Development of Wide Area Protection & Coordination for PEA’s 115 kV Closed Loop Transmission Lines in Chiang Mai Area

This paper presents a method that could be implemented to wide area protection and coordination (WAPC) for transmission lines. The aims of this method are to improve protection performance and decrease the mal-operation of protection relays due to the increasing of infeed currents from external sources. The scope of the study is 115 kV closed loop transmission system of Provincial Electricity Authority (PEA) in Chiang Mai area. The primary protection of the studied transmission system is stepped distance elements. The backup protections are the upstream stepped distance elements and directional overcurrent elements. Coordinating the primary and backup elements is to manage a time sequence of the element to trip respectively. In this paper, it will be shown that the method of coordinating the distance relays can assist the protection engineer to set the protection relays more correctly and effectively.