Correct option is D
An isolator, also known as a disconnector, is a mechanical switch that is used to isolate a part of the circuit from the system for maintenance and safety purposes.
Isolators are used in electrical circuits to ensure that a section of the circuit is completely de-energized for service or maintenance.
Unlike circuit breakers, isolators do not have arc-extinguishing capabilities and are not designed to open a circuit under load.
They are operated only after the circuit has been opened by a circuit breaker.
An isolator, also known as a disconnector, is an essential component in electrical systems, particularly in high-voltage or high-power applications.
It is designed to provide a safe and visible means of isolating a circuit or equipment from the power source, ensuring that it is completely de-energized for maintenance or repair work.
Unlike circuit breakers, isolators do not have an arc interruption mechanism and are, therefore, not intended to open or close a circuit under load. Their primary function is safety isolation.
Visible Isolation Point: One of the main features of an isolator is its ability to provide a clear, visible gap in the electrical circuit, reassuring maintenance personnel that the circuit is indeed open and safe for work.
Operation Under No Load: Isolators are intended to operate only when there's no current flow in the circuit - either the circuit is already in an off state, or a circuit breaker has interrupted the current flow before the isolator is operated.
Types of Isolators:
Pantograph Isolators: Feature an extendable arm that can be raised or lowered to connect or disconnect the circuit.
Gas Insulated: Used in gas-insulated switchgear (GIS), employing SF6 gas to provide both insulation and the physical isolation gap.
Single or Multiple Poles: Isolators can be single or multi-pole, depending on the application. Three-pole isolators are common for three-phase systems.
Applications:
Isolation of transformers, bus bars, and generators for maintenance.
Isolation of sections of a high-voltage grid.
In substations, as part of safety protocols to ensure circuits are de-energized.
