Oil level measurement method and device for oil storage tank

Abstract

The present invention relates to the field of transformer technology, and in particular to a method and device for measuring the oil level of an oil conservator. The measuring method comprises: first obtaining the temperature and oil pressure of the transformer oil through a sensor; then correcting the temperature according to the ambient temperature and a correction coefficient to obtain a corrected temperature, wherein the correction coefficient is determined according to the installation position of the temperature sensor; then determining the density of the transformer oil according to the corrected temperature; and finally determining the oil level of the transformer oil according to the oil pressure and density of the transformer oil. The temperature is corrected by determining the correction coefficient based on the installation position of the temperature sensor, ensuring that the corrected temperature can accurately reflect the temperature of the transformer oil in the oil conservator, thereby ensuring that the oil level calculated by the corrected temperature is the actual oil level, and realizing accurate monitoring of the oil level of the oil conservator.

Description

Technical Field

[0001] The invention relates to the technical field of transformers, and in particular to an oil level measurement method and device for an oil storage cabinet. Background Art

[0002] The large-scale power transformers in operation are mainly oil-immersed transformers. The transformer oil plays an insulating and cooling role during the operation of the transformer. If the transformer oil level is too high, it may cause excessive pressure in the oil tank at high temperature or heavy load, causing oil overflow or pressure relief valve action; if the transformer oil level is too low, the high-voltage part may lose the protection of oil and be exposed, causing breakdown, discharge or transformer damage; in addition, the transformer oil level can also reflect the sealing condition of the oil tank, which is convenient for timely detection of oil seepage or oil leakage. Therefore, timely and accurate monitoring of the transformer oil level is very important for the safe operation of the transformer.

[0003] The transformer oil level gauge is a device that indicates the oil level in the oil conservator. With the development of sensor technology and the development requirements of smart grids, digital transformer oil level gauges that collect oil pressure and oil temperature to measure the oil level in the oil conservator have emerged. The sensor is installed at any position of the oil conservator or oil tank, and the oil level of the oil conservator is calculated by combining the collected oil temperature and oil pressure, and then the oil level is converted into the indication value of the transformer oil level gauge. The existing oil level measurement methods of digital transformer oil level gauges do not consider temperature compensation, resulting in a large error between the calculated oil level and the actual oil level, making it impossible to accurately monitor the oil level of the oil conservator, posing a safety hazard to the operation of the transformer. Summary of the invention

[0004] The present invention provides an oil level calculation method for an oil conservator, which is used to solve the technical problem that the oil level calculation method for an oil conservator in the prior art does not consider temperature compensation, resulting in failure to accurately monitor the oil level of the oil conservator.

[0005] A first aspect of the present invention provides a method for calculating the oil level of an oil storage tank, comprising:

[0006] Get transformer oil temperature and oil pressure;

[0007] The temperature is corrected according to the ambient temperature and a correction coefficient to obtain a corrected temperature, wherein the correction coefficient is determined according to the installation position of the temperature sensor;

[0008] determining the density of the transformer oil according to the corrected temperature;

[0009] The oil level of the transformer oil is determined based on the oil pressure and the density.

[0010] In a first possible implementation method of the first aspect, the correction coefficient is proportional to the distance of the temperature sensor relative to the oil storage tank.

[0011] In a second possible implementation method of the first aspect, the correction temperature T1=T0-k(T0-T2), wherein: T0 is the temperature of the transformer oil, T2 is the ambient temperature, and k is the correction coefficient;

[0012] If the temperature sensor is installed in the oil storage tank, k=0.

[0013] In a third possible implementation method of the first aspect, after determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes:

[0014] Calculate the per unit height of the oil level in the oil storage tank;

[0015] Calculate the rotation angle of the oil level gauge according to the per unit value of the height;

[0016] The indicated value of the oil level gauge is calculated according to the rotation angle.

