Applying static excitation systems

Many power generation plants in the pulp and paper industry are faced with high maintenance and downtime due to the excitation system. DC field breakers, motor driven rheostats, rotating exciter failures, commutator deterioration, and replacement parts for the automatic voltage regulator (AVR) are just a few of the problems typical of these aged power plants. The result is high overhead and potentially long down time of the generator system. The replacement of the rotating exciter and associated equipment for static excitation systems provides the positive solutions to these problems. The static exciter offers the design flexibility of easy retrofit for both small and larger rotating exciter systems. Additionally, it eliminates the maintenance overhead common to the brush type exciter. This article discusses the static exciter system that includes the power control devices (SCRs, also called thyristors), power transformer and automatic voltage regulator. The elimination of the DC field breaker can offer substantial cost savings. Solid state fast de-excitation circuits and its benefits are discussed. Lastly, selection criteria and application considerations are reviewed regarding types of static exciters.