HVDC Converter Station Construction in Korea: Converter and Control Systems

HVDC converter station construction in Korea covers installing the converters, control and monitoring systems and ancillary equipment for high-voltage direct current transmission. HVDC converts AC to high-voltage DC for transmission and back to AC at the receiving end, and is used for long-distance and submarine links or to connect separate grids. Converter stations contain equipment you will not find in an ordinary substation — thyristor valves, converter transformers, filters and smoothing reactors — so you need to understand what each item does. This guide covers two stages: converter equipment and control systems.

Contents

• Common Pre-Work Review
• 1. Converter Equipment
• Key HVDC Converter Station Equipment
• 2. Control and Monitoring Systems
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Review the construction approval, single-line diagrams, thyristor valve and auxiliary specifications, sequence and block diagrams, earthing design and drawings, oil containment drawings and the Korea Electrical Safety Corporation (KESCO) inspection procedures. All work follows the design, method statement, work procedures and manufacturer drawings. Prepare a level, insulation tester, power factor test set and torque wrench; workers wear insulated helmets, flame-resistant clothing, insulated boots and harnesses.

1. Converter Equipment

1. In the valve hall, install thyristor valves and modules, arresters, wall bushings, buses, fiber-optic cables and earthing terminals.
2. In the DC hall, install smoothing reactors, voltage dividers, disconnectors, earthing switches and DC cable terminations.
3. In AC and DC filter rooms, install supply buses and earthing switches for capacitors, reactors, resistors, CTs and VTs.
4. Install pumps, fans, sensors and indicators for cooling and HVAC, and connect power and control cables.
5. Install breakers, switches and operating panels and wire control cables to suit their functions.
6. Review converter transformer specifications and drawings, install it to suit rating, vector group and cooling, and wire the tap changer and protection.
7. Build the main circuit — metallic return, power cables and transfer buses — for monopole, bipole or double monopole operation.
8. Install electrode equipment: electrodes, reactors, disconnectors and local panels.

Thyristors and damping resistors are very heat-sensitive, so cooling must work exactly as designed. The valve-side windings of a converter transformer are unearthed and carry DC bias, so their insulation differs from a standard transformer’s.

Key HVDC Converter Station Equipment

Equipment	Role
Thyristor valve	Core AC/DC switching; valve bridges connect three-phase AC and the DC line
Converter transformer	Supplies the AC voltage needed for rectification and inversion; earthed star on AC side, unearthed star and delta on valve side
Load tap changer (LTC)	Controls DC voltage; per the NCS, steps of 1–2% over about a 20% range
AC harmonic filter	Diverts converter harmonic currents to limit AC voltage distortion
Smoothing reactor	Smooths DC ripple, limits surges into the valve hall and current rate of change
DC filter	Used on overhead DC lines (not needed for back-to-back or cable links)
DC arrester	Protects valves and valve structures from overvoltage
Reactive power supply	Converters consume reactive power of about 50–60% of transmitted active power
DC voltage divider	Measures DC voltage for control, protection and monitoring
Break-over diode (BOD)	Protects thyristors from forward overvoltage or loss of gate electronics

This summarizes explanations in the NCS competency unit. Actual specifications follow the project specification and manufacturer drawings.

2. Control and Monitoring Systems

1. Confirm the central control system architecture.
2. Review control configuration, control methods and monitoring.
3. Install bipole control, status recording and interlock panels, and run communication and instrumentation cables to the central controller.
4. Review and install control, signal and telephone circuits for video and waveform monitors.
5. Install converter control and protection relay cubicles and remote monitoring wiring.
6. Install CCPI, valve base electronics (VBE) and measurement cubicles and remote monitoring wiring.
7. Install transient fault recorder and distributed I/O cubicles and remote monitoring wiring.

FAQ

Reference Standards

• Electricity Business Act (전기사업법) — law.go.kr
• Electrical Safety Management Act (전기안전관리법) — law.go.kr
• Electric Technology Management Act (전력기술관리법) — law.go.kr
• Electrical Construction Business Act (전기공사업법) — law.go.kr
• Occupational Safety and Health Act (산업안전보건법) — law.go.kr
• Korea Electro-technical Code (KEC, 한국전기설비규정) — law.go.kr
• Technical Standards for Electrical Equipment (전기설비기술기준) — law.go.kr
• KEPCO design standards and substation construction practice; Korean Industrial Standards (KS)
• NCS competency unit HVDC Converter Station Construction (고압 직류송전(HVDC) 변환설비공사, 1901070319_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistake is approaching HVDC like an ordinary substation and missing the needs of valve cooling or converter transformer valve-side insulation. Converter work depends on the layout of the valve hall, DC hall and filter rooms and the main circuit for each operating mode; control work on each cubicle’s role and remote monitoring wiring. Related guides: Reactive Power Compensation Installation, Energy Storage (EES/ESS) Installation, Digital Substation System Installation. A Korean version of this guide is available here.

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This article restructures the Korean NCS competency unit ‘HVDC Converter Station Construction’ (고압 직류송전(HVDC) 변환설비공사, code 1901070319_22v2) as a practical reference. Actual work must follow applicable standards and the judgment of qualified professionals; always confirm specific values, deadlines and criteria against the latest regulations and client standards.

Written/reviewed by VOLT · Last updated 2026-10-26