Transient Loading Improvements for Large Steam-Electric Generating Units

Abstract

The intent of this paper is to discuss the ultimate in operating flexibility during transient conditions that can be built into new designs having steam conditions of 2400 psig, 1050/1000 F reheat or above. The following discussion proposes an over-all operating philosophy in the hope of developing better understanding among the engineers, operators, and equipment manufacturers. Emphasis is placed upon steam temperature control to suit various turbine operating conditions. New methods proposed include a means of raising throttle steam enthalpy during hot turbine starts, a control and/or supervisory system for regulating unit start-ups and shutdowns, and a new means of cooling the low pressure turbine exhaust during start-up. As a result, for short duration turbine generator shutdowns as 8 hours, units may be unloaded rapidly at full pressure and in some cases may be restarted from turning gear to one third load restoring design primary steam temperature and pressure in as little as 35 minutes without sacrifice of safety.