JPH1137034A - Reversible pump turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the push-down water surface level of a reversible pump turbine under a phase modifying operation within an aptitude domain even in the case where during the phase modifying operation of one of reversible pump turbines to hold a discharge pipeline in common, a load shutdown occurs in another reversible pump turbine. SOLUTION: In a reversible pump turbine where high pressure air is supplied into a draft tube 6 to make the idle running operation of a runner in air possible, a high pressure air supplying pipe 7 and a high pressure air discharging pipe 13 are connected to the draft tube 6. In the draft tube 6, a free water surface low limit point 9c is set up at a water level position lower than a high pressure air supplying stop point, and when a water level in the draft tube is lower than the free water surface low limit point 9c, the high pressure air in the draft tube 6 is discharged through the high pressure air discharge pipe 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump-turbine in which high-pressure air is injected into a suction pipe, a free water surface is formed in the suction pipe by the high-pressure air, and the runner can run idle.

[0002]

2. Description of the Related Art In recent years, hydraulic machines such as pump-turbines have been designed to have a high head with a view to economy, and the suction height or the pushing depth of such a high-head hydraulic machine is determined from the viewpoint of preventing cavitation. , And as a result, the water pressure in the suction pipe is high.

[0003] Incidentally, in such a pump turbine, in order to stabilize the power system and quickly respond to a change in power demand, a phase adjustment operation in which the runner of the pump turbine runs idle for a long time is often performed.

FIG. 4 is a longitudinal sectional view schematically showing a pump-turbine for explaining the above-mentioned phase adjustment operation.

In FIG. 4, reference numeral 1 denotes a runner chamber of a pump turbine, in which a runner 3 provided at the lower end of a main shaft 2 is rotatably disposed. A spiral casing 4 is provided on the outer periphery of the runner chamber 1, and guide vanes 5 are arranged in a circumferential direction in a flow path connecting the runner chamber 1 and the spiral casing 4. A suction pipe 6 is connected to the lower end of the runner chamber 1.

[0006] A high-pressure air injection pipe 7 is connected to the suction pipe 6, and a water level detection pipe 8 for detecting the water level is connected to the water level detection pipe 8. Water level sensors 10a, 10b corresponding to the two water surface levels 9a, 9b are attached.

In such a pump-turbine, high-pressure air is injected into the suction pipe 6 through the high-pressure air injection pipe 7 after the guide vanes 5 are fully closed in order to reduce the power load during the phase adjustment operation. The water in the runner chamber 1 is drained into the suction pipe 6, the water surface 9 is pushed down by a predetermined distance from the lower end 3a of the runner 3, and the runner 3 is rotated in high-pressure air to reduce the driving torque. I have.

However, during such a phase adjustment operation, the air in the space between the runner 3 and the water surface is swirled in the direction of rotation by the action of the centrifugal wind pressure caused by the rotation of the runner 3, as shown in FIG. In addition, large undulations and swings occur on the water surface 9. This is particularly noticeable when the pressure in the suction pipe 6 is high.

In such a state, air is entrained below the water surface 9 and a large amount of air bubbles float in the water, and a part of the air bubbles is always supplied to the downstream side of the suction pipe 6 via the elbow portion 6a of the suction pipe 6. As a result, the water surface 9 in the suction pipe 6 gradually rises. When the water level 9 reaches the set water level 9a, the water level sensor 10a
Detects this and operates the control valve 7a of the high-pressure air injection pipe 7 to introduce high-pressure air into the suction pipe 6 to push down the water surface 9. When the water surface 9 drops to the set water surface level 9b, the water level sensor 10b detects this and stops supplying high-pressure air. In this way, the water surface 9 is always kept depressed by a predetermined distance from the lower end 3a of the runner 3, and the above operation is repeated in a long-time phase adjustment operation.

