Electro-Voice 1252, 250 operation manual Power Quality, Cause Disturbance Type Source

1.5: Power Quality

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 mis-operation 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 Table 1.3 below.

Cause	Disturbance Type	Source
	Transient voltage disturbance,	Lightning
Impulse Transient		Electrostatic discharge
	sub-cycle duration	Load switching
		Capacitor switching
Oscillatory transient	Transient voltage, sub-cycle	Line/cable switching
		Capacitor switching
with decay	duration
		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 distortion	Steady state current or voltage,	Non-linear loads
	long term duration	System resonance

Table 1.3: Typical Power Quality Problems and Sources

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.

Electro Industries/GaugeTech Doc # E107706 V1.25 1-13