JPS628636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the operation of a multistage pump water turbine in which each stage is connected by a return passage.

Generally, the operation of a pump-turbine is controlled by adjusting the opening degree of guide vanes provided on the outer periphery of the runner to adjust the flow rate of water flowing through the runner. A multi-stage pump turbine has a flow path configuration in which each stage has a runner and each stage is connected by a return passage, but for ease of explanation, we will use a Francis type 2 pump turbine as shown in Figure 1 as an example. The present invention will be explained by taking the case of a stage pump water turbine. 1 is a low-pressure step runner, 2 is a same-part guide vane, 3 is a high-pressure step runner, and 4 is a same-part guide vane, and the low-pressure stage and the high-pressure stage are connected by a return passage 5.

In this flow path configuration, when the water turbine is in operation, the water flow flowing from the hydraulic pipe 7 into the casing 6 connected thereto is directed to the guide vanes 4 and runners 3 of the high pressure stage.
The water passes through the return passage 5, passes through the guide vanes 2 and runners 1 of the low pressure stage, and is discharged into the suction pipe 8 connected to a discharge channel (not shown). on the other hand,
When the pump is operating, the water flow pumped by the runner 1 of the low pressure stage flows through the opposite route to that when the water turbine is operating.

In a pump-turbine, when the guide vanes are opened at the time of starting the turbine or shutting down the pump to shift to turbine operation or pump operation, this is done by controlling the opening of the guide vanes, which are normally in a fully closed state, to a predetermined opening degree. In this case, when the guide vane is fully closed, the penstock is cut off and the flow path inside the guide vane, which is protected from being affected by the water pressure of the penstock, is exposed to the water pressure of the penstock at the same time as the guide vane opens. In addition to this, the water flow rate changes suddenly due to the guide vane opening, so water pressure fluctuations occur in the penstock pipeline due to the water hammer phenomenon caused by flow rate changes, and if the fluctuating water pressure is abnormally large, the hydraulic Machines are subjected to extremely harsh conditions, and in some cases, accidents such as destruction can occur.

Therefore, in such cases, guide vane control is required to safely control the operation of the pump-turbine without putting it in a dangerous operating state. This is an important problem in multi-stage pump turbines, which tend to have weak structural strength due to their complex flow path shapes.

Generally, the flow path of a pump-turbine is reduced in size in the guide vane portion, so that the water flow is also reduced in size when flowing through the guide vane portion.

Therefore, in a multi-stage pump-turbine in which the flow paths of each stage are connected by the return passage 5, when the opening of the guide vanes 2 and 4 of each stage is controlled under different opening states, the flow rate is is controlled under the control of the guide vane at the step with the smaller guide vane opening degree among the steps. When the flow rate is suddenly changed by guide vane control, a water pressure fluctuation occurs in the penstock line 7 due to the water hammer phenomenon, which also affects the flow path of the multi-stage pump turbine that communicates with the penstock line 7. In this case, the pressure waves due to water pressure fluctuations are mainly reflected at the stepped guide vane section where the guide vane opening is small, and most of the pressure waves are reflected on the hydraulic pipe side outside the guide vane. The water is transmitted to the flow path section, and only a small amount is transmitted to the inner flow path section, so the outside flow path section is greatly affected by water pressure fluctuations and falls into a severe state of strength, but the inner flow path section is In this case, the influence of water pressure fluctuation is small. In this way, in a multi-stage pump-turbine, when the guide vane is opened when the turbine or pump is started, the flow rate is suddenly changed, and the operation of the turbine or pump is shifted to operation. Depending on the control method, the degree of influence that the water pressure state of the water penstock, such as water pressure fluctuations, has on the flow path section of the pump-turbine, that is, the safety of the machine, will be greatly influenced.

In addition, as a guide vane control method, a guide vane is provided in each step, and the guide vanes in each step are opened all at once, and the guide vanes in the highest pressure step are slower in pump operation than the guide vanes in other steps. However, for water turbine operation, a system has been proposed in which the opening is controlled at a faster speed.
18553). However, during water turbine operation, the guide vanes at the highest pressure stage always maintain a larger opening than the other stages, so severe water pressure fluctuations in the penstock due to the guide vane opening control occur on the low pressure side with a small opening. This causes a problem that directly spreads to the step section, exposing the pump turbine to a dangerous operating condition due to its strength.

