JPS63138170A - Guide vane shutting system for water wheel and reversible pump-turbine - Google Patents

Abstract

PURPOSE:To reduce the cost for water pressure iron pipe and the like by quickly closing a guide vane to a predetermined degree of opening when a water wheel etc. is shut from the load, and slowly closing after passage of a certain while, and thereby suppressing rise of the water pressure. CONSTITUTION:In case load shutoff is made during operation of a Francis turbine or a reversible pump-turbine with a small specific velocity, a guide vane is quickly closed to a certain predetermined degree of opening, which is maintained for a predetermined period of time T. Then the guide vane is slowly closed after passage of time T. Thereby water pressure rise in a water pressure iron pipe is suppressed to reduce cost for water pressure iron pipe etc. It is also made possible to reduce the water pressure drop in a tailrace so as to increase the suction height, so that the amount of excavation for power plant can be lessened to a great extent.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a guide vane closing system for water turbines and pump water turbines, which are the main engines of hydroelectric power plants.

(b) Prior Art Conventionally, in Francis turbines and pump turbines with small specific speeds, when it is necessary to perform load shedding during operation or to perform an emergency stop due to some unforeseen cause, the system shown in Fig. 2 is used. As shown in Figure 3, there is a closing method that closes almost suddenly after a sudden change in load and then transitions to a slight slow closing, as shown in Figure 3, a closing system that makes the sudden closing a little and lengthens the slow closing, or as shown in Figure 4. As shown in the figure, a closing method is known in which a short sudden closing is performed, followed by a slow closing, and then a further sudden closing.

(c) Problems to be Solved by the Invention However, in such a system, when the load on the water turbine and the pump turbine is cut off, there are problems such as an increase in water pressure on the penstock side and a drop in water pressure on the side of the spillway. Also.

In order to suppress the increase in rotation of the water turbine and pump-turbine during load shedding, it is effective to increase the moment of inertia CD'' of the generator, but this increases the cost and also increases the moment of inertia GD'' of the generator. has a structural limit and cannot be increased indefinitely.

Furthermore, Fig. 5 is a diagram showing the relationship between the flow rate Q passing through the hydraulic machine and the rotation speed n of the runner at each guide vane opening degree a, using a curve, and the solid line is when the guide vane opening degree is constant. The two-dot chain line is the locus at load shedding, and the one-dot chain line is the runaway curve.

In the curve of FIG. 5, there is a part A where the flow rate Q decreases as the runner rotational speed n increases, but this is because the flow rate is throttled by the runner itself.

Therefore, in the conventional closure system described above, the guide vane restricts the flow rate Q even in the portion A where the runner rotational speed n increases and the flow rate decreases.

There were problems with the increase in water pressure in the penstock and the drop in water pressure in the spillway.

The object of this invention is to minimize the decrease in the flow rate Q in the portion A where the flow rate decreases without closing the guide vane opening.

(d) Means for solving the problem In order to achieve the above object, 1. In the present invention, when the load of a water turbine or a pump water turbine is interrupted, the guide vanes are first suddenly closed to a predetermined opening degree. Then, after a predetermined period of time has elapsed at that opening, the valve is gently closed again.

(e) At the time of load interruption of the working water turbine and the pump water turbine, the guide vanes are first suddenly closed to a predetermined opening, and then in the region where the flow rate decreases as the runner rotation speed increases, the guide vanes are closed to that opening. By keeping it as it is, the increase in water pressure in the penstock can be suppressed.

(f) Embodiment Figure 1 is a diagram showing the closing characteristics of the guide vane according to the present invention, where the flow rate does not change much even when the guide vane opening is large and the rotational speed increases (as the rotational speed n of the runner increases). In region B) of FIG. 5, where the flow rate Q cannot be reduced much by the runner itself, the guide vane is first abruptly closed. The reason for this is that when the guide vane opening degree a0 is large, the runaway n
This is to prevent harmful effects such as vibrations from occurring when entering lI.

Next, in part A of FIG. 1 (from point X to point Y, region A of FIG. 5), the guide vane opening degree a0 is kept constant.
Then, in part 1 of FIG. 1, that is, area C of FIG.
After that, start gently closing the guide vane again. Specifically, the guide vanes are reclosed once the maximum water pressure in the penstock and the minimum water pressure in the spillway have passed, and the vanes are fully closed.

This makes it possible to further suppress the increase in water pressure in the penstock or the drop in water pressure in the waterway.

(G) Effects of the Invention As is clear from the above explanation, (1) according to the present invention, by suppressing the increase in water pressure, the cost of penstocks, etc. can be reduced, and the amount of water pressure drop in the spillway can be reduced. Since the suction height H5 can be increased, the amount of excavation per power plant can be significantly reduced, and the cost of one power plant can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a closing characteristic diagram of the guide vane according to the present invention, Figs. 2 to 4 are control characteristic diagrams according to the conventional guide vane closing method, and Fig. 5 is a diagram showing the flow rate and flow rate depending on the guide vane opening of the hydraulic machine. FIG. 3 is a diagram showing the relationship between rotational speeds and operating characteristics. Representative Patent Attorney Kyo Yuasa 1:3; (5 others) LLSeC

Claims (1)

[Claims] 1) When the load of a water turbine or pump-turbine is interrupted, etc., the guide vanes are first suddenly closed to a predetermined opening, and then, after a predetermined period of time has elapsed at that opening, the guide vanes are gently closed again. A guide vane closing system for water turbines and pump water turbines featuring: