Modeling and simulation of interturn short-circuit faults in ultra-high voltage converter transformers
In recent years,internal short-circuit faults inside ultra-high voltage(UHV)converter transformers have led to a spate of explosive fires,posing a serious threat to the safe and reliable operation of power systems.In this paper,taking a typical single-phase four-limb converter transformer of±800 kV UHV converter station as a re-search case,modeling and simulation of winding interturn short-circuit fault are carried out on ANSYS Maxwell&Simplorer platform.The variation characteristics of radial leakage flux,the short-circuit current and the arcing fault energy under different fault scenarios are investigated.The results show that the normal axial flux distribution is dis-turbed by a large amount of radial leakage flux inside the converter transformer with the occurrence of interturn short-circuit fault,and high-amplitude fault circulating current emerges in the short-circuit loop.Under a 1.98%interturn short-circuit fault,the magnetic leakage flux density reaches 2.76 T at peak,the short-circuit circulating current reaches 80.59 kA at peak,and the fault energy released over four cycles reaches 1.22 MJ.According to the law of ampere-turn balance,the more the shorted turn number,the lower the circulating current amplitude.However,since the average arc voltage increases monotonically with the arc length,the overall arc energy is posi-tively correlated with the number of shorted turns.In addition,interturn short-circuit faults closer to the middle part of the winding are more serious due to the difference in leakage inductance caused by the leakage distortion.
ultra-high voltage(UHV)converter transformerinterturn short-circuit faultoil-gas arc modelmod-eling and simulation
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