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Question 1. What does Ohm’s Law state for a simple DC circuit? A) V = I × R B) P = V × I C) I = V / C D) R = V × I Answer: A Explanation: Ohm’s Law defines the relationship between voltage (V), current (I), and resistance (R) as V = I × R. Question 2. In a three‑phase Wye (star) system, the line‑to‑neutral voltage is A) √3 times the line‑to‑line voltage B) Equal to the line‑to‑line voltage C) 1/√3 of the line‑to‑line voltage D) Not related to the line‑to‑line voltage Answer: C Explanation: For a Wye connection, V_line‑to‑neutral = V_line‑to‑line ÷ √3. Question 3. Which material typically has the highest conductivity for power conductors? A) Aluminum B) Copper C) Steel‑reinforced aluminum D) Nickel Answer: B Explanation: Copper’s electrical conductivity (~58 MS/m) exceeds that of aluminum (~35 MS/m) and steel. Question 4. A transformer’s nameplate lists “KV 110/10”. This indicates A) Primary voltage 110 kV, secondary 10 kV B) Primary current 110 A, secondary 10 A
C) Turns ratio of 110: D) Impedance of 110 % on 10 % load Answer: A Explanation: The notation “KV 110/10” denotes primary (high) voltage of 110 kV and secondary (low) voltage of 10 kV. Question 5. Which device is primarily used to protect a distribution line from lightning surges? A) Fuse B) Recloser C) Surge arrester D) Sectionalizer Answer: C Explanation: Surge arresters provide a low‑impedance path to ground for lightning‑induced over‑voltages. Question 6. In a series circuit, the total resistance is A) The arithmetic mean of individual resistances B) The sum of all individual resistances C) The product of all individual resistances D) The reciprocal of the sum of reciprocals Answer: B Explanation: Resistances in series add directly: R_total = Σ R_i. Question 7. The phase sequence “ABC” in a three‑phase system indicates A) Voltage magnitude order B) The order in which phases reach their positive peaks C) The order of neutral connections D) The order of grounding electrodes Answer: B
Question 11. In a delta‑connected three‑phase transformer, the line voltage is A) Equal to the phase voltage B) √3 times the phase voltage C) 1/√3 of the phase voltage D) Unrelated to the phase voltage Answer: B Explanation: For delta, V_line = √3 × V_phase. Question 12. The “kVA” rating of a transformer represents A) Real power output B) Apparent power capacity C) Reactive power only D) Energy loss per hour Answer: B Explanation: kVA is the apparent power, combining real (kW) and reactive (kVAR) components. Question 13. Which type of insulator is most commonly used on high‑voltage suspension lines? A) Pin insulator B) Disk (suspension) insulator C) Post insulator D) Strain insulator Answer: B Explanation: Disk or suspension insulators are stacked and support the line’s weight while providing required creepage distance. Question 14. A “cutout” in a distribution line primarily serves as A) A voltage regulator B) A fuse holder and protective device C) A line‑to‑ground fault detector
D) A switching mechanism for load shedding Answer: B Explanation: Cutouts house a fuse and provide a means to isolate a faulted section automatically. Question 15. The NESC minimum vertical clearance for a 69 kV line over a public roadway is A) 12 ft B) 18 ft C) 22 ft D) 30 ft Answer: C Explanation: According to NESC Table 2, a 69 kV line requires at least 22 ft vertical clearance over a public road. Question 16. When calculating voltage drop in a conductor, which parameter is most significant? A) Conductor color B) Conductor resistance per unit length C) Number of splices D) Type of pole material Answer: B Explanation: Voltage drop = I × R_total; resistance per unit length directly influences the drop. Question 17. A pole‑mount transformer is typically rated for A) 13.8 kV to 480 V distribution B) 115 kV to 13.8 kV transmission C) 34.5 kV to 13.8 kV sub‑transmission D) 4.16 kV to 120 V residential service Answer: A Explanation: Pole‑mount transformers step down medium‑voltage distribution (13.8 kV) to low‑voltage (480 V) for customer service.
