JPS629748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for a water turbine or a pump water turbine having an S-shaped characteristic in which the rotation and flow rate are in the direction of the water turbine.

[Background of the invention]

In general, the runners of pump turbines, particularly high head pump turbines, are designed to provide sufficient centrifugal pumping action in order to obtain high head during pump operation.

However, this design adversely affects the turbine operation of the pump turbine. When the characteristics of a pump-turbine to which this design is adopted are expressed by a characteristic curve representing the relationship between the number of rotations per unit head (N ₁ ) and the flow rate per unit head (Q ₁ ) under a predetermined guide vane opening, This characteristic curve shows that in the water turbine operation region,
It has a first part where the value of Q ₁ decreases as the value of N ₁ increases, and a second part where the value of Q ₁ decreases as the value of N ₁ decreases.

For convenience of explanation, in this specification, the second
This part is called the S-characteristic part. Further, the characteristics of the pump-turbine in the S-characteristic portion are hereinafter referred to as S-characteristics.

The reason for this S-shaped characteristic is that when a water turbine is operating, water normally flows from the outer circumference of the runner toward the center, but as the runner rotates, the centrifugal force acting on the water increases, causing the water to flow. This is thought to be due to the flow being reversed and switching to pump flow.

Furthermore, it is thought that this is because the flow mode within the runner changes in a complicated manner when approaching this state. Regarding water turbine operation in the S-shaped characteristic section,
The torque per unit head (T ₁ ) also decreases as the number of revolutions per unit head (N ₁ ) decreases.

Normally, the operation of the pump-turbine is carried out in the first part. However, if the number of rotations per unit head (N ₁ ) increases suddenly and greatly, such as when the load is cut off, the load suddenly decreases, the water turbine is started, or when switching from phase adjustment operation to water turbine operation, the pump-turbine It will be operated in the S-characteristic section. When operation in the S-shaped characteristic part starts,
The operating point of the pump-turbine follows the S-shaped characteristic part from one end to the other, and first the flow rate per unit head (Q ₁ ) and the number of rotations per unit head (N ₁ ) decrease.
After that, Q ₁ and N ₁ increase while tracing the S-shaped characteristic part in the opposite direction, like a pendulum swinging back.
This reciprocating motion in the S-shaped characteristic portion continues almost permanently as long as the guide vane opening remains above a predetermined value, and will not end unless special measures are taken. During this period, the torque per unit head (T ₁ ) also repeatedly decreases and increases.

It is desirable to operate the pump-turbine while avoiding the S-shaped characteristic portion. This is because operation in the S-shaped characteristic part causes abnormal water pressure fluctuations in the penstock and draft tube, including a large water pressure rise and a large water pressure drop, as well as in the pump-turbine itself, resulting in severe water hammer and sometimes This is because it leads to water column separation. A load disconnection occurs, for example, when a disconnector is used to disconnect the generator connected to a pump-turbine and the main transformer, so that the power from the generator is not supplied to the power grid. .
In addition, water hammers can be used if either or both of the penstock and draft tubes are long.
Care must be taken to avoid large amplitudes.

The characteristics of a pump water turbine having S-shaped characteristics in the water turbine operation region are shown in FIGS. 1A and 1B.
In FIG. 1A, the characteristics of the pump-turbine are shown as the relationship between the number of revolutions per unit head (N ₁ ) and the flow rate per unit head (Q ₁ ), using the guide vane opening as a parameter. On the other hand, in FIG. 1B, the characteristics of the pump-turbine are shown using the same parameters as the relationship between the number of revolutions per unit head (N ₁ ) and the torque per unit head (T ₁ ).
N ₁ , Q ₁ and T ₁ are expressed by the following equations.

N ₁ = N/√, Q ₁ = Q/√, T ₁ = T/H In the above formula, the symbols N, Q and T are respectively,
It shows the rotation speed, flow rate, and torque of the pump-turbine, and H indicates the effective head of the pump-turbine.

Characteristic curves 1 and 1' are obtained under certain relatively large guide vane openings. Characteristic curves 2 and 2' are obtained under smaller guide vane openings. Characteristic curves 3 and 3' are also obtained at smaller guide vane openings.

In the ah section of characteristic curve 1, the value of Q ₁ decreases as N ₁ decreases. As mentioned above,
In this specification, this curve portion ah is referred to as S
This is called the character characteristic part. Similarly, curved portion b-i
is an S-shaped characteristic portion of characteristic curve 2, and curve portion cj is an S-shaped characteristic portion of characteristic curve 3. As is clear at first glance, the S-shaped characteristic portions ah of the characteristic curve 1 are longer than the S-shaped characteristic portions b-i of the characteristic curve 2; It is longer than the S-shaped characteristic portion c-j of No. 3. This means that as the guide vane opening becomes smaller, the length of the S-shaped characteristic portion becomes shorter.

