What is ISOLATOR,ELCB,MCB?

ISOLATOR

It is a Mechanical Operated Switch Isolates a part of Electrical circuit.
Difference between  ISOLATOR and a circuit Breaker is a Circuit breaker is made interrupt the fault current Usually isolator  is Present at both the end of C B.range of an isolator .Up to 145kv is Hand Operation. 
           
                            While higher Voltage like 245kv or 420kv is it motorized Classicfication of Isolator Depending upon the requirement is it Classified in to single break isolator Double break Isolators  Pantograph isolators Tilting type and Rotating type and so on . As  par the Position of Isolator in a power System it is Classifieds in to line side Bus side isolator Transfer bus side Isolator et cetera.

 ELCB 

  

    Electrical Safety device used for installing an electrical device with high earth impedance to avoid shock.The main purpose of Elcb is to damage to human due to shock.

  

An ELCB is a device use for protecting electrical appliances from excess current. An earth wire connects the appliance from the plug point to a metal plate in the ground.

  

If excess current flows through the appliance the current will flow through the earth wire in the plug and directly towards the metal plate in the ground.

This is called the earth leakage current. The excess current is dispersed in the ground. An earth leakage circuit breaker operates by means of a switch controlled by an electromagnet, a device consisting of an iron or steel core that is Magnetised by electric current in a coil

Operation

  

ELCB is a Specialised type of latching relay that has a building’s incoming mains power connected through its switching contacts so that the ELCB disconnects the power in an earth leakage condition.

The ELCB detects fault currents from live to the earth wire within the installation it protects. If sufficient voltage appears across the ELCB’s sense coil, it will switch off the power, and remain off until manually reset. An ELCB however, does not sense fault currents from live to any other earthed body.          

If either of the earth wires become disconnected from the ELCB, it will no longer trip and the installation will often no longer be properly earthed.

Some ELCBs do not respond to rectified fault current. This issue is the same in principle with ELCBs and RCDs, but ELCBs are on average much older and specs have improved considerably over the years,

so an old ELCB is more likely to have some uncommon fault current waveform that it will not respond to.With any mechanical device, failures occur, and ELCBs should ideally be tested periodically to ensure they still work.

MCB

    A miniature circuit breaker automatically switches off electrical circuit during an abnormal condition of the network means in overload condition as well as faulty condition. Nowadays we use an MCB in low voltage electrical network instead of fuse. The fuse may not sense it but the miniature circuit breaker does it in a more reliable way.MCB  is much more sensitive to overcurrent than fuse.

  

Handling an MCB is electrically safer than a fuse. Let’s look at the working of the miniature circuit breaker.

   

Working principle of MCB

                    Whenever continuous over current flows through MCB, the bimetallic strip is heated and deflects by bending. This deflection of bimetallic strip releases mechanical latch. As this mechanical latch is attached with operating mechanism, it causes to open the miniature circuit breaker contacts, and the MCB turns off thereby stopping the current to flow in the circuit. To restart the flow of current the MCB must be manually turned ON. This mechanism protects from the faults arising due to over current or over load.

  

MCB operation

  

If the circuit is overloaded for a long time, the bi-metallic strip becomes overheated and deformed. This deformation of Bi-metallic strip causes, displacement of latch point. The moving contact of the MCB is arranged by means of spring pressure, with this latch point, that a little displacement of latch causes, release of spring and makes the moving contact to move for opening the MCB.