Circuit Breakers, Relays and Lightning Arrestor

Circuit Breaker (CB): it is a protective device which protects the electrical equipments from the fault  condition, it has tho contacts one is fixed contact (FC) & another is moving contact (MC), under normal condition FC is attached with MC, under fault condition FC is separated with MC.
under fault condition a gap produced between FC & MC, between circuit breakers are classified in to many types they are

1. Oil CB

A) MOCB (minimum oil CB)      b) Bulk oil CB

2. VCB (Vaccun CB)

3. SF6 CB (Sulphur hexa fluoride CB)

4. ACB (Air CB)

5. MCCB (Molded CB)

CB 1,2,3, are used at HV side because it has high voltage low current 

CB 4,5 are used at LV side because it has low voltage high current 

CB consists three types of coils to operate

1. Shunt Coil

2. UV (under voltage) Coil

3. Close Coil

Types of faults to operate the CB: 

Depending up on fault the Cb gets operate

Short circuit fault

Over load fault

Instantaneous earth fault

Ground fault

Relays

Relay: it is a sensing device which sense the fault and gives the command to the circuit breaker to trip the circuit.

Types of Relay: 

• Differential relay
• Earth Fault relay
• Over current relay
• Over load relay
• Phase prevent relay
• Instantaneous earth fault relay
• Under voltage relay
• Over voltage relay

LIGHTNING ARRESTOR

Lightning Arrestor: it is also known as surge protector, it is used to protect the electrical of equipments, when ever surge is diverted to the earth.

Types of lightning Arrestor: 

1. Rod type
2. Horn gap type
3. Expulsion type
4. Non liner resistor type with gaps