A friend reminded me of the extensive flicker monitoring program
that the Colombian utility commission required of electric
utilities beginning in 2005. Based on preliminary measurements,
it was obvious that the perceptibility short term (Pst) value
used to quantify the complex process of the eye-brain response
to voltage fluctuations below 30 hertz was greater than the
typically accepted annoyance level of 1.0 in many measurements,
as shown in the figure below. Yet the number of complaints about
the lights flickering wasn’t that large.  Likewise, studies in
Australia and elsewhere have found the magic 1.0 number has been
exceeded with minimal complaints. An October 2011 U.K. study
found that the “shadow flicker” effect (modulation of the
voltage waveform as a blade of a wind turbine passes in line
with the tower) that was a big concern with increased deployment
of wind turbines has been insignificant there. Does this mean
that, after years of effort to develop and adopt standards for
accurately measuring fli