Evaluation of ability to withstand short circuit and development of large capacity 500 kV autotransformer

Abstract

Once the short circuit damage accident of a large capacity 500 kV transformer occurs suddenly, it will seriously affect the safe operation of the power grid. The article expounds on the calculation principle and evaluation method of the transformer's ability to withstand short circuit, then introduces the design structure of 400 MVA/500 kV short circuit autotransformer and calculates the electromagnetic force and evaluates the ability to withstand short circuit under high voltage - medium voltage (HV-MV) and medium voltage - low voltage (MV-LV) conditions. By comparing with typical 110 kV and 220 kV transformers, the short-circuit characteristics are analysed, the control strategy is proposed, and the largest capacity short circuit prototype with 400 MVA/500 kV autotransformer is developed. Last, the sudden short circuit test is carried out in the large current test centre. The results show that the large capacity autotransformer passed the big current impulse under HV-MV and MV-LV short circuit conditions for the first time in the world, and all indicators are good, which confirms the accuracy of the strength check and the effectiveness of the short circuit evaluation method and also proves that the 500 kV autotransformer has strong strength to withstand short circuits.