A type of circuit breaker known as an oil circuit breaker is one that uses oil as the dielectric or insulating substance in order to extinguish electrical arcs. The contacts of an oil circuit breaker are made separate from the insulating oil in order to function properly. Because of the malfunction in the system, the circuit breaker’s contacts become exposed to the insulating oil when the fault occurs. As a result, an arc is created between the contacts, and the heat generated by the arc causes the surrounding oil to evaporate. The oil circuit breakers can be broken down into two distinct kinds.
The fabrication of an oil circuit breaker is a pretty simple process. It is made up of current conducting contacts that are sealed inside of a sturdy, airtight, earth metal tank. The tank is then filled by transformer oil. In addition to its role as an arc extinguishing medium, the oil also performs the function of an insulator between the live component and the earth. At the very top of the oil, the tank is filled with air, which works as a cushion to regulate the displaced oil on the development of gas surrounding the arc as well as to absorb the physical shock of the ascent of oil. Air is pumped into the tank until it reaches the very top of the oil. The breaker tank is welded together very firmly so that it can withstand the vibration that is created by cutting off very high current. The oil circuit breaker includes a gas outlet that is installed in the tank’s cover for the purpose of removing gases.
The contact of the oil to the circuit breaker will be closed and will carry the current when the operating circumstances are considered to be normal. The circuit breaker’s contacts will begin to move apart when the fault in the system occurs, which will result in an arc being struck across the contacts. Because of this arc, a significant quantity of heat is released, and an extremely high temperature is achieved, which converts the oil that is in the surrounding area into gas by vaporizing it. The gas that was released then encircled the arc, and its rapid expansion surrounding it severely displaced the oil that was there. When a distance between the fixed contact and the moving contact reaches a particular critical value, the arc is extinguished. This value depends upon the arc current and the recovery voltage.
The heat from the arc causes the oil to evaporate between the contacts, which then causes it to transform primarily into hydrogen gas. The gas condenses to form a bubble that encircles the contacts, and this bubble quickly grows in size. The oil is driven out of the way by the gas bubble, which is then absorbed by the atmosphere cushion. The gas bubble which de-ionizes the medium is compressed due to the surrounding oil’s presence. The medium in between the connections exhibits an increased dielectric strength as a result. The contact spacing also lengthens the arc, which contributes to an increase in the medium’s dielectric strength. When the current goes over a zero-crossing again, the arc is extinguished. The fact that a conventional break oil circuit breaker does not have an arc control and instead relies on contact separation, which results in a longer arc, is the most significant disadvantage of this type of breaker. It is not reliable and requires significantly longer arcing durations. When the points of contact are moved far enough apart, the arc will no longer continue. For low voltage 11kV circuits, a plain snap oil circuit breaker is typically utilized because of the constraints described above.
After the circuit breaker has been tripped by a short-circuit current, the contacts on the circuit breaker can often become scorched as a result of arcing. Additionally, the dielectric oil will become carbonized in the vicinity of the contacts, causing it to lose its strength as a dielectric. As a direct consequence of this, the breaker’s breaking capacity is diminished. As a result, it is necessary to perform routine maintenance on an oil circuit breaker, which includes monitoring the oil level and replacing any worn out contacts.