A micro-power wireless oil pressure sensor system monitoring method and device

Abstract

The present invention relates to the field of online monitoring technology, and in particular to a micro-power wireless oil pressure sensor system monitoring method and device thereof, the monitoring method comprising: sensing the oil temperature and oil pressure at each moment in 24 hours and transmitting them to a data processing library for processing, performing curve fitting to obtain a function, and repeating the steps to obtain an average function; calculating a theoretical value based on theoretical conditions, and then performing curve fitting to obtain a theoretical function; comparing the obtained functions to obtain the maximum difference and minimum difference at each moment in 24 hours; predicting each moment in 24 hours every day, and comparing the predicted results with the theoretical function to obtain the difference at each moment, comparing the obtained difference at each moment, and providing feedback and warning based on the comparison results. The present invention can predict the development of the equipment operating status in advance, reduce the losses caused by failures, and reduce the frequency of periodic inspections of the equipment by staff.

Description

Technical Field

[0001] The present invention relates to the technical field of online monitoring, and in particular to a micro-power wireless oil pressure sensor system monitoring method and device. Background Art

[0002] Insulating oil is widely used in high-voltage electrical equipment such as power transformers, oil circuit breakers, oil-filled cables, and power capacitor bushings. It can impregnate and protect solid insulation of transformers, cables, capacitors, etc., fill bubbles in the insulation, prevent the intrusion of external air and moisture, and ensure reliable insulation.

[0003] Due to the excellent performance of insulating oil, oil-immersed power equipment is increasingly being used in substations, and oil temperature and oil pressure are key indicators of the health of oil-immersed power equipment. Currently, most substations still use traditional methods to monitor oil level status, where operation and maintenance personnel periodically read meters. This consumes a lot of costs and relies on the experience of the operation and maintenance personnel, which is subject to certain human error factors. There is also a low oil pressure alarm sensor, which is a mechanical alarm device that only issues an alarm when the oil pressure is abnormal. At this time, the fault has often already occurred and cannot be reversed. There is a certain lag in the fault alarm, and it cannot record the continuous operation status of the equipment. In addition, mechanical oil pressure alarm sensors are often complex in structure, large in size, bulky in appearance, and expensive, which also brings many inconveniences to operation and maintenance personnel. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the defects of the background technology and provide a micro-power wireless oil pressure sensor system monitoring method and device, so that it can monitor the oil temperature and oil pressure of oil-immersed power equipment and upload the monitoring data, thereby realizing online monitoring of the oil temperature and oil pressure of oil-immersed power equipment, saving a lot of operation and maintenance costs, and being able to record the operating status of the current online equipment in real time, grasp the changing trend of the equipment operating status, thereby predicting the development of the equipment operating status in advance, and reducing the losses caused by failures.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A micro-power wireless oil pressure sensor system monitoring method, the micro-power wireless oil pressure sensor system monitoring method comprising the following steps:

[0007] S1: Senses the oil pressure and temperature at every moment of the day and transmits the information to the data processing library;

[0008] S2: The data processing library processes the received information and performs curve fitting to obtain the oil pressure function and oil temperature function;

[0009] S3: Repeat the operations of step S1 and step S2 for one week, and process the data obtained in one week to obtain the average data;

[0010] S4: performing curve fitting on the average data obtained in step S3 to obtain an oil pressure average function and an oil temperature average function;

[0011] S5: The data processing library calculates the oil pressure and oil temperature according to theoretical conditions and obtains theoretical oil pressure data and theoretical oil temperature data;

[0012] S6: Perform curve fitting on the theoretical data obtained in step S5 to obtain a theoretical function of oil pressure and a theoretical function of oil temperature;

[0013] S7: The data processing library compares the oil pressure average function obtained in step S4 with the oil pressure theoretical function obtained in step S6, and the oil temperature average function obtained in step S4 with the oil temperature theoretical function obtained in step S6, to obtain the maximum and minimum differences in oil pressure and oil temperature at each moment;

[0014] S8: Monitor the oil pressure and oil temperature every day and perform curve fitting on the data of the day to derive a function. Use the function to predict the oil temperature and oil pressure of the next period. Compare the predicted results with the theoretical function to obtain the difference at each moment.

[0015] S9: Compare the difference value at each moment obtained in step S8 with the maximum difference and minimum difference obtained in step S7. When the difference value is greater than the maximum value in step S7 and the difference value is less than the minimum value in step S7, a feedback warning is issued. At the same time, the actual value at each moment is subtracted from the predicted value to obtain the maximum difference and minimum difference. When the maximum difference is greater than the maximum value in step S7 and the minimum difference is less than the minimum value in step S7, a feedback warning is issued.

