Hydraulic Turbine Govenors Flashcards
What is a hydraulic turbine govenor?
An automatic attachment for co trolling speed to a turbine, engine, or similar machinary.
What must a govenor do?
It must maintain a balance between the water input to the turbines and the power requirements of the system (electrical output of the turbine).
On a large system, what settings and variables must the govenor take into consideration?
Allowable loading of the transmission line
Maximum loading of the lines between systems
Hydraulic characteristics of the penstock and turbine
Flywheel effect of the rotating mass of the turbine and generator.
What detects and responds to any change in speed of the turbine?
The govenor ball head.
What determines the time required to center the small plunger?
It is determined by the setting of the dashpot needle valve.
Describe speed droop.
It is an additional adjustment in the speed adjustment linkage to cause the govenor to add speed adjustment in the lower direction as the gates open wider. It is necessary to eliminate “hunting”
What determines speed droop?
The amount of speed droop is the decrease in speed from zero load to full open gate and is expressed in percent of normal speed. Most govenors may be adjusted for speed droop settings of 0-5%.
How are generating units usually ran on a system?
They are ran in parallel with govenors controlling speed to all.
What is a govenor with zero speed droop called?
It is called an isochronous govenor. They will respond to take all additional load the system demands.
What sort of safety devices are in place with turbines and govenors?
Belt driven ball heads will either restrict gate or shut gates upon broken belt
Overspeed devices may be provided to close the gates if the speed exceeds a predetermined value.
Low govenor oil pressure switches may give alarms or shut the gates if the govenor oil pressure drops below a certain pressure.
To prevent water hammer pressure damages some units open auxiliary nozzles if the main nozzle closes too rapidly; others cause deflector vanes to direct water away from the vanes.
Describe a speeder rod.
The speeder rod transmits movement of the flyball assembly to the pilot valve, usually through a system of levers.
What is the restoring mechanism?
It is the linkage or cable between the servomotor and govenor that returns the pilot and relay valves to their neutral positions after the govenor has made a change in the position of the gates or needle.
What is a compensating dashpot?
It is inserted in the restoring mechanism to damp the gate movement, thus preventing overtravel and hunting.
