
all employees involved in the job.
    (4) Duct rods. The employer shall ensure that, if employees use
duct rods, the employees install the duct rods in the direction
presenting the least hazard to employees. The employer shall station an
employee at the far end of the duct line being rodded to ensure that
the employees maintain the required minimum approach distances.
    (5) Multiple cables. When multiple cables are present in a work
area, the employer shall identify the cable to be worked by electrical
means, unless its identity is obvious by reason of distinctive
appearance or location or by other readily apparent means of
identification. The employer shall protect cables other than the one
being worked from damage.
    (6) Moving cables. Except when paragraph (t)(7)(ii) of this section
permits employees to perform work that could cause a fault in an
energized cable in a manhole or vault, the employer shall ensure that
employees inspect energized cables to be moved for abnormalities.
    (7) Protection against faults. (i) Where a cable in a manhole or
vault has one or more abnormalities that could lead to a fault or be an
indication of an impending fault, the employer shall deenergize the
cable with the abnormality before any employee may work in the manhole
or vault, except when service-load conditions and a lack of feasible
alternatives require that the cable remain energized. In that case,
employees may enter the manhole or vault provided the employer protects
them from the possible effects of a failure using shields or other
devices that are capable of containing the adverse effects of a fault.
The employer shall treat the following abnormalities as indications of
impending faults unless the employer can demonstrate that the
conditions could not lead to a fault: Oil or compound leaking from
cable or joints, broken cable sheaths or joint sleeves, hot localized
surface temperatures of cables or joints, or joints swollen beyond
normal tolerance.
    (ii) If the work employees will perform in a manhole or vault could
cause a fault in a cable, the employer shall deenergize that cable
before any employee works in the manhole or vault, except when service-
load conditions and a lack of feasible alternatives require that the
cable remain energized. In that case, employees may enter the manhole
or vault provided the employer protects them from the possible effects
of a failure using shields or other devices that are capable of
containing the adverse effects of a fault.
    (8) Sheath continuity. When employees perform work on buried cable
or on cable in a manhole or vault, the employer shall maintain
metallic-sheath continuity, or the cable sheath shall be treated as
energized.
    (u) Substations. This paragraph provides additional requirements
for substations and for work performed in them.
    (1) Access and working space. The employer shall provide and
maintain sufficient access and working space about electric equipment
to permit ready and safe operation and maintenance of such equipment by
employees.

    Note to paragraph (u)(1): American National Standard National
Electrical Safety Code, ANSI/IEEE C2-2012 contains guidelines for
the dimensions of access and working space about electric equipment
in substations. Installations meeting the ANSI provisions comply
with paragraph (u)(1) of this section. The Occupational Safety and
Health Administration will determine whether an installation that
does not conform to this ANSI standard complies with paragraph
(u)(1) of this section based on the following criteria:
    (1) Whether the installation conforms to the edition of ANSI C2
that was in effect when the installation was made,
    (2) Whether the configuration of the installation enables
employees to maintain the minimum approach distances, established by
the employer under paragraph (l)(3)(i) of this section, while the
employees are working on exposed, energized parts, and
    (3) Whether the precautions taken when employees perform work on
the installation provide protection equivalent to the protection
provided by access and working space meeting ANSI/IEEE C2-2012.

    (2) Draw-out-type circuit breakers. The employer shall ensure that,
when employees remove or insert draw-out-type circuit breakers, the
breaker is in the open position. The employer shall also render the
control circuit inoperable if the design of the equipment permits.
    (3) Substation fences. Conductive fences around substations shall
be grounded. When a substation fence is expanded or a section is
removed, fence sections shall be isolated, grounded, or bonded as
necessary to protect employees from hazardous differences in electric
potential.

    Note to paragraph (u)(3): IEEE Std 80-2000, IEEE Guide for
Safety in AC Substation Grounding, contains guidelines for
protection against hazardous differences in electric potential.

    (4) Guarding of rooms and other spaces containing electric supply
equipment. (i) Rooms and other spaces in which electric supply lines or
equipment are installed shall meet the requirements of paragraphs
(u)(4)(ii) through (u)(4)(v) of this section under the following
conditions:
    (A) If exposed live parts operating at 50 to 150 volts to ground
are within 2.4 meters (8 feet) of the ground or other working surface
inside the room or other space,

    (B) If live parts operating at 151 to 600 volts to ground and
located within 2.4 meters (8 feet) of the ground or other working
surface inside the room or other space are guarded only by location, as
permitted under paragraph (u)(5)(i) of this section, or
    (C) If live parts operating at more than 600 volts to ground are
within the room or other space, unless:
    (1) The live parts are enclosed within grounded, metal-enclosed
equipment whose only openings are designed so that foreign objects
inserted in these openings will be deflected from energized parts, or
    (2) The live parts are installed at a height, above ground and any
other working surface, that provides protection at the voltage on the
live parts corresponding to the protection provided by a 2.4-meter (8-
foot) height at 50 volts.
    (ii) Fences, screens, partitions, or walls shall enclose the rooms
and other spaces so as to minimize the possibility that unqualified
persons will enter.
    (iii) Unqualified persons may not enter the rooms or other spaces
while the electric supply lines or equipment are energized.
    (iv) The employer shall display signs at entrances to the rooms and
other spaces warning unqualified persons to keep out.
    (v) The employer shall keep each entrance to a room or other space
locked, unless the entrance is under the observation of a person who is
attending the room or other space for the purpose of preventing
unqualified employees from entering.
    (5) Guarding of energized parts. (i) The employer shall provide
guards around all live parts operating at more than 150 volts to ground
without an insulating covering unless the location of the live parts
gives sufficient clearance (horizontal, vertical, or both) to minimize
the possibility of accidental employee contact.

    Note to paragraph (u)(5)(i): American National Standard National
Electrical Safety Code, ANSI/IEEE C2-2002 contains guidelines for
the dimensions of clearance distances about electric equipment in
substations. Installations meeting the ANSI provisions comply with
paragraph (u)(5)(i) of this section. The Occupational Safety and
Health Administration will determine whether an installation that
does not conform to this ANSI standard complies with paragraph
(u)(5)(i) of this section based on the following criteria:
    (1) Whether the installation conforms to the edition of ANSI C2
that was in effect when the installation was made,
    (2) Whether each employee is isolated from energized parts at
the point of closest approach; and
    (3) Whether the precautions taken when employees perform work on
the installation provide protection equivalent to the protection
provided by horizontal and vertical clearances meeting ANSI/IEEE C2-
2002.

    (ii) Except for fuse replacement and other necessary access by
qualified persons, the employer shall maintain guarding of energized
parts within a compartment during operation and maintenance functions
to prevent accidental contact with energized parts and to prevent
dropped tools or other equipment from contacting energized parts.
    (iii) Before guards are removed from energized equipment, the
employer shall install barriers around the work area to prevent
employees who are not working on the equipment, but who are in the
area, from contacting the exposed live parts.
    (6) Substation entry. (i) Upon entering an attended substation,
each employee, other than employees regularly working in the station,
shall report his or her presence to the employee in charge of
substation activities to receive information on special system
conditions affecting employee safety.
    (ii) The job briefing required by paragraph (c) of this section
shall cover information on special system conditions affecting employee
safety, including the location of energized equipment in or adjacent to
the work area and the limits of any deenergized work area.
    (v) Power generation. This paragraph provides additional
requirements and related work practices for power generating plants.
    (1) Interlocks and other safety devices. (i) Interlocks and other
safety devices shall be maintained in a safe, operable condition.
    (ii) No interlock or other safety device may be modified to defeat
its function, except for test, repair, or adjustment of the device.
    (2) Changing brushes. Before exciter or generator brushes are
changed while the generator is in service, the exciter or generator
field shall be checked to determine whether a ground condition exists.
The brushes may not be changed while the generator is energized if a
ground condition exists.
    (3) Access and working space. The employer shall provide and
maintain sufficient access and working space about electric equipment
to permit ready and safe operation and maintenance of such equipment by
employees.

    Note to paragraph (v)(3) of this section:  American National
Standard National Electrical Safety Code, ANSI/IEEE C2-2012 contains
guidelines for the dimensions of access and working space about
electric equipment in substations. Installations meeting the ANSI
provisions comply with paragraph (v)(3) of this section. The
Occupational Safety and Health Administration will determine whether
an installation that does not conform to this ANSI standard complies
with paragraph (v)(3) of this section based on the following
criteria:
    (1) Whether the installation conforms to the edition of ANSI C2
that was in effect when the installation was made;
    (2) Whether the configuration of the installation enables
employees to maintain the minimum approach distances, established by
the employer under paragraph (l)(3)(i) of this section, while the
employees are working on exposed, energized parts, and;
    (3) Whether the precautions taken when employees perform work on
the installation provide protection equivalent to the protection
provided by access and working space meeting ANSI/IEEE C2-2012.

    (4) Guarding of rooms and other spaces containing electric supply
equipment. (i) Rooms and other spaces in which electric supply lines or
equipment are installed shall meet the requirements of paragraphs
(v)(4)(ii) through (v)(4)(v) of this section under the following
conditions:
    (A) If exposed live parts operating at 50 to 150 volts to ground
are within 2.4 meters (8 feet) of the ground or other working surface
inside the room or other space,
    (B) If live parts operating at 151 to 600 volts to ground and
located within 2.4 meters (8 feet) of the ground or other working
surface inside the room or other space are guarded only by location, as
permitted under paragraph (v)(5)(i) of this section, or
    (C) If live parts operating at more than 600 volts to ground are
within the room or other space, unless:
    (1) The live parts are enclosed within grounded, metal-enclosed
equipment whose only openings are designed so that foreign objects
inserted in these openings will be deflected from energized parts, or
    (2) The live parts are installed at a height, above ground and any
other working surface, that provides protection at the voltage on the
live parts corresponding to the protection provided by a 2.4-meter (8-
foot) height at 50 volts.
    (ii) Fences, screens, partitions, or walls shall enclose the rooms
and other spaces so as to minimize the possibility that unqualified
persons will enter.
    (iii) Unqualified persons may not enter the rooms or other spaces
while the electric supply lines or equipment are energized.

    (iv) The employer shall display signs at entrances to the rooms and
other spaces warning unqualified persons to keep out.
    (v) The employer shall keep each entrance to a room or other space
locked, unless the entrance is under the observation of a person who is
attending the room or other space for the purpose of preventing
unqualified employees from entering.
    (5) Guarding of energized parts. (i) The employer shall provide
guards around all live parts operating at more than 150 volts to ground
without an insulating covering unless the location of the live parts
gives sufficient clearance (horizontal, vertical, or both) to minimize
the possibility of accidental employee contact.

