Simulation Of Distributed Current Limiting Strategy For 500kV Substation

As the grid load continues to increase,the short-circuit current level gradually increases.The short-circuit current in many areas of the Guangdong power grid has far exceeded the breaking capacity of the circuit breaker,resulting in the threat of safe and stable operation of the power grid.The problem of the increasingly serious short-circuit current exceeding the standard needs to be solved urgently.The research status of current limiting measures at home and abroad in recent years shows that the current limiting effect of the fault current limiter(FCL)is obvious,which is an ideal choice at present.Based on the previous research.This paper proposes a fault current limiter based on fast vacuum switch combined with fast vacuum switch and current limiting reactor.The fault current limiter has the advantages of simple structure,fast current limiting speed and small loss.The different installation positions of the fault current limiter in the power grid are analyzed.Improve on the basis of existing centralized current limiting schemes,a distributed current limiting scheme is adopted.By comparing the centralized current limiting scheme and the distributed current limiting scheme under different types of faults,the distributed current limiting scheme is more reasonable,which has low cost,large range and good current limiting effect.According to the actual parameters of Zengcheng Station,the modeling and simulation in PSCAD4.5 software verified the feasibility of the model.Applying the phase-breaking technology of the circuit breaker to the FCL to achieve the purpose of short-circuit current controlled current limiting.The current short circuit current zero-crossing prediction algorithm is simulated and compared,and the adaptive RLS algorithm is selected and its performance is simulated by MATLAB software.Commutation effect of the controlled fault current limiting(CFL)and the directly fault current limiting(DFL)were compared and analyzed.The results show that tthe controlled fault current limiting(CFL)has short arcing time and low arc energy,which is beneficial to the successful commutation of the fast vacuum switch body and the fault current limiter.But it is possible to extend the current limit time.The continuous transition model of the fault current limiter based on the fast vacuum switch is established,and the breaking process of the fast vacuum switch is simulated.The overvoltage of the current limiter under different working conditions is simulated and analyzed by PSCAD4.5 software.The results show that when only one current limiting module is input,the current limiting module does not synchronize the input and the differentintercepting value,when the lightning arrester is not added,the overvoltage is high.After the lightning arrester is added,the overvoltage is obviously suppressed.The fault current limiter was installed in the system.According to the actual parameters of Guangdong Zengcheng station,a distributed current limiting system model was established to simulate the current limiting effect when faults occur in different locations.The simulation results show that when the Zengcheng station implements the distributed current limiting scheme,the short-circuit current can be limited to 63 kA or less,the current limiting rate is 15%,and there is no obvious overvoltage in the current limiting process,which meets the requirements of the China Southern Power Grid Science Research Institute.