The document discusses circuit breakers, including their technical aspects, types, fundamental characteristics, parts, and comparisons to other switching devices. It describes circuit breaker ratings like voltage, current, and short circuit levels. Common circuit breaker types include air magnetic, oil, air blast, vacuum, and SF6 gas. The document also outlines selection criteria for low and medium-high voltage switching devices and reviews circuit breaker control circuits, interlocks, and SF6 circuit breakers.

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