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Question 1. What is the current in amperes when a 240 V load draws 12 kW of real power at unity power factor? A) 25 A B) 30 A C) 50 A D) 100 A Answer: B Explanation: P = V × I → I = P/V = 12 000 W / 240 V = 50 A. Because the power factor is 1, apparent power equals real power, so I = 50 A. The correct answer is C (50 A). Question 2. In a series circuit of three resistors 4 Ω, 6 Ω, and 10 Ω connected to a 120 V source, what is the voltage across the 6 Ω resistor? A) 24 V B) 30 V C) 36 V D) 48 V Answer: B Explanation: Total resistance = 4+6+10 = 20 Ω. Total current I = V/R = 120 V / 20 Ω = 6 A. Voltage across 6 Ω = I × R = 6 A × 6 Ω = 36 V. The correct answer is C. Question 3. Which of the following best describes the relationship between peak voltage (V_peak) and RMS voltage (V_RMS) for a sinusoidal AC waveform? A) V_RMS = V_peak / √2 B) V_RMS = V_peak C) V_RMS = V_peak × √2 D) V_RMS = V_peak / 2 Answer: A Explanation: For a pure sine wave, V_RMS = V_peak / √2 (approximately 0.707 × V_peak). Question 4. A three-phase, 4.16 kV (line-to-line) wye-connected system has what line-to-neutral voltage? A) 2.40 kV B) 4.16 kV C) 2.40 V D) 7.21 kV Answer: A Explanation: V_L-N = V_L-L / √3 = 4.16 kV / 1.732 ≈ 2.40 kV. Question 5. In a delta-connected three-phase load, the phase current is equal to: A) Line current divided by √3 B) Line current multiplied by √3 C) Line voltage divided by √3 D) Line voltage multiplied by √ Answer: B
Explanation: For delta, I_phase = I_line × √3. Question 6. A transformer has a primary of 240 V and a secondary of 120 V. What is its turns ratio (N_primary : N_secondary)? A) 1 : 2 B) 2 : 1 C) 1 : 1 D) 4 : 1 Answer: B Explanation: Turns ratio equals voltage ratio. 240 V/120 V = 2, so N_primary : N_secondary = 2 : 1. Question 7. A 500 kVA, 60 Hz, 3-phase transformer has a 5 % impedance. What is the short-circuit voltage (in volts) referred to the primary? A) 5 % of 480 V B) 5 % of 277 V C) 5 % of 600 V D) 5 % of 208 V Answer: A Explanation: Impedance voltage = %Z × rated primary voltage. Assuming a 480 V primary, 5 % of 480 V = 24 V. Question 8. Which type of transformer connection provides a neutral point on the secondary without requiring a separate grounding transformer? A) Delta-Delta B) Wye-Wye C) Open-Delta D) Zig-Zag Answer: B Explanation: A wye-connected secondary inherently provides a neutral point. Question 9. When testing a three-phase transformer bank for correct polarity, you connect a voltmeter between the high-side of phase A and the low-side of phase B. The meter reads 0 V. What polarity condition exists? A) Additive (correct) B) Subtractive C) Open circuit D) Shorted turns Answer: B Explanation: Zero volts between high of A and low of B indicates subtractive polarity (phases are 180° out of phase). Question 10. A step-voltage regulator is set to raise the secondary voltage by 2 % under load. If the feeder voltage is 12 kV, what voltage does the regulator attempt to maintain?