    Note to paragraph (v)(5)(i): American National Standard National
Electrical Safety Code, ANSI/IEEE C2-2002 contains guidelines for
the dimensions of clearance distances about electric equipment in
substations. Installations meeting the ANSI provisions comply with
paragraph (v)(5)(i) of this section. The Occupational Safety and
Health Administration will determine whether an installation that
does not conform to this ANSI standard complies with paragraph
(v)(5)(i) of this section based on the following criteria:
    (1) Whether the installation conforms to the edition of ANSI C2
that was in effect when the installation was made;
    (2) Whether each employee is isolated from energized parts at
the point of closest approach; and
    (3) Whether the precautions taken when employees perform work on
the installation provide protection equivalent to the protection
provided by horizontal and vertical clearances meeting ANSI/IEEE C2-
2002.

    (ii) Except for fuse replacement and other necessary access by
qualified persons, the employer shall maintain guarding of energized
parts within a compartment during operation and maintenance functions
to prevent accidental contact with energized parts and to prevent
dropped tools or other equipment from contacting energized parts.
    (iii) Before guards are removed from energized equipment, the
employer shall install barriers around the work area to prevent
employees who are not working on the equipment, but who are in the
area, from contacting the exposed live parts.
    (6) Water or steam spaces. The following requirements apply to work
in water and steam spaces associated with boilers:
    (i) A designated employee shall inspect conditions before work is
permitted and after its completion. Eye protection, or full face
protection if necessary, shall be worn at all times when condenser,
heater, or boiler tubes are being cleaned.
    (ii) Where it is necessary for employees to work near tube ends
during cleaning, shielding shall be installed at the tube ends.
    (7) Chemical cleaning of boilers and pressure vessels. The
following requirements apply to chemical cleaning of boilers and
pressure vessels:
    (i) Areas where chemical cleaning is in progress shall be cordoned
off to restrict access during cleaning. If flammable liquids, gases, or
vapors or combustible materials will be used or might be produced
during the cleaning process, the following requirements also apply:
    (A) The area shall be posted with signs restricting entry and
warning of the hazards of fire and explosion; and
    (B) Smoking, welding, and other possible ignition sources are
prohibited in these restricted areas.
    (ii) The number of personnel in the restricted area shall be
limited to those necessary to accomplish the task safely.
    (iii) There shall be ready access to water or showers for emergency
use.

    Note to paragraph (v)(7)(iii): See Sec.  1910.141 for
requirements that apply to the water supply and to washing
facilities.

    (iv) Employees in restricted areas shall wear protective equipment
meeting the requirements of Subpart I of this part and including, but
not limited to, protective clothing, boots, goggles, and gloves.
    (8) Chlorine systems. (i) Chlorine system enclosures shall be
posted with signs restricting entry and warning of the hazard to health
and the hazards of fire and explosion.

    Note to paragraph (v)(8)(i): See Subpart Z of this part for
requirements necessary to protect the health of employees from the
effects of chlorine.

    (ii) Only designated employees may enter the restricted area.
Additionally, the number of personnel shall be limited to those
necessary to accomplish the task safely.
    (iii) Emergency repair kits shall be available near the shelter or
enclosure to allow for the prompt repair of leaks in chlorine lines,
equipment, or containers.
    (iv) Before repair procedures are started, chlorine tanks, pipes,
and equipment shall be purged with dry air and isolated from other
sources of chlorine.
    (v) The employer shall ensure that chlorine is not mixed with
materials that would react with the chlorine in a dangerously
exothermic or other hazardous manner.
    (9) Boilers. (i) Before internal furnace or ash hopper repair work
is started, overhead areas shall be inspected for possible falling
objects. If the hazard of falling objects exists, overhead protection
such as planking or nets shall be provided.
    (ii) When opening an operating boiler door, employees shall stand
clear of the opening of the door to avoid the heat blast and gases
which may escape from the boiler.
    (10) Turbine generators. (i) Smoking and other ignition sources are
prohibited near hydrogen or hydrogen sealing systems, and signs warning
of the danger of explosion and fire shall be posted.
    (ii) Excessive hydrogen makeup or abnormal loss of pressure shall
be considered as an emergency and shall be corrected immediately.
    (iii) A sufficient quantity of inert gas shall be available to
purge the hydrogen from the largest generator.
    (11) Coal and ash handling. (i) Only designated persons may operate
railroad equipment.
    (ii) Before a locomotive or locomotive crane is moved, a warning
shall be given to employees in the area.
    (iii) Employees engaged in switching or dumping cars may not use
their feet to line up drawheads.
    (iv) Drawheads and knuckles may not be shifted while locomotives or
cars are in motion.
    (v) When a railroad car is stopped for unloading, the car shall be
secured from displacement that could endanger employees.
    (vi) An emergency means of stopping dump operations shall be
provided at railcar dumps.
    (vii) The employer shall ensure that employees who work in coal- or
ash-handling conveyor areas are trained and knowledgeable in conveyor
operation and in the requirements of paragraphs (v)(11)(viii) through
(v)(11)(xii) of this section.
    (viii) Employees may not ride a coal- or ash-handling conveyor belt
at any time. Employees may not cross over the conveyor belt, except at
walkways, unless the conveyor's energy source has been deenergized and
has been locked out or tagged in accordance with paragraph (d) of this
section.
    (ix) A conveyor that could cause injury when started may not be
started until personnel in the area are alerted by a signal or by a
designated person that the conveyor is about to start.
    (x) If a conveyor that could cause injury when started is
automatically controlled or is controlled from a remote location, an
audible device shall be provided that sounds an alarm that will be
recognized by each employee as a warning that the conveyor will start
and

that can be clearly heard at all points along the conveyor where
personnel may be present. The warning device shall be actuated by the
device starting the conveyor and shall continue for a period of time
before the conveyor starts that is long enough to allow employees to
move clear of the conveyor system. A visual warning may be used in
place of the audible device if the employer can demonstrate that it
will provide an equally effective warning in the particular
circumstances involved. However if the employer can demonstrate that
the system's function would be seriously hindered by the required time
delay, warning signs may be provided in place of the audible warning
device. If the system was installed before January 31, 1995, warning
signs may be provided in place of the audible warning device until such
time as the conveyor or its control system is rebuilt or rewired. These
warning signs shall be clear, concise, and legible and shall indicate
that conveyors and allied equipment may be started at any time, that
danger exists, and that personnel must keep clear. These warning signs
shall be provided along the conveyor at areas not guarded by position
or location.
    (xi) Remotely and automatically controlled conveyors, and conveyors
that have operating stations which are not manned or which are beyond
voice and visual contact from drive areas, loading areas, transfer
points, and other locations on the conveyor path not guarded by
location, position, or guards shall be furnished with emergency stop
buttons, pull cords, limit switches, or similar emergency stop devices.
However, if the employer can demonstrate that the design, function, and
operation of the conveyor do not expose an employee to hazards, an
emergency stop device is not required.
    (A) Emergency stop devices shall be easily identifiable in the
immediate vicinity of such locations.
    (B) An emergency stop device shall act directly on the control of
the conveyor involved and may not depend on the stopping of any other
equipment.
    (C) Emergency stop devices shall be installed so that they cannot
be overridden from other locations.
    (xii) Where coal-handling operations may produce a combustible
atmosphere from fuel sources or from flammable gases or dust, sources
of ignition shall be eliminated or safely controlled to prevent
ignition of the combustible atmosphere.

    Note to paragraph (v)(11)(xii): Locations that are hazardous
because of the presence of combustible dust are classified as Class
II hazardous locations. See Sec.  1910.307.

    (xiii) An employee may not work on or beneath overhanging coal in
coal bunkers, coal silos, or coal storage areas, unless the employee is
protected from all hazards posed by shifting coal.
    (xiv) An employee entering a bunker or silo to dislodge the
contents shall wear a body harness with lifeline attached. The lifeline
shall be secured to a fixed support outside the bunker and shall be
attended at all times by an employee located outside the bunker or
facility.
    (12) Hydroplants and equipment. Employees working on or close to
water gates, valves, intakes, forebays, flumes, or other locations
where increased or decreased water flow or levels may pose a
significant hazard shall be warned and shall vacate such dangerous
areas before water flow changes are made.
    (w) Special conditions. (1) Capacitors. The following additional
requirements apply to work on capacitors and on lines connected to
capacitors.

    Note to paragraph (w)(1): See paragraphs (m) and (n) of this
section for requirements pertaining to the deenergizing and
grounding of capacitor installations.

    (i) Before employees work on capacitors, the employer shall
disconnect the capacitors from energized sources and short circuit the
capacitors. The employer shall ensure that the employee short
circuiting the capacitors waits at least 5 minutes from the time of
disconnection before applying the short circuit,
    (ii) Before employees handle the units, the employer shall short
circuit each unit in series-parallel capacitor banks between all
terminals and the capacitor case or its rack. If the cases of
capacitors are on ungrounded substation racks, the employer shall bond
the racks to ground.
    (iii) The employer shall short circuit any line connected to
capacitors before the line is treated as deenergized.
    (2) Current transformer secondaries. The employer shall ensure that
employees do not open the secondary of a current transformer while the
transformer is energized. If the employer cannot deenergize the primary
of the current transformer before employees perform work on an
instrument, a relay, or other section of a current transformer
secondary circuit, the employer shall bridge the circuit so that the
current transformer secondary does not experience an open-circuit
condition.
    (3) Series streetlighting. (i) If the open-circuit voltage exceeds
600 volts, the employer shall ensure that employees work on series
streetlighting circuits in accordance with paragraph (q) or (t) of this
section, as appropriate.
    (ii) Before any employee opens a series loop, the employer shall
deenergize the streetlighting transformer and isolate it from the
source of supply or shall bridge the loop to avoid an open-circuit
condition.
    (4) Illumination. The employer shall provide sufficient
illumination to enable the employee to perform the work safely.
    (5) Protection against drowning. (i) Whenever an employee may be
pulled or pushed, or might fall, into water where the danger of
drowning exists, the employer shall provide the employee with, and
shall ensure that the employee uses, a U.S. Coast Guard-approved
personal flotation device.
    (ii) The employer shall maintain each personal flotation device in
safe condition and shall inspect each personal flotation device
frequently enough to ensure that it does not have rot, mildew, water
saturation, or any other condition that could render the device
unsuitable for use.
    (iii) An employee may cross streams or other bodies of water only
if a safe means of passage, such as a bridge, is available.
    (6) Employee protection in public work areas. (i) Traffic-control
signs and traffic-control devices used for the protection of employees
shall meet Sec.  1926.200(g)(2) of this chapter.
    (ii) Before employees begin work in the vicinity of vehicular or
pedestrian traffic that may endanger them, the employer shall place
warning signs or flags and other traffic-control devices in conspicuous
locations to alert and channel approaching traffic.
    (iii) The employer shall use barricades where additional employee
protection is necessary.
    (iv) The employer shall protect excavated areas with barricades.
    (v) The employer shall display warning lights prominently at night.
    (7) Backfeed. When there is a possibility of voltage backfeed from
sources of cogeneration or from the secondary system (for example,
backfeed from more than one energized phase feeding a common load), the
requirements of paragraph (l) of this section apply if employees will
work the lines or equipment as energized, and the requirements of
paragraphs (m) and (n) of this section apply if employees will work the
lines or equipment as deenergized.
    (8) Lasers. The employer shall install, adjust, and operate laser
equipment in accordance with Sec.  1926.54 of this chapter.
    (9) Hydraulic fluids. Hydraulic fluids used for the insulated
sections of