[0016] Furthermore, in step S5, according to the phase cusp theory of cavitation bubble dynamics and fluid mechanics, water vapor and oil vapor are ideal gases, and the ideal gas state equations of water vapor and oil vapor are:

[0017] P g V = n g ·R * ·T (1)

[0018] P V V = n V ·R * ·T (2)

[0019] Where V is the bubble volume; R* is the ideal gas constant; T is the thermodynamic temperature of the ideal gas, which is a constant; n g and n V is the amount of water vapor and oil vapor; P g and PV is the partial pressure of water vapor and oil vapor;

[0020] The internal pressure is composed of the partial pressure of gas and steam. The partial pressure of steam can be obtained from the quantitative relationship between water and oil vapor:

[0021] P g +P V =P1+P δ (3)

[0022]

[0023] P1=P atm +P oil =P atm +ρ·g·h (5)

[0024] P V =x·P w +y·P0 (6)

[0025]

[0026] Where P1 is the fluid pressure; P δ is the surface tension of the oil; δ is the surface tension coefficient; R is the radius of the bubble in the oil; ρ is the density of the current transformer oil; g is the acceleration of gravity; h is the depth of the oil; P atm is atmospheric pressure; P oil is the liquid pressure of the oil; x and y represent the percentage of water and oil respectively; W is the molecular weight of gaseous water in the oil; M w and M δ Represent the molar mass of water and oil respectively; P w is the saturated vapor pressure of water; P0 is the saturated vapor pressure of oil, and P is obtained by the following formula w 、P0:

[0027] log 10 (P W )=A-(B / (T+C)) (8)

[0028] ln(P0)=D+E / T (9)

[0029] Among them, A, B, C, and D are constants;

[0030] For a given external pressure, the above formula gives a direct relationship between pressure and radius. If the external pressure changes, the bubble will change its volume to reach a new equilibrium state. Therefore, an equation can be used to relate the determined state to the initial state to determine the state. The initial state is represented by 0. Then the initial state equation can be expressed as:

[0031] Pg0 +P v0 =P 10 +P δ0 (10)

[0032] Among them, P g0 is the initial partial pressure of the gas; P v0 is the initial partial pressure of steam; P 10 is the pressure under certain conditions; P δ0 is the initial saturated vapor pressure of the oil;

[0033] At high load rates, the upper limit of the oil temperature rise rate in the current transformer is 15°C / min, so it is considered an isothermal process and satisfies the following relationship:

[0034] p g0 V0=p g V (11)

[0035] Where V0 is the initial steam volume; p g0 is the initial partial pressure of the gas; p g is the partial pressure of the gas;

[0036] At the same time, regardless of temperature changes, the vapor pressure does not change. Combining formulas (3), (4), (10), and (11), we can obtain:

[0037]

[0038] Where R0 is the initial radius of the bubble in the oil; R is the determined radius of the bubble in the oil;

[0039] When the liquid pressure completely offsets the additional pressure of surface tension and the total inward pressure can no longer balance the outward pressure, the oil body will expand. The following formula is the derivative of the above formula:

[0040]

[0041] By solving the above equation, we can get the following equation:

[0042]

[0043] Among them, R C is the critical radius of bubbles in oil;

[0044] By combining (12) and (14), the critical pressure value R is obtained C :

[0045]

[0046] Therefore, the theoretical pressure value P of the oil in the current transformer is B is the difference between the liquid pressure and the critical pressure, as shown in the following formula:

[0047]

[0048] Thus the theoretical value of oil pressure is obtained, and multi-time calculation is performed to obtain the theoretical oil pressure data at multiple times;

[0049] Secondly, for the theoretical calculation of oil temperature, through the mass conservation equation, energy conservation equation and momentum conservation equation, the oil density does not change with time, and its differential form is:

[0050]

[0051] in, is the Hamiltonian operator; V is the fluid velocity vector; ρ represents the current transformer oil density; f is the unit fluid mass force; p is the fluid pressure; μ is the dynamic viscosity of the fluid; e is the internal energy of the fluid; q is the volume heat source of the fluid; k is the thermal conductivity of the fluid; S is the portion of the fluid mechanical energy converted into thermal energy under the combined action of the oil viscosity and the internal heat source of the fluid; T1 is the current transformer oil temperature;

