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Exam Review

Key Facts: Engineer Electric Railway Exam

80 items

Official written exam paper length (4 subjects × 20)

Q-Net Engineer Electric Railway qualification standard (jmCd 1741)

120 minutes

Written examination duration (30 minutes per subject)

Q-Net 필기시험 접수안내 (기사·산업기사 과목별 30분)

40 / 60

Passing standard: 40% individual subject floor (과락) and 60% overall average

National Technical Qualifications Act Enforcement Rules

KRW 19,400

Written exam registration fee

Q-Net 전기철도기사 page, checked 2026-09-20

KRW 22,600

Practical exam registration fee (2-hour 필답형)

Q-Net 전기철도기사 page, checked 2026-09-20

2 years

Exemption duration for written test pass

National Technical Qualifications Act Enforcement Decree Article 21

전기철도기사 is South Korea's benchmark Engineer-grade qualification in electric railway traction engineering (jmCd 1741, MOLIT / HRD Korea). The official written CBT exam comprises 80 MCQs across four subjects (20 per subject, 30 min each, 120 min total) requiring a 40% per-subject floor and 60% overall average, followed by a 2-hour written descriptive practical exam (필답형) in electric railway practice. Official Q-Net fees are KRW 19,400 (written) and KRW 22,600 (practical). OpenExamPrep provides an independent 100-question English MCQ practice bank.