[0017] In a fourth possible implementation method of the first aspect, after determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes:

[0018] Calculate the oil volume ratio of the oil conservator based on the oil level;

[0019] The oil volume of the oil storage tank is calculated according to the oil volume ratio.

[0020] In a fifth possible implementation method of the first aspect, after determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes:

[0021] Calculate the pressure exerted by the bellows expander on the transformer oil;

[0022] The oil level is corrected according to the pressure, the density and the oil pressure to obtain a corrected oil level, and the oil pressure is the oil pressure at the bottom of the internal oil vertical corrugated oil storage tank.

[0023] In combination with the fifth possible implementation method of the first aspect, in a sixth possible implementation method, the corrected oil level H1=(PS+KH0+ρgSH2) / (ρgS+K), wherein: P is the oil pressure, S is the top cover area of ​​the bellows expander, K is the elastic coefficient of the bellows expander, H0 is the height of the bellows expander in a free state, H2 is the height of the pressure sensor relative to the bottom of the oil storage tank, ρ is the density, and g is the acceleration of gravity.

[0024] In combination with the fifth possible implementation method of the first aspect, in a seventh possible implementation method, after the oil level is corrected according to the pressure, the density and the oil pressure, the method further includes:

[0025] The corrected oil level is compared with a low oil level threshold and a high oil level threshold respectively;

[0026] If the corrected oil level is less than the low oil level threshold or greater than the high oil level threshold, an alarm signal is issued.

[0027] A second aspect of the present invention provides an oil level measuring device for an oil storage tank, comprising: a pressure sensor, a temperature sensor, a conversion module and a data processing module;

[0028] The pressure sensor is used to obtain the oil pressure of the transformer oil;

[0029] The temperature sensor is used to obtain the temperature of the transformer oil and the ambient temperature;

[0030] The conversion module is used to convert the current signal or voltage signal of the sensor into a digital quantity, and output the digital quantity to the data processing module;

[0031] The data processing module is used to process the digital quantity and output the oil level;

[0032] The pressure sensor and the temperature sensor are connected to the data processing module through the conversion module.

[0033] In a first possible implementation of the second aspect, the device further includes: a communication module, a storage module and a human-computer interaction module connected to the data processing module;

[0034] The communication module is used to exchange information with the communication management machine;

[0035] The storage module is used to store the oil pressure and the temperature;

[0036] The human-computer interaction module is used to input instructions.

[0037] It can be seen from the above technical solutions that the present invention has the following advantages:

[0038] The oil level measurement method of the oil storage tank provided by the present invention first obtains the temperature and oil pressure of the transformer oil through a sensor; then corrects the temperature according to the ambient temperature and the correction coefficient to obtain the corrected temperature, wherein the correction coefficient is determined according to the installation position of the temperature sensor; then determines the density of the transformer oil according to the corrected temperature; and finally determines the oil level of the transformer oil according to the oil pressure and density of the transformer oil. The correction coefficient is determined based on the installation position of the temperature sensor to correct the temperature, ensuring that the corrected temperature can accurately reflect the temperature of the transformer oil in the oil storage tank, thereby ensuring that the oil level calculated by the corrected temperature is the actual oil level, and realizing accurate monitoring of the oil level of the oil storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 A schematic diagram of a flow chart of a method for calculating the oil level of an oil storage tank shown in an embodiment of the present application;

[0041] Figure 2 Another schematic diagram of a flow chart of a method for calculating the oil level of an oil storage tank shown in an embodiment of the present application;

[0042] Figure 3 Another schematic diagram of a flow chart of a method for calculating the oil level of an oil storage tank shown in an embodiment of the present application;

[0043] Figure 4 This is a structural schematic diagram of an oil level measuring device for an oil storage cabinet shown in an embodiment of the present application. DETAILED DESCRIPTION

[0044] The embodiment of the present invention provides an oil level calculation method for an oil conservator, which is used to solve the technical problem that the oil level calculation method for an oil conservator in the prior art does not consider temperature compensation, resulting in failure to accurately monitor the oil level of the oil conservator.