[0052] Since the relative velocity of the oil in the current transformer to the box is 0, the surface temperature of the solid box is consistent with the temperature of the oil. If the current transformer shell and the radiator shell are simplified as smooth planes, the heat dissipation process of the current transformer shell can be considered as longitudinal flat plate convection heat transfer. According to the basic theory of heat transfer, the Nusselt number N of the horizontal plate is uh and the Nusselt number N of the vertical plate uv They are as follows:

[0053]

[0054]

[0055] λ Ra =λ Gr λ Pr (twenty four)

[0056] Among them, λ Pr is the Prandtl number; λ Gr is the Grashof number; λ Ra is the Rayleigh number; g is the acceleration due to gravity; β is the corresponding fluid expansion coefficient; v is the kinematic viscosity of the fluid; L is the characteristic size; c is the specific heat capacity of the fluid; θ is the temperature difference between the wall and the external fluid;

[0057] Substituting the obtained Nusselt number into formula (25) can obtain the convective heat transfer coefficient of the current transformer:

[0058]

[0059] Where h1 is the convective heat transfer coefficient; N uiis the Nusselt number; i is the current value;

[0060] Heat flow q generated by radiation heat transfer of current transformer housing r It can be expressed by the following formula:

[0061]

[0062] Where ε is the surface emissivity of the current transformer housing; σ is the Stefan-Boltzmann constant, 5.67×10 -8 W / (m 2 ·K 4 );T w is the transformer casing temperature; T a is the external ambient temperature of the current transformer;

[0063] The process of the thermal physical parameters of the current transformer oil changing with temperature is shown below:

[0064] μ(T1)=exp(F)T1 -E (27)

[0065] Where, E = 9.55 ± 0.23, F = 50.24 ± 1.33; μ(T1) is the dynamic viscosity of the current transformer;

[0066] S=μ(T1)·q r (28)

[0067] q=q r (29)

[0068] e=h1q r (30)

[0069] Substituting (28), (29), and (30) into formula (19), we obtain:

[0070]

[0071] According to the above formula, the current scale temperature T1 can be obtained, and the theoretical temperature value at each moment can be deduced from it.

[0072] Furthermore, the specific method in step S2 is:

[0073] S2.1: Monitor the oil temperature and oil pressure of oil-immersed electrical equipment through sensors;

[0074] S2.2: Upload the monitoring data to the data processing library in real time through the wireless communication module;

[0075] S2.3: After the data processing library completes data processing, it transmits the results to the port for the next step.

[0076] A micro-power wireless oil pressure sensor system device is applicable to a micro-power wireless oil pressure sensor system monitoring method, comprising: a movable portion, a fixed portion, and a data monitoring component;

[0077] The fixing portion is fixedly mounted on the transformer and includes: a No. 1 oil passage and a No. 2 oil passage. The No. 1 oil passage is arranged inside the fixing portion along the axial direction of the fixing portion and passes through one end of the fixing portion. The No. 2 oil passage is arranged inside the fixing portion and passes through the fixing portion, and connects the internal oil circuit of the transformer with the No. 1 oil passage.

[0078] The movable portion is connected to the fixed portion and includes: a shell and a pipe. The shell is a hollow structure. The pipe is arranged at the center of the shell, one end of which passes through the shell and is connected to the interior thereof, and the other end is inserted into the first oil passage. An oil inlet hole is provided on the end of the pipe away from the shell, and an exhaust hole is provided at the portion of the pipe that contacts the shell. The exhaust hole passes through the pipe and the shell and is connected to the outside.

[0079] The data monitoring component is arranged in the hollow area inside the shell, and includes: a sensor chip and a wireless communication module. The sensor chip is connected to the pipeline, and the wireless communication module is installed at the upper end of the interior of the shell, and is used to sense the oil pressure and oil temperature at each time of the day, and transmit the information of the oil pressure and oil temperature to the data processing library.

[0080] Furthermore, the wireless communication module is a Lora module, which is a low-power micro-power wireless communication module that uploads the collected monitoring data wirelessly.

[0081] Furthermore, a No. 1 spring is provided inside the No. 1 oil channel away from the through end, and the No. 1 spring is connected to the stopper.

[0082] Furthermore, the fixing portion further includes a screw head and a hexagonal mounting block, the screw head is threadedly connected to the transformer, and the hexagonal mounting block is fixedly mounted to the screw head.

