By: Bas ten Have (University of Twente)

Conducted electromagnetic interference has shown to result in misreadings of static energy meters due to non-linear current waveforms [1]-[3]. Based on these findings it is of interest to survey waveforms that occur in typical low voltage distribution networks, and to see which waveforms static energy meters are exposed to in real world situations. Therefore, on-site surveys are performed in the framework of the MeterEMI project, and this article summarizes the performed surveys.

The waveforms occurring at the meter connection point of a consumer are measured using a time-domain approach, and a Time-domain Electromagnetic interference Measurement and Post-processing System (TEMPS) is used [4]. Such system has several advantages: it allows to reduce effective measurement time, perform full-spectrum measurement, parallelize acquisitions through multi-channel capabilities, and moreover other advanced processing functions are possible, because time-domain data is available. A basic block diagram of TEMPS is shown in Figure 1.

Figure 1: Diagram of TEMPS [4].

Current transducers are connected to the meter connection point to measure the line(s) and neutral currents in the system.  A picture of the installed measurement setup is shown in Figure 2. Specific triggers are used to select only the non-linear, impulsive, signals. For this purpose, the waveforms are triggered based on the amplitude probability distribution (APD) [4] and a wavelet trigger [5]. Test sites are surveyed during a 10 day period.

Figure 2: Installed measurement setup at the consumers meter connection point [6].

On-site measurement results at a location where different electric vehicles are charging are shown in [4]. In Figure 3, the time-domain waveform obtained in such a situation is plotted. From this result the impulsive behavior of the distribution network is visible, which shows a clear harmonic distorted current, where current spikes are visible on the top of the sinewave that is repeating at mains frequency.

Figure 3: Time domain data of an electric vehicle charging [4].

In another measurement campaign, a household situation using a photovoltaic installation, is surveyed, and the results are summarized in [6]. In this case most of the captured waveforms show a clear fundamental frequency, and have higher order components, or pulses, at the top of the sine wave, which is comparable to the previously mentioned results and is plotted in Figure 4. Furthermore, highly harmonic signals are found in which a higher third order harmonic, compared to the fundamental frequency is observed together with current transients with short rise times. This shows the existence of highly harmonic distorted currents in low voltage distribution networks.

Figure 4: Typical occurring distorted currents, as found in [6].

These surveys have shown the existence of harmonic distorted and pulsed currents in low-voltage distribution networks. Within the framework of the project more test sites are surveyed in different countries, the results are currently evaluated using different signal post-processing techniques, such that the complex signals can be characterized by a parametric description.

[1] B. Have, T. Hartman, N. Moonen, C. Keyer, and F. Leferink, “Faulty Readings of Static Energy Meters Caused by Conducted Electromagnetic Interference from a Water Pump,” Renewable Energy and Power Quality Journal (RE&PQJ), pp. 15-19, Santa Cruz de Tenerife, Spain, 2019. DOI: 10.24084/REPQI17.205

[2] B. Have, T. Hartman, N. Moonen, and F. Leferink, “Misreadings of Static Energy Meters due to Conducted EMI caused by Fast Changing Current,” 2019 Joint International Symposium on Electromagnetic Compatibility and Asia-Pacific International Symposium on Electromagnetic Compatibility, pp. 445-448, Sapporo, Japan, 2019. DOI: 10.23919/EMCTokyo.2019.8893903

[3] B. Have, T. Hartman, N. Moonen, and F. Leferink, “Inclination of Fast Changing Currents Effect the Readings of Static Energy Meters,” 2019 International Symposium on Electromagnetic Compatibility (EMC Europe 2019), pp. 208-213, Barcelona, Spain, 2019. DOI: 10.1109/EMCEurope.2019.8871982

[4] T. Hartman, M.Pous, M.A. Azpúrua, F. Silva, and F. Leferink, “On-site Waveform Characterization at Static Meters Loaded with Electrical Vehicle Chargers,” 2019 International Symposium on Electromagnetic Compatibility (EMC Europe 2019), pp. 191-196, Barcelona, Spain, 2019.  DOI: 10.1109/EMCEurope.2019.8871469

[5] F. Barakou, P.S. Wright, H.E. van den Brom, G.J.P. Kok, and G. Rietveld, “Detection Methods for Current Signals Causing Errors in Static Electricity Meters,” 2019 International Symposium on Electromagnetic Compatibility (EMC Europe 2019), pp. 273-278, Barcelona, Spain, 2019. DOI: 10.1109/EMCEurope.2019.8872120

[6] B. Have, M.A. Azpúrua, M. Pous, F. Silva, and F. Leferink, “On-Site Waveform Survey in LV Distribution Network using a Photovoltaic Installation,” 2020 International Symposium on Electromagnetic Compatibility (EMC Europe 2020), Rome, Italy, 2020. DOI: 10.1109/EMCEurope.2019.8871469