This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Conductor Materials”.
1. In stranded conductor of 6 layers, what will be the total number of individual wire?
Explanation: Standard conductors usually have the central wire around with there at successive layers of wires. For n layers the number of individual wire is 3n (n+1)+1. Where ‘n’ is number of layers.
2. A standard conductor have three layers of wire. What will be the diameter of stranded conductor if diameter of each strand is 5 mm?
a) 38 mm
b) 15 mm
c) 20 mm
d) 35 mm
Explanation: If the diameter of each strand is ‘d’ then diameter of the standard conductor will be (2n + 1)d. ‘n’ is number of layers.
3. What is the disadvantage of using Stranded Hard Drawn Copper for overhead transmission lines?
a) Low tensile strength
b) Due to electrolytic troubles
d) High cost
Explanation: Hard Drawn Copper have good tensile strength, does not corrodes in normal atmosphere and is not subject to electrolytic troubles. Owing to the difficulty of importing copper due to lack of foreign exchange in our country, cost of copper is higher than aluminium. The trend now days is to use aluminium in place of copper.
4. Which of the following conductors are most suitable for short lines supplying rural areas and operating at voltage of about 11 Kv?
a) Hard Drawn Copper Conductor
b) ACSR Conductor
c) Galvanized steel
d) Phosphor Bronze
Explanation: Galvanized steel have great tensile strength and so it can be used for extremely long spans,or for short line section exposed to normally high stresses due to climatic conditions. These conductors are most suitable for lines supplying rural areas and operating at voltages of about 11 Kv where cheapness is the main consideration.
5. Which of the following conductive material will be preferred when harmful gases such as ammonia are present in atmosphere?
a) Cadmium copper
b) Phosphor bronze
c) Galvanized steel
Explanation: When harmful gases such as Ammonia are present in atmosphere and the spans are extremely long, phosphor bronze is most suitable material for an overhead line conductor for such situation.
6. What is the amount of Corona losses in ACSR conductors in comparison to copper conductors?
d) No Corona loss
Explanation: The ACSR conductors has a largest diameter than any other type of conductor of same resistance, so corona losses are low in ACSR conductors.
7. What is the advantage of cadmium copper over hard drawn copper?
a) Higher conductivity
b) Higher tensile strength
c) Low cost
d) Low conductivity
Explanation: Addition of 1 or 2% of cadmium in copper increases the tensile strength by about 40% and reduces the conductivity only by 17% below that of pure copper. However, cadmium copper is costlier than pure copper, its use will be economical for a line with long spans and small cross section.
8. In extra High Voltage lines, which conductor material is used for ground wire provided above the line conductors for protection against lightning?
a) Hard drawn copper
b) Cadmium copper
c) Stranded galvanized steel
Explanation: Due to very poor conductivity, about 30% of copper and higher eddy current and hysteresis losses. Application of galvanized steel wire is limited to telecommunication lines stay wire Earth wire and guard wires. Stranded galvanized steel wires are used as guy wires and earth wires.
9. Which of the following conductor is needed to use with shortest span?
a) ACSR Conductors
b) All Aluminium Conductors
c) Hard Drawn Copper Conductors
d) Cadmium Copper Conductors
Explanation: All aluminium conductors have low tensile strength. Linear coefficient of expansion of Aluminium is 1.4 times that of copper and so sag is greater in aluminium wires. Due to these characteristics, aluminium stranded conductors are mainly used for low voltage distribution overhead lines having shorts spans of up to 65 m.
10. Which of the following wire is used as stay wire?
a) All Aluminium Conductors
b) Standard Galvanized Steel Conductors
c) Cadmium Copper Conductors
d) Phosphor Bronze Conductors
Explanation: Stay wires are used for supporting poles and towers. Standard galvanized steel conductors have great tensile strength and superior mechanical properties. So standard galvanized steel wires are widely used as stay wire and earth wire.
Sanfoundry Global Education & Learning Series – Power Systems.
To practice all areas of Power Systems, here is complete set of 1000+ Multiple Choice Questions and Answers.