[0083] Furthermore, the hexagonal mounting block is provided with a first slide groove and a second slide groove;

[0084] The first and second chutes are arc-shaped chutes, the first chute is provided on the surface of the hexagonal mounting block, and the second chute is provided inside the hexagonal mounting block. The first and second chutes are connected, and the cross-sections of the first and second chutes along the height direction of the hexagonal mounting block are L-shaped;

[0085] The housing is provided with a slider, which is an L-shaped structure, with a first side of the L-shaped structure connected to the housing and a second side perpendicular to the first side. The slider matches the cross-sectional shape of the first and second chutes, and the slider is inserted into the trough body, with the side wall of the trough body fitting against the wall surface of the slider;

[0086] A mounting groove is provided at the end of the No. 1 slide groove. The mounting groove is larger than the No. 1 slide groove in the width direction and can accommodate the first side of the slider.

[0087] Furthermore, a No. 2 spring is provided inside the No. 2 slide groove, and one end of the No. 2 spring is connected to a baffle.

[0088] Furthermore, a sealing ring is provided on one end of the side wall of the No. 1 oil channel away from the spiral head.

[0089] The beneficial effects of the present invention are: 1. The present invention can monitor the oil temperature at all times through data processing and function fitting, and can predict the oil temperature at the next moment. The predicted data is compared with the theoretical data, and the difference is obtained and then compared. The operation status of the equipment can be intuitively seen, thereby predicting the development of the equipment operation status in advance, reducing the losses caused by failures, reducing the frequency of periodic inspections of the equipment by staff, reducing the work intensity of staff, and improving the applicability of the equipment.

[0090] 2. The present invention adopts a low-power micro-power wireless communication module. Its micro-power characteristics can maximize the efficiency of battery utilization, extend the service life of the equipment, and reduce the replacement frequency; the collected monitoring data is uploaded wirelessly, which greatly reduces communication interference; the oil temperature and oil pressure of the oil-immersed power equipment are wirelessly monitored in real time through LoRa and the monitoring data is uploaded, realizing online monitoring of the oil temperature and oil pressure of the oil-immersed power equipment, saving a lot of operation and maintenance costs, and being able to record the operating status of the current online equipment in real time, grasp the changing trend of the equipment operating status, thereby predicting the development of the equipment operating status in advance and reducing the losses caused by failures.

[0091] 3. The design of the fixed part and the movable part makes it necessary to install the fixed part only for the first time during installation. The installation difficulty of the fixed part is the same as that of the existing technology, and most of the time is spent on replacing the movable part, which not only saves maintenance costs but also saves manpower. When disassembling, only the movable part needs to be rotated counterclockwise until it stops rotating, and then moved to the side away from the fixed part to complete the disassembly, which is quick and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0093] Figure 1This is a flow chart of the micro-power wireless oil pressure sensor system monitoring method of the present invention;

[0094] Figure 2 It is a left side view of the micro-power wireless oil pressure sensor system device of the present invention;

[0095] Figure 3 This is a right rear view of the micro-power wireless oil pressure sensor system in a disassembled state;

[0096] Figure 4 This is a left side view of the micro-power wireless oil pressure sensor system in a disassembled state;

[0097] Figure 5 This is a left side view of the micro-power wireless oil pressure sensor system in the installed state;

[0098] Figure 6 for Figure 6 AA sectional view;

[0099] Figure 7 for Figure 7 BB cross-sectional view;

[0100] Figure 8 This is a schematic diagram of the structure of the No. 1 and No. 2 chute devices of the micro-power wireless oil pressure sensor system;

[0101] Figure numerals: 1. Fixed part; 11. Screw head; 12. Hexagonal mounting block; 13. Oil channel No. 1; 14. Stop block; 15. Spring No. 1; 16. Oil channel No. 2; 17. Slide groove No. 1; 171. Mounting groove; 18. Slide groove No. 2; 19. Sealing ring; 2. Movable part; 21. Shell; 22. Pipeline; 23. Slider; 24. Oil inlet hole; 25. Exhaust hole; 3. Data monitoring component; 31. Sensor chip; 32. Wireless communication module; 4. Spring No. 2; 5. Baffle. DETAILED DESCRIPTION

[0102] 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 described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0103] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0104] like Figure 1The micro-power wireless oil pressure sensor system monitoring method shown includes the following steps:

[0105] S1: Senses the oil pressure and temperature at every moment of the day and transmits the information to the data processing library;

