Grounding forms and basic requirements of low-voltage power distribution systems   In order to cooperate with lightning protection devices such as surge protection device  in low-voltage electrical systems to discharge lightning, the grounding in low-voltage power distribution systems must meet the following requirements:   1. The grounding forms of the low system can be divided into three types: TN, TT, and IT. Among them, the TN system can be divided into three types: TN-C, TN-S and TN-C-S.   2. The grounding form of the low-voltage power distribution system should be determined according to the specific requirements of the electrical safety protection of the system.   3. When the protective grounding and functional grounding share the same grounding conductor, the relevant requirements for the protective grounding conductor shall be met first.   4. Exposed conductive parts of electrical installations shall not be used as series transition contacts for protective earth conductors (PE).   5. The protective earth conductor (PE) shall meet the following requirements:   1.The protective earth conductor (PE) shall have appropriate protection against mechanical damage, chemical or electrochemical damage, electrodynamic and thermal effects, etc. 2. Protective electrical appliances and switching devices shall not be installed in the protective earth conductor (PE) circuit, but connection points that can only be disconnected with tools are allowed 3.When using electrical monitoring instruments for grounding detection, special components such as working sensors, coils, current transformers, etc. should not be connected in series in the protective grounding conductor.   4. When the copper conductor is connected to the aluminum conductor, a special connection device for copper and aluminum should be used.   6. The cross-sectional area of ​​the protective grounding conductor (PE) should meet the conditions for automatic power cut off after a short circuit, and can withstand the mechanical stress and thermal effects caused by the expected fault current within the cut-off time of the protective appliance.   7. The minimum cross-sectional area of ​​the separately laid protective earth conductor (PE) shall comply with the provisions of Article 7.4.5 of this standard.   8. The protective earth conductor (PE) may consist of one or more of the following conductors:   1.Conductors in multi-core cables 2.Insulated or bare conductors shared with live conductors 3.Bare or insulated conductors for fixed installations 4.Metal cable jackets and concentric conductor power cables that meet dynamic and thermally stable electrical continuity   9. The following metal parts shall not be used as protective earth conductors (PE):   1.Metal water pipe 2.Metal pipes containing gas, liquid, powder, etc. 3.Flexible or bendable metal conduit 4.Flexible metal parts 5. Support wire, cable tray, metal protective conduit

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Post time: Apr-28-2022