Adjustment of wicket gates important to maintaining machine performance
- Virginia Power, Glen Allen (United States)
Meeting acceptable variances for final face-to-face clearances between wicket gates is critical to the proper operation of a hydroelectric machine. Accurate adjustment enables water to flow evenly into each section of the runner. It permits wicket gates to open and close as designed, minimizing water loss and leakage, and extends the life of wicket gate linkages. Typically, wicket gates are checked and adjusted during major maintenance. In the case of a Kaplan runner, uneven flow may unbalance the runner and lead to shaft runout and loss in efficiency. Face-to-face clearances of wicket gates become even more crucial in units operating under high heads, especially Francis turbines and pump-turbines, which work with less water for the amount of power produced and therefore are more dependent on proper flow. In hydro plants without variable frequency converters, brakes must be applied to the generator to shut down a unit. Operators typically wait until the runner is at 60 percent of speed before applying brakes. If wicket gates are leaking water because they are not adjusted to the proper variances, it becomes difficult to bring the machine to a complete stop in a normal manner. Such a condition could be detrimental to the hydroelectric machine, which will continue to rotate after the brakes are applied but without proper lubrication to moving parts. At plants without spherical valves, proper adjustment of wicket gates is critical for shutting off flow during periods when units are shut down. It also benefits units designed to operate in a synchronous condensing mode (where the tailwater below the runner is depressed, the runner spins in air, and the generator is used as a motor). If the wicket gates leak badly as a result of poor adjustment, compressed air must be continually supplied to the unit to keep the tailwater depressed below the runner.
- OSTI ID:
- 6848365
- Journal Information:
- Hydro Review; (United States), Vol. 12:2; ISSN 0884-0385
- Country of Publication:
- United States
- Language:
- English
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