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Rural
Electrification Magazine, August 1992
Testing
Arresters Before Lightning Does
by
John Lowrey, Communications Manager for Southwest Arkansas Electric
Cooperative
Consumers
with complaints can cause headaches, but they can also mean opportunities
for creative problem solving. For Piedmont EMC in Hillsborough,
North Carolina, a consumer's blinking light complaint created
an opportunity to experiment with a new test meter for lightning
arresters. With a demonstration unit from Hi-Test Detection Instruments.
Piedmont found 25 bad arresters out of 40 on the line serving
the dissatisfied member.
David
Obenshain, manager of engineering for Piedmont, admits the 19,265-member
co-op's reclosers are operating more than he would like, causing
20 to 40 blinks per year for some members. "If you've got
a bad arrester of any type - say the silicon carbide material
crystallizes and the arrester no longer has decent characteristics
and doesn't clear a fault - then the recloser behind it has to
open and you get blinks all the way down the line," explains
Obenshain.
To
attack the blinks, Piedmont EMC has exchanged old lightning arresters,
installing new metal oxide varistor (MOV) arresters, installed
wildlife guards on transformers and used new electronic controls
on reclosers to fine-tune system protection. And now the co-op
can also test lightning arresters.
The
Hi-Test Surge Arrester Tester is the first low-cost device available
for testing distribution-class arresters. It can also be used
to test insulators. Transformer bushings and fuses. Weighing just
three pounds and powered by a 12-VDC gel cell, the tester puts
out 0 to 30 kVDC in 1-kV steps. Current leakage is displayed on
a 0 to 50-microamp LED display in 5-microamp steps. The tester
can be used for field testing and troubleshooting, for random
testing the quality assurance of new material, and for routine
testing in transformer shops.
"When
you put the test leads across any arrester. If there's any current
leakage, the current meter will indicate that current leakage
and the volt meter will instantly display the breakover voltage
of the part that you're testing." says John Farquhar, President
of Hi-Test Detection Instruments.
There
is no danger of catastrophic failure when using this tester. "...
maximum current is a little over 200 microamps. There's no way
its going to cause any kind of explosive failure," says Farquhar.
"We
tried it with new arresters and old arresters. We believe that
it works well on the old expulsion-type arrester, the more modern
silicon carbide arrester and also the modern MOV arrester."
Says Obenshain... "Ultimately system protection and coordination
is as much an art as a science. The right tools help." But
he quickly adds, "I also have a senior electrical engineer
who is really good at the art of system coordination."
Go
to the HiSat Arrester/Leakage Tester product page
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