[0010]

[0005] However, as shown in FIG.
The penstock 11 and the discharge line 12 which are the same as the other pump turbines P2
In the case of the power plant sharing the above, when the load shedding of the other pump turbine occurs during the phase adjustment operation of the pump turbine, the pressure of the water discharge pipe 12 is short at almost the same time as the load shedding. descend. Then, in response to the decrease in water pressure, the runner 3
The high-pressure air filled in the space between the water and the water surface 9 in the suction pipe 6 expands, and the water surface 9 may drop rapidly until the water pressure and the air pressure are balanced.

However, since the water level sensors 10a and 10b attached to the water level detection pipe 8 are provided corresponding to the water surfaces 9a and 9b in order to cope with the above-described movement of the water surface in the suction pipe 6, There is a problem that it is not possible to cope with the sudden drop of the water surface.

That is, when the water surface 9 drops significantly above the water surface level 9b, the high-pressure air in the space above the water surface leaks at a stretch toward the downstream side 6b of the suction pipe 6, and as a result, the suction pipe 6 Water rapidly flows into the elbow 6a from the downstream side of the suction pipe 6, and the water level rises rapidly. At this time, as shown in FIG. 6, a part of the inflow water may reach the runner 3 due to the force at the time of inflow and the action of the swirling flow of the air in the suction pipe 6. Runner 3
In addition, the collision of water having a higher density than air causes fluctuations and vibrations of the shaft input, which has an unfavorable effect on stable phase adjustment operation.

[0013] In view of the above, the present invention provides a phase-shifting operation even when one of the pump-turbines sharing a water discharge pipe performs a phase-shifting operation and the other pump-turbine experiences load shedding. It is an object of the present invention to obtain a pump turbine capable of controlling the water level of a pumping turbine inside a water pump within an appropriate range.

[0014]

SUMMARY OF THE INVENTION According to the present invention, high-pressure air is injected into a suction pipe connected to a lower end of a runner chamber, and a free water surface is formed in the suction pipe so that the runner can run idle in air. In the pump water turbine,
A high-pressure air exhaust pipe for discharging high-pressure air in the suction pipe is connected together with a high-pressure air injection pipe for injecting high-pressure air into the suction pipe, and further below a high-pressure air injection stop point set at a free water level in the suction pipe. A lower limit of the free water level is set at the water level, and when the water level in the suction pipe falls below the lower limit of the free water level, an exhaust valve provided on the high-pressure air exhaust pipe is opened.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, a control valve 7a is connected to a suction pipe 6.
And a high-pressure air exhaust pipe 13 having an exhaust valve 13a for discharging high-pressure air in the suction pipe 6 is connected to the high-pressure air injection pipe 7 having The water level detecting pipe 8 for detecting the water level is provided for the water level 9a for re-injecting the high pressure air at a level close to the runner side, for the water level 9b for stopping the injection of the high pressure air below it, and further below. There are provided three water level sensors 10a, 10b, 10c for a water surface level 9c for exhausting the high pressure air, so as to detect the depressed water surface level in the suction pipe 6 in a stepwise manner. Then, the water level in the suction pipe 6 reaches the water level 9c, and when this is detected by the water level sensor 10c, the exhaust valve 13a is opened. When such a pump-turbine performs a so-called phase-shifting operation in which the runner 3 runs idle in the air, the guide vane 5 is fully closed, and the high-pressure air is introduced into the suction pipe 6 by the high-pressure air injection pipe 7. To drain the water in the runner chamber 1 into the suction pipe 6 to push down the water surface 9 by a predetermined distance from the lower end 3 a of the runner 3. In this case, the water surface level 6a and the water surface level 6b are usually set to the water surface in the suction pipe 6 in order to efficiently supply the high-pressure air. That is,
When lowering the water level for the first time, or after entering the phase adjustment operation, supply air by leak is performed, and the water level 6b is set as the water level at which the air supply is stopped. The water surface level 6a is set as a water surface level at which replenishment is performed so as not to approach too much.

