CHARACTERISATION OF COMMUNICATION CHANNEL ON HIGH VOLTAGE ENERGY TRANSPORT AND DISTRIBUTION SYSTEMS

CHARACTERISATION OF COMMUNICATION CHANNEL ON HIGH VOLTAGE ENERGY TRANSPORT AND DISTRIBUTION SYSTEMS Power Line Communication (PLC) can be used to create a communication system across Medium/Low Voltage electrical systems. It enables establishing digital communications without the need for extra wires allowing transmission of data and electricity over the same media. The system, which is made up of a transmitter and a receiver, ensures monitoring and control of electrical distribution installations over long distances, particularly in situations where maintenance is challenging. Despite its benefits, PLC channel is quite harsh and presents a number of challenges. With respect to frequency, location, environment and the sort of equipment connected to it, a channel’s characteristics and properties change. The communication band spans between 10kHz and 500kHz, and is primarily due to the fact that the power grid was not initially intended to be used for communications and also is optimised to work at a super low frequency band (50-60Hz). The first purpose of the thesis is to outline the key benefits and disadvantages of PLC communication over other technologies (Fiber, Wi-Fi), analyze a power grid at various voltage levels and look at applicable standards and regulations. Characterising the transmitter/receiver input impedance as a function of frequency, as well as the main advantages of the differential signalling employed to transmit the data, is fundamental to understand the line budget link, the impedance mismatch between the transmitter, the transmission line and the receiver, as well as the value of reflections. These data will be combined to determine the maximum power transfer. The influence of cable geometries on power and signal energy transmission over MV/LV networks has been modelled using lossy Transmission Line Theory. Since the communication is differential, two-port equivalent circuit and S-Parameters have been presented in order to compare results about characteristic parameters of the cables obtained through equations and simulations on Matlab with measured data, collected through a Vector Network Analyser (VNA). An overview of step-up/step-down transformers (bidirectional), which are used to shift voltage levels at low frequency maintaining the same amount of power, was made since data, generated and retrieved on LV side, had to travel across MV/LV power line channel. At 50-60Hz, non-idealities which can be represented with resistive and inductive behaviours, were measured using the No Load Test, Short Circuit Test and Winding Resistance Measurement and a low frequency TF (Transfer Function) has been implemented through a simulation on LTspice. However, given that data transmission happens at 133 kHz, an augmented model of the transformers has been considered that takes into account stray capacitances that become crucial when the wide band TF of the transformers has to be obtained. The VNA was used to measure it and an LTspice model was developed. The model was compared with the real TF of the transformer to ascertain how trustworthy and robust it was. The maximum distance for the signal to travel between the transmitter and receiver before noise cancels it has been estimated, and it has been determined which modification in the component selection can improve it while always considering the cost-benefit ratio. Finally, an innovative solution has been proposed, which tries to remove some components in the network configuration with a lower overall cost.