Research of the effect for relay protection based on STATCOM

This paper deals with the influence of the STATCOM to the relay protection. The fundamental compensation principle, the main circuit and control strategies of STATCOM are all proposed. Then the mathematical model of the distribution system with STATCOM is established, the three-phase short-circuit fault is analyzed. The EMTDC/PSCAD is used for analyzing the dynamic characteristics and protection of distributed power system during balanced fault. And then the instantaneous over-current protection, the time delay instantaneous over-current protection and definite time over- current protection are installed. The operation logic of the relay protective in distribution system with STATCOM is analyzed. Simulation results show that a STATCOM voltage controller can improve the stability performance of voltage and reduce the reactive and fault current, but the selectivity of the relay protection is impacted. To ensure the protective selectivity, a new five-step protection scheme is presented. The results of the dynamic simulation verify the validity of the presented scheme.