Application Note

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Application Note

F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w . f l u k e . c o m / l i b r a r y

Stepping up to

power quality tools

When electrical problems arise, every electrical profes-

sional knows to grab his digital multimeter and current

clamp and start looking for answers. Some problems

will be found and answered easily. But other issues

will go unanswered without the proper tools and

knowledge to investigate distribution systems contain-

ing electronic (nonlinear) loads. “Poor power quality”

is any deviation in the electrical supply to equipment

that results in its mis-operation or reduces its reliabil-

ity. Such deviations may occur for only milliseconds

or less, are often caused by nonlinear loads, and can

rarely be found with the digital multimeter.

How important are these power quality issues? Exact

dollar estimates vary, but these issues are known to

cost facilities billions of dollars annually. Neutrals and

transformers overheat, medical imaging equipment

locks up and requires a system reboot, employees

complain of headaches due to lighting conditions, and

a PBX loses calls—all of these typical power qual-

ity issues appear in single-phase systems. One utility

study of 112 different sites found power quality prob-

lems occurring from 114 problems per month in one

facility to over 4,000 problems per month in another

facility! It is clear that facility operations and mainte-

nance personnel, and contractors who are attempting

to help solve client needs, must be able to isolate and

solve the causes of power quality disturbances.

The first concept to understand when getting

started in power quality is that single-phase non-

linear loads, from computers to lighting to some

specialized equipment, will cause power quality

problems. These same nonlinear loads are also

susceptible to power quality problems. Fortu-

nately, the Fluke 43B Power Quality Analyzer is

specifically designed for testing and troubleshoot-

ing single-phase power problems. For those who

are looking for an introduction into the world of

power quality while taking the next step beyond

the digital multimeter, a single-phase power qual-

ity analyzer is the logical choice. Easy to set up

and use, the analyzer can give quick and precise

answers to allow for intelligent troubleshooting

decisions.

By Randy Barnett

Single-phase loads

While it is possible that poor quality power can

be delivered to a facility, estimates are that 65 to

85 percent of power quality problems are cre-

ated by equipment within the facility. Considering

that approximately 95 percent of the loads on

a 208Y/120 volt panel board in a modern com-

mercial facility are single-phase electronic loads

known to cause these problems, it is safe to

assume that troubleshooting these loads and their

branch circuits should be at least as important

to the electrical professional as taking standard

voltage and current readings with the digital

multimeter.

For those who want to break into the field of

power quality, the Fluke 43B Power Quality

Analyzer is a logical choice

Summary of content (4 pages)

PAGE 1
Stepping up to power quality tools For those who want to break into the field of power quality, the Fluke 43B Power Quality Analyzer is a logical choice Application Note By Randy Barnett When electrical problems arise, every electrical professional knows to grab his digital multimeter and current clamp and start looking for answers. Some problems will be found and answered easily.
PAGE 2
Take a general power survey Unless you already suspect the cause of the power quality problem, a good place to start is by performing a general power quality survey. Begin as far back toward the service entrance in the distribution system as possible. For example, most commercial buildings utilize a 208Y/120 volt distribution system. So, begin measurements at the first panel board downstream of the 208Y/120 volt transformers.
PAGE 3
The Volts/Amps/Hertz function Begin use of the Fluke 43B by depressing the Menu key and observing the instrument menu. Select the Volts/Amps/Hertz function and press Enter. Both voltage and current waveforms appear on the screen. A few quick checks here can determine whether you are at a location in the system that may be presenting some power quality concerns. Notice the severity of any distortion on the voltage and current sine waves. Look for a crest factor (CF) of 1.4 on the voltage sine wave.
PAGE 4
The Harmonics function Selecting Harmonics from the menu provides the level of each harmonic current in the system. Harmonic currents are multiples of the fundamental 60 Hz frequency. Different harmonic levels present different problems. In a single-phase system, the presence of the third harmonic is common. This harmonic current can cause overheating in neutral conductors and transformers and, as with all harmonics, it will tend to distort the fundamental sine wave.