2nd URSI AT-RASC, Gran Canaria, 28 May – 1 June 2018 Method for measuring background noise levels conducted over low voltage power lines Leszek Nowosielski (1) , Bogdan Uljasz (1) , Marian Wnuk (1) , Michał Nowosielski (2) (1) Military University of Technology, Faculty of Electronics, Warsaw, Poland (2) Medical University of Warsaw, Poland Abstract This paper describes a measurement methodology for background noise conducted over low voltage power lines in the 0.15 MHz – 30 MHz frequency range. A block diagram of a background noise voltage measuring system with supporting components is provided, along with a description of the measurement methodology used. Example measurement results are presented. The paper also describes relationships, which can be used for assessing environment disruption levels on a given power line. 1. Introduction Data transmission technologies utilizing low voltage power lines to transmit information within buildings are continuously rising in popularity. These data transmission systems are referred to as Power Line Communications (PLC) solutions. Low voltage circuits are convenient data transmission pathways for indoor premises within a building. To make use of these circuits, one needs to install dedicated powerline modems, which need to be plugged directly into a electrical wall socket. Energy suppliers use power lines for a similar purpose, i.e. to collect metering information from compatible energy meters. Therefore, background noise levels on low voltage power lines are an important concern to anyone deploying Power Line Communications technologies. Measurements of background noise levels conducted over voltage power lines within frequency ranges up to 500 kHz can be found in available literature [2, 3, 4, 5]. To assess whether a given power line circuit is able to support PLC with broadband speeds (up to several Mbit/s), information on background noise levels in a wider frequency range, up to 30 MHz, is required. However, information provided in current literature [1] on background noise measurement in that frequency range is outdated. The last paper on this subject was published in 1999, and focuses solely on urban areas. This article describes a method for measuring background noise levels conducted over low voltage power lines, and an example schematic of the measurement system. Levels of conducted background noise depend on natural (thermal) noise and any interference generated either intentionally or intentionally by people. There are few quantitative descriptions of conducted background noise in available literature. As presented in available literature [1], one can state that background noise levels conducted via low voltage power lines, as measured in 1999 for a single location within the territory of the United States, subjected to representative disturbances from electrical and electronic devices in frequency ranges of (1÷20) MHz and (20÷60) MHz equal 40 dB and 30 dB respectively above the thermal noise levels defined by the following relationship:  ௧௘௥,௕ =൉ ଴ ൉ (1) where: k – Boltzmann constant, equal to 1.38 ∙ 10 ଶଷ J/K, T0 – temperature of 290 K, b – equivalent bandwidth of a reference selective system in [Hz]. Upon conversion to logarithmic units and substituting fixed values, such as the Boltzmann constant, and the ambient temperature T0=290 K, the relationship (1) becomes easier to use.  ௧௘௥,௕ [ܤ] = െ174 + 10 log  (2) See Fig. 1 for example values of thermal noise levels Pter,b and conducted background noise levels Pn,b as published in existing literature [1]. Figure 1. Example values of thermal noise levels Pter,b and conducted background noise levels Pn,b for a frequency range of 150 kHz – 30 MHz, as presented in existing literature [1] In many application, it would more convenient to use the value of conducted background noise voltage Un,b in the b band defined by the pre-detection circuit of a monitoring receiver connected to the monitored low voltage power line. To convert the conducted background noise levels