New single-ended earthfault distance estimation for the 110-kV- and 20-kV-compensated network

Due to today´s increased demands on grid operation management, new methods for earth fault localization and detection are needed. The fault localization should be performed as quickly as possible and under the condition, that the fault current at the fault location will not be significantly increased. The pros and cons of Distance Protection in solid grounded networks are well known. In case of a single-line earthfault, the current via the fault location in solid grounded networks is in the range of some kA. In compensated networks the residual current I_res via the fault location is, in case of a single line fault, only few ampere. Very often this current is much smaller than the load current of the feeder. A distinction between load current, circulating currents in meshed networks and fault current is more or less not possible. Therefore, the Earthfault-Distance-Protection in compensated networks is usually switched off. With the new transient relays, based on the qu2-algorithm, it is possible to detect in the substation very reliable the faulty feeder and the direction of the fault. This statement is also correct for meshed networks. In a 110-kV-network the distance between two substations is in the range of 50 km to 200 km. Also if the feeder is identified correctly, it is still a challenge to locate the exact fault position on this feeder. The results of field-test in a 110-kV-network with different fault impedances will be presented.