The circuit breaker can be considered to be one of the most useful products within the electrical industry. It allows for the protection of electrical circuits from being damaged by short circuiting or current overload, while providing the option of an easy reset so that they do not need to be replaced each and every time. Since their invention, innovation has resulted in numerous types of circuit breakers that each serve a unique purpose.
One of these is the air circuit breaker. It is unique in that it is powered by air at atmospheric pressure and is used in applications where voltage up to 15 KV is handled. It moistens the air by using an air-blast, and has an advantage in that it does not need to use flammable liquids such as oil.
For the most part, air circuit breakers are subject to the same maintenance procedures and schedules as other types of circuit breakers. The purpose of performing maintenance is to identify current problems and prevent future ones from occurring.
Before diving in, it is important to mention that all the power going to the circuit breaker needs to be shut off completely before you begin any maintenance work. Only when the circuit breaker has been put back together again may you turn the power on again.
To begin, there should be a thorough inspection of any parts that are broken, damaged through excessive wear, significantly aged or missing. Temperature, corrosion. They must either be repaired or replaced immediately.
The next step is to examine the main contacts of the circuit breaker. Seeing as they make and break the current, they should be examined first. They must be properly cleaned out with silver cleaner or alcohol using cloths that are non-abrasive. You should look for signs of wear, especially if the circuit breaker has been subject to several short-circuit currents prior to your visit. Worn out contacts can contribute to an unusual rise in temperature during the operation of the circuit breaker that can prove to be dangerous. The contacts must be properly aligned and the spring pressures should fall within the boundaries dictated by the manufacturer.
The arc chutes must then be inspected for any dirt or moisture. There may be some black coloration on the arc chutes’ fins, which is normal and acceptable as long as they are not damaged. This part of the maintenance process primarily involves cleaning and inspecting for any damages that have occurred since the last inspection. Do not use wire brushes or emery cloth as you will end up leaving conductive residue that compromises the function of the arc chutes. Light sanding would be the best option for removing any dirt present, and a vacuum cleaner would be sufficient for dust removal. Without a properly functioning arc chute, the short circuit may not be fully cleared and the circuit breaker will be destroyed.
You should then inspect the operating mechanism that is composed of the device and chassis mechanisms. They should be clean is a whistle with all of the screws and bolts being secured properly. Additionally, you want to make sure that there is a sufficient amount of lubrication as stated by the manufacturer’s specifications – a lack of lubrication or an excessive amount will damage the longevity of the circuit breaker.
However, there are also some special steps that need to be taken for air circuit breakers. Because air is being compressed, it is important that there are no air leakages present and they must be plugged as soon as they are found. Any oil leakages found within the grading capacitors need to be checked on a monthly basis and the dew point of the operating air located within the air dryer’s outlet should be measured to see if it falls within the necessary limits.
When all of this is said and done, you should perform the necessary electrical and functional tests on the air circuit breaker. There are several parts to the testing phase, but the key things to ensure are the flawless functioning of the operating mechanisms and that the insulation resistance tests are performed. Tests for instant tripping and overcurrent should also be conducted.
The final step is to re-assemble the circuit breaker back to its original appearance and create a brief report on how the maintenance process went. This provides safety inspectors with a clear record on the maintenance performed while ensuring that the necessary steps for fixing or replacing parts within the air circuit breaker are carried out in a timely fashion.