Portion of the conductor near the surface carries less current and core of the conductor carries more current
Portion of the conductor near the surface carries more current and the core of the conductor carries less current
Current flows through the half cross-section of the conductor
None of the above
Answer.2. Portion of the conductor near the surface carries more current and the core of the conductor carries less current
Explanation:
In string effect due to eddy current, the portion of the conductor near the surface carries more current and the core of the conductor carries less current
Ques 52. A circuit is disconnected by isolators when
Line is on full load
Circuit breaker is not open
There is no current in the line
Line is energized
Answer.3. There is no current in the line Explanation:
In electrical engineering, a disconnector, disconnect switch, or isolator switch is used to ensure that an electrical circuit is completely de-energized for service or maintenance.
Ques 53. Current rating is not necessary in case of
Circuit breaker
Isolator
Load break switch
None of the above
Answer.2. Isolator
Explanation:
Isolator operates under no-load condition. They are not equipped with any arch-quenching device and don’t have any specified current breaking capacity or current making capacity.
Isolators are employed only for isolating the circuit when the current has already been interrupted. They ensure that the current is not switched into the circuit until the fault has been fixed.
Ques 54. In a substation, the following equipment is not installed
Exciters
Series capacitors
Shunt reactors
Voltage transformers
Answer.1. Exciter
Explanation:
To produce power electrical conductors are to be moved in a strong magnetic field. Permanent magnets have very limited strength. So there are electromagnets in the generator. This needs DC supply to produce magnetism. Supplying DC power to the magnetic coil is called excitation.
The exciter is used in generating station, therefore, it is not required in the substation.
Ques 55. The voltage drop, for constant voltage transmission, is compensated by installing
Capacitors
Synchronous motors
Inductors
All of the above
Answer.2. Synchronous motor
Explanation:
Synchronous motor sometimes runs on no-load with over-excitation for improving the voltage regulation of a transmission line. Such an over-excited synchronous motor is called the synchronous condenser or synchronous capacitor.
Ques 56. The use of strain type insulators is made where the conductors are
Dead End
Road Crossing
Intermediate anchor towers
All of the above
Answer.4. All of the above
Explanation:
Strain Type Insulator
Strain type insulators are used for handling the mechanical stress at the angle position of the line i.e Dead end, intermediate anchor tower, corner, sharp curve.
Ques 57. The current drawn by the line due to corona losses is
Non-sinusoidal
Triangular
Square
Sinusoidal
Answer.1. Non-sinusoidal
Explanation:
The current drawn by the line due to corona is non-sinusoidal therefore non-sinusoidal voltage occurs in the line.
This non-sinusoidal current and voltage cause inductive interference with the neighboring communication line.
Ques 58. Pin type insulators are generally not used for voltages beyond
22 kV
33 kV
11 kV
1 kV
Answer.2. 33 kV
Explanation:
Pin type insulators are used for the transmission and distribution of electric power at voltages up to 33 kV.
Beyond operating voltage of 33 kV, the pin type insulators become too bulky and hence uneconomical.
Ques 59. For transmission of power over a distance of 200 km, the transmission voltage should be
66 kV
132 kV
11 kV
33 kV
Answer.2. 132 kV
Explanation:
In this case, the line length is more than 160 Km, therefore, it is a long transmission line and the line voltage requires is greater than 100 kV.
Ques 60. Which of the following equipment, for regulating the voltage in the distribution feeder, will be most economical?
Static condenser
Tap changing transformer
Synchronous condenser
Shunt capacitor
Answer.4. Shunt capacitor
Explanation:
The synchronous condenser is most suitable for power factor correction but it is expensive therefore it is used for the high-voltage transmission line.
The most economical way of regulating the voltage within the permissible limit is to use shunt capacitor.
Shunt capacitors are installed on the feeder and substation bus to achieve the economical power factor.
