Harmonic Distortion Compensation in Voltage Transformers for Improved Power Quality Measurements

Monitoring voltage harmonics represents one of the most important tasks in power quality assessment. In particular, the employed instrument transformer plays a key role in the achieved accuracy. Its harmonic measurement performance is typically evaluated by measuring its frequency response function. However, nonlinearities may have a nonnegligible impact on measurement uncertainty; for example, this occurs as far as the inductive voltage transformers are considered. This paper proposes a simple technique allowing the compensation of the most significant nonlinear effect that is the harmonic distortion produced by the large fundamental primary voltage. The method is first derived and introduced by means of numerical simulations and then implemented through a proper experimental setup. Results highlight remarkable accuracy improvements when realistic voltage waveforms are measured.