As harmonic distortion of voltage and current is reality in the power system, the need for accurate measurement of electrical power and energy goes beyond the instruments’ specifications and calibration procedures regarding pure sine wave signals. Several international standards and recommendations provide test signals for examination of electricity meters under non-sinusoidal conditions, however, not all of the test signal parameters’ possible states are faithfully represented in those documents. Because the high order harmonics may possess random amplitudes and phase shifts in relation to components at fundamental frequency, it is important that the meter’s performance is verified with random waveforms as well. The non-linear dependence between the measured power/energy and the phase shifts, both between fundamental and harmonic components, provides additional complexity of such an analysis. Simple test signals, which are in accordance with the standards’ demands and propositions, are used for determination of the measurement error in case of different harmonic distortion parameter change. In order for a general error function for any measurement device to be determined, mathematical modelling, regarding the results from multiple tests, is performed. The mathematical model presents a strong dependence between a single component’s phase shifts and a meter’s error and it provides a systematization of all signal parameters’ influence on the measurement accuracy.

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The main metrological ambiguity in transducers' calibration protocols establishment is whether the unit is going to be regarded as an integrated device in a measurement system, or it will be examined as a standalone instrument. This dilemma is related to the quantity selection on which the procedure development is based and later the measurement uncertainty modelling is performed. Another issue is the appropriate selection of measurement points which are going to embrace the full range of input signals transformation. The discussion is experimentally verified with a real case study considering trans-conductance amplifier calibration by using high current energy comparator.

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