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Key Facts: SC Public Utilities Electrical Exam

50 Q

Official Exam Questions

PSI SC Commercial Contractor CIB updated 5/15/2025

70%

Passing Score

PSI SC Commercial Contractor CIB updated 5/15/2025

3 hours

Time Allowed

PSI SC Commercial Contractor CIB updated 5/15/2025

USD 60

PSI Exam Fee

PSI SC Commercial Contractor CIB updated 5/15/2025

Open Book

Book Policy

PSI SC Commercial Contractor CIB updated 5/15/2025

South Carolina Public Utilities - Electrical Contractor Examination is the official CLB/PSI open-book exam: 50 questions, 70% (35 of 50), 3 hours, USD 60 (bulletin updated 5/15/2025). Official delivery is English.

Sample SC Public Utilities Electrical Practice Questions

Try these sample questions to review concepts for the SC Public Utilities Electrical exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A 37.5 kVA single-phase pole-mount transformer is fully loaded on a 240 V secondary. What is the approximate full-load secondary current?
A.78 A
B.156 A
C.312 A
D.16 A
Explanation: Single-phase current is I = S / V. Convert 37.5 kVA to 37,500 VA and divide by 240 V: 37,500 / 240 = 156 A. Line crews use this check when sizing secondary leads, connectors, and loading on a South Carolina distribution transformer.
2H1 and X1 markings on a distribution transformer identify which terminals?
A.The tank ground lugs only
B.The instantaneous-polarity ends of the primary and secondary windings
C.The high-voltage and low-voltage bushings that must never be used together
D.The internal fuse and secondary breaker terminals on a CSP unit
Explanation: H1 (primary) and X1 (secondary) mark terminals of the same instantaneous polarity. Crews use those marks to connect additive or subtractive banks, to check rotation, and to avoid circulating current when paralleling units.
3Oil in a liquid-filled overhead distribution transformer is used primarily to:
A.Increase the nameplate kVA by raising winding resistance
B.Insulate the windings and transfer heat from the coils to the tank
C.Serve as the multi-grounded system neutral
D.Replace the need for a surge arrester on the primary
Explanation: Transformer oil is a dielectric that isolates the windings and a coolant that carries heat to the tank and radiators. Losing oil level or contaminating the oil reduces both insulation strength and cooling.
4On a completely self-protected (CSP) overhead distribution transformer, the secondary overload device is typically:
A.An external primary fused cutout on the crossarm
B.A secondary breaker mounted inside the tank
C.A network protector in the vault
D.A customer main breaker at the meter
Explanation: A CSP transformer carries an internal primary weak-link fuse, a secondary breaker in the tank, and usually tank-mounted arresters. The internal secondary breaker opens on overload or secondary fault so the unit can be reset from the handle on the tank.
5A 50 kVA single-phase transformer has a 7,620 V primary. What is the approximate full-load primary current?
A.3.3 A
B.6.6 A
C.13.1 A
D.208 A
Explanation: Single-phase current is I = S / V. 50,000 VA / 7,620 V ≈ 6.6 A. That primary current is used to size the fused cutout, primary leads, and loading on a 7.2/12.47 kV class South Carolina feeder.
6Three 25 kVA single-phase transformers are banked closed-delta. What is the three-phase bank rating?
A.25 kVA
B.43 kVA
C.75 kVA
D.150 kVA
Explanation: In a closed-delta bank each transformer carries one phase, so the three-phase rating is the sum of the three nameplates: 25 + 25 + 25 = 75 kVA. An open-delta (V) bank of two units would be only about 86.6 percent of the two-unit sum, not the closed-delta total.
7A single-phase transformer is rated 7,200 V primary and 240 V secondary. If the primary winding has 1,500 turns, how many secondary turns are required for that voltage ratio?
A.25 turns
B.50 turns
C.150 turns
D.500 turns
Explanation: Turns ratio equals voltage ratio: Np / Ns = Vp / Vs. 1,500 / Ns = 7,200 / 240 = 30, so Ns = 1,500 / 30 = 50 turns. The same ratio is used when checking nameplate voltages before banking transformers.
8A delta-wye transformer bank is commonly used to serve 480Y/277 V three-phase loads from a delta primary feeder because the wye secondary:
A.Eliminates the need for a grounded conductor on the secondary
B.Provides a grounded-wye neutral and 277 V line-to-neutral for mixed loads
C.Forces all secondary loads to be ungrounded corner-grounded delta
D.Makes primary and secondary zero-sequence currents identical
Explanation: A wye secondary gives a neutral at the common point of the three windings, so the bank can serve 480 V three-phase and 277 V line-to-neutral loads. The delta primary also traps secondary zero-sequence current so it does not pass into the primary feeder.
9A no-load tap changer (NLTC) on a distribution transformer is intended to be operated:
A.Under full load to regulate feeder voltage in real time
B.Only after the transformer has been deenergized
C.From the secondary breaker handle while the primary is hot
D.By shorting adjacent taps with a hot-line clamp
Explanation: A no-load tap changer changes the primary turns only when the transformer is deenergized. Operating it hot flashes the tap contacts and can destroy the changer. Load-tap changers (LTCs) are the devices built to tap under load, and they are not the typical pole-mount NLTC.
10Before paralleling two single-phase distribution transformers on the same secondary, a line crew must verify that the units have matching:
A.Tank color and manufacturer only
B.Voltage ratings, polarity, and similar percent impedance
C.Primary fuse sizes only
D.Secondary breaker trip settings only
Explanation: Paralleled transformers must have the same voltage ratio and polarity so they do not circulate current, and similar percent impedance so they share load in proportion to kVA. Mismatched impedance dumps most of the load onto the lower-impedance unit.

