| 摘要 |
In a water level depressing operation of a multistage hydraulic machine, first, the guide vane in the maximum-pressure stage is totally closed. Then, the respective guide vanes in the remaining stages are left opened more or less, and compressed air is supplied, whereby the water level is depressed below the runner in the runner chamber in the minimum-pressure stage. Thereafter, the respective guide vanes in the stages other than the maximum-pressure stage are also totally closed. Then, when the water level in each of the runner chambers is raised as a result of, for example, leakage of water from the associated guide vane, compressed air is individually replenished to each of the runner chambers. Moreover, the accumulated water in the return blade passage is discharged to, the subsequent pressure stage runner chamber through the guide vane and finally to the draft tube owing to the individual control of the pressures of the respective runner chambers, whereby the water level in each of the runner chambers is controlled. Accordingly, it is possible to reliably depress the water level.
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