Optimisation of UHF radio SCADA systems for electrical distribution networks
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.
This thesis presents the results of an investigation to establish methods to improve the performance of area radio based communication systems for Supervisory Control and Data Acquisition (SCADA) systems. The considerable scale on which an area radio network is used as a telecommunication network is quite unique to South Africa due to a lack of high bandwidth telecommunication systems in rural areas. Research was done to establish Key Performance Indicators (KPIs) to measure the performance of the area radio telecommunication systems. Two KPIs were chosen, namely Remote Terminal Unit (RTU) availability and Control Success Rate (CSR). These KPIs were trended over a three-year period to measure the effectiveness of measures taken to improve the systems. Two measures were implemented, namely to change the RTU radios, antennas and coaxial feeder cables and to redesign the communication systems in such a way to restrict multiple RTU protocols on the same area radio telecommunication network. The installation of new digital radios together with low loss coaxial cable and specific antennas improved the RTU availability from 96.87 % for the year 2002 to 99.17 % for the year 2004, which realised in an increase of 2.83 % for 432 installed RTUs. This measure, however, did not influence the CSR. The implementation of the newly designed communication networks had a significant influence on the control success rate of the SCADA systems and the KPI increased from 77.65 % for the year 2002 to 78.76 % for the year 2003 and 80.88 % for the year 2004. A drastic increase in performance was observed after the restriction of multiple RTU protocols on the same network during May 2004, where the value for twelve months prior to September 2005 was measured at 84.38 %. The utilisation of area radio telecommunication networks was measured for two operational networks and it was found to be well within the specifications of international accepted standards. One of these networks comprised of three repeaters and 84 installed RTUs and an average utilisation of 17 % and a peak utilisation of 25 % was measured. The other network had an installed base of 4 repeaters and 15 installed RTUs’s and an average utilisation of 3 % and a peak utilisation of 8 % was measured. This compares favourable with the IEEE standard 999-1992 , which recommends a channel utilisation of between 40 % and 60 %. Keywords : Key performance indicators, Radio telecommunication networks, Remote terminal unit