[0106] S2: The data processing library processes the received information and performs curve fitting to obtain the oil pressure function and oil temperature function;

[0107] S3: Repeat the operations of step S1 and step S2 for one week, and process the data obtained in one week to obtain the average data;

[0108] S4: performing curve fitting on the average data obtained in step S3 to obtain an oil pressure average function and an oil temperature average function;

[0109] S5: The data processing library calculates the oil pressure and oil temperature according to theoretical conditions and obtains theoretical oil pressure data and theoretical oil temperature data;

[0110] S6: Perform curve fitting on the theoretical data obtained in step S5 to obtain a theoretical function of oil pressure and a theoretical function of oil temperature;

[0111] S7: The data processing library compares the oil pressure average function obtained in step S4 with the oil pressure theoretical function obtained in step S6, and the oil temperature average function obtained in step S4 with the oil temperature theoretical function obtained in step S6, to obtain the maximum and minimum differences in oil pressure and oil temperature at each moment;

[0112] S8: Monitor the oil pressure and oil temperature every day and perform curve fitting on the data of the day to derive a function. Use the function to predict the oil temperature and oil pressure of the next period. Compare the predicted results with the theoretical function to obtain the difference at each moment.

[0113] S9: Compare the difference value at each moment obtained in step S8 with the maximum difference and minimum difference obtained in step S7. When the difference value is greater than the maximum value in step S7 and the difference value is less than the minimum value in step S7, a feedback warning is issued. At the same time, the actual value at each moment is subtracted from the predicted value to obtain the maximum difference and minimum difference. When the maximum difference is greater than the maximum value in step S7 and the minimum difference is less than the minimum value in step S7, a feedback warning is issued.

[0114] During the specific implementation process, when the oil-immersed transformer starts working, the micro-power wireless oil pressure sensor itself is grounded and starts working. Its built-in temperature sensing device and oil pressure sensing device constantly sense the oil temperature and oil pressure, and periodically (once an hour) upload the temperature and oil pressure to the data processing library. The data processing library performs curve fitting on the data of the day and derives a function. This operation is repeated for one week, that is, the temperature and oil pressure data of seven days are averaged to obtain the actual value and actual function.

[0115] On the 8th day, the micro-power wireless oil pressure sensor also monitors the oil temperature and oil pressure and periodically transmits the data to the data processing library. The data processing library performs curve fitting to obtain the function of the day, and then uses the function to predict the oil temperature and oil pressure at the next moment, and compares the predicted value with the theoretical value obtained by the theoretical function. When the difference between the predicted value and the theoretical value is greater than the maximum difference between the average value and the theoretical value at the next moment, or less than the minimum difference between the average value and the theoretical value, the system assessment device has a problem at this time. Secondly, when the maximum difference and minimum difference obtained by subtracting the actual value from the predicted value at each moment are greater than the maximum value in step S7 and the minimum difference is less than the minimum value in step S7, the system assessment device has a problem at this time, and an early warning signal is transmitted to the port to inform the staff and check the equipment in time. When the predicted value is between the difference between the average value and the theoretical value at the next moment, the system assessment device is risk-free and continues to monitor.

[0116] According to the phase apex theory of cavitation bubble dynamics and fluid mechanics in step S5, the cavitation phenomenon in the engineering liquid is almost nuclear cavitation. There is tiny cavitation nucleus in the liquid itself. When the pressure drops to the corresponding threshold, bubbles will be formed. The dissolved gas and water in the transformer oil can serve as cavitation nucleus. Now, according to the actual situation and phase theory of transformer oil, the cavitation threshold value of transformer oil is obtained. Under normal pressure, various gases approximately meet the state equation of ideal gas. Water vapor and oil vapor are also real gases. When their temperature is well below the critical temperature, water vapor and oil vapor can be approximately regarded as ideal gases. Water vapor and oil vapor are ideal gases. The ideal gas state equation of water vapor and oil vapor is:

[0117] P g V = n g ·R * ·T (1)

[0118] P V V = n V ·R * ·T (2)

[0119] Where V is the bubble volume; R* is the ideal gas constant; T is the thermodynamic temperature of the ideal gas, which is a constant; ng and n V is the amount of water vapor and oil vapor; P g and P V is the partial pressure of water vapor and oil vapor;

[0120] The internal pressure is composed of the partial pressure of gas and steam. The partial pressure of steam can be obtained from the quantitative relationship between water and oil vapor:

[0121] P g +P V =P1+P δ (3)

[0122]

