MCQ Questions on Transmission & Distribution

101. Transmission lines connect

(a) Generating station to a switching station/step down transformer station
(b) Step down transformer station to service transformer banks
(c) Distribution transformer to consumer premises
(d) Service points to consumer premises

102. A 3 phase 4 wire system is commonly used for

(a) Primary distribution
(b) Secondary distribution
(c) Primary transmission
(d) Secondary transmission

103. The highest transmission voltage in India is

(a) 765 kV
(b) 400 kV
(c) 220 kV
(d) 132 kV

104. The surge impedance of a 400 km long, over head line is 400Ω. For 200 km length of the same line, the surge impedance will be

(a) 200 Ω
(b) 800 Ω
(c) 400 Ω
(d) 100 Ω

105. Transmission lines are transposed to

(a) reduce copper loss
(b) reduce skin effect
(c) prevent interference with neighbouring telephone lines
(d) prevent short circuit between any two lines

106. The spacing between the conductors is increased the capacitance, inductance, resistance of a transmission line will be

(a) increase, increase, increases
(b) decreases, increases, increases
(c) decreases, increases, constant
(d) increases, decreases, constant

107. In a short line, the regulation at leading power factor is

(a) IR cos φ_r+ IX sin φ_r
(b) IX coso φ_r + IR sinφ_r
(c) IR cos φ_r– IX sin φ_r
(d) IX coso φ_r – IR sinφ_r

108. Skin effect is affected by the following factor

(a) supply frequency
(b) radius of the conductor
(c) type of supply system
(d) all the above

109. The minimum permissible value of earth resistance at small substation is

(a) 8 Ω
(b) 5 Ω
(c) 0.5 Ω
(d) 2 Ω

110. The type of cable joint for large size cable

(a) Tee joint
(c) Ferrul joint
(b) Married joint
(d) Britannia Joint

111. The voltage phasor of a circuit is 10 ∠15° V and current phasor is 2 ∠-45° A. The reactive power in the circuit will be

(a) 17.32 VAR
(b) 10 √2 VAR
(c) 8.66 VAR
(d) None of these [UPPCL JE – 2007]

112. Sag of conductors between two electric poles can be determined by

(a) WL²/8T
(b) WL²/16T
(c) WL²/2T
(d) WL²/ T
Where
W = Weight per unit length of conductor in kg/m
L = Distance between two poles in metre
T = Tension in conductors in kg-m

113. The economic size of a conductor in transmission and distribution lines of electric power is decided by

(a) Ohm’s law
(b) Kelvin’s law
(c) Kirchhoff’s law
(d) Faraday’s law [UPPCL JE – 2007]

114. In an AC transmission line difference in phase of voltage at two ends of the line is due to

(a) System voltage
(b) Insulators
(c) Resistance of line
(d) Reactance of line

115. If 5000 kW power is transmitted at 220 kV in place of 11 kV, reduction in the value of electric current will be

(a) 90%
(b) 95%
(c) 5%
(d) 10%

116. In long AC transmission lines, the receiving end voltage becomes greater than sending end voltage at light load or no load operation. This is due to

(a) Ferranti effect
(b) Skin effect
(c) Proximity effect
(d) Corona effect [UPPCL JE – 2007]

117. For extra high voltage ac transmission lines, conductors used are

(a) All aluminium
(c) AAAC
(b) All steel
(d) ACSR
[UPPCL JE – 2007]

118. Which of the following relations is true for long transmission line?

(a) V_s = AV_R – BI_R
(b) V_s = BV_R + AI_R
(c) V_s = AV_R + BI_R
(d) V_s = BV_R – AI_R [UPPCL JE 2007]

119. Which of the following is used for power factor improvement in transmission line?

(a) Three phase induction motor
(b) An overexcited three phase synchronous motor running on no load
(c) Three phase AC series motor
(d) Choke [UPPCL JE – 2007]

120. The bundled conductor in EHV transmission line system provides

(a) increased inductance
(b) reduced capacitance
(c) increased capacitance
(d) increased voltage gradient [UPPCL JE – 2007]

121. Corona losses in transmission lines are minimized when

(a) conductor size is reduced.
(b) smooth conductor is used.
(c) sharp points are provided in the line.
(d) current density in conductor is reduced.

122. The power loss in a transmission line depends on

(a) current in the line.
(b) resistance of the line.
(c) length of the line.
(d) All of the above [UPPCL JE – 2007]

123. The main consideration for operating transmission line at high voltage is

(a) to increase efficiency
(b) to reduce power loss
(c) to increase power transmission capability
(d) All of the above [UPPCL JE – 2007]

124. The presence of earth in case of overhead transmission line

(a) increases capacitance
(b) increases inductance
(c) decreases capacitance
(d) decreases inductance [UPPCL JE 2007]

125. Effect of increase in temperature in an overhead transmission line is

(a) to increase stress and length both
(b) to decrease stress and length both
(c) to decrease stress and increase length
(d) None of the above [UPPCL JE – 2007]

126. Super conducting materials can be used for

(a) ore refining.
(b) magnetic levitation in high speed trains.
(c) medical resonance imaging.
(d) All of the above [UPPCL JE – 2007]

