Abstract Apparatus for reducing the resistance of a high resistance fault between two cores or between one core and the sheath of an electrical cable comprising a first transformer having a high open circuit voltage rating and a low short circuit current rating and a second transformer having a low open circuit voltage rating and a high short circuit current rating. The two transformers are connected in series and across the two faulty cores or between the faulty and the sheath and their respective primary windings are energized. Initially the sum of the two secondary voltages will be applied to the cable to reduce the fault resistance. This will cause the fault current to increase. When the fault current increases beyond the short circuit current rating of the first transformer this transformer will zero leaving only the second transformer to burn the fault down to a point where conventional fault locating apparatus can be employed to locate the fault.
Inventors
👤 Frank Edward Jenkinson
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-03 13:14
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/08
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
152 words
Apparatus for reducing the resistance of a high resistance fault in an electrical cable, comprising a first transformer having a predetermined open circuit voltage rating and short circuit current rating, a second transformer having an open circuit voltage rating substantially lower than that of the first transformer and a short circuit current rating substantially higher than that of the first transformer, and means for connecting the secondary windings of the two transformers simultaneously and in series to the cable so that, initially, the sum of the two secondary voltages is applied to the cable to break down the fault, and that, as the fault resistance reaches a value which permits the flow of a current higher than that of the short circuit current rating of the first transformer, the first transformer will zero and leave only the second transformer to reduce the fault resistance to a value suitable for fault location purposes.
Claim 2
Dependent Claim
152 words
Apparatus for reducing the resistance of a high resistance fault in an electrical cable, comprising a first transformer having a predetermined open circuit voltage rating and short circuit current rating, a second transformer having an open circuit voltage rating substantially lower than that of the first transformer and a short circuit current rating substantially higher than that of the first transformer, and means for connecting the secondary windings of the two transformers simultaneously and in series to the cable so that, initially, the sum of the two secondary voltages is applied to the cable to break down the fault, and that, as the fault resistance reaches a value which permits the flow of a current higher than that of the short circuit current rating of the first transformer, the first transformer will zero and leave only the second transformer to reduce the fault resistance to a value suitable for fault location purposes.
Claim 3
Dependent Claim
24 words
Apparatus as claimed in claim 1 including means to rectify the secondary voltages of the two transformers before they are applied to the cable.