大型变压器绕组的特快速暂态过电压计算及防护措施

Computation and Protection Measures of Very Fast Transient Overvoltages in Large Transformer Windings

气体绝缘变电站中特快速暂态过电压会对变压器绝缘造成损害,为此通过有限元方法计算变压器绕组的匝间电容、饼间电容和绕组对地电容,搭建了特快速暂态过电压在变压器绕组中传播的ATP-EMTP仿真模型。仿真结果表明:1)以线匝为单元建立变压器绕组模型可以较准确地仿真绕组中VFTO的传播特性;2)采用改进的纠结式绕组,能有效地减小匝间电压和饼间电压;3)使用内屏蔽–连续式绕组接线,可以有效地改善绕组VFTO分布;4)减小接地电容或者增大纵向电容可以改善VFTO分布,不考虑电导时变压器绕组中VFTO的衰减较慢。

In gas insulated substations, very fast transient overvoltages will impair transformer insulation.Consequently, we calculated the interturn capacitance, the section-to-section capacitance and the ground capacitance of the transformer windings by the finite element method, and established an ATP-EMTP model for the propagation of the very fast transient overvoltages in the transformer windings. The results show that the model of transformer windings based on one turn as an element can simulate the propagation properties of VFTO precisely. The improved interleaved connection mode can decrease the interturn voltage and section-to-section voltage. Inner shield coil can be further used to improve the voltage distribution of VFTO. Reducing the ground capacitance or increasing longitudinal capacitance can improve the VFTO distribution, and the attenuation of VFTO in the transformer windings will be slower if conductance is not considered.