Theoretical And Experimental Research On Speed Rise Of Turbine Units Load Rejection

Load rejection is the worst a running condition for units, a severe test for governing system. The inertia moment of rotor, the valve turn-off time, steam volume time constant and so on directly affect the unit momentary speed rise, and when the units start load rejection, before closing high and medium governing valves and extraction check valves, the pressure from extraction steam and steam heaters plunge, which will cause drain vaporization, then the steam will returns turbine to do work to lead to the unit overspeed, probably major accidents for unit equipments. Base on the close analysis and comparison of the principle of units load rejection, the numerical method of maximum momentary speed and tests of load rejection, in accordance with the conventional load rejection of current large capacity, high parameters units, raises two numerical methods of the maximum speed rise, and analyzes the advantages and disadvantages of the two methods. According to five units load rejection tests parameters and wave curves, combining theory and practice together, obtains several important parameters, accurately calculates the maximum momentary speed and the speed rise quantity caused by governing valves, especially the acquisition methods of valve equivalent closing time and rotor time constant, which greatly improve the accuracy of calculation. Compiles governing system test diagnosis program by using VB language, it can diagnose and evaluate the main function and test results by calling the test data, the fitting curves and formulas. Finally investigates some preparation matters, control items and logical optimization during the tests.