JPH0326281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the oil level of a pressure oil tank, particularly a pressure oil tank for a pressure oil equipment in a hydroelectric power plant.

[Prior Art] In a hydroelectric power plant, a pressure oil tank and an air replenishment device that supplies compressed air to the pressure oil tank are used to control the hydraulic servo motor that operates the guide vanes or inlet valves for adjusting the water volume of the water turbine. is provided. Figure 1 shows the general system.
1 is a pressure oil tank, 2 is an air supply oil level detector, 3 is a pressure switch, 4 is an air compressor, 5 is an air tank,
Reference numeral 6 indicates an air supply solenoid valve, and reference numeral 7 indicates an air release valve.

The oil level in the pressure oil tank 1 is the oil level L2 at the lowest normal oil pressure.
and the oil level L1 at the highest normal oil pressure. The relationship between the oil pressure and the oil level in the pressure oil tank 1 is P×V ⁿ = constant...(1) where P is the pressure, V is the volume of air, and n is the oil pressure with the polytropic index relationship maintained.・The oil level is changing.

However, if the air in the pressure oil tank 1 dissolves into the oil or leaks outside the pressure oil tank 1 and the amount of air in the pressure oil tank 1 decreases, the pressure oil tank 1, which has the relationship of equation (1), The oil pressure and oil level in the pressure oil tank 1 become unbalanced, and the oil level in the pressure oil tank 1 rises by an amount corresponding to the amount of air that has decreased. Therefore, it is necessary to supply the insufficient amount of air into the pressure oil tank 1 to return the oil level in the pressure oil tank 1 to the reference oil level position.

Conventional hydraulic pressure by supplying air in the pressure oil tank 1
In the oil level control method, the oil level L at the maximum normal oil pressure is
1, when the oil level rose by ΔL and reached the air replenishment oil level L0, while the oil pressure and oil level changed due to consumption of pressure oil, for example, the oil level L2 at the lowest normal oil pressure. From the allowable minimum oil pressure oil level L3
Even if an abnormality occurs, such as an air leak inside the pressure oil tank 1 or air intrusion from the outside,
It was not possible to detect abnormalities in the oil pressure and oil level and to control air supply, and it was not possible to always ensure a stable relationship between the oil pressure and oil level in the pressure oil tank 1. In addition, if the compressed air from the air tank 5 enters the pressure oil tank 1 in an excessive amount due to some abnormality and the excess air is to be released, the air release valve 7 is manually opened to release the air to the outside. The method used was to control the oil level in the pressure oil tank 1 by releasing the oil into the tank.

Figure 2 shows the electrical sequence for conventional air replenishment.
2 is an air replenishment oil level detector; 3 is a pressure switch that opens when the pressure in the pressure tank 1 rises to the level equivalent to L0 oil level under normal conditions; 6 is an air replenishment solenoid valve; 8 is a timer for setting air replenishment time; 9 indicates an auxiliary relay. When the air in the pressure oil tank 1 decreases and the oil level rises and reaches the air replenishment oil level L0, the air replenishment oil level detector 2 is closed and the pressure switch 3 is closed. The air replenishment time setting timer 8 is activated, the auxiliary relay 9 is energized, the air replenishment solenoid valve 6 is energized, and the compressed air stored in the air tank 5 shown in FIG. 1 is transferred to the pressure oil tank 1. supply air to The air replenishment time setting timer 8 sets in advance the time required for replenishing the pressure oil tank 1 from the air tank 5 with the amount of air necessary to return the oil level from the air replenishment oil level L0 to the normal maximum oil level L1. Air is only supplied during that time.

On the other hand, when stopping air replenishment, air replenishment is performed when any of the following conditions is met: the air replenishment time setting timer 8 returns, the air replenishment oil level detector 2 opens, or the pressure switch 3 opens. The solenoid valve 6 is deenergized and the air supply to the pressure oil tank 1 is stopped.

