A novel energy ratio direction relay based on equivalent travelling-wave process

An effective analysis method is required to analyse the entire travelling wave (TW) process, which includes the initial and succeeding TWs. As TW directional protection only uses the initial TWs to avoid potential confusion that may be caused by the aliasing of TWs, a long-term reliable criterion is difficult to offer. Thus, this presentation proposes an analysis method for the whole TW process based on an equivalent TW process and a novel directional protection approach. Based on this equivalent TW process, the protection can overcome the limit of presenting long-term criterion, the problem of detecting a fault close to the relay location, and the insufficient sensitivity under the fault with an inception angle near zero that troubles the conventional TW directional protection. Extensive simulation in EMTP/ATP verified the performance of this protection.