Protection of Medium Voltage and Low Voltage Networks Against Lightning Part 2: Lightning protection of Medium Voltage networks

Overvoltages due to direct and indirect lightning events depend on several factors and are characterized by complex wave shapes. For this reason numerical codes have been developed, aiming at the evaluation of the lightning overvoltages on realistic distribution line configurations. These tools are of fundamental help in the protection scheme design and the insulation coordination of actual distribution systems, as well as in evaluating the overvoltages transferred through distribution transformers to the low voltage part of the system. The basic information for designers of lightning protection of MV and LV networks has been presented in the part 1 of this guide. This second part presents an application of the basic information to the lightning protection of MV networks containing overhead lines3. This part of the guide applies primarily to MV networks with system voltage in the range from 1 kV to 36 kV. It is relevant for higher system voltages as well, but it becomes gradually less relevant when the system voltage increases. It is thus not possible to specify an upper limit for the system voltage, but the guide should not be used for system voltages above 50 kV