Simulation Analysis and Treatment of Main Transformer Fault in a Hydropower Station

The present paper, based on a hydropower station with an outgoing voltage of 220 kV, examines the situation where a main transformer tripped due to a lightning surge overvoltage, resulting in the burnout of the windings near the transformer's neutral point. Utilizing the electromagnetic transient simulation software ATP-EMTP, initial and oscillating potential distribution equivalent circuit models of the transformer windings were constructed. An excitation source was added to the model's terminal, This analysis aimed to explore the initial potential, and oscillating potential distribution between the transformer's windings under two scenarios: neutral point gap breakdown and neutral point gap intact, and to discuss the causes of internal faults within the transformer. Furthermore, a comprehensive electromagnetic transient simulation model was established, encompassing the 220 kV GIS substation, transmission towers, power lines, generators, and transformers, to simulate and analyze several typical conditions that could lead to internal faults in the transformer. Additionally, preventive measures were proposed to prevent similar faults from occurring in the main transformer in the future.