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GATE 2020 || Power Systems || Quiz 11 (App update required to attempt this test)
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Question 1
What is the symmetrical breaking current if a three phase 33 kv oil circuit breaker is rated 1200 A, 2000 MVA, 3 secs?
Question 2
An air blast circuit breaker is designed to interrupt a transformer magnetising current of 11 A (r.m.s.) chops the current at an instantaneous value of 7 A. If the values of L and C in the circuit are 35.2 H and 0.0023 μF, then the value of voltage that appears across the contacts of the breaker is (Assume that all the inductive energy is transferred to the capacitance)
Question 3
A list of relays and the power system components protected by the relays are given in the group I and group II, respectively. Choose the correct matches from the choices given below :
Group I
P–Distance Relay
Q-Under Frequency Relay
R-Differential Relay
S–Buchholz Relay
Group II
1) Transformer
2) Turbines
3) Busbars
4) Shunt capacitors
5) Alternators
6) Transmission Lines
Question 4
In a 132 kV system, the series inductance up to the point of circuit breaker location is 50 mH. The shunt capacitance at the circuit breaker terminal is 0.05 μF. The critical value of resistance in ohms required to be connected across the circuit breaker contacts which will give no transient oscillation is _____________.
Question 5
A three phase Δ-Y connected ,30 MVA, 33/11 kV transformer is protected by a differential relay. If the fault drawing up to 200 % of the rated current, then the relay current is (Assume the CT ratio on primary side is 500:5 and that on secondary side is 2000:5)
Question 6
An IDMT over current relay has a current setting of 150 % and a time multiplier of 0.5. The C.T ratio is 500:5. The operating time characteristics for a time multiplier 1.0 is given in the table
The actual operating time (in seconds) for a fault current of 6000 A is
The actual operating time (in seconds) for a fault current of 6000 A is
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Sep 17ESE & GATE EE
