## 5 Conclusions  
This paper presents an evaluation of Broadband over Power Lines (BPL) technology, which benefits from the usage of already existing power lines as a communication channel. Over the years BPL has been considered as a promising technology in terms of future development of Smart Grids, and even in some cases it is the only available communication technology at the time; thus, knowledge of performance and its limitations is vital. In this paper, performance evaluation of Broadband over Power Lines technology with a focus on its use in linear topologies of distribution substations in modern Smart Grids was introduced. As we stated earlier in the state of the art section, the impact of repeaters on the network performance is still not exactly described, and thus planning of large-scale Smart Grid structures based on powerline communication technology lacks exact input values. The main focus of this paper is to investigate the impact of repeaters in a linear topology of distribution substations on the performance of the communication network. In the measurement section, both laboratory and field tests were presented based on a real on-field scenario with six substations with a total power line length of 1364 m, where the impact of BPL repeater for different testing methodologies was observed in detail. Results discussed in the measurements section later served as input values for simulations of powerline networks with balancing of data throughput with multiple streams and throughput bottlenecks. Besides the analysis of measured topologies, this research focused on simulations of the behavior of data transmission on the shared medium. In the first part, analysis of multiple streams on a simple point-to-point topology was studied. A total of 20 simulations were run. When the third stream joins the communication on the shared medium, its transmission speed rises and at the same time the transmission speed of the original streams slowly drops until they are equal. If there is a data stream  
Figure 20: Effects of repeaters on data throughput in a topology with a bottleneck. transmitting at a significantly lower speed, as it was in scenario 1B, this stream's speed is not affected in such scale. Further, the focus was on balancing time--how long it takes for two streams to reach the same throughput if one starts to transmit with delay. The effect of repeaters was also studied here. Discovered balancing times were in general much higher than the delay times, e.g., for the delay of 10 s in two repeater scenario with a bottleneck of 300 kb/s, the balancing time was almost 60 s. This means that the streams that start to transmit sooner have more priority than the ones that start later. In this simulation, bottlenecks affect the results in a way that with higher bottleneck values balancing time decreases. As our last investigation, the values taken from measurements were inserted into simulations to demonstrate the effect of repeaters and bottlenecks on the final throughput. According to the simulations, the throughput does not drop equally with different bottleneck values, lower bottleneck values mean lower throughput drop. This is most likely because of the fact that the limiting factor is not the repeater(s) but the bottleneck. A significant contribution of this article is our focus on the effect of repeaters in PLC communication. From previous studies and our measurements presented in this paper, it is clear that the repeaters have a great impact on data throughput mainly because the repeaters introduce data processing delay on the communication route. In future work, we want to evaluate the possibilities of extending the existing PLC simulation tool in NS-3 for repeater nodes. Another option is to survey the possibilities of MATLAB and Simulink. The evaluation of multiple different simulators could bring higher precision prediction of PLC network behavior. Conceptualization, P.M. ([PERSON]) and P.M. ([PERSON]); methodology, P.M. ([PERSON]), J.S. and J.P.; software, J.P.; validation, J.S.