交直流电压分量对变压器油中典型模型击穿特性影响

Influences of AC and DC Voltage Component on Typical Insulation Model Breakdown Characteristics in Transformer Oil

在高压直流输电系统中,绝缘系统如换流变压器阀侧绝缘长期运行中不仅承受交流电压,还要受到直流电压的作用。由于在换流变压器试验过程中无法模拟交流和直流复合电压作用这一实际工况,交-直流合成电压对油纸绝缘特性影响缺乏深入研究。本文以典型针-板模型为例,同时施加不同交、直流分量,研究变压器油在针-板模型中的击穿特性。试验结果首次揭示了不同交直流分量对针-板模型击穿特性的影响。结果表明:典型针-板电极模型在交-直流复合电压作用下,随着预加直流分量的上升,模型交流击穿电压呈线性下降;随着预加交流分量的上升,模型直流击穿电压也呈线性下降。通过对比分析表明,不同预加电压类型对模型击穿特性存在明显影响,且预加交流电压下的模型击穿电压高于预加直流条件下的模型击穿电压。

In the HVDC transmission system,the failure of converter transformer is the key problem for the electrical power system safety.Oil-paper insulation system in converter transformer bears AC and DC voltage in their lifetime.Since having no way to simulate its actual working condition,usually,AC and DC test voltage are separately imposed on the transformer during the factory test.Different influences of AC and DC voltage on the insulation characteristics are unknown.This paper designs a needle-plate model,and imposes different AC and DC voltage values to the oil surrounded needle-plate model to study the differences of breakdown characteristics.The test reveales the different effects of AC and DC voltages to the insulation model breakdown characteristics.The results indicate that under the combined AC and DC voltage,the AC breakdown voltage decline linearly as the pre-DC-voltage value increase and vice versa.The result also suggests the pre-stressed voltage type affects the test result obviously and for the oil surrounded needle-plate model,the breakdown voltage value of pre-stressed AC-voltage is higher than the condition of pre-stressed DC-voltage.