Study of environmental impact of underground electric transmission systems

The project was undertaken to examine present practices in underground power transmission, identify environmental impacts associated with those practices, and develop guidelines for reducing impacts where possible. Four basic types of underground transmission cable in commercial use were studied: high pressure oil filled (HPOF) pipe type, low medium pressure oil-filled (LPOF) self contained, extruded dielectric, and gas dielectric (SF6) cable systems. Both alternating current (AC) and direct current (DC) were considered in transmission voltages from 115 to 500 kilovolts (kV). The environmental analysis considers site conditions typical of those found throughout the U.S. The complete spectrum of impact-causing activities was evaluated.