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+64 3 348 5999 (Int)
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Severe Power Quality Event… Burned Fuse Cut-out Determined & Located

Event from week commencing April 4th 2016 – USA. This event involved a long circuit with many miles of overhead exposure. A school and other customers at various locations on the circuit began complaining of flickering lights. The utility patrolled but was unsuccessful. They were considering running an infrared scan of the circuit, but this would be difficult because some portions of the circuit were not truck accessible. The flicker condition was severe and continued for six days. Early in the process DFA detected a failing switch on the circuit and estimated that the switch had 83 kVA of load past it, +/- 50%. The utility company became desperate enough that they were willing to switch off sections of the circuit, one at a time, to see when the flicker went away. Unfortunately they did not have any system, other than DFA, that would tell them when the problem went away. Power Solutions Inc, the makers of and prime technical support team for the DFA, worked with them for four hours at that time during which time they opened and closed multiple switches. At each switching operation, DFA real-time measurements made it obvious whether the problem was downstream of the just-operated switch. This is possible because DFA and PSI is aware which parameter to monitor as an indication of switch failure. Neither SCADA nor anything else available to the customer utility would provide this parameter or enable this real-time feedback to guide their search. In addition, dispatchers asked PSI "could it be tree contact?" and "could it be a failing arrester?" and many such questions. The clear answer, based on DFA, was that it was not any of these things but rather a failing switch or clamp, with greatest likelihood of switch. This enabled the utility to know what to look for. When they finally identified the problem, it was indeed a burned top of a fused cut-out serving a single heavily-loaded 50 kVA service transformer. The DFA-assisted search took four hours. A search without DFA would likely have taken days, during which time the utility would have expended many more man-hours and would have continued to provide degraded service to their customers.

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