  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 context, 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 high frequency
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 article, 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.
