Sandy Pond Intertie, Massachusetts

The largest single source of electrical power in Massachusetts, is not a power plant but a high voltage cable that brings electricity directly from the James Bay hydro project in northern Quebec. The over 900 mile long, 450 kilovolt DC line enters the New England power grid at a 22-acre site called the Sandy Pond Converter Terminal, near Ayer, Massachusetts, where a variety of filters in the yard clean the electric signal as it comes in. The current then enters a large metal building, the electrical "valve hall," full of thrysters and quadra valves, which convert the power from Direct Current (used only occasionally by utility companies, to minimize current loss on especially long, uninterrupted transmissions) to Alternating Current. The voltage is then stepped down to 345 kilovolts, for distribution throughout New England.

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