Transmission Line Protection Using Decaying DC Information in Fault Current

Today use of fast and reliable transmission line protection is of importance. This article presents two protection techniques for transmission lines using information obtained from the decaying dc component of fault current and the prefault voltage signal. The fault direction is obtained using the polarities of prefault voltage and decaying dc of fault current. Internal faults in the transmission lines are detected with exchange of information on the decaying dc currents at both ends. The protection decisions are derived within a quarter cycle with a signal sampling rate of 4 kHz. Upon testing on a 400-kV simulated transmission system for different fault types, resistances, inception angles, and field data from a 400-kV line, the proposed techniques are found to be accurate.