Transformer maintenance consists mostly of testing, although it
includes other activities (e.g., housekeeping-related). The
three categories of transformer testing are:  1.    Acceptance.
Normally, you perform acceptance tests following initial
installation. The test results provide baseline maintenance
data. But if a transformer has not operated for a while, it
requires acceptance testing again. The normal definition of "a
while" is three days or more, but you might use a shorter
timeframe if conditions warrant (e.g., the sprinkler system
operated).  2.    Routine. These are data collection activities,
such as recording temperatures, and don’t require de-
energization.  3.    Periodic. The complete menu of these tests
requires a deep skill set, and thus they are typically
outsourced to a testing firm.  In the next several parts of this
series, we'll examine these further.