As in FIG. 1A, in FIG. 1B, the curved sections a'-h', b'-i', and c'-j' are
These are S-shaped characteristic portions of characteristic curves 1', 2' and 3', respectively.

FIG. 1B is closely related to FIG. 1A. For example, Q ₁ =Q _1X , N ₁ =N _1X on curve 3 in Figure 1A
The point x that satisfies the above corresponds to the point X' on the curve 3' in FIG. 1B. Point x' is T ₁ = T _1X ', N ₁ = N _1X '
This is a point that satisfies (=N _1X ). Similarly, Figure 1A
Points a, b, c, d, e, f, h, i and j in FIG. 1B are respectively points a', b', c',
It corresponds to d′, e′, f′, h′, i′ and j′.

Curve Nr is a no-load flow rate curve. curve 1,
Intersection points α, β, and γ between curves 2 and 3 and curve Nr correspond to intersections α', β', and γ' between curves 1', 2', and 3' and straight line T ₁ =0, respectively.

Next, referring to characteristic curves 1 and 1', the operation of the pump turbine (power generation operation) will be explained. As described above, the characteristics corresponding to characteristic curves 1 and 1' are obtained when the guide vane opening is set to a relatively large value. Normally, the operation of a pump-turbine is as follows:
The upper part of the characteristic curve 1, that is, the S-shaped characteristic part a-
This is done in the curved portion above h. However, if, for example, the load applied to the pump-turbine is suddenly lost, the number of revolutions (N) of the pump-turbine increases rapidly, and the value of N ₁ also increases rapidly. Thus, the pump turbine begins to operate in the S-characteristic section. During operation in the S-characteristic section, the value of N ₁ decreases due to the decrease in the rotation speed (N) of the pump-turbine and the increase in the effective head H, and accordingly the value of Q ₁ also decreases. Now assuming that the value of H is constant, the decrease in the value of Q ₁ is
This means that the pump turbine flow rate (Q) decreases correspondingly. In reality, the value of H, ie the head difference between the pump-turbine inlet connected to the penstock and the pump-turbine outlet connected to the draft tube, increases at the same time as the flow rate Q decreases. In this way, once the value of N ₁ decreases, the flow rate Q decreases, and a decrease in the flow rate Q results in an increase in the effective head H of the pump-turbine. This increase in effective head H results in a further decrease in N ₁ , which in turn results in a further decrease in _{Q 1 .} In this way, once the operation in the S-shaped characteristic section begins, Q ₁ and N ₁ will move along the S-shaped characteristic section in the decreasing direction of Q ₁ , that is, in the direction from point a to point d. Continuously decreasing. It can be seen that Q ₁ and N ₁ decrease at an accelerated rate and continuously, as in the positive feedback control circuit.

When the operating point of the pump-turbine completes tracing the S-shaped characteristic part from point a to point h, the above phenomenon is gradually alleviated in the same way as in the negative feedback control circuit, and then reverses, and eventually changes from point h to S-shaped. The characteristic part will be traced in the direction of Q ₁ increase, ie from point h to point a. Tracing the S-shaped characteristic portion in the opposite direction is also performed in the same manner as the arrow positive feedback control circuit.

Assuming that the guide vane opening is constant, once the pump-turbine starts operating in the S-characteristic section, the above-mentioned reciprocating motion is repeated almost permanently. As explained above, such operation is undesirable. This is because it causes abnormal water pressure changes in each waterway system of a hydroelectric power plant, resulting in intense water hammer and sometimes water column separation phenomena.

It should be noted that these adverse effects associated with driving in an S-shaped section are reduced as the length of the S-shaped section is reduced. For example, if the guide vane opening is made smaller, the S-shaped characteristic part b-
If the pump-turbine is operated according to characteristic curve 2 with i, the negative effects associated with the S-characteristic are reduced.

The operation of the pump-turbine in the S-shaped characteristic portion also has an adverse effect on the torque T of the pump-turbine. When the value of N ₁ decreases in the S-shaped characteristic part, Fig. 1B
As shown in , the value of T ₁ decreases. Now again points a and h on the characteristic curve 1 shown in FIG.
is the point a' on the characteristic curve 1' shown in Figure 1B.
It must be noted that each corresponds to h′.

