Protective Earthing of Container Houses

Protective earthing of container houses is an important measure to prevent electric shock accidents and ensure personal safety. Its core is to reliably connect the metal box and the outer shell of electrical equipment to the ground through earthing devices, reducing the contact voltage and avoiding the risk of electric shock.

I. Necessity of Protective Earthing

1. Anti-Electric Shock Mechanism
   When the insulation of electrical equipment is damaged and the outer shell becomes electrified, if it is not grounded, a current path will be formed when a person touches the electrified outer shell, triggering an electric shock. After earthing, the fault current flows into the ground through the earthing wire. Since the earthing resistance is much smaller than the human body resistance, the current preferentially passes through the earthing device, significantly reducing the risk of electric shock. For example, in energy storage container houses, the earthing resistance needs to be controlled within 4Ω to ensure that the fault current is large enough to trigger the action of protective devices (such as circuit breakers).

2. Lightning Protection
   As a metal structure, container houses may become electrified due to electromagnetic induction or direct lightning strikes during thunderstorms if they are not grounded. Good earthing can form a Faraday cage effect, introducing the lightning current into the ground and protecting the internal personnel and equipment. For example, the building electrical lightning protection earthing system discharges the lightning current to the ground through earthing electrodes to prevent the box from becoming electrified.

II. Key Points for Implementing Protective Earthing

1. Selection of Earthing Devices

   • Earthing Electrodes: Vertical or horizontally arranged metal conductors (such as angle steel and steel pipes) can be used and buried underground to directly contact the ground. Natural earthing electrodes (such as building foundation steel bars and metal pipes) can also be utilized, but their conductivity and corrosion resistance need to be ensured.
   • Earthing Wires: Special yellow-green bicolored wires should be used to connect the outer shell of equipment to the earthing electrodes. The cross-sectional area of the wires needs to meet the requirements of the fault current. For example, in energy storage container houses, the cross-sectional area of the equipment earthing wires should be no less than 4mm², and the cross-sectional area of the main earthing wires should be no less than 250mm².

2. Equipotential Bonding
   In container houses, all metal components (such as anti-static floors, equipment outer shells, and pipes) need to be interconnected through copper bars or wires to form an equipotential body. This can eliminate the potential difference between different metal parts and avoid the risk of electric shock. For example, in energy storage container houses, a dedicated earthing copper bar needs to be laid inside to connect the equipment earthing terminals to the external earthing points of the box.

III. Earthing Requirements in Different Scenarios

1. Residential Container Houses
   It is necessary to refer to building electrical codes and set up lightning protection earthing and protective earthing. For example, the residential container houses produced by Wanzhong Container are equipped with standard lightning protection earthing interfaces and complete power-on tests before leaving the factory to ensure that the earthing resistance meets the requirements.

2. Energy Storage Container Houses
   It is necessary to strictly follow GB 50065—2011 Code for Design of Earthing of AC Electrical Installations, set up an independent earthing network, and connect it to the external main earthing network at a single point to avoid introducing potential differences into the box. At the same time, anti-static floors need to be laid, and the system resistance value should be controlled within 1×10⁶~1×10⁹Ω to prevent static electricity accumulation.

IV. Precautions

• Prohibition of Series Earthing: Each device should be grounded separately to avoid other devices becoming electrified due to the failure of one device.
• Regular Inspection: It is necessary to regularly check the earthing resistance and the connection status of the earthing wires to ensure their reliability.
• Avoidance of Multiple-Point Connections: The connection between the main earthing network and the box should adopt a single-point connection method to prevent potential differences from being introduced into the interior of the box.