OIL CIRCUIT BREAKERS
Oil circuit breakers are the oldest type of circuit breakers. Oil circuit breakers are usually employed for high voltage applications up to 11kV with a current rating of up to 2400A. In this design, the main contacts are immersed in oil and the oil acts as the ionizing medium between the contacts. The oil is mineral type, with high dielectric strength to withstand the voltage across the contacts under normal conditions.
Oil has the following advantages:
Oil circuit breakers maybe of various types, but regardless of that the basic arc extinction process remains same in all circuit breakers. When main contacts are separated during the operation of the circuit breakers an arc will be produced. The arc will thus generate heat decomposing the oil around the main contacts and liberate gases (mostly hydrogen). The production of the hydrogen gas in this manner appreciably increases the dielectric strength of the gap between the contacts which aids in the arc extinction process.
Depending upon the amount of oil to be used oil circuit breakers may be classified into the following two types:
1)Bulk Oil Circuit Breaker
2)Minimum Oil Circuit Breakers
In the initial stages, the use of high-volume (bulk) oil circuit breakers was more common. In this type, the whole breaker unit is immersed in the oil. This type had the disadvantage of production
of higher hydrogen quantities during arcing and higher maintenance requirements. Subsequently these were replaced with low oil (minimum oil) types, where the arc and the bubble are confined into a smaller chamber, minimizing the size of the unit.
1 ) BULK TYPE OIL CIRCUIT BREAKERS
In bulk type oil circuit breakers a large amount of oil is used. The oil is required in large amount as it performs the following functions:
a)Production of hydrogen gas for arc extinction
b)Insulation between the open contacts
c)Insulation of line contacts form earthed metal tank.
Oil circuit breakers are the oldest type of circuit breakers. Oil circuit breakers are usually employed for high voltage applications up to 11kV with a current rating of up to 2400A. In this design, the main contacts are immersed in oil and the oil acts as the ionizing medium between the contacts. The oil is mineral type, with high dielectric strength to withstand the voltage across the contacts under normal conditions.
Oil has the following advantages:
- they have ability of cooling oil to flow into the space after current zero and arc goes out
- oil presents the cooling surface.
- energy absorption by decomposition of oil
Oil circuit breakers maybe of various types, but regardless of that the basic arc extinction process remains same in all circuit breakers. When main contacts are separated during the operation of the circuit breakers an arc will be produced. The arc will thus generate heat decomposing the oil around the main contacts and liberate gases (mostly hydrogen). The production of the hydrogen gas in this manner appreciably increases the dielectric strength of the gap between the contacts which aids in the arc extinction process.
Depending upon the amount of oil to be used oil circuit breakers may be classified into the following two types:
1)Bulk Oil Circuit Breaker
2)Minimum Oil Circuit Breakers
In the initial stages, the use of high-volume (bulk) oil circuit breakers was more common. In this type, the whole breaker unit is immersed in the oil. This type had the disadvantage of production
of higher hydrogen quantities during arcing and higher maintenance requirements. Subsequently these were replaced with low oil (minimum oil) types, where the arc and the bubble are confined into a smaller chamber, minimizing the size of the unit.
1 ) BULK TYPE OIL CIRCUIT BREAKERS
In bulk type oil circuit breakers a large amount of oil is used. The oil is required in large amount as it performs the following functions:
a)Production of hydrogen gas for arc extinction
b)Insulation between the open contacts
c)Insulation of line contacts form earthed metal tank.
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