Advantages of Oil Circuit Breaker (OCB)
As an Arc extinguishing medium oil has the following advantages:
1. Oil produces hydrogen during arching. The hydrogen helps extinguish the arc.
2. The oil provides insulation for the live exposed contacts from the earthed portions of the container
3. Oil provides insulation between the contacts after the arc has been extinguished

Disadvantages of Oil Circuit Breaker (OCB)
1. Oil is inflammable and may cause fire hazards. When a defective circuit breaker fails under pressure, it may cause an explosion
2. The hydrogen generated during arcing, when combined with air, may form an explosive mixture
3. During arcing, oil decomposes and becomes polluted by carbon particles, which reduces its dielectric strength. Hence, it requires periodic maintenance and replacement.

Ref:
Electrical Equipment Handbook: Troubleshooting and Maintenance By Philip Kiameh



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