In order to meet the energy tolerance requirements of information system equipment, SPD installation can be multi-staged. The energy coordination between SPDs should be considered when multi-stage matching is carried out. When there is freewheeling, the decoupling device should be connected in series in the line. When conditions permit, it is advisable to use similar products of the same manufacturer, and require manufacturers to provide installation distance requirements between their products at all levels.
When accurate data cannot be obtained, the decoupling device should be connected in series when the line length between the voltage switch type and the voltage limiting type SPD is less than 10 meters and the line length between the voltage limiting type SPD is less than 5 meters. In the same power supply system, when the protection voltage level of the SPD installed at the starting point of the power supply device is Up ≤ 50% of the withstand voltage level of the end protected device, only the primary surge protector can be installed.