This paper presents a comparison of measurement methods for current and voltage distortion in low voltage networks in the frequency range from 2 kHz to 150 kHz (supraharmonics). The comparison encompasses the methods informatively described in IEC and CISPR international standards, as well as other innovative techniques presented in the literature. The presented work is carried out within a novel framework that includes advanced and complex synthetic test signals, as well as real grid recordings, that allow an accurate comparison of the performance of the tested methods. Specifically designed indices are employed to characterize the accuracy of the tested methods in the frequency and amplitude assessment. In light of that, strengths and weaknesses of the methods are identified. The results of this paper contribute to the ongoing standardization work carried out by the IEC SC77A/WG9 with the purpose of defining a normative measurement method suitable for assessing grid disturbance levels in the range from 2 kHz to 150 kHz.

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This work presents a novel measurement method to characterize long-term and short-term variations of the LV grid impedance from 20 kHz to 10 MHz with configurable time, frequency and amplitude resolutions. The characterization of the grid access impedance in this frequency range is vital for the design and development of NB-PLC and BB-PLC technologies. The measurement system is valid for in-home, indoor cable networks and for the harsh conditions of the LV distribution grid, where a large input dynamic range and strong protection mechanisms against high-amplitude impulsive noises are required. Its accuracy is evaluated by comparison to a precision impedance meter for a wide set of impedance values, obtaining a maximum deviation within ± 8 %.First trials of the grid impedance sub-cycle variations caused by commercial appliances and for frequencies assigned to BB-PLC are also presented in this paper. The results demonstrate that the grid impedance is highly time-varying within the mains cycle, both in amplitude and phase. These first outcomes point at the need to evaluate the accumulative effects of sub-cycle variations in the LV distribution grid, so that equalization algorithms in the next BB-PLC technologies could be developed to overcome the impact of these fast variations.

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