A) Conductor material, temperature, wind speed B) Tension, span length, temperature C) Span length, wind speed, ice thickness D) Tension, wind speed, ice thickness Answer: B Explanation: Sag = f(tension, span length, temperature) because temperature changes conductor length, tension resists sag, and longer spans increase sag. Question 16. A vibration damper is installed on a conductor to mitigate Aeolian vibration. Which condition most likely triggers the need for a damper? A) Wind speeds above 30 mph B) Ice loading over 0.5 in C) Conductors spaced less than 20 ft apart D) Conductors operating above 75 °C Answer: A Explanation: Aeolian vibration occurs in moderate wind (10- 30 mph); dampers are installed when wind speeds regularly exceed 30 mph to prevent fatigue. Question 17. When calculating the lead-to-height ratio for a guy wire, which ratio provides the most stable configuration? A) 1 : 1 B) 1 : 2 C) 1 : 3 D) 1 : 4 Answer: C Explanation: A 1 : 3 (lead:height) ratio yields a stable angle (~18°) that balances tension and ground reaction forces. Question 18. What is the primary purpose of a compression sleeve splice on a stranded copper conductor? A) To increase conductor diameter B) To provide a permanent, low-resistance joint C) To allow quick disconnection D) To insulate the joint from moisture Answer: B Explanation: Compression sleeves create a permanent, mechanically robust, low-resistance joint without solder. Question 19. Which type of insulator is most appropriate for a pin-type attachment on a 13.8 kV distribution line? A) Suspension B) Pin C) Strain D) Line post Answer: B
Explanation: Pin insulators are designed for direct attachment of conductors on a pole, typical for 13.8 kV distribution. Question 20. In underground residential distribution (URD), the minimum conduit fill for a single 4/0 AWG copper cable is: A) 30 % B) 40 % C) 53 % D) 60 % Answer: C Explanation: NEC Table 1, Chapter 9 permits up to 53 % fill for a single cable in a conduit. Question 21. The allowable pulling tension for a 350 kcmil XLPE cable in a 2-in. conduit is closest to: A) 1,000 lb B) 2,000 lb C) 3,500 lb D) 5,000 lb Answer: B Explanation: Manufacturer tables typically limit pulling tension for 350 kcmil XLPE to about 2 times its breaking strength, roughly 2,000 lb in a 2-in. conduit. Question 22. Which splicing method is recommended for underground PVC-lined duct bank terminations to maintain water tightness? A) Heat-shrink sleeve B) Cold-shrink sleeve C) Mechanical compression D) Soldered splice Answer: B Explanation: Cold-shrink sleeves provide a reliable, water-tight seal without the need for heat, ideal for underground terminations. Question 23. A pad-mounted transformer has a nameplate voltage of 13.8 kV primary and 240 V secondary. What is its turns ratio? A) 57.5 : 1 B) 1 : 57.5 C) 13.8 : 0.24 D) 0.24 : 13. Answer: A Explanation: Turns ratio = V_primary / V_secondary = 13 800 V / 240 V ≈ 57.5 : 1. Question 24. When using a thumper to locate a fault in an underground cable, the operator hears a “click” after the thumper fires. What does this indicate?
Question 29. When using a hot-stick (link stick) for a live-line operation, the minimum clearance between the stick tip and the conductor must be at least: A) 6 in B) 12 in C) 18 in D) 24 in Answer: C Explanation: NEC and OSHA require a minimum 18 in clearance to prevent arcing from the stick to the conductor. Question 30. In grounding a substation, the “Equal Potential Zone” (EPZ) is established to: A) Provide a low-impedance path for fault current B) Prevent step and touch potentials C) Isolate the substation from the utility grid D) Increase system voltage stability Answer: B Explanation: EPZ grounding reduces voltage gradients, protecting personnel from step and touch voltage hazards. Question 31. The required size of a ground-bonding conductor for a 400 A service, copper, is: A) 4 AWG B) 2 AWG C) 1/0 AWG D) 4/0 AWG Answer: C Explanation: NEC Table 250.122 specifies 1/0 AWG copper for a 400 A service. Question 32. A block and tackle system has a mechanical advantage of 4. If a 2,000 lb load is lifted, what is the input force required (ignoring friction)? A) 250 lb B) 500 lb C) 1,000 lb D) 2,000 lb Answer: B Explanation: Input force = Load / Mechanical advantage = 2,000 lb / 4 = 500 lb. Question 33. When rigging a load with a sling at a 60° angle to the vertical, the tension in each leg of the sling is: A) Equal to the load B) 0.5 × load C) 0.87 × load D) 1.15 × load Answer: D
Explanation: Tension = Load / (2 × cos θ). For θ = 60°, cos θ = 0.5 → Tension = Load / (2 × 0.5) = Load. Actually tension equals load. The correct answer is A. Question 34. Which type of circuit breaker uses a vacuum interrupter to extinguish the arc? A) Oil B) SF₆ C) Vacuum D) Air-magnetic Answer: C Explanation: Vacuum circuit breakers extinguish arcs inside a vacuum interrupter chamber. Question 35. A recloser on a distribution line is set to attempt a reclosing operation after a fault. How many automatic reclosing attempts are typically permitted before the device locks out? A) 1 B) 2 C) 3 D) 4 Answer: B Explanation: Standard practice allows two automatic reclosing attempts before lockout. Question 36. Lightning arresters are installed on transmission lines primarily to: A) Reduce line sag B) Limit over-voltage transients C) Increase line current-carrying capacity D) Provide grounding for the tower Answer: B Explanation: Arresters divert lightning-induced over-voltages to ground, protecting equipment. Question 37. In a lattice tower, the “D” member typically refers to: A) The diagonal bracing B) The top cross-arm C) The dead-end brace D) The base plate Answer: A Explanation: “D” members are diagonal bracing elements that provide lateral stability.
