Difference between Circuit Breaker and Isolator / Disconnector

Difference between Circuit Breaker and Isolator / Disconnector

Everyone is aware of the importance of electrical safety measures but many of us lack knowledge of the various types of electrical devices available in the market to ensure the safe functioning of electrical equipment. Switchgear is an umbrella term that comprises the most significant set of devices that augment such safety. The two most common names among switchgear, found almost in every electrical power system, are circuit breakers and isolators/disconnectors. These two devices are indispensable for electrical power systems. 

Both the circuit breaker and the isolator are entrusted with the common function of disrupting or isolating connections in electrical circuits in case there is a problem with the electrical system. This close functional association between the two leads many people to confuse the isolator with the circuit breaker and vice versa. In this article, we are going to bust this common misconception by looking at the difference between circuit breakers and isolators. Let’s get to know more about these essential safety devices.

What is a Circuit Breaker? 

A circuit breaker is a device that works like a switch to ensure electrical safety. Circuit breakers are installed in series within an electrical circuit such that they are enabled to stop current flow whenever a fault is detected. The principal function of a circuit breaker is to safeguard against short-circuiting and overloading in a circuit. A relay system is used by the circuit breaker to detect such faults in the circuit. Once faults are detected, it automatically stops the flow of current to prevent damage to both the circuit and connected appliances or equipment.

Circuit breakers come with operating options. They can be switched on automatically as well as manually. They are also equipped with an extinguishing system that allows them to function even during on-load conditions. Circuit breakers are typically attached to electrical devices and equipment such as transformers. They are capable of dealing with heavy load currents. 

Read Also - Types Of Circuit Breakers And Their Importance

What is an Isolator/ Disconnector? 

Isolators are also often called disconnectors. It is a unit of switchgear that can be used to disconnect the entire circuit or even isolate parts of an electrical circuit. Essentially, an isolator or disconnector is a disconnecting switch that can be used only under off-load conditions, i.e., when there is no current flow in the circuit. This is a principal point of difference between a switch isolator and a circuit breaker.

The disconnector usually comes into use when an electrical system is to undergo repair or maintenance. Such an electrical system needs to be isolated to protect the technician as well as equipment. In the manner of a capacitor, an isolator allows the AC components to function while blocking the DC components. 

An isolator is installed separately within the electrical circuit to ensure safe maintenance and repair of faulty sections. The most significant aspect of the isolator is that no current should be flowing through it when it is being operated. 

Characteristics of Circuit Breaker and Isolator

While both circuit breakers and isolators are part of switchgear components, they have certain unique characteristics of their own. Here are some of the essential characteristics of each:

Circuit Breakers

  1. Surge protection: Circuit breakers are primarily designed to protect electrical circuits from overcurrent conditions. They automatically disconnect the circuit when an excessive current flows through it, preventing damage to equipment and mitigating the risk of fire.
  2. Interrupting capacity: Circuit breakers are rated for their ability to interrupt a fault current safely. 
  3. Tripping mechanisms: Circuit breakers employ different tripping mechanisms, including thermal, magnetic, or a combination of both, to sense and respond to overcurrent conditions. 
  4. Resettable: Unlike fuses, circuit breakers are manually or automatically resettable after they trip. 
  5. Application in various voltage systems: Circuit breakers are used in a wide range of voltage levels, from low-voltage residential applications to medium and high voltage in industrial settings and power transmission.


  1. Isolation function: Isolators are used to physically disconnect a part of the electrical system for maintenance or repair purposes. 
  2. No current interruption: Isolators are not designed to interrupt current under normal operating conditions. Their primary function is to isolate a section of the circuit for maintenance, allowing personnel to work safely.
  3. Visible open/closed position: Isolators often have a visible open/closed position indicator to provide a clear visual indication of the state of isolation. This helps ensure that workers can easily determine whether a circuit is isolated or energised.
  4. Manual operation: Isolators are generally manually operated.
  5. Limited fault current interruption capability: While isolators can handle some fault current, their primary purpose is not to interrupt fault currents. Circuit breakers are responsible for handling fault currents and protecting the system.

Read Also - Understanding The Difference Between Isolators, Rccbs, And Mcbs: A Comprehensive Guide

Nine Notable Differences between Isolator and Circuit Breaker 

Now that we know the essential characteristics of both - a circuit breaker and an isolator, let us dive into the difference between a switch disconnector and a circuit breaker.

Basis of Difference

Circuit Breaker


  1. Definition

Protective electrical device that acts as a switch to interrupt current flow through a circuit whenever faults are detected.

A kind of disconnecting switch is used to isolate an electrical system from the main power supply for safety reasons.

  1. Build

A single unit consisting of an electromagnetic switch and a relay system.

A simple mechanical switch.

  1. Operation

Manual and automatic


  1. Type

On-load; can be used when the power supply is on

Off-load; no current can flow through the circuit when in use

  1. Capacity

Low, Medium, High


  1. Use

Protects the entire circuit from surge currents by switching off the power supply as and when required.

Isolates faulty parts of a circuit to facilitate repair and/or maintenance.

  1. Applications

Domestic, commercial, and industrial applications

Mostly industrial applications

  1. Breaking capacity



  1. Expense

More expensive

Less expensive

Now that you understand the differences between isolators and circuit breakers and the role played by each of these two components, you can confidently look for the protective device that best suits your specific requirements.

Purchase the Best Quality Isolators and Circuit Breakers at the Schneider Electric eShop 

Whether you are looking for switchgear components for your household or industrial applications, Schneider Electric is a brand name you can trust. Visit the Schneider Electric eShop to look for and secure the best deals on all kinds of protective electrical equipment, including isolators and circuit breakers.

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