The main characteristics of Sf gas are:
6
¨
The gas is neither combustible nor toxic.
¨
It is chemically stable and will not age with time.
¨
Breaking capacity of Sf6 gas is high even at relatively low pressure, because of
its superior dielectric and thermal properties.
¨
The interruption in Sf gas is not forced and thus no over voltages are
6
generated. No damping resistor or surge arrestor is needed, not even when
controlling small motors.
¨
The dielectric strength at the relevant pressure is about 3 times higher than air
and is roughly at par with oil.
¨
Any leakage is easily detected. To provide an extra margin of safety, the
breaker is capable of interrupting its rated current at rated voltage even at
atmospheric pressure.
The Sf breaker type HPA operates on what is usually referred to as the puffer
6
principle. This involves compressing the gas between a static piston and a movable
cylinder during the interruption action. The compressed gas is then blown through a
nozzle in which the arc is taking place. A combination of careful attention to design
and the use of proven components has meant that arcing times in the new HPA
breaker have been reduced to a minimum. As a result, the new breaker contacts will
normally not need replacement during the service life of the breaker. The breaker pole
operation is shown in fig. 2.
(4)
Fig - 2
(The Puffer Principle)
Summary of Contents for HPA 12kV
Page 7: ...Fig 3b HPA breaker pole for 36 kV ...
Page 9: ... 7 Fig 5 Circuit Breaker ...
Page 13: ...Fig 7A Maintenance schedule for frequently operated breaker type HPA 1VYN400290 005 11 ...
Page 14: ...Fig 7B Maintenance schedule for frequently operated breaker type HPA 1VYN400290 005 12 ...
Page 15: ...Electrical endurance HPA 13 ...
Page 29: ......