Question

By constantly measuring the electrical quantities which differ during normal and abnormal conditions_______ is the device which detects abnormal condition in electric circuits.
1. Protective Relay
2. Air Circuit Breaker
3. MCB
4. Differential Relay

Answer 1

Correct Answer - Option 1 : Protective Relay

Protective Relay:

• A Protective Relay is a device that detects the fault and initiates the operation of the circuit breaker to isolate the defective element from the rest of the system.
• Relay is an automatic device which detects an abnormal condition or fault in an electrical circuit
• It works on the concept of a magnetic field and Faraday law
• Relays control one electrical circuit by opening and closing contacts in another circuit

 

Fundamental Requirements of Protective Relay:

• Selectivity 
• Speed
• Sensitivity
• Reliability
• Simplicity
• Economy

• A differential relay is defined as the relay that operates when the phase difference of two or more identical electrical quantities exceeds a predetermined amount.
• Air circuit breakers are widely used for the low voltage circuits as well as the highest transmission voltages. Simple air circuit breakers that do not incorporate any arc-control devices are used for low voltages, below 1 kV.
• Miniature Circuit Breaker is used to protect the circuits from short circuit fault. It is used in the place of fuse. When the amount of electricity is increasing in wire, the MCB turn off and the result is it breaks the circuit. It prevents from burning of home appliances.