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

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

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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)
A three-phase, 12 kV, 50 Hz and 300 kW load is operating at 0.8 pf lag. If the pf is to be improved to unity, using star connected capacitor, the per phase value of the reactive VAR required is:

50 kVAR
75 kVAR
25 kVAR
100 kVAR

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MGVCL Exam Paper (30-07-2021 Shift 2)
Consider the following statements associated with Buchholz's relays.
Statement 1: Buchholz's relay is a current operated device.
Statement 2 : Buchholz's relay is placed between the transformer tank and the conservator.

Statement 1 is FALSE and Statement 2 is TRUE
Both Statement 1 and Statement 2 are TRUE
Both Statement 1 and Statement 2 are FALSE
Statement 1 is TRUE and Statement 2 is FALSE

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MGVCL Exam Paper (30-07-2021 Shift 2)
The miniature circuit breaker (MCB) with Class D trip characteristics trips instantaneously when the current flowing through it reaches ____ the rated current.

between 2 to 3 times
between 10 to 20 times
between 3 to 5 times
between 5 to 10 times

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