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Inductive instrument transformers (ITs) are still the most used voltage and current sensors in power systems. Among the numerous applications that require their use, one of the most important is surely represented by harmonics measurement. In this case, the recent literature shows that, since they suffer from both a filtering behavior due to their dynamics and from nonlinear effects produced by their iron core, they can introduce errors up to some percent. This article wants to deeply investigate, in the very same experimental conditions, about the performance of two digital signal processing techniques, recently introduced for the improvement of harmonics measurements performed through ITs, namely, SINusoidal characterization for DIstortion COMPensation (SINDICOMP) and compensation of harmonic distortion through polynomial modeling in the frequency domain (PHD). These methods have been applied to two different voltage transformers, having different specifications, by using two measurement setups based on different architectures. The impact of the voltage generator employed during the identification on the achieved accuracy is theoretically and experimentally evaluated. Modified versions of SINDICOMP and PHD compensation, which are more robust against nonidealities of the measurement setup, are presented. The performances of the techniques are evaluated by adopting voltage waveforms similar to those that can be encountered during the normal operation in a real distribution grid.

A standardized measurement procedure and source specification for laboratory high-frequency (HF, 2–150 kHz) emissions tests of low-voltage (LV) electronic equipment are still in development. To date, emissions have been measured by direct supply from the mains network or a controllable power source (PS), but both methods are known to interfere with the assessment process. A line impedance stabilization network (LISN) limits supply-load interactions but has been underevaluated until now in the HF analysis, despite being named a potential approach in IEC Standards. This article quantifies the effect of supply conditions on HF emission assessment and the role of the LISN. The effect of the supply voltage fundamental amplitude and low-frequency background distortion on the magnitude and frequency of the characteristic HF emissions is presented, and a new supply configuration combining a programmable PS with LISN is proposed. Experimental results from a case study of two LED lamps with distinct HF emissions, representative of a number of typical LV electronic devices, indicate that only the proposed programmable PS+LISN supply can guarantee the accurate and repeatable measurements under controllable voltage supply conditions and impedance separation that are needed by ongoing HF standardization and modeling activities.