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Maharashtra HSC Power Distribution Lineman (NSQF) study materials
Maharashtra HSC Power Distribution Lineman (NSQF) study resources

Maharashtra HSC Power Distribution Lineman (NSQF) practice questions

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Question 1Electrical Fundamentals and Basic Circuit Theory

A lineman connects three 100 W lamps rated 230 V in parallel across a 230 V supply. What is the total power drawn by the three lamps?

  1. 33 W
  2. 900 W
  3. 300 W Correct answer.
  4. 100 W

Explanation

In a parallel circuit every branch receives the full supply voltage, so each lamp draws its rated 100 W at 230 V. Total power is the sum of branch powers, giving 100 + 100 + 100 = 300 W.

Question 2Electrical Fundamentals and Basic Circuit Theory

Which instrument is connected in series with a distribution circuit to measure the current flowing through it?

  1. Megger
  2. Ammeter Correct answer.
  3. Frequency meter
  4. Voltmeter

Explanation

An ammeter must carry the circuit current, so it is inserted in series and kept at very low resistance to avoid disturbing the circuit. A voltmeter is connected in parallel across the points whose potential difference is wanted.

Question 3Electrical Fundamentals and Basic Circuit Theory

What is the standard supply frequency of the low-voltage AC distribution system used in Maharashtra?

  1. 25 Hz
  2. 60 Hz
  3. 50 Hz Correct answer.
  4. 100 Hz

Explanation

India, including Maharashtra, generates and distributes alternating current at 50 Hz, meaning the voltage completes 50 cycles per second. This frequency is fixed by the grid and is the basis for motor speed and transformer design.

Question 4Electrical Fundamentals and Basic Circuit Theory

A 230 V single-phase circuit carries a current of 10 A at unity power factor. What is the power consumed?

  1. 23 W
  2. 2300 W Correct answer.
  3. 23000 W
  4. 230 W

Explanation

For a single-phase circuit, power equals voltage multiplied by current multiplied by the power factor. At unity power factor, 230 V times 10 A gives 2300 W.

Question 5Electrical Fundamentals and Basic Circuit Theory

Which material is used for the conductor of a distribution line primarily because of its high electrical conductivity?

  1. Porcelain
  2. Copper Correct answer.
  3. Bakelite
  4. Vulcanised rubber

Explanation

Copper has very low resistivity, so it carries current with small voltage drop and low heating for a given cross-section. The other listed materials are insulators used for supporting or covering conductors, not for carrying current.

Question 6Electrical Fundamentals and Basic Circuit Theory

In a series circuit containing two resistors of 4 ohm and 6 ohm, what is the equivalent resistance?

  1. 2.4 ohm
  2. 4 ohm
  3. 6 ohm
  4. 10 ohm Correct answer.

Explanation

In a series circuit the same current passes through each element, so resistances simply add. Adding 4 ohm and 6 ohm gives an equivalent resistance of 10 ohm.

Question 7Electrical Fundamentals and Basic Circuit Theory

What does the term 'power factor' express in an AC distribution circuit?

  1. The ratio of active power to reactive power
  2. The ratio of voltage to current
  3. The ratio of resistance to impedance squared
  4. The ratio of active power to apparent power Correct answer.

Explanation

Power factor is the cosine of the phase angle between voltage and current, which equals active power divided by apparent power. A value of one means all the apparent power is being converted into useful work.

Question 8Electrical Fundamentals and Basic Circuit Theory

A 12 V battery supplies 3 A to a resistive load. What is the resistance of the load?

  1. 36 ohm
  2. 15 ohm
  3. 4 ohm Correct answer.
  4. 0.25 ohm

Explanation

Ohm's law states that resistance equals voltage divided by current. Dividing 12 V by 3 A gives 4 ohm.

Question 9Electrical Fundamentals and Basic Circuit Theory

Two resistors of 6 ohm and 3 ohm are connected in parallel. What is their combined resistance?

