Utility experience with digital excitation systems

Ontario Hydro, a Canadian utility with an installed capacity of over 30000 MW, has utilized static excitation systems on a large number of generators, ranging from 3 MVA to 1100 MVA in size, since the early 1960's. Ontario Hydro has always attempted to take advantage of excitation system control as a means of eliminating or reducing stability constraints on their operation. The advent of digital excitation systems offered us the opportunity to work with manufacturers to incorporate special features or controls which had previously required complex additional hardware. This paper discusses the authors' experience with these systems, from 1988 to date, as well as providing a list of items which merit consideration by utilities and manufacturers as they move toward the second generation of digitally-implemented systems.