Power Systems Objective Questions & Answers
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An over current relay, having a current setting of 125% connected to a supply circuit through a current transformer of ratio 500/5. The plug setting multiplier for a fault current of 5 kA is
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Equal area criterion gives the information regarding
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Which of the following transformer is used in sub station for operating a protective relay?
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If a generator of 250 MVA rating has an inertia constant of 6 MJ/MVA, its inertia constant on 100 MVA base is
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If the inertia constant H = 8 MJ/MVA for a 50 MVA generator, the stored energy is
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If the inertia constant H = 10 MJ/MVA for a 50 MVA generator, the stored energy is
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Making and breaking currents of 3 phase AC circuit breakers in power system are respectively in what form?
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Normally Z bus matrix is a
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Stock bridge dampers are used in case hill areas to over come the which problem?
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An isolated synchronous generator with transient reactance equal to 0.1 pu on a 100 MVA base is connected to the high voltage bus through a step up transformer of reactance 0.1 pu on a 100 MVA base. The fault level at the bus is
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In a 220 kV system, the inductance and capacitance up to the circuit breaker location are 25 mH and 0.025 µF respectively. The value of resistor required to be connected across the breaker contacts which will give no transient oscillations, is
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The pu parameters for a 500 MVA machine on its own base are: Inertia, H = 20 pu; reactance X = 2 pu. The pu values of inertia and reactance on 100 MVA common base, respectively, are
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The sequence components of the fault current are as follows: I_{R1} = j1.5 pu, I_{R2} = j0.5 pu, I_{R0} = j1. The type of fault is
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Steady state stability of a power system is improved by
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For 800 MJ stored energy in the rotor at synchronous speed, what is the inertia constant H for a 50 Hz, four pole turbo generator rated 100 MVA, 11 kV?
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Mho relay is usually employed for protection of
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Lightning arresters are used for
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An over current relay, having a current setting of 125% connected to a supply circuit through a current transformer of ratio 400/5. The pick up value is
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Maximum power capacity of a transmission line can be increased by
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Two identical synchronous machines having same inertia constant are connected in parallel and swinging together. The effective inertia constant is 4 MJ/MVA. Then each machine has inertia constant of
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A generating station has a maximum demand of 100 MW, a load factor of 60% and a plant capacity factor of 50%. The reserve capacity of the plant is
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In thermal power stations, economiser will
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If a 500 MVA, 11 kV 3phase generator at 50 Hz feeds through a transfer impedance of (0+j0.605) Ω/phase, an infinite voltage also at 11 kV, then the maximum steady state power transfer on the base of 500 MVA and 11 kV is
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Which of the following is/are the disadvantages of phase modifiers?
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An alternator having an induced emf of 1.6 pu is connected to an infinite bus of 1 pu. If the bus bar has reactance of 0.6 pu and alternator has reactance of 0.2 pu, what is the maximum power that can be transferred?
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The rating of fuse wire is always expressed in
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Which one of the following relays has the capability of anticipating the possible major fault in a transformer?
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For which one of the following types of motors, is the equal area criterion for stability applicable?
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Lightning arresters are made up of which material?
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The inertia constant of 100 MVA, 50 Hz, 4 pole generator is 10 MJ/MVA. If the mechanical input to the machine is suddenly raised from 50 MW to 75 MW, the rotor acceleration will be equal to
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