Hida-Shinano

The Hida-Shinano high voltage direct current link currently under construction connects the 50-Hz Shin Shinano substation of TEPCO Power Grid, Inc. to the 60-Hz Hida converter station of Chubu Electric Power Grid Co., Inc. It is the first such project in Japan in which an HVDC link connects via overhead lines between grids operating at different frequencies and with different manufacturers supplying the systems at each end. Hitachi supplied the converter system at Hida converter station, whilst Toshiba supplied the converter system at the Shinano end.

The station has a relatively high altitude of 1,085 m.

Hida-Shinano HVDC Link runs over 89 km of overhead lines connecting the Shin Shinano substation of TEPCO Power Grid, Inc. in Nagano Prefecture to the new Hida converter station of Chubu Electric Power Grid Co., Inc. in Gifu Prefecture. The link has a capacity of 900 MW (2 × 450-MW poles) and operates at a DC line voltage of 200 kV.

This HVDC system involves two different manufacturers – Hitachi and Toshiba - with Shin Shinano substation as the master station and Hida converter station as the secondary station. The overall system relies on cooperative control between the systems at each end for things like starting and stopping the link, the exchange of signals for protection interlocking, and the timing of protection mode initiation. Accordingly, simulation trials were conducted at Shin Shinano substation during 2018 that simulated the two manufacturers’ control and protection systems. This was followed by connection testing, which commenced after installation of the converter and its control and protection systems and is still in progress.

Electricity transmission in Japan is unusual because the country is divided for historical reasons into two regions each running at a different mains frequency. Eastern Japan has 50 Hz networks while western Japan has 60 Hz networks. Limitations of conversion capacity causes a bottleneck to transfer electricity and shift imbalances between the networks.

Eastern Japan runs at 50 Hz; Western Japan runs at 60 Hz. This originates from the first purchases of generators from AEG for Tokyo in 1895 and from General Electric for Osaka in 1896. The frequency difference partitions Japan's national grid and so power can be moved only between the two parts of the grid using HVDC back-to-back converters, or transmission lines.