Apparatus and method for identifying the phase of a three phase power

Abstract

A phase identification system and method identifies the phase of a power signal at a remote location from a three-phase generator. The system has a radio transmitter which transmits a modulated representation of a voltage signal via radio frequency, and a remote field detector which receives and demodulates the transmitted signal to provide a reference signal. The field detector also includes an input probe for detecting the power signal having an unknown phase at the remote location. The field detector includes a phase comparator and a calibration phase corrector for determining the phase difference between the power signal having a known phase and the power signal having an unknown phase, thereby identifying the phase of the unknown signal at the remote location. The invention also includes a method of calibrating the phase identification system. The method includes the steps of modulating and transmitting a known phase signal, receiving and demodulating the same signal, and comparing the demodulated signal with a signal having the same phase as the known signal to determine the phase difference due to the transmitting and receiving circuitry. This phase difference constitutes the calibration offset value which is subtracted from the measured phase difference between the reference signal and the detected unknown signal to obtain a corrected phase difference value.