Impacts of protection system misoperation on the reliability of Turkish National Power Transmission System

This paper presents the analysis of relay system to identify the effects of misoperations on system reliability in the Thrace part of Turkish National Power Transmission System comprising 154 kV and 380 kV sub-systems. Since one of the main reasons of the cascading failures is the misoperation of the protection system, this study is concentrated on the analysis of relay system to minimize the risk of occurring cascading events as well as to improve the reliability level of the system. Initially, a detailed system model is constructed according to the collected system data and the protection system data such as relay types, relay settings etc. Simulations are then performed by an integrated power system analysis tool DigSilent Powerfactory software. The system is tested for predefined fault scenarios. Depending upon the consequences of misoperation of the protection system, cascading failure risks and decrease in the reliability level of the system are determined. Simulations and the calculations, cover the distance protection relays and over-current relays.