Assessment of medium voltage earth fault protection for embedded generation

With the large influx of embedded generation into Western Power´s distribution network, the risk of the formation of stable `island´ networks following a single phase to earth fault on the medium voltage network has grown. Traditional methods for detecting and clearing these faults can be beyond the economic reach of small scale generators, especially household photovoltaic generators, therefore these customers must rely on the anti-islanding schemes described in AS4777. This paper will assess two common forms of passive anti-islanding schemes and express the network constraints as a `non-detection zone´ in terms of commonly measured network parameters This has allowed Western Power to proactively inform policies for the connection of new embedded generation to mitigate the identified risk, and which may be easily and effectively applied.