Analysis of the Reasons for the Failed 10 kV MOA Based on Impulse Aging and Power Frequency Aging Tests

Due to lightning strikes and prolonged power frequency voltage exposure, frequent failures and defects caused by the decommissioning of 10 kV surge arresters in the power grid severely affect the reliability and stability of power supply. Therefore, this study selects $\mathbf{Z n O}$ varistor samples from mainstream 10 kV arrester manufacturers to conduct impulse aging tests and power frequency aging tests in order to investigate the reasons behind the failure and decommissioning of 10 kV arresters. During the tests, the following parameters were measured: the positive/negative $D C$ reference voltage $\left(U_{1 \mathrm{~mA}}\right)$, the leakage current at 0.75 times $U_{1 \mathrm{~mA}}$ under positive/negative voltage, the resistive current under continuous operating voltage, and its harmonic characteristics. Finally, a comparative analysis of the electrical performance trends and differences in failure modes of the samples under the two tests was made. The results show that under impulse aging tests, the performance of the ZnO varistors deteriorated continuously, leading to failure modes such as cracking and pinhole defects. However, in power frequency aging tests, the performance of the ZnO varistors was improved, and no failure modes were observed. Based on these findings, it is speculated that the failures and decommissioning of 10 kV surge arresters are mainly caused by lightning impulses. Future research should focus on enhancing the impulse withstand capability of $\mathbf{Z n O}$ varistors in 10 kV surge arresters.