特高压变压器雷电冲击伏秒特性研究

随着750 kV、1000 kV输电技术的发展，相应的电力变压器和并联电抗器的容量、尺寸和入口电容随之增大，试验回路尺寸亦相应扩大，这使雷电冲击试验电压的波前时间拉长，无法达到国内外标准的要求。根据500 kV、750 kV和1000 kV变压器和电抗器的实际雷电冲击试验波形，结合油纸复合绝缘结构的雷电伏秒特性，分析了不同波前时间对特高压变压器和电抗器绝缘水平的影响。目前变压器的设计计算和试验电压的选取一般按照标准波头进行，而充油设备的雷电冲击伏秒特性表明，雷电冲击试验电压波前时间的长短与绝缘强度有密切关系，波前时间延长可能会对某些纵绝缘的考核偏松，同时对主绝缘的考核偏严。因此，应在特高压变压器、电抗器的设计研制和试验中，考虑和重视雷电冲击波形波前时间延长所带来的影响。

Study on Volt-Time Characteristics of UHV Transformer Under Lightning Impulse

Along with the rapid development of power transmission technology for the 750kV and above voltage grade,the capacity,dimension and entrance capacitance of corresponding power transformer and shunt reactor increase and accordingly the dimension of testing circuit is enlarged accordingly,thus it makes the wave front time of lightning impulse testing voltage elongated and the qualification in the both national and international standards can hardly be met.According to the waveforms from actual 500 kV,750 kV and 1 000 kV lightning impulse tests and combining with the lightning voltage-time characteristics of oil-paper combination insulation structure,the impacts of various wave front time on insulation level of UHV power transformers and reactors are analyzed.At present,the design calculation and the selection of testing voltage are generally based on standard wave front,however the lightning impulse voltage-time characteristics of oil-immersed equipments show that the length of wave front time of lightning impulse testing voltage is closely related to insulation strength,elongated wave front time may make the examination for some longitudinal insulation relaxed and that for main insulation more strict.Therefore,in the design,development and testing of UHV power transformers and reactors the impacts brought by elongated wave front time of lightning impulse waveform should be considered and paid special attention to.