[0045] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The oil conservator, commonly known as the oil pillow, is installed above the transformer oil tank and connected to the transformer oil tank with a pipe. When the transformer oil expands due to heat, the transformer oil flows from the transformer oil tank to the oil conservator. When the transformer oil contracts due to cold, the transformer oil flows from the oil conservator to the oil tank. It is equivalent to a buffer, which ensures that the transformer oil tank is always filled with transformer oil. Since the oil in the oil tank is always full, the oil level of the transformer is reflected by the oil level of the oil conservator. The digital transformer oil level gauge is a device that collects the temperature and oil pressure of the transformer oil through a temperature sensor and a pressure sensor to calculate the oil level of the oil conservator. However, the transformer oil in different locations has different temperatures. For example, there is a large difference in the temperature of the transformer oil in the pipeline, oil tank and oil conservator. If you want to ensure that the calculated oil level of the oil conservator is the actual oil level of the oil conservator, you need to ensure that the temperature of the transformer oil used for calculation is the temperature of the transformer oil in the oil conservator. However, existing digital transformer oil level gauges mostly use the transformer oil temperature at any position to calculate the oil level of the oil conservator, which may result in a large error between the measured oil level and the actual oil level, making it impossible to accurately monitor the oil level of the oil conservator, posing certain safety hazards to the operation of the transformer.

[0047] Embodiment 1

[0048] See also Figure 1 , Figure 1 A schematic flow chart of a method for calculating the oil level in an oil storage cabinet provided in an embodiment of the present invention.

[0049] This embodiment provides a method for calculating the oil level of an oil storage tank, including:

[0050] 101. Obtain the temperature and oil pressure of transformer oil;

[0051] In this embodiment, a temperature sensor is installed at any position of the transformer covered by the transformer oil to collect the temperature of the transformer oil; because the oil level of the oil conservator needs to be calculated by the liquid pressure formula, it is necessary to ensure that the collected pressure corresponds to the actual oil level of the oil conservator, so a pressure sensor is set at the bottom of the oil conservator to collect the oil pressure of the transformer oil.

[0052] 102. Correct the temperature according to the ambient temperature and a correction coefficient to obtain a corrected temperature, wherein the correction coefficient is determined according to an installation position of the temperature sensor;

[0053] Heat will be transferred from a high temperature place to a low temperature place. Since the transformer oil will be in direct contact with the transformer oil tank, pipeline and oil storage cabinet, and the transformer oil tank, pipeline and oil storage cabinet are in contact with the external environment, the temperature of the transformer oil is affected by the temperature of the transformer oil tank, pipeline and oil storage cabinet and the external environment at the same time. Therefore, the ambient temperature can refer to the temperature of the transformer oil tank, the temperature of the pipeline, the temperature of the oil storage cabinet, the temperature of the external environment or the average value of the four temperatures. It can be seen that the temperature of the transformer oil is a dynamically changing quantity during the flow process. In this embodiment, since the temperature of the external environment has the greatest impact on the temperature of the transformer oil, the external environment temperature is used as the ambient temperature; the correction coefficient is an empirical value, which can be understood as a difference degree, that is, the difference degree between the temperature of the transformer oil at any position of the transformer and the temperature of the transformer oil in the oil storage cabinet; the temperature is corrected, that is, the temperature of the transformer oil in the oil storage cabinet is calculated by combining the transformer oil temperature collected by the temperature sensor with the correction coefficient and the ambient temperature.

[0054] 103. Determine the density of the transformer oil according to the corrected temperature;

[0055] In this embodiment, since the density of the transformer oil at 0° C. and the thermal expansion coefficient of the transformer oil are known, and the temperature of the transformer oil in the oil conservator, i.e., the corrected temperature, has been determined according to step 102, the density of the transformer oil in the oil conservator can be calculated.

