What is Disconnector?
A disconnector (also known as an isolator) is often positioned between two circuit breakers in a substation under particular conditions to give visible isolation & safe maintenance access to equipment.
The following are the key conditions in which this arrangement is used:
1). Busbar Configuration
In double busbar (or) double breaker systems, a disconnector between two circuit breakers enables circuit switching or isolation for maintenance without disturbing the entire system. This design provides operational flexibility & redundancy.
2). Maintenance & Safety
When doing maintenance on a circuit breaker or substation section, the disconnector creates a visible break in circuit to ensure safety. Circuit breakers can halt current, yet they don’t leave a visible gap, thus disconnectors are employed.
3). Sectionalizing
In ring bus (or) breaker-and-a-half arrangements, disconnectors are installed between breakers to sectionalize the bus or isolate a portion of the system while keeping the rest operational.
4). Fail-safe Isolation
To isolate a malfunctioning circuit breaker from the rest of the system, place a disconnector across two breakers. This is particularly beneficial in sensitive installations if fault tolerance is required.
5). Redundancy in Protection
To ensure double redundancy, two breakers may be utilized for a single line (or) transformer, with a disconnector in between for controlled isolation without halting the entire load.
Disconnectors should only be used when the circuit is de-energized, as they are not meant to interrupt current and lack the arc-quenching capabilities of circuit breakers.