Resonant Grounded Isolation Transformers to Prevent Ignitions From Powerline Faults

Abstract

Methods and research for preventing utility-caused wildfires have significantly advanced in the past few decades, including development of criteria on reduction of energy release in an electrical fault to mitigate the probability of ignitions. Technologies to minimize energy release during electrical faults and achieve these ignition benefits are being applied at the substation level. However, the benefits can be targeted to a high-risk area by resonant grounding an isolation transformer on a distribution circuit. By doing this it is possible to reduce single line to ground fault current beyond the transformer to a level unlikely to ignite fires. This system was constructed and shown capable of reducing the power into a phase-to-ground fault by a factor of more than 10,000 and detect ground faults smaller than 0.5 A. This allowed it to meet the ignition criteria mandated for distribution network fire safety in the Australian state of Victoria. It was also tested for typical ignition scenarios such as downed phase conductors and phase conductors contacting with a tree branch. In all cases the probability of ignition was reduced by 90% or more.