Hokkaido-Honschu

The Hokkaido-Honshu HVDC link connects the islands of Hokkaido and Honshu in Japan. The original link, commissioned in 1979, was designed to interconnect the power grids of these two major Japanese islands.

Technical Specifications

The initial Hokkaido-Honshu HVDC link had a transmission capacity of 300 MW, operated at a DC voltage of ±250 kV, and had a rated current of 1200 A. The total length of the link spanned 193 km, comprising 149 km of overhead line and 44 km of submarine cable. The system employed thyristor converters for AC/DC conversion and was configured as a monopolar HVDC line, utilizing a single conductor for power transmission with an earth return.

Converter Stations

The two converter stations are the Nanae Converter Station in Hokkaido, and the Kamikita converter station in Honshu.

Cable Terminal Stations

The link incorporates two cable terminal stations to facilitate the transition between overhead lines and submarine cables.

System Upgrades

In 1993, the transmission capacity of the Hokkaido-Honshu HVDC link was increased to 600 MW. This upgrade involved the installation of a second cable, effectively doubling the original capacity. Later, in 2012, the first cable, which had deteriorated over time, was replaced with a modern DC XLPE (Cross-Linked Polyethylene) cable. This replacement maintained the total power transmission capacity at 600 MW while improving reliability and efficiency.

Technical Advancements

The Hokkaido-Honshu HVDC link has incorporated several technical advancements over its operational life. These improvements include the implementation of light-triggered thyristors and the utilization of advanced control and protection systems. These enhancements served to improve the system's performance, reliability, and efficiency over time.

Purpose and Benefits

The Hokkaido-Honshu HVDC link served multiple important purposes. It enabled power interchange between Hokkaido and Honshu, provided a stable power supply to Hokkaido during periods of high demand.

This HVDC link played an important role in enhancing the stability and reliability of Japan's power grid, allowing for more efficient use of generation resources and improved management of power supply and demand across the two islands.