Omaha Public Power District, Omaha, Nebraska, U.S., recently engaged EPRIsolutions to help it determine whether the vintage externally gapped lightning arresters on its distribution system were operating within design limits. But the lightning impulse tests that EPRIsolutions conducted at the Arrester Test Facility in Lenox, Massachusetts, U.S., produced some interesting results.

“We have always assumed that if the lightning arresters were intact, the transformer and line were protected,” said Bill Dahl, PE, OPPD’s Technical Services Engineer. “However, the testing and analysis that EPRIsolutions performed on a sample of our older externally-gapped distribution arresters proved that this may not be the case. Based on EPRIsolutions’ findings, we are developing a plan to replace all arresters that are 40 years old or older.”

According to Dave Rueger, the EPRIsolutions project manager, the tests were, first and foremost, designed to help the utility assess the functionality of similar arresters in service on its distribution system. “In a larger sense,” he said, “the tests will also help OPPD improve distribution transformer protection levels, reduce breaker operations, and increase power quality.” Rueger also noted that the test results identified which types of vintage arresters should be replaced first, allowing OPPD engineers to optimize their replacement strategy.

But for Rueger, there were additional benefits. “It’s not often that you get a chance to put vintage electrical components to the test and compare the results to modern technology,” he adds.