# Multi-Point Time-Synchronized Waveform Recording for the Analysis of Wide-Area Harmonic Propagation
## 4 Results
### Separate Operation of the EV Charger  
The analysis begins by examining EV charger current emission and by assessing respective voltage distortion under sinusoidal power supply conditions. Figure 2 shows that current spectral components \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Test Sequence** & **Power Supply** & **PV Setpoint** & **EV Charger** & **Triphase** & **Load Banks** & **Topology** \\ \hline A.1 & MG & 7.5 A & Disconnected & Disconnected & Disconnected & A \\ A.2 & MG & Disconnected & 32 A & Disconnected & Disconnected & A \\ A.3 & MG & Disconnected & Disconnected & Substation A & Disconnected & A \\ A.4 & MG & 7.5 A & 32 A & Substation A & Disconnected & A \\ B.1 & Grid & 7.5 A & Disconnected & Disconnected & Disconnected & A \\ B.2 & Grid & Disconnected & 32 A & Disconnected & Disconnected & A \\ B.3 & Grid & Disconnected & Disconnected & Substation A & Disconnected & A \\ B.4 & Grid & 7.5 A & 32 A & Substation A & Disconnected & A \\ B.5 & Grid & 7.5 A & 32 A & Substation A & 24 kW & A \\ B.6 & Grid & 7.5 A & 32 A & Substation A & 24 kW & B \\ B.7 & Grid & 7.5 A & 32 A & Substation D & 24 kW & B \\ \hline \hline \end{tabular}  
Topology A—mock impedances MI 4 and MI 5; topology B—mock impedance MI 8.  
\end{table} 
Table 1: Experimental scenarios. of the EV charger for this case are characterized by high values of harmonics at 1150 Hz and 1250 Hz, which are 0.71 A and 1.24 A, respectively. Moreover, 150 Hz and 250 Hz spectral components exhibit 0.35 A while a 350 Hz harmonic component counts some 0.42 A. Finally, lesser levels can be observed for frequencies between 450 Hz and 1050 Hz. By analyzing synchronized voltage spectral components presented in Figure 2, one can notice a coherent picture, where at 1150 Hz and at 1250 Hz harmonic magnitudes are 1.90 V and 2.80 V, respectively. For the rest, only harmonics at 250 Hz, 350 Hz, and 650 Hz are clearly visible with RMS magnitudes of 0.67 V, 1.22 V, and 0.65 V, respectively. On the other hand, by energizing test networks by means of a public grid, a clear change of the harmonic profiles can be observed in Figure 3. An increase of 350 Hz and 550 Hz current components up to 0.51 A and 0.246 A, respectively, coincided with the rise of voltage at 350 Hz up to 1.64 V and substantial decrease of 650 Hz voltage harmonic which counted 0.284 V.  
Figure 3: EV charger harmonic currents and voltages at LV side of Substation A. Test sequence B.2—public grid supply. Figure 2: EV charger harmonic currents and voltages on the LV side of Substation A. Test sequence A.2—MG set supply. Thus, a direct comparison of Figures 2, 4, and 5 allows for inferring that voltage distortion recorded at different points could not be caused by the EV charger itself but rather propagated from the path magnetizing circuit-MV side Substation G-MV side Substation A. This conclusion can be supported by measuring synchronized spectra of magnetizing current produced by pole-mounted transformers versus spectra of the MV current through Substation A. This graph is shown in Figure 6. Based on this graph, it can be inferred that harmonic components of magnetizing current had a dominant influence on the voltage distortion in the system. Therefore, this current impacted MV voltage at Substation G and propagated down to its LV side, where reflected MV distortion patterns are clearly visible. Additionally, the synchronized data allow for drawing interesting conclusions with respect to Substation A. At frequencies 1150 Hz and 1250 Hz, we can notice that voltages at LV side are substantially higher in comparison with ones at Substation G. This is not only related to a larger system harmonic impedance with underground cable MI 1 being 5 times longer than MV cable connecting Substation G (in total 400 m), but also to a fact that, at these frequencies, an EV charger's emissions were relatively high, which resulted in larger harmonic voltage drop over impedance at these frequencies (as Figure 6 supports). Figure 5: Harmonic emission of EV charger under ideal sinusoidal supply conditions.