SF6 CIRCUIT BREAKER
Is the circuit breaker that uses SF6( sulphur hexaflou
ride)gas as an air quenching medium
It is an electro-negative gas
It has high dielectric strength to absorb free electron
s
SF6 circuit breaker is very high effective for high volt
age (33kv-800kv)
WORKING PRINCIPLE OF SF6 BR
EAKER
SF6 is based on self blast and compessing technique
When fault occurs the main contacts are separated. The cu
rrent flowing through the arcing contacts makes no electri
c arc is hit
The displacement of the moving contacts is synchronized
with the valve which enters the high pressure SF6 gas in th
e arc interrupting chamber at a pressure of about 16kg/cm²
SF6 BREAKER...
 The free electrons in the arc are absorbed by SF6 gas to form relatively i
mmobile negative ions.This is arcing contact separation.
 The loss of electrons in the arc builds up enough dielectric strength exti
nguish the arc circuit breaker to open.
 PROPERTIES OF SF6 CIRCUIT BREAKER
 Physical properties
 Excellent heat transfer property
 No colour,no odor,non toxic and non flammable gas
 Chemical properties
 Chemical inert
 Non corrosive on all metal at ambient temperature
 Chemical stable at atmospheric pressure and temperature
 Electrical properties
 High dielectric strength
 Arc interrupting capcity
 The dielectric constant is independent of the frequency of the applied vo
SF6 CIRCUIT BREAKER
Advantages
Less arcing time
Low maintenance costs
The gas has good insulating properties
Noiseless operations
There is no risk of fire as it is non inflammable
Disadvantages of SF6 circuit breaker
The cost of gas is high
Needs cleaning periodically
Application of SF6 circuit breaker
Power distribution and control
Line protection for power circuit
SF6 CIRCUIT BREAKER
Capacitor blocks
Rectifier circuits
For protection of transformers