Earth-fault detection in a compensated earthed network, without any voltage measurement: a new protection principle

In a compensated earthed network, the detection of phase-to-earth faults is currently achieved by a directional earth-fault protection. Such a protection can be based either on the residual active current or on the residual active power, but it always requires the residual voltage to be measured. An artificial neural network (ANN) can be used for an alternative approach. When adequately designed and trained an ANN based algorithm is able to recognise different network conditions and thus it can make a correct fault diagnosis. This powerful concept has already been used in order to improve the performances of a distance protection, for instance in Coury et al. (1998) or to reduce the number of settings of a transformer differential protection, in Bertrand et al. (1997). In the application described in this paper, the ANN is used in order to reduce the number of the relay inputs. An algorithm has been developed, which detects phase-to-ground faults in a Petersen-coil earthed network, without any voltage measurement; only the three phase currents are processed.