MCQ Questions on Transmission & Distribution

251. Which of the following is not a type of insulator used in overhead transmission line?

(a) Rivet type
(b) Pin type
(c) Suspension type
(d) Strain type

252. String efficiency of a suspension insulator string is improved by

(a) longer cross arm
(b) using discs of different size
(c) using guard ring
(d) capacitive grading

253. Which of following is not the reason of using aluminum generally as bus bar? [UPPCL – 2015]

(a) It is cheaper
(b) It is solid
(c) It is corrosion resistance
(d) It is light weight

254. In three phase transmission line the volume of copper depends upon

(a) directly proportional to voltage and inversely to power factor
(b) inversely proportional to voltage and directly to power factor
(c) inversely proportional to voltage and power factor square
(d) directly proportional to voltage and power factor
[UPPCL – 2013]

255. In three phase transmission line the increment in line voltage results in

(a) increase in voltage drop
(b) increase in volume of copper
(c) decrease in line losses
(d) increase in line losses

256. On 132 kV transmission lines, some particular type of insulator is used. What is the name given to it? [UPRVUNL – 2014]

(a) Pin type insulators
(b) Disc type insulators
(c) Shackle type insulators
(d) Pin and shackle type insulators

257. What does 100% string efficiency imply? [UPRVUNL 2014]

(a) One of the insulator disc is shorted
(b) Shunt capacitance is 1 MF
(c) Potential across each disc is same
(d) Potential across each disc is zero

258. Which portion of the transmission system is more prone to faults?

(a) Alternator
(c) Overhead lines
(b) Transformer
(d) Underground cables

 259. Steel wire is used as

(a) overhead telephone wire
(b) earth wire
(c) core wire of ACSR
(d) all of these [IOF – 2014]

260. Overhead lines for power supply to tram cars are at a minimum height of

(a) 3 m
(b) 6 m
(c) 10 m
(d) 20 m

261. The usual spans with R.C.C. poles is

(a) 300 – 500 metres
(b) 80 – 100 meters
(c) 40 – 50 metres
(d) 60 – 100 metres

262. The mechanical test is done on which type of insulator? [UPSSC – 2015]

(a) shackle type
(b) Pin type
(c) Strain type
(d) Suspension type

263. If the height of transmission tower is increased, which of the following parameter is likely to change?

(a) Resistance
(b) Inductance
(c) Capacitance
(d) None of the above

264. Steel poles for transmission lines need protection against

(a) Termites
(b) Borer
(c) Corrosion
(d) All of the above

265. The corona take place in two current carrying conductors when

(a) conductors are close
(b) conductors are far
(c) potential difference is high
(d) only in d.c. transmission

266. In a distribution system, major cost is that of

(a) Earthing system
(b) Distribution transformer
(c) Conductors
(d) Meters

267. Which of following is used to support insulators on over head line

(a) cross-arm
(b) earth wire
(c) conductor
(d) phase plate

268. Which of the following steps is taken in order to reduce corona losses in AC transmission. [UPPCL – 2016]

(a) The gap between the conductors is increased
(b) Load is increased
(c) The gap between the conductors is decreased
(d) Load is reduced

269. Corona effect in transmission can be detected by

1. Hissing sound
2. Faint luminous glow which is blue in colour
3. Presence of ozone which is detected by odour

Which of these is/are correct?
(a) Only 1 and 2
(b) Only 1 and 3
(c) Only 2
(d) 1, 2, and 3 [UPPCL – 2016]

270. Which of the following is not a type of insulator used in overhead lines?

1. Pin type
2. Shackle type
3. Strain type
4. Suspension type

(a) None of these
(b) 2 and 4
(c) 3 and 4
(d) 1 and 3

271. The Ferranti effect is observed in

(a) DC lines
(b) AC lines
(c) Telephone lines
(d) Network lines

272. The phenomenon of rise in voltage at the receiving end of the open circuited or lightly loaded line is called the

(a) Ferranti effect
(b) Skin effect
(c) Induction
(d) None of the above

273. If the shunt capacitance is reduced then the string efficiency of an insulator is

(a) Increased
(b) Decreased
(c) Constant
(d) Independent of shunt capacitance

274. The steady current when flowing through the conductor, does not distribute uniformly, rather it has the tendency to concentrate near the surface of the conductor. This phenomenon is called

(a) Skin effect
(b) Eddy current
(c) Hysteresis loss
(d) None of the above

275. Inductance of bundled conductor line in comparison to inductance of the line with one conductor per phase is……..

(a) Not comparable
(b) More
(c) Less
(d) Equal

276. If AC corona losses in a transmission line is 0.6 kW, then for the same line voltage, approximate value of DC corona loss will be

