Study on the Failure Causes and Improvement Measures of Arresters in 10 kV Distribution Transformer Areas

In recent years, arresters in 10 kV distribution transformer areas of the Guangdong power grid have exhibited a rising trend of premature failures, posing a serious threat to distribution network reliability. This paper studied the failure causes of arresters through performance tests on failed arresters and through deterioration tests on new arresters and their prorated sections under typical operating stresses. The failed arresters and their internal varistors displayed varying degrees of physical damage and pronounced degradation in electrical performance, characterized by a strong polarity effect on the DC reference voltage (U1mA), elevated DC leakage current (IL) and resistive current (iR), and excessive residual voltage (U5kV). In the lightning impulse test, varistors primarily showed pinhole-type damage and significant polarity effects on ΔU1mA. In the AC aging test, ΔU5kV increased markedly. In the water immersion test, varistors exhibited salt deposits and aluminum electrode blackening, with ΔU1mA decreasing, while IL and ΔiR increased significantly. Overall, internal moisture superimposed on other operating stresses was identified as a major internal cause of arrester failure, while pollution flashover of the housing was considered the primary external factor. Corresponding improvement measures in material optimization, testing and inspection, and operation and maintenance are proposed to enhance arrester reliability.