Underground Intelligence Bureau

In some cases, where the street light is supplied directly from the LV main, using the technique in the previous section may also allow the detection of the LV main which supplies that street light — and possible detection of LV service connections.

Another technique for locating LV services is the capacitance method. The red Genny lead is placed close to and parallel with a satellite cable or TV aerial cable, the black lead to earth (a changing tone will not occur using this technique). The Genny signal is induced into the cable and therefore detectable on the LV supply.

The same capacitance method can also be used to locate communications cables on BT poles and at properties where access allows.

The figures

9 from the printed chapter

Fig 01External wall lantern with a red crocodile clip on its supply — using the lighting circuit at a property.

Fig 02Genny connected at a property's service position, seen from above.

Fig 03Earth pin and lead at the base of a stone wall, water bottle beside for wetting the earth.

Fig 04Connection made inside an external meter box with the Genny beside it.

Fig 05Red clip on an outside tap — using bonded metalwork as the connection point.

Fig 06Genny at the corner of a house, meter box and downpipes on the wall above.

Fig 07Red clip on a cable running down a rendered wall beside an old iron pipe.

Fig 08Genny4 connected beneath a white external unit on a brick wall.

Fig 09Wooden pole with the supply dropping to a service position at its base.

Filed under

Direct connection Locating technique

Locating Low Voltage (LV) Mains and Services

The figures