Field Tests and Simulation of a High Initial Response Brushless Excitation System

The extremely long transmission distances associated with the Colstrip mine-mouth power plant called for stability improvement measures in the planning stages which included the application of high initial response excitation systems. The brushless excitation systems on the 819 MVA Colstrip Units 3 and 4 are designed to provide high initial response characteristics. Field tests were conducted during unit operation in which the fast large and small-signal response was successfully demonstrated. Response times are similar to that of static systems, without the use of brushes or collectors. Excitation system model constants were calculated based on hardware characteristics. Simulation results show the ability of the model to accurately reproduce the actual excitation system response.