Evaluation of the megawatt demand setter for load-follow operation of C-E's SYSTEM 80+

The Megawatt Demand Setter (MDS) is a digital supervisory control system that automatically assures that the turbine load is consistent with plant operating limits for critical parameters. The MDS is designed to avert plant trips by limiting the load demand during load transients and by reducing the turbine load if plant operating limits are approached or violated. The MDS, devised and patented by Combustion Engineering, Inc., in the 1970s for automatic load dispatching, has been installed at two plants. Those plants have since been operated in a base-load capacity, however, and have not needed to implement the load-follow capabilities of the MDS. As the percentage of electricity generated by nuclear units increases, the need to implement such load-follow capabilities will also increase. Combustion Engineering intends to incorporate improved load-follow capability in its SYSTEM 80+ nuclear steam supply system (NSSS) design. One aspect of this will be incorporation of the MDS in the design of the NUPLEX 80+ advanced control complex for system 80+. This paper presents an evaluation of two major design features of the MDS for load-follow operation based on simulation of SYSTEM 80+ plant responses