Sault Ste. Marie, Michigan
September 1, 2000

Don Sawruk, President
(906) 632-5150

Edison Sault Electric Company has delivered to the Michigan Public Service Commission its report on the cause of last month's service outage on Mackinac Island.

The report which included the findings of three independent consultants, concludes that the failure of the submarine cables that serve the Island was most likely caused by the thermal breakdown of cable insulation in those portions of the submarine cable that were installed on land. Contributing to the thermal breakdown was magnetic heating of the steel armor wires due to the proximity of the cables to each other and the inability of the cables to dissipate heat due to the unusually dry soil conditions.

Edison Sault Electric, with help from several outside contractors, has rebuilt the land based portions of the submarine cables which had failed both on Mackinac Island and St. Ignace. These new portions of the electric delivery system to Mackinac Island are now tied to the existing water based submarine cables and are presently serving the Island. However, the water based submarine portions of the cable have been stressed and are working under reduced capacity. Diesel generators remain on the Island as a source of backup generation and will continue to remain on the Island until such time as Edison Sault is satisfied that the system serving the Island will continue to do so reliably.

Edison Sault Electric, working in conjunction with its engineering consultants and also consultants for the City of Mackinac Island, is in the process of securing new submarine cables to be placed in the water as soon as possible. Current plans call for two new (I 7Nfw each - a total of 34MW) submarine cable circuits to be installed by the end of 2001. Edison Sault is also examining a number of related issues to further improve the entire distribution system on the Island.

Mackinac Island Outage Report

To contact Customer Service, send mail to customerserv@edisonsault.com.

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Last modified: August 16, 2002