Non-Destructive Status Testing of Lead-Sheathed, 5-KV Undergound Cable

We report the successful conclusion to phase one of a program to solve the problem of determining in unambiguous but non-destructive fashion the on/off status of a lead-sheathed underground distribution cable. An automatic, remote-controlled prototype machine has been developed with self-test and monitoring functions. The machine cuts a small hole through the lead jacket, applies a detector probe to the cable's outer, high-resistivity screen. This screen is capacitively coupled to the inner conductor so the small voltage drop caused by the displacement current to the screen can be used to determine the on-off status of the cable. If the cable tests off, at the operator's direction the machine spikes the cable to provide absolute proof of the off status of the cable.