The water level sensor 10b corresponding to the water surface level 6b is used to stop the injection of high-pressure air when the water surface in the suction pipe 6 passes from the water surface level 6b downward. Therefore, when the actual depressed water level is below the water level 6b, it is unclear how low the level is. In the normal case where the phase-shifting operation is performed by a single pump-turbine, no particular problem occurs. This is because the water surface levels 6a and 6b are set so that both the shaft input and the leak amount are smaller as shown in the diagram schematically showing the relationship between the depressed water surface and the leak amount and the shaft input in FIG. And a level closer to the runner lower end 3a. For this reason, there is ample room for the water level LC (FIG. 2) at which the amount of leakage starts to increase rapidly.

However, as described above, when it is conceivable that a plurality of pump-turbines connected by a single conduit perform the phase-shifting operation and the normal power generation operation at the same time, the pump-turbine that performs the phase-shifting operation It is expected that the change in the depressed water level in the suction pipe 6 will be extremely large when the load is cut off in the pump turbine that performs the normal power generation operation. In this case, it is conceivable that the water surface level is lowered even beyond the water surface level Lc shown in FIG. 2, and a large amount of high pressure air leaks to the downstream side of the suction pipe 6 and at the same time, the suction pipe 6
There is a possibility that water will suddenly flow from the downstream side to the elbow side 6a and the water surface will be disturbed.

However, in the present invention, the suction pipe 6
When the water level 9 in the inside falls to the water level 6c, it is detected by a water level sensor 10c attached to the water level detection pipe 8, the exhaust valve 13a of the high pressure air exhaust pipe 13 is opened, and the high pressure air in the suction pipe 6 is removed. Some are suddenly exhausted to the outside. Therefore, the surface of the water that was descending turned up
Next, when the water surface 9 reaches the water surface level 9b, the exhaust valve 13a of the high-pressure air exhaust pipe 13 is closed. In this way, the water surface 9 is brought to the water surface levels 9a and 9
b.

FIG. 3 is a view showing another embodiment of the present invention. A high-pressure air exhaust pipe 13 having an exhaust valve 13a is connected to the suction pipe 6 and the pressure in the suction pipe 6 is detected. A pressure sensor 14 is provided. Others are the same as those shown in FIG. Therefore, the pressure-electric signal during the phase adjustment operation of the pressure sensor 14 attached to the suction pipe 6 is basically governed by the dam water level of the lower pond to which the water discharge pipe is connected and the operation state of the other pump turbines. , Draft tube 6
Irrespective of the level of the water surface 9 in the interior, it therefore shows a constant value or only makes a gradual change in time. However, when load rejection occurs in another pump turbine, the pressure in the water discharge pipe changes within a short time of several seconds to several tens of seconds, unlike normal operation. Then, this pressure change is transmitted to the suction pipe 6 of the pump turbine performing the phase adjustment operation, and the water surface 9 changes rapidly.

The problem here is the effect of the pressure drop when the load is cut off, as described above. Therefore, the rate of pressure drop per hour of the signal of the pressure sensor 14 of the pump turbine performing the phase-shifting operation is monitored, and when this exceeds a predetermined value, for example, a value of 5 mHg / sec, load rejection occurs. Therefore, the exhaust valve 13a of the high-pressure air exhaust pipe 13 is opened, the air in the suction pipe 6 is exhausted, and the water level in the suction pipe 6 is prevented from being abnormally lowered.

Further, in the above embodiment, one of the water level sensor 10c and the pressure sensor 14 for detecting the third water surface level 9c is provided, but both of them are provided and both are used. Abnormal drop of the water surface 9 in the suction pipe 6 may be prevented by coping with the load interruption of the pump turbine.

That is, when the water pressure sensor 14 detects a pressure drop in the suction pipe 6 due to the load interruption, the exhaust valve 13a of the high-pressure air exhaust pipe 13 is opened to exhaust the air in the suction pipe 6 and to release the air. When the water level 9 rises and the water level 9c is detected by the water level sensor 10c, the exhaust valve 13a may be closed.

