Research Of Current-limiting Characteristics Of The Transformer-Type Fault Current Limiter

As the China’s power grid scale expands, the power load grows rapidly, more large capacity units put into use and the major power grids interconnect closely, the level of power system short-circuit current is increasing day by day, which is a serious threat to the safe operation of the power system. So, how to limit short-circuit current has been an inevitable technical and economic issue in the development of China’s power industry. It’s an effective measure to limit short-circuit current by installing fault current limiter (FCL) in power system. This paper introduces transformer-type FCL, analyzing its advantages and disadvantages and its current-limiting characteristics based on the status of its research and development at home and abroad.This paper introduces the basic principle of transformer-type FCL that is composed of a capacitor in parallel with primary side of a transformer whose second side is connected to a discharge gap. The current-limiting effect and the conditions are described quantitatively by analyzing the steady-state characteristics while the fault current limiter is limiting short-circuit current, which demonstrates the feasibility of the scheme in principle. The application of the fault current limiter is simulated in a500kV transmission system and a10kV distribution system respectively with PSCAD/EMTDC software which can creates the equivalent simulation model. For500kV ultra-high voltage system, the current-limiting characteristics of different fault types and sites are analyzed. Meanwhile, the impact of the parameters of the FCL on the current-limiting characteristics is discussed in detail. Through the theoretical analysis and simulation, the effect of the FCL on the transient stability of power system and the breaking characteristics of circuit breaker is researched. Taking exiting laboratory conditions into account, the short-circuit experiment is carried out to verify the current-limiting effect of the FCL on the basis of theoretical analysis and simulation.Finally, the simulation and experiment results show that the transformer-type FCL has a good effect on limiting short-circuit current, which reduces dynamic and thermal burden of circuit breaker and other electrical equipment and improves operational reliability and service life of the equipment and the stability of power system. Generally speaking, the FCL achieves a machine meeting several purposes by combining series reactive power compensation with current-limiting function. Moreover, the FCL has a simple structure that can realize automatic switching without additional control, which is helpful to realize high-voltage and large-capacity and makes the FCL more cost-effective. Therefore, the FCL is an effective current-limiting scheme reflecting broad application prospect to limit short-circuit current in power system.