Assessment on Speed Governor Performance of Turbine of Vajilalongkorn Hydropower Plant

Abstract

This paper concern with performance assessment of the guide vane position actuator when controlled via a high-speed linear servo valve adopted as a replacement of a retired electro-hydraulic convertor.  The valve was selected based on sufficient range of delivered oil flow and response of control signal. Due to change in dynamic characteristics of the valve, control parameters were adjusted, and the system response was studied after such replacement according to function of the unit, which are 1) Governor Dry Test, for assessment on response of auxiliary servo motor speed within the operation range, and 2) Governor Wet Test, for assessment on response of the whole governor unit. The Unit Protection trip testing scheme was performed to evaluate the system response to rapid disengagement of turbine load with pressure rise of the turbine conduit. It was found that the turbine was protected against overspeed as the guide vane was closed at sufficient speed resulting only 1.31% overshoot whereas the acceptance criterion is not greater than 54%. The maximum pressure of inlet conduit was found at 8.615 N/cm² and was within an acceptable limit at 11.3 N/cm². When the unit was started from rest to a rated speed, the period required since the guide vane started to close until the time the speed approach the set point was 33 second. It then required another 50 second for the turbine speed to be stabilized on the rated value. This was acceptable for further testing scheme on engagement of generator and feeder of electricity to the distribution system.