[0123] P1=P atm +P oil =P atm +ρ·g·h (5)

[0124] P V =x·P w +y·P0 (6)

[0125]

[0126] Where P1 is the fluid pressure; P δ is the surface tension of the oil; δ is the surface tension coefficient; R is the radius of the bubble in the oil; ρ is the density of the current transformer oil; g is the acceleration of gravity; h is the depth of the oil; P atm is atmospheric pressure; P oil is the liquid pressure of the oil; x and y represent the percentage of water and oil respectively; W is the molecular weight of gaseous water in the oil; M w and M δ Represent the molar mass of water and oil respectively; P w is the saturated vapor pressure of water; P0 is the saturated vapor pressure of oil, and P is obtained by the following formula w 、P0:

[0127] log 10 (P W )=A-(B / (T+C)) (8)

[0128] ln(P0)=D+E / T (9)

[0129] Among them, A, B, C, and D are constants;

[0130] For a given external pressure, the above formula gives a direct relationship between pressure and radius. If the external pressure changes, the bubble will change its volume to reach a new equilibrium state. Therefore, an equation can be used to relate the determined state to the initial state to determine the state. The initial state is represented by 0. Then the initial state equation can be expressed as:

[0131] P g0 +P v0 =P 10 +P δ0 (10)

[0132] Among them, P g0 is the initial partial pressure of the gas; P v0 is the initial partial pressure of steam; P 10 is the pressure under certain conditions; P δ0 is the initial saturated vapor pressure of the oil;

[0133] At high load rates, the upper limit of the oil temperature rise rate in the current transformer is 15°C / min, so it is considered an isothermal process and satisfies the following relationship:

[0134] p g0 V0=p g V (11)

[0135] Where V0 is the initial steam volume; p g0 is the initial partial pressure of the gas; p g is the partial pressure of the gas;

[0136] At the same time, regardless of temperature changes, the vapor pressure does not change. Combining formulas (3), (4), (10), and (11), we can obtain:

[0137]

[0138] Where R0 is the initial radius of the bubble in the oil; R is the determined radius of the bubble in the oil;

[0139] When the liquid pressure completely offsets the additional pressure of surface tension and the total inward pressure can no longer balance the outward pressure, the oil body will expand. The following formula is the derivative of the above formula:

[0140]

[0141] By solving the above equation, we can get the following equation:

[0142]

[0143] Among them, R C is the critical radius of bubbles in oil;

[0144] By combining (12) and (14), the critical pressure value P is obtained C :

[0145]

[0146] Therefore, the theoretical pressure value P of the oil in the current transformer is B is the difference between the liquid pressure and the critical pressure, as shown in the following formula:

[0147]

[0148] Thus the theoretical value of oil pressure is obtained, and multi-time calculation is performed to obtain the theoretical oil pressure data at multiple times;

[0149] Secondly, for the theoretical calculation of oil temperature, through the mass conservation equation, energy conservation equation and momentum conservation equation, the oil density does not change with time, and its differential form is:

[0150]

[0151] in, is the Hamiltonian operator; V is the fluid velocity vector; ρ represents the current transformer oil density; f is the unit fluid mass force; p is the fluid pressure; μ is the dynamic viscosity of the fluid; e is the internal energy of the fluid; q is the volume heat source of the fluid; k is the thermal conductivity of the fluid; S is the portion of the fluid mechanical energy converted into thermal energy under the combined action of the oil viscosity and the internal heat source of the fluid; T1 is the current transformer oil temperature;

[0152] Since the relative velocity of the oil in the current transformer to the box is 0, the surface temperature of the solid box is consistent with the temperature of the oil. If the current transformer shell and the radiator shell are simplified as smooth planes, the heat dissipation process of the current transformer shell can be considered as longitudinal flat plate convection heat transfer. According to the basic theory of heat transfer, the Nusselt number N of the horizontal plate is uh and the Nusselt number N of the vertical plate uv They are as follows:

[0153]

[0154] λ Ra =λ Gr λ Pr (twenty four)

[0155] Among them, λ Pr is the Prandtl number; λ Gr is the Grashof number; λ Ra is the Rayleigh number; g is the acceleration due to gravity; β is the corresponding fluid expansion coefficient; v is the kinematic viscosity of the fluid; L is the characteristic size; c is the specific heat capacity of the fluid; θ is the temperature difference between the wall and the external fluid;

[0156] Substituting the obtained Nusselt number into formula (25) can obtain the convective heat transfer coefficient of the current transformer:

