The main subject of this paper is the sensing of network anomalies that span from harmless impedance changes at some network termination to more or less pronounced electrical faults, considering also cable degradation over time. In this paper, we present how to harvest information about such anomalies in distribution grids using high frequency signals spanning from few kHz to several MHz. Given the wide bandwidth considered, we rely on power line modems as network sensors. We firstly discuss the front-end architectures needed to perform the measurement and then introduce two algorithms to detect, classify and locate the different kinds of network anomalies listed above. Simulation results are finally presented. They validate the concept of sensing in smart grids using power line modems and show the efficiency of the proposed algorithms.

A major aspect in power line distribution networks is the constant monitoring of the network properties. With the advent of the smart grid concept, distributed monitoring has started complementing the information of the central stations. In this paper, power line communications modems deployed throughout the network provide a tool to monitor high-frequency components of the signals traveling through a power line network. We propose, therefore, to use them not only as communication devices but also as network sensors. Besides classical voltage measurements, these sensors can be designed to monitor highfrequency impedances, which provide useful information about the power line network, as for instance status of the topology, cable degradation, and occurrence of faults. In this paper, we provide a technical analysis of different voltage and impedance measurement techniques that can be integrated into power line modems. We assess the accuracy of the techniques under analysis in the presence of network noise, and we discuss the statistical characteristics of the measurement noise. We finally compare the performances of the examined techniques when applied to the fault detection problem in distribution networks, in order to establish which technique gives more accurate results.

Power distribution grids are exploited by power line communication (PLC) technology to convey high-frequency data signals. The natural conformation of such power line networks causes a relevant part of the high-frequency signals traveling through them to be radiated instead of being conducted. This causes not only electromagnetic interference with devices positioned next to power line cables, but also a consistent deterioration of the signal integrity. Since existing PLC channel models do not take into account losses due to radiation phenomenon, this paper responds to the need of developing accurate network simulators. A thorough analysis is herein presented about the conducted and radiated effects on the signal integrity, digging into differential mode to common mode signal conversion due to network imbalances. The outcome of this work allows each network element to be described by a mixed-mode transmission matrix. Furthermore, the classical per-unit-length equivalent circuit of transmission lines is extended to incorporate radiation resistances. The results of this paper lay the foundations for future developments of comprehensive power line network models that incorporate conducted and radiated phenomena.

Leakage of information in power line communication (PLC) networks is a threat to privacy and security. A way to enhance security is to encode the transmitted information with the use of a secret key. If the communication channel exhibits common characteristics at both ends and these are unknown to a potential eavesdropper, then it is possible to locally generate a common secret key at the two communication ends without the need for sharing it through the broadcast channel. This is known as physical layer key generation. To this aim, known techniques have been developed exploiting the transfer function of symmetric channels. However, the PLC channel is in general not symmetric, but just reciprocal. Therefore, in this paper, we first analyze the characteristics of the channel to verify whether physical layer key generation can be implemented. Then, we propose two novel methods that exploit the reciprocity of the PLC channel to generate common information by the two intended users. This information is processed through different quantization techniques to generate secret keys locally. To assess the security of the generated keys, we analyze the spatial correlation of PLC channels. This allows verifying whether the eavesdropper’s channels are weakly correlated with the intended users’ channel. Consequently, it is found that the information leaked to a possible eavesdropper has very low correlation to the locally generated key. The analysis and proposed methods are validated on a measurement dataset.