What is the difference between isolator and switch?
Answer:
A switch is a simple device to connect or disconnect power supply in one equipment or service. An isolater can have multiple areas of power distribution and these areas can be isolated from power supply and taken for maintenance with out functionally affecting the other areas.Hence isolators are largely used in industries in power distribution panels .There can be isolaters with locking device for safety.
Major difference between isolator and circuit breaker is that isolator is an off-load device, whereas circuit breaker is an on-load device.
(An isolator switch is part of an electrical circuit and is most often found in industrial applications. The switch does exactly what its name suggests in that it electrically isolates the circuit or circuits that are connected to it. Such a switch is not used normally as an instrument to turn on/off the circuit in the way that a light switch does. Either the switch isolates circuits that are continually powered or is a key element which enables an electrical engineer to safely work on the protected circuit.
Isolator switches may be fitted with the ability for the switch to padlock such that inadvertent operation is not possible. In some designs the isolator switch has the additional ability to earth the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both end of the circuit need to be isolated.
An isolator is a switch connected after a circuit breaker. When a circuit or a busbar is taken out of service by tripping the circuit breaker, the isolator is then open circuited and the isolated line is earthed through earth switch so that the trapped line charges are safely conducted to ground.
A circuit breaker is a complex circuit -breaking device with the following duties:
Make or break both normal and abnormal currents,
Appropriately manage the high-energy arc associated with current interruption. The problem has become more acute due to interconnection of power stations resulting in very high fault levels,
Effect current interruption only when it is called upon to do so by the relay circuits. In fact they are required to trip for a minimum of the internal fault current and remain inoperative for a maximum of through fault current,
Rapid and successive automatic breaking and making to aid stable system operation,
3-pole and single pole auto-relosing arrangement.
In addition to these making and breaking capabilities, a circuit breaker is required to do so under the following typical conditions:
Short-circuit interruption
Interruption of small inductive currents
Capacitor switching,
Interruption of short-line fault,
Asynchronous switching
In practice there may be no physical difference, but their purpose is different. A switch is used in a circuit to turn whatever devices on the circuit on or off whereas an isolater is used to isolate the whole circuit so it can be safely worked on. Some isolation switches also ground the circuit. Isolation switches are often more robust and may latch open so they can't be accidently switched on when someone is working on the circuit, they may also have a device that needs to be released before the switch is closed or be locked open. A common work practice is to have a notice fixed to the isolation switch advising of the danger of switching it on which is fixed in such a way that it has to be removed before switching the circuit back on. A related device is an emergency kill or cut off switch which is pressed to shut down machinery when an accident occurs. These are normally more difficult to reset than to switch off.
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