Difference between Isolator and Circuit Breaker

In electrical power system, various devices are used to ensure the safe operation of electrical equipment. The most important set of these devices that helps to ensure this safety is switchgears. Amongst these switchgears, the circuit breakers and isolators are commonly used in every electrical power system. These two devices are very important in an electrical power system.

The isolator and circuit breaker both have a similar function of disconnecting the electrical circuits when there is an issue in electrical system. Therefore, they are closely related to each other, however, there are many differences between circuit breaker and isolator that draw a line between these two.

This article is meant for explaining the differences between circuit breaker and isolator. Also, it will explain what the circuit breaker and isolator are, so that the reader can easily understand the differences between the two components.

What is a Circuit Breaker?

A circuit breaker is an electrical safety device which works like a switch. The circuit breaker is arranged in series in an electric circuit so that it can stop the flow of current through the circuit whenever required. The primary function of a circuit breaker is to protect the circuit from overload and short-circuit faults. The circuit breaker detects such faults with help of a relay system and interrupts the current flow through the circuit, preventing further damages

A typical circuit breaker can be operated manually and automatically. The circuit breaker also has an in-built extinguishing system which enables it to operate under on-load conditions. A circuit breaker is attached to the electrical devices such as transformers, etc. and is suitable for handling heavy load currents.

What is an Isolator?

An isolator is a switchgear component which is used to disconnect or isolate the whole or a specific part of the circuit. Sometimes, an isolator is also called as a disconnector. Basically, the isolator is a disconnecting switch that can be operated under off-load conditions only, i.e. it can only be operated when there is no current flowing through the circuit.

The isolator is used when maintenance and repair are to be done in an electrical system to protect the technicians and other equipment. An isolator blocks the DC components and allows the AC components to flow though it just like a capacitor.

The isolator is a separate part of the electrical system which is created for safe maintenance of the faulty section. Most important thing about an isolator is that while anyone using an isolator, the current flowing through it must be zero or within the limits of safety.

Difference between Isolator and Circuit Breaker

The following table highlights the major differences between isolator and circuit breaker-

Basis of DifferenceIsolatorCircuit Breaker
DescriptionAn isolator is a type of disconnecting switch which is used in an electrical circuit to ensure that the circuit is totally isolated from the supply mains.A circuit breaker is a protective electrical device that works as a switch and is used to stop the flow of electric current through the circuit wherever necessary.
Circuit symbol
ConstructionAn isolator is a simple mechanical switch.A circuit breaker consists of an electromechanical switch and a relay system in a single unit.
Operation MethodIsolator can only be operated manually.Circuit breaker can be operated manually as well as automatically.
Type of deviceIsolator is an off-load device, i.e. it can only be operated when there is no current flowing through the circuit.Circuit breaker is an on-load device. Hence, it can be operated under power on conditions.
FunctionsThe major function an isolator is to disconnect the faulty part of an electrical system, so that it will be safe to repair.The function of a circuit breaker is to protect the entire electrical system, if there is a fault. Also, it serves the function of a switch to cut off the supply wherever necessary.
ContactsA typical isolator has main and moving arms.A typical circuit breaker has main and arcing contacts.
Withstand capacityIsolator has a low withstand capacity to currents.A circuit breaker has high withstand capacity.
Insulation & quenching mediumIsolator does not need insulation or insulation medium. Isolator uses atmospheric air as arc quenching medium.Circuit breaker requires insulation medium and arc quenching medium such as air, oil, vacuum, SF6 gas, etc.
Provide interruptionIsolator provides the interruption in the power supply only during inspection, maintenance or repair.Circuit breaker interrupts the power flow during normal as well as fault like short-circuit and overload.
Removal of trap chargesIsolator can remove the trap charges.Circuit breaker is incapable of removing the trap charges.
Need of relay systemIsolator does not require relay system for the operation.Circuit breaker uses relay system to detect the errors in the system.
Earth switchSingle or double earth switches can be provided in an isolator.No earth switch can be included in a circuit breaker.
Over voltage during switchingThere is no rise of overvoltage during switching of an isolator.There may be rise in overvoltage during switching of a circuit breaker.
Breaking capacityThe breaking capacity of isolator is less, as it cannot be used to break load faults.The breaking capacity of circuit breaker is more, hence it can be used to break the load faults.
SafetyThe isolator ensures the safety for technicians and switchgears.Circuit breaker is not very safe, only professional and well trained technicians can operate it safely.
CostIsolator is less costly.Circuit breaker is very expensive.
ApplicationsIsolators find applications only in industrial electrical systems to disconnect the circuit during maintenanceCircuit breakers are widely used in domestic, commercial, and industrial electrical systems for normal switching as well protection from fault.


In this article, we have highlighted many differences between isolator and circuit breaker, along with their brief description. The circuit breakers and isolators are important switchgear components in any electrical power system that ensure that the abnormal currents in the system due to any fault do not damage the electrical installations.

Updated on: 08-Jul-2022

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