Protection scheme for transmission lines based on alienation coefficients for current signals

Abstract

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for faults detection and discrimination. The proposed technique is able to accurately identify the condition of phase(s) involved in all ten types of shunt faults that may occur in extra high-voltage transmission lines under different fault resistances, inception angle and loading levels. The proposed technique does not need any extra equipment as it depends only on the three line-currents measurements which are mostly available at the relay location. This technique is able to perform the fault detection, type and phase selection in about a half-cycle period. Thus, the proposed technique is well suited for implementation in digital protection schemes. The proposed methodology is applied for a part of 500 KV Egyptian network. Alternative transient program and MATLAB programs are used to implement the proposed technique.