equipment shall provide insulation for the voltage involved.
    (x) Definitions.
    Affected employee. An employee whose job requires him or her to
operate or use a machine or equipment on which servicing or maintenance
is being performed under lockout or tagout, or whose job requires him
or her to work in an area in which such servicing or maintenance is
being performed.
    Attendant. An employee assigned to remain immediately outside the
entrance to an enclosed or other space to render assistance as needed
to employees inside the space.
    Authorized employee. An employee who locks out or tags out machines
or equipment in order to perform servicing or maintenance on that
machine or equipment. An affected employee becomes an authorized
employee when that employee's duties include performing servicing or
maintenance covered under this section.
    Automatic circuit recloser. A self-controlled device for
automatically interrupting and reclosing an alternating-current
circuit, with a predetermined sequence of opening and reclosing
followed by resetting, hold closed, or lockout.
    Barricade. A physical obstruction such as tapes, cones, or A-frame
type wood or metal structures that provides a warning about, and limits
access to, a hazardous area.
    Barrier. A physical obstruction that prevents contact with
energized lines or equipment or prevents unauthorized access to a work
area.
    Bond. The electrical interconnection of conductive parts designed
to maintain a common electric potential.
    Bus. A conductor or a group of conductors that serve as a common
connection for two or more circuits.
    Bushing. An insulating structure that includes a through conductor
or that provides a passageway for such a conductor, and that, when
mounted on a barrier, insulates the conductor from the barrier for the
purpose of conducting current from one side of the barrier to the
other.
    Cable. A conductor with insulation, or a stranded conductor with or
without insulation and other coverings (single-conductor cable), or a
combination of conductors insulated from one another (multiple-
conductor cable).
    Cable sheath. A conductive protective covering applied to cables.

    Note to the definition of ``cable sheath'': A cable sheath may
consist of multiple layers one or more of which is conductive.

    Circuit. A conductor or system of conductors through which an
electric current is intended to flow.
    Clearance (between objects). The clear distance between two objects
measured surface to surface.
    Clearance (for work). Authorization to perform specified work or
permission to enter a restricted area.
    Communication lines. (See Lines; (1) Communication lines.)
    Conductor. A material, usually in the form of a wire, cable, or bus
bar, used for carrying an electric current.
    Contract employer. An employer, other than a host employer, that
performs work covered by this section under contract.
    Covered conductor. A conductor covered with a dielectric having no
rated insulating strength or having a rated insulating strength less
than the voltage of the circuit in which the conductor is used.
    Current-carrying part. A conducting part intended to be connected
in an electric circuit to a source of voltage. Non-current-carrying
parts are those not intended to be so connected.
    Deenergized. Free from any electrical connection to a source of
potential difference and from electric charge; not having a potential
that is different from the potential of the earth.

    Note to the definition of ``deenergized'': The term applies only
to current-carrying parts, which are sometimes energized (alive).

    Designated employee (designated person). An employee (or person)
who is assigned by the employer to perform specific duties under the
terms of this section and who has sufficient knowledge of the
construction and operation of the equipment, and the hazards involved,
to perform his or her duties safely.
    Electric line truck. A truck used to transport personnel, tools,
and material for electric supply line work.
    Electric supply equipment. Equipment that produces, modifies,
regulates, controls, or safeguards a supply of electric energy.
    Electric supply lines. (See Lines; (2) Electric supply lines.)
    Electric utility. An organization responsible for the installation,
operation, or maintenance of an electric supply system.
    Enclosed space. A working space, such as a manhole, vault, tunnel,
or shaft, that has a limited means of egress or entry, that is designed
for periodic employee entry under normal operating conditions, and
that, under normal conditions, does not contain a hazardous atmosphere,
but may contain a hazardous atmosphere under abnormal conditions.

    Note to the definition of ``enclosed space'': The Occupational
Safety and Health Administration does not consider spaces that are
enclosed but not designed for employee entry under normal operating
conditions to be enclosed spaces for the purposes of this section.
Similarly, the Occupational Safety and Health Administration does
not consider spaces that are enclosed and that are expected to
contain a hazardous atmosphere to be enclosed spaces for the
purposes of this section. Such spaces meet the definition of permit
spaces in Sec.  1910.146, and entry into them must conform to that
standard.

    Energized (alive, live). Electrically connected to a source of
potential difference, or electrically charged so as to have a potential
significantly different from that of earth in the vicinity.
    Energy isolating device. A physical device that prevents the
transmission or release of energy, including, but not limited to, the
following: a manually operated electric circuit breaker, a disconnect
switch, a manually operated switch, a slide gate, a slip blind, a line
valve, blocks, and any similar device with a visible indication of the
position of the device. (Push buttons, selector switches, and other
control-circuit-type devices are not energy isolating devices.)
    Energy source. Any electrical, mechanical, hydraulic, pneumatic,
chemical, nuclear, thermal, or other energy source that could cause
injury to employees.
    Entry (as used in paragraph (e) of this section). The action by
which a person passes through an opening into an enclosed space. Entry
includes ensuing work activities in that space and is considered to
have occurred as soon as any part of the entrant's body breaks the
plane of an opening into the space.
    Equipment (electric). A general term including material, fittings,
devices, appliances, fixtures, apparatus, and the like used as part of
or in connection with an electrical installation.
    Exposed, Exposed to contact (as applied to energized parts). Not
isolated or guarded.
    Fall restraint system. A fall protection system that prevents the
user from falling any distance.
    First-aid training. Training in the initial care, including
cardiopulmonary resuscitation (which includes chest compressions,
rescue breathing, and, as appropriate, other heart and lung
resuscitation techniques), performed by a person who is not a medical
practitioner, of a sick or injured person until definitive medical
treatment can be administered.
    Ground. A conducting connection, whether planned or unplanned,
between an electric circuit or equipment and the earth, or to some
conducting body that serves in place of the earth.

    Grounded. Connected to earth or to some conducting body that serves
in place of the earth.
    Guarded. Covered, fenced, enclosed, or otherwise protected, by
means of suitable covers or casings, barrier rails or screens, mats, or
platforms, designed to minimize the possibility, under normal
conditions, of dangerous approach or inadvertent contact by persons or
objects.

    Note to the definition of ``guarded'': Wires that are insulated,
but not otherwise protected, are not guarded.

    Hazardous atmosphere. An atmosphere that may expose employees to
the risk of death, incapacitation, impairment of ability to self-rescue
(that is, escape unaided from an enclosed space), injury, or acute
illness from one or more of the following causes:
    (1) Flammable gas, vapor, or mist in excess of 10 percent of its
lower flammable limit (LFL);
    (2) Airborne combustible dust at a concentration that meets or
exceeds its LFL;

    Note to the definition of ``hazardous atmosphere'' (2): This
concentration may be approximated as a condition in which the dust
obscures vision at a distance of 1.52 meters (5 feet) or less.

    (3) Atmospheric oxygen concentration below 19.5 percent or above
23.5 percent;
    (4) Atmospheric concentration of any substance for which a dose or
a permissible exposure limit is published in Subpart G, Occupational
Health and Environmental Control, or in Subpart Z, Toxic and Hazardous
Substances, of this part and which could result in employee exposure in
excess of its dose or permissible exposure limit;

    Note to the definition of ``hazardous atmosphere'' (4): An
atmospheric concentration of any substance that is not capable of
causing death, incapacitation, impairment of ability to self-rescue,
injury, or acute illness due to its health effects is not covered by
this provision.

    (5) Any other atmospheric condition that is immediately dangerous
to life or health.

    Note to the definition of ``hazardous atmosphere'' (5): For air
contaminants for which the Occupational Safety and Health
Administration has not determined a dose or permissible exposure
limit, other sources of information, such as Material Safety Data
Sheets that comply with the Hazard Communication Standard, Sec.
1910.1200, published information, and internal documents can provide
guidance in establishing acceptable atmospheric conditions.

    High-power tests. Tests in which the employer uses fault currents,
load currents, magnetizing currents, and line-dropping currents to test
equipment, either at the equipment's rated voltage or at lower
voltages.
    High-voltage tests. Tests in which the employer uses voltages of
approximately 1,000 volts as a practical minimum and in which the
voltage source has sufficient energy to cause injury.
    High wind. A wind of such velocity that one or more of the
following hazards would be present:
    (1) The wind could blow an employee from an elevated location,
    (2) The wind could cause an employee or equipment handling material
to lose control of the material, or
    (3) The wind would expose an employee to other hazards not
controlled by the standard involved.

    Note to the definition of ``high wind'': The Occupational Safety
and Health Administration normally considers winds exceeding 64.4
kilometers per hour (40 miles per hour), or 48.3 kilometers per hour
(30 miles per hour) if the work involves material handling, as
meeting this criteria, unless the employer takes precautions to
protect employees from the hazardous effects of the wind.

    Host employer. An employer that operates, or that controls the
operating procedures for, an electric power generation, transmission,
or distribution installation on which a contract employer is performing
work covered by this section.

