The ENEL's experience on the evolution of excitation control systems through microprocessor technology

Over recent years, the evolution of microprocessor technology with the consequent availability of reliable, high performance, low cost digital hardware and powerful software tools and the prospect of growing difficulties in the maintenance of analog apparatus, has led many manufacturers to develop new digital AVRs. Many benefits are expected from the use of microprocessors as wider flexibility, improvements in control performance and autodiagnostics, richer information for the local and remote operator. To exploit these advantages ENEL, the Italian Electricity Company, encouraged the Italian electromechanical manufacturers to develop a new generation of digital AVR. The paper, after a brief glance over the general problems and advantages deriving from the use of microprocessor technology, gives an overview of the most technical aspects to be envisaged in the design of digital AVR and shows the differences in the approach and the novelties coming out with respect to the traditional analogue solution. It deepens design aspects regarding the hardware and software architecture, the reliability and the safety, factors affecting interface, response the criteria for evaluating dynamic alteration. An example of the advanced digital AVR is presented in detail.