Influence of distributed generation on the protection principles of a 70 kV/15 kV transformer in antenna: The zero-sequence overvoltage protection U0>

Distributed Generation (DG) influences the traditional protection schemes. In this paper the influence of DG on the protections of the Belgian grid operator, Elia, is explained for a 70 kV/15 kV transformer in antenna. Based on the method of the symmetrical components, the detection of two different types of protections, zero-sequence overvoltage, U0>, and negative-sequence overvoltage, U2>, are analysed in case of a line-to-ground fault, a broken conductor without earth fault and a broken conductor with earth fault at the transformer side. The U0>relay is to be installed in the star point at the primary side of the transformer and measures the zero-sequence voltage. The U2>relay calculates the negative-sequence voltage at the secondary side of the transformer.