Fault direction method in compensated network using the zero sequence active energy signal

In medium voltage distribution network, a coil might be placed in the transformer neutral to compensate the zero sequence capacitance of the network. This creates a zero sequence system with very high impedance fault. In case of single phase earth fault, the consequence is a very small faulty current which allows continuous operation even in faulty condition. Several protection devices exist to indicate the fault direction using the transient signal. A new method has been developed by computation of the zero sequence active energy signal to increase the sensitivity of the device regarding the fault impedance. The energy comes from the charging of the zero sequence capacitance of the sound feeder and the imperfection of the Petersen coil. This paper describes the phenomenon behind the algorithm of direction determination and followed by the explanation of the algorithm with simulation tests and recordings from a German DSO.