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Testing Arresters Before Lightning Does

Rural Electrification Magazine, August 1992

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."

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