Abstract: An apparatus is disclosed to locate buried conductors, specifically a substation grounding grid. The apparatus provides accurate and precise location of a conductor as it is passed across the ground surface. A power unit is provided that includes a signal generator to produce a periodic test current, asymmetric in time, that has at least one odd harmonic and one even harmonic of a fundamental frequency. The periodic test current is passed through the buried conductors. A portable search unit has a substantially vertical axis coil attuned to pick up a signal including the odd harmonic and the even harmonic of the fundamental frequency from the periodic test current, a power source is provided and a signal interpretation processor and indicator provides an indication of phase reversal of the signal utilizing the odd harmonic and the even harmonic when the vertical axis coil passes over at least one of the buried conductors.