• Isolating the cable from the feed provides an added measure of safety, eliminating the chances of accidental electrical contact while working on the circuit.

• Isolating the faulted section of underground cable from the rest of the circuit assures that the signal from the underground cable fault locating equipment is directed only at the fault, not bleeding off into branch circuits or devices still connected to the circuit.

Steve (right) looks on as crews isolate from the transformer

and prepare to connect the Timco Spitfire

•      Circuit isolation can be hampered by branch circuits, T-Taps, and wye splices, especially on street light circuits. In these cases it may become necessary to locate the underground splices and cut the circuits apart. In situations where the service or street light cable is spliced directly on to the mains it is advisable to locate the splice and cut the faulted section away from the main. When doing this, cut the faulted circuit far enough away from the splice in order to restore service with a straight splice instead of having to remake the wye splice. this will save considerable time and permits the rest of the circuit to remain in service.

•      Circuits that are fed from direct overhead taps will need to cut, either in the pole riser or in the ground, to achieve isolation. Street light circuits that are controlled by photocells or relays do not need to be isolated, the photocell or relay switch automatically isolates the circuit from the feed.

•      Individual street lights or other devices should be disconnected from the circuit, either by opening the fuseholder or physically disconnecting the device.

•      Other circuits, such as parking lot lights, signs, etc can usually be isolated at junction boxes, pole bases, or within the device itself.

     If you are having difficulty detecting the signal from the underground cable fault locating equipment, the problem could be insufficient isolation

next - FAULT LOCATING