Q: What is Vacuum
Circuit Breaker? Where it is used?
Ans: In VCB vacuum as a dielectric medium is used
to quench the arc.
VCB can be applied up to
35KV. Multi-unit VCB have been employed at voltages up to
72.5 KV.
The space required smaller than OCB and employed in both indoor and outdoor services.
Q:Why we use VCB
at High Transmission System, why not ACB?
Ans: Vacuum
has high arc quenching property compare to air. The dielectric strength of
vacuum equal to 8 times that of air. That is why always VCB used as in HT
breaker and ACB used as in LT.
Q:What is the
function of anti-pumping in circuit breaker?
Ans: When breaker is close at one time by close
push button, the anti-pumping contactor prevent to re-close the breaker by close
push button after if it already close.
Q: What is SF6 Circuit Breaker?
Q: What is SF6 Circuit Breaker?
Ans: In SF6 circuit breaker SF6 gas is used as arc
quenching medium.SF6 is Sulfur hexafluoride
gas. SF6 gas has excellent insulating strength because of affinity for
electrons. It is 100 times as effective as Air.
Q. What are the tests carried out of a CB?
Q. What are the tests carried out of a CB?
Ans: 1. Short Circuit
tests:
a) Making capacity test
b) Breaking capacity test
c) Short time current test
d) Operating duty test
2. Dielectric tests:
i) Power frequency tests:
a) One minute dry withstand test
b) One minute wet withstand test
II) Impulse voltage dry withstand test
3. Thermal test