B) Temperature rise due to current flow C) Number of insulators used D) Length of the pole Answer: B Explanation: Conductor sag increases with temperature because the conductor expands lengthwise. Question 22. A “sectionalizer” is used to A) Limit the length of a faulted section after a recloser opens B) Regulate voltage on a feeder C) Provide a ground fault path D) Measure line current for billing Answer: A Explanation: Sectionalizers count the number of reclose operations and open after a set count, isolating a faulted segment. Question 23. The primary function of a “grounding electrode” is to A) Carry load current B) Provide a low‑impedance path to earth for fault currents C) Support the pole structure D) Isolate the system from the utility grid Answer: B Explanation: Grounding electrodes (e.g., ground rods) ensure fault currents have a safe path to earth, limiting step and touch potentials. Question 24. Which of the following best describes a “pad‑mount” transformer? A) Mounted on a concrete pad at ground level, used in underground distribution B Incorrect (We must correct) Correction Answer: A
Explanation: Pad‑mount transformers are installed on a concrete pad, often in underground or compact urban settings, and are not pole‑mounted. Question 25. The “reactive power” of a purely inductive load is A) Zero B) Positive, measured in kVAR C) Negative, measured in kW D) Equal to apparent power Answer: B Explanation: Inductive loads draw reactive power (kVAR) with no real power consumption; it is positive by convention. Question 26. When a line‑to‑ground fault occurs, the “step potential” is A) Voltage difference between two points on the ground a step apart B) Voltage across the faulted conductor C) Current flowing through the ground rod D) The protective relay setting Answer: A Explanation: Step potential is the voltage gradient on the earth surface that can cause a hazardous current through a person’s body. Question 27. A “hot stick” is used for A) Lifting heavy equipment B) Performing live‑line work while maintaining safe distance C) Measuring voltage on de‑energized circuits D) Cutting tree branches near lines Answer: B Explanation: Hot sticks are insulated poles that allow workers to manipulate energized equipment from a safe distance.
C) S = V × I × cos ϕ D) S = V × I × sin ϕ Answer: A Explanation: Apparent power S (VA) equals RMS voltage multiplied by RMS current, regardless of phase angle. Question 32. The “minimum approach distance” for a de‑energized line is A) Determined by OSHA Table 1 for the voltage class B) Always 10 ft regardless of voltage C) The same as the live‑line approach distance D) Not required if the line is tagged “dead” Answer: A Explanation: OSHA Table 1 specifies minimum approach distances based on system voltage, even for de‑energized work. Question 33. A “recloser” differs from a standard circuit breaker because A) It can automatically close after opening without operator action B) It has a higher interrupting rating C) It is only used on underground cables D) It cannot be manually operated Answer: A Explanation: Reclosers are designed to automatically attempt reclosing after a temporary fault, unlike standard breakers. Question 34. In underground cable construction, “URD” stands for A) Underground Residential Distribution B) Unbalanced Resistive Design C) Ultra‑Resilient Dielectric D) Utility‑Rated Direct‑buried Answer: A
Explanation: URD cables are used for residential distribution and are designed for direct burial. Question 35. The primary cause of “corona discharge” on high‑voltage lines is A) Excessive conductor sag B) High electric field intensity at conductor surface C) Low line current D) Presence of steel reinforcement in the conductor Answer: B Explanation: Corona occurs when the electric field exceeds the ionization strength of air, causing a visible discharge. Question 36. Which of the following is a common method to locate underground conductors? A) Visual inspection of the ground surface B) Use of a cable locator or fault‑location device C) Listening for humming sounds D) Measuring soil temperature Answer: B Explanation: Cable locators inject a signal onto the conductor and detect it above ground to determine location. Question 37. A “sectionalizer” counts the number of reclose attempts and then A) Opens the circuit to isolate the faulted section B) Increases the voltage on the line C) Sends a signal to the control center D) Switches to a backup feeder automatically Answer: A Explanation: After a preset number of reclose cycles, the sectionalizer opens, keeping the faulted portion isolated. Question 38. Which factor most influences the ampacity of a buried cable?
D) A portable generator Answer: A Explanation: Pole‑top rescues are performed from bucket trucks equipped with rescue baskets and fall‑protection gear. Question 42. The “reactance” of an inductor in a 60 Hz AC system is calculated by A) X_L = 2π f L B) X_L = 1/(2π f L) C) X_L = R × L D) X_L = V ÷ I Answer: A Explanation: Inductive reactance X_L = 2πfL, where f is frequency and L is inductance. Question 43. Which type of insulator is most suitable for a dead‑end on a 138 kV line? A) Pin insulator B) Suspension (disk) insulator with strain block C) Post insulator D) Horn‑type insulator Answer: B Explanation: For high‑voltage dead‑ends, suspension insulators with a strain block provide the required mechanical strength and creepage distance. Question 44. The purpose of a “voltage regulator” in a distribution feeder is to A) Reduce line current during peak load B) Maintain a constant voltage despite load variations C) Detect ground faults D) Provide a backup power source Answer: B Explanation: Voltage regulators adjust tap settings to keep feeder voltage within acceptable limits as load changes.