[0157]

[0158] Where h1 is the convective heat transfer coefficient; N ui is the Nusselt number; i is the current value;

[0159] Heat flow q generated by radiation heat transfer of current transformer housing r It can be expressed by the following formula:

[0160]

[0161] Where ε is the surface emissivity of the current transformer housing; σ is the Stefan-Boltzmann constant, 5.67×10 -8 W / (m 2 ·K 4 );T w is the transformer casing temperature; T a is the external ambient temperature of the current transformer;

[0162] The process of the thermal physical parameters of the current transformer oil changing with temperature is shown below:

[0163] μ(T1)=exp(F)T1 -E (27)

[0164] Where, E = 9.55 ± 0.23, F = 50.24 ± 1.33; μ(T1) is the dynamic viscosity of the current transformer;

[0165] S=μ(T1)·q r (28)

[0166] q=q r (29)

[0167] e=h1q r (30)

[0168] Substituting (28), (29), and (30) into formula (19), we obtain:

[0169]

[0170] According to the above formula, the current scale temperature T1 can be obtained, and the theoretical temperature value at each moment can be deduced from it.

[0171] As a specific embodiment of the present invention, the specific method in step S2 is:

[0172] S2.1: Monitor the oil temperature and oil pressure of oil-immersed electrical equipment through sensors;

[0173] S2.2: Upload the monitoring data to the data processing library in real time through the wireless communication module;

[0174] S2.3: After the data processing library completes data processing, it transmits the results to the port for the next step.

[0175] By wirelessly monitoring the oil temperature and oil pressure of oil-immersed power equipment in real time and uploading the monitoring data, online monitoring of the oil temperature and oil pressure of oil-immersed power equipment can be achieved. This can record the operating status of the current online equipment in real time, grasp the changing trend of the equipment operating status, and thus predict the development of the equipment operating status in advance, reducing the losses caused by failures.

[0176] The following describes Figures 2 to 8 The micro-power wireless oil pressure sensor system device shown is suitable for the above-mentioned micro-power wireless oil pressure sensor system monitoring method, comprising: a fixed part 1, a movable part 2 and a data monitoring component 3; the fixed part 1 is fixedly installed on the transformer, comprising: a first oil passage 13 and a second oil passage 16, the first oil passage 13 is arranged inside the fixed part 1 along the axial direction of the fixed part 1 and passes through one end of the fixed part 1, the second oil passage 16 is arranged inside the fixed part 1 and passes through the fixed part 1, and connects the internal oil circuit of the transformer with the first oil passage 13; the movable part 2 is connected to the fixed part 1, comprising: a shell 21 and a pipe 22, the shell 21 is a hollow structure, and the pipe 22 is arranged in the shell 21 The center of the shell 21 is formed, one end of the shell 21 passes through the shell 21 and is connected to the inside thereof, and the other end is inserted into the No. 1 oil channel 13. An oil inlet hole 24 is provided on the end of the pipe 22 away from the shell 21, and an exhaust hole 25 is provided on the part of the pipe 22 that contacts the shell 21. The exhaust hole 25 passes through the pipe 22 and the shell 21 and is connected to the outside; the data monitoring component 3 is arranged in the hollow area inside the shell 21, including: a sensor chip 31 and a wireless communication module 32. The sensor chip 31 is connected to the pipe 22, and the wireless communication module 32 is installed at the upper end of the inner part of the shell 21, for sensing the oil pressure and oil temperature at each time of the day, and transmitting the information of the oil pressure and oil temperature to the data processing library.

[0177] During the specific implementation process, the insulating oil flows into the No. 1 oil channel 13 through the No. 2 oil channel 16, and then enters the interior of the pipeline 22 through the oil inlet hole 24. The air in the initial state of the pipeline 22 is discharged from the exhaust hole 25, which facilitates the oil body to enter the pipeline 22 while exhausting the air, ensuring the purity of the oil in the monitored part inside. The oil level rises to contact the sensor chip 31. After the sensor chip 31 measures the oil temperature and oil pressure data, the wireless communication module 32 transmits the monitored data to the database for processing.

[0178] As a preferred embodiment of the above, the wireless communication module 32 is a Lora module, which is a low-power micro-power wireless communication module 32. On the one hand, its micro-power characteristics can maximize the efficiency of battery utilization and extend the service life of the equipment. On the other hand, it uploads the collected monitoring data wirelessly, which greatly reduces communication interference and improves data accuracy.

