Application of novel multi-frequency neutral admittance method into earth-fault protection in compensated MV-networks

This paper describes a novel algorithm for feeder earth-fault protection applicable in compensated and unearthed medium-voltage networks. The suggested algorithm provides good protection sensitivity and very secure discrimination between faulty and healthy feeders even in the most challenging faults with highly distorted signals such as restriking earth faults. The operation of the novel method is based on multifrequency neutral admittance measurement in combination with cumulative phasor summing technique. In the paper, first the theory and operation of the novel algorithm is described. Secondly, the advantages and features brought by the novel method are demonstrated with variety of different fault types. The results show that the novel algorithm provides universal, all-in-one protection function that detects selectively all types of earth faults. Also the overall security and dependability of the existing protection schemes can be improved by the novel method, which can be applied either in tripping or alarming mode depending on the application.