New Mexico (NM) EL-1J Journeyman Electrical Distribution Systems, including Transmission Lines Practice ExamQuestions and Answers Best rated A+ Guaranteed Success Latest Update 1.What is the typical voltage range for primary distribution systems in the United States?
A) 120–240 V
B) 600–1,000 V
- 4 kV–35 kV
- 69 kV–500 kV
Rationale: Primary distribution usually operates between 4 kV and 35 kV. Transmission voltages are higher, and secondary distribution is lower.
2.Which of the following best describes the purpose of a substation?
- Increase customer billing accuracy
- Step voltage up or down and provide switching/protection
- Store energy for backup use
- Measure harmonics in the system
Rationale: Substations transform voltage levels and provide switching/protection for reliability.
3.
The conductor material most commonly used for overhead transmission lines is:
- Copper
- Aluminum Conductor Steel Reinforced (ACSR)
- Stainless steel
- Bronze
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Rationale: ACSR is the standard for overhead lines due to its strength-to-weight ratio and cost efficiency.
4.
The National Electrical Safety Code (NESC) primarily governs:
- Inside building wiring
- Utility transmission and distribution systems
- Low-voltage residential installations
- Data cabling
Rationale: NEC covers premises wiring; NESC governs overhead and underground utility distribution and transmission.
5.What happens to line current in a purely resistive AC circuit?
- Lags voltage by 90°
- Leads voltage by 90°
- Is zero
- Is in phase with voltage
Rationale: In a purely resistive circuit, voltage and current rise and fall together (in phase).
6.When calculating voltage drop on a distribution feeder, which factor is most important?
- Transformer type
- Conductor resistance and current flow
- Lightning arresters
- Number of insulators
Rationale: Voltage drop is caused by conductor resistance and current.
7.Which device automatically restores service after a temporary fault?
- Fuse
- Circuit breaker
- Recloser
- Disconnect switch 2 / 4
Rationale: Reclosers attempt to clear temporary faults by reclosing automatically.
8.
Grounding transmission line structures primarily provides:
- A return path for neutral current
- Lightning and fault current dissipation
- Reduction of corona losses
- Improved voltage regulation
Rationale: Grounding directs lightning and fault current safely into earth.
9.What is the typical spacing between phases on a high-voltage transmission line (69 kV and above)?
- 6 inches
- 1 foot
- Several feet (6–15 ft depending on voltage)
- 1 mile
Rationale: High voltages require significant air clearance to prevent flashover.
10.
The main purpose of a lightning arrester is to:
- Regulate voltage
- Protect equipment from transient overvoltages
- Step voltage down
- Balance loads
Rationale: Arresters limit surges by diverting them to ground.
11.Which of the following is a secondary distribution voltage?
A) 120/240 V 3 / 4
- 4.16 kV
- 34.5 kV
- 138 kV
Rationale: Customers typically receive 120/240 V service from secondary distribution.
12.
Sag in an overhead conductor is primarily affected by:
- Voltage level
- Conductor temperature and tension
- Insulator type
- Grounding method
Rationale: Heat increases sag; conductor tension and span length control it.
13.Which type of insulator is most common on distribution lines?
- Post insulator
- Pin-type insulator
- Suspension insulator
- Disc insulator
Rationale: Pin-type insulators are commonly used on lower-voltage distribution lines.Suspension types are used for higher voltages.
14.Which device is used to regulate feeder voltage by automatically adjusting tap settings?
- Transformer
- Voltage regulator
- Capacitor bank
- Lightning arrester
Rationale: Voltage regulators adjust taps to maintain constant voltage.
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