Research And Application Of Fault Current Limiter In Low Voltage Side Of Transformer

The short-circuit current is in excess of31.5-40kA and the part is even above60kA When the low voltage side of large capacity transformer breaks down. The interrupting capacity of universal circuit breaker in the substation is not more than40kA and the full breaking time is more than100ms. The power transformer is damaged for being unable to withstand the impact of short-circuit current and is incapable of large short-circuit current. A special circuit breaker which can break63-100kA is costly, each cost millions of yuan. How to realize quick short-circuit protection function for lOkV side of large capacity transformer is the key to solve the problem under the controllable investment cost and combination of current limiting device and circuit breaker.There are a lot of study results about current limiter. At the same time, the situation of low-voltage side of transformer is complex and need to cooperate with various equipment and protection system to realize rapid protection when installing current limiter. With the further development current limiting technology, limited performance is greatly improved. The current limiter can be can be widely installed on the low voltage side of transformer combining with vacuum circuit breaker to complete the short circuit protection in order to reduce the damage of the short-circuit current on transformer.This paper proposes to have DDXK1, a new large current-limiter with high speed and super capacity, and general vacuum circuit breaker in series as short-circuit protection for10kV side of large capacity transformer. The paper also puts forward the design, installation and operation of sets of equipment of typical demonstration project in order to solve the problem of short-circuit damage of large capacity transformer and improve the level of transformer protection.The paper study main technology of limiter, such as fault current limiter and solid-state limiting and so on, with reseach status and key technology of the limiter. The paper analyzes their technical principle, advantages and disadvantages, summarizes the application scope of limiter. Based on current technology research and combined with the current actual situation at the scene of substation system, such as transformer, circuit breaker, switch, relay protection, the paper analyses the feasibility of new method combining DDXK1limiter with general vacuum circuit breaker using in short-circuit protection for the10kV side of large capacity transformer with the research status and key technology of current limiter.At the same time, the paper study the electronic control technology and relay protection technology. Combined with the low voltage side of transformer short-circuit protection scheme, the paper also propose the design and optimization of electronic control system and the cooperation program of current limiter and replay protection. The operation and maintenance guidelines are made combined with the actual case providing experience for the application of this advanced technology in power system.The DDXK1of high current limiter which is advanced, functional, safe and reliable can reduce the output short-circuit current of transformer. The application can prevent the damage of short-circuit, reduce the circuit breakers and bus accidents, improve the reliability of power supply and save the technical infrastructure investment. It has significant economic and social benefits.