however, a customer-driven issue. It could be said that any power problem concerning
voltage or current that results in a failure or misoperation of customer equipment is a
power quality problem.
Harmonic distortion in a power system is caused by nonlinear devices. Electronic power
converter loads constitute the most important class of nonlinear loads in a power system.
The switch mode power supplies in a number of single-phase electronic equipment, such
as personal computers, printers and copiers, have a very high third-harmonic content in
the current. Three-phase electronic power converters, that is, dc/ac drives, however, do
not generate third-harmonic currents. Still, they can be significant sources of harmonics.
Power quality monitoring is an essential service that utilities can provide for their
industrial and key customers. Not only can a monitoring system provide information
about system disturbances and their possible causes, it can also detect problem conditions
throughout the system before they cause customer complaints, equipment malfunctions
and even equipment damage or failure. Power quality problems are not limited to the
utility side of the system. In fact, the majority of power quality problems are localized
within customer facilities. Thus, power quality monitoring is not only an effective
customer service strategy but also a way to protect a utility's reputation for quality power
and service.
PQI provides a method for monitoring the power quality by means of the current
waveform distortion. PQI provides a short-term 3-second average and a long-term
demand for TDD.
10.1.6 Signals
Table 915: PQI Input signals
Name
Type Default Description
I_A SIGNAL 0 Phase A current
I_B SIGNAL 0 Phase B current
I_C SIGNAL 0 Phase C current
BLOCK BOOLEAN 0=False Block signal for all binary outputs
Table 916: PQI Output signals
Name
Type Description
ALARM BOOLEAN Alarm signal for TDD
1MAC059074-MB A Section 10
Power quality measurement functions
615 series ANSI 1035
Technical Manual
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