[Problem to be solved by the invention]

As mentioned above, the conventional method for controlling the oil level of the pressure oil tank 1 is such that the oil level of the pressure oil tank 1 deviates from the oil level L1 at normal maximum oil pressure to the oil level L2 at normal minimum oil pressure, and reaches the air supply oil level L0. Since the correction is performed by treating the oil level as abnormal only when the oil level rises, air leakage or intrusion may occur within the normal operating range of oil level L2 at normal minimum oil pressure to oil level L3 at allowable minimum oil pressure. When such an abnormality occurs, there is a drawback that it is not possible to detect the abnormality in the oil level and control the oil level.

The present invention eliminates these drawbacks and maintains the oil pressure and oil level in the pressure oil tank in a stable state over the entire operating range, providing safe and reliable oil level control in the pressure oil tank. The purpose is to provide a method.

[Means to solve the problem]

The present invention is a method for controlling the oil pressure and oil level of a pressure oil tank in a power plant based on polytropic change characteristics, based on the detection results of oil pressure, oil level, and ^temperature . and P is pressure,
The allowable range is set as a function value of the oil pressure and oil level in the pressure oil tank, which is determined from the polytropic change characteristic where V is the volume of air and n is the polytropic index. Second, P x V = R x T (here Considering the temperature characteristics obtained from the ideal gas equation of state where P is the pressure, V is the volume of the air, R is the gas constant of the air, and T is the absolute temperature, the function value of the above-mentioned oil pressure and oil level with respect to temperature change is calculated. After correcting the permissible range of This system is characterized by air supply or surplus air release to quickly return the oil pressure, oil level, and temperature to normal ranges.

[Effect]

In the oil level control method for a pressure oil tank of the present invention, based on the detection results of oil pressure, oil level, and temperature, first
V ⁿ = constant (where P is pressure, V is volume of air,
The allowable range is set as a function value of the oil pressure and oil level in the pressure oil tank, which is determined from the polytropic change characteristic (n is a polytropic index), and secondly, P×V=R×
Considering the temperature characteristics obtained from the ideal gas equation of state T (where P is pressure, V is the volume of air, R is the gas constant of air, and T is absolute temperature), the above-mentioned hydraulic pressure and oil level against temperature changes are calculated. Since the allowable range is corrected as a function value, the allowable range can be determined using the relationship between oil pressure and oil level in consideration of temperature characteristics as a function value. Therefore, this function value is compared with, for example, continuously detected oil pressure, oil level, and temperature to detect abnormalities related to the oil pressure and oil level in the pressure oil tank. Abnormalities can be quickly detected in all areas of oil level changes. Based on this detection result, air is supplied or surplus air is released to return the oil pressure, oil level, and temperature to the normal range, so the oil pressure and oil level in the pressure oil tank are always stable throughout the operating range. can maintain the condition,
Safe and reliable oil level control in pressure oil tanks becomes possible.

〔Example〕

Examples will be described below.

FIG. 3 shows a schematic system of one embodiment, and FIG. 4 shows an electrical sequence for air supply. The same parts as in FIGS. 1 and 2 are given the same reference numerals. In these figures, 10 is a temperature sensor, 11 is an oil level sensor, 12 is a pressure sensor, 13 is an arithmetic control unit, 14 is an air release solenoid valve, 15 is an air supply digital contact, and 16 is an air release digital contact. There is.

Figure 5 is an explanatory diagram of the algorithm for the normal region of a pressure oil tank, where the horizontal and vertical axes represent oil pressure P and oil level H, respectively, and Y is the ideal oil pressure/oil level characteristic curve,
Y ₁ is the curve of the upper limit value of the oil pressure/oil level characteristics used as the judgment criterion, Y ₂ is the curve of the lower limit value of the oil pressure/oil level characteristic used as the judgment criterion, H _N and P _N are the detected values of the oil level and oil pressure, respectively. , P _nax is the hydraulic pressure at oil level H _N.
The upper limit value of the oil level characteristics, P _nio , indicates the lower limit value of the oil pressure/oil level characteristics when the oil level is H _N , and L indicates the allowable range. In other words, Figure 5 shows the oil pressure/oil level algorithm characteristics in which the upper limit value Y ₁ and lower limit value Y ₂ of the oil level are determined as a function value of the oil level and the oil pressure, which is a change in air amount converted to an oil level. .

