A traveling-wave-based line protection strategy against single-line-to-ground faults in active distribution networks

Abstract

Electricity networks are in the era of major transition from stable passive distribution networks with unidirectional electricity transportation to active distribution, and the fault on the distribution lines should be cleared from both sides accordingly. This paper proposes a traveling-wave-based line protection scheme which can isolate the Single-Line-to-Ground (SLG) fault from both sides of the faulted line in neutral non-effectively grounded distribution network including Distributed Generation (DG) sources. In the proposed scheme, when a SLG fault occurs, first, relays distinguish the fault direction by comparing the polarities of the initial voltage and current traveling waves; and then the relays that detect the fault on the downstream and upstream sides operate based on the conventional time grading coordination, and the electrical changes of three-phase in a specified time window, respectively; finally, after operation of the relay upstream of the fault on the faulted line with the fastest time setting, the relay downstream of the fault operates by detecting the tripping of the opposite circuit breaker. In order to validate the efficiency of the proposed scheme, extensive simulations have been performed on a typical active distribution system using ATP-EMTP software. The simulation results indicate that the proposed line protection scheme can accurately and quickly isolate the SLG fault from both sides.