(a) 1800 W
(b) 1.2 kW
(c) 0.2 kW
(d) 0.3 kW

277. Corona loss increases with

(a) increase in supply frequency and conductor size
(b) increase in supply frequency and reduction in conductor size
(c) decrease in supply frequency and conductor size
(d) decrease in supply frequency but increase in conductor size

278. The good effect of corona on overhead lines is to

(a) increase the line current carrying capacity
(b) increase the power factor
(c) reduce radio interference
(d) reduce steepness of surge fronts

279. Which of the following is not an insulation used for construction of cables ?

(a) Plastic
(b) Varnish cambric
(c) Paper
(d) Wood

280. Line insulators are made of

(a) Marble
(b) PVC
(c) Porcelain
(d) Mica

281. Aluminium is commonly used as conductor material in transmission lines compared to copper because

(a) It is more conductive
(b) It tensile strength is more
(c) It is costlier
(d) It is cheaper and lighter

282. The ………. faults are due to short circuits in conductors.

(a) Shunt
(b) Series
(c) Parallel
(d) Fixed

283. The sag of a transmission line depends upon

(a) Weight of conductor and direct proportional to span length
(b) Weight of conductor an inversely proportional to span length
(c) Weight of conductor and direct proportional to square of span length
(d) Weight of conductor and inversely proportional to square of span length

284. Find the approximate value of sag for a 66 kV line which has a span of 200 m between towers.

(a) 0.02 m
(b) 2 m
(c) 0.2 m
(d) 20 m

285. What is the approximate value of average resistance of a human body?

(a) 1 ΚΩ
(b) 5 ΚΩ
(c) 10 ΚΩ
(d) 15 ΚΩ

286. In a 3-phase, 4-wire system the neutral wire has the cross section

(a) the same cross section as the outer wires
(b) half the cross section as the outer wires
(c) twice the cross section as the outer wires
(d) 0.75 times the cross section of the conductor

287. Cables may be considered as…… of reactive power

(a) absorbers
(b) generators
(c) neither absorbers nor generators
(d) absorbers and generators both

288. Armouring in cable is used to protect the cable from

(a) voltage surge
(b) mechanical injury
(c) surge current
(d) increased voltage

289. The most commonly used insulation for cables in the low voltage to 33 kV range is

(a) paper insulation
(b) cross linked polyethylene
(c) vulcanized indian rubber
(d) poly vinyl chloride

290. Impregnated paper is used in an insulator

(a) In between the armature stamping
(b) High voltage cables
(c) Commutator
(d) H.T. Line

291. What is the main drawback of the underground transmission system compared to the overhead transmission system?

(a) Exposure to lightning
(b) Heavy initial cost
(c) Exposure to atmospheric hazards such as smoke, ice, wind
(d) Induction interference between power and communication circuits

292. The attenuation and propagation constants are applicable to

(a) Both underground cables and transmission lines
(b) Only transmission lines
(c) Only underground cables
(d) Neither transmission lines nor underground cables

293. An overhead line having a surge impedance of 400 ohms is connected in series with an underground cable having a surge impedance of 100 ohms. If the surge of 50 kV travels from the line towards the cable junctions, the value of transmitted voltage wave at the junction is

(a) 30 kV
(b) 20 kV
(c) 80 kV
(d) -30 kV

294. For LV applications (below 1 KV) …….. cables are used

(a) Plastic
(b) Paper Insulated
(c) Oil filled
(d) Signal core

295. High voltage cable core is covered by insulation after this what is the right sequence from core

(a) bedding, sheath, armouring, serving
(b) armouring, sheath, serving, bedding
(c) sheath, serving, bedding, armouring
(d) sheath, bedding, armouring, serving

296. Moisture ingress can be prevented by which of the following

(a) serving
(b) armouring
(c) vulcanized bitumin
(d) metal sheath

297. A.C.S.R. conductor having 7 steel strands surrounded by 25 aluminium conductors will be specified as

(a) 25/7
(c) 50/15
(b) 7/25
(d) 15/50

298. Least number of faults occur in

(a) Transmission lines
(b) Cables
(c) Switchgears
(d) Transformers

299. In a 60 km underground power transmission system, the best transmission system is

(a) single-phase AC system
(b) three-phase AC system
(c) High voltage AC voltage system
(d) DC transmission system

300. In terms of cost, overhead transmission line is better than underground transmission line in the field of

(a) insulation
(b) right of way
(c) visibility
(d) None of these