making a 25-square-millimeter wire joint in the power distribution cabinet

When making a 25-square-millimeter wire joint in the power distribution cabinet, it is necessary to ensure a firm connection, good electrical conductivity, and reliable insulation. The following are the detailed steps and precautions:

 I. Preparation of Tools and Materials

1. **Tools**:

   - Crimping pliers (matching the 25-square-millimeter crimping sleeve)

   - Wire strippers (the wire stripping length is about 30-40mm)

   - Insulating tape or heat shrink tubing

   - Sandpaper or copper wire brush (for cleaning the wire)

   - Multimeter (for testing conductivity)

2. **Materials**:

   - 25-square-millimeter copper/aluminum crimping sleeve (the same material as the wire)

   - Copper-aluminum transition joint (if the wire materials are different)

   - Insulating tape or heat shrink tubing

# II. Operation Steps

1. **Removing the Insulation Layer**:

   - Use wire strippers to remove the insulation layer at both ends of the wire, with a length about half of the length of the crimping sleeve (usually 30-40mm).

   - Note: Avoid damaging the core wire.

2. **Cleaning the Wire**:

   - Use sandpaper or a copper wire brush to remove the oxide layer on the surface of the wire to ensure good contact.

3. **Inserting the Crimping Sleeve**:

   - Insert the two wires into both ends of the crimping sleeve respectively, ensuring that the core wires fully enter the crimping sleeve and the exposed lengths at both ends are equal.

4. **Crimping Operation**:

   - Use crimping pliers to apply uniform pressure at the crimping mark positions of the crimping sleeve (usually there are 2-3 crimping points), crimping each point 2-3 times.

   - Ensure that there are no cracks in the crimping sleeve after crimping and that the core wire is not exposed.

5. **Insulation Treatment**:

   - Tightly wind the joint with insulating tape, covering at least 2-3cm on both sides of the crimping sleeve.

   - Or use heat shrink tubing (wrap the joint after heating and shrinking) to improve moisture resistance.

6. **Testing and Fixing**:

   - Use a multimeter to measure the resistance of the joint, which should be similar to the resistance of the wire itself.

   - Fix the joint in the power distribution cabinet to avoid being pulled by force.

 III. Precautions

1. **Material Matching**:

   - For copper core wires, use copper crimping sleeves, and for aluminum core wires, use aluminum crimping sleeves. Avoid direct contact between copper and aluminum (which is prone to oxidation).

2. **Safe Operation**:

   - Disconnect the power supply before operation and wear insulating gloves.

   - When crimping, keep your hands away from the crimping part to prevent pinching injuries.

3. **Specification Requirements**:

   - The joint should be kept away from high-temperature and humid environments and maintain good ventilation.

   - It is recommended to be operated by a licensed electrician and comply with the Code for Design of Low-Voltage Power Distribution (GB 50054).

 IV. Handling of Common Problems

- **Loose Crimping**: Recheck the crimping position to ensure that the specification of the crimping pliers is correct.

- **Insulation Damage**: Replace with new insulating tape or heat shrink tubing.

- **High Contact Resistance**: Clean the wire or replace the crimping sleeve.

If you encounter difficulties in operation, it is recommended to contact a professional electrician for handling to ensure electrical safety.