    Note to the definition of ``host employer'': The Occupational
Safety and Health Administration will treat the electric utility or
the owner of the installation as the host employer if it operates or
controls operating procedures for the installation. If the electric
utility or installation owner neither operates nor controls
operating procedures for the installation, the Occupational Safety
and Health Administration will treat the employer that the utility
or owner has contracted with to operate or control the operating
procedures for the installation as the host employer. In no case
will there be more than one host employer.

    Immediately dangerous to life or health (IDLH). Any condition that
poses an immediate or delayed threat to life or that would cause
irreversible adverse health effects or that would interfere with an
individual's ability to escape unaided from a permit space.

    Note to the definition of ``immediately dangerous to life or
health'': Some materials--hydrogen fluoride gas and cadmium vapor,
for example--may produce immediate transient effects that, even if
severe, may pass without medical attention, but are followed by
sudden, possibly fatal collapse 12-72 hours after exposure. The
victim ``feels normal'' from recovery from transient effects until
collapse. Such materials in hazardous quantities are considered to
be ``immediately'' dangerous to life or health.

    Insulated. Separated from other conducting surfaces by a dielectric
(including air space) offering a high resistance to the passage of
current.

    Note to the definition of ``insulated'': When any object is said
to be insulated, it is understood to be insulated for the conditions
to which it normally is subjected. Otherwise, it is, for the purpose
of this section, uninsulated.

    Insulation (cable). Material relied upon to insulate the conductor
from other conductors or conducting parts or from ground.
    Isolated. Not readily accessible to persons unless special means
for access are used.
    Line-clearance tree trimmer. An employee who, through related
training or on-the-job experience or both, is familiar with the special
techniques and hazards involved in line-clearance tree trimming.

    Note 1 to the definition of ``line-clearance tree trimmer'': An
employee who is regularly assigned to a line-clearance tree-trimming
crew and who is undergoing on-the-job training and who, in the
course of such training, has demonstrated an ability to perform
duties safely at his or her level of training and who is under the
direct supervision of a line-clearance tree trimmer is considered to
be a line-clearance tree trimmer for the performance of those
duties.

    Note 2 to the definition of ``line-clearance tree trimmer'': A
line-clearance tree trimmer is not considered to be a ``qualified
employee'' under this section unless he or she has the training
required for a qualified employee under paragraph (a)(2)(ii) of this
section. However, under the electrical safety-related work practices
standard in Subpart S of this part, a line-clearance tree trimmer is
considered to be a ``qualified employee''. Tree trimming performed
by such ``qualified employees'' is not subject to the electrical
safety-related work practice requirements contained in Sec. Sec.
1910.331 through 1910.335 of this part. (See also the note following
Sec.  1910.332(b)(3) of this part for information regarding the
training an employee must have to be considered a qualified employee
under Sec. Sec.  1910.331 through 1910.335 of this part.)

    Line-clearance tree trimming. The pruning, trimming, repairing,
maintaining, removing, or clearing of trees, or the cutting of brush,
that is within the following distance of electric supply lines and
equipment:
    (1) For voltages to ground of 50 kilovolts or less--3.05 meters (10
feet);
    (2) For voltages to ground of more than 50 kilovolts--3.05 meters
(10 feet) plus 0.10 meters (4 inches) for every 10 kilovolts over 50
kilovolts.

    Lines. (1) Communication lines. The conductors and their supporting
or containing structures which are used for public or private signal or
communication service, and which operate at potentials not exceeding
400 volts to ground or 750 volts between any two points of the circuit,
and the transmitted power of which does not exceed 150 watts. If the
lines are operating at less than 150 volts, no limit is placed on the
transmitted power of the system. Under certain conditions,
communication cables may include communication circuits exceeding these
limitations where such circuits are also used to supply power solely to
communication equipment.

    Note to the definition of ``communication lines'': Telephone,
telegraph, railroad signal, data, clock, fire, police alarm, cable
television, and other systems conforming to this definition are
included. Lines used for signaling purposes, but not included under
this definition, are considered as electric supply lines of the same
voltage.

    (2) Electric supply lines. Conductors used to transmit electric
energy and their necessary supporting or containing structures. Signal
lines of more than 400 volts are always supply lines within this
section, and those of less than 400 volts are considered as supply
lines, if so run and operated throughout.
    Manhole. A subsurface enclosure that personnel may enter and that
is used for installing, operating, and maintaining submersible
equipment or cable.
    Minimum approach distance. The closest distance an employee may
approach an energized or a grounded object.

    Note to the definition of ``minimum approach distance'':
Paragraph (l)(3)(i) of this section requires employers to establish
minimum approach distances.

    Personal fall arrest system. A system used to arrest an employee in
a fall from a working level.
    Qualified employee (qualified person). An employee (person)
knowledgeable in the construction and operation of the electric power
generation, transmission, and distribution equipment involved, along
with the associated hazards.

    Note 1 to the definition of ``qualified employee (qualified
person)'': An employee must have the training required by (a)(2)(ii)
of this section to be a qualified employee.

    Note 2 to the definition of ``qualified employee (qualified
person)'': Except under (g)(2)(iv)(C)(2) and (g)(2)(iv)(C)(3) of
this section, an employee who is undergoing on-the-job training and
who has demonstrated, in the course of such training, an ability to
perform duties safely at his or her level of training and who is
under the direct supervision of a qualified person is a qualified
person for the performance of those duties.

    Statistical sparkover voltage. A transient overvoltage level that
produces a 97.72-percent probability of sparkover (that is, two
standard deviations above the voltage at which there is a 50-percent
probability of sparkover).
    Statistical withstand voltage. A transient overvoltage level that
produces a 0.14-percent probability of sparkover (that is, three
standard deviations below the voltage at which there is a 50-percent
probability of sparkover).
    Switch. A device for opening and closing or for changing the
connection of a circuit. In this section, a switch is manually
operable, unless otherwise stated.
    System operator. A qualified person designated to operate the
system or its parts.
    Vault. An enclosure, above or below ground, that personnel may
enter and that is used for installing, operating, or maintaining
equipment or cable.
    Vented vault. A vault that has provision for air changes using
exhaust-flue stacks and low-level air intakes operating on pressure and
temperature differentials that provide for airflow that precludes a
hazardous atmosphere from developing.
    Voltage. The effective (root mean square, or rms) potential
difference between any two conductors or between a conductor and
ground. This section expresses voltages in nominal values, unless
otherwise indicated. The nominal voltage of a system or circuit is the
value assigned to a system or circuit of a given voltage class for the
purpose of convenient designation. The operating voltage of the system
may vary above or below this value.
    Work-positioning equipment. A body belt or body harness system
rigged to allow an employee to be supported on an elevated vertical
surface, such as a utility pole or tower leg, and work with both hands
free while leaning.

Appendix A to Sec.  1910.269--Flow Charts

    This appendix presents information, in the form of flow charts,
that illustrates the scope and application of Sec.  1910.269. This
appendix addresses the interface between Sec.  1910.269 and Subpart
S of this Part (Electrical), between Sec.  1910.269 and Sec.
1910.146 (Permit-required confined spaces), and between Sec.
1910.269 and Sec.  1910.147 (The control of hazardous energy
(lockout/tagout)). These flow charts provide guidance for employers
trying to implement the requirements of Sec.  1910.269 in
combination with other General Industry Standards contained in Part
1910. Employers should always consult the relevant standards, in
conjunction with this appendix, to ensure compliance with all
applicable requirements.
BILLING CODE 4510-26-P

[GRAPHIC] [TIFF OMITTED] TR11AP14.018

[GRAPHIC] [TIFF OMITTED] TR11AP14.019

[GRAPHIC] [TIFF OMITTED] TR11AP14.020

[GRAPHIC] [TIFF OMITTED] TR11AP14.021

[GRAPHIC] [TIFF OMITTED] TR11AP14.022

[GRAPHIC] [TIFF OMITTED] TR11AP14.023

Appendix B to Sec.  1910.269--Working on Exposed Energized Parts

I. Introduction

    Electric utilities design electric power generation,
transmission, and distribution installations to meet National
Electrical Safety Code (NESC), ANSI C2, requirements. Electric
utilities also design transmission and distribution lines to limit
line outages as required by system reliability criteria \1\ and to
withstand the maximum overvoltages impressed on the system.
Conditions such as switching surges, faults, and lightning can cause
overvoltages. Electric utilities generally select insulator design
and lengths and the clearances to structural parts so as to prevent
outages from contaminated line insulation and during storms. Line
insulator lengths and structural clearances have, over the years,
come closer to the minimum approach distances used by workers. As
minimum approach distances and structural clearances converge, it is
increasingly important that system designers and system operating
and maintenance personnel understand the concepts underlying minimum
approach distances.
---------------------------------------------------------------------------

    \1\ Federal, State, and local regulatory bodies and electric
utilities set reliability requirements that limit the number and
duration of system outages.
---------------------------------------------------------------------------

    The information in this appendix will assist employers in
complying with the minimum approach-distance requirements contained
in Sec.  1910.269(l)(3) and (q)(3). Employers must use the technical
criteria and methodology presented in this appendix in establishing
minimum approach distances in accordance with Sec.
1910.269(l)(3)(i) and Table R-3 and Table R-8. This appendix
provides essential background information and technical criteria for
the calculation of the required minimum approach distances for live-
line work on electric power generation, transmission, and
distribution installations.
    Unless an employer is using the maximum transient overvoltages
specified in Table R-9 for voltages over 72.5 kilovolts, the
employer must use persons knowledgeable in the techniques discussed
in this appendix, and competent in the field of electric
transmission and distribution system design, to determine the
maximum transient overvoltage.

II. General

    A. Definitions. The following definitions from Sec.  1910.269(x)
relate to work on or near electric power generation, transmission,
and distribution lines and equipment and the electrical hazards they
present.
    Exposed. . . . Not isolated or guarded.
    Guarded. Covered, fenced, enclosed, or otherwise protected, by
means of suitable covers or casings, barrier rails or screens, mats,
or platforms, designed to minimize the possibility, under normal
conditions, of dangerous approach or inadvertent contact by persons
or objects.

    Note to the definition of ``guarded'': Wires that are insulated,
but not otherwise protected, are not guarded.

    Insulated. Separated from other conducting surfaces by a
dielectric (including air space) offering a high resistance to the
passage of current.

    Note to the definition of ``insulated'': When any object is said
to be insulated, it is understood to be insulated for the conditions
to which it normally is subjected. Otherwise, it is, for the purpose
of this section, uninsulated.

