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MET Group Technical is a leader in the UK and Europe for non-invasive energised inspections and safe live operations.
ACB Testing & Maintenance
Air Circuit Breaker Maintenance, Testing & Repairs
A frequently overlooked aspect of electrical installations is the primary switchgear and isolation methods. In many setups, especially in larger facilities, the primary means of isolation and system protection is typically an 'Air Circuit Breaker,' a mechanical device that varies in design based on brand and age. This equipment can stay in the 'On' or 'Closed' position for extended periods, and without regular maintenance or activation, it may fail to function unexpectedly, leading to potentially serious consequences.
The switchgear, whether from ABB, Merlin Gerin, Schneider Electric, GEC, Mitsubishi, or other manufacturers, serves as the main isolation point and provides protection against faults or overcurrents in the system, thus ensuring the safety of the upstream system. A failure to function properly can result in severe repercussions.
MET Group's Air Circuit Breaker Service for Compliance and Reliability:
At MET Group, we offer comprehensive maintenance services for this primary breaker unit, as well as for secondary units and those further along the installation. We can create a customized maintenance program that aligns with existing routines, which may include main shutdowns, switch withdrawals, cleaning, re-torqueing (only during panel maintenance), lubrication (a crucial aspect of ACB maintenance), greasing, functional testing, contact servicing, and replacement of any worn or damaged parts.
Additionally, overcurrent relays and trip units can undergo Secondary Injection Testing with the appropriate testing equipment for each brand, ensuring that tripping parameters remain within the manufacturer's tolerances and that the unit functions as intended to protect site assets and systems. Alongside ACB maintenance, we can perform similar inspections and tests on Moulded Case Circuit Breakers (MCCB) to verify their tripping characteristics and performance. The agreed-upon program may include a comprehensive invasive inspection and physical maintenance of the entire primary and secondary panel setup during a controlled shutdown. As an extra precaution, we can conduct a thermographic survey of the switchgear under full load to check for any overheating of components or connections.
Air circuit breakers (ACBs) are vital in electrical distribution systems, safeguarding circuits from overloads and short circuits. Regular testing of ACBs is crucial for ensuring their reliability and proper functioning. Here are some essential elements of METs air circuit breaker testing:
Visual Inspection: Examine the circuit breaker for any signs of physical damage, corrosion, loose connections, or overheating, and ensure proper alignment and operation of mechanical linkages and moving parts.
Contact Resistance Test: Conduct a contact resistance test to confirm that the electrical contacts within the circuit breaker have low resistance, minimizing power losses and ensuring efficient current interruption, as high contact resistance can lead to overheating and reduced performance.
Insulation Resistance: Test: Perform an insulation resistance test to assess the integrity of the circuit breaker's insulation, identifying any breakdown or contamination, and ensure that the insulation resistance meets specified requirements.
Overcurrent Protection Testing: Test the overcurrent protection features of the circuit breaker to ensure it trips within the designated time during overload and short circuit conditions, using a test kit to simulate various fault scenarios.
Trip Unit Calibration: If the air circuit breaker has an electronic trip unit, calibrate it to ensure it operates within specified parameters and verify that the trip unit settings align with the protection needs of the connected electrical system.
Secondary Injection Testing: Carry out secondary injection testing on the trip unit to simulate protective relay operation and ensure coordination with other protective devices in the system, validating the protection scheme's functionality.
Closing and Opening Time Measurement: Measure the closing and opening times of the circuit breaker to ensure it operates within specified limits, as incorrect times can impact the coordination of protection devices.
Mechanical Operation Test: Conduct a mechanical operation test to ensure the operating mechanism functions smoothly and verify that the breaker can be manually closed and opened without issues.
Dielectric Strength Test: Perform a dielectric strength test to evaluate the insulation properties of the circuit breaker under high voltage conditions, ensuring the insulation can withstand voltage stress without failure.
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