35kV金属氧化物避雷器雷电冲击老化性能的研究

Research of Degradation Performance of 35kV MOA under Lightning Impulses

研究了在连续雷电冲击电流(8/20μs)作用下,35 kV金属氧化物避雷器小电流特性与残压特性的变化规律,以及避雷器内部电阻片的老化特点及失效方式。35 kV避雷器受到连续雷电冲击时,存在一冲击阈值(850次),当冲击次数低于该阈值时避雷器小电流及残压特性几乎不变,当冲击次数大于该阈值时,避雷器小电流及残压特性发生明显劣化;雷电冲击造成避雷器的失效主要是由内部电阻片沿面闪络引起的,并在避雷器接地端首先发生沿面闪络现象;氧化锌电阻片受到雷电冲击后性能出现方向性差异。该研究为35 kV等级的避雷器运行的雷电冲击老化寿命评估和失效方式预防提供了实验依据。

The low current and the residual voltage characteristics of the 35 kV metal oxide arrester （MOA） are studied under the continuous applications of 8/20 μs impulse current. The degradation feature and damage mechanism of the varistors in the MOA are also researched. There is a threshold of impulse application number （850） when the 35 kV MOA are applied by continuous lightning impulses. The low current and the residual voltage characteristics will keep constant if the impulse application number is less than the threshold. But, if the impulse application number is greater than the threshold, the residual voltage characteristics will degraded obviously. The damage of MOA resulted from lightning impulse is mainly caused by the surface flashover along the varistors, and such flashover often occur at grounding terminal of MOA in the beginning stage. The ZnO varistor will present the directional deviation after the stresses by lightning impulses. The study results will supply the experimental basis to evaluate the degradation life and to prevent damage of 35 kV MOA in service.