Earth fault detector in power line section - disconnects line section for very short period and observes delay of unbalance voltage

摘要

The line section is a part of a three-phase network (10) with earthed or non-earthed neutral. Detection of the earthed section is achieved by brief disconnection of line sections after appearance of unbalance voltage signalling an earth fault. The part of the network affected by earth fault is detected by a network disconnection without interfering with a consumer. Line sections in this network part are disconnected during certain time intervals, with the voltage at certain points disconnected for a period of the order of 250 milliseconds. Decay of the envelope of the unbalance voltage appearing after the disconnection serves as criterion for the section affected by the earth fault.