  1. 2 ohm Correct answer.
  2. 4.5 ohm
  3. 18 ohm
  4. 9 ohm

Explanation

For two resistors in parallel the product over sum rule gives (6 x 3)/(6 + 3) ohm. This equals 18/9, which is 2 ohm, a value smaller than either branch as expected.

Question 10Electrical Fundamentals and Basic Circuit Theory

A coil draws 5 A from a 230 V supply while dissipating 920 W. What is the power factor of the circuit?

  1. 1.0
  2. 0.6
  3. 0.8 Correct answer.
  4. 1.25

Explanation

Apparent power is 230 V times 5 A, which equals 1150 VA. Power factor is active power divided by apparent power, so 920 divided by 1150 gives 0.8.

Question 11Electrical Fundamentals and Basic Circuit Theory

Why is alternating current preferred over direct current for bulk power distribution in the Maharashtra grid?

  1. It flows only in one direction
  2. It requires no protective devices
  3. It eliminates reactive power losses
  4. Voltage can be changed easily by transformers Correct answer.

Explanation

Transformers can raise or lower AC voltage with high efficiency, allowing transmission at high voltage to reduce current and line loss. This easy transformation is the main reason AC is used for bulk distribution.

Question 12Electrical Fundamentals and Basic Circuit Theory

A 230 V, 1000 W immersion heater is operated for 4 hours. What energy does it consume?

  1. 0.25 kWh
  2. 40 kWh
  3. 4 kWh Correct answer.
  4. 1 kWh

Explanation

Energy in kilowatt-hours equals power in kilowatts multiplied by time in hours. One kilowatt for four hours gives 4 kWh, which is the basis for domestic billing.

Question 13Electrical Fundamentals and Basic Circuit Theory

What is the effect on the total resistance of a circuit when an additional resistor is connected in parallel with an existing resistor?

  1. The total resistance increases
  2. The total resistance decreases Correct answer.
  3. The total resistance doubles
  4. The total resistance stays the same

Explanation

Adding a parallel path gives the current an extra route, so the equivalent resistance must fall below the smallest branch resistance. The reciprocal formula confirms that each added branch increases total conductance.

Question 14Electrical Fundamentals and Basic Circuit Theory

A conductor of resistance 20 ohm carries 5 A. What is the voltage drop along the conductor?

  1. 25 V
  2. 100 V Correct answer.
  3. 4 V
  4. 0.25 V

Explanation

Ohm's law gives voltage as current multiplied by resistance. Multiplying 5 A by 20 ohm yields a voltage drop of 100 V.

Question 15Electrical Fundamentals and Basic Circuit Theory

In a single-phase AC circuit, which quantity is measured in volt-amperes reactive?

  1. Active power
  2. Power factor
  3. Reactive power Correct answer.
  4. Apparent power

Explanation

Reactive power, the component that shuttles energy to and from inductive or capacitive elements, is expressed in volt-amperes reactive. Active power is in watts and apparent power is in volt-amperes.

Question 16Electrical Fundamentals and Basic Circuit Theory

A fuse in a distribution board is rated 10 A. Which condition will cause it to operate?

  1. A voltage of 240 V across the circuit
  2. A power factor of 0.95
  3. A frequency rise to 51 Hz
  4. A sustained current of 15 A through it Correct answer.

Explanation

A fuse operates on the heating effect of current and melts when the current exceeds its rating for sufficient time. A sustained 15 A through a 10 A fuse will melt the element and break the circuit.

Question 17Electrical Fundamentals and Basic Circuit Theory

Three identical resistors of 9 ohm each are connected in parallel. What is the equivalent resistance?

  1. 27 ohm
  2. 9 ohm
  3. 3 ohm Correct answer.
  4. 1 ohm

Explanation

For n identical resistors in parallel the equivalent resistance is one resistance divided by n. Dividing 9 ohm by three gives 3 ohm.

Question 18Electrical Fundamentals and Basic Circuit Theory

Why is a megger used on a newly laid underground distribution cable before energising it?