In this case, as compared with closing the exhaust valve 13a of the high-pressure air exhaust pipe 13 when the water level in the suction pipe 6 reaches the water surface level 9b as in the first and second embodiments, the suction pipe is 6, when the water surface 9 rises with the recovery of the water pressure after a certain period of time from the load rejection, the air pressure in the space above the water surface at the same water surface level increases. Slows down. Therefore, when the water surface 9 reaches the water surface level 9a detected by the water level sensor 10a and the high-pressure air is injected from the high-pressure air injection pipe 7 into the suction pipe 6, the overshoot above the water surface is reduced, and the shaft input is reduced. Increase can be reduced,
More stable control becomes possible.

[0025]

As described above, in the present invention, the high pressure air exhaust pipe is connected to the suction pipe, and the high pressure air exhaust pipe is connected to the high pressure air discharge pipe when the water level in the suction pipe falls below the high pressure air inflow stop point. I opened the exhaust valve
In the case where the pump turbine performing the phase-shift operation and the pump turbine performing the normal power generation operation are connected by a pipeline,
If the water level in the suction pipe of the pump turbine that is in phase operation is going to be lower than the predetermined water level when the load is cut off or the like in the pump turbine that is performing the power generation operation, the pump turbine through the high pressure air exhaust pipe will be used. High-pressure air is discharged to prevent the water level in the suction pipe from being lowered. Therefore,
Shaft input fluctuations and vibrations caused by abrupt leaks in the pump turbine performing the phase adjustment operation are prevented, and stable phase adjustment operation can be performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of a pump-turbine of the present invention.

FIG. 2 is a diagram showing a relationship between a pushing water surface level, an amount of air leakage, and an axis input during an idling operation.

FIG. 3 is a longitudinal sectional view showing another embodiment of the pump-turbine of the present invention.

FIG. 4 is a longitudinal sectional view showing a schematic configuration of a conventional pump-turbine.

FIG. 5 is a diagram schematically showing a power plant having a plurality of pump turbines sharing a pipeline.

FIG. 6 is a diagram showing a state inside the suction pipe when the water pressure in the suction pipe of the pump turbine performing the idling operation is abnormally decreased.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Runner chamber 2 Main shaft 3 Runner 4 Spiral casing 5 Guide vane 6 Suction pipe 7 High pressure air injection pipe 8 Water level detection pipe 9a, 9b, 9c Water level 10a, 10b, 10c Water level sensor 13 High pressure air exhaust pipe 13a Exhaust valve 14 Pressure sensor

Claims (4)

[Claims] 1. A pump-turbine wherein high-pressure air is injected into a suction pipe connected to a lower end of a runner chamber, and a free water surface is formed in the suction pipe so that the runner can run idle in air. And a high-pressure air exhaust pipe for discharging high-pressure air in the suction pipe together with a high-pressure air injection pipe for injecting high-pressure air into the suction pipe, and a high-pressure air injection stop point set to a free water level in the suction pipe. Further, a lower limit of the free water level is set at the lower water level position, and when the water level in the suction pipe falls below the free water lower limit, the exhaust valve provided on the high-pressure air exhaust pipe is opened. To do, a pump turbine. 2. A suction pipe is provided with a water level sensor for detecting a water level at a lower limit of a free water level, and an exhaust valve provided on the high-pressure air exhaust pipe is controlled in an opening direction by a detection signal from the water level sensor. The pump-turbine according to claim 1, characterized in that: 3. A pressure sensor for detecting pressure in the suction pipe is provided on the suction pipe, and an exhaust valve provided on the high-pressure air exhaust pipe is controlled in an opening direction by a detection signal from the pressure sensor. 2. The method of claim 1, wherein
The described pump turbine. 4. A suction pipe is provided with a water level sensor for detecting a predetermined water level further below a high-pressure air injection stop point, and a pressure sensor for detecting a pressure in the suction pipe corresponding to a water level at a lower limit of a free water level. The exhaust valve provided on the high-pressure air exhaust pipe is controlled in an opening direction by a detection signal from the pressure sensor, and the exhaust valve is closed by a detection signal from the water level sensor. Item 4. The pump-turbine according to Item 1.