## 5 Discussion  
Taking into account the results of the research presented in this paper, it can be stated that the harmonic content of the supply voltage can be considered as one of the origins of the increasing level of supraharmonics non-intentional emission. As it was shown in the paper, successively increased deterioration grade of the supply voltage waveform, representing respectively harmonic content of permissible level defined for the public grid as well as for the immunity test, had a direct influence on non-intentional emission in the range 2-150 kHz, that in consequence affected the transmission of the investigated PRIME PLC system. Figure 13: Impact of the supply voltage distortion grade on the duration of the failed connections in one hour of the investigated PRIME PLC system. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sinusoidal Supply Voltage** & **LED** & **CFL** & \begin{tabular}{c} **Induction Motor** \\ **with PWM** \\ \end{tabular} \\ \hline total number of & & & \\ attempted connections & 53 & 95 & 110 \\ number of successful connections & 44 & 76 & 90 \\ number of failed connections & 9 & 19 & 20 \\ duration of failed connections in one & 2 & 186 & 186 \\ hour (s) & & & \\ \hline Distorted supply voltage & & & \\ EN 50160 (Table 2) & LED & CFL & \
\begin{tabular}{c} Induction motor with \\ PWM \\ \end{tabular} \\ \hline total number of connections & 103 & 54 & 93 \\ number of successful connections & 83 & 44 & 83 \\ number of failed connections & 20 & 10 & 10 \\ duration of failed connections in one & 187 & 187 & 551 \\ hour (s) & & & \\ \hline Distorted supply voltage & & & \\ IEC 61000-4-13 Class 3 (Table 3) & LED & CFL &
\begin{tabular}{c} Induction motor with \\ PWM \\ \end{tabular} \\ \hline total number of connections & 106 & 104 & 28 \\ number of successful connections & 80 & 84 & 24 \\ number of failed connections & 20 & 20 & 4 \\ duration of failed connections in one & 371 & 366 & 192 \\ hour (s) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The statistics of the transmission of the investigated PRIME PLC during the different scenarios of supply voltage distortion and variant types of loads (2 h continuous work). The obtained results allow us to draw several conclusions, namely:
* For all investigated loads (CFL, LED, the motor with PWM) it was observed that increasing the content of higher harmonics in the supply voltage from the sinusoidal condition, by the waveform distortion representing permissible content of harmonic in a public grid, to the waveform distortion defined in the immunity test of the equipment, resulted in a higher level of non-intentional emission in the range 2-150 kHz. As a consequence, the SNR derived from the local maximum magnitude of the background signal and associated with it the local magnitude of the transmission signal of the investigated PRIME PLC system was consistently decreasing, from 17.04 dB to 3.14 dB (for LED), from 20.61 dB to 2.94 dB (for CFL) and from 10.11 dB to \(-\)0.79 dB (for the motor with PWM). The SNR calculated on the basis of power of the transmission signal and power of the background signal in the transmission band was also decreasing, from 30.06 dB to 7.61 dB (for LED), from 26.31 dB to 9.73 dB (for CFL), and from 18.97 dB to 2.49 dB (for the motor with PWM), respectively. * An indirect result of the supply voltage distortion is an increasing number of the connections activated by the investigated PLC system in order to prevent loss of the connection. However, in case of a high level of supply voltage distortions, the duration of the failed connections increased significantly. The duration of failed connections decreased from 2 s to 371 s for the LED load, and from 186 s to 366 s for the CFL load. The highest value of the duration of failed connections, 551 s, was achieved in the case of the induction motor powered by PWM.