10-12-2012, 03:06 PM
TRANSMISSION
TRANSMISSION.pptx (Size: 203.23 KB / Downloads: 34)
Introduction.
A Circuit breaker is an equipment that breaks a circuit either manually or automatically under all condition at no load , full , load or short circuit.
Operating Principle.
When C.B is closed & it carries F.L. current. It is also equipped with CT, relay coil & trip coil.
In case of fault, the C.B. actuates a relay coil through trip coil ,which operates immediately & disconnects equipment from the supply.
Operation :-
Under normal operating conditions , the moving contacts remain engaged with the upper fixed contact . When a fault occurs , the moving contact is pulled down by the tripping springs and an arc is struck . The arc vapourises oil and produces gases under high pressure .
Advantages.
Advantages compared to bulk oil circuit breaker.
It requires lesser quantity of oil
It requires smaller space
There is reduced risk of fire
Maintenance problems are reduced
Disadvantages.
Due to smaller quantity of oil , the degree of carbonisation is increased.
Vacuum Circuit Breaker.
Vaccum is used as an quenching medium
Have greatest insulating strength.
10-7 to 10-5 pressure is to be maintained.
Used is 11kv panel in control room of grid station.