Maximum Continuous Operating Voltage And Lightning Current Of Surge Protector
surge protective device (SPD) Maximum Continuous Operating Voltage Uc
The maximum RMS voltage or DC voltage that may be continuously applied across the SPD is equal to the rated voltage of the SPD itself.
IEC stipulates that in TT systems, when the SPD is installed on the source side of a residual current device (RCD), Uc ≥ 1.1Uo; when the SPD is installed on the load side of the residual current device (RCD), Uc ≥ 1.5Uo.
In TN and IT systems, Uc ≥ 1.1Uo. The selection of Uc should take into account the fluctuations in the local power grid and the specific power consumption of the user. A high value is not always the best. A high Uc will also increase the starting voltage of the varistor, and surge voltage will harm the equipment. International standards have a series of preferred values that are related to the local power grid level.
surge protector (SPD) Lightning Current Imax
Typically, an SPD with a 10/350µs waveform and a current flow of ≥10kA per phase is installed at the junction of LPZ0 and LPZ1. An SPD with an 8/20µs waveform and a current flow of ≥5kA per phase is installed at the junction of LPZ1 and LPZ2. Because the energy of a 10/350µs waveform is 20 times greater than that of an 8/20µs waveform, its current is correspondingly 5 times greater. Therefore, if an SPD with an 8/20µs waveform is used instead, the lightning current of surge protection device will be 5 times greater.
