Case Studies

4 Fluke Corporation Power Quality Case Study: Clean power delivers clean water
Fluke. Keeping your world
up and running
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Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
For more information call:
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ax (31 40) 2 675 222
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ax (9
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eb access: http://www.fluke.com
©2005 Fluke Corporation. All rights reserved.
Printed in U.S.A. 6/2005 2517353 A-EN-P Rev A
What is it?
Total Harmonic Distortion (THD) is the sum of the
contributions of all harmonics. Harmonic distor-
tion is a normal consequence of a power system
supplying electronic loads such as computers,
business machines, electronic lighting ballasts,
and control systems.
What does it do?
Harmonic distortion can cause:
•
High current to flow in neutral conductors.
•
Motors and transformers to run hot, shortening
their lives.
•
Increased susceptibility to voltage sags, poten-
tially causing spurious resets.
•
Reduced efficiency of transformer—or, a larger
unit is required to accommodate harmonics.
•
Audible noise.
How much does an incident cost?
The major costs are associated with shortened
life of motors and transformers. If the equipment
is part of production systems, income may be
affected as well.
Sample calculation
Assume the cost to replace a 100 KVA trans-
former is $7000 including labor each year.
Assume 8 hours of downtime each year with
inc
ome loss of $6
000 per hour.
Total Cost: $7000 + (8 x $6000) = $55,000
annually
What to check?
Motors, transformers and neutral conductors
ser
v
ing electronic loads.
How much is ok?
Voltage distortion (THD) should be investigated if
it is over 5 % on any phase. Some current distor-
tion (T
HD) is normal on any part of the system
serving electronic loads. Monitor current levels
and temperature at transformers to b
e sure that
they are not overstressed. Neutral current should
not exceed the capacity of the neutral conductor.
Why correct harmonics?
Maintenance Electrical Specialist Mark Newport using a Fluke 434
Power Quality Analyzer to measure, trend, and document the power
factor and harmonics correction provided by the plant’s new power
correction system.