Oil circuit breaker

An oil circuit breaker (OCB) is a type of electrical circuit breaker that uses oil as the arc-quenching medium to interrupt electrical currents. OCBs are commonly used in medium-voltage power systems, typically up to 36 kV, and are designed to provide reliable and safe switching of electrical circuits.

Here's how an OCB works:

  1. When the circuit breaker is operated, the moving contacts (called the "moving contact" or "MC") separate, creating an arc between them.
  2. The arc is sustained by the electrical current flowing through it, and it can be quite hot, reaching temperatures of up to 30,000°C (54,000°F).
  3. The oil surrounding the arc quenches the arc by rapidly cooling it, thereby extinguishing the arc.
  4. The oil also helps to dissipate the heat generated by the arc, reducing the risk of damage to the breaker or surrounding equipment.
  5. Once the arc is extinguished, the moving contacts can be safely closed again, and the circuit can be re-established.

OCBs have several advantages, including:

  1. High interrupting capacity: OCBs can interrupt high currents and voltages, making them suitable for use in medium-voltage power systems.
  2. Low maintenance: OCBs require minimal maintenance, as the oil helps to keep the contacts clean and free of debris.
  3. High reliability: OCBs are designed to operate reliably in a wide range of environmental conditions, including extreme temperatures and humidity.
  4. Low cost: OCBs are generally less expensive than other types of circuit breakers, such as vacuum circuit breakers (VCBs) or gas-insulated switchgear (GIS).

However, OCBs also have some disadvantages, including:

  1. Limited lifespan: OCBs have a limited lifespan, typically around 20-30 years, due to the degradation of the oil over time.
  2. Oil leakage: OCBs can leak oil, which can be a environmental concern and require regular maintenance to prevent.
  3. Limited flexibility: OCBs are typically designed for specific voltage and current ratings, making them less flexible than other types of circuit breakers.

Overall, OCBs are a reliable and cost-effective option for medium-voltage power systems, but they may not be suitable for all applications due to their limitations.