Table of Contents
Advertisement
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 prob-
lems. Some of that information is summarized in Table 1.3, below.
Cause
Impulse Transient
Oscillatory transient with decay
Sag/swell
Interruptions
Undervoltage/
Overvoltage
Voltage flicker
Harmonic distortion
It is often assumed that power quality problems originate with the utility. While it is true that many 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.
e
Electro Industries/Gauge Tech
Disturbance Type
Transient voltage disturbance,
sub-cycle duration
Transient voltage, sub-cycle
duration
RMS voltage, multiple cycle
duration
RMS voltage, multipile second or
longer duration
RMS voltage, steady state, multiple
second or longer duration
RMS voltage, steady state,
repetitive condition
Steady state current or voltage,
long term duration
Table 1.3: Typical power quality problems and sources
Doc# E149701
Source
Lightning
Electrostatic discharge
Load switching
Capacitor switching
Line/cable switching
Capacitor switching
Load switching
Remote system faults
System protection
Circuit breakers
Fuses
Maintenance
Motor starting
Load variations
Load dropping
Intermittent loads
Motor starting
Arc furnaces
Non-linear loads
System resonance
1-13
Advertisement
Table of Contents
