Evaluation of Supraharmonic Propagation in LV Networks Based on the Impedance Changes Created by Household Devices

This paper investigates the characteristics of emission in the frequency range 2-150 kHz (supraharmonics) in time and frequency domain and how it propagates under different scenarios posed by the customer connections and changes in the grid. The analysis is based on measurements performed in a low-voltage installation, considering the simultaneous operation of a set of PV inverters and LED lamps in order to create changes in both impedance and emissions. The results confirm that supraharmonics tend to interact with nearby devices in the customer installation. As the number and constellation of emitting devices change so does the propagation of the supraharmonics. The propagation towards the grid can either increase or decrease with the increasing number of connected devices depending on the ratio between the impedances of the device and the grid impedance. Devices' technology plays an important role in defining supraharmonic characteristics, emission levels and propagation. Finally, a qualitative analysis of the individual devices' impedance and discussion of some of the practical aspects is provided.