Method and apparatus for cable conductor shield fault detection
AssigneeSouthwire Company
InventorsEdward B. Joy, Athanasios P. Meliopoulos, Roger P. Webb
Life of this patent
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Abstract
Disclosed is an apparatus and method for continuously detecting skips, protrusions, protuberances and other defects in cable conductor shield, comprising a high voltage electrode, a capacitance bridge filter circuit and a corona discharge detector. A noncontacting coaxial electrode is employed to create an electric field between the cable conductor and the electrode. In the presence of this field, defects in the shield produce corona discharges. A detection circuit employing a capacitance bridge is employed to continuously detect corona discharges and produce signals used for subsequently locating the positions of the defects on the finished cable.
Claims19
Apparatus for detecting defects in a semi-conductive conductor shield of unfinished high voltage cable which is continuously advanced along a path of travel, comprising:
- means, including a high voltage electrode arranged in non-contacting relation around said continuously advancing cable, for applying high voltage power concentrically around said continuously advancing cable to produce an electric field around said cable, the magnitude of said high voltage power being selected such that the electric field intensity existing in the air gap between the shielded cable and the inner cylindrical surface of the electrode approaches, but is less than, the electrical breakdown value for the air in the gap;
- means connected to said means for applying high voltage power for detecting the resultant electrode current having a corona discharge component caused by field strength changes in said electric field resulting from defects in said conductor shield;
- means connected to the detecting means for filtering said resultant electrode current to eliminate any low frequency components thereof and produce a corona current signal corresponding to said corona discharge component;
- means arranged downstream of said means for applying high voltage power for applying insulation about said unfinished high voltage cable;
- and
- means connected to the means for filtering said resultant electrode current for indicating the presence of at least one of a skip, protrusion, protuberance and other defect in said conductor shield upon receiving said corona current signal.
A method of detecting defects in the semi-conductive conductor shield of unfinished high voltage cable which is continuously advanced along a path of travel, comprising the steps of:
- applying high voltage power concentrically around said continuously advancing cable utilizing a high voltage electrode arranged in non-contacting relation around said continuously advancing cable to produce an electric field around said cable, the magnitude of said high voltage power being selected such that the electric field intensity existing in the air gap between the shielded cable and the inner cylindrical surface of the electrode approaches, but is less than, the electrical breakdown value for the air in the gap;
- detecting the resultant electrode current having a corona discharge component caused by field strength changes in said electric field resulting from defects in said conductor shield;
- filtering said resultant electrode current to eliminate any low frequency components thereof and produce a corona current signal corresponding to said corona discharge component;
- applying insulation about said unfinished high voltage cable subsequent to detecting changes in said electric field;
- and
- indicating the presence of at least one of a skip, protrusion, protuberance and other defect in said conductor shield in correspondence with said corona current signal.
Dependencies are inferred from the claim text.