10 kV配电变压器雷电过电压及其防治方法研究

Ｒesearch on Lightning Overvoltage of 10 kV Distribution Transformer and It Prevention Method

摘要:

10 k V台区配电变压器是配电网最重要的设备之一,但在多雷区时常发生雷击损坏故障。根据台区典型设计和现场勘查结果,建立了雷电直击导线和雷电感应下的电磁暂态仿真模型,分析了配电变压器高压侧绝缘的雷电过电压,结果如下:雷电直击导线后,变压器绝缘承受的电压为避雷器残压和接地引下线电压之和,过电压幅值极易超过标准雷电耐受电压75 k V;雷电感应的能量较小,过电压幅值超过标准雷电耐受电压的概率非常小。同时,研究了加装避雷线对雷电直击过电压的防治效果,发现避雷线可大幅降低过电压幅值,若在此基础上缩短避雷器横担至变压器支架的电气距离,可大大降低变压器损坏概率。

Abstract:

Distribution transformer in 10 kV power distribution area is one of the most important equipment in distribution network． However，it is often be damaged by lightning in the area with more lightning activities． According to the typical design and the field investigation，the electromagnetic transient simulation model for lightning direct striking and lightning induction is established，and the lightning overvoltage of high voltage side insulation on distribution transformer is analyzed． The results are as follows: After lightning directly striking conductor，the voltage suffered by transformer insulation is the sum of the residual voltage of lightning arrester and the voltage of ground lead． The amplitude of overvoltage easily exceeds the standard lightning withstand voltage，which is 75 kV． Because the energy induced by lightning is small，the probability that overvoltage amplitude exceeding the standard lightning withstand voltage is very small． The preventive effect of adding lightning arrester on lightning direct overvoltage is studied． It is found that lightning arrester can greatly reduce the amplitude of overvoltage． If the electric distance between the arrester cross － arm and the transformer support is shortened on this basis，the probability of transformer damage can be greatly reduced