Difference between Relay and Circuit breaker

Relays and circuit breakers are two commonly used terms of a power system. The study of the protection in power systems is incomplete without the study of relays and circuit breakers. The uses of relays and circuit breakers are found in industrial as well as in commercial applications. There are many differences between a relay and a circuit breaker. Let us see what is the difference between relay and circuit breaker.

Difference between Relay and Circuit breaker in tabular form

Relay Circuit Breaker
A relay is a switching device used in the power system for providing signals to the circuit breaker as soon as a fault occurs in the system. A circuit breaker is a device that is used in the power system breaks the circuit automatically after getting the signal from the relay.
A relay works like a sensor that senses the fault that occurred in the circuit and sends the signal to the circuit breaker. A circuit breaker breaks the contacts after receiving the signal from the relay.
A relay is a switching and sensing device. A circuit breaker is a disconnecting or isolating device.
The operation of a relay takes place on the low power input voltage. A circuit breaker is automatic on load device.
A relay is used in the circuits where control and selection of one among many circuits is needed. One circuit breaker is used for one circuit.
A relay can amplify discrete signals. A circuit is not capable of amplifying any signal.
Relays are used to protect electrical equipment like a transformer, motor, generator, etc. Relays continuously monitor voltage, current, and power in a circuit and send signals in the case of irregularities. Circuit breakers are used to protect the circuit from overload and short circuit currents. Circuit breakers are used for switching loads in buildings, industries, etc.

What is a relay?

A relay is basically a switching and sensing device that sends the signal of fault to the circuit breaker present in the circuit in order to prevent the system from damages. The relay continuously monitors the parameters of a circuit like voltage, current, power and provides a signal as soon as it detects any fault. Relay is a very useful device used for protection in every power system.

What is a circuit breaker?

A circuit breaker is an isolating or disconnecting device that disconnects the circuit on receiving the signals of occurrence of a fault in the circuit. The relay is the device from which a circuit breaker receives these signals and protects the circuit from damages. Every circuit in the power system from household to industrial contains a circuit breaker as a protecting device.


In the study of power system protection, relays and circuit breakers are the primary protective devices to be studied. In spite of the differences, both the devices are used for the protection of the circuits. Electric motors, generators, transformers, and all other electric equipment use relays and circuit breakers.


Sunmoni Gohain
NIT Silchar

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