When the operating condition follows the S-shaped characteristic part in the direction of decreasing _T1 , the effective head H continues to rise as described above, and dH/dt>0, and a decrease in _T1 means a decrease in pump-turbine torque T. . Furthermore, the pump turbine torque T
It is clear that a decrease in N results in a decrease in the pump turbine rotational speed N. A decrease in the pump-turbine rotational speed N results in a corresponding decrease in N ₁ and then a further decrease in T ₁ . Meanwhile, as the effective head H is increasing as described above, this acceleration tendency becomes even stronger. In this way, while the pump-turbine follows the characteristic curve 1 in the direction of decreasing Q ₁ , it simultaneously traces the characteristic curve 1' from point a' to point h'. The way to trace this is the same as in the case of a positive feedback control circuit. After that, when the slope reverses at point h' after tracing the S-shaped characteristic part, a negative feedback or stabilizing effect is activated, and the direction of tracing is reversed at a point slightly past point h', and the characteristic curve 1' is moved to point h'. ′ in the direction of point a′. Obviously, torque variations as described above are disadvantageous.

Generally, when there is a load or break, the guide vanes are normally closed by the action of the speed governor of the pump turbine. The governor always operates the guide vanes in the direction of closing when the actual rotation speed is higher than the set rotation speed (usually the synchronous rotation speed of the generator), but in a pump-turbine with S-shaped characteristics, this normal If the guide vane is allowed to close, there is a risk that the S-shaped characteristic will be promoted.

Even if the load is on or off, the operating state of the pump-turbine does not fall into the S-shaped characteristic region until the number of revolutions per unit head (N ₁ ) reaches point a in Figure 1A. Operation in the S-characteristic section begins after a certain period of time has elapsed since the load was interrupted. It is desirable for the guide vanes to close rapidly during a period of time from the moment the load breaks to when the S-characteristic section is entered. This is because, due to this rapid closing operation, the characteristics of the pump-turbine shift to a direction that alleviates the adverse effects caused by the S-shaped characteristic portion. for example,
By closing the guide vanes (ie, reducing the opening of the guide vanes), the characteristics of the pump-turbine represented by characteristic curve 1 in FIG. 1A change to those represented by characteristic curve 2. This transition causes characteristic curve 2
has an S-shaped characteristic portion smaller than that of characteristic curve 1, so that the adverse effects of the problem are alleviated accordingly.

Next, it should be noted that rapid closing of the guide vanes should not be performed when the pump turbine is operated following the S-shaped characteristic section in the direction of Q ₁ decrease. This is because, due to rapid closing, the operating state runs diagonally from point b on characteristic curve 2 to point j on characteristic curve 3, and from a dynamic viewpoint, the slope of the characteristic curve (dQ ₁ / dN ₁ ) is strengthened, and the influence of the S-shaped characteristic appears more strongly. If the rapid confinement is performed while the S-shaped characteristic portion is being followed in the flow rate decreasing direction, the adverse effects of the S-shaped characteristic portion will be extremely severe.

By the way, as mentioned above, as long as the guide vane opening remains above a predetermined value, once the guide vane enters the S-characteristic part, it will almost permanently move through the S-characteristic part with a constant period.
Q ₁ After following the direction of decrease, immediately turn back to the direction of increase and then trace it back to the direction of decrease. In other words, for a pump-turbine, the opportunities to prevent the guide vanes from closing rapidly are not limited to a predetermined period of time after the load is cut off, but occur repeatedly. Therefore, it is necessary to prevent disadvantageous abnormal water pressure changes at all opportunities.

In order to reduce or avoid this abnormal water pressure fluctuation,
The present inventor has proposed that when the S-shaped characteristic portion is traced in the direction of decreasing flow rate or in the direction of decreasing torque, the guide vanes are opened from the current opening degree, and when the S-shaped characteristic portion is traced in the direction of increasing flow rate or torque. A technique for rapidly closing the guide vanes was proposed in Japanese Patent Applications 52-59213 and 59214.

However, if a power loss accident occurs while the guide vane is being opened by following the S-shaped characteristic portion in the direction of decreasing flow rate or decreasing torque, the pressure oil switching solenoid valve of the control device that opens and closes the guide vane will switch. However, the guide vane closes rapidly. For this reason, a problem arises in that abnormal water pressure fluctuations increase.

