First-zone distance relaying algorithm of parallel transmission lines for single-phase to ground faults

• In single phase to ground faults two zero-sequence currents of parallel lines is in-phase or reverse-phase.
• Two zero-sequence currents of parallel lines can be expressed as III0=kII0III0=kII0, k is a real member.
• It only requires current and voltage at one end of protected line to realize reliable distance relay of parallel lines.
• The problems of overreach and under-reach of zone-one distance relays can be overcome.
• The algorithm optimizes the performance of zone-one distance relaying for parallel lines.

A novel zone-one distance relaying algorithm for single phase to ground faults on parallel lines is proposed. The proposed algorithm only requires sampled current and voltage values at one end of the protected line to calculate the fault impedance. The adjacent circuit zero-sequence current can be calculated from the protected circuit zero-sequence current and without cross-connection. The algorithm can overcome the issues of overreach and under-reach. The study in this paper shows that the new algorithm has higher reliability than that of conventional distance relays with and without cross-connected zero-sequence current compensation. Therefore, the algorithm optimizes the performance of zone-one distance relaying for parallel transmission lines. The results are verified by the simulations using PSCAD software.

The proposed algorithm only requires sampled current and voltage values at one end of the protected transmission line to calculate the fault impedance. Zero-sequence current of adjacent line can be expressed by that of protected line. The algorithm can overcome the problems of overreach and under-reach.Figure optionsDownload as PowerPoint slide