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+64 3 348 5999 (Int)
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Catastrophic Surge Arrestor Failure Detected and Located

Event from week commencing March 28th 2016: USA. A substation circuit breaker tripped once and reclosed successfully, during a storm. SCADA told the utility this, but told them nothing more. This was a routine fault that ordinarily would not be investigated. From DFA, however, it was clear that the fault resulted from the catastrophic failure of an MOV-type arrester. When these fail, the body of the arrester may blow apart physically. In such scenarios it might be that part of the arrester body remains connected to an energized phase conductor and dangles in the air, another common scenario being that the arrestor blows apart and can eject hot porcelain and internal material posing a fire and safety risk in either case. Based upon knowing from DFA that this was an arrester failure, the utility investigated and indeed found the failed arrester which had suffered that latter failure mode on this occasion. In addition, DFA supplied a fault current level, which the utility put the DFA-generated fault current into their single line model to narrow the search to a small area. (A relay might have given them a fault current level, too, but this point is moot if they do not have a compelling reason to investigate the event.) Therefore the crew was dispatched knowing (1) where to look and (2) what to look for. If the utility had not investigated, it is impossible to have known either how long the fractured arrester body may have remained in the broken, dangling condition and a continued possible safety, bushfire, and customer service delivery/reliability risk, or, in the second and actual scenario in this case, whether there had been a fire start or injury to a passing person as a result. The prompt location was valuable in either scenario.

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