    Isolated. Not readily accessible to persons unless special means
for access are used.
    Statistical sparkover voltage. A transient overvoltage level
that produces a 97.72-percent probability of sparkover (that is, two
standard deviations above the voltage at which there is a 50-percent
probability of sparkover).
    Statistical withstand voltage. A transient overvoltage level
that produces a 0.14-percent probability of sparkover (that is,
three standard deviations below the voltage at which there is a 50-
percent probability of sparkover).
    B. Installations energized at 50 to 300 volts. The hazards posed
by installations energized at 50 to 300 volts are the same as those
found in many other workplaces. That is not to say that there is no
hazard, but the complexity of electrical protection required does
not compare to that required for high-voltage systems. The employee
must avoid contact with the exposed parts, and the protective
equipment used (such as rubber insulating gloves) must provide
insulation for the voltages involved.
    C. Exposed energized parts over 300 volts AC. Paragraph
(l)(3)(i) of Sec.  1910.269 requires the employer to establish
minimum approach distances no less than the distances computed by
Table R-3 for ac systems so that employees can work safely without
risk of sparkover.\2\
---------------------------------------------------------------------------

    \2\ Sparkover is a disruptive electric discharge in which an
electric arc forms and electric current passes through air.
---------------------------------------------------------------------------

    Unless the employee is using electrical protective equipment,
air is the insulating medium between the employee and energized
parts. The distance between the employee and an energized part must
be sufficient for the air to withstand the maximum transient
overvoltage that can reach the worksite under the working conditions
and practices the employee is using. This distance is the minimum
air insulation distance, and it is equal to the electrical component
of the minimum approach distance.
    Normal system design may provide or include a means (such as
lightning arrestors) to control maximum anticipated transient
overvoltages, or the employer may use temporary devices (portable
protective gaps) or measures (such as preventing automatic circuit
breaker reclosing) to achieve the same result. Paragraph (l)(3)(ii)
of Sec.  1910.269 requires the employer to determine the maximum
anticipated per-unit transient overvoltage, phase-to-ground, through
an engineering analysis or assume a maximum anticipated per-unit
transient overvoltage, phase-to-ground, in accordance with Table R-
9, which specifies the following maximums for ac systems:

72.6 to 420.0 kilovolts--3.5 per unit
420.1 to 550.0 kilovolts--3.0 per unit
550.1 to 800.0 kilovolts--2.5 per unit

    See paragraph IV.A.2, later in this appendix, for additional
discussion of maximum transient overvoltages.
    D. Types of exposures. Employees working on or near energized
electric power generation, transmission, and distribution systems
face two kinds of exposures: Phase-to-ground and phase-to-phase. The
exposure is phase-to-ground: (1) With respect to an energized part,
when the employee is at ground potential or (2) with respect to
ground, when an employee is at the potential of the energized part
during live-line barehand work. The exposure is phase-to-phase, with
respect to an energized part, when an employee is at the potential
of another energized part (at a different potential) during live-
line barehand work.

III. Determination of Minimum Approach Distances for AC Voltages
Greater Than 300 Volts

    A. Voltages of 301 to 5,000 volts. Test data generally forms the
basis of minimum air insulation distances. The lowest voltage for
which sufficient test data exists is 5,000 volts, and these data
indicate that the minimum air insulation distance at that voltage is
20 millimeters (1 inch). Because the minimum air insulation distance
increases with increasing voltage, and, conversely, decreases with
decreasing voltage, an assumed minimum air insulation distance of 20
millimeters will protect against sparkover at voltages of 301 to
5,000 volts. Thus, 20 millimeters is the electrical component of the
minimum approach distance for these voltages.
    B. Voltages of 5.1 to 72.5 kilovolts. For voltages from 5.1 to
72.5 kilovolts, the Occupational Safety and Health Administration
bases the methodology for calculating the electrical component of
the minimum approach distance on Institute of Electrical and
Electronic Engineers (IEEE) Standard 4-1995, Standard Techniques for
High-Voltage Testing. Table 1 lists the critical sparkover distances
from that standard as listed in IEEE Std 516-2009, IEEE Guide for
Maintenance Methods on Energized Power Lines.

             Table 1--Sparkover Distance for Rod-to-Rod Gap
------------------------------------------------------------------------
                                                        Gap spacing from
         60 Hz Rod-to-Rod sparkover (kV peak)            IEEE Std 4-1995
                                                              (cm)
------------------------------------------------------------------------
25....................................................                 2
36....................................................                 3
46....................................................                 4
53....................................................                 5
60....................................................                 6
70....................................................                 8
79....................................................                10
86....................................................                12
95....................................................                14
104...................................................                16
112...................................................                18
120...................................................                20
143...................................................                25
167...................................................                30
192...................................................                35
218...................................................                40
243...................................................                45
270...................................................                50
322...................................................                60
------------------------------------------------------------------------
Source: IEEE Std 516-2009.

    To use this table to determine the electrical component of the
minimum approach distance, the employer must determine the peak
phase-to-ground transient overvoltage and select a gap from the
table that corresponds to that voltage as a withstand voltage rather
than a critical sparkover voltage. To calculate the electrical
component of the minimum approach distance for voltages between 5
and 72.5 kilovolts, use the following procedure:
    1. Divide the phase-to-phase voltage by the square root of 3 to
convert it to a phase-to-ground voltage.
    2. Multiply the phase-to-ground voltage by the square root of 2
to convert the rms value of the voltage to the peak phase-to-ground
voltage.
    3. Multiply the peak phase-to-ground voltage by the maximum per-
unit transient overvoltage, which, for this voltage range, is 3.0,
as discussed later in this appendix. This is the maximum phase-to-
ground transient overvoltage, which corresponds to the withstand
voltage for the relevant exposure.\3\
---------------------------------------------------------------------------

    \3\ The withstand voltage is the voltage at which sparkover is
not likely to occur across a specified distance. It is the voltage
taken at the 3[sigma] point below the sparkover voltage, assuming
that the sparkover curve follows a normal distribution.
---------------------------------------------------------------------------

    4. Divide the maximum phase-to-ground transient overvoltage by
0.85 to determine the corresponding critical sparkover voltage. (The
critical sparkover voltage is 3 standard deviations (or 15 percent)
greater than the withstand voltage.)
    5. Determine the electrical component of the minimum approach
distance from Table 1 through interpolation.
    Table 2 illustrates how to derive the electrical component of
the minimum approach distance for voltages from 5.1 to 72.5
kilovolts, before the application of any altitude correction factor,
as explained later.

                      Table 2--Calculating the Electrical Component of MAD 751 V to 72.5 kV
----------------------------------------------------------------------------------------------------------------
                                                        Maximum system phase-to-phase voltage (kV)
                  Step                   -----------------------------------------------------------------------
                                                 15                36                46               72.5
----------------------------------------------------------------------------------------------------------------
1. Divide by [radic]3...................               8.7              20.8              26.6              41.9
2. Multiply by [radic]2.................              12.2              29.4              37.6              59.2
3. Multiply by 3.0......................              36.7              88.2             112.7             177.6
4. Divide by 0.85.......................              43.2             103.7             132.6             208.9
5. Interpolate from Table 1.............      3+(7.2/10)*1      14+(8.7/9)*2    20+(12.6/23)*5    35+(16.9/26)*5
Electrical component of MAD (cm)........              3.72             15.93             22.74             38.25
----------------------------------------------------------------------------------------------------------------

    C. Voltages of 72.6 to 800 kilovolts. For voltages of 72.6
kilovolts to 800 kilovolts, this section bases the electrical
component of minimum approach distances, before the application of
any altitude correction factor, on the following formula:

Equation 1--For Voltages of 72.6 kV to 800 kV

D = 0.3048(C + a) VL-GT

Where:

D = Electrical component of the minimum approach distance in air in
meters;
C = a correction factor associated with the variation of gap
sparkover with voltage;
a = A factor relating to the saturation of air at system voltages of
345 kilovolts or higher; \4\
---------------------------------------------------------------------------

    \4\ Test data demonstrates that the saturation factor is greater
than 0 at peak voltages of about 630 kilovolts. Systems operating at
345 kilovolts (or maximum system voltages of 362 kilovolts) can have
peak maximum transient overvoltages exceeding 630 kilovolts. Table
R-3 sets equations for calculating a based on peak voltage.
---------------------------------------------------------------------------

VL-G = Maximum system line-to-ground rms voltage in kilovolts--it
should be the ``actual'' maximum, or the normal highest voltage for
the range (for example, 10 percent above the nominal voltage); and
T = Maximum transient overvoltage factor in per unit.

    In Equation 1, C is 0.01: (1) For phase-to-ground exposures that
the employer can demonstrate consist only of air across the approach
distance (gap) and (2) for phase-to-phase exposures if the employer
can demonstrate that no insulated tool spans the gap and that no
large conductive object is in the gap. Otherwise, C is 0.011.
    In Equation 1, the term a varies depending on whether the
employee's exposure is phase-to-ground or phase-to-phase and on
whether objects are in the gap. The employer must use the equations
in Table 3 to calculate a. Sparkover test data with insulation
spanning the gap form the basis for the equations for phase-to-
ground exposures, and sparkover test data with only air in the gap
form the basis for the equations for phase-to-phase exposures. The
phase-to-ground equations result in slightly higher values of a,
and, consequently, produce larger minimum approach distances, than
the phase-to-phase equations for the same value of VPeak.

                             Table 3--Equations for Calculating the Surge Factor, a
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
                                            Phase-to-ground exposures
----------------------------------------------------------------------------------------------------------------
VPeak = TL-GVL-G [radic]2.........           635 kV or less           635.1 to 915 kV         915.1 to 1,050 kV
a.................................                        0      (VPeak- 635)/140,000       (VPeak-645)/135,000
                                   -----------------------------------------------------------------------------
VPeak = TL-GVL-G[radic]2..........                               More than 1,050 kV
                                   -----------------------------------------------------------------------------
a.................................                               (VPeak-675)/125,000
----------------------------------------------------------------------------------------------------------------
                                          Phase-to-phase exposures \1\
----------------------------------------------------------------------------------------------------------------
VPeak = (1.35TL-G + 0.45)VL-                 630 kV or less           630.1 to 848 kV         848.1 to 1,131 kV
 G[radic]2........................
a.................................                        0       (VPeak-630)/155,000     (VPeak-633.6)/152,207
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
VPeak = (1.35TL-G + 0.45)VL-                          1,131.1 to 1,485 kV                    More than 1,485 kV
 G[radic]2..........................
a...................................                  (VPeak-628)/153,846                 (VPeak-350.5)/203,666
\1\ Use the equations for phase-to-ground exposures (with VPeak for phase-to-phase exposures) unless the
  employer can demonstrate that no insulated tool spans the gap and that no large conductive object is in the
  gap.