127. Which of the following is used to maintain constant voltage in the feeder circuit?

(a) Induction regulator
(b) Booster
(c) Tap Changer
(d) Phase advancers [UPPCL JE – 2016]

128. In earthed neutral system, the magnitude of transient voltage is:

(a) Zero
(c) Medium
(b) Very small
(d) Very high
[UPPCL JE 2016]

129. Corona discharge is generally in colour.

(a) blackish
(b) bluish
(c) yellowish
(d) brownish [UPPCL JE – 2016]

130. Screened cables can be used for voltages

(a) Upto 11 kV
(b) 11 kV to 33 kV
(c) 33 kV to 66 kV
(d) 66 kV to 132 kV [UPPCL JE – 2016]

131. For overhead transmission line, the magnitude of surge impedance is close to

(a) 4 – 6 Ω
(b) 50 – 100 Ω
(c) 400 – 600 Ω
(d) 700 – 1000 Ω [UPPCL JE – 2016]

132. According to the IS code, the colour of earth wire is usually

(a) Red
(b) Green
(c) Yellow
(d) Black [UPPCL JE – 2016]

133. Which of the following is an effect of non-uniform current distribution in a conductor? [UPPCL JE 2016]

(a) Ferranti effect
(b) Skin effect
(c) Proximity effect
(d) Skin effect or Proximity effect

134. Which of the following is used to make bus bars and transmission line conductors?

(a) Lead
(b) Aluminium
(c) Nichrome
(d) Cadmium [UPPCL JE – 2016]

135. Core is insulated by …………. in a belted cable. [UPPCL JE 2016]

(a) Impregnated paper
(b) VIR
(c) PVC
(d) Gutta Percha

136. Corona losses in DC transmission is

(a) Minimum
(b) High
(c) Infinite
(d) Moderate [UPPCL JE – 2016]

137. The 400 V distribution lines are commonly known as

(a) Feeder
(b) Service mains
(c) Sub station
(d) Distributors [UPPCL JE – 2016]

138. Low voltage cable have operating voltage upto

(a) 1 kV
(b) 11 kV
(c) 22 kV
(d) 33 kV [UPPCL JE – 2016]

139. Loss in transmission line is 20 MW and is loaded at 110 kV. If load is 200 MVA and length is 100 km then resistance per km is

(a) 8.06 ohm
(b) 6.05 ohm
(c) 0.806 ohm
(d) 0.0605 ohm [UPPCL AE – 2016]

140. To increase power transfer capability of a long transmission line, we should

(a) Increase line resistance
(b) Increase transmission voltage
(c) Decrease line reactance
(d) Increase transmission voltage and decrease line reactance

141. Installation of capacitors at suitable locations and of optimum size in a distribution system results in

1. No change in voltage regulation
2. Reduction in distribution power losses
3. Increase of kVA rating of distribution transformers.

(a) Both 1 and 2 are correct
(b) Only 2 is correct
(c) Only 3 is correct
(d) Both 1 and 3 are correct. [UPPCL AE – 2016]

142. The corona loss for 400 kV, 50 Hz system is 3kW/km per phase. What is the corona loss if the system operates for DC with same configuration? [UPPCL AE – 2016]

(a) 3 kW/km per phase
(b) 9 kW/km per phase
(c) 1 kW/km per phase
(d) 1.5 kW/km per phase

143. Over head transmission lines are provided with earth wires

1. To protect the transmission line from direct lightening strike.
2. To protect the transmission line insulation from the indirect lightning strike.
3. To provide path for neutral current.

Which of these statement(s) is/are correct?
(a) Only 2 and 3
(b) Only 1
(c) Only 3
(d) Both 1 and 3

144. Surge impedance loading of a transmission line can be increased by

1. Decreasing its voltage level
2. Reducing the length of the line

(a) Only 2 is correct
(b) Only 1 is correct
(c) Both 1 and 2 is correct
(d) Both 1 and 2 is incorrect

145. The corona loss in a particular system at 50 Hz is 3kW/km per phase then corona loss at 60 Hz in kW/km per phase is

(a) 0
(b) 1.13
(c) 3.4
(d) 3.9 [UPPCL AE 2016]

146. Normal belted cables can be used for voltages

(a) 11 kV
(b) 11 kV – 33 kV
(c) 33 kV – 66 kV
(d) 66 kV – 132 kV

147. Which of the following statement is true?

(i) transmission lines is not used for communication
(ii) transmission lines are classified only as per their construction
(iii) corona losses are less in DC than in AC system
(iv) cables are used for DC supply only
(a) (i) and (ii)
(b) (ii) and (iii)
(c) only (iii)
(d) only (iv)

148. In HVDC transmission there are predominant ………. harmonics on d.c. side and ………… harmonics on a.c. side of converters. [UPPCL AE – 2016]

(a) Current, voltage
(b) Voltage, frequency
(c) Current, frequency
(d) Voltage, current

149. Depending upon the voltage to be handled, switchgear may be broadly classified into

(a) Outdoor type
(b) Indoor type
(c) Both Outdoor type and Indoor
(d) None of these [UPPCL JE – 2018]