±1100kV换流站避雷器小电流区阻抗特性

Impedance Characteristic in Low Current Region of MOA at μ1 100 kV Converter Station

±1100 kV换流站避雷器(MOA)节点持续运行电压谐波含量高、波形差异大、避雷器荷电率高,而避雷器小电流区阻抗特性直接影响持续运行电压下的功耗、泄漏电流及伏安特性等,阻抗特性与运行电压频率、波形和温度密切相关,因此避雷器呈现不同劣化特性,威胁避雷器的运行安全。该文仿真分析了换流站直流场避雷器节点持续运行电压的负荷特征,试验研究了直流避雷器用金属氧化物电阻片(MOV)在不同工作温度、谐波频率和荷电率下等值阻抗的变化特性。试验结果表明:随着谐波负荷和工作温度的升高,泄漏电流阻性和容性分量均增大,等值阻抗呈减小趋势;等效阻抗由容性变为阻性的转折点出现在100%~105%荷电率范围,转折点对应的荷电率在60℃时降至95%、在150 Hz时升至107%;持续运行电压下谐波含量增加或工作温度升高,导致实际运行荷电率升高。

The contents of voltage harmonic, waveform differences, and charge rates at metal oxide arrester(MOA) nodes in ±1 100 kV converter stations are high or remarkable. The impedance characteristic of MOA in small current region, which directly affects the power consumption, leakage current and U–I characteristic, is closely related to voltage frequency, waveform, and temperature. Therefore, MOAs exhibit different degradation characteristics which threaten to their safety. In this paper, the load characteristics of continuous operating voltages of DC MOAs in the converter station are simulated and analyzed. The variation characteristics of equivalent impedance of the metal-oxide varistor(MOV) are experimentally studied under different temperatures, voltage frequencies, and charge rates. The results reveal that, as the harmonic load and temperature increase, the resistive and capacitive components of leakage current will increase and the equivalent impedance will decrease. A turning point from capacitive to resistive equivalent impedance will appear in the range of 100% to 105% charge rate. The charge rate of the turning point is changed into 95% at 60 ℃ and 107% at 150 Hz. The increase in harmonic content or temperature under continuous operating voltage leads to an increase of actual operating charge rate.