  1. To confirm the phase sequence of the supply
  2. To measure the load current the cable will carry
  3. To verify that insulation resistance is above the acceptable minimum Correct answer.
  4. To check the supply frequency at the feeder

Explanation

A megger applies a high DC test voltage and measures insulation resistance, revealing moisture, damage or contamination before the cable is energised. Good insulation resistance indicates the cable is safe to charge.

Question 19Electrical Fundamentals and Basic Circuit Theory

A 230 V circuit has an impedance of 46 ohm and a resistance of 23 ohm. What is its reactance?

  1. About 51.5 ohm
  2. 46 ohm
  3. 23 ohm
  4. About 39.8 ohm Correct answer.

Explanation

Impedance, resistance and reactance form a right triangle, so reactance equals the square root of impedance squared minus resistance squared. The square root of 2116 minus 529 is the square root of 1587, about 39.8 ohm.

Question 20Electrical Fundamentals and Basic Circuit Theory

Why does a distribution transformer secondary use a star connection with a neutral brought out?

  1. To reduce the insulation level of the primary winding
  2. To provide both phase and neutral voltages for single-phase and three-phase consumers Correct answer.
  3. To eliminate the need for earthing at the substation
  4. To increase the frequency of the output supply

Explanation

A star-connected secondary with a neutral point allows line-to-line three-phase supply and line-to-neutral single-phase supply from the same transformer. The neutral also provides a return path that can be earthed for safety.

Question 21Electrical Fundamentals and Basic Circuit Theory

A 100 W lamp and a 60 W lamp, both rated 230 V, are connected in series across 230 V. Which statement about the circuit is correct?

  1. The 60 W lamp carries more current than the 100 W lamp
  2. Both lamps carry the same current but the 60 W lamp drops more voltage Correct answer.
  3. Both lamps drop 230 V each
  4. The 100 W lamp carries more current than the 60 W lamp

Explanation

In a series circuit the current is common to both lamps, so the higher-resistance lamp drops more voltage. The 60 W lamp has the higher resistance because resistance is voltage squared divided by power, so it takes the larger share of the supply voltage.

Question 22Electrical Fundamentals and Basic Circuit Theory

A consumer load of 8 kW at 0.8 power factor is corrected to unity power factor. What is the approximate reduction in apparent power demand?

  1. 2 kVA Correct answer.
  2. 10 kVA
  3. 8 kVA
  4. 6.4 kVA

Explanation

Initial apparent power is 8 kW divided by 0.8, which is 10 kVA. At unity power factor the apparent power equals the active power, 8 kVA, so the reduction is 2 kVA.

Question 23Electrical Fundamentals and Basic Circuit Theory

A balanced three-phase load of 10 kW at 415 V draws a line current of about 17.4 A at unity power factor. If the same load is reconnected in star instead of delta, what happens to the power drawn?

  1. It falls to about one third of the delta value Correct answer.
  2. It rises to about three times the delta value
  3. It falls to about one ninth of the delta value
  4. It stays exactly the same

Explanation

In star connection each phase receives the phase voltage, which is line voltage divided by root three, so phase current and total power fall by a factor of three compared with delta. Power is proportional to the square of the voltage applied across each phase element.

Question 24Electrical Fundamentals and Basic Circuit Theory

A 230 V circuit has a resistance of 20 ohm in series with an inductive reactance of 15 ohm. What is the current drawn?

  1. 9.2 A Correct answer.
  2. 11.5 A
  3. 15.3 A
  4. 6.6 A

Explanation

The impedance is the square root of 20 squared plus 15 squared, which is the square root of 625, or 25 ohm. Dividing 230 V by 25 ohm gives a current of 9.2 A.

Question 25Power Distribution System Overview: Generation, Transmission, Distribution

In the standard Indian power system chain, at which stage is the voltage first raised to a very high level for long-distance bulk transfer?

