SPD has limited life. The performance of SPD internal electronic components, such as gas discharge tube, varistor, transient suppression diode, diode, etc., will be affected when it discharges surge current. If SPD discharges too many times of surge current, it will cause performance degradation. In addition, due to the influence of temperature and humidity, the performance of components will gradually degrade. According IEC 61508-2 2010, 18.104.22.168, the useful lifetime lies within a range of 8 to 12 years. It can, however, be significantly less if elements are operated near their specification limits. For example, in outdoor high temperature and high humidity conditions, the expected lifetime of SPD is 3-5 years. If the system voltage is close to the maximum continuous working voltage of SPD, or overvoltage occurs frequently, the lifetime of SPD will be even shorter.
SPD shall be replaced regularly according to site conditions (thunderstorm days, temperature and humidity, power supply voltage quality and other factors). For example, it is recommended to replace SPD in 3-5 years in places where there are many thunderstorm days and the environment is bad. For places where there are few thunderstorm days, the environment is good and the power supply quality is good, SPD can be replaced in 5-8 years.
For SPD with status indication, if the indicated SPD fails, it shall be replaced immediately. In addition, SPD can be test by special equipments. We can also install online lightning monitoring system to monitor SPD status in real time and evaluate according to the environment and lightning impulse.