Modelling and estimating power-line communication (PLC) channels are complicated issues due to the complex network topologies, various junctions, and changeable loads. This paper focuses on the frequency response characteristics (FRCs) of medium-voltage (MV) PLC networks with special consideration of two scenarios that are often neglected but generally exist. In the first scenario, the MV distribution network is of the ring topology. In the second scenario, the MV overhead lines and underground cables join at junctions, and the shields of underground cables are grounded with nonzero grounding impedances at the junctions. These conditions lead to the failure of currently popular methods to different degrees. For this reason, we developed an effective method to calculate the FRCs of distribution networks for PLC applications. With this method, the frequency responses of nodes are simply expressed as the binary function of the overall tube propagation matrix and overall node scattering matrix, which is convenient for calculations and analyses. The proposed method was validated by the agreement between the calculated and measured FRCs. The results of two test examples showed that the proposed method performed better in comparison with the traditional approximate method when nonideal grounding conditions were taken into account. The proposed method is also independent of the network topology, so it can adapt to the dynamic changes of the network structure.
Verification of a Novel Method of Detecting Faults in Medium-Voltage Systems with Covered Conductors
