Effect of SSSC-based SSR controller on the performance of distance relay and adaptive approach using synchronized measurement

The use of series compensation in a transmission line with capacitors may result in new problems like torsional oscillations in shaft sections of turbine-generator due to subsynchronous resonance (SSR) when system frequency matches with any one of torsional mode frequency of shaft system during fault or disturbances occur in the transmission line. The subsynchronous current due to SSR during fault also affects the reach of a distance protection system. The diminution of SSR is enhanced by series voltage injection into the power transmission line with static synchronous series compensator (SSSC) from the knowledge of subsynchronous components, extracted from the system. The use of SSSC in transmission line reduces the subsynchronous oscillations, but it adversely affects the distance protection system which leads to an imprecise assessment of fault location, ie, over or under-reach. This paper investigates the SSR mitigation in the presence of SSSC and its effect on distance protection scheme. A new approach is proposed for mitigating the problems associated with distance protection by using the synchrophasor measurement. The entire study of simulation is investigated by using a 48-pulse SSSC carried out with Bergeron model of transmission line in PSCAD. The simulation results represent that the suggested adaptive scheme is truthful, reliable, and secure with a change in compensation level of SSSC.