circuit breaker is electrical device to carry load and to isolate in case of fault.

1. CIRCUIT BREAKER
-B. Prasad
Chartered Engineer
amieclub@gmail.com

2. TECHNICAL ASPECT
 RATED VOLTAGE
NORMAL CURRENT
RATING
SHORT CIRCUIT CURRENT
RATING
INDOOR/OUTDOOR TYPE
MOTORISED/NON-
MOTORISED
REMOTE/LOCAL
OPERATION

3. Circuit breaker types
 Air magnetic
 • Oil
 • Air blast
 • Vacuum
 • SF6 gas

4. Fundamental characteristics of a
circuit breaker
 Its rated voltage Ue
 Its rated current In
 Its tripping current level
adjustment ranges for
overload protection (Iror
Irth)
 short circuit protection (Im)

5. Selection of Switching Devices
LOW VOLTAGE
 Fuse
 MCB
 ELCB
 MCB
 MCCB
 SFU
 ISOLATOR
 CHANGE OVER
 CNTACTOR
MEDIUMHIGH
VOLTAGE
 ACB
 OLCB
 VCB
 SFC BREAKER
 HT FUSE

6. Breaker parts

7. VACUUM INTERRUPTER

8. Vacuum interrupter side view

9. Interlocks
 Breaker may not be taken out unless it is off.
 Closed breaker may not go in service position.
 Closed breaker will trip when taking outside.
 Test position limit switch.
 Service position limit switch.
 VCB in service and locked.
 Service position key.

10. Rating, selection of breakers
 Rated voltage:12 KV to 765KV
 Rated current:
200,400,630,800,1000,1250,1600,2000,
2500,3150,4000A
 Rated frequency: 50 or 60Hz
 Short circuit breaking
current:12.5,16,20,25,31.5,40,50,63,80 KA
 Rated short time withstand current: 1s

11. Breaker control circuit

12. ACB MOUNTED ON CRADLE

13. ACB CRADLE

15. SF6 breaker
 Known as
Sulphur
hexafluoride
 Suitable for 66
KV to 800KV
 Generates
greenhouse
gas, safety
issue

16. Breaker comparison
Functions performed
Protections
Isolation Control
Switchgear Overloads Short-circuit
Fuse Yes Yes No No
Disconnector No No Yes No
Switch No No Yes? Yes
Disconnector –
fuse
Yes Yes Yes No
Switch – fuse Yes Yes Yes? Yes
Contactor No No No Yes
Circuit-
breaker
Yes Yes Yes? Yes

17. ACT FAST AND INITIATE
FIRST
 बड़ा सोचो
 तेजी से सोचो व
 सबसे पहले सोचो
 िवचारो पर िकसी का
 एकािधकार नही होता.
---- धीरभाई अमबानी

18. Thank you