In this way, conventional methods cannot safely control either water turbine operation or pump operation, and there are many technologically unexplored fields for multi-stage pump turbines themselves. At present, no accurate operation control method has been proposed for transitioning to operation.

The purpose of the present invention is to suppress the spread of water pressure fluctuations that occur in the hydraulic pipe line to the low-pressure side stage during guide vane opening control during operation of either the water turbine or the pump, so as not to put the pump water turbine into a dangerous operating state. An object of the present invention is to provide a method for controlling the operation of a multi-stage pump turbine.

In order to achieve the above object, the present invention provides a multi-stage pump-turbine in which the flow paths of each stage from the lowest pressure stage to the highest pressure stage are connected by return passages, when the turbine is started or the pump is shut off. When opening a guide vane to shift to a water turbine or pump operation mode, regardless of this operation mode, first open the guide vanes of the other stages with the guide vane of the highest pressure stage fully closed, and then The guide vane of the highest pressure stage is opened, and the opening of the guide vane of the highest pressure stage is maintained at the same or lower than the guide vane opening of the other stages, and the opening of the guide vane is controlled to a predetermined opening. It is characterized by making people do things.

In the following, we will take the Francis type two-stage pump-turbine, which is an example of a multi-stage pump-turbine shown in Fig. 1, as an example, and
An embodiment of the present invention will be described with reference to the drawings.

In the Francis-type two-stage pump turbine shown in Figure 1, when the guide vane is opened at the time of starting the turbine or shutting down the pump to shift to operation of the turbine or pump, the horizontal axis in Figure 2 represents time t, and the vertical axis represents the guide vane. In the guide vane control diagram showing the opening degree a of guide vane 4 at the highest pressure stage (diagram G4)
When the guide vane 2 of the other stage is fully closed,
(line diagram G2), then open the highest pressure stage guide vane 4, and maintain the highest pressure stage guide vane opening below the other stage guide vane opening to a predetermined opening a ₀ By controlling the guide vanes until the opening is reached (for example, the no-load opening in the case of a water turbine or the specified opening in the case of a pump), the required operation of the water turbine or pump is started.

First, we will discuss an example of the effect when starting a water turbine.

In this case, when the highest pressure stage guide vane 4 is fully closed and the other stage guide vane 2 is slightly opened, the low pressure side flow path inside the fully closed guide vane 4 is equipped with a hydraulic pipe. Since the high water pressure of step 7 does not act and the low water pressure on the spillway side acts, it is in an extremely safe state in terms of strength, and the guide vanes in the other stages that are in this flow path and are affected by low water pressure. Since the pressure difference before and after the guide vane 2 is small, and as a result, the opening/closing hydraulic moment is very small, the opening of the other step guide vanes 2 can be controlled with an extremely small operating force.

In this way, in a state that is safe in terms of strength and with a small operating force, first open the guide vanes 2 in the other stages to communicate the flow path from the lowest pressure stage to the highest pressure stage, and then open the guide vanes 2 in the highest pressure stage. 4 is opened to smooth the water flow in the flow path to start the water turbine, and the highest pressure step guide vane opening is maintained below the other step guide vane openings until the guide vane reaches a predetermined _opening . Since the control is performed, the influence of water pressure fluctuations in the penstock line caused by changes in flow rate due to guide vane opening control is reduced to the casing 6, which is located on the penstock side side of the guide vane 4 at the highest pressure stage where the guide vane opening is small. Although it is large in extremely limited flow passages, such as, it is relatively small in the low pressure side flow passage inside the highest pressure stage guide vane 4, which occupies most of the multistage hydromechanical flow passage. Therefore, most of the flow path sections are strong and safe even against water pressure fluctuations.

If, contrary to the case of this embodiment, the highest pressure step guide vane 4 is maintained in an over-open state relative to the other step guide vanes 2, the high water pressure of the hydraulic pipe 7 will be applied to the other step. Since the flow path on the low-pressure stage side leading to the guide vane 2 is affected, the strength of the multi-stage pump-turbine is extremely severe, and the pressure difference between the front and rear of the guide vane 2 on other stages that are affected by high water pressure increases. As a result, the opening/closing hydraulic moment becomes extremely large, requiring an excessive operating force to control the opening.Furthermore, if the guide vane opening degree after opening is smaller than that of the guide vane at the highest pressure stage, the water pressure will increase. The influence of water pressure fluctuations in the pipeline greatly spreads over a wide range of passages up to the small opening guide vane section, resulting in serious problems such as putting the machine in a dangerous situation.

