DD IEC TS 62257-9-4-2007 pdf Recommendations for small renewable energy and hybrid systems for rural electrification – Part 9-4: Integrated system – – User installation

7 Protection against effect of lightning 7.1 Installation supplied from a microgrid The overvoltage protection, where necessary, is provided on the microgrid side. 7.2 Standalone installation If the distance between the external generator and the user’s installation is less than 15 m: no special measure is required. If the distance between the external generator and the user’s installation is greater than 15 m and the number of thunderstorm days per year (obtained from iso-keraunic maps) is high (generally more than 25 days per year), a conductor made of bare copper with a sectional area of at least 10 mm2 shall be installed between the external generator and the user’s installation. It shall be installed in the same ditch as the electrical cable (laid in a conduit) as close as possible to it. This creates an equipotential bonding system as shown in Figure 3. One of the ends shall be connected to the earthing electrode of the external generator and the other shall be connected to a special terminal provided for this purpose at the user’s installation. SPDs shall be installed between the two polarities and between each polarity and the earth at the two ends of the bonding conductor. For specific requirements for generators, refer to the appropriate parts of the IEC 62257-7 series.
8 Selection and erection of electrical equipment 8.1 Wiring system 8.1.1 General The number of subcircuits shall be determined according to the position of the consumption points, their nature and the foreseeable load. Separate neutral and protective conductors shall be provided for each subcircuit. The cross-sectional area of conductors is chosen to provide for a satisfactory lifetime of conductors and insulation subjected to the thermal effects of carrying current for prolonged periods of time in normal service (See tables in IEC 60364-5-52). Other considerations that affect the choice of cross . sectional area of conductors are: ●to fulfill maximum acceptable voltage drop, to withstand the electro-dynamic stresses which can occur in the event of a short-circuit, ●to withstand the other mechanical stresses to which the conductors may be subjected, to ensure an impedance value compatible with operation of the short-circuit protection devices. 8.1.2 Voltage drops The maximum voltage drops in the installation shall not be greater than those indicated in Table 2.