Zinc oxide arresters are widely used in power grids with voltage levels below 10KV, mainly as a common lightning protection device to prevent lightning waves from damaging electrical equipment in substations. They not only have excellent nonlinear volt-ampere characteristics, but also have low cost, no gaps, no follow current, large current capacity, and stable performance. However, breakdown and explosion accidents still occur from time to time.
Common faults are mainly caused by the following reasons:
Poor sealing
Cause analysis: Poor sealing of arresters mainly occurs during the production process. For example, the valve plates of the arrester are not thoroughly dried and contain moisture. Or during assembly, the sealing gasket of the arrester is improperly placed or even not installed. Some manufacturers use unqualified materials, such as poor-quality porcelain insulators with invisible small holes, which can also cause moisture to seep in and make the interior damp.
Preventive measures: To prevent poor sealing of arresters, users should conduct strict sealing tests before use. In addition, during the operation and maintenance of arresters, especially after thunderstorms, patrol inspections should be strengthened to promptly detect abnormal conditions. During regular preventive tests on arresters, test personnel should carefully analyze the test data. Because when an arrester is damp, there may be no visible problems on the outside, but only through test data can internal defects be discovered.
Aging of internal valve plates
Cause analysis: Aging of valve plates generally occurs during operation. Due to poor uniformity of the arrester valve plates, their aging degrees vary, resulting in uneven potential distribution among the valve plates. After a period of operation, some valve plates deteriorate first, causing an increase in leakage current and power loss of the arrester.
Since the grid voltage remains unchanged, the load on the remaining normal valve plates inside the arrester increases, accelerating their aging. This forms a vicious cycle, leading to internal breakdown of the arrester, causing single-phase grounding or explosion of the arrester body.
Another reason for accelerated aging of zinc oxide arrester valve plates is that the continuous operating voltage of the arrester is too low. This will greatly increase the load on the arrester during operation, especially when a single-phase ground fault occurs in the system, causing rapid aging of the valve plates.
Preventive measures: To address the aging of arrester valve plates, in addition to requiring manufacturers to improve production processes and enhance the uniformity of valve plates, it is also necessary to select arresters with sufficient rated voltage and continuous operating voltage during design and selection. In addition, during patrol inspections, not only should the appearance of the arrester be checked for damage, flashover, and other phenomena, but also the leakage current value of the arrester should be recorded and compared with the initial value. If the value is too large, the defect should be reported promptly and dealt with.
