## 4 Results of an Experimental Study with Power-Line Communication and Selected End-User Equipment
Statistics of the connection in the presented case are expressed by:  
* Total number of the connections: 106 (including 86 successful and 20 failed connections). * Duration of failed connections in one hour: 371 s.  
Comparative Analysis: Operation of the Tested PRIME PLC System under the Different Scenario of Supply Voltage Distortion and Variant Types of Loads  
Previously presented results described in detail cases with LED light sources and consequently increased level of supply voltage distortion. The presented results aimed to express the methodology of the investigation with special consideration of the identification and analysis of the characteristic spectra of voltage in the point of the connection of the load and energy meter. As already mentioned, the loads responsible for the majority of data transmission interference in systems based on PLC transmission are LED and CFL light sources and induction motors powered by a pulse width modulation (PWM) frequency inverter. Therefore, in order to assess the impact of the power supply voltage distortion on the operation of the tested PRIME PLC system, with the simultaneous presence of emissions of these loads, extended investigations were performed using several cases formulated as mixtures of the different scenario of supply voltage distortion and variant types of load. It resulted in ten investigation cases for deliberate comparative analysis:  
* No-load and sinusoidal supply voltage (reference condition)--1 case. * LED light sources (sinusoidal, EN 50160, IEC 61000 4-13)--3 cases. * CFL light sources (sinusoidal, EN 50160, IEC 61000 4-13)--3 cases. * Induction motor powered by PWM (sinusoidal, EN 50160, IEC 61000 4-13)--3 cases. Spectral analysis in the range of 2-150 kHz was carried out for the mentioned ten investigation cases. Figure 11 presents spectra of the investigated voltage in the point of the connection of the load and energy meter with PRIME PLC communication for: (a) LED, (b) CFL, and (c) induction motor with PWM converter, respectively. For better representation, every figure consists of margin characteristic spectra reflecting the background of the transmission obtained for the sinusoidal supply and no-load denoted as reference condition (grey) as well as spectrum of the signal with PRIME PLC transmission (black). The next three curves express the investigated voltage spectra for the consequently deteriorating supply voltage condition (brown--sinusoidal, yellow--EN 50160, orange--IEC 61000-4-13). The first comment to the obtained results presented in Figure 11 might be addressed to the comparison of the non-intentional emission of the investigated loads for the sinusoidal supply voltage (brown) and normative curves representing emission in a power grid. It can be noticed that, for normative supply conditions, the spectra differ significantly and are characterised by different frequency components in the observed range 2-150 kHz. Moreover, temporarily the obtained spectra exceed the curves representing the normative level of non-intentional emission in the public grid defined in IEC 61000-3-8 [4] adopted in EN 50065:2012 [2] (green normative curve). The second comment might be addressed to the influence of the distorted voltage condition on non-intentional emission in the range 2-150 kHz. As it was shown in Figure 11, increasing the level of the contribution of the low-frequency component 0-2 kHz in the supply voltage affected the non-intentional emission in the observed range 2-150 kHz in the connection point of the loads and energy meter with PRIME PLC transmission (yellow and orange lines). For the margin condition representing low-frequency contribution used in the immunity test, according to IEC 61000-4-13, the investigated spectra were very close to the intentional transmission signal of the PRIME PLC system (black).