A Noncontact Voltage Measurement System for Power-Line Voltage Waveforms

This paper presents the design and implementation details of a complete noncontact (NC) voltage acquisition system, which allows the measurement of power-line voltage waveforms without galvanic contact. The system is composed by a novel capacitive probe, an analog front end (AFE), and a microcontroller-based digital signal processing stage. A deep experimental characterization of the noncontact measurement system was performed. The tests reported a high linearity (maximum nonlinearity of +/- 0.2%), a low input-referred noise (11 mV(rms)), and a low-frequency response distortion. Measurements of +/- 330-V triangular waveform signals were performed with maximum instantaneous errors below +/- 1.5 V. The power-line voltage (220 V-rms at 50 Hz) was acquired without galvanic contact with an instantaneous error lower than +/- 3 V, whereas the mean error on rms voltage measurements was 0.32% and the maximum 0.7%. A two-day continuous measurement of power-line voltage was accomplished for testing system's stability, resulting in negligible accuracy variations.