    In Equation 1, T is the maximum transient overvoltage factor in
per unit. As noted earlier, Sec.  1910.269(l)(3)(ii) requires the
employer to determine the maximum anticipated per-unit transient
overvoltage, phase-to-ground, through an engineering analysis or
assume a maximum anticipated per-unit transient overvoltage, phase-
to-ground, in accordance with Table R-9. For phase-to-ground
exposures, the employer uses this value, called TL-G, as T in
Equation 1. IEEE Std 516-2009 provides the following formula to
calculate the phase-to-phase maximum transient overvoltage, TL-L,
from TL-G:

TL-L = 1.35TL-G + 0.45

For phase-to-phase exposures, the employer uses this value as T in
Equation 1.
    D. Provisions for inadvertent movement. The minimum approach
distance must include an ``adder'' to compensate for the inadvertent
movement of the worker relative to an energized part or the movement
of the part relative to the worker. This ``adder'' must account for
this possible inadvertent movement and provide the worker with a
comfortable and safe zone in which to work. Employers must add the
distance for inadvertent movement (called the ``ergonomic component
of the minimum approach distance'') to the electrical component to
determine the total safe minimum approach distances used in live-
line work.
    The Occupational Safety and Health Administration based the
ergonomic component of the minimum approach distance on response
time-distance analysis. This technique uses an estimate of the total
response time to a hazardous incident and converts that time to the
distance traveled. For example, the driver of a car takes a given
amount of time to respond to a ``stimulus'' and stop the vehicle.
The elapsed time involved results in the car's traveling some
distance before coming to a complete stop. This distance depends on
the speed of the car

at the time the stimulus appears and the reaction time of the
driver.
    In the case of live-line work, the employee must first perceive
that he or she is approaching the danger zone. Then, the worker
responds to the danger and must decelerate and stop all motion
toward the energized part. During the time it takes to stop, the
employee will travel some distance. This is the distance the
employer must add to the electrical component of the minimum
approach distance to obtain the total safe minimum approach
distance.
    At voltages from 751 volts to 72.5 kilovolts,\5\ the electrical
component of the minimum approach distance is smaller than the
ergonomic component. At 72.5 kilovolts, the electrical component is
only a little more than 0.3 meters (1 foot). An ergonomic component
of the minimum approach distance must provide for all the worker's
unanticipated movements. At these voltages, workers generally use
rubber insulating gloves; however, these gloves protect only a
worker's hands and arms. Therefore, the energized object must be at
a safe approach distance to protect the worker's face. In this case,
0.61 meters (2 feet) is a sufficient and practical ergonomic
component of the minimum approach distance.
---------------------------------------------------------------------------

    \5\ For voltages of 50 to 300 volts, Table R-3 specifies a
minimum approach distance of ``avoid contact.'' The minimum approach
distance for this voltage range contains neither an electrical
component nor an ergonomic component.
---------------------------------------------------------------------------

    For voltages between 72.6 and 800 kilovolts, employees must use
different work practices during energized line work. Generally,
employees use live-line tools (hot sticks) to perform work on
energized equipment. These tools, by design, keep the energized part
at a constant distance from the employee and, thus, maintain the
appropriate minimum approach distance automatically.
    The location of the worker and the type of work methods the
worker is using also influence the length of the ergonomic component
of the minimum approach distance. In this higher voltage range, the
employees use work methods that more tightly control their movements
than when the workers perform work using rubber insulating gloves.
The worker, therefore, is farther from the energized line or
equipment and must be more precise in his or her movements just to
perform the work. For these reasons, this section adopts an
ergonomic component of the minimum approach distance of 0.31 m (1
foot) for voltages between 72.6 and 800 kilovolts.
    Table 4 summarizes the ergonomic component of the minimum
approach distance for various voltage ranges.

        Table 4--Ergonomic Component of Minimum Approach Distance
------------------------------------------------------------------------
                                                   Distance
         Voltage range (kV)          -----------------------------------
                                              m                ft
------------------------------------------------------------------------
0.301 to 0.750......................              0.31               1.0
0.751 to 72.5.......................              0.61               2.0
72.6 to 800.........................              0.31               1.0
------------------------------------------------------------------------
Note: The employer must add this distance to the electrical component of
  the minimum approach distance to obtain the full minimum approach
  distance.

    The ergonomic component of the minimum approach distance
accounts for errors in maintaining the minimum approach distance
(which might occur, for example, if an employee misjudges the length
of a conductive object he or she is holding), and for errors in
judging the minimum approach distance. The ergonomic component also
accounts for inadvertent movements by the employee, such as
slipping. In contrast, the working position selected to properly
maintain the minimum approach distance must account for all of an
employee's reasonably likely movements and still permit the employee
to adhere to the applicable minimum approach distance. (See Figure
1.) Reasonably likely movements include an employee's adjustments to
tools, equipment, and working positions and all movements needed to
perform the work. For example, the employee should be able to
perform all of the following actions without straying into the
minimum approach distance:
     Adjust his or her hardhat,
     maneuver a tool onto an energized part with a
reasonable amount of overreaching or underreaching,
     reach for and handle tools, material, and equipment
passed to him or her, and
     adjust tools, and replace components on them, when
necessary during the work procedure.
    The training of qualified employees required under Sec.
1910.269(a)(2), and the job planning and briefing required under
Sec.  1910.269(c), must address selection of a proper working
position.
BILLING CODE 4510-26-P

[GRAPHIC] [TIFF OMITTED] TR11AP14.024

BILLING CODE 4510-26-C
    E. Miscellaneous correction factors. Changes in the air medium
that forms the insulation influences the strength of an air gap. A
brief discussion of each factor follows.
    1. Dielectric strength of air. The dielectric strength of air in
a uniform electric field at standard atmospheric conditions is
approximately 3 kilovolts per millimeter.\6\ The pressure,
temperature, and humidity of the air, the shape, dimensions, and
separation of the electrodes, and the

characteristics of the applied voltage (wave shape) affect the
disruptive gradient.
---------------------------------------------------------------------------

    \6\ For the purposes of estimating arc length, Sec.  1910.269
generally assumes a more conservative dielectric strength of 10
kilovolts per 25.4 millimeters, consistent with assumptions made in
consensus standards such as the National Electrical Safety Code
(IEEE C2-2012). The more conservative value accounts for variables
such as electrode shape, wave shape, and a certain amount of
overvoltage.
---------------------------------------------------------------------------

    2. Atmospheric effect. The empirically determined electrical
strength of a given gap is normally applicable at standard
atmospheric conditions (20 [deg]C, 101.3 kilopascals, 11 grams/cubic
centimeter humidity). An increase in the density (humidity) of the
air inhibits sparkover for a given air gap. The combination of
temperature and air pressure that results in the lowest gap
sparkover voltage is high temperature and low pressure. This
combination of conditions is not likely to occur. Low air pressure,
generally associated with high humidity, causes increased electrical
strength. An average air pressure generally correlates with low
humidity. Hot and dry working conditions normally result in reduced
electrical strength. The equations for minimum approach distances in
Table R-3 assume standard atmospheric conditions.
    3. Altitude. The reduced air pressure at high altitudes causes a
reduction in the electrical strength of an air gap. An employer must
increase the minimum approach distance by about 3 percent per 300
meters (1,000 feet) of increased altitude for altitudes above 900
meters (3,000 feet). Table R-5 specifies the altitude correction
factor that the employer must use in calculating minimum approach
distances.

IV. Determining Minimum Approach Distances

A. Factors Affecting Voltage Stress at the Worksite

    1. System voltage (nominal). The nominal system voltage range
determines the voltage for purposes of calculating minimum approach
distances. The employer selects the range in which the nominal
system voltage falls, as given in the relevant table, and uses the
highest value within that range in per-unit calculations.
    2. Transient overvoltages. Operation of switches or circuit
breakers, a fault on a line or circuit or on an adjacent circuit,
and similar activities may generate transient overvoltages on an
electrical system. Each overvoltage has an associated transient
voltage wave shape. The wave shape arriving at the site and its
magnitude vary considerably.
    In developing requirements for minimum approach distances, the
Occupational Safety and Health Administration considered the most
common wave shapes and the magnitude of transient overvoltages found
on electric power generation, transmission, and distribution
systems. The equations in Table R-3 for minimum approach distances
use per-unit maximum transient overvoltages, which are relative to
the nominal maximum voltage of the system. For example, a maximum
transient overvoltage value of 3.0 per unit indicates that the
highest transient overvoltage is 3.0 times the nominal maximum
system voltage.
    3. Typical magnitude of overvoltages. Table 5 lists the
magnitude of typical transient overvoltages.

          Table 5--Magnitude of Typical Transient Overvoltages
------------------------------------------------------------------------
                                                         Magnitude  (per
                         Cause                                unit)
------------------------------------------------------------------------
Energized 200-mile line without closing resistors.....               3.5
Energized 200-mile line with one-step closing resistor               2.1
Energized 200-mile line with multistep resistor.......               2.5
Reclosing with trapped charge one-step resistor.......               2.2
Opening surge with single restrike....................               3.0
Fault initiation unfaulted phase......................               2.1
Fault initiation adjacent circuit.....................               2.5
Fault clearing........................................        1.7 to 1.9
------------------------------------------------------------------------

    4. Standard deviation--air-gap withstand. For each air gap
length under the same atmospheric conditions, there is a statistical
variation in the breakdown voltage. The probability of breakdown
against voltage has a normal (Gaussian) distribution. The standard
deviation of this distribution varies with the wave shape, gap
geometry, and atmospheric conditions. The withstand voltage of the
air gap is three standard deviations (3[sigma]) below the critical
sparkover voltage. (The critical sparkover voltage is the crest
value of the impulse wave that, under specified conditions, causes
sparkover 50 percent of the time. An impulse wave of three standard
deviations below this value, that is, the withstand voltage, has a
probability of sparkover of approximately 1 in 1,000.)
    5. Broken Insulators. Tests show reductions in the insulation
strength of insulator strings with broken skirts. Broken units may
lose up to 70 percent of their withstand capacity. Because an
employer cannot determine the insulating capability of a broken unit
without testing it, the employer must consider damaged units in an
insulator to have no insulating value. Additionally, the presence of
a live-line tool alongside an insulator string with broken units may
further reduce the overall insulating strength. The number of good
units that must be present in a string for it to be ``insulated'' as
defined by Sec.  1910.269(x) depends on the maximum overvoltage
possible at the worksite.

