In 1960 Great Lakes Power installed four submarine cables to carry power from the mainland to St. Joseph Island in the North Channel of Lake Huron.The service, 730 m in length, is 34.5 kV. Three of the singlephase cables are in regular use, the fourth acts as a backup.

In 1977 the installation failed for the first time, requiring replacement of a pothead. With the cables approaching the end of their useful life, GLP asked Hatch Energy to assess their condition and make recommendations for future action. We examined the condition of the asset, and carried out partial discharge tests on the cables.The client accepted our report, which presented a number of viable options.