Virtual Labs

Load Transfer from one Feeder to other during Transformer Maintenance

In a transformer, if N2 is number of secondary winding N1 is the number of primary winding then, if (N2/N1) ratio is greater than 1.It is called as ________

a: Step down transformer Explanation

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b: Step up transformer Explanation

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c: Isolation transformer Explanation

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d: All Explanation

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In a transformer, if N2 is number of secondary winding N1 is the number of primary winding then, if (N2/N1) ratio is equal to 1.It is called as ________

a: Step down transformer Explanation

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b: Step up transformer Explanation

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c: Isolation transformer Explanation

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d: All Explanation

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The tap changing control equipment includes ________

a: Control and paralleling equipment Explanation

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b: Line drop compensator equipment used along with the current transformer to provide voltage control at a point remote from the measuring point Explanation

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c: Automatic voltage regulating relay Explanation

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d: Al Explanation

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16 step tap changes provide ________ voltage change in each step.

a: 2% Explanation

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b: 1% Explanation

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c: 5/4% Explanation

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d: 4/5% Explanation

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In case of, OFF circuit taps, the transformer must be _________ before the tap changer mechanism is operated.

a: Energized Explanation

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b: De-energized Explanation

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c: Both Energized and De-energized Explanation

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d: None Explanation

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Advantage of using instrument Transformer is

a: Standard rated instruments may be used easily Explanation

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b: It provides safety for operating personal Explanation

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c: Both Standard rated instruments may be used easily and It provides safety for operating personal Explanation

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d: None Explanation

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Potential transformers are made with

a: Low quality icon core operating at very low flex density so that the magnetizing current may be large Explanation

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b: High quality icon core operating at very high flex density so that the magnetizing current may be large Explanation

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c: High quality icon core operating at very high flex density so that the magnetizing current may be very small Explanation

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d: High quality icon core operating at very low flex density so that the magnetizing current may be very small Explanation

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A high magnitude alternating current can be measured by a combination of _________ and_________.

a: A high magnitude alternating current can be measured by a combination of _________ and_________. Explanation

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b: Current transformer and high range ammeter Explanation

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c: Current transformer and low range ammeter Explanation

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d: None Explanation

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The current transformer ratio is not equal to the ratio of secondary to primary turns.

a: The above statement is false Explanation

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b: The above statement is false, because of the effect of magnetizing current Explanation

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c: The above statement is true, because of the effect of magnetizing current Explanation

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d: None Explanation

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A current transformer must never be operated on open circuit for

a: There will be no secondary m.m.f. and since the primary current (and m.m.f.) is fixed, the core flux will increase enormously. This will cause large amount of eddy current and hysteresis losses and the resulting high temperature may damage the insulation or even the core Explanation

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b: As the secondary side is open, a very high voltage will be induced in the multi-turn secondary and this high voltage is dangerous to both life and to the insulation Explanation

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c: There will be no secondary m.m.f. and since the primary current (and m.m.f.) is fixed, the core flux will increase enormously. This will cause large amount of eddy current and hysteresis losses and the resulting high temperature may damage the insulation or even the core and As the secondary side is open, a very high voltage will be induced in the multi-turn secondary and this high voltage is dangerous to both life and to the insulation Explanation

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d: None Explanation

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_______ is used to make sure that an electrical circuit can be completely de-energized for service or maintenance.

a: Circuit breaker Explanation

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b: Isolator Explanation

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c: Fuse Explanation

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d: None Explanation

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Isolators are

a: Manually operated Explanation

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b: Motorized Explanation

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c: Both Manually operated and Motorized Explanation

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d: None Explanation

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Characteristic of high voltage rating Circuit Breaker :-

a: High reliability electrically and mutually Explanation

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b: Capability of interrupting capacitive and inductive circuits and fault currents of all values within their rating Explanation

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c: Slower time response Explanation

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d: Both High reliability electrically and mutually and Capability of interrupting capacitive and inductive circuits and fault currents of all values within their rating Explanation

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In oil circuit breaker (O.C.B) the range exists between

a: 75MVA at 2.5 kV and 50000MVA at 250kV Explanation

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b: 7.5MVA at 2.5 kV and 50000MVA at 250kV Explanation

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c: 250MVA at 2.5 kV and 5000MVA at 250kV Explanation

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d: 25MVA at 2.5 kV and 5000MVA at 250kV Explanation

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In SF6 Circuit breaker

a: No risk of fire Explanation

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b: No reduction of dielectric strength Explanation

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c: Current chopping tendency is minimized Explanation

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d: All Explanation

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The voltage across the contacts during the arcing period is known as

a: Recovery voltage Explanation

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b: Restriking voltage Explanation

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c: Arc voltage Explanation

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d: All Explanation

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The peak value of current (including the DC component) during first cycle of current wave after the closure of Circuit breaker is known as __________

a: Breaking capacity Explanation

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b: Making capacity Explanation

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c: Short-time capacity Explanation

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d: None Explanation

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__________ of a Circuit breaker depends upon its ability to withstand the temperature rise and the electromagnetic force effects.

a: Breaking capacity Explanation

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b: Making capacity Explanation

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c: Short-time capacity Explanation

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d: None Explanation

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The major advantage of single bus-bar system is that fault on one part of the bus�bar or system does not completely shut down the whole station.

a: False Explanation

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b: True Explanation

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Bus bar can be arranged in __________

a: Single bus-bar system Explanation

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b: Double bus-bar system with sectionalisation Explanation

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c: Both Single bus-bar system and Double bus-bar system with sectionalisation Explanation

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d: None Explanation

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_________ is a device which is used to switch from one bus to the other without any interruption in power supply and without creating hazardous arcs.

a: Isolator Explanation

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b: Circuit breaker Explanation

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c: Bus coupler Explanation

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d: Any of them Explanation

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