How to discharge a medium voltage circuit breaker

Discharging a medium voltage circuit breaker is a critical process that requires careful planning, execution, and safety precautions to ensure the breaker is safely returned to service. Here's a step-by-step guide on how to discharge a medium voltage circuit breaker:

Preparation

  1. Ensure the breaker is de-energized: Verify that the breaker is in the open position and the circuit is de-energized. Use a voltage tester or a multimeter to confirm the absence of voltage.
  2. Identify the discharge method: Determine the type of discharge method required for your breaker. Common methods include:
    • Manual discharge: Using a discharge tool or a screwdriver to manually discharge the breaker.
    • Automatic discharge: Using a discharge device, such as a discharge resistor or a discharge capacitor, to automatically discharge the breaker.
  3. Wear personal protective equipment (PPE): Wear appropriate PPE, including gloves, safety glasses, and a face shield, to protect yourself from electrical shock and arc flash.
  4. Ensure a safe working environment: Ensure the work area is clear of any obstacles, and the floor is dry and non-conductive.

Manual Discharge Method

  1. Locate the discharge terminal: Identify the discharge terminal on the breaker, usually marked with a "D" or "DISCH" label.
  2. Use a discharge tool or screwdriver: Use a discharge tool or a screwdriver to manually discharge the breaker. The tool should be designed specifically for this purpose and should be rated for the voltage and current of the breaker.
  3. Insert the tool: Carefully insert the discharge tool or screwdriver into the discharge terminal and ensure it is securely seated.
  4. Discharge the breaker: Slowly and carefully discharge the breaker by turning the tool clockwise or counterclockwise, depending on the breaker's design.
  5. Verify the discharge: Use a voltage tester or a multimeter to verify that the breaker is fully discharged.

Automatic Discharge Method

  1. Connect the discharge device: Connect the discharge device, such as a discharge resistor or a discharge capacitor, to the breaker's discharge terminal.
  2. Set the discharge time: Set the discharge time according to the manufacturer's instructions or the breaker's specifications.
  3. Start the discharge: Start the discharge process by closing the breaker or activating the discharge device.
  4. Verify the discharge: Use a voltage tester or a multimeter to verify that the breaker is fully discharged.

Post-Discharge Procedures

  1. Verify the breaker is fully discharged: Use a voltage tester or a multimeter to verify that the breaker is fully discharged.
  2. Check the breaker's operating mechanism: Check the breaker's operating mechanism to ensure it is functioning properly.
  3. Return the breaker to service: Once the breaker is fully discharged, you can return it to service.

Important Safety Considerations

  1. Always follow the manufacturer's instructions: Follow the manufacturer's instructions for discharging the breaker, as the process may vary depending on the breaker's design and specifications.
  2. Ensure the breaker is de-energized: Verify that the breaker is de-energized before attempting to discharge it.
  3. Use appropriate PPE: Wear appropriate PPE to protect yourself from electrical shock and arc flash.
  4. Work in a safe environment: Ensure the work area is clear of any obstacles and the floor is dry and non-conductive.

Remember to always follow the manufacturer's instructions and take necessary safety precautions when discharging a medium voltage circuit breaker. If you are unsure about the process or feel uncomfortable performing the discharge, consult a qualified electrician or the breaker's manufacturer.