Operation and Maintenance of Surge Arresters

During routine operation, the contamination status of the surge arrester's porcelain housing surface should be inspected. This is because severe contamination on the porcelain surface leads to a highly uneven voltage distribution. In surge arresters equipped with parallel shunt resistors, an increase in voltage distribution across a specific internal element causes a significant surge in the current flowing through its associated parallel resistor; this may result in the burnout of the parallel resistor and subsequently trigger a fault. Furthermore, such contamination may compromise the arc-extinguishing performance of valve-type surge arresters. Consequently, if the porcelain surface of a surge arrester becomes heavily contaminated, it must be cleaned promptly.

Inspect the surge arrester's lead wires and grounding down-conductors for any signs of scorching or broken strands; also, check the discharge counter to determine if it has been damaged by excessive current. Such inspections are the most effective means of detecting latent defects within the surge arrester. Verify the integrity of the seal at the upper lead connection; a compromised seal allows moisture ingress, which can easily precipitate an electrical accident. Therefore, examine the cement joints connecting the porcelain housing to the flange to ensure they are watertight. For 10 kV valve-type surge arresters, a waterproof cover may be installed over the upper lead connection to prevent rainwater infiltration. Verify that the electrical clearance between the surge arrester and the protected electrical equipment meets the required specifications; ideally, the surge arrester should be positioned as close as possible to the equipment it protects. Following a thunderstorm, check the discharge counter to confirm its operational status. Monitor the leakage current; if the power-frequency discharge voltage deviates significantly-either above or below-the standard reference value, the unit should undergo maintenance and testing. If the discharge counter indicates an excessive number of operations, maintenance is required. Maintenance is also mandatory if cracks are detected in the porcelain housing or cement joints, or if the flange plate or rubber gasket has become dislodged.

The insulation resistance of the surge arrester should be checked periodically. Measurements should be taken using a 2500-volt insulation tester (megohmmeter). The measured values ​​should be compared against the results from the previous inspection; if there are no significant deviations, the unit may remain in service. A significant drop in insulation resistance is typically caused by moisture ingress resulting from a faulty seal, or by a short circuit across the internal spark gaps; if the resistance falls below the acceptable threshold, a comprehensive characteristic test must be performed. Conversely, a significant increase in insulation resistance is generally attributable to poor contact or breakage within the internal parallel resistors, slackening of internal springs, or the physical separation of internal components. To ensure the timely detection of latent internal defects in valve-type lightning arresters, a preventive test should be conducted annually prior to the thunderstorm season.