Solid dielectric cables for underwater power transmission

Following the very successful application of extruded polyethylene insulation to coaxial submarine telephone cables, the first high voltage power transmission circuit using this insulation under water was energized in 1968 at Cook Inlet, Alaska. The accumulated experience with 138 kV solid dielectric submarine cables now amounts to nearly 30 circuit-mile-years without a single electrical underwater fault. The major advantages of this new form of cable are simplicity in construction, easier installation, and lower electrical capacitance and thermal impedance. The critical length of a 138 KV cable with 2000 MCM conductor is 150-200 miles, depending on sediment thermal resistivity. Extruded polyethylene insulation, therefore, makes it possible to transmit ac power over long distances under water.