About the SC Public Utilities Electrical Exam

The South Carolina Public Utilities - Electrical Contractor Examination is the official CLB classification examination administered by PSI. The official exam has 50 scored questions. Passing is 70% (35 of 50) in 3 hours. The examination is open book. PSI lists USD 60 (Candidate Information Bulletin updated 5/15/2025). The scope is limited to line construction for public and private companies, high-voltage work over 2,400 volts, and traffic-signal and highway-lighting work. This bank is an English-language MCQ study adaptation. It does not replace required trade experience, board approval, or the official examination.

Exam sponsor: PSI Services LLC (for the South Carolina Contractor's Licensing Board). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Open-book computer-based multiple-choice. Allowed references include the National Electrical Safety Code (C2-1997), the 2020 NEC with SC modifications, OSHA 29 CFR 1926, Lineman's and Cableman's Handbook (12th or 14th), American Electricians' Handbook (16th, 2013), and the South Carolina 811 Excavator Manual.

Time Limit

3 hours

Passing Score

70% (35 of 50)

Exam / Certification Fees

USD 60

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

12%

Transformers

Transformers (6 items)

10%

Electrical Knowledge

Electrical Knowledge (5 items)

10%

Conductors

Conductors (5 items)

14%

Overhead Lines

Overhead Lines (7 items)

8%

Underground Lines

Underground Lines (4 items)

16%

Equipment and Safety

Equipment and Safety (8 items)

6%

Grounding Methods

Grounding Methods (3 items)

8%

Service Drops and Laterals

Service Drops and Laterals (4 items)

8%

Poles and Structures

Poles and Structures (4 items)

8%

Electric Supply Stations

Electric Supply Stations (4 items)

Preparing for the SC Public Utilities Electrical Exam

What You Need to Know

  • Passing score: 70% (35 of 50)
  • Assessment: Open-book computer-based multiple-choice. Allowed references include the National Electrical Safety Code (C2-1997), the 2020 NEC with SC modifications, OSHA 29 CFR 1926, Lineman's and Cableman's Handbook (12th or 14th), American Electricians' Handbook (16th, 2013), and the South Carolina 811 Excavator Manual.
  • Time limit: 3 hours
  • Exam / certification fees: USD 60 Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

SC Public Utilities Electrical: Suggested Study Strategy

1Distribute study time to the official PSI content outline (bulletin updated 5/15/2025)
2Use only the PSI-listed references; temporary tabs such as Post-it notes are prohibited
3Pass Business Management and Law for Commercial Contractor in addition to this technical examination
4This bank is an English-language MCQ study aid, not an official PSI form

Frequently Asked Questions

How many questions are on the South Carolina Public Utilities - Electrical Contractor Examination?

The official PSI examination has 50 scored questions. Passing is 70% (35 of 50) within 3 hours (Commercial Contractor Candidate Information Bulletin updated 5/15/2025).

How much does this PSI examination cost?

PSI lists USD 60 for this examination. The South Carolina Contractor's Licensing Board charges a separate USD 350 license application fee for general and mechanical contractor licenses.

Is this examination open book?

Yes. PSI lists the South Carolina commercial contractor examinations as open book. Listed references include the National Electrical Safety Code (C2-1997) and the 2020 NEC with SC modifications.

What voltage threshold is in the Public Electrical Utility scope?

The PSI bulletin states the holder may perform high-voltage cable splicing and pulling wire for systems in excess of 2,400 volts, plus traffic-signal and highway-lighting work.