Application and development research of 220kV transformer protection with special configuration based on impedance algorithm

This paper describes that the use of large capacity110kV transformers in Jiangsu power grid makes the mismatch between the capacity of 220kV transformer and the capacity of 110kV transformer. As the capacity of 110kV transformer is too large, its short-circuit impedance is relative small, while the capacity of 220kV transformer capacity is relative small, the conventional configuration and setting of transformer protection may results in the conflict between the protection of the 110kV line, the back-up protection of 220kV transformer and 110kV transformer protection, Which may lead to leapfrog trip of the back-up protection of 110kV side of 220kV transformer, and the wide-area blackout. This paper sets out the strategy and feasibility way to solve the problem, such as the using of the large-capacity 220kV transformer, but it is unrealistic. This paper puts forward a simple and effective way that the impedance protection is used as the corresponding back-up protection of 220kV transformer. Cooperating with two companies, the protection device based on impedance protection has been developed. The result of static test and dynamic test showed that the configuration is effective and feasible.