Waveform analysis aficionados may
have noticed that the example in Figure
1 also has another power quality problem due to the harmonics: multiple zero
crossings. Fortunately, the harmonic
impedance was low enough that the
resulting voltage waveform did not have
the same scale of distortion around the
zero crossing as the current does. If it did,
equipment that uses the voltage waveform
to synchronize time and processing could
be seriously compromised without proper
filter protection in its circuitry.
Harmonics aren’t all bad. Anyone who
has sung in a choral group or played in
an orchestra knows that, without them,
music would be pretty boring. This is not
true with harmonics on electrical circuits,
where “boring” is good, as the power
quality of the electrical supply meets the
requirements of loads.
BI NGHA M, a contributing editor for power quality, can be reached at 732.248.4393.
Figure 2: Vthd from a facility in mixed commercial/residential area