1922 Installation of the World's Longest Submarine Power Transmission Line
In 1922, Sumitomo Electric Wire & Cable Works (present Sumitomo Electric Industries, Ltd.) successfully completed a project that was considered to be impossible with the technology of that time, namely the installation of a 21 km submarine cable from Niihama City, Ehime to an offshore island called Shisakajima.
A refinery was relocated to the uninhabited island of Shisakajima to avoid smoke hazards in 1905. After that, the cost of transporting coal for fuel to the coal-fired power plant in the island became a problem. There was a large hydropower plant on the opposite shore in Niihama and power transmission from it to the island would reduce the cost to one fifth. However, the world's longest submarine cable in those days, which was in San Francisco, was only 6.7 km long. There was no technology to install a submarine cable exceeding three times its length anywhere in the world.
Just then, the coal-fired power plant was damaged. It was decided to install a power transmission line from Niihama to the island and the whole project ranging from the design and production of the cable to the installation was delegated to Sumitomo Electric Wire & Cable Works. The company thoroughly studied submarine cables in the United States and Europe and concentrated the experience and knowledge to complete a high-performance cable full of originality and ingenuity. Overcoming a series of problems, such as suspension of the work due to rainstorms and malfunction of the cable, underwater installation work was carried out over 20 days to successfully install the world's longest submarine cable of that time. This experience dramatically improved the submarine cable technology of Sumitomo Electric Wire & Cable Works.