Surge Protective Device (spd) Selection Steps - Professional Technical Detailed Explanation
When selecting a surge protector (SPD), it is necessary to select it according to comprehensive factors such as the performance characteristics of the protection equipment, the application environment, and the installation location.
The first step is to select the maximum continuous working voltage (UC), short-time overvoltage (UT), nominal discharge current (In), and maximum discharge current (Imax) of the surge protective device. The maximum continuous working voltage of the surge protection device is much larger than the maximum continuous working voltage of the power system, and the transient overvoltage of the surge protector is much larger than the transient overvoltage of the power grid.
The second step is to determine the protection distance, that is, to determine the installation location of the surge protector. Under normal circumstances, the surge protector needs to be installed at the junction of each lightning protection zone, but due to the influence of environmental factors and the installation location of the protected equipment, it is generally installed at the front end of the protected equipment, in parallel or series, according to the product manual.
The third step is to expect the life and failure mode of the surge protector. The maximum service life of the surge protector is 5 years, and each product has a failure indication.
The fourth step is the relationship between the surge protector (SPD) and other electrical devices. Under normal circumstances, Ic will not cause any personal safety hazards or damage other equipment; in the event of a fault, the surge protector (SPD) will not affect other electrical appliances, such as RCD or circuit breakers. The surge coordination between the surge protector and the overcurrent protector is that when it is less than the maximum discharge current (Imax), the overcurrent protector does not operate; when it is greater than or equal to the maximum discharge current (Imax), the overcurrent protector is allowed to operate, but it cannot cause any damage.
The fifth step, the selection of the voltage protection level (Up), should consider the surge withstand capability (Uw) of the protected equipment.
The sixth step, the selection of the surge protector (SPD) When two surge protectors (SPD) are used on the same conductor, the coordination of the selected surge protector and other surge protectors should be considered.
The use of surge protectors in different grounding methods is different. On the one hand, because the protection characteristics are different under different grounding methods, the installation locations are different; on the other hand, the surge protector and the leakage protection device work together to avoid the current when the surge protector is activated may cause the upper leakage protection device to malfunction at the same time. Therefore, when the surge protector is installed, it is necessary to install corresponding protection equipment at the upper level, such as circuit breakers or fuses.
