DefinePK

Abstract

For electrical power transmission system, a high voltage protection scheme provides prevention against the hazards in the form of lightning, ferranti effect, and power fluctuations. When these conditions occur, the power system can experience an over voltage which may be two to three times greater than its rated value. During these kinds of abnormal conditions, protective relays play a crucial role in protecting the system. In this work, the authors have analyzed the performance of four different relays (overcurrent, over/under voltage, distance, and differential relays). Analyses are based on the operating time under different faults occurring on 80-250 km long 400 kV high voltage AC transmission lines. MATLAB has been used to model and analyze the system for identifying different types of faults in a transmission line. The main objective of this work is to compare the operating times of the most important four relays under conditions of single line to ground fault (LG), three phase fault (LLLG) and double phase to ground fault (LLG). In this situation, the system outputs are observed under normal, fault, and no-fault conditions, and the response time is calculated to turn on a circuit breaker. It is envisioned that this work will be one-stop source of guidance for protection engineers to select proper relays for the newly installed power systems.