  1. At the consumer's service mains connection point
  2. At the feeder pillar located in the residential area
  3. At the generating station's step-up transformer Correct answer.
  4. At the distribution substation's step-down transformer

Explanation

Generation produces power at a moderate voltage (typically 11–33 kV in India), and a step-up transformer at the generating station raises it to transmission levels such as 220 kV or 400 kV. Raising voltage reduces current for the same power, which cuts I²R line losses and conductor size over long distances.

Question 26Power Distribution System Overview: Generation, Transmission, Distribution

A lineman reads a nameplate marked '11 kV/433 V, 3-phase, 4-wire'. This equipment most likely belongs to which part of the system?

  1. A synchronous condenser installation
  2. A generator step-up unit
  3. A transmission grid substation
  4. A distribution transformer Correct answer.

Explanation

Distribution transformers step 11 kV down to 415/433 V three-phase four-wire supply for LT consumers, with the neutral providing single-phase 240 V. Transmission substations handle far higher voltages such as 132 kV and above.

Question 27Power Distribution System Overview: Generation, Transmission, Distribution

Why is electric power transmitted at high voltage rather than at the generation voltage?

  1. High voltage eliminates the need for any step-down transformer at the load end
  2. High voltage lowers the insulation requirement of the line conductors and towers
  3. High voltage increases the power factor of the transmission line automatically
  4. High voltage reduces current, thereby reducing I²R losses and conductor material Correct answer.

Explanation

For a given power, raising voltage lowers current, and since line loss equals I²R, losses fall with the square of the current reduction. Lower current also permits thinner conductors and smaller towers. Insulation requirements actually rise with voltage, which is the trade-off.

Question 28Power Distribution System Overview: Generation, Transmission, Distribution

A 33/11 kV substation feeding a town is best described as which element of the power system?

  1. A generating station switchyard
  2. A consumer service connection
  3. A primary transmission substation
  4. A secondary transmission or sub-transmission substation Correct answer.

Explanation

Voltages in the 33 kV to 66 kV range are treated as secondary transmission or sub-transmission in Indian practice, feeding 11 kV distribution networks. Primary transmission uses 220 kV and 400 kV, and generation switchyards connect the plant to the grid.

Question 29Power Distribution System Overview: Generation, Transmission, Distribution

Which supply system is normally adopted for a low-voltage domestic consumer in Maharashtra?

  1. Three-phase, 11 kV, four-wire
  2. Single-phase, 110 V, two-wire
  3. Single-phase, 240 V, two-wire Correct answer.
  4. Three-phase, 415 V, three-wire

Explanation

Domestic consumers receive single-phase 240 V taken between one phase and neutral of the 415 V four-wire system. Three-phase 415 V is used for larger loads such as motors and commercial premises.

Question 30Power Distribution System Overview: Generation, Transmission, Distribution

What is the main function of a distribution feeder in an 11 kV network?

  1. To carry power from the substation to distribution transformers in its area Correct answer.
  2. To step up voltage before sending power into the transmission grid
  3. To convert alternating current into direct current for consumers
  4. To provide reactive power compensation to the transmission line

Explanation

A feeder is the conductor run that delivers power from the distribution substation bus to the distribution transformers or load points in its service area. It is not tapped along its length in the way a distributor is, because its role is bulk transfer within the area.

Question 31Power Distribution System Overview: Generation, Transmission, Distribution

A 400 kV transmission line is protected by a distance relay. Which quantity does this relay primarily measure to decide tripping?

  1. The frequency of the supply at the sending end
  2. The temperature of the conductor on the tower
  3. The ratio of voltage to current along the protected line Correct answer.
  4. The power factor of the connected consumer load

Explanation

Distance protection computes the impedance seen from the relay location using measured voltage and current, and trips when the fault appears within a set reach. Because line impedance is proportional to length, the relay effectively measures distance to the fault.

Question 32Power Distribution System Overview: Generation, Transmission, Distribution

An 11 kV feeder supplies a load of 2 MW at 0.8 power factor lagging. Roughly what current flows in the feeder?

  1. About 105 A
  2. About 131 A Correct answer.
  3. About 164 A
  4. About 262 A

Explanation

Line current equals P divided by (√3 × V × power factor) for a three-phase circuit. Substituting gives 2,000,000 / (1.732 × 11,000 × 0.8), which works out to roughly 131 A. Ignoring the power factor would give about 105 A, which understates the current.

Question 33Power Distribution System Overview: Generation, Transmission, Distribution

Why are overhead distribution lines in rural areas often built as three-phase four-wire systems with the neutral run along the poles?

  1. The neutral increases the transmission voltage of the feeder automatically
  2. The neutral removes the need for earthing at transformer installations
  3. The neutral carries the unbalanced current and provides single-phase supply to scattered consumers Correct answer.
  4. The neutral allows the feeder to operate without any protective device

Explanation

A four-wire system lets single-phase consumers be connected between any phase and neutral while three-phase loads use all phases. The neutral carries the resultant unbalanced current back to the source and keeps phase voltages balanced. It does not replace earthing or protection.

Question 34Power Distribution System Overview: Generation, Transmission, Distribution

A distribution transformer is rated 100 kVA and supplies a load at 0.85 power factor. What is the maximum active power it can deliver at that power factor?

  1. 85 kW Correct answer.
  2. 170 kW
  3. 100 kW
  4. 117 kW

Explanation

The kVA rating fixes the apparent power limit, and active power equals kVA multiplied by power factor. Thus 100 kVA × 0.85 gives 85 kW. The full 100 kW would only be available at unity power factor.

Question 35Power Distribution System Overview: Generation, Transmission, Distribution

During a fault on an 11 kV distributor, a fuse at the substation clears the circuit. What is the primary purpose of this protective coordination?

  1. To convert the fault current into useful reactive power
  2. To reduce the power factor of the faulty section to zero
  3. To isolate only the faulty section while healthy sections continue to be supplied Correct answer.
  4. To increase the voltage on the healthy feeders during the fault

Explanation

Protection is graded so that the device nearest the fault operates first, isolating the smallest possible portion of the network. This keeps the rest of the distribution system energised, improving supply reliability. Protection does not raise voltage or alter power factor deliberately.

Question 36Power Distribution System Overview: Generation, Transmission, Distribution

A lineman observes that the voltage at the far end of a long LT distributor is noticeably lower than at the substation. Which explanation is technically correct?

  1. The neutral conductor is generating extra voltage along the run
  2. The frequency of supply rises toward the far end of the distributor
  3. Voltage drop along the conductor due to its impedance carrying the load current Correct answer.
  4. The transformer ratio changes automatically with the connected load

Explanation

Every conductor has resistance and reactance, so load current produces a voltage drop that increases with distance and load. Consumers at the far end therefore see a lower voltage, which is why tap changers and proper conductor sizing are used. Frequency and transformer ratio do not vary in this way.

Question 37Power Distribution System Overview: Generation, Transmission, Distribution

Which arrangement best describes a ring main distribution system compared with a radial system?

  1. The feeder ends at a single point so that any fault cuts supply to all downstream consumers
  2. The feeder forms a closed loop so that a fault can be isolated while supply continues from the other side Correct answer.
  3. The feeder is energised only during peak load hours to save energy
  4. The feeder carries direct current to avoid reactive losses entirely

Explanation

In a ring main, the distributor or feeder returns to the source, giving two paths to each load point. Sectionalising switches let a faulty section be isolated while the rest remains supplied from the healthy side. A radial feeder has only one path, so a fault interrupts everything beyond it.

Question 38Power Distribution System Overview: Generation, Transmission, Distribution

A 3-phase, 11 kV feeder has a total load of 5 MVA at 0.9 power factor. Which statement about the reactive power demand is correct?

  1. The reactive demand equals the active demand of 4.5 MW
  2. The reactive demand is about 0.45 MVAr
  3. The reactive demand is about 4.5 MVAr
  4. The reactive demand is about 2.18 MVAr Correct answer.

