What is the difference between a Circuit Breaker and Isolator?

Circuit breakers and isolators are both devices used for safeguarding electrical systems. While they may appear similar in design for a novice user, a closer examination reveals distinct differences in design, operation, and intended usage. In this article, we look at the unique characteristics of circuit breakers and isolators and their importance in electrical engineering.

Definition:

Let's have a look at how these two devices are defined by their intended use case.

Circuit Breaker Definition 

The primary function of a circuit breaker is to detect abnormal conditions within the electrical system, such as overload, short-circuit, or ground faults, and interrupt the electric current through a combination of sophisticated trip mechanisms. Circuit breakers typically have three main types of tripping mechanisms - thermal, magnetic, and electronic. Upon detection of an electrical fault, the relevant system activates and trips the circuit to protect equipment and personnel from electrical hazards.

Isolator Definition  

An isolator is primarily a maintenance tool, it helps in isolating electrical circuits during repair works. The isolator physically disconnects a circuit from the power source to create a safe working environment for personnel, and effectively acts as a safeguard against live electrical components. Isolators generally have clear visual markers to indicate whether the circuit is energised or de-energised.

So, in essence, a circuit breaker is a safety device that protects personnel and equipment from electrical fault conditions whereas an isolator is a maintenance safety device that helps in disconnecting a circuit during upgrade or repair work.

Working Mechanism:  

While circuit breakers possess a number of tripping mechanisms, isolators are relatively simple in design.

Circuit Breaker Working Mechanism  

Normally, a circuit breaker has a thermal and a magnetic trip mechanism. The thermal strip provides protection against overload conditions, where the bimetallic strip melts to disconnect the circuit once the threshold of current rating is exceeded for a given amount of time. The magnetic trip mechanism acts via an electromagnet that trips the circuit instantly during short-circuits. More advanced circuit breakers (MCBs and MCCBs) also offer electronic trip capabilities, remote operation, and data logging capabilities.

Isolator Working Mechanism  

Unlike circuit breakers, there is no trip mechanism inside an isolator. The isolator is a manual switch which needs to be operated by personnel. It offers a simple open/close functionality, just like regular switches we use to turn on lights and power sockets. However, the construction of an isolator is sturdier than regular switches and sockets, as it is the physical barrier between the circuit and the power source.

Application and Uses:  

So, by now you should be aware of the basic functional differences between circuit breakers and isolators. Here are how these products are used in an electrical system:

Application of Circuit Breakers  

Due to the robust design and their ability to withstand harsh conditions like humidity, vibration, and shock, circuit breakers are widely used in diverse electrical systems. Here are some prime examples of circuit breaker usage:

• Residential electrical panels
• Commercial and industrial facilities
• Power generation and transmission systems
• Renewable energy systems
• Data centres and critical facilities
• Marine and off-shore applications

Application of Isolators  

As a more specialised product, isolators are only installed at places where circuit isolation is most likely to be required in future. Here are some examples of isolator usage:

• Electrical maintenance and repair
• Lockout-Tagout (LOTO) procedures to prevent unauthorised operation
• Critical equipment isolation from the grid
• Safety interlocking systems to ensure compliance
• Emergency shutdown systems (ESDs)
• Isolation for testing and commissioning

Regulatory Requirements:  

In India, electrical products are subject to various standards set by the Bureau of Indian Standards (BIS) and Indian Electrical Code (IEC). Whereas, International regulations for electrical products are led by the International Electrotechnical Commission (also IEC) and the International Organisation for Standardisation (ISO).

Regulations for Circuit Breakers in India  

IS/IEC 60898-1: This standard specifies requirements for low-voltage circuit breakers intended for household and similar applications. It covers aspects such as rated voltage, rated current, breaking capacity, tripping characteristics, and performance requirements. 

Regulations for Isolators in India 

While specific standards for isolators may not exist, they are typically required to comply with relevant sections of the Indian Electrical Code (IEC) and other applicable regulations governing electrical installations and equipment.

International Standards for Circuit Breakers  

1. IEC 60947 Series: This series of standards covers low-voltage switchgear and controlgear, including circuit breakers, for industrial applications. Standards such as IEC 60947-2 (circuit breakers) and IEC 60947-3 (switch-disconnectors) specify requirements for design, performance, testing, and safety considerations. Compliance with these standards ensures interoperability and consistency in circuit breaker performance across different countries and regions.
2. IEC 60898 Series: Similar to its Indian counterpart, IS/IEC 60898-1, this series of standards specifies requirements for circuit breakers intended for household and similar applications. It provides guidelines for aspects such as rated voltage, current-carrying capacity, breaking capacity, and tripping characteristics, ensuring the safety and reliability of circuit breakers used in residential installations.

International Standards for Isolators  

1. IEC 60947 Series: As with circuit breakers, the IEC 60947 series of standards covers various aspects of low-voltage switchgear and controlgear, including isolators. Standards such as IEC 60947-3 (switch-disconnectors) specify requirements for isolators used in industrial applications, ensuring their performance, safety, and interoperability with other electrical components.
2. ISO 13947: This standard, developed by the International Organization for Standardization (ISO), provides general requirements and test methods for disconnectors, switch-disconnectors, and fuse-combination units used in electrical installations. While not specific to isolators, ISO 13947 may encompass requirements relevant to isolator design, construction, and performance.

Also Read: Miniature Circuit Breaker (MCB) Vs Isolator Switch: Understanding Differences And Uses

Conclusion  

In the end, having circuit breakers and isolators as a part of electrical setup is a must have nowadays. If nothing else, it's peace of mind knowing that your equipment, family members, and personnel are always protected from electrical hazards with the right safety devices in place.

FAQs:

Q1. What are the advantages of isolators compared to circuit breakers?

Ans: Compared with circuit breakers, isolators are easier to design and are relatively cheaper. They are applied to disconnect loads of a circuit for servicing while, at the same time, no current is flowing through the load. Isolators give visible isolation points and, in this way, protect from electric current while working on electrical equipment. As for isolators, they cannot interrupt the fault currents and, therefore, are mostly used for non-load switching purposes.

Q2. What are the safety features of a circuit breaker?

Ans: Circuit breakers have protective measures such as the ability of the breaker to trip automatically for overcurrent, short circuit, and ground fault. They are designed to be able to break the current cycle almost immediately to avoid fires especially those associated with electricity and equipment damage. Certain Circuit Breakers also contain adjustable trip settings and even thermal-magnetic features to suit the load capacity as a way of improving the entire electrical system safety.

Q3. What are the safety features of an isolator?

Ans: Isolators offer safety in the aspect of electrical management by acting as a way to safely disconnect an electrical appliance from a power source. They are intended to withstand the off-load state, to exclude a current shift in the course of maintenance. The other components you will find on isolators include a mechanism that locks the circuit to avoid its re-energizing by accident and clear labels that inform about the status and further ensure the operation's safety and maintenance.

Q4. Can an isolator be used to prevent short circuits?

Ans: An isolator can in no way be used to avoid short circuits. Isolators are intended for the isolation of the circuits for maintenance requirements and it does not have the capacity to interrupt the fault currents. Short circuits cause the flow of a large amount of current through the circuit, and to eliminate them, one needs to use circuit breakers or fuses that sense overcurrent situations to switch off the circuit.