In addition, over current relay/ trip units can be Secondary Injection Tested using the appropriate test equipment for each brand of equipment to ensure that tripping parameters are still within manufacturer’s tolerances and that the unit will perform as designed and protect site assets/ systems.
In addition to the maintenance of ACB’s, we can carry out similar inspections and tests on Moulded Case Circuit Breakers (MCCB) to ensure correct tripping characteristics and performance.
The individual programme agreed upon, might include a full invasive inspection and physical maintenance of the whole primary and secondary panel arrangement under a controlled shutdown process. As an additional check, we can undertake a thermographic survey of the switchgear, under full load, to ensure that there is no overheating of components or connections.

 

Air circuit breakers (ACBs) are critical components in electrical distribution systems, responsible for protecting circuits from overloads and short circuits. Regular testing of air circuit breakers is essential to ensure their proper functioning and reliability. Here are some key aspects of METs air circuit breaker testing:

1. Visual Inspection:

   • Conduct a visual inspection of the circuit breaker for any signs of physical damage, corrosion, loose connections, or overheating.

   • Check for proper alignment and operation of mechanical linkages and moving parts.

2. Contact Resistance Test:

   • Perform a contact resistance test to ensure that the electrical contacts within the circuit breaker have low resistance, minimizing power losses and ensuring efficient current interruption.

   • High contact resistance can lead to overheating and decreased performance.

3. Insulation Resistance Test:

   • Conduct an insulation resistance test to verify the insulation integrity of the circuit breaker. This test helps identify any insulation breakdown or contamination.

   • Ensure that the insulation resistance meets the specified requirements.

4. Overcurrent Protection Testing:

   • Test the overcurrent protection features of the circuit breaker to verify that it trips within the specified time under overload and short circuit conditions.

   • Use a test kit to simulate various fault conditions and check the response of the circuit breaker.

5. Trip Unit Calibration:

   • If the air circuit breaker has an electronic trip unit, calibrate it to ensure that it operates within the specified parameters.

   • Verify that the trip unit settings align with the protection requirements of the connected electrical system.

6. Secondary Injection Testing:

   • Perform secondary injection testing on the trip unit to simulate the operation of protective relays and ensure coordination with other protective devices in the system.

   • This helps validate the correct functioning of the protection scheme.

7. Closing and Opening Time Measurement:

   • Measure the closing and opening times of the circuit breaker to ensure that it operates within the specified time limits.

   • Incorrect operating times can affect the coordination of protection devices in the system.

8. Mechanical Operation Test:

   • Conduct a mechanical operation test to ensure smooth and proper functioning of the operating mechanism.

   • Verify that the breaker can be manually closed and opened without any issues.

9. Dielectric Strength Test:

   • Perform a dielectric strength test to check the insulation properties of the circuit breaker under high voltage conditions.

   • This test ensures that the insulation can withstand the voltage stress without breakdown.