Free Power Systems MCQs with Answers
334 Power Systems MCQs from Electrical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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334 questions · page 15 of 17
- A. 6.6 kV
- B. 11 kV
- C. 33 kV
- D. 66 kV
- E. 132 kV
Explanation: In the usual cable-voltage classification, extra-high-tension cables operate up to 66 kV.
Correct answer: 66 kV- A. 3.3 kV
- B. 6.6 kV
- C. 11 kV
- D. 33 kV
Explanation: Supertension cables are commonly classified for voltages up to 33 kV. The 11 kV value belongs to the usual high-tension cable range, not…
Correct answer: 33 kV- A. l.lkV
- B. 3.3kV
- C. 6.6kV
- D. llkV
Explanation: The conventional classification places high-voltage cables up to 11 kV.
Correct answer: llkV- A. Increase of short-circuit current of the system
- B. Availability of steady voltage at all loads at the line terminals
- C. Possibility of better protection for the line due to possible use of higher terminal reactants
- D. Improvement of power factor at times of moderate and heavy loads
- E. Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission
Explanation: A constant-voltage transmission system requires low line impedance, which causes a larger short-circuit current when a fault occurs.
Correct answer: Increase of short-circuit current of the system- A. surge impedance of the line
- B. conductance of the line
- C. regulation of the line
- D. none of the above
Explanation: The quantity √(Z/Y), where Z is series impedance and Y is shunt admittance per unit length, is the surge or characteristic impedance of a…
Correct answer: surge impedance of the line- A. Seeback effect
- B. Ferranti effect
- C. Raman effect
- D. none of the above
Explanation: The Ferranti effect is the rise of receiving-end voltage above sending-end voltage when a long line is open-circuited or lightly loaded.
Correct answer: Ferranti effect- A. a long line
- B. a medium line
- C. a short line
- D. any of the above
Explanation: Transmission lines longer than roughly 250 km are treated as long lines because distributed capacitance and inductance must be considered.
Correct answer: a long line- A. Resistance
- B. Inductance
- C. Capacitance
- D. All of the above
Explanation: Resistance, inductance, capacitance, and conductance are the distributed constants of a transmission line.
Correct answer: All of the above- A. Size of the conductor
- B. Shape of the conductor
- C. Surface condition of the conductor
- D. All of the above
Explanation: Corona depends on conductor size, conductor shape, and surface condition because these factors affect the electric-field intensity at the…
Correct answer: All of the above- A. 40-50 meters
- B. 60-100 meters
- C. 80-100 meters
- D. 300-500 meters
Explanation: R.C.C. poles are stronger and can support longer spans than ordinary wooden poles.
Correct answer: 80-100 meters- A. stay wire
- B. earth wire
- C. structural components
- D. all of the above
Explanation: Galvanised steel resists atmospheric corrosion while providing good mechanical strength, so it is used for stay wires, earth wires and…
Correct answer: all of the above- A. Copper
- B. Aluminium
- C. Steel
- D. Tungsten
Explanation: Copper and aluminium are used as electrical conductors, while steel is used where mechanical strength is important, such as in…
Correct answer: Tungsten- A. from 2 to 5 years
- B. 10 to 15 years
- C. 25 to 30 years
- D. 60 to 70 years
Explanation: Creosote or preservative treatment protects wooden poles against moisture, fungi and insects, extending their service life to roughly 25…
Correct answer: 25 to 30 years- A. Kelvin's law
- B. Ohm's law
- C. Kirchhoffs law
- D. Faraday's law
- E. none of the above
Explanation: Kelvin's law states that the most economical conductor size occurs when annual capital charges due to interest and depreciation equal the…
Correct answer: Kelvin's law- A. 11 kV
- B. 33 kV
- C. 66 kV
- D. 400 kV
Explanation: Overhead lines are suitable for very high voltages because air provides insulation at comparatively low cost and the conductors can be…
Correct answer: 400 kV- A. 440 V
- B. 11 kV
- C. 33 kV
- D. 66 kV
Explanation: In conventional power-system comparisons, underground cables are generally considered uneconomical and difficult to operate above about 66…
Correct answer: 66 kV- A. Distributors
- B. Service mains
- C. Feeders
- D. None of the above
Explanation: Service mains are the conductors running from the distribution line or distributor to the consumer's terminals.
Correct answer: Service mains- A. Overhead system
- B. Underground system
- C. Both A. and (b)
- D. None of the above
Explanation: Electrical power can be transmitted by overhead lines or by underground cables.
Correct answer: Both A. and (b)- A. Current will flow to earth
- B. Supply voltage will drop
- C. Supply voltage will increase
- D. No current will flow in the conductor
- E. None of the above
Explanation: When a live conductor contacts earth, a fault current flows from the conductor into the ground and returns through the earthing path or…
Correct answer: Current will flow to earth- A. resistivity of conductor material increases
- B. permeability of conductor material increases
- C. diameter increases
- D. frequency increases
Explanation: Skin effect becomes weaker when resistivity increases because the skin depth is proportional to the square root of resistivity.
Correct answer: resistivity of conductor material increases