Causes Of Valve Plate Failure During Surge Arrester Operation: Hidden Dangers Deep Within The Power System

During the long-term operation of a power system, the stability of the internal components of lightning surge arrester directly determines the safety of the line. Due to the combined effects of environmental factors and electrical stress, the performance degradation of the valve plate in the surge arresters has become an unavoidable issue in equipment operation and maintenance. This degradation is not sudden, but rather a physical and chemical evolution process from the inside out.

Aging Causes of the Valve Plate Microstructure

As the core of a nonlinear resistor, the valve plate's conductivity mechanism relies on the layered structure on the surface of zinc oxide grains. Under long-term power frequency voltage, this structure undergoes subtle but continuous changes:

• Imbalance in grain boundary potential distribution: Operating voltage gradually lowers the potential barrier height at grain boundaries.

• Slow increase in resistive current: Increased leakage current leads to heat accumulation inside the valve plate.

• Thermal stress induces microcracks: Cyclic heating and cooling cause damage to the ceramic body that is invisible to the naked eye.

External Environment's Contribution to Degradation

Besides the internal factor of the 11kv lightning arrester valve plate's performance degradation, moisture absorption due to seal failure is a fatal flaw. When moisture enters the porcelain bushing and adheres to the sides of the valve plate, it alters the originally uniform electric field distribution. Charge concentrates in the damp areas, leading to partial discharge, which directly accelerates the performance degradation of the zinc oxide material.

During inspections, if you observe significant abnormal heating on the 15kv lightning arrester surface or abrupt jumps in the online monitoring data, this usually indicates the valve plate is emitting a signal. Once this degradation crosses a critical point, the valve plate loses its non-linear characteristics, potentially causing the porcelain bushing to burst.

Regularly conducting DC reference voltage tests and leakage current detection are common methods for assessing the valve plate's health. By comparing the data, maintenance personnel can clearly determine whether the lightning arrester in transformer has entered its performance degradation phase, allowing for equipment replacement before any risks materialize.