Long duration impulse withstand capability of SPD

In low voltage system, there are varity impulse happened with different peak value and time duration due to the lightning and equipment operation or faults. SPD is the main protective device withstanding those impulse, it is widely used in the low power system. However SPD's fault usually lead to big loss in using. Thence SPD's reliability is the focus element concerned by users. To improve the reliability of SPD in using is a very important subject in the field of manufacture and application.