Sample Engineer Electric Railway Practice Questions

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

1According to KR Code KR E-01050 (전기방식), what is the standard electrification system for Korean national railway lines, and what DC exception is permitted?
A.Single-phase AC 20 kV, 50 Hz; DC exception 750 V
B.Single-phase AC 25 kV, 60 Hz; DC exception 1,500 V
C.Three-phase AC 22.9 kV, 60 Hz; DC exception 3,000 V
D.Single-phase AC 15 kV, 16.7 Hz; DC exception 1,500 V
Explanation: KR E-01050 states that the electric railway electrical system shall be single-phase AC 25 kV, 60 Hz, and that a DC system, when used, shall be DC 1,500 V. Korean commercial frequency is 60 Hz, which distinguishes this MOLIT/KR practice from 50 Hz or 16.7 Hz networks used in parts of Europe. OpenExamPrep independent practice uses this KR Code wording as study material, not as an official Q-Net paper.
2Under Article 36 of the Urban Railway Construction Rule (도시철도건설규칙 제36조), what voltage and contact-line arrangement is specified for the traction contact line (전차선로) of a standard urban railway?
A.DC 750 V third-rail collection as the default for all urban railways
B.AC 25 kV overhead contact line for every urban railway including metros
C.DC 1,500 V overhead contact line (가공선식)
D.AC 6,600 V overhead contact line shared with station lighting
Explanation: 도시철도건설규칙 제36조(전기방식) lists 전차선로 as DC 1,500 V overhead (가공선식). High-voltage station feeders, lighting, and signalling supplies are listed separately and must not be confused with the traction contact-line voltage. Light-rail third-rail exceptions live in Article 79, not in the default Article 36 rule.
3In the autotransformer feeding system (AT급전방식 / 단권변압기방식) required by KR E-01050, which voltage set describes the catenary, feeder, and rail relationships?
A.Catenary-to-rail 12.5 kV, feeder-to-rail 12.5 kV, catenary-to-feeder 25 kV
B.Catenary-to-rail 25 kV, feeder-to-rail 25 kV, catenary-to-feeder 50 kV
C.Catenary-to-rail 25 kV, feeder-to-rail 0 V, catenary-to-feeder 25 kV
D.Catenary-to-rail 50 kV, feeder-to-rail 25 kV, catenary-to-feeder 75 kV
Explanation: KR E-01050 defines AT feeding as 25 kV between the feeder and rail and between the catenary (전차선) and rail, with 50 kV between the catenary and the feeder. The autotransformer (단권변압기) mid-point is bonded to the rails and the non-insulated protective wire (FPW), so the train still sees a 25 kV contact-to-rail voltage while the feeder carries the opposite polarity.
4What is the principal purpose of a booster transformer (흡상변압기, BT) in an AC electric-railway feeding circuit?
A.To raise the catenary voltage from 25 kV to 50 kV for high-speed trains
B.To convert three-phase KEPCO supply into two 90-degree single-phase circuits
C.To force return current into the negative feeder (부급전선) and reduce inductive interference in nearby communication lines
D.To provide regenerative paths from the DC rectifier back into the 154 kV grid
Explanation: KR E-01050 describes BT feeding as installing a contact wire and a negative feeder (부급전선) with booster transformers about every 4 km in series. The 1:1 booster transformer (흡상변압기) magnetically couples catenary current to the negative feeder so return current is sucked out of the rails, reducing earth return and inductive interference on parallel telecommunication circuits.
5Why do Korean AC traction substations commonly use a Scott-connected main transformer (스코트 결선 주변압기)?
A.To create two single-phase traction supplies (M-phase and T-phase) displaced by 90 electrical degrees and thereby reduce three-phase unbalance on the KEPCO incoming supply
B.To double the catenary voltage by autotransformer action inside the substation
C.To provide a path for DC stray current back to the rectifier negative bus
D.To operate as a 1:1 series booster on the contact wire
Explanation: A Scott connection transforms a three-phase source into two single-phase outputs (M상 and T상) that are 90° apart. Feeding adjacent catenary sections from M and T phases spreads the single-phase railway load across all three incoming phases and lowers negative-sequence unbalance seen by KEPCO. The teaser (T) winding uses √3/2 of the main (M) winding turns so the two traction voltages are equal.
6In a simple catenary overhead contact system (심플 커티너리), which three conductors or fittings carry the mechanical load and the sliding contact current?
A.Messenger wire (조가선), contact wire (전차선), and droppers (드로퍼 / 행거)
B.Negative feeder (부급전선), protective wire (보호선), and running rails only
C.Rigid conductor rail (강체전차선), third rail, and balance weights
D.Feeder messenger, earth wire, and cantilever pipe with no contact wire
Explanation: A simple catenary suspends a contact wire (전차선) from a messenger wire (조가선) by droppers (드로퍼). The messenger takes most of the sag and tension variation, while the contact wire presents a nearly level sliding surface to the pantograph. Compound (콤파운드) catenary adds an auxiliary messenger; rigid overhead (강체전차선) replaces the flexible wires with a conductor bar.
7Why is staggered (zigzag) stagger, or 편위, applied to an overhead contact wire relative to the track centre line?
A.To raise the electrical clearance to bridges without changing system height (가고)
B.To spread pantograph-carbon wear evenly across the collector strip instead of grooving one path
C.To force return current into the negative feeder in a BT section
D.To keep mid-span sag equal to 1/8 of the span regardless of tension
Explanation: Stagger (편위) offsets the contact wire alternately left and right of the track centre at successive supports. The pantograph then sweeps across the carbon strip, preventing a single groove and extending collector life. Stagger must still keep the wire inside the pantograph working width after wind deflection and vehicle roll.
8What is the function of a phase-break or system-change dead section (절연구간) on Korean AC or AC/DC railways?
A.A short overlap of live wires that the pantograph briefly parallels so that DC feeders can be paralleled without a gap
B.An electrically dead overhead interval that isolates different feeding phases or AC and DC systems so a pantograph does not short them together
C.A mechanical tensioning device that keeps contact-wire tension constant with temperature
D.A buried drainage cable that collects DC stray current
Explanation: A 절연구간 is a dead (neutral) overhead section. On AC lines it separates adjacent feeding phases or Scott M/T sections; on dual-voltage urban lines it separates AC 25 kV from DC 1,500 V. The train must coast or switch onboard circuits while the pantograph passes the dead interval so the two live systems are never bridged.
9KR E-01050 lists incoming receiving voltages of 22.9 kV, 154 kV, and 345 kV. Which incoming voltage is identified as the Korean electric-railway standard, and which legacy voltage may still appear on older lines?
A.Standard 345 kV, legacy 22.9 kV
B.Standard 154 kV, with some existing 66 kV supplies still in service
C.Standard 22.9 kV, legacy 765 kV
D.Standard 66 kV for every new high-speed substation
Explanation: The KR E-01050 commentary states that KEPCO transmission voltages include 66, 154, 345, and 765 kV, that electric railways take 154 kV as the standard incoming supply, and that some 66 kV supplies remain in service. New design therefore starts from 154 kV unless site constraints force another listed nominal voltage.
10In Korean AT feeding, about how far apart are autotransformers typically placed, and to what are the AT mid-points connected?
A.About 1 km apart, mid-points floating with no rail bond
B.About 10 km apart, mid-points connected to the rails and the non-insulated protective wire (FPW)
C.About 30 km apart, mid-points connected only to the 154 kV incoming bus
D.About 4 km apart, mid-points connected only to the negative feeder of a BT circuit
Explanation: KR E-01050 commentary places autotransformers at about 10 km intervals. Each AT winding mid-point is connected to the rails and the non-insulated protective wire (FPW), and a protective-wire jumper (CPW) bonds FPW to rail near the mid-point between ATs. That arrangement returns traction current and reduces induced voltages on nearby circuits.

