| 摘要 |
System for electrical signalling between first and second downhole locations in a well containing a metallic structure 1. Units 3 / 4 at first and second locations apply signals to and/or receive signals from the metallic structure. A third location between the first and second locations has a magnetic toroid 51 around metallic tubing 1 of the metallic structure. The magnetic toroid has a winding 52 which is connected to a cable 53 which runs along the metallic tubing. The first unit applies a signal to and/or receives a signal from the metallic tubing via the cable and magnetic toroid allowing signalling between the first and second units. The cable may bridge an electrically insulated part of the metallic structure. A further independent claim defines passive relay apparatus comprising first and second magnetic toroids (see FIG 2) with windings and a cable connected between the windings of the toroids. |
