CHEN Yicong, CHEN Zongrang, ZHANG Peng, XU Haodong, SUO Jun, ZHANG Yusheng, ZHU Shuyou, YAN Chenguang
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 research 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 disturbed 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 positively 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.