Answer: B Explanation: Z_base = V² / S = (7 200 V)² / 100 000 VA = 518.4 Ω. 5 % of 518.4 Ω = 25.92 Ω. Reactance is 5 % of impedance, not 5 % of rating. The correct answer is C (7.5 Ω) is not correct. Question 43. In a Wye-Delta transformer bank, the primary is wye-connected and the secondary is delta-connected. Which of the following is true about the line voltages? A) Primary line voltage equals secondary line voltage B) Primary line voltage is √ times secondary line voltage C) Secondary line voltage is √3 times primary line voltage D) Both line voltages are identical to phase voltages Answer: C Explanation: In a Wye-Delta bank, V_LL,secondary = √ 3 × V_LL,primary. Question 44. The purpose of a strain insulator on a suspension line is to: A) Increase line sag B) Reduce conductor vibration C) Provide mechanical support for conductor weight D) Isolate the line from the pole Answer: C Explanation: Strain insulators bear the mechanical load of the conductor and maintain clearance. Question 45. A 350 kcmil aluminum conductor has a resistance of 0.321 Ω per 1,000 ft at 75 °C. What is the voltage drop for a 0.5 mile run carrying 200 A? A) 16.2 V B) 32.4 V C) 64.8 V D) 128 V Answer: B Explanation: Length = 0.5 mi = 2,640 ft. Resistance = 0.321 Ω/1,000 ft × 2.64 = 0.847 Ω. Voltage drop = I × R = 200 A × 0.847 Ω ≈ 169 V. None of the choices match; the correct answer should be 169 V. Question 46. Which of the following best describes the function of a sectionalizer in a distribution network? A) Opens on over-current immediately B) Opens only after a set number of reclose cycles C) Provides voltage regulation D) Detects ground faults and trips instantly Answer: B
Explanation: Sectionalizers count reclose operations and open after a predetermined number to isolate faulted sections. Question 47. A 69 kV transmission line uses a bundle of three conductors per phase. If the spacing between conductors in a bundle is 0.5 ft, what is the approximate bundle reduction factor for inductance? A) 0.85 B) 0.90 C) 0.95 D) 1. Answer: B Explanation: Bundle spacing reduces inductance; a typical reduction factor for a three-conductor bundle with 0.5 ft spacing is about 0.90. Question 48. The NEC requires a minimum of how many feet of working clearance between a live overhead line and a grounded metal pole? A) 4 ft B) 6 ft C) 8 ft D) 10 ft Answer: B Explanation: NEC 2020 225.30 requires at least 6 ft of clearance for grounded metal poles. Question 49. When performing a lockout/tagout (LOTO) on a substation breaker, which of the following is the first step? A) Apply the lock B) Verify de-energization C) Place the tag D) Remove the breaker Answer: B Explanation: The first step is to verify that the equipment is de-energized before applying locks and tags. Question 50. A 10 kV underground cable is installed in a duct bank with a spacing of 12 in. What is the minimum separation required between this cable and a 4.16 kV service cable in the same bank? A) 6 in B) 12 in C) 18 in D) 24 in Answer: C Explanation: NEC requires a minimum of 12 in separation for voltage differences over 1 kV; however, a 6 in spacing is acceptable if the cables are of the same voltage class. The correct answer is B.
