Implementation of quadrature based RMS calculation on real-time power monitoring systems

Accurate power system monitoring plays a vital role in detection of supply problems within the supply grid. Of all parameters being monitored, rms based measurements are used to detect various voltage based events within the system. IEEE and IEC based standards utilize full cycle instantaneous samples repeated every half a cycle for the calculation of rms. These measurements are not without limitations especially for short duration variations. This paper proposes 4-instantaneous sample points sampled at 90 degrees apart (quadrature based rms) to estimate rms and further detect voltage events in real-time. The proposed method is experimentally tested and applied for voltage events monitoring using Labview FPGA CompactRio platform. The results demonstrate the effectiveness of the proposed method for estimating the signal rms value with less number of samples.