Evaluation of the proposed retirement of a condensing turbine generator on the paper mill electrical distribution system and utility ties

The problem, as described by this paper mill, is the desire to retire an inefficient condensing steam turbine generator for economic reasons and purchase additional power from the utility. The condensing unit, along with a modern extraction steam turbine generator and two utility ties, presently supply power to this three-bus medium voltage system via sync bus and reactor ties. A power system study commenced to determine the impact of the proposed change on the existing paper mill electrical distribution system as well as the existing utility ties. This paper describes the results of the analytical methods employed: power quality measurements, load flow analysis, short circuit analysis and transient stability simulations. Recommendations included alternatives to accommodate retirement of the condensing steam turbine generator, most significantly, the installation of a new power transformer as a third utility tie and the application of reactive compensation as filters at the three medium voltage busses.