[0056] 104. Determine the oil level of the transformer oil according to the oil pressure and the density;

[0057] In this embodiment, the oil pressure at the bottom of the oil conservator and the density of the transformer oil in the oil conservator are known, and the depth of the transformer oil corresponding to the oil pressure, i.e., the oil level, can be calculated according to the liquid pressure formula.

[0058] Beneficial effects of this embodiment: The oil level measurement method of the oil conservator provided by this embodiment first obtains the temperature and oil pressure of the transformer oil through the sensor; then corrects the temperature according to the ambient temperature and the correction coefficient to obtain the corrected temperature, wherein the correction coefficient is determined according to the installation position of the temperature sensor; then determines the density of the transformer oil according to the corrected temperature; and finally determines the oil level of the transformer oil according to the oil pressure and density of the transformer oil. The correction coefficient is determined based on the installation position of the temperature sensor to correct the temperature, ensuring that the corrected temperature can accurately reflect the temperature of the transformer oil in the oil conservator, thereby ensuring that the oil level calculated by the corrected temperature is the actual oil level, and realizing accurate monitoring of the oil level of the oil conservator.

[0059] Embodiment 2

[0060] In order to cater to the usage habits of the operation and maintenance personnel, the oil level of the oil conservator measured by the digital transformer oil level gauge needs to be presented by a pointer oil level gauge, and the oil volume ratio and oil volume of the oil conservator need to be calculated at the same time, so that the operation personnel can better monitor the operation status of the transformer. Therefore, in this embodiment, the digital transformer oil level gauge and the pointer oil level gauge are fitted, and the oil volume ratio and oil volume of the oil conservator are calculated.

[0061] See also Figure 2 , Figure 2 Another schematic diagram of a flow chart of a method for calculating the oil level of an oil storage cabinet provided by an embodiment of the present invention.

[0062] This embodiment provides a method for calculating the oil level of an oil storage tank, including:

[0063] 201. Obtain the temperature and oil pressure of the transformer oil;

[0064] In this embodiment, the specific content of step 201 is similar to that of step 101 in the above-mentioned embodiment 1, and is not described in detail here.

[0065] 202. Correct the temperature according to the ambient temperature and the correction coefficient to obtain a corrected temperature;

[0066] The farther the temperature sensor is from the oil conservator, the greater the difference between the transformer oil temperature collected by it and the transformer oil temperature in the oil conservator. Because the distance is far, the longer the distance and the time taken by the transformer oil to flow from the location to the oil conservator, the more heat will flow out of the transformer oil or flow into the transformer oil from the environment. Therefore, the correction coefficient is proportional to the distance of the temperature sensor relative to the oil conservator. The distance of the temperature sensor relative to the oil conservator should be understood as: the length of the path through which the transformer oil flows from the location of the temperature sensor to the flow into the oil conservator. For example, the correction coefficient corresponding to the oil tank is greater than the correction coefficient corresponding to the pipeline. In this embodiment, the correction temperature T1 = T0-k (T0-T2), where: T0 is the temperature of the transformer oil collected by the temperature sensor, T2 is the ambient temperature, that is, the external environment temperature, and k is the correction coefficient. It should be noted that: if the temperature sensor is installed in the oil conservator, T1 = T0, that is, the correction coefficient k = 0.

[0067] 203. Determine the density of the transformer oil according to the corrected temperature;

[0068] In this embodiment, the density of the transformer oil in the oil conservator is ρ=ρ0 / (1+αT1), where ρ0 is the density of the transformer oil at 0°C, α is the thermal expansion coefficient of the transformer oil, and T1 is the correction temperature.

[0069] 204. Determine the oil level of the transformer oil according to the oil pressure and the density;

[0070] Because liquid pressure = liquid density * weight acceleration * liquid depth, in this example, the transformer oil level H of the oil conservator is H = P / ρg + H2, where P is the pressure collected by the pressure sensor, ρ is the density of the transformer oil in the oil conservator, g is the weight acceleration, and H2 is the height of the pressure sensor relative to the bottom of the oil conservator. In this embodiment, the pressure sensor is installed at the bottom of the oil conservator, so H2 = 0.

