Application of the conditioned network concept in high frequency power line carrier

Abstract

The aim of the research described in this thesis was to investigate the possible use of underground Low Voltage Distribution Networks as a medium for the propagation of high frequency communication and data signals. Although the results and observations presented are based upon work carried out on a typical UK urban underground network, the same principles apply to most European underground Low Voltage Distribution Networks. The work was based around the use of frequencies greater than 1 MHz; these high frequencies provide enough bandwidth for a number of value added services to be offered in addition to the more usual Utility requirements for remote meter reading and load control. The research resulted in the development of an in-line filter element designed to limit the amount of Power Line Carrier noise egress from a distribution network whilst at the same time reducing the amount of high frequency noise entering the network. The effects of the Electricity Distribution Network on high frequency signals are discussed in some detail. All Power Line Carrier systems must be capable of operating in the presence of noise. Network topology and individual network elements have a significant effect on high frequency signals; a number of topologies are described and the effects of changes in characteristic impedance and discontinuities are discussed. The results and observations were largely obtained from a Low Voltage Electricity Distribution Network in Kendal, Cumbria. The limited availability of expensive high frequency test equipment resulted in the need to develop unique testing procedures; these are described in full. Sample results from the tests undertaken in Kendal are presented and discussed. The Conditioned Network concept is outlined and the design rules used to develop the in-line Conditioning Unit highlighted. A mathematical model for the filter element of the Conditioning Unit is developed and compared to empirical results obtained from laboratory experiments.