Question 45. In a three‑phase system, the total apparent power (S_total) is A) √3 × V_LL × I_L B) 3 × V_phase × I_phase C) V_LL × I_L × cos ϕ D) Both A and B (they are equivalent) Answer: D Explanation: Both formulas represent total apparent power: S_total = √3 · V_LL · I_L = 3 · V_phase · I_phase. Question 46. A “ground‑fault interrupter” (GFI) works by A) Measuring the difference between line and neutral currents and tripping when imbalance exceeds a threshold B) Detecting over‑voltage on the line C) Monitoring temperature of conductors D) Providing surge protection for equipment Answer: A Explanation: GFIs compare line and neutral currents; a mismatch indicates leakage to ground and triggers a trip. Question 47. The term “creepage distance” refers to A) The distance a conductor sags under its own weight B) The shortest surface path along an insulator between energized parts and grounded parts C) The horizontal clearance between a line and a building D) The distance between two poles in a line span Answer: B Explanation: Creepage distance is the path along the surface of an insulator that leakage current must travel, influencing flashover risk. Question 48. Which of the following best describes a “sectionalizer” operation after a fault?
B) Excessive sag due to high temperature C) Low line voltage D) Use of aluminum conductors only Answer: A Explanation: Ice builds up on conductors, and wind can cause them to oscillate (gallop), leading to mechanical stress. Question 52. A “dead‑end” strain block is used to A) Provide a mechanical anchor for the conductor at the end of a span B) Reduce voltage on the line C) Serve as a grounding point for the system D) Act as a fuse for overload protection Answer: A Explanation: Strain blocks transfer the tensile load from the conductor to the dead‑end insulator assembly. Question 53. The term “ampacity” is derived from A) “Ampere capacity” – the maximum continuous current a conductor can carry B) “Amplitude capacity” – the peak voltage a line can handle C) “Amplifier capacity” – the power rating of a transformer D) “Amphibian capacity” – a code term for underground cables Answer: A Explanation: Ampacity stands for ampere capacity, indicating the allowable current based on temperature limits. Question 54. When a distribution line is “recloser‑blocked,” it means A) The recloser will not attempt to close after a fault until manually reset B) The recloser is operating at maximum speed C) The recloser is in a locked‑out condition D) The recloser has failed and must be replaced
Answer: A Explanation: Recloser‑blocked indicates the device will stay open after a fault until an operator intervenes. Question 55. Which of the following best describes a “phase‑to‑ground” fault? A) A fault between two phases only B) A fault between one phase and the earth/ground C) A fault between all three phases simultaneously D) A fault that occurs only during maintenance Answer: B Explanation: Phase‑to‑ground faults involve a conductive path from a phase conductor to earth. Question 56. The purpose of “guy wires” on a transmission tower is to A) Carry the phase conductors B) Provide lateral support to resist wind and ice loads C) Serve as grounding conductors D) Reduce electromagnetic interference Answer: B Explanation: Guy wires anchor the tower and counteract lateral forces from wind and ice. Question 57. Which of the following is true about a “three‑phase, four‑wire” Wye system? A) It provides a neutral conductor for single‑phase loads B) It does not have a neutral conductor C) It is only used for high‑voltage transmission D) It cannot supply single‑phase loads Answer: A Explanation: The fourth wire is the neutral, allowing connection of both three‑phase and single‑phase loads.
C) Voltage fluctuation caused by solar generation D) Voltage rise after a fault is cleared Answer: A Explanation: Load‑drop voltage is the IR drop across the line’s resistance and reactance under load. Question 62. When performing “hot‑line” work, the minimum safe distance from an energized 13.8 kV line is A) 3 ft B) 6 ft C) 10 ft D) 15 ft Answer: C Explanation: OSHA Table 1 specifies a minimum approach distance of 10 ft for 13.8 kV lines. Question 63. The term “continuous rating” of a transformer refers to A) The maximum power it can deliver for a short period B) The power level it can sustain indefinitely without overheating C) The voltage rating of its primary winding only D) The number of taps available on the secondary Answer: B Explanation: Continuous rating is the thermal limit for indefinite operation. Question 64. A “cable vault” is primarily used for A) Housing underground cable splices and terminations in a protected environment B) Storing spare conductors on the field C) Providing a shelter for pole‑top equipment D) Acting as a transformer oil reservoir Answer: A
Explanation: Cable vaults protect splices, terminations, and connections from moisture and mechanical damage. Question 65. Which of the following is a common cause of “flashover” on an insulator? A) Excessive creepage distance B) Surface contamination combined with high voltage C) Low ambient temperature D) Use of steel‑reinforced conductors Answer: B Explanation: Contaminants reduce the effective creepage distance, allowing a conductive path to develop under high voltage. Question 66. In a distribution network, “sectionalizing” is used to A) Divide a feeder into smaller sections for selective isolation during faults B) Increase the voltage on the entire feeder C) Combine multiple feeders into one larger circuit D) Provide a backup power source for critical loads Answer: A Explanation: Sectionalizers isolate faulted portions while allowing the rest of the feeder to stay energized. Question 67. The “thermal rating” of a fuse is the A) Maximum voltage it can interrupt B) Current at which it will melt under specified time‑current characteristics C) Physical size of the fuse element D) Frequency at which it operates Answer: B Explanation: Thermal rating defines the current level and time required for the fuse element to melt and open the circuit.