[0179] In order to prevent the insulating oil from flowing from the No. 2 oil channel 16 into the No. 1 oil channel 13 and overflowing when the fixed part 1 is installed, a No. 1 spring 15 is provided inside the No. 1 oil channel 13 away from the through end. When the movable part 2 is not installed, the No. 1 spring 15 is in the initial state, and the block 14 connected to it blocks the end of the No. 2 oil channel 16 connected to the No. 1 oil channel 13 to prevent the insulating oil from flowing in. When the movable part 2 is installed, the end of the pipeline 22 squeezes the block 14 to connect the No. 2 oil channel 16 with the oil inlet hole 24 to realize oil inflow.

[0180] During the installation of the fixing part 1, in order to facilitate installation, the fixing part 1 extends into the transformer oil circuit with a screw head 11, and a hexagonal mounting block 12 is provided to facilitate workers to rotate and install it by hand or with a wrench, thereby improving installation convenience.

[0181] As a preferred embodiment of the above, Figures 3 to 4 As shown, the hexagonal mounting block 12 is provided with a No. 1 slide groove 17 and a No. 2 slide groove 18; the No. 1 slide groove 17 and the No. 2 slide groove 18 are arc-shaped grooves, the No. 1 slide groove 17 is opened on the surface of the hexagonal mounting block 12, and the No. 2 slide groove 18 is opened inside the hexagonal mounting block 12, as shown in FIG. Figure 7 and Figure 8As shown, the No. 1 slide 17 is connected to the No. 2 slide 18, and the cross-section of the hexagonal mounting block 12 along the height direction is L-shaped; a slider 23 is provided on the shell 21, and the slider 23 is an L-shaped structure. The first side of the L-shaped structure is connected to the shell 21, and the second side is perpendicular to the first side. The slider 23 matches the cross-sectional shape of the No. 1 slide 17 and the No. 2 slide 18. The slider 23 is inserted into the groove body, and the side wall of the groove body fits with the wall surface of the slider 23; a mounting groove 171 is provided at the end of the No. 1 slide 17, and the mounting groove 171 is larger than the No. 1 slide 17 in the width direction and can accommodate the first side of the slider 23. After the pipe 22 is inserted into the No. 1 oil channel 13, due to the mounting groove 171 is larger than the width of the No. 1 slide groove 17 in the width direction, so the slider 23 can be inserted from the installation groove 171 and rotated in the direction away from the installation groove 171. Since the side walls of the No. 1 slide groove 17 and the No. 2 slide groove 18 are in contact with the slider 23, the No. 1 slide groove 17 limits the first side of the slider 23, and the No. 2 slide groove 18 limits the second side of the slider 23. Therefore, the movable part 2 is fixed on the fixed part 1, and when disassembling, it is only necessary to rotate in the direction opposite to the installation direction to disassemble the movable part 2. Therefore, in daily use, it is only necessary to install the fixed part 1 during the first installation, and the movable part 2 can be disassembled separately during subsequent maintenance, reducing the workload of personnel.

[0182] During the operation of precision instruments, circuits and electronic components are generally more susceptible to damage than mechanical structures. The above-mentioned circuits and electronic components are all located in the movable part 2. Compared with the fixed part 1, the movable part 2 is disassembled more frequently. Therefore, the convenient disassembly of the movable part 2 not only saves maintenance costs, but also saves manpower.

[0183] As a preferred embodiment of the above, Figures 5 to 6 As shown, a No. 2 spring 4 is provided inside the No. 2 slide groove 18, and one end of the No. 2 spring 4 is connected to a baffle 5. After the slider 23 is inserted, it presses against the baffle 5 and applies pressure to it. The No. 2 spring 4 will generate a rightward force under pressure to squeeze the slider 23, which can effectively prevent the movable part 2 from shaking and greatly improve the stability of the device.

[0184] In order to further improve the accuracy of the collected pressure data, a sealing ring 19 is provided on the side wall of the No. 1 oil channel 13 away from the screw head 11 to prevent deviation of the measured pressure caused by oil leakage.

[0185] As a specific embodiment of the present invention, there is only one No. 2 oil channel 16, and insulating oil enters the pipeline 22 from only one direction to avoid oil collision caused by entry from multiple directions, which may lead to pressure measurement errors.

[0186] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A micro-power wireless oil pressure sensor system monitoring method, characterized in that: The micro-power wireless oil pressure sensor system monitoring method comