A Weak Fault Adaptive Traveling Wave Protection Method for Bus and Transmission Line

With the increasing number of ultrahigh-voltage transmission lines, the protection with ultrahigh speed is increasingly urgent. Traveling wave protection has the advantage of ultrahigh speed. But it has not yet been widely applied, because it has low reliability in the condition of weak faults, i.e. small initial fault angle and large transition resistance. The reliability of traveling wave protection is low because the initial fault angle and transition resistance have great influence on the transient quantity produced by the fault. This paper proposed a relay basing on the high-frequency fault current which was normalized by initial fault angle and transition resistance. The normalized fault high frequency current contains initial fault angle and transition resistance information. It removed the influence of fault angle and transition resistance by using the normalized high frequency current to construct the action criterion for fault judgment. It improved the algorithm's reliability. In this algorithm, the fault high frequency current and fault direction were used as joint criteria for fault judgment. The presented method protects a bus and a transmission line at the same time. It was verified using ATP/EMTP. Simulation results showed the algorithm reliably determined whether the fault was occurring in the line, or in the busbar, or outer side zone.