Experimental study on the impulse aging of varistors in the arrester of 500kV AC filter

The impulse current of the 500 kV AC filter arresters is very high when the AC filter bank circuit breaker is switched and the closing phase angle is large in some ±800 kV and ±500 kV converter stations. The frequent high current will accelerate aging of the arresters and then threaten the safe operation of converter stations.In this paper, based on the measured impulse current waveform of the arresters during the switching on process of AC filter bank, the impulse aging experiments of ZnO varistors of AC filter arrester under the negative polarity 15/35 µs impulse current with an amplitude of 15 kA was carried out. Firstly, in order to shorten the experiments cycle, each group of the impulse aging experiments consists of 50 times impulses. Secondly, combined with the experiments results and calculation analysis, the variation of electrical characteristic parameters such as DC reference voltage (U
0.01mA
, U
0.1mA
and U
1mA
), capacitance C, residual voltage ratio β and nonlinear coefficient α
2
of ZnO varistors during the experiments process were obtained. Finally, the variation regularities of electrical characteristic parameters of ZnO varistors obtained by a large number of single impulse aging experiments in other papers were compared and analyzed. The results show that the overall variation trend of electrical characteristic parameters of ZnO varistors obtained by each group of the impulse aging experiments with 50 times impulses is almost the same as that obtained by the single impulse aging experiments.