Mapping a buried electrical earthing network for dispersion of lightning or electrical fault currents, injects voltage signals measures simultaneously the induced electric and magnetic fields in two different planes

摘要

An a.c. voltage signal is injected between two injection points (16) and at a particular zone the electromagnetic field is detected. The values of the magnetic field (H) and the electric field (E) are measured in the zone and these values are compared with respective predetermined step values. When the magnetic field value (H) is greater than its associated step value it is determined that there is a network conductor in the zone between the two injection points or the earthing conductor is connected to one of the injection points (16) when the electric field (E) is greater than its associated value. Signals are injected several times with silent gaps between successive signals. Independent claims are included for a signal injector and electric and magnetic field sensors.