Answer: D Explanation: OSHA requires a minimum 18 in clearance regardless of stick rating. Question 56. When grounding a steel pole, the required ground-rod length for a soil resistivity of 150 Ω·cm is approximately: A) 4 ft B) 6 ft C) 8 ft D) 10 ft Answer: C Explanation: Standard practice uses an 8-ft ground rod for typical soils; higher resistivity may require longer rods. Question 57. A bucket-truck operator lifts a load of 3,000 lb using a sling at a 45 ° angle to the vertical. What is the tension in each leg of the sling? A) 1,500 lb B) 2,121 lb C) 3,000 lb D) 4,242 lb Answer: B Explanation: Tension per leg = Load / (2 × cos 45°) = 3,000 / (2 × 0.707) ≈ 2,121 lb. Question 58. The purpose of an “additive polarity” test on a transformer bank is to verify that: A) The windings are wound in the same direction B) The secondary voltages add when paralleled C) The transformer is free of internal faults D) The tap changer is set correctly Answer: B Explanation: Additive polarity ensures that when two transformers are paralleled, their secondary voltages add rather than cancel. Question 59. In a 13.8 kV distribution line, the minimum horizontal clearance from a building edge is: A) 3 ft B) 6 ft C) 10 ft D) 15 ft Answer: C Explanation: NEC 2020 requires at least 10 ft horizontal clearance for 13.8 kV lines. Question 60. A 250 kVA, 480 V three-phase transformer has a nameplate impedance of 6 %. What is its short-circuit voltage (in volts) on the primary?
A) 28.8 V B) 57.6 V C) 86.4 V D) 115.2 V
Answer: B Explanation: V_sc = %Z × V_primary = 0.06 × 480 V = 28.8 V. The correct answer is A. Question 61. Which of the following is the most common cause of a “hot spot” in a transformer winding? A) Over-voltage B) Uneven cooling C) Excessive load current D) Low oil level Answer: B Explanation: Uneven cooling leads to localized temperature rise (hot spot). Question 62. In a three-phase, 4.16 kV delta-connected system, the line-to-neutral voltage is: A) 2.40 kV B) 4.16 kV C) 7.21 kV D) Not applicable Answer: D Explanation: Delta systems do not have a neutral point; therefore line-to-neutral voltage is not applicable. Question 63. When installing a pole-mounted transformer, the recommended minimum distance between the transformer and the pole base is: A) 12 in B) 24 in C) 36 in D) 48 in Answer: B Explanation: A 24-inch clearance allows for proper ventilation and maintenance access. Question 64. The primary function of a “load-break switch” is to: A) Interrupt fault currents B) Isolate a circuit under load without arcing C) Regulate voltage D) Provide over-current protection Answer: B Explanation: Load-break switches are designed to open circuits while carrying load current, using arc-quenching mechanisms.
Answer: A Explanation: Dead-end resistors limit the fault current at the line termination, protecting equipment. Question 70. When pulling a 350 kcmil cable through a 2-in. conduit, the recommended maximum pulling tension is: A) 500 lb B) 1,000 lb C) 1,500 lb D) 2,000 lb Answer: C Explanation: Manufacturer guidelines typically limit pulling tension to about 1,500 lb for 350 kcmil in 2-in. conduit. Question 71. In a three-phase, 13.8 kV system, the line-to-line voltage is 13.8 kV. What is the per-phase voltage (phase-to-neutral) for a wye configuration? A) 7.97 kV B) 8.00 kV C) 11.96 kV D) 13.80 kV Answer: A Explanation: V_phase = V_LL / √3 = 13.8 kV / 1.732 ≈ 7.97 kV. Question 72. A “dead-end” resistor of 5 Ω is installed on a 12 kV feeder that supplies a 200 A load. What is the voltage drop across the resistor? A) 100 V B) 200 V C) 300 V D) 400 V Answer: B Explanation: V = I × R = 200 A × 5 Ω = 1,000 V. None of the answers match; the correct answer is 1,000 V. Question 73. The “arc flash boundary” for a piece of equipment rated at 30 kA incident energy of 8 cal/cm² is: A) 4 ft B) 8 ft C) 12 ft D) 16 ft Answer: B Explanation: NFPA 70E calculations typically place a 8 cal/cm² boundary at about 8 ft. Question 74. Which type of protective device automatically recloses after a temporary fault and then locks out if the fault persists?
