Breakdown Behaviour of Damaged Low-Voltage Cables: Laboratory Experiments and Field Experience
Faults in Low-Voltage (LV) cables commonly develop from earlier inflicted damage. Outages can be preceded by high-current transients of duration too short to activate protective devices like fuses. This paper explores such early signatures of possible upcoming faults both by laboratory experiments and in a field study.
Upon exposure of moisture the breakdowns and their voltage and current characteristics are investigated for two LV cable types (OIP and PVC). In laboratory tests, a clear intermittent behaviour is observed. Typical breakdown signals show a current transient igniting around the voltage peak and its extinction is usually close to the voltage zero crossing. LV grid faults should be distinguished from events occurring in connected households. Though signal patterns can be comparable, a distinction can usually be made, mainly based on current peak values because of the interruption characteristics of household miniature circuit breakers. A pilot study involving 23 connections in the LV grid has shown similar signals as obtained in the laboratory tests. Typical cable fault related transients were observed beforehand. This indicates a correlation of such transients and the likelihood of an outage. A large variation of the time to an outage was observed ranging from several hours to several months.
Copyright (c) 2017 B. Kruizinga, P.A.A.F. Wouters, E.F. Steennis
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