GE EPM 6000 Multi-function Power Metering System Typical Power Quality Problems

CHAPTER 2: ELECTRICAL BACKGROUND

2.6Power Quality

2.6.1 Description

Power quality can mean several different things. The terms power quality and power quality problem have been applied to all types of conditions. A simple definition of power quality problem is any voltage, current or frequency deviation that results in misoperation or failure of customer equipment or systems. The causes of power quality problems vary widely and may originate in the customer equipment, in an adjacent customer facility or with the utility.

In his book Power Quality Primer, Barry Kennedy provided information on different types of power quality problems. Some of that information is summarized in the following table.

Table 2–3: Typical Power Quality Problems

Cause	Disturbance Type	Source(s)
		Lightning;
Impulse	Transient voltage disturbance,	Electrostatic discharge;
transient	sub-cycle duration	Load switching;
		Capacitor switching
Oscillatory	Transient voltage, sub-cycle	Line/cable switching;
transient with		Capacitor switching;
	duration
decay		Load switching
Sag/swell	RMS voltage, multiple cycle	Remote system faults
	duration
		System protection;
Interruptions	RMS voltage, multiple second or	Circuit breakers;
	longer duration	Fuses;
		Maintenance
Undervoltage/	RMS voltage, steady state,	Motor starting;
	multiple second or longer	Load variations;
Overvoltage
	duration	Load dropping
	RMS voltage, steady state,	Intermittent loads;
Voltage flicker		Motor starting;
	repetitive condition
		Arc furnaces
Harmonic	Steady-state current or voltage,	Non-linear loads;
distortion	long term duration	System resonance

It is often assumed that power quality problems originate with the utility. While it is true that may power quality problems can originate with the utility system, many problems originate with customer equipment. Customer-caused problems may manifest themselves inside the customer location or they may be transported by the utility system to another adjacent customer. Often, equipment that is sensitive to power quality problems may in fact also be the cause of the problem.

If a power quality problem is suspected, it is generally wise to consult a power quality professional for assistance in defining the cause and possible solutions to the problem.

EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 2–17