A circuit breaker is rated 2500 A, 2000 MVA, 33 kV, 3 sec, 3-phase oil circuit breaker. Determine the breaking current.

Breaking capacity of circuit breaker = √3*VL*Ib
VL - line voltage in volt
IL - Line current/breaking in ampere
VL = 33 kV
S = 2000 MVA

Ib = 30*1000 (in kVA)/(√3*33)
Ib = 34.99 kA

A generating station having 'n' section busbars each rated at Q kVA with ×% reactance is connected on the tie-bars systems through busbar reactances of b%. Determine the short circuit kVA if a 3-phase fault takes place on one section.

Short circuit kVA of any bus is given by:
Skva = Sbase*(100/% X)
Where,
Sbase - base rating in kVA
% X - value of reactance in %

Find the word which is correctly spelt from the given options.

In a short circuit test on circuit breaker, time to reach the peak re-striking voltage is 50 µs with the peak restriking voltage of 100 kV. Determine average RRRV (Rate of rise re-striking voltage)?

RRRV = Peak value of restriking voltage/time to reach the peak re-striking voltage
RRRV = 100*1000/(50 μs)
RRRV = 2*10⁶ kV/sec

In the circuit of figure, the switch is closed to position-1 for a long time. At t = 0 the switch position is changed from postion-1 to postion-2. Find an expression for the current i(t).

Standard eqution of current for this condition,
i(t) = i(0+)*cos(wt)
i(0+) = E/R
For LC circuit,
w = 1/√(LC)

i(t) = (E/R)*cos((1/√(LC))*t) A

Fill in the blanks with suitable Preposition from the given alternatives.
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