Jeju 1 (Haenam–Jeju)

The Jeju 1 HVDC project, also known as the HVDC Haenam–Cheju system, is the first high-voltage direct current transmission link connecting the Korean Peninsula to Jeju Island in South Korea. This bipolar HVDC system went into service in 1996 and is owned and operated by Korea Electric Power Corporation (KEPCO).

Technical Specifications

The HVDC link consists of two 180 kV cables with a maximum transmission capacity of 300 megawatts. The total length of the connection is 101 kilometers, with the first 5 kilometers on the Korean mainland being underground, while the rest is partially buried under the sea bed.

The system uses Line Commutated Converter (LCC) technology. Each pole of the bipolar system consists of a single 12-pulse converter bridge. The thyristor valves used in the system are designed to operate with a minimum power down to zero, compared to the usual minimum of 5-10% in conventional HVDC systems.

Converter Stations

The two converter stations are at Haenam and Jeju island. Due to the proximity of the Jeju station to the sea, all equipment, including AC harmonic filters, is installed indoors to prevent corrosion and pollution-related flashovers from sea salt.

Control and Operation

The Jeju 1 HVDC system incorporates several unique design features to enable its use as the sole power source for Jeju Island when necessary. The control characteristics are reversed from conventional practice, with the inverter (Jeju) station controlling current and the rectifier (Haenam) station controlling DC voltage. This arrangement allows for rapid control of received power without relying on telecommunications to the mainland.

The system is equipped with synchronous compensators that provide the required reactive power and commutation voltage when no generation units are operating on Jeju. These compensators can be started with gas turbines, allowing the HVDC transmission scheme to start and run when no local generation is available on the island.

System Upgrades

In 2020, GE Vernova completed an upgrade to the Jeju 1 HVDC link. This upgrade included the installation of GE's advanced H450 Line Commutated Converter valve technology, as well as improvements to the control system and cooling system. The upgraded control system now uses GE's latest algorithms for maintaining grid frequency, providing higher reliability and more robust operational control.

The Jeju 1 HVDC system plays an important role in South Korea's energy infrastructure, enabling efficient power transfer between the mainland and Jeju Island, and supporting the integration of renewable energy sources in line with the country's energy transition goals.