Maintenance for low voltage circuit breakers

Low circuit breaker normally operating at 600 volt AC and below.The common used types of  circuit breaker around the world such as molded case circuit breaker (MCCB) and Air circuit breaker ( ACB ).

This low voltage circuit breaker usually used for power distribution and sub power distribution at factory and general industry.It a combination with electrical and mechanical device to protect our electrical system from overload and over current matters.

IEE regulation stated a several condition for maintenance and services for circuit breaker.The main purpose is to make sure this circuit breaker in good condition and can activated when problem happen.It also for safety purpose for equipment and personnel.

How long period for maintenance the low voltage circuit breakers?

Normally in all country over the world,period for maintenance the circuit breaker is every 1 to 3 years per one times.It should perform periodically services and it depending on the operating condition and their last service.

A low circuit breaker should be inspected and maintained if necessary whenever it has interrupted current at or near its rated capacity.Following listed are the conditions that make we should perform frequency maintenance and inspection such as :

•  High humidity and high ambient temperature.
•  Dusty or dirty atmosphere.
•  Corrosive atmosphere.
•  Frequent switching  matters.
•  Frequent fault or trip operations.
•  Age of equipment.

How to perform maintenance for low voltage circuit breakers?

Normally circuit breaker manufacturer’s gave a completed service manual and maintenance instructions.If they not provided the service manual,please contact the supplier to supply it and conduct training how to maintain and services.

The following below i would like to share based on my experience several procedures that should be followed in the maintenance of Air circuit breaker or molded case circuit breaker :

• An initial check of the breaker should be made in the TEST position prior to withdrawing it from to enclosure.
• Insulating parts, including bushings, should be wiped clean of dust and smoke.
• The alignment and condition of the mechanism contacts should be checked and adjusted according to the manufacturer’s instruction book.
• Check arc chutes condition and replaces any damaged parts.
• Inspect breaker operating mechanism for loose hardware and missing or broken cotter pins, etc. Examine cam, latch, and roller surfaces for damage or wear.
• Clean and lubricate operating mechanism with a light machine oil (SAE-20 or 30) for pins and bearings and with a non hardening grease for the wearing surfaces of cams, rollers, etc.
• Set breaker operating mechanism adjustments as described in the manufacturer’s instruction book. If these adjustments cannot be made within the specified tolerances, it may indicate excessive wear and the need for a complete overhaul.
• Replace contacts if badly worn or burned and check control device for freedom of operation.
• Perform insulation resistance tester for move and static contact