Adaptive Distance Relay for Statcom Connected Transmission Lines - Development of Dsp Based Relay Hardware, Relaying Schemes and Hil Testing Procedures

Abstract

Flexible AC Transmission System (FACTS) devices are used to enhance the transient stability limit and power transfer capacity of the existing transmission lines. Static Synchronous Compensator (STATCOM) a shunt type FACTS device is used to maintain the voltage at the point of common coupling on the transmission lines. A STATCOM has fast response of about 1-2 fundamental cycles, which matches with the typical response time of the protection subsystem. Hence, its functional characteristics and associated control system introduce dynamic changes during fault conditions in a transmission line. It is important that distance relays perform correctly irrespective of such dynamic changes introduced during faults, as it defeats the purpose of STATCOM installation. The work presented in this thesis is aimed at detailed study on the influence of STATCOM on the performance of distance relay under normal and abnormal operating conditions of the power systems. The work also put forth adaptive distance relaying schemes to mitigate the adverse of impact of STATCOM on distance relay. Its performance is compared with the conventional standalone mho type distance relay, through simulations on a realistic study power system using EMTDC/PSCAD package. A relay hardware to implement, the adaptive relaying scheme has been developed using TMS320F28335 digital signal processor and a simultaneous sampling ADS8556 analog to digital converter. The real time hardware in the loop test bench has been developed, using Doble F6150 power system simulator, to test the performance of the newly developed relaying schemes and relay hardware. The simulation results obtained from EMTDC/PSCAD are used as test signals for this purpose. The evaluation results have clearly demonstrated, the efficacy of the adaptive relaying schemes in mitigating the adverse impact of STATCOM on the distance relay performance.