[Purpose of the invention]

The present invention was developed in view of the above circumstances, and reduces abnormal water pressure fluctuations even if a power loss accident occurs when the guide vane is opened by following the S-shaped characteristic portion in the direction of decreasing flow rate or decreasing torque. The purpose is to

[Summary of the invention]

That is, the feature of the present invention is that in the water turbine operating range, if the rotation speed per unit head of the pump turbine is N ₁ , the flow rate per unit head Q ₁ , and the generated torque per unit head T ₁ , then N ₁ = N/√, Q ₁ = Q/√, T ₁ = T/H (N, Q, T, and H indicate the rotation speed, flow rate, torque, and effective head of the pump-turbine). , the rotation speed N ₁ on the horizontal axis and the flow rate Q ₁ on the vertical axis
This is a characteristic curve diagram of a pump-turbine showing the relationship between rotational speed N ₁ , flow rate Q ₁ , and generated torque T 1 , which has an S-shaped characteristic in which the rotation speed N ₁ , flow rate Q 1 , and generated torque T ₁ all decrease, and the operating state of the pump-turbine is S-shaped. When the flow rate decreases or the torque decreases on the characteristics, the guide vanes are opened from the current opening, and when the pump turbine operation status follows the S-shaped characteristics in the flow rate increase direction or torque increase direction, the guide vanes are opened. In a control device for a pump-turbine configured to rapidly close the guide vane, there is a detection device that detects that the S-shaped characteristic is being followed in the direction of decreasing flow rate or decreasing direction of torque, and a signal detected by this detection device that opens the guide vane. a pressure oil switching solenoid valve to operate, and another pressure oil switching solenoid valve operating to gently close the guide vane when power to the pressure oil switching solenoid valve is lost while the guide vane is opening; The control system for pump water turbines consists of:

As can be understood from FIGS. 1A and 1B, when the pump-turbine is operated in the S-shaped characteristic section, ∂Q ₁ /∂N ₁ >0 and ∂T ₁ /
The relationship ∂N ₁ >0 is satisfied. When the S-shaped characteristic part is traced in the direction of decreasing Q ₁ , dN ₁ /
The relationships dt<0 and Q ₁ /dt<0 are satisfied. Here t is time. When dQ ₁ /dt<0, Q, that is, the amount of water flowing into the pump-turbine is decreasing, and as a result, the water pressure P at the lower end of the penstock (pump-turbine end) on the upstream side increases, and the relationship dP/dt>0. holds true. By the way, the inventor has clarified the behavior of a pump-turbine within the above-mentioned S-shaped characteristic, and based on this, has discovered several convenient methods for detecting a pump-turbine that produces an S-shaped characteristic part. In other words, it can be detected that the operating state of the pump-turbine is following the S-shaped characteristic part in the _Q1 decreasing direction by combining a rotation speed detector, a head detector, a flow rate detector, and a computer under the following three conditions. This can be done by detecting that at least one of the following conditions is satisfied.

(A) dN ₁ /dt<0 and dQ ₁ /dt<0 hold simultaneously.

(B) dN ₁ /dt<0 and dP/dt>0 hold simultaneously.

(C) dT ₁ /dt<0 and dN ₁ /dt<0 hold simultaneously.

In order to accurately detect that this pump-turbine S-shaped characteristic part is following the _Q1 decreasing direction, it is detected that any one of the above conditions A to C is satisfied.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. When the rotational speed of the pump-turbine increases due to load interruption, the control hydraulic pressure increases to 20% by the action of the speed governor.
The oil is drained and the relay turbo motor piston 17
is moved downward by pressure oil PO ₂ that is constantly applied to the upper side thereof, and stops at the position where the stopper 26 hits the servo motor closing time adjustment nuts 16-1 and 16-2. Then, the main pressure distribution valve plunger 18 which is directly connected to the relay turbo motor piston 17
The pressure oil PO 3 that is constantly applied to the main pressure distribution valve 19 is guided to the pipe 22, and the pressure oil PO ₃ is guided to the pipe 21.
is communicated with the drain oil pipe 23-2, so the piston 25 of the guide vane servo motor cylinder 24 is
It operates in the closing direction according to the closing speed defined by the closing time adjusting nuts 16-1 and 16-2.
After that, when it is detected by any of the methods of conditional expressions (A), (B), and (C) that the S-shaped characteristic is being followed in the flow rate decreasing direction, the contact 30 closes and the flow path of the pressure oil PO ₁ is switched. The electromagnet S1 of the solenoid valve 1 is energized, the piston 3 of the cylinder 4 shown in FIG. 2 moves upward, and the stopper 5
is pulled upward by lever 6. At this time, the rotational speed of the pump turbine is still far above the rated value, so the control pressure oil 20 remains drained.