Next, an example of the effect when the pump is shut off will be described.

In this case, when the guide vanes of each stage are fully closed, the runners of each stage are in a state of pump shut-off operation in which the runner is operated underwater at a specified rotational speed.
The guide vane inner flow path near the outer periphery of the runner receives shutoff water pressure and has relatively high water pressure, but since the guide vane is fully closed, the guide vane inner flow path is cut off and the guide vane outer flow path does not receive shutoff water pressure. In this section, the water pressure is relatively low in each stage except for the guide vane outer flow path of the highest pressure stage, which communicates with the high pressure water pressure pipe 7, that is, the guide vanes in each stage are completely closed. During pump shut-off operation, the water pressure distribution in the flow path of the multistage pump-turbine is unbalanced, such as the working water pressure being different in the inner flow path of the guide vane. Generally, when a guide vane receives water pressure when fully closed, it is designed to receive a hydraulic moment in the closing direction if the outside water pressure is relatively high, and conversely to receive a hydraulic moment in the opening direction if the inside water pressure is relatively high. During the shut-off operation, a hydraulic moment in the opening direction acts on the guide vane where the inner water pressure is relatively high.

Therefore, when the other step guide vanes 2 except for the highest pressure step guide vane 4 are opened first using the method of this embodiment when the pump is shut off, the other step guide vanes 2 will have a hydraulic moment in the opening direction. Since there is a self-opening force in response, the opening can be performed with an extremely small operating force.Furthermore, the flow path is communicated from the lowest pressure stage to the highest pressure stage by the opening of the other stage guide vane 2, and as a result, The cutoff water pressure of each step is added sequentially from the lowest pressure step to the highest pressure step, and the total sum of the cutoff water pressure acts on the highest pressure step where the guide vane is still fully closed. The unbalanced water pressure distribution along the way is corrected, and the water pressure gradually increases toward the high pressure stage side, resulting in a hydraulically natural and appropriate water pressure distribution, resulting in an extremely stable and appropriate operating state, and therefore stable as shown above. Under these conditions, it is possible to shift to pumping operation.

In this stable shut-off operation, the water pressure of the water penstock 7 acts on the guide vane outer flow path in the highest pressure stage, and the water pressure on the guide vane inner flow path is relatively higher than the water pressure of the water penstock 7. Since the cut-off water pressure that can lift water is acting, the guide vane 4 at the highest pressure stage when fully closed receives a hydraulic moment in the opening direction, and the operating force is extremely small as in the case of the guide vane 2 at other stages. Opening can be done at . That is, according to the method of this embodiment, finally, the highest pressure stage guide vane 4 can be easily opened with a small operating force and in an extremely stable operating state to shift to pumping operation. Furthermore, after the highest pressure stage guide vane 4 is opened, the highest pressure stage guide vane opening degree is maintained below the other stage guide vane opening degrees and guide vane control is performed until the predetermined opening degree _a0 . Even if water pressure fluctuations occur in the penstock line 7 due to flow rate changes due to guide vane control,
The influence of water pressure fluctuations is small in the low-pressure stage side flow path portion inside the highest pressure stage guide vane 4, which is slightly opened, so that safe control can be performed even against water pressure fluctuations.

As described above, according to the present invention, it is possible to open the other step guide vanes with a small operating force, and
It is possible to suppress the spread of water pressure fluctuations induced in the water penstock to the low-pressure side stage, and it is possible to safely control operation at startup.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a two-stage Francis type pump-turbine showing an embodiment of the multi-stage pump-turbine, and FIG. 2 is a guide vane control diagram showing an embodiment of the present invention. 1, 3...Runner, 2, 4...Guide vane,
5... Return passage, 6... Casing, 7... Hydraulic pipe.

Claims (1)

[Claims] 1. In a multi-stage pump-turbine in which the flow passages of each stage from the lowest pressure stage to the highest pressure stage are connected by return passages, the guide vanes are opened when the turbine is started or the pump is shut off. When shifting to the operation mode, regardless of this operation mode, first open the guide vanes of the other stages with the guide vane of the highest pressure stage fully closed, then open the guide vane of the highest pressure stage, The multi-stage pump is characterized in that the opening degree of the guide vane in the highest pressure stage section is maintained at the same or lower than the opening degree of the guide vanes in the other stages, and the opening of the guide vane is controlled until it reaches a predetermined opening degree. How to control the operation of a water turbine.