Therefore, in the pressure oil tank 1 of this embodiment, the state inside the pressure oil tank 1 is detected by the temperature sensor 10,
The oil level sensor 11 and the pressure sensor 12 constantly detect continuous quantities, which are input into the arithmetic and control unit 13, and the detected values are compared with the algorithm characteristics of oil pressure and oil level shown in Fig. 4, and the detected values are determined to be within the allowable range ( Y ₁ to _{Y 2} ), the abnormal state is corrected by supplying or discharging air until the position is near the ideal curve Y within the allowable range L, and the control is performed to return to the normal position.

The algorithm characteristic range shown in Figure 4 is as shown in equation (1) when the oil pressure in the pressure oil tank is P and the amount of air is V, P x V ⁿ = constant...(1)' Here, n is a polytope. It is an index that changes depending on the change in air temperature in the pressure oil tank, and generally,
It is known that n=1.0 to 1.4.

It is determined according to the polytropic change characteristics.

On the other hand, there is a relationship between the oil pressure P in the pressure oil tank, the amount of air V, the absolute temperature T, and the gas constant R of air as shown in the equation of state for an ideal gas: P x V = R x T (2), From this ideal gas state equation, the initial values of oil pressure, oil level, and temperature are respectively P ₁ , V ₁ , and T ₁ , and the changed oil pressure, oil level, and temperature are P ₂ , respectively.
Assuming V ₂ and T ₂ , P ₁ ×V ₁ /T ₁ =P ₂ ×V ₂ /T ₂ (3).

Here, since there is a relationship between absolute temperature T and degree Celsius temperature t as T = 273 + t...(4), the amount of increase or decrease in temperature can be expressed as Δt
Then, the temperature T ₂ after the change is T ₂ =273+t+Δt (5).

Therefore, assuming that the amount of air is constant, the pressure change due to temperature change is P ₁ /273+t=P ₂ /273+t+Δt (6) P ₂ =P ₁ {1+Δt/273+t} (7).

Figure 6 shows the algorithm for the normal region that has been modified based on temperature changes in the pressure oil tank.
It moves in parallel to monitor the condition inside the pressure oil tank. In FIG. 6, the same parts as in FIG. 5 are given the same reference numerals. In this figure, Y′ is the temperature Δt
Ideal oil pressure/oil level characteristic curve after change, Y ₁ ′ is temperature Δt
The curve of the upper limit value of the oil pressure/oil level characteristic used as the criterion after the change in temperature, Y ₂ ′ is the curve of the lower limit value of the oil pressure/oil level characteristic used as the criterion after the change in temperature Δt, H′ _N and P′ _N are Detected values of oil level and oil pressure after temperature Δt change, respectively,
P′ _nax is the upper limit of the oil pressure and oil level characteristics when the oil level is H′ _N , P′ _nio is the lower limit of the oil pressure and oil surface characteristics when the oil level is H′ _N , L is the allowable range under the initial conditions, and L′ is an allowable range after a change in temperature Δt, and M is a pressure correction due to a change in temperature Δt.

In other words, the allowable range Y ₁ to _{Y 2} in the initial state is corrected to the normal range due to the temperature change (Δt) during operation, and becomes Y ₁ ′ to _{Y 2} ′, and the relationship between the pressure oil level in the pressure tank is always adjusted based on the oil level. A normal relationship can be maintained over the entire range of surface and oil pressure changes.

In the pressure oil tank 1 of the embodiment, the oil pressure/oil level characteristics expressed as a function of temperature as shown in FIG. The signals from the sensor 10, oil level sensor 11, and pressure sensor 12 are compared with the algorithm characteristics of the normal region described above, and the relationship between the oil pressure and oil level in the pressure oil tank 1 at that time is determined at point A in FIG. , this is not acceptable, so
Immediately detects an abnormality (lack of air), the air supply digital contact 15 is energized by the arithmetic and control unit 13, the air supply solenoid valve 6 is energized, and air is supplied from the air tank 5 to the pressure oil tank 1. Oil level control is performed by increasing the internal pressure of the pressure oil tank 1 and correcting the abnormal condition at point A to near point C on the ideal oil pressure/oil level characteristic curve Y within the normal range. In addition, when the state inside the pressure oil tank 1 is at point B in FIG. The solenoid valve 14 is energized to release excess air in the pressure oil tank 1, lowering the pressure in the pressure oil tank 1, and changing the abnormal state at point B to C on the ideal oil pressure/oil level characteristic curve within the normal range. Oil level control is performed by making corrections to the vicinity of the point.