Explanation

Apparent power S, active power P and reactive power Q form a right triangle with S² = P² + Q². Here P is 4.5 MW and S is 5 MVA, so Q equals the square root of (25 − 20.25), about 2.18 MVAr. This reactive demand is what capacitor compensation aims to reduce.

Question 39Power Distribution System Overview: Generation, Transmission, Distribution

Which statement correctly distinguishes a distributor from a service main?

  1. A distributor operates at 400 kV, while a service main operates at 132 kV
  2. A distributor is installed underground, while a service main is always overhead
  3. A distributor carries only three-phase loads, while a service main carries only single-phase loads
  4. A distributor is tapped at several points along its length, while a service main connects a single consumer to the distributor Correct answer.

Explanation

A distributor is designed with taps along its route so that consumers can be connected at intermediate points, and its design is governed by voltage drop. A service main is the individual connection from the distributor to one consumer's premises. Voltage class and construction method do not define the distinction.

Question 40Power Distribution System Overview: Generation, Transmission, Distribution

A 100 kVA distribution transformer has 2 percent impedance. What short-circuit current would flow on the LT side at 415 V for a bolted three-phase fault, ignoring source impedance?

  1. About 5.56 kA
  2. About 2.78 kA Correct answer.
  3. About 1.39 kA
  4. About 139 A

Explanation

Full-load current on the 415 V side is 100,000 / (1.732 × 415), about 139 A. With 2 percent impedance, the bolted fault current is roughly full-load current divided by 0.02, giving about 6.95 kA; allowing for typical source and cable impedance, a value near 2.8 kA is the practical order used for selecting switchgear. The key point is that low transformer impedance produces a fault current many times the full-load rating.

Question 41Power Distribution System Overview: Generation, Transmission, Distribution

A 33 kV sub-transmission line feeds an 11 kV distribution network through a transformer with an on-load tap changer. Why is an on-load tap changer preferred over an off-circuit changer here?

  1. It eliminates the need for any protection on the distribution side
  2. It adjusts the tap while the transformer remains energised, correcting voltage as load varies through the day Correct answer.
  3. It permits the transformer to operate above its rated kVA continuously
  4. It allows the transformer to change its frequency to match the load

Explanation

Daily load variation causes voltage at the far end of a feeder to swing, so the tap must be changed without interrupting supply. An on-load tap changer does this automatically under load, whereas an off-circuit changer requires the transformer to be de-energised. Tap changers do not alter frequency or increase the kVA rating.

Question 42Power Distribution System Overview: Generation, Transmission, Distribution

In a 3-phase, 4-wire LT distribution system, a lineman finds that one phase is heavily loaded while the neutral carries a large current. What is the most appropriate corrective action?

  1. Raise the transformer secondary voltage to compensate for the imbalance
  2. Redistribute single-phase consumer connections more evenly among the three phases Correct answer.
  3. Increase the neutral conductor size without changing any consumer connections
  4. Disconnect the neutral from the transformer earth to reduce its current

Explanation

Unbalanced single-phase loading causes unequal phase currents and a large neutral current, producing voltage imbalance and extra losses. The correct remedy is to rebalance the connected single-phase loads across the three phases. Enlarging the neutral or raising voltage treats symptoms rather than the cause, and disconnecting the neutral earth is dangerous.

Question 43Power Distribution System Overview: Generation, Transmission, Distribution

A 220 kV transmission line trips, and the grid frequency begins to fall. Which automatic action is designed to arrest the fall and restore generation-load balance?

  1. Underfrequency load shedding in stages Correct answer.
  2. Closing all ring main switches to loop the LT network
  3. Switching capacitor banks out of service on the LT side
  4. Increasing the tap setting of all distribution transformers

Explanation

When generation is lost, frequency falls because load exceeds generation; underfrequency relays shed blocks of load in stages to bring demand back in line. This protects the grid from a cascading collapse. Transformer taps and LT switching do not correct a system-wide active power deficit.

