What should I pay attention to when installing the power distribution cabinet?

The installation of power distribution cabinet is a key link in electrical construction, and it is necessary to strictly follow safety specifications and technical standards to ensure the stable operation of power system. The following are the core items that should be paid attention to during installation:

First, preparation before installation

Environmental inspection

Ensure that the installation location is dry and well ventilated, away from high temperature, humidity, dust and corrosive gas environment (such as caution near boiler room and bathroom).

The ground shall be flat, and the height of foundation steel or bracket shall meet the design requirements, so as to avoid water soaking the cabinet.

Check whether the positions and sizes of reserved holes and embedded parts in civil works match the distribution cabinet.

equipment inspection

Check whether the model, specification and quantity of the power distribution cabinet are consistent with the design drawings, and the accessories (such as door locks, instruments and switches) are complete and undamaged.

Check whether there is deformation and corrosion on the surface of the cabinet, the cabinet door can be opened and closed flexibly, the internal electrical components are fixed firmly, and the wiring terminals are not loose.

Testing insulation resistance: measure insulation resistance between phases and ground with a 500V megohmmeter, which should be no less than 2MΩ (the standard should be improved in wet environment).

Second, the key points of the installation process

1. Installation of foundation steel

The foundation is made of galvanized angle steel or channel steel, with levelness error ≤1mm/m and total length ≤ 5 mm; Perpendicular error ≤ 1.5 mm/m.

The foundation steel shall be reliably grounded (at least two places shall be connected with the grounding trunk line), and the grounding resistance shall be ≤4Ω.

The foundation steel can be fixed to the ground by expansion bolts or welding, and the welding place needs anti-corrosion treatment (anti-rust paint and topcoat).

2. Installation of cabinet body

Fixed mode:

Small-sized distribution cabinets (light weight) can be directly fixed on the wall or ground with expansion bolts.

Large-scale power distribution cabinets need to install basic section steel first, and then connect or weld the cabinet body with the section steel by bolts (pay attention to protect the paint surface of the cabinet body when welding).

Arrangement requirements:

When multiple cabinets are installed in parallel, the horizontal deviation at the top is ≤2mm, the lateral flatness deviation is ≤3mm, and the gap between cabinets is ≤2mm.

When installed in columns, the verticality error shall be ≤1.5‰, the flatness deviation of the disk surface shall be ≤5mm, and the arrangement shall be neat and beautiful.

Safe distance:

Width of front operation channel of power distribution cabinet: single row layout ≥1.5m, double row layout ≥2m.

The width of the back maintenance channel: ≥0.8m (≥0.6m in case of difficulty), and the side is ≥0.5m away from the wall.

3. Electrical connection

Wire selection:

The phase line, neutral line and protective ground line (PE line) should be clearly separated (phase line: yellow/green/red; Zero line: light blue; PE line: yellow and green).

The cross-sectional area of the conductor meets the design requirements, and the cross-sectional area of the copper conductor is ≥ 1.5 mm, and the aluminum conductor is ≥ 2.5 mm (the specification needs to be increased when the current is large).

Wiring process:

Wires and terminals are firmly connected, the crimping terminals need to match the wire diameter, and multi-strand wires need to be tinned or cold-pressed terminals are used.

Inlet and outlet holes should be sealed (such as with fireproof mud or rubber sealing ring) to avoid the intrusion of small animals or dust.

The PE line shall be provided with a separate grounding terminal block, which shall not be mixed with the neutral line; The metal frame, doors and supports of the cabinet shall be reliably grounded.

4. Functional testing

Check again whether the wiring is correct, short circuit and grounding fault before electrifying.

Test the on-off function of each switch, whether the action of circuit breaker and leakage protector is sensitive and reliable (it can pass the simulated fault current test).

Check that the instrument and indicator light display normally, which is consistent with the actual operation state.

Third, the safety and specification requirements

ground protection

The power distribution cabinet must be reliably grounded, and the grounding resistance of PE line should meet the design requirements (usually ≤4Ω). It is forbidden to use series grounding.

Openable doors with electrical appliances should be connected to the cabinet frame through soft copper wires to ensure grounding continuity.

Identification and warning

The front of the cabinet should be marked with the name and number of the circuit, and the switch function should be clearly marked (such as "lighting circuit" and "air conditioning circuit").

Safety warning signs such as "beware of electric shock" are posted on the cupboard door, and the keys are kept by special personnel.

Fire and explosion protection

Power distribution cabinets installed in flammable places (such as warehouses and kitchens) should be explosion-proof products and sealed.

Inlet and outlet holes shall be blocked with fireproof materials to avoid the spread of fire.

Fall prevention and earthquake prevention

The installation height of the suspended distribution cabinet shall conform to ergonomics (the lower edge is more than or equal to ≥1.3m from the ground), and the fixing bolts shall bear enough weight to avoid falling.

Vibration environment (such as equipment room) needs to be equipped with damping pads, and bolts should be treated with anti-loosening treatment (such as adding spring washers).

IV. Acceptance and debugging

Check whether the installation size, grounding resistance and insulation resistance conform to the specifications.

Simulate the test run, and observe whether the current and voltage of each loop are normal, and whether there is abnormal heat and noise.

Arrange installation records, test reports and other materials and hand them over to Party A for filing.

summary

Electrical safety, mechanical stability and convenient operation should be taken into account in the installation of power distribution cabinets, and standards such as Code for Acceptance of Construction Quality of Building Electrical Engineering (GB 50303) and Code for Design of Low-voltage Power Distribution (GB 50054) should be strictly followed. If complex systems are involved (such as intelligent power distribution cabinets and dual power supply switching), it is recommended to be operated by professional electricians or teams to ensure construction quality and safe operation.