JPS5912177A - Increase and decrease method of revolving speed of valve water wheel - Google Patents

Abstract

PURPOSE:To permit to restrict the revolving speed increase of the water wheel and a generator upon interrupting a load at a low rate by a method wherein a guide vane is closed totally and a runner vane is fully opened quickly simultaneously with the interruption of the load of the valve water wheel. CONSTITUTION:In the water wheel having variable opening degrees of the guide vane and the runner vane, and guide vane 11 is fully closed simultaneously with the interruption of the load, as shown by a broken line in the diagram (a). On the other hand, the runner area vane 12 is fully opened rapidly simultaneously with the interruption of the load, as shown by a broken line in the diagram (b). According to this method, the flow amount of water flowed through the water wheel is somewhat increased compared with a conventional decreasing method, however, a water wheel efficiency is decreased and the loss of the water wheel is increased, thereby enabling to prevent the increase of the revolving speed. As a result, the increasing value 13 of the revolving speed of the water wheel generator becomes about 40% of the maximum increasing value DELTAn, as shown by the broken line in the diagram (c) and may be reduced lower than the value in the conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing the increase in rotational speed of a water turbine/generator due to load shedding of a valve water turbine having movable blades.

Conventionally, in valve turbines with a head of 10 m or less, the value of L-V on the suction pipe side of the water turbine (length of the penstock) x (average flow velocity of water flowing through the iron pipe) is equal to the value of L-V on the upstream side. It is often larger than the value (length of penstock) x (average flow velocity of water flowing through the penstock). In such a case, the pressure on the suction pipe side decreases as the load on the water turbine is cut off, increasing the apparent head.

For example, a water turbine with a head of 6m has a pressure drop of 2m on the suction pipe side, and 1ff on the upstream side! If there is a pressure increase of 9 degrees, the increase value Δn of 9 degrees will be about 60%. Now, for example, a customer requests that the rotational speed increase value △n be kept at around 40%.
In this case, it is possible to respond by increasing the flywheel effect GD of the generator by approximately 50 inches compared to the conventional method, but this method would result in a considerable increase in cost.
It is desired to suppress the increase in the rotational speed of the water turbine/generator due to load shedding without increasing the speed.

A conventional method for reducing the increase in rotational speed during load shedding of a valve water turbine will be explained based on the drawings.

Figure 1 is a diagram showing the opening of the guide vane and runner vane and the increase in rotational speed of the water turbine and generator due to load shedding of the valve turbine. In Figure 1 (a), the horizontal axis is time, Figure 1(b) is a diagram of the guide vane opening degree with the vertical axis as the opening degree (a,), and Figure 1(b) is a diagram of the guide vane opening degree with the horizontal axis as time and the vertical axis as the opening degree (ψ). FIG. 1(C) is a diagram of the rotational speed increase value Δn of the water turbine/generator, with the horizontal axis representing time and the vertical axis representing the rate of increase in rotational speed (%). In the figure, an example of a conventional method for reducing an increase in rotational speed due to load shedding of a water turbine is shown by a solid line.

As shown in FIGS. 1(a) and 1(b), in the conventional method, the guide vane 1 and runner vane 2 are simultaneously closed when the load on the water turbine is cut off, and the complete closure of the kite vane 1 is confirmed. As soon as the runner reached n, the runner vane 2 was opened rapidly. In this method, the kite vane 1 and the runner vane 2 are closed in an on-cam state.

After the guide vane 1 is fully closed, the runner vane 2 is suddenly opened to increase stirring loss and suppress the increase in the rotational speed of the water turbine/generator.

In the above method, as shown in FIG.
5 The increase is suppressed to some extent as runner vane 2 is fully opened, but the increase is quite large. 5 The maximum increase in rotational speed is △ because Gy of the generator is generally small. It was normal for n to be around 60%. Therefore, the maximum increase value of 1 rotation speed △nf: O60%
In order to make it smaller, it is necessary to increase the GIy of the generator, which has the disadvantage of increasing costs.

The present invention eliminates the above-mentioned drawbacks and provides a valve water turbine that can suppress the increase in rotational speed of the water turbine and generator due to load shedding of the water turbine without increasing the flywheel effect GD"i of the generator. The object of the present invention is to provide a method for reducing the increase in rotational speed.

According to the present invention, the above-mentioned object is a method for reducing the increase in rotational speed due to load shedding of a valve water turbine in which the opening degrees of guide vanes and runner vanes can be changed, This is accomplished by fully closing the guide vanes and quickly fully opening the runner vanes simultaneously with the load shedding of the water turbine.

Embodiments of the present invention will be described based on the drawings.

In FIG. 1(a), FIG. 1(b), and FIG. 1(C), an embodiment of the method of reducing the increase in rotational speed due to load shedding according to the present invention is shown by a broken line. In the reduction method of the present invention, the guide vane 111 is completely closed as shown by the broken line in FIG. 1(a) at the same time as the load on the water turbine is cut off. On the other hand, the runner vane 12 simultaneously completely opens the load shedding of the water turbine, as shown by the broken line in FIG. 1(b). In this method, the guide vane 11
The relationship between the runner vane 12 and the runner vane 12 becomes an off-cam state, and the flow rate flowing through the turbine increases somewhat compared to the conventional reduction method, but the efficiency of the turbine decreases significantly, so the loss of the turbine increases and prevents the rotation speed from increasing. Become.

In the above method, as shown by the broken line in Fig. 1(C), the increase value 13 of the rotation speed of the water turbine/generator increases at the same time as the load is removed from the water turbine, but the maximum increase value △n of one rotation speed is approximately 40%, which can be significantly reduced compared to the reduction method shown in the conventional embodiment.

As mentioned above, the present invention fully closes the guide vanes at the same time as the load of the water turbine is cut off, and also quickly fully opens the runner vanes to prevent the runner vanes from stirring, thereby increasing the ``-5 = GD'', and also increasing the strength of one rotation. It is possible to provide a method for reducing the increase in rotational speed of a valve water turbine that can meet customer requests at low cost without reducing fatigue strength.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the opening of the kite vane and runner vane and the increase in rotational speed of the water turbine and generator due to load shedding of the valve turbine. In Figure 1 (a), the horizontal axis is time, and the vertical axis is time. Fig. 1(b) is a diagram of the opening degree of the guide vane where the horizontal axis is time and the vertical axis is the opening degree (ψ). In Figure 1 (C), the horizontal axis is time, and the state noodles~
The rotational speed of the generator in the water wheel, where the vertical axis is the increase in rotational speed (%) It is a diagram of the increase value (Δn). 11... Opening degree of guide vane, 12... Opening degree of runner vane, 13... Increase value of rotation speed. 6-

Claims (1)

[Claims] ■) In a valve water turbine in which the opening degree of the guide vane and runner vane can be changed, the guide vane is fully closed at the same time as the load is removed from the water turbine in order to reduce the increase in rotational speed that occurs when the load is removed from the water turbine. A method for reducing an increase in rotational speed of a valve water turbine, characterized in that the runner vane is rapidly fully opened.