Response of Steam and Hydroelectric Generating Plants to Generation Control Tests

This paper presents some of the control characteristics of generating plants as determined by field measurement. Tests on generating units in service have determined that governor dead band varies widely between governors and between load points for some governors. Large new steam turbines have been found with governors having dead bands so large that the governor seldom caused the unit to help correct system frequency. The backlash in governor control linkages on some units was found to cause long time lags in control when initiated by automatic dispatching systems. Time delays in combustion control action and boiler thermal time lags were measured. These caused generation to continue to change for periods of time following a change in turbine control valve position. Frequency-response tests of generation controls of an over-all generating plant were conducted. Time delays in generation change measured after step changes in controls help explain the phase and magnitude changes measured during frequency-response tests. This paper shows that control characteristics can be measured with today's manually controlled generating plants. Some of the data obtained may be useful in designing improved controls for tomorrow's computer-operated plants.