About the Engineer Electric Railway Exam

Engineer Electric Railway (전기철도기사) is South Korea's premier Engineer-grade national technical qualification in railway electrification systems, overhead catenary design, traction power substations, and rail structural engineering, administered by the Human Resources Development Service of Korea (HRD Korea / Q-Net) under the Ministry of Land, Infrastructure and Transport (MOLIT). The written examination assesses 80 four-option multiple-choice questions across four core subjects: Electric Railway Engineering (전기철도공학), Electric Railway Structure Engineering (전기철도 구조물공학), Electromagnetics (전기자기학), and Power Engineering (전력공학). Candidates passing the written paper advance to a 2-hour written descriptive practical examination (필답형) in 전기철도 실무 (Electric railway practice). OpenExamPrep provides an independent English-language MCQ study adaptation tailored for mastering core traction principles, rigorous mechanical and electrical calculations, and dual Korean-English technical terminology.

Exam sponsor: HRD Korea (Q-Net) / Ministry of Land, Infrastructure and Transport (MOLIT). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Written paper covering 전기철도공학 (Electric Railway Engineering), 전기철도 구조물공학 (Electric Railway Structure Engineering), 전기자기학 (Electromagnetics), and 전력공학 (Power Engineering) with 20 items and 30 minutes each (80 items / 120 minutes total), followed by a 2-hour, 100-point written descriptive practical examination in 전기철도 실무. OpenExamPrep study weights cover all four written subjects with 25 questions each.

Time Limit

120 minutes for the four written subjects (30 minutes each); practical: 2 hours written descriptive sitting

Passing Score

Written: 40+ per subject (과락 floor) and 60 average; practical: 60/100

Exam / Certification Fees

KRW 19,400 written / KRW 22,600 practical (Q-Net, 2026-09-20)

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

Official sources

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.

25%

Electric Railway Engineering (전기철도공학)

Traction power supply systems (DC 1,500 V vs AC 25 kV 60 Hz), Auto Transformer (AT) and Booster Transformer (BT) feeding schemes, neutral sections and automatic changeover, overhead catenary styles (simple, stitched, compound, rigid R-bar), contact and messenger wire specifications, dropper spacing and length calculations, stagger/zigzag for pantograph wear equalization, wave propagation velocity c = √(T/m), Doppler parameter, pantograph contact force and uplift, Scott-connected transformers, and traction substation converters.

25%

Electric Railway Structure Engineering (전기철도 구조물공학)

Catenary support masts (galvanized steel pipe, H-beam, concrete poles, steel lattice), cantilever bracket assemblies, steady arms, foundation block overturning stability factor of safety, allowable soil bearing capacity, catenary mechanical tension T and sag formula S = (w·L²)/(8·T), wind pressure load calculations, ice loading, balance weight and spring automatic tension balancing devices, thermal expansion compensation ΔL = α·L·Δt, rolling stock kinematic gauges, static/dynamic electrical clearances, lightning shield wires, surge arresters, and rail potential control.

25%

Electromagnetics (전기자기학)

Electrostatic field theory, Coulomb's law, Gauss's law, conductor-to-earth capacitance, magnetostatics, Biot-Savart law, Ampere's circuital law, magnetic field intensity and flux density, Faraday's law of induction, self and mutual inductance in catenary and rail circuits, electrostatic induction voltage on telecommunication lines Vs = (Cs / (Cs + Ce))·V, electromagnetic induction voltage Vm = ω·M·I·L·K, screening factor K of return wires and rails, skin and proximity effects in AC conductors and steel rails, and DC stray current leakage and electrolytic corrosion mitigation.

25%

Power Engineering (전력공학)

154 kV high-voltage subtransmission grid interfacing, three-phase grid voltage unbalance ratio from single-phase railway loads, KEPCO 3% negative-sequence voltage limit, reactive power compensation (SVC, STATCOM), active harmonic filtering, feeder short-circuit fault analysis (catenary-to-rail, catenary-to-feeder), reactance-based fault locators X = 2πfL·d, protective relay schemes (directional distance relays, differential protection, overcurrent relays), GIS and vacuum circuit breakers, high-speed DC circuit breakers (HSCB), and substation grounding grid safety.

