High-voltage metal-clad apparatus comprising a capacitive voltage divider

Claim 1

Electrical apparatus rated for a predetermined high voltage comprising : a. a linearly extending high voltage conductor; b. a metal cylindrical enclosure coaxially surrounding and spaced apart from said conductor; c. a pressurized dielectric gas in said enclosure; d. capacitive voltage divider means including an electrode interposed between said enclosure and a section of said conductor in capacitive association with the latter, a measuring capacitance coupled to said electrode so as to acquire a low voltage when said conductor is high voltage energized, output means connected to said capacitance; e. means to isolate said section of said conductor; and f. calibrating means to accurately determine the reduction ratio of said capacitive voltage divider means by application of a relatively low test voltage to said section, said calibrating means comprising a withdrawable test probe movable into and out of engagement with said section, and insulating bushing means traversing said enclosure and having a through conductor electrically connected to said probe to apply said test voltage through said probe to said section, said bushing means rated for a voltage substantially lower than said predetermined rated high voltage of said apparatus.