[0071] 205. Calculate the per unit height value of the oil level in the oil storage tank;

[0072] The per unit value is a relative unit system. The per unit value is a numerical notation method commonly used in power system analysis and engineering calculations. It represents the relative value of each physical quantity and parameter. The unit is pu, which can also be considered dimensionless. In this embodiment, the oil conservator is a cylindrical container, which is placed horizontally above the transformer oil tank. The per unit value of the height of the oil level in the oil conservator is h=H / D, where: H is the transformer oil level of the oil conservator, and D is the inner diameter of the oil conservator.

[0073] 206. Calculate the indicated value of the oil level gauge according to the per unit value of the height;

[0074] In this embodiment, the rotation angle θ of the float connecting rod of the pointer oil level gauge is first calculated according to the per-unit value of the height, θ=arcsin(h.sin(θmax)), wherein: θmax is the maximum rotation angle of the float connecting rod of the pointer oil level gauge, and h is the per-unit value of the height of the oil level in the oil storage tank; then the indicated value a of the pointer oil level gauge is calculated according to the rotation angle, a=θ*A / θmax, wherein A is the maximum range of the pointer oil level gauge. According to the industry standard of the oil level gauge, the maximum rotation angle of the float connecting rod of the domestic oil level gauge is 45°, and the maximum rotation angle of the float connecting rod of the foreign oil level gauge is 60°.

[0075] 207. Calculate the oil volume ratio of the oil storage tank according to the oil level;

[0076] The oil volume ratio is the ratio of the transformer oil in the oil conservator to the volume of the oil conservator. In this embodiment, the inner diameter of the oil conservator is D, the inner radius is d, and the oil volume ratio s of the oil conservator is equal to the ratio of the area of ​​the transformer oil on the vertical cross section of the oil conservator to the vertical cross section area of ​​the oil conservator. Therefore, when the transformer oil level H of the oil conservator is less than d, the calculation method of the oil volume ratio s of the oil conservator is as follows:

[0077]

[0078] When the transformer oil level H in the oil conservator is greater than d, the calculation method of the oil volume ratio s in the oil conservator is as follows:

[0079]

[0080] 208. Calculate the oil volume of the oil storage tank according to the oil volume ratio;

[0081] The oil volume is the volume of transformer oil in the oil conservator. In this embodiment, the volume of the oil conservator is V = πd 2 L, where d is the inner radius of the oil conservator, L is the length of the oil conservator, and the oil volume of the oil conservator can be obtained by multiplying the oil volume ratio of the oil conservator by the volume of the oil conservator, that is, the oil volume of the oil conservator V1 = sV = sπd 2 L, where s is the oil volume ratio of the oil storage tank.

[0082] Beneficial effects of this embodiment: This embodiment converts the measured oil level into the indication value of a pointer-type oil level gauge, and simultaneously measures the oil ratio and oil volume in the oil storage cabinet, which caters to the habits of operation and maintenance personnel, and provides multiple monitoring data, which can monitor the transformer oil level more accurately.

[0083] Embodiment 3

[0084] Because the corrugated expander of the internal oil vertical corrugated oil conservator will produce a certain force on the transformer oil, the pressure collected by the pressure sensor installed at the bottom of the internal oil vertical corrugated oil conservator, in addition to the pressure of the transformer oil itself, also includes a part of the pressure applied to the transformer oil by the corrugated expander. Therefore, if it is an internal oil vertical corrugated oil conservator, the measured oil level needs to be corrected. In this embodiment, the oil level correction process is described.

[0085] See also Figure 3 , Figure 3 Another schematic diagram of a flow chart of a method for calculating the oil level of an oil storage cabinet provided by an embodiment of the present invention.

[0086] This embodiment provides a method for calculating the oil level of an oil storage tank, including:

[0087] 301. Obtain the temperature and oil pressure of the transformer oil;

[0088] In this embodiment, the specific content of step 301 is similar to that of step 101 in the above-mentioned embodiment 1, and is not described in detail here.

[0089] 302. Correct the temperature according to the ambient temperature and the correction coefficient to obtain a corrected temperature;

[0090] In this embodiment, the specific content of step 302 is similar to the content of step 202 in the above-mentioned embodiment 2, and is not described in detail here.

[0091] 303. Determine the density of the transformer oil according to the corrected temperature;

[0092] In this embodiment, the specific content of step 303 is similar to that of step 203 in the above-mentioned second embodiment, and will not be described in detail here.

[0093] 304. Determine the oil level of the transformer oil according to the oil pressure and the density;

[0094] In this embodiment, the specific content of step 304 is similar to that of step 204 in the above-mentioned second embodiment, and will not be described in detail here.

[0095] 305. Calculate the pressure exerted by the corrugated expander on the transformer oil;

[0096] In the vertical corrugated oil storage cabinet with internal oil, the top cover of the corrugated expander and the elastic force generated by the elastic deformation of the corrugated expander will directly act on the transformer oil - when the corrugated expander is in a stretched state, the top cover of the corrugated sensor will be subjected to a downward elastic force, and this part of the elastic force directly acts on the transformer oil through the top cover, exerting a downward force on the transformer oil, and the pressure sensor at the bottom of the oil storage cabinet will collect the downward force; when the corrugated expander is in a compressed state, the top cover of the corrugated sensor will be subjected to an upward elastic force, because the corrugated expander is in a vacuum state, and the upward elastic force will cause a certain negative pressure to be generated on the top of the corrugated expander, that is, an upward force is exerted on the transformer oil, resulting in the pressure sensor at the bottom of the oil storage cabinet only collecting part of the transformer oil's own pressure. Therefore, the pressure collected by the pressure sensor at the bottom of the oil storage cabinet is the sum of the pressure of the transformer oil itself and the pressure of the corrugated expander on the transformer oil. Therefore, for the internal oil vertical corrugated oil storage cabinet, if the pressure collected by the pressure sensor is directly used to calculate its oil level, because part of the pressure is not generated by the transformer oil itself, the calculated oil level will be too large or too small. In order to obtain the pressure belonging to the transformer oil itself, in this embodiment, the pressure generated by the corrugated expander on the transformer oil must be calculated first. First, according to the deformation of the corrugated expander, the overall pressure F=K(H1-H0) generated downward is calculated, where K is the elastic coefficient of the corrugated expander, H0 is the height of the corrugated expander in a free state, and H1 is the actual oil level of the transformer oil in the oil storage cabinet. Because the area of ​​the transformer oil used to bear the downward pressure of the corrugated expander is approximately equal to the area of ​​the top cover of the corrugated expander, the pressure P1=F / S=K(H1-H0) / S given to the transformer oil by the corrugated expander, where S is the top cover area of ​​the corrugated expander.

[0097] 306. Correct the oil level according to the pressure, the density and the oil pressure to obtain a corrected oil level;

[0098] In this embodiment, the oil pressure is the oil pressure at the bottom of the internal oil vertical corrugated oil conservator collected by the pressure sensor. The purpose of correcting the oil level is to ensure that the measured oil level is infinitely close to the actual oil level of the oil conservator. The corrected oil level is the oil level that eliminates possible errors. Therefore, the corrected oil level can be understood as the actual oil level of the internal oil vertical corrugated oil conservator. It can be known from step 305 that the pressure collected by the pressure sensor P=P1+P2=K(H1-H0) / S+ρg(H1-H2). It can be calculated that the corrected oil level H1=(PS+KH0+ ρgSH2) / (ρgS+K), where: P is the oil pressure collected by the oil pressure sensor, P1 is the pressure of the transformer oil given by the corrugated expander, P2 is the pressure of the transformer oil in the oil conservator, S is the top cover area of ​​the corrugated expander, K is the elastic coefficient of the corrugated expander, H0 is the height of the corrugated expander in a free state, H2 is the height of the pressure sensor relative to the bottom of the oil conservator, in this embodiment, because the pressure sensor is installed at the bottom of the oil conservator, H2=0, ρ is the density of the transformer oil in the oil conservator, and g is the acceleration of gravity.