B. Minimum Approach Distances Based on Known, Maximum-Anticipated
Per-Unit Transient Overvoltages

    1. Determining the minimum approach distance for AC systems.
Under Sec.  1910.269(l)(3)(ii), the employer must determine the
maximum anticipated per-unit transient overvoltage, phase-to-ground,
through an engineering analysis or must assume a maximum anticipated
per-unit transient overvoltage, phase-to-ground, in accordance with
Table R-9. When the employer conducts an engineering analysis of the
system and determines that the maximum transient overvoltage is
lower than specified by Table R-9, the employer must ensure that any
conditions assumed in the analysis, for example, that employees
block reclosing on a circuit or install portable protective gaps,
are present during energized work. To ensure that these conditions
are present, the employer may need to institute new live-work
procedures reflecting the conditions and limitations set by the
engineering analysis.
    2. Calculation of reduced approach distance values. An employer
may take the following steps to reduce minimum approach distances
when the maximum transient overvoltage on the system (that is, the
maximum transient overvoltage without additional steps to control
overvoltages) produces unacceptably large minimum approach
distances:
    Step 1. Determine the maximum voltage (with respect to a given
nominal voltage range) for the energized part.
    Step 2. Determine the technique to use to control the maximum
transient overvoltage. (See paragraphs IV.C and IV.D of this
appendix.) Determine the maximum transient overvoltage that can
exist at the worksite with that form of control in place and with a
confidence level of 3[sigma]. This voltage is the withstand voltage
for the purpose of calculating the appropriate minimum approach
distance.
    Step 3. Direct employees to implement procedures to ensure that
the control technique is in effect during the course of the work.
    Step 4. Using the new value of transient overvoltage in per
unit, calculate the required minimum approach distance from Table R-
3.

C. Methods of Controlling Possible Transient Overvoltage Stress
Found on a System

    1. Introduction. There are several means of controlling
overvoltages that occur on transmission systems. For example, the
employer can modify the operation of circuit breakers or other
switching devices to reduce switching transient overvoltages.
Alternatively, the employer can hold the overvoltage to an
acceptable level by installing surge arresters or portable

protective gaps on the system. In addition, the employer can change
the transmission system to minimize the effect of switching
operations. Section 4.8 of IEEE Std 516-2009 describes various ways
of controlling, and thereby reducing, maximum transient
overvoltages.
    2. Operation of circuit breakers. \7\ The maximum transient
overvoltage that can reach the worksite is often the result of
switching on the line on which employees are working. Disabling
automatic reclosing during energized line work, so that the line
will not be reenergized after being opened for any reason, limits
the maximum switching surge overvoltage to the larger of the opening
surge or the greatest possible fault-generated surge, provided that
the devices (for example, insertion resistors) are operable and will
function to limit the transient overvoltage and that circuit breaker
restrikes do not occur. The employer must ensure the proper
functioning of insertion resistors and other overvoltage-limiting
devices when the employer's engineering analysis assumes their
proper operation to limit the overvoltage level. If the employer
cannot disable the reclosing feature (because of system operating
conditions), other methods of controlling the switching surge level
may be necessary.
---------------------------------------------------------------------------

    \7\ The detailed design of a circuit interrupter, such as the
design of the contacts, resistor insertion, and breaker timing
control, are beyond the scope of this appendix. The design of the
system generally accounts for these features. This appendix only
discusses features that can limit the maximum switching transient
overvoltage on a system.
---------------------------------------------------------------------------

    Transient surges on an adjacent line, particularly for double
circuit construction, may cause a significant overvoltage on the
line on which employees are working. The employer's engineering
analysis must account for coupling to adjacent lines.
    3. Surge arresters. The use of modern surge arresters allows a
reduction in the basic impulse-insulation levels of much
transmission system equipment. The primary function of early
arresters was to protect the system insulation from the effects of
lightning. Modern arresters not only dissipate lightning-caused
transients, but may also control many other system transients caused
by switching or faults.
    The employer may use properly designed arresters to control
transient overvoltages along a transmission line and thereby reduce
the requisite length of the insulator string and possibly the
maximum transient overvoltage on the line.\8\
---------------------------------------------------------------------------

    \8\ Surge arrester application is beyond the scope of this
appendix. However, if the employer installs the arrester near the
work site, the application would be similar to the protective gaps
discussed in paragraph IV.D of this appendix.
---------------------------------------------------------------------------

    4. Switching Restrictions. Another form of overvoltage control
involves establishing switching restrictions, whereby the employer
prohibits the operation of circuit breakers until certain system
conditions are present. The employer restricts switching by using a
tagging system, similar to that used for a permit, except that the
common term used for this activity is a ``hold-off'' or
``restriction.'' These terms indicate that the restriction does not
prevent operation, but only modifies the operation during the live-
work activity.

D. Minimum Approach Distance Based on Control of Maximum Transient
Overvoltage at the Worksite

    When the employer institutes control of maximum transient
overvoltage at the worksite by installing portable protective gaps,
the employer may calculate the minimum approach distance as follows:
    Step 1. Select the appropriate withstand voltage for the
protective gap based on system requirements and an acceptable
probability of gap sparkover.\9\
---------------------------------------------------------------------------

    \9\ The employer should check the withstand voltage to ensure
that it results in a probability of gap flashover that is acceptable
from a system outage perspective. (In other words, a gap sparkover
will produce a system outage. The employer should determine whether
such an outage will impact overall system performance to an
acceptable degree.) In general, the withstand voltage should be at
least 1.25 times the maximum crest operating voltage.
---------------------------------------------------------------------------

    Step 2. Determine a gap distance that provides a withstand
voltage \10\ greater than or equal to the one selected in the first
step.\11\
---------------------------------------------------------------------------

    \10\ The manufacturer of the gap provides, based on test data,
the critical sparkover voltage for each gap spacing (for example, a
critical sparkover voltage of 665 kilovolts for a gap spacing of 1.2
meters). The withstand voltage for the gap is equal to 85 percent of
its critical sparkover voltage.
    \11\ Switch steps 1 and 2 if the length of the protective gap is
known.
---------------------------------------------------------------------------

    Step 3. Use 110 percent of the gap's critical sparkover voltage
to determine the phase-to-ground peak voltage at gap sparkover (VPPG
Peak).
    Step 4. Determine the maximum transient overvoltage, phase-to-
ground, at the worksite from the following formula:
[GRAPHIC] [TIFF OMITTED] TR11AP14.025

    Step 5. Use this value of T \12\ in the equation in Table R-3 to
obtain the minimum approach distance. If the worksite is no more
than 900 meters (3,000 feet) above sea level, the employer may use
this value of T to determine the minimum approach distance from
Table 7 through Table 14.
---------------------------------------------------------------------------

    \12\ IEEE Std 516-2009 states that most employers add 0.2 to the
calculated value of T as an additional safety factor.

    Note: All rounding must be to the next higher value (that is,
---------------------------------------------------------------------------
always round up).

    Sample protective gap calculations.
    Problem: Employees are to perform work on a 500-kilovolt
transmission line at sea level that is subject to transient
overvoltages of 2.4 p.u. The maximum operating voltage of the line
is 550 kilovolts. Determine the length of the protective gap that
will provide the minimum practical safe approach distance. Also,
determine what that minimum approach distance is.
    Step 1. Calculate the smallest practical maximum transient
overvoltage (1.25 times the crest phase-to-ground voltage): \13\
---------------------------------------------------------------------------

    \13\ To eliminate sparkovers due to minor system disturbances,
the employer should use a withstand voltage no lower than 1.25 p.u.
Note that this is a practical, or operational, consideration only.
It may be feasible for the employer to use lower values of withstand
voltage.
[GRAPHIC] [TIFF OMITTED] TR11AP14.026

    This value equals the withstand voltage of the protective gap.
    Step 2. Using test data for a particular protective gap, select
a gap that has a critical sparkover voltage greater than or equal
to:

561kV / 0.85 = 660kV

For example, if a protective gap with a 1.22-m (4.0-foot) spacing
tested to a critical sparkover voltage of 665 kilovolts (crest),
select this gap spacing.
    Step 3. The phase-to-ground peak voltage at gap sparkover (VPPG
Peak) is 110 percent of the value from the previous step:

665kV x 1.10 = 732kV

This value corresponds to the withstand voltage of the electrical
component of the minimum approach distance.
    Step 4. Use this voltage to determine the worksite value of T:
    [GRAPHIC] [TIFF OMITTED] TR11AP14.027

    Step 5. Use this value of T in the equation in Table R-3 to
obtain the minimum approach distance, or look up the minimum
approach distance in Table 7 through Table 14:

MAD = 2.29m (7.6 ft).

E. Location of Protective Gaps

    1. Adjacent structures. The employer may install the protective
gap on a structure adjacent to the worksite, as this practice does
not significantly reduce the protection afforded by the gap.
    2. Terminal stations. Gaps installed at terminal stations of
lines or circuits provide a level of protection; however, that level
of protection may not extend throughout the length of the line to
the worksite. The use of substation terminal gaps raises the
possibility that separate surges could enter the line at opposite
ends, each with low enough magnitude to pass the terminal gaps
without sparkover. When voltage surges occur simultaneously at each
end of a line and travel toward each other, the total voltage on the
line at the point where they meet is the arithmetic sum of the two
surges. A gap installed within 0.8 km (0.5 mile) of the worksite
will protect against such intersecting waves. Engineering studies of
a particular line or system may indicate that employers can
adequately protect employees by installing gaps at even more distant
locations. In any event, unless using the default values for T from
Table R-9, the employer must determine T at the worksite.
    3. Worksite. If the employer installs protective gaps at the
worksite, the gap setting establishes the worksite impulse
insulation strength. Lightning strikes as far as 6 miles from the
worksite can cause a voltage surge greater than the gap withstand
voltage, and a gap sparkover can occur. In addition, the gap can
sparkover from overvoltages on the line that exceed the withstand
voltage of the gap. Consequently, the employer must protect
employees from hazards resulting from any sparkover that could
occur.

    F. Disabling automatic reclosing. There are two reasons to
disable the automatic-reclosing feature of circuit-interrupting
devices while employees are performing live-line work:
     To prevent reenergization of a circuit faulted during
the work, which could create a hazard or result in more serious
injuries or damage than the injuries or damage produced by the
original fault;
     To prevent any transient overvoltage caused by the
switching surge that would result if the circuit were reenergized.

However, due to system stability considerations, it may not always
be feasible to disable the automatic-reclosing feature.

V. Minimum Approach-Distance Tables

    A. Legacy tables. Employers may use the minimum approach
distances in Table 6 through Table 13 until March 31, 2015.

                            Table 6--Minimum Approach Distances Until March 31, 2015
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
       Voltage range phase to phase  (kV)       ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
0.05 to 1.0....................................           Avoid Contact
                                                          Avoid Contact
                                                ----------------------------------------------------------------
1.1 to 15.0....................................            2.10            0.64             2.20            0.66
15.1 to 36.0...................................            2.30            0.72             2.60            0.77
36.1 to 46.0...................................            2.60            0.77             2.80            0.85
46.1 to 72.5...................................            3.00            0.90             3.50            1.05
72.6 to 121....................................            3.20            0.95             4.30            1.29
138 to 145.....................................            3.60            1.09             4.90            1.50
161 to 169.....................................            4.00            1.22             5.70            1.71
230 to 242.....................................            5.30            1.59             7.50            2.27
345 to 362.....................................            8.50            2.59            12.50            3.80
500 to 550.....................................           11.30            3.42            18.10            5.50
765 to 800.....................................           14.90            4.53            26.00            7.91
----------------------------------------------------------------------------------------------------------------
Note: The clear live-line tool distance must equal or exceed the values for the indicated voltage ranges.

       Table 7--Minimum Approach Distances Until March 31, 2015--72.6 to 121.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
2.0............................................            0.74            2.42             1.09            3.58
2.1............................................            0.76            2.50             1.09            3.58
2.2............................................            0.79            2.58             1.12            3.67
2.3............................................            0.81            2.67             1.14            3.75
2.4............................................            0.84            2.75             1.17            3.83
2.5............................................            0.84            2.75             1.19            3.92
2.6............................................            0.86            2.83             1.22            4.00
2.7............................................            0.89            2.92             1.24            4.08
2.8............................................            0.91            3.00             1.24            4.08
2.9............................................            0.94            3.08             1.27            4.17
3.0............................................            0.97            3.17             1.30            4.25
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

       Table 8--Minimum Approach Distances Until March 31, 2015--121.1 to 145.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
2.0............................................            0.84            2.75             1.24            4.08
2.1............................................            0.86            2.83             1.27            4.17
2.2............................................            0.89            2.92             1.30            4.25
2.3............................................            0.91            3.00             1.32            4.33
2.4............................................            0.94            3.08             1.35            4.42
2.5............................................            0.97            3.17             1.37            4.50
2.6............................................            0.99            3.25             1.40            4.58
2.7............................................            1.02            3.33             1.42            4.67
2.8............................................            1.04            3.42             1.45            4.75
2.9............................................            1.07            3.50             1.47            4.83
3.0............................................            1.09            3.58             1.50            4.92
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

       Table 9--Minimum Approach Distances Until March 31, 2015--145.1 to 169.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
2.0............................................            0.91            3.00             1.42            4.67
2.1............................................            0.97            3.17             1.45            4.75
2.2............................................            0.99            3.25             1.47            4.83
2.3............................................            1.02            3.33             1.50            4.92
2.4............................................            1.04            3.42             1.52            5.00
2.5............................................            1.07            3.50             1.57            5.17
2.6............................................            1.12            3.67             1.60            5.25
2.7............................................            1.14            3.75             1.63            5.33
2.8............................................            1.17            3.83             1.65            5.42
2.9............................................            1.19            3.92             1.68            5.50
3.0............................................            1.22            4.00             1.73            5.67
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

      Table 10--Minimum Approach Distances Until March 31, 2015--169.1 to 242.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
2.0............................................            1.17            3.83             1.85            6.08
2.1............................................            1.22            4.00             1.91            6.25
2.2............................................            1.24            4.08             1.93            6.33
2.3............................................            1.30            4.25             1.98            6.50
2.4............................................            1.35            4.42             2.01            6.58
2.5............................................            1.37            4.50             2.06            6.75
2.6............................................            1.42            4.67             2.11            6.92
2.7............................................            1.47            4.83             2.13            7.00
2.8............................................            1.50            4.92             2.18            7.17
2.9............................................            1.55            5.08             2.24            7.33
3.0............................................            1.60            5.25             2.29            7.50
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

      Table 11--Minimum Approach Distances Until March 31, 2015--242.1 to 362.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
2.0............................................            1.60            5.25             2.62            8.58
2.1............................................            1.65            5.42             2.69            8.83
2.2............................................            1.75            5.75             2.79            9.17
2.3............................................            1.85            6.08             2.90            9.50
2.4............................................            1.93            6.33             3.02            9.92
2.5............................................            2.03            6.67             3.15           10.33
2.6............................................            2.16            7.08             3.28           10.75
2.7............................................            2.26            7.42             3.40           11.17
2.8............................................            2.36            7.75             3.53           11.58
2.9............................................            2.49            8.17             3.68           12.08
3.0............................................            2.59            8.50             3.81           12.50
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

      Table 12--Minimum Approach Distances Until March 31, 2015--362.1 to 552.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
1.5............................................            1.83            6.00             2.24            7.33
1.6............................................            1.98            6.50             2.67            8.75
1.7............................................            2.13            7.00             3.10           10.17
1.8............................................            2.31            7.58             3.53           11.58
1.9............................................            2.46            8.08             4.01           13.17
2.0............................................            2.67            8.75             4.52           14.83

2.1............................................            2.84            9.33             4.75           15.58
2.2............................................            3.02            9.92             4.98           16.33
2.3............................................            3.20           10.50             5.23           17.17
2.4............................................            3.43           11.25             5.51           18.08
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

      Table 13--Minimum Approach Distances Until March 31, 2015--552.1 to 800.0 kV With Overvoltage Factor
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------

1.5............................................            2.95            9.67             3.68           12.08
1.6............................................            3.25           10.67             4.42           14.50
1.7............................................            3.56           11.67             5.23           17.17
1.8............................................            3.86           12.67             6.07           19.92
1.9............................................            4.19           13.75             6.99           22.92
2.0............................................            4.55           14.92             7.92           26.00
----------------------------------------------------------------------------------------------------------------
Note 1: The employer may apply the distance specified in this table only where the employer determines the
  maximum anticipated per-unit transient overvoltage by engineering analysis. (Table 6 applies otherwise.)
Note 2: The distances specified in this table are the air, bare-hand, and live-line tool distances.

    B. Alternative minimum approach distances. Employers may use the
minimum approach distances in Table 14 through Table 21 provided
that the employer follows the notes to those tables.

                            Table 14--AC Minimum Approach Distances--72.6 to 121.0 kV
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
1.5............................................            0.67             2.2             0.84             2.8
1.6............................................            0.69             2.3             0.87             2.9
1.7............................................            0.71             2.3             0.90             3.0
1.8............................................            0.74             2.4             0.93             3.1
1.9............................................            0.76             2.5             0.96             3.1
2.0............................................            0.78             2.6             0.99             3.2
2.1............................................            0.81             2.7             1.01             3.3
2.2............................................            0.83             2.7             1.04             3.4
2.3............................................            0.85             2.8             1.07             3.5
2.4............................................            0.88             2.9             1.10             3.6
2.5............................................            0.90             3.0             1.13             3.7
2.6............................................            0.92             3.0             1.16             3.8
2.7............................................            0.95             3.1             1.19             3.9
2.8............................................            0.97             3.2             1.22             4.0
2.9............................................            0.99             3.2             1.24             4.1
3.0............................................            1.02             3.3             1.27             4.2
3.1............................................            1.04             3.4             1.30             4.3
3.2............................................            1.06             3.5             1.33             4.4
3.3............................................            1.09             3.6             1.36             4.5
3.4............................................            1.11             3.6             1.39             4.6
3.5............................................            1.13             3.7             1.42             4.7
----------------------------------------------------------------------------------------------------------------

                           Table 15--AC Minimum Approach Distances--121.1 to 145.0 kV
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
1.5............................................            0.74             2.4             0.95             3.1
1.6............................................            0.76             2.5             0.98             3.2
1.7............................................            0.79             2.6             1.02             3.3

1.8............................................            0.82             2.7             1.05             3.4
1.9............................................            0.85             2.8             1.08             3.5
2.0............................................            0.88             2.9             1.12             3.7
2.1............................................            0.90             3.0             1.15             3.8
2.2............................................            0.93             3.1             1.19             3.9
2.3............................................            0.96             3.1             1.22             4.0
2.4............................................            0.99             3.2             1.26             4.1
2.5............................................            1.02             3.3             1.29             4.2
2.6............................................            1.04             3.4             1.33             4.4
2.7............................................            1.07             3.5             1.36             4.5
2.8............................................            1.10             3.6             1.39             4.6
2.9............................................            1.13             3.7             1.43             4.7
3.0............................................            1.16             3.8             1.46             4.8
3.1............................................            1.19             3.9             1.50             4.9
3.2............................................            1.21             4.0             1.53             5.0
3.3............................................            1.24             4.1             1.57             5.2
3.4............................................            1.27             4.2             1.60             5.2
3.5............................................            1.30             4.3             1.64             5.4
----------------------------------------------------------------------------------------------------------------

                           Table 16--AC Minimum Approach Distances--145.1 to 169.0 kV
----------------------------------------------------------------------------------------------------------------
                                                     Phase-to-ground exposure         Phase-to-phase exposure
                    T (p.u.)                    ----------------------------------------------------------------
                                                        m               ft               m              ft
----------------------------------------------------------------------------------------------------------------
1.5............................................            0.81             2.7             1.05             3.4
1.6............................................            0.84             2.8             1.09             3.6
1.7............................................            0.87             2.9             1.13             3.7
1.8............................................            0.90             3.0             1.17             3.8
1.9............................................            0.94             3.1             1.21             4.0
2.0............................................            0.97             3.2             1.25             4.1
2.1............................................            1.00             3.3             1.29             4.2