As the stopper 5 is pulled up, the main pressure regulating valve plunger 18 also rises via the rod 13. Therefore, the pressure oil PO ₃ of the main pressure distribution valve 19 is guided to the pipe 21, and the pipe 22 is led to the drain oil pipe 23-1, so that the guide vane servo motor piston 25
moves in the opening direction at an opening speed defined by the upper limit position of the lever 6. Further, when the S-shaped characteristic begins to be followed in the direction of increasing flow rate, the contact point 30 opens, the electromagnet S1 of the solenoid valve 1 is deenergized, and the piston 3 moves downward. Therefore, the load will be in the same state as when it was disconnected, and the guide vane servo motor piston 25 will be
The closing time adjustment nuts 16-1 and 16-2
It moves in the closing direction with the closing speed defined by . At this time, since the rotational speed of the pump-turbine is still above the rated rotation, the control pressure oil 20 remains drained.

The electromagnet S2 of the solenoid valve 2 is configured so that it is always energized as long as the power supply is normal.
The piston 8 is always pushed down to the lower end. Lever 11 moved up and down by piston 8
is configured such that at its lower limit position it does not interfere with the operation of the stopper 10, that is, the operation of the main pressure regulating valve plunger 18. In addition, 7
is the fulcrum of lever 6, 12 is the fulcrum of lever 11, 1
4-1 and 14-2 are nuts for adjusting the opening time of the servo motor, 15-1 and 15-2 are stud bolts, P in FIG. 3 is a DC positive power supply, and N is a DC negative power supply, respectively.

In the above configuration, if the power supply is lost when the load is interrupted, especially when the guide vane is following an S-shaped characteristic in the direction of decreasing flow rate, which is not a time when the guide vane should be suddenly closed, the electromagnet S1 of the solenoid valve 1 is deenergized and the The path is switched, the piston 3 is pushed down, and the lever 6 is lowered.
Therefore, the opening operation of the guide vanes is no longer performed. However, since the electromagnet S2 of the solenoid valve 2 is also deenergized and the oil passage is switched, the piston 8 is pushed up and the lever 11 is moved upward. Therefore, the lever 11 is
3 and limits the amount of descent of the rod 13. Therefore, the amount of pressure oil PO ₃ from the main pressure regulating valve 19 flowing to the guide vane servo motor cylinder 24 through the pipe line 22 is restricted, so the piston 25 moves slowly in the closing direction.

〔Effect of the invention〕

According to the present invention, when the guide vanes are opened by following the S-shaped characteristic portion in the direction of decreasing flow rate or decreasing torque, even if an accident of power loss occurs, the guide vanes will not close rapidly. , it is possible to reduce abnormal water pressure fluctuations.

[Brief explanation of the drawing]

Fig. 1A and Fig. 1B are explanatory diagrams of the S-shaped characteristics peculiar to pump-turbine, Fig. 2 is a schematic diagram of a control device for realizing the present invention, and Fig. 3 is an electromagnet of the solenoid valve shown in Fig. 2. FIG. 1, 2... Solenoid valve, 3, 8... Piston, 6, 11
...Lever, 19...Main pressure distribution valve, 24...Guide vane servo motor cylinder, 30...Contact.

Claims (1)

[Claims] 1 In the water turbine operation range, if the number of rotations per unit head of the pump turbine is N ₁ , the flow rate per unit head Q ₁ , and the generated torque per unit head T ₁ , then N ₁ = N/√ , Q ₁ =Q/√, T ₁ =T/H
(However, N, Q, T, and H indicate the rotation speed, flow rate, torque, and effective head of the pump-turbine.) The horizontal axis represents the rotation speed N ₁ and the vertical axis represents the flow rate Q ₁ and generated torque. A characteristic curve diagram of a pump-turbine showing the relationship between T ₁ , rotation speed N ₁ , flow rate Q ₁ , and generated torque.
When the operating condition of the pump- _turbine follows the S-curve characteristic in the direction of decreasing flow rate or decreasing torque, the guide vanes are opened from the current opening degree, and the pump-turbine is In a pump-turbine control device configured to rapidly close the guide vanes when the operating state follows the S-shaped characteristic in the direction of increasing flow rate or increasing torque, the control device for a pump-turbine is configured to rapidly close the guide vanes when the operating state follows the S-shaped characteristic in the direction of decreasing flow rate or decreasing torque. a pressure oil switching solenoid valve that opens a guide vane based on a signal detected by the detection device; and a pressure oil switching solenoid valve that opens the guide vane when power is lost to the pressure oil switching solenoid valve while the guide vane is opening. A control device for a pump water turbine, comprising a pressure oil switching solenoid valve different from the one described above, which acts to gently close a guide vane.