MGVCL Exam Paper (30-07-2021 Shift 2)
A 1000 kVA ONAN cooled transformer has a load of 500 kVA throughout the day except for a period of 4 hours. What is the permissible overload for a duration of four hours. Assume the permissible load kVA as a fraction of rated kVA is 1.24.

2480 kVA
930 kVA
1240 kVA
620 kVA

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MGVCL Exam Paper (30-07-2021 Shift 2)
A 50 Hz synchronous generator is connected to an infinite bus through a line. The p.u. reactances of generator and the line are j0.3 p.u. and j0.2 p.u. respectively. The generator no load voltage is 1.1 p.u. and that of infinite bus is 1.0 p.u. The inertia constant of the generator is 4 MW-sec/MVA. Determine the frequency of natural oscillations if the generator is loaded to 60% of its maximum power transfer capacity and small perturbation in power is given.

1.52 Hz
1.32 Hz
1.62 Hz
1.42 Hz

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MGVCL Exam Paper (30-07-2021 Shift 2)
Interposing current-transformer (CT) is used in differential protection of a transformer to

match the standard ratio of CTs used on both sides of the transformer winding
limit the main CT secondary current
minimize the effect of saturation of the main CTs
increase the sensitivity of the relay

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MGVCL Exam Paper (30-07-2021 Shift 2)
The magnitude of the generator earth-fault current is limited by

controlling field exciter
using higher rating CTs
inserting suitable resistance in neutral grounding circuit
inserting the stabilizing resistance in series with the relay

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