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1MAC059074-MB A

615 series ANSI

Technical Manual

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.

Signals

PQI Input signals

PQI Output signals

Power quality measurement functions

Phase A current

Phase B current

Phase C current

Block signal for all binary outputs

Alarm signal for TDD

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