A Protection and Fault Location Scheme for EHV Line Based on Single- Ended Technique

Abstract

Extra High voltage (EHV) transmission lines are designed to transfer large amount of power from one location to another. The transmission line protection relays, in the industry, are based on the fundamental frequency component of the voltages and currents. These relays need at least one fundamental frequency cycle for performing the protection operation. Voltage and current traveling waves are generated when a fault occurs on the transmission line. The velocity of propagation of traveling waves is finite and the level of the waves decreases with increase in the distance traveled. Information about the fault can be obtained by analyzing the traveling waves. Single-ended technique, which use traveling waves for protecting EHV transmission lines, are proposed in this paper. The traveling waves are extracted from the modal voltages and currents at the terminals of the transmission line. The technique identify and locate the fault by using the information contained in the waves. A power system was modeled in the Electromagnetic Transient Direct Current Analysis (EMTDC) and several cases of faults and fault location were tested. The performance of the digital techniques for protecting EHV transmission lines using traveling waves was confirmed to be satisfactory. The proposed technique provide protection at speed and discriminate well between internal and external faults.