Choice of Surge Protective Device
The selection of Surge Protective Device is carried out as follows.
Step 1: Select Uc, UT, In, Imax of Surge Protective Device. The maximum continuous operating voltage of the Surge Protective Device is much larger than that of the power system, and the transient overvoltage of the Surge Protective Device is much larger than that of the grid.
Step 2: Determine the protection distance, that is, determine the location of the Surge Protective Device.
Step 3: Anticipate the life and failure modes of the Surge Protective Device.
Step 4: Interrelationship between Surge Protective Device and other electrical appliances. Under normal circumstances, Ic will not cause any personal safety hazards and damage other equipment; when a fault occurs, Surge Protective Device will not affect other electrical appliances, such as RCD or circuit breaker. The surge coordination between the Surge Protective Device and the overcurrent protector, when it is less than Imax, the overcurrent protector does not operate; when it is greater than or equal to Imax, the overcurrent protector is allowed to operate, but it cannot cause any damage.
Step 5: The selection of voltage protection level Uₚ should consider the surge withstand capability Uw of the protected equipment.
Step 6: When two Surge Protective Devices are used on the same conductor, the cooperation between the selected Surge Protective Device and other Surge Protective Devices should be considered.
The use of Surge Protective Device is different in different grounding methods. On the one hand, because of the different characteristics of the protection under different grounding methods, the installation location is also different; on the other hand, the Surge Protective Device cooperates with the leakage protection device, in order to avoid the current when the Surge Protective Device operates may cause the leakage protection of the upper level at the same time The device malfunctions, so the Surge Protective Device needs to be installed with corresponding protection devices, such as circuit breakers or fuses, on its upper level during installation.
