Patent ID: 7372246

Claim:
A system for determining the phase of an alternating current having a periodic waveform and carried by a field conductor relative to an alternating current having a periodic waveform and carried by a reference conductor, comprising: a reference unit that samples a reference conductor voltage at a plurality of temporally spaced intervals, digitizes the plurality of voltage samples, and transmits the plurality of digitized reference conductor voltage samples; a field sampling unit that, when placed on or directly adjacent the field conductor at a field location, transmits a signal representative of a field conductor voltage, wherein the field sampling unit comprises a first conductive sensor element proximate a first end of the field sampling unit for sensing one or more voltages from one or more nearby conductors, the first conductive sensor element comprising a cylinder and a first output, a second conductive sensor element proximate a distal end of the field sampling unit for sensing one or more voltages from one or more nearby conductors, the second conductive sensor element comprising a cylinder and a second output and having at least one closed end with a generally planar face, where the closed end of the second conductive sensor element acts as a capacitive pickup when placed on or proximate to and generally parallel to the field conductor; and an electronic circuit for measuring the difference between the first output and the second output, and wherein the voltages of the one or more nearby conductors other than the field conductor are sensed approximately equally by the first and second conductive sensor elements and the differential measurement is representative of the voltage of the field conductor; and a field unit that receives the voltage signal from the field sampling unit, samples the field conductor voltage at a plurality of temporally spaced intervals and digitizes the plurality of voltage samples, receives the plurality of digitized reference conductor voltage samples, and compares the plurality of digitized field conductor voltage samples and the plurality of digitized reference conductor voltage samples to determine the phase of the alternating current carried by the field conductor relative to the alternating current carried by the reference conductor.