Preparing for the Engineer Electric Railway Exam

What You Need to Know

  • Passing score: Written: 40+ per subject (과락 floor) and 60 average; practical: 60/100
  • Assessment: Written paper covering 전기철도공학 (Electric Railway Engineering), 전기철도 구조물공학 (Electric Railway Structure Engineering), 전기자기학 (Electromagnetics), and 전력공학 (Power Engineering) with 20 items and 30 minutes each (80 items / 120 minutes total), followed by a 2-hour, 100-point written descriptive practical examination in 전기철도 실무. OpenExamPrep study weights cover all four written subjects with 25 questions each.
  • Time limit: 120 minutes for the four written subjects (30 minutes each); practical: 2 hours written descriptive sitting
  • Exam / certification fees: KRW 19,400 written / KRW 22,600 practical (Q-Net, 2026-09-20) 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

Engineer Electric Railway: Suggested Study Strategy

1Master the distinction between AT and BT feeding schemes: Auto Transformer (AT) systems operate at 2×27.5 kV (55 kV between feeder and catenary) with AT spacings of 10–15 km and virtually eliminate inductive interference, whereas Booster Transformer (BT) systems operate at 25 kV with suction transformers spaced every 4 km requiring section insulators and are phased out on modern high-speed lines.
2Drill catenary mechanical and wave formulas: Memorize the wave propagation velocity formula c = √(T/m), the sag formula S = (w·L²)/(8·T), and the thermal expansion elongation formula ΔL = α·L·Δt. Ensure units are converted correctly (e.g., tension in N, mass in kg/m, span in meters).
3Prioritize electromagnetic induction calculations: Focus on mutual induction voltage Vm = ω·M·I·L·K and electrostatic induction voltage Vs = (Cs / (Cs + Ce))·V. Remember that the screening factor K represents the reduction ratio (a lower K means superior shielding).
4Understand grid unbalance and fault locators: Review how single-phase traction loads connected across two phases of a 154 kV three-phase supply create negative-sequence voltage unbalance, and how Scott transformers convert 3-phase to two 90°-shifted single phases (M-phase and T-phase) to balance substation loading.

Frequently Asked Questions

What is Engineer Electric Railway (전기철도기사)?

It is South Korea's official national technical qualification (jmCd 1741) for engineers responsible for the design, construction, supervision, and maintenance of railway traction electrification networks, overhead catenary systems, traction power substations, and electrical railway structures. The exam is administered by HRD Korea under the authority of the Ministry of Land, Infrastructure and Transport (MOLIT).

How is the official examination structured in 2026?

The official examination consists of two consecutive stages: (1) A written CBT examination featuring 80 four-option multiple-choice questions across 4 subjects (20 questions each, 120 minutes total), graded on a 40-point per-subject floor and 60-point overall average; and (2) A 2-hour written descriptive practical examination (필답형) in 전기철도 실무 (Electric railway practice) scored out of 100 points, requiring 60 points to pass.

What language is the official exam administered in, and what is this study bank?

The official Q-Net examination is administered entirely in Korean at test centers in South Korea. This OpenExamPrep bank is an independent English-language adaptation created for bilingual engineers, overseas professionals, and domestic candidates seeking conceptual clarity and formula mastery. All technical terms include their standard Korean terminology in parentheses (e.g., AT급전방식, 흡상변압기, 조가선, 전차선).

What are the registration fees and validity periods?

As verified on Q-Net for the 2026 exam cycle, the written exam fee is KRW 19,400 and the practical exam fee is KRW 22,600 (totaling KRW 42,000). Under Article 21 of the Enforcement Decree of the National Technical Qualifications Act, candidates who pass the written paper receive a 2-year exemption from repeating the written examination.

What are the most challenging subjects and key calculation topics?

Candidates consistently find Electric Railway Engineering (전기철도공학) and Electromagnetics (전기자기학) the most challenging due to multi-step quantitative problems. Crucial calculations include Auto Transformer (AT) neutral section voltage drops, wave propagation speeds c = √(T/m), catenary sag S = (w·L²)/(8·T), mutual inductance screening factors K, and traction substation three-phase unbalance voltage ratios.