Travelling-wave techniques applied to ultrahigh-speed distance protection

The report describes an investigation into a technique for a high-speed distance protective relay based on the propagation of travelling waves initiated by a fault. The distance to the fault is determined by the time difference between the wave approaching the fault and the corresponding wave reflected at the fault, as they pass the measuring point. In a three-phase transmission line, modal analysis is used to decouple the solutions of the wave equations into three independent modes of propagation. The time-delayed modal components describing the wave approaching the fault are cross-correlated against the components reflected at the fault. The peak output in the cross-correlation function occurs when the time delay in the incident wave causes the two signals to be matched. The signal conditioning and correlation detector are designed using analog circuitry incorporating charge coupled device technology.