Impulse voltage tests on a 4.8-kv. distribution substation

DISTRIBUTION lines from ungrounded 4,800-volt substations of the Detroit Edison Company commonly have several hundred feet of three-phase underground cable between the overhead lines and the station, voltage regulators being connected between the bus and the station end of the cable. Although lightning arresters are connected at the substation bus and at the junctions of the overhead lines and entrance cables, a number of flashovers due to lightning voltage have occurred, consistently between the line terminal of the regulator and the station end of the entrance cable.