Answer / s syed mohamed

Actually the thing is vacuum has high arc queching property
compare than air .becoz in VCB ,the die electric strength
is equal to 8 times of air . That y always vaccum used as in
HT breaker and air used as in LT in these breakers employ
with high resistance intruption principle.

Answer / g.ravikanth

vcb means "vaccume" at higher potential there is a chance
of ionization of air molecules but if it is vaccume there
is no chance at all for ionization.

Answer / er. ankush miglani 9718151073

at high voltages the air may get ionized but the vaccum
doesnt. so dats why..........

Answer / reddy

VCB provides more insuklation strength than ACB ... ACB
upto 132kV

Answer / rajesh dhankar

i'm sorry to say that above two answer give above are half
correct. because all u r talking about ionized air if u ever
open Chamber where CT's and PT's are connected u will find
distance less than a hand away and there is no problem of
ionized air there.
The main reason after that is at a time of breaking a ckt or
can say shutting down a ckt when load is not completely zero
there can be big damage or accident because of higher
voltage rather if load is completely zero then there is no
problem.
and ACB are used in low tension line where low voltage and
higher load can be controlled.

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