Effectives

The effective values in the measurement data are determined as a true root mean square (True RMS). This method also takes into account non-sinusoidal signal components, such as those caused by harmonics or non-linear loads.

The calculation is performed continuously on the basis of the measured instantaneous values. The voltage and current signals are recorded at a fixed sampling rate. The effective value is calculated from the instantaneous values using a sliding time window. The number of grid half-waves taken into account can be set via the parameter EffectiveWindowCycles. This time window is shifted continuously so that an updated value is available in each cycle.

The time window is based on the period value of the grid frequency. The modules use a phase-locked loop (PLL) to determine this frequency. The PLL synchronizes to the measured voltage as a reference signal. The current grid frequency and thus the period value is determined from the phase angle. This serves as the integration period for the effective value calculation. The dynamic adaptation of the time window to the current grid frequency ensures that the calculation is always carried out over whole multiples of periods. This means that the effective value determination remains robust even with frequency fluctuations.

This method is used for the effective values of voltages and currents in the structures Voltage, Current and for the power values (active, reactive and apparent power) in the structure Power. In contrast, the fundamental components of voltage, current and power in the structure Fundamentals are determined exclusively from the sinusoidal signal components of the fundamental frequency.

The measured values are provided via the STcPowerMeasureEffective structure.