Next, we will show an example of creating an abnormality diagnosis monitoring algorithm that takes temperature correction into consideration for a pressure oil tank in a hydroelectric power plant. The amounts are respectively at hydraulic pressure of 47Kg/ ^cm2.
2200Lit and 1400Lit, and the maximum oil level for regular use is 50
Kg/cm ² , minimum normal oil level is 47Kg/cm ² , upper limit alarm oil pressure/oil level is 52Kg/cm ² , lower limit alarm oil pressure/oil level is
42.5Kg/cm ² , and in this case, the upper limit alarm oil pressure/oil level is set at a position approximately 10 to 20 mm above the air supply oil level L0, and the lower limit alarm oil pressure/oil level is set to the minimum normal oil pressure/oil level L2. It was set at a position midway between the lowest oil pressure and oil level L3.

The abnormality diagnosis algorithm for this pressure oil tank is created for the range from the upper limit alarm oil pressure/oil level to the lower limit alarm oil pressure/oil level, and when the oil pressure/oil level is outside this range, the presence or absence of the abnormality diagnosis monitoring algorithm is checked. First, everything is detected as abnormal.

In this way, in the pressure oil tank of the example,
It has become possible to continuously detect the oil pressure, oil level, and temperature in the pressure oil tank, and to perform air replenishment or release control by monitoring according to the change characteristics of the oil pressure and oil level, taking temperature changes into consideration. The oil pressure and oil level in the oil tank can always be maintained in a stable state over the entire operating range, providing safe and reliable oil level control in the pressure oil tank for pressure oil equipment.

〔Effect of the invention〕

The present invention can always maintain the oil pressure and oil level in the pressure oil tank in a stable state over the entire operating range.
A safe and reliable oil level control method for a pressure oil tank can be provided.

[Brief explanation of drawings]

Fig. 1 is a conventional pressure oil tank oil level control system diagram, Fig. 2 is an oil level control electrical sequence diagram, and Fig. 3 is used in an embodiment of the oil level control method for a pressure oil tank of the present invention. Pressure oil tank oil level control system diagram, Figure 4 is also an oil level control electrical sequence diagram, Figure 5 is also an algorithm explanatory diagram of the normal range of oil pressure and oil level of the pressure oil tank, and Figure 6 is also the same temperature characteristic. It is an explanatory diagram of the algorithm of the oil pressure and oil level of the pressure oil tank taken into consideration. 1...Pressure oil tank, 4...Air compressor, 5...
Air tank, 6...Air supply solenoid valve, 14...Air release solenoid valve, 15...Air supply digital contact,
16...Air release digital contact.

Claims (1)

[Claims] 1 In a method of controlling the oil pressure and oil level of a pressure oil tank in a hydroelectric power plant based on polytropic change characteristics, firstly, P×V ⁿ = constant (here, P is pressure, V
is the volume of air and n is the polytropic exponent). Set the allowable range as a function value of the oil pressure and oil level in the pressure oil tank, and then set the tolerance range as a function value of the oil pressure and oil level in the pressure oil tank. P is the pressure, V is the volume of the air, R is the gas constant of the air, and T is the absolute temperature. The permissible range is corrected, and abnormalities in the oil pressure and oil level in the pressure oil tank are detected using the obtained function values as judgment criteria, and based on the results, the entire range of oil pressure and oil level changes in the pressure oil tank is detected. A method for controlling an oil level in a pressure oil tank, characterized by supplying air or releasing excess air so as to quickly return oil pressure, oil level, and temperature to normal ranges.