| 摘要 |
<p>A system is disclosed in which an electrically conductive boring device (12) is caused to move through the ground to provide an underground tunnel, to install underground utilities, or for any other reason. An arrangement for detecting if the boring device (12) electrically engages an underground source of high voltage such as an existing underground utility line is provided, the arrangement comprising means (22) defining an electrically conductive path leading from the boring device (12) to a grounding point (20) sufficient to reduce to a negligible level any high voltage to which the device (12) may be subjected. The arrangement monitors the current through the grounding path (22) and indicates if the current level through the path (22) reaches a predetermined threshold level which is selected to correspond with the presence of high voltage.</p> |
