Str. 108 Rynek Energii Nr 1(116) - 2015 LV NETWORK MODELLING FOR SMART LIGHTING CONTROL SYSTEMS OVER PLC Piotr Kiedrowski Key words: PLC, Smart Lighting, signal attenuation, LV network impedance Summary. The model of the narrowband PLC signal attenuation is presented. The sources of the attenuations are LV power lines as well as loads impedance. The proposed method of modelling is limited to the specific kind of the LV network which are street or road lights supplying lines. The model takes into account: the variability in the lantern impedance, the back impedance which is the transformer and other parallel lines impedance and of course the primary parameters of the supplying lines. The model bases on the long transmission lines theory as well as transmission line equations and allows us to determine the energy absorption of the PLC signal by the individual lantern in any lighting state it can be. Knowing the internal impedance of the PLC modem the level of the receiving signal can be assessed and expressed in volts, amperes or (VA). This model allows to create simulators of the narrowband PLC transmission over cable or overhead lines which supply any type of lanterns, that can be individually dimmed from the Smart Lighting Control System. The simulation of the street or road lighting last-mile communication systems allows us to obtain essential information about its traffic possibilities and performance, what is widespread used both at the stage of the planning as well as at the stage of the maintenance. 1. INTRODUCTION The low voltage (LV) network, used for streets and roads lighting supplying, creates a specific kind of the transmission medium for Smart Lighting control systems. These systems usually use the power line communication (PLC) technology. From the topological point of view such solutions are similar to bus networks. There are of course more differences then similarities in compare to classical wired communication network. The main differences are:  the impedance mismatch,  unbalance of the lines,  changeable mains impedance,  lines are usually not transparent, by the meaning of their attenuation,  skin effect is more pronounced,  negligible small conductance between conductors. These reasons cause, that classical approach to the problem of the network modelling is impossible. There are also no possible to adopt methods used in [12] for describing electric power distribution network, because they only concern low frequencies. Proposed method is dedicated to the narrowband PLC, i.e. working in the frequency band up to 150 kHz [6]. Over the last decades, the narrowband transmission over metal lines was not developed [1] except the PLC and ADSL (Asymmetric Digital Subscriber Line) technologies. Excluding the last-mile [10] communication systems for Smart Grid, even narrowband communications were realized on the basis of the broadband transmission systems [5], [9]. There are a few works which describe the methods of comparing the different standards and transmission modes of the narrowband PLC [1], [3], [4], [8]. These works focused mainly on qualitative description of the transmission vs. SNR (Signal to Noise Ratio) proposing the noise models. In this paper the attenuation model is proposed. Knowing the power of the transmitting signal, the attenuation of the transmitting path and assuming the highest, allowable noise level there is possible to assess the performance of the communication system, by the meaning of the SNR worst case. Knowing the quality parameters for the worst conditions is very useful in the system designing e.g. the communication protocols type, their parameters, the modulations type selection, transmission speed or even time of the reaction. The proposed model bases on primary parameters evaluation of the LV power lines, which are necessary for calculating the secondary parameters, such as: the characteristic impedance and the propagation constant. These two parameters together with the lanterns, modems and the transformer impedances allow to determine the value of the received signal power. To determine the secondary parameters, the transmission lines theory was used, as more adequate method than the four-pole theory due to the distributed character of the primary parameters. Proposed method of modeling is limited to LV network used for streets and roads lighting supplying because it does not include any extra loads influences, except the lanterns and MV/LV transformer ones.