December 1, 2009

Top Plants: Edison Sault Hydroelectric Plant Sault Ste. Marie, Michigan

Angela Neville, JD

Current Plant Overview

The powerhouse is 1,340 feet long (¼ mile) and 80 feet wide. It contains 74 three-phase horizontal turbine generators, with each generator operating at 4,400 V, 180 rpm, and producing between 600 and 850 kVA. Each turbine has four runners, or blades, which drive the 60-cycle generators that produce the electricity. The turbine units are rated at 772 to 935 hp at 20 feet of headwaters falling from the upper St. Marys River to the lower river.

Of the 74 turbines, 41 were installed in 1902 and the other 33 were installed in 1915 and 1916. Three turbine manufacturers — Jolly McCormick; S. Morgan Smith; and Wellman, Seaver & Morgan — built the turbines, but none of these companies is in still in business. As a result of the absence of original turbine manufacturers, plant personnel have to machine many replacement parts in-house.

The length of the canal from the headgates (intake) to the powerhouse is approximately 11,850 feet (2¼ miles). The canal varies in width from 200 to 220 feet at water level and is approximately 24 feet in depth. Water velocity, which is 7 to 10 feet per second, varies for assorted reasons. At times the water moves at speeds up to 7 mph.

The entrance to the canal, which is located at the eastern end of Ashmun Bay, is controlled by four steel headgates. The upper quarter of the canal was excavated out of rock, with the balance of the canal dug into the earth and lined with timber. The canal is designed to handle 30,000 cubic feet per second (cfs) of water.

In an October interview, POWER asked Ernie Maas, vice president of engineering and operations at Edison Sault Hydroelectric Plant, to describe the plant’s current maintenance/mechanical staff. He explained that it consists of one hydro superintendent, one foreman, one electrician, one machinist, one welder, and four maintenance workers who work 8 to 4:30, Monday through Friday.