Study on the Influence Mechanism of Side Surface Treatment Technology for ZnO Varistors

ABSTRACT Zinc oxide (ZnO) varistors serve as the core component of metal oxide arresters, and their energy withstand capability directly determines the ability of arresters to resist high‐current impulse surges. To elucidate the influence mechanism of side surface treatment technology, three types of samples were prepared in this study: insulating varnish coating, high‐resistance layer integrated sintering, and in situ repair medium secondary sintering. These samples were subjected to volt‐ampere characteristic testing, 2‐ms square‐wave impulse current withstand tests, scanning electron microscopy characterization, and current distribution characteristic tests. The results show that the insulating varnish exhibits poor adhesion to the substrate and ineffective pore filling; under high‐current impulse conditions, thermal stress concentration leads to side coating detachment, resulting in a 2‐ms square‐wave withstand capacity of merely 500 A. The high‐resistance layer improves both adhesion and pore filling effectiveness; however, it fails to address the thermal perforation failure caused by non‐uniform electric field distribution at the edges, increasing the 2‐ms square‐wave withstand capacity to 700 A. The in situ repair medium treatment achieves optimal adhesion and pore filling performance, with significantly enhanced uniformity of current distribution, enabling a 2‐ms square‐wave withstand capacity of up to 950 A, albeit at the cost of decreased voltage gradient and increased leakage current. This study provides essential theoretical foundations for enhancing the energy withstand capability of ZnO varistors.