1. Arc Quenching Medium:

   • Air Circuit Breaker (ACB): ACBs use air as the arc quenching medium. When the circuit breaker interrupts the current flow, the arc produced between the contacts is extinguished by the surrounding air.
   • Oil Circuit Breaker (OCB): OCBs use oil as the arc quenching medium. The arc produced during circuit interruption is directed into a chamber filled with insulating oil, where it is rapidly cooled and extinguished.

2. Insulation:

   • Air Circuit Breaker (ACB): ACBs typically have solid insulation materials such as ceramics or composite materials to insulate the conductive parts from each other and from the surrounding environment.
   • Oil Circuit Breaker (OCB): OCBs use insulating oil not only as the arc quenching medium but also as insulation for the conductive parts. The oil provides additional insulation and helps dissipate heat generated during interruption.

3. Maintenance:

   • Air Circuit Breaker (ACB): ACBs generally require less maintenance compared to OCBs. They do not require periodic oil testing or refilling, and their components are easier to inspect and replace.
   • Oil Circuit Breaker (OCB): OCBs require regular maintenance, including oil testing, filtering, and sometimes oil replacement. The insulating oil needs to be monitored for degradation and contamination, and the oil level must be maintained within specified limits.

4. Environmental Impact:

   • Air Circuit Breaker (ACB): ACBs are more environmentally friendly than OCBs because they do not use oil, which can pose environmental hazards if leaked or improperly disposed of.
   • Oil Circuit Breaker (OCB): OCBs have a higher environmental impact due to the use of insulating oil, which can be toxic and harmful to the environment if released into the soil or water.

5. Application:

   • Air Circuit Breaker (ACB): ACBs are commonly used in indoor applications where space is limited and environmental concerns are important. They are suitable for low to medium voltage applications.
   • Oil Circuit Breaker (OCB): OCBs are typically used in high voltage applications, such as power generation and transmission facilities, where high interruption capacity and reliable performance are required.

Overall, both air circuit breakers and oil circuit breakers have their advantages and disadvantages, and the choice between them depends on factors such as the voltage level, application requirements, maintenance considerations, and environmental concerns.