A) Recloser B) Breaker C) Fuse D) Sectionalizer Answer: A Explanation: Reclosers attempt to restore service after transient faults and lock out on repeated faults. Question 75. A 15 kV, 10 MVA transformer has a no-load loss of 0.5 % and a full-load loss of 2 %. What is its efficiency at full load? A) 97.5 % B) 98.0 % C) 98.5 % D) 99.0 % Answer: B Explanation: Efficiency = (Output) / (Input) = (100 % – losses). Total loss = 0.5 % + 2 % = 2.5 %; efficiency = 97.5 %. The correct answer is A. Question 76. The primary reason for installing a “surge protector” on a distribution feeder is to: A) Reduce line losses B) Prevent voltage spikes caused by switching C) Increase ampacity D) Provide grounding for the feeder Answer: B Explanation: Surge protectors clamp transient over-voltages caused by switching or lightning. Question 77. In a 4-wire, 120/240 V residential service, the neutral conductor must be: A) Grounded at the transformer only B) Grounded at every service entrance C) Isolated from ground D) Connected to each load Answer: A Explanation: The neutral is grounded at the transformer (source) and at the service disconnect, but not at each load. Question 78. When using a “link-stick” for a live-line operation, the stick is typically made of: A) Fiberglass B) Aluminum C) Carbon fiber reinforced polymer D) Steel Answer: C
A) Ground rods only B) Ground plates only C) Ground wires (ground straps) attached to the tower legs D) No grounding required Answer: C Explanation: Ground wires (or ground straps) are run from the tower legs to a ground rod or ground plate to provide a low-impedance path. Question 84. When performing a “phase-to-ground” voltage test on a three-phase system, the measured voltage will be: A) Equal to line-to-line voltage B) Equal to line-to-neutral voltage C) √3 times line-to-neutral voltage D) Half of line-to-line voltage Answer: B Explanation: Phase-to-ground voltage equals line-to-neutral voltage in a wye system. Question 85. The ANSI/IEEE standard for transformer tap changer performance is: A) IEEE C57.12.00 B) IEEE C57.13 C) IEEE C57.91 D) IEEE C57. Answer: B Explanation: IEEE C57.13 covers tap changer design and performance. Question 86. A 250 kVA transformer has a temperature rise of 55 °C. If the ambient temperature is 35 °C, what is the maximum permissible winding temperature? A) 55 °C B) 90 °C C) 110 °C D) 150 °C Answer: B Explanation: Max winding temperature = ambient + rise = 35 °C + 55 °C = 90 °C. Question 87. In a three-phase, 13.8 kV delta system, the line current for a 1 MVA balanced load is: A) 41.8 A B) 48.5 A C) 69.3 A D) 83.3 A Answer: D Explanation: For delta, S = √3 × V_LL × I → I = S / (√3 × V_LL) = 1 000 kVA / (1.732 × 13.8 kV) ≈ 41.8 A. The correct answer is A.
Question 88. The main advantage of using a “double-circuit” tower in a transmission line is: A) Reduced construction cost B) Ability to carry two separate circuits on one structure C) Improved visual aesthetics D) Lower line losses Answer: B Explanation: Double-circuit towers allow two independent circuits to be mounted on the same tower, saving right-of-way. Question 89. When a live-line worker uses a “shotgun” hot-stick, the tool is primarily used for: A) Pulling conductors B) Cutting live conductors C) Applying a voltage test probe D) Measuring current Answer: C Explanation: A shotgun is a hot-stick equipped with a voltage probe for testing line voltage from a safe distance. Question 90. The correct procedure for “de-energizing” a substation breaker includes: A) Opening the breaker, then removing the lock B) Removing the lock, then opening the breaker C) Verifying no voltage, then opening the breaker D) Opening the breaker, verifying no voltage, then applying lock and tag Answer: D Explanation: The breaker must be opened, voltage verified absent, then lockout/tagout applied. Question 91. A 13.8 kV overhead line is required to have a minimum clearance of 10 ft from any building roof. If the line is 28 ft above ground, what is the minimum horizontal distance from the building edge? A) 10 ft B) 12 ft C) 14 ft D) 16 ft Answer: A Explanation: NEC requires a minimum of 10 ft clearance both vertically and horizontally for this voltage.
