Electrical Protective devices

Posted On :   18/11/2019||01:57:04pm

Posted By :Sreeraj N

Electrical protective devices have very important role in these days because of our life very close or depending to electricity so protection from electrical fault is very important in our life.


Fuse safety deviceFuse safety device

Fuse is a system of fuse wire,placed in a fuse holder. and it’s designed for protection from damage caused by overcurrent / overload / Short circuit.

Fuse is a short length of wire designated to melt and separate in case of excessive current.The fuse is connected in the phase of the supply.It is always connected in series with the circuit / components that need to be protected.When the current drawn by the circuit exceeds the rated current of the fuse wire,the fuse wire melts and breaks.This disconnects the supply from the circuit and thus protects the circuit and the components in the circuit.

Fuse carrier and channel are made of porcelain or Bakelite material. The fuse wire is made of low resistivity material and low melting point(zinc, copper, silver, aluminum).

Circuit breakers

Circuit breakers

It’s an electrical switch operated by automatically and it’s designed for protection from damage caused by overcurrent / overload / Short circuit. Basically circuit breakers are used to interrupt current flow after a fault is detected. It’s a type of fuse but a fuse which operates once and then must be replaced (by changing fuse wire); a circuit breaker can be reset to resume normal operation.Its know as in short name CB.

Depending upon CB rating and working nature its mainly divided into 4 types.

1. MINIATURE CIRCUIT BREAKER ( M.C.B ) :- which work magnetIc thermal release principle.it act and open the circuit in less than 5 milli seconds.It is connected in the phase,between the supply line.Its coming under 100 Ampere and its used for house / small electronic circuits. It can reset easily by switch liver no need of rewiring fuse.

2. Molded CASE CIRCUIT BREAKER ( M.C.C.B ) : – Its a type of MCB but it’s different by its usage that means its used for high power equipment. ( 10000 to 200000 Amps )


3. EARTH LEAKAGE CIRCUIT BREAKER (E.L.C.B ) : – Earth leakage circuit breakers are used to protect the circuit from the electrical leakage .In circuit someone gets shocked the ELCB cuts off the power within the time of 0.1 seconds.There are two types of ELCB 1.Voltage Earth Leakage Circuit Breaker. 2. Current Earth Leakage Circuit Breaker.


4. EARTHING OR GROUNDING :- Connecting the metal body of an electrical appliance,machinery or an electrical installation to earth,through a low resistance wire,is called Earthing or Grounding.



Its an electrical switch working by the help of electromagnetic property.Commonly its seeing in motor starters.It’s helping the motor starting by control system means ON/OFF SWITCH Automatic or manually. Contactor is switching device as well as a protective device.

Overload relay : – As the names we can know its a relay switch or dripping device from overload and this overload relay classified as nature of overload means Temperature,Current,Voltage like

Symbols used in Electrical standers above mentioned terms


Photo credits :- Nachi,Havells