Circuit breaker in substation in Sri-Lanka

A circuit breaker in substation is a key component in electrical power systems, designed to interrupt the flow of electricity when a fault occurs, such as a short circuit or overload. Depending on system design, these devices can operate manually or automatically and come in various types, including air, vacuum, oil, and SF₆ gas.

For example, consider a substation feeding power to an industrial area. If a short circuit occurs on one of the distribution lines due to a tree branch falling on the line, the circuit breaker associated with that line must quickly detect the fault and interrupt the current.

It is responsible for disconnecting faulty parts of the grid while keeping the rest of the system running smoothly. Without these breakers, power failures could cascade through the system, leading to widespread blackouts.

Circuit breakers form part of a broader substation protection and control system that includes current transformers, voltage transformers, and digital protection relays. When a relay detects an abnormality, it sends a signal to the breaker to open, thereby isolating the faulty section.

Example: In a modern urban substation where space is limited, a hybrid circuit breaker might be used to protect the main incoming feeder. The hybrid design allows for compact installation while providing reliable fault protection and efficient arc quenching.

OCBs are used in high-voltage substations and have been popular in the past, although they are now being replaced by more modern technologies. Example: In a rural high-voltage substation serving a long transmission line, an OCB might be used to protect the line.