Short Answer:

An isolator is a manually operated switch used in switchgear to completely disconnect a circuit from the system for safe maintenance. Unlike circuit breakers, isolators are not designed to operate under load and are used only when the current is already zero.

Their main purpose is to provide a visible break in the circuit to ensure the safety of maintenance personnel and prevent accidental energization of equipment during repair work.

Detailed Explanation:

Isolators and their purpose in switchgear

Isolators, also known as disconnect switches, are used in substations and switchgear panels to ensure electrical isolation of equipment or sections of the network. They are typically operated manually and are installed alongside circuit breakers.

Key features:

Operated only after the breaker has opened the circuit.
Cannot interrupt load or fault current.
Provide visible and physical disconnection.
Often equipped with interlocking to prevent unsafe operation.

Purposes in switchgear:

Safety during maintenance:
- Prevents accidental flow of electricity during repair or inspection.
Isolation of faulty sections:
- Allows safe work on transformers, feeders, or breakers.
Clear visual confirmation:
- Ensures that the line is open and de-energized.
Coordination with breakers:
- Used after circuit breakers open the load to maintain isolation.

Conclusion:

Isolators are safety devices used to disconnect parts of the system for inspection and repair. Though they do not interrupt current, they provide visible assurance of isolation, making them essential in switchgear for protection and safe maintenance.