Research On System Condition Of Fault Current Limiter Based On High Coupled Split Reactor With Automatic Current Sharing And Limiting Technology

With the rapid increase of power load in China,the short-circuit capacities at central nodes of many power grids are growing continully.When a short-circuit fault occurs,the short-circuit current will reach or even exceed the breaking capacity of the circuit breaker,which makes the breaker unable to act in time and effectively,thus causing a larger area of power failure accidents,seriously threatening the operation safety of the power grid.In order to solve the problem of excessive short-circuit current in the development of 500kV power grid,a kind of current limiter based on High Coupling Split Reactor(HCSR)automatic current sharing technology is proposed,which can effectively limit the short-circuit current and improve the breaking capacity of the circuit breaker.Due to the connection of high coupling reactor in the current limiter,there are small distributed capacitors at both ends,arms and to the ground,which will affect the transient recovery voltage(TRV)of circuit breaker during breaking.In order to realize the engineering application of the current limiter based on the HCSR,it is necessary to build a simulation model according to the detailed system conditions,carry out simulation calculation for the TRV characteristics of the circuit breaker in the process of breaking in case of various types of short-circuit faults in the system,carry out detailed analysis on the special problems,and put forward the corresponding technical measures,so as to provide reference for the development and application of the current limiter.Firstly,this paper analyzes the structure and working principle of HCSR current limiter in limiting short-circuit current,divides its breaking process into current sharing breaking and current limiting breaking according to technical characteristics,and calculates the time-domain expression of breaking voltage of two circuit breakers respectively.Comparing with current sharing breaking,current limiting breaking is much harder.The transient current and voltage are closely related to the coupling inductance and distributed capacitance of the current limiter.Then the circuit simulation model of HCSR current limiter is built.Based on the engineering example of a typical 500kV system,in which short circuit current exceeding the standard,the main technical parameters of the current limiter are researched.The coupling coefficient,reactance value and parameter calculation formula of distributed capacitance of current limiter are studied.According to the effect of limiting short-circuit current,the key technical requirements of current limiter,such as rated parameters,overload capacity,short-circuit current withstand capacity,over-voltage and suppression measures,are put forward.Finally,the electromagnetic transient process of fault breaking in the system with current limiter is simulated and verified.According to different fault types and fault locations,this paper analyzes the operation effect of hcsr current limiter put into operation and its influence on system over-voltage,and analyzes the influence of different breaking process,current limiter structure,splitting reactor parameters,circuit breaker closure,etc.on hcsr breaking effect.The test results show that when the circuit breakers of current limiter don't operate at the same time,the TRV of later circuit breaker exceeds the standard without countermeasures.The peak value of TRV can be effectively suppressed by connecting ZnO arrester in the break of circuit breaker,and the rise rate of TRV can be effectively reduced by connecting capacitors at both ends of series reactor.