1000 kV特高压电力变压器绝缘水平及试验技术

中国1 000 kV交流特高压系统绝缘配合不是对 500 kV系统的简单放大，也并未完全依照GB311.1-1997或IEC60071-1-1993标准，是在优化原则下研究确定的。变压器绝缘水平为：雷电冲击耐压2 250 kV、操作冲击耐压 1 800 kV、工频耐压1 100 kV(5 min)。由于特高压变压器各绕组绝缘水平及绝缘试验电压要求不同，而变压器各绕组是通过电磁耦合紧密联系的，工频和操作冲击试验电压在各绕组间按变比传递，因此势必造成有些线端绝缘设计不能按其技术规范所规定的试验电压来考核。此外，特高压电力变压器电压高、容量大、尺寸超大，试验回路尺寸也相应扩大，杂散电感、电容影响也更加突出。这将造成雷电冲击试验电压波形的波头时间拉长，而设计计算一般按照标准波头进行。因此，在特高压变压器绝缘设计中，应关注长波头试验电压的影响。文中详细介绍了中国1 000 kV交流特高压工程用电力变压器的结构特点、绝缘水平及绝缘试验中的特殊问题。

Insulation Level and Test Technology of 1000 kV Power Transformers

The insulation coordination for the first 1000 kV power transmission project in China is studied and decided under the optimization principle, it is not a simply extrapolation of that for 500 kV power transmission system and is nor completely in accordance with the standards of GB311.1-1997 and IEC60071-1-1993. The insulation level of 1000 kV power transformer adheres to following items: the lightning impulse withstand voltage is 2250kV; the switching impulse withstand voltage is 1800 kV; and the power frequency withstand voltage is 1100 kV/5min. Due to the differences among the insulation levels and insulation test voltages for different windings of UHV power transformer and the close electromagnetic coupling among the windings of UHV power transformer, the power frequency and impulse test voltages are transmitted among these windings by the transformer ratio, thus it is bound to bring about the condition that the insulation design for some conductor terminals can not be checked by the test voltage specified in the technical specification. Besides, due to the high voltage class, high capacity and super size of UHV power transformer, the size of its test circuit is correspondingly enlarged, the impacts of stray inductance and capacitance will be more intense consequentially, thus it makes the front time of voltage waveform in lighting impulse test elongated, however, the design and calculation are generally conducted according to standard waveform, thus in the isolation design of UHV power transformer the attention should be paid to the impact of long front time test voltage. In this paper, the structural features and insulation level of power transformer for 1000 kV power transmission project in China as well as special problems during the insulation test are presented in detail.