problem concerning voltage or current that results in a failure or misoperation ofcustomer equipment is a power quality problem.Harmonic distortion in a power system is caused by nonlinear devices. Electronicpower converter loads constitute the most important class of nonlinear loads in apower system. The switch mode power supplies in a number of single-phaseelectronic equipment, such as personal computers, printers and copiers, have a veryhigh third-harmonic content in the current. Three-phase electronic powerconverters, 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 theirindustrial and key customers. Not only can a monitoring system provideinformation about system disturbances and their possible causes, it can also detectproblem conditions throughout the system before they cause customer complaints,equipment malfunctions and even equipment damage or failure. Power qualityproblems are not limited to the utility side of the system. In fact, the majority ofpower quality problems are localized within customer facilities. Thus, powerquality monitoring is not only an effective customer service strategy but also a wayto protect a utility's reputation for quality power and service.CMHAI provides a method for monitoring the power quality by means of thecurrent waveform distortion. CMHAI provides a short-term 3-second average and along-term demand for TDD.10.1.6 SignalsTable 643:CMHAI Input signalsName Type Default DescriptionI_A Signal 0 Phase A currentI_B Signal 0 Phase B currentI_C Signal 0 Phase C currentBLOCK BOOLEAN 0=False Block signal for all binary outputsTable 644:CMHAI Output signalsName Type DescriptionALARM BOOLEAN Alarm signal for TDD1YHT530004D05 D Section 10Power quality measurement functions615 series 767Technical Manual