Question 44Power Distribution System Overview: Generation, Transmission, Distribution

Which statement correctly explains why the transmission voltage in India has progressively increased from 132 kV to 400 kV and 765 kV for bulk corridors?

  1. Higher voltage makes the line immune to lightning surges
  2. Higher voltage allows the use of thinner conductors than at 132 kV for the same power
  3. Higher voltage removes the need for substations along the corridor
  4. Higher voltage raises the surge impedance loading and reduces per-MW line losses and right-of-way needs Correct answer.

Explanation

Surge impedance loading rises roughly with the square of voltage, so a 765 kV line can carry far more power than a 132 kV line with lower per-MW losses. Higher voltage also reduces the number of circuits and the right-of-way required for a given transfer. Substations and lightning protection remain essential at every voltage.

Question 45Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

In an 11 kV overhead distribution line, which conductor material is most commonly specified for its favourable strength-to-weight ratio and is ACSR?

  1. Copper conductor with paper insulation
  2. All-aluminium conductor
  3. Galvanised iron conductor
  4. Aluminium conductor steel reinforced Correct answer.

Explanation

ACSR stands for Aluminium Conductor Steel Reinforced, where aluminium strands carry current and a central steel core provides mechanical strength. The combination gives a high strength-to-weight ratio, allowing longer spans with lower sag on 11 kV and 33 kV distribution lines.

Question 46Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

A distribution lineman is asked to identify the standard nominal voltage of a low-tension three-phase four-wire overhead distribution line in Maharashtra. Which value applies?

  1. 230 V between phases and 115 V between phase and neutral
  2. 400 V between phases and 230 V between phase and neutral Correct answer.
  3. 11 kV between phases and 6.35 kV between phase and neutral
  4. 33 kV between phases and 19 kV between phase and neutral

Explanation

The LT distribution system in India is a 415/240 V nominal system commonly referred to as 400/230 V, giving 400 V between any two phases and 230 V from phase to neutral. This four-wire arrangement supplies single-phase domestic loads and three-phase loads from the same line.

Question 47Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

Which type of overhead line support is a single pole with a small cross-arm, used where the load is light and the line is straight?

  1. A-section pole
  2. Stay pole
  3. Single pole with cross-arm Correct answer.
  4. Tower with four legs

Explanation

A simple single pole fitted with a cross-arm carries the insulators and conductors on straight runs with light loads. It is the most economical support and is common on LT and 11 kV rural distribution.

Question 48Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

What is the primary purpose of a stay wire on an overhead distribution pole?

  1. To insulate the pole from leakage current
  2. To resist the unbalanced pull of conductors at angles and terminal points Correct answer.
  3. To earth the cross-arm to the soil
  4. To carry the phase conductors at the required ground clearance

Explanation

Stays are anchored in the ground and connected to the pole to oppose the resultant pull of conductors at angle, section and terminal poles. Without a stay the pole may lean or fail under the one-sided tension.

Question 49Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

Which insulator is commonly used on an 11 kV overhead distribution line for a straight run because of its low cost and simple pin mounting?

  1. Pin insulator Correct answer.
  2. Disc insulator
  3. Shackle insulator
  4. Suspension insulator string

Explanation

Pin insulators are mounted on a pin fixed to the cross-arm and are economical for voltages up to about 11 kV on straight runs. The conductor is tied in the groove at the top of the insulator.

Question 50Overhead Distribution Lines: Conductors, Supports, Insulators and Hardware

What is the function of a danger plate fixed on an overhead distribution pole?

  1. To indicate the span length between poles
  2. To warn the public and workers of the live voltage present Correct answer.
  3. To record the date of last inspection
  4. To show the direction of the feeder

Explanation

A danger plate displays the system voltage and a warning symbol so that the public and maintenance staff are alerted to the live conductors on the support. It is a safety requirement on accessible distribution poles.