[0099] 307. Compare the corrected oil level with a low oil level threshold and a high oil level threshold respectively;

[0100] In this example, the corrected oil level is compared with the low oil level threshold and the high oil level threshold respectively. If the corrected oil level is less than the low oil level threshold, an alarm signal is issued; if the corrected oil level is greater than the high oil level threshold, an alarm signal is also issued, which can remind the operation and maintenance personnel to respond to the transformer failure in time to reduce losses.

[0101] Beneficial effects of this embodiment: This embodiment, for the internal oil vertical corrugated oil conservator, not only takes into account the influence of transformer oil temperature on the measurement of oil level in the oil conservator, but also takes into account the additional pressure generated by the corrugated expander on the transformer oil, further eliminating the oil level error and ensuring accurate monitoring of the oil level in the oil conservator.

[0102] Embodiment 4

[0103] See also Figure 4 , Figure 4 A schematic structural diagram of an oil level measuring device for an oil storage cabinet provided in an embodiment of the present invention.

[0104] This embodiment provides an oil level measuring device for an oil storage tank, comprising:

[0105] Pressure sensor, temperature sensor, conversion module and data processing module; the pressure sensor is used to obtain the oil pressure of the transformer oil - convert the oil pressure of the transformer oil into a DC current or voltage signal, and output it to the conversion module; the temperature sensor is used to obtain the temperature of the transformer oil and the ambient temperature, and output the obtained temperature to the conversion module; the conversion module is used to convert the current signal or voltage signal of the sensor into a digital quantity, and output the digital quantity to the data processing module; the data processing module is used to process the digital quantity and output the oil level; the pressure sensor and the temperature sensor are connected to the data processing module through the conversion module. In this embodiment, the conversion module is an A / D conversion module, and the data processing module is a microprocessor. In addition to processing digital quantities, it is also necessary to complete the collection and storage of oil pressure and temperature data, and human-computer dialogue.

[0106] Specifically, the oil level measuring device of the oil storage cabinet in this embodiment is also provided with: a power supply module, a human-computer interaction module, a communication module, a storage module, an output drive module and a clock; the power supply module is respectively connected to the temperature sensor, the pressure sensor, the clock, the data processing module and other modules to convert AC 220V or DC 220V, DC 110V into a DC voltage for use by the temperature sensor, the pressure sensor, the clock, the data processing module and other modules; the human-computer interaction module inputs instructions through a keyboard, a button or a touch screen, displays relevant information through a digital tube, an LCD screen or an LED screen, and performs parameter settings and status and data browsing, etc.; the communication module uses serial port, 485 bus, Bluetooth, WIFI, etc. to interact with the communication management machine for receiving commands, modifying parameter settings, outputting historical sampling data, status and alarm information, etc.; the storage module is a large-capacity storage device for storing events, oil pressure, transformer oil temperature and other data; the output drive module outputs independent nodes through photoelectric isolation or small relays, can send out action and alarm signals, and display values ​​such as oil level and temperature through LED or LCD screen; the clock provides time for the data processing module to mark the time of historical data, which is convenient for data analysis and utilization. The input end of the data processing module is connected to the conversion module and the clock respectively, and the output end is connected to the human-computer interaction module, communication module, storage module and output drive module respectively.

[0107] Beneficial effects of this embodiment: The oil level measuring device for the oil tank provided in this embodiment can simultaneously realize the functions of an oil temperature gauge, an oil level gauge, and an oil pressure quick-acting relay, and can assist in judging whether a respirator is blocked or whether an internal oil vertical corrugated oil storage cabinet is stuck by checking whether the oil level is abnormal. It can also judge whether the oil level is abnormal by checking the temperature curve and the oil level curve of the transformer oil, thereby reducing the overall device cost and operation and maintenance workload.

[0108] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0109] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0110] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0111] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of software functional modules.

[0112] If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0113] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the oil level of an oil storage tank, characterized in that: include: Get transformer oil temperature and oil pressure; Correcting the temperature according to the ambient temperature and a correction coefficient to obtain a corrected temperature, wherein the correction coefficient is determined according to an installation position of the temperature sensor; determining the density of the transformer oil according to the corrected temperature; determining the oil level of the transformer oil according to the oil pressure and the density; After determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes: Calculating the pressure exerted by the bellows expander on the transformer oil; The oil level is corrected according to the pressure, the density and the oil pressure to obtain a corrected oil level, wherein the oil pressure is the oil pressure at the bottom of the internal oil vertical corrugated oil storage tank; The corrected oil level H1=(PS+KH0+ρgSH2) / (ρgS+K), wherein: P is the oil pressure, S is the top cover area of ​​the bellows expander, K is the elastic coefficient of the bellows expander, H0 is the height of the bellows expander in a free state, H2 is the height of the pressure sensor relative to the bottom of the oil storage tank, ρ is the density, and g is the acceleration of gravity.

2. The method for calculating the oil level of an oil storage tank according to claim 1, characterized in that: The correction coefficient is proportional to the distance of the temperature sensor relative to the oil conservator.

3. The method for calculating the oil level of an oil storage tank according to claim 1, characterized in that: The correction temperature T1=T0-k(T0-T2), wherein: T0 is the temperature of the transformer oil, T2 is the ambient temperature, and k is the correction coefficient; If the temperature sensor is installed in the oil storage tank, k=0.

4. The method for calculating the oil level of an oil storage tank according to claim 1, characterized in that: After determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes: Calculating the per unit height value of the oil level in the oil conservator; Calculating the rotation angle of the oil level gauge according to the per unit value of the height; The indicated value of the oil level gauge is calculated according to the rotation angle.

5. The method for calculating the oil level of an oil storage tank according to claim 1, characterized in that: After determining the oil level of the transformer oil according to the oil pressure and the density, the method further includes: calculating the oil volume ratio of the oil conservator according to the oil level; The oil volume of the oil storage tank is calculated according to the oil volume ratio.

6. The method for calculating the oil level of an oil storage tank according to claim 1, characterized in that: After the oil level is corrected according to the pressure, the density and the oil pressure, the method further includes: comparing the corrected oil level with a low oil level threshold and a high oil level threshold respectively; If the corrected oil level is less than the low oil level threshold or greater than the high oil level threshold, an alarm signal is issued.

7. An oil level measuring device for an oil storage tank, characterized in that: include: Pressure sensor, temperature sensor, conversion module and data processing module; The pressure sensor is used to obtain the oil pressure of the transformer oil; The temperature sensor is used to obtain the temperature of the transformer oil and the ambient temperature; The conversion module is used to convert the current signal or voltage signal of the sensor into a digital quantity, and output the digital quantity to the data processing module; The data processing module is used to process the digital quantity and output the oil level; The pressure sensor and the temperature sensor are connected to the data processing module through the conversion module; The oil level measuring device for an oil storage tank executes the oil level measuring method for an oil storage tank as claimed in claim 1.

8. The oil level measuring device for an oil storage tank according to claim 7, characterized in that: It also includes: a communication module, a storage module and a human-computer interaction module connected to the data processing module; The communication module is used to exchange information with the communication management machine; The storage module is used to store the oil pressure and the temperature; The human-computer interaction module is used to input instructions.

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