Power Quality; Description - GE Multilin EPM 6000 Instruction Manual

CHAPTER 2: ELECTRICAL BACKGROUND
2.6

Power Quality

2.6.1

Description

EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
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
Impulse Transient voltage disturbance,
transient sub-cycle duration
Oscillatory
Transient voltage, sub-cycle
transient with
duration
decay
RMS voltage, multiple cycle
Sag/swell
duration
RMS voltage, multiple second or
Interruptions
longer duration
RMS voltage, steady state,
Undervoltage/
multiple second or longer
Overvoltage
duration
RMS voltage, steady state,
Voltage flicker
repetitive condition
Harmonic Steady-state current or voltage,
distortion long term duration
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.
Disturbance Type Source(s)
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
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