Research of fault current limiter for 500kV power grid

Configuring large power supply in high load density networks and interconnections between power grids will cause enormous short-circuit current. If the short-circuit current rating of equipment in power system is exceeded, the equipment must be replaced, which is a very cost- and/or time-intensive procedure. A fault current limiter offers a choice in such case. First, this paper attempts to give an overview of fault current limiting measures for medium and high voltage applications. Then several representative fault current limiters including developing and developed measures are examined with an emphasis upon the thyristor protected series capacitor (TPSC) based short-circuit current limiter (SCCL). The SCCL would be the only technical proposal which can be used in high voltage system for its proven technology, low cost, high reliability, powerful performance and easy realization in high voltage system. The technology is used in the fault current limiter demonstration project in East China power grid. First, the main circuit topology of the fault current limiter demonstration project in East China power grid was introduced, together with the parameter specification of main-circuit equipments such as capacitor, reactor, damping circuit, thyristor, spark gap, MOV, and bypass circuit breaker. Then the measures and strategies of the current limiting reactor fast insertion and the over-voltage control and protection upon the series capacitors were introduced. After that the equivalent system of the fault current limiter demonstration project in East China SOOkV power grid was established using PSCAD/EMTDC, with which, an approach to identify fault signal fast based on the line current slope, and the coordination between the slope value and the instantaneous value of line current were studied in details by the aid of PSCAD/EMTDC simulation results. The optimal coordination and corresponding time setting value were given. FCL is series connected to the transmission line and should have influence upon protective relays to some extent. The effect of automatic circuit re-closer on FCL and the co-ordination between FCL control and protection system and protective relays must be researched. The influence of automatic reclosing on FCL and the coordination between FCL protection and line protection were performed by PSCAD/EMTDC simulation, and a simulative analysis-based rational solution was given. To demonstrate the validity of PSCAD/EMTDC simulation results, the real time digital simulation (RTDS) experiment of the control and protection system for FCL demonstration project in East China SOOkV power grid was done. The paper presents the RTDS results which consist of experimental scheme, experimental models, simulation results, and analysis of fault signal identification method and influence of fault current limiter on protective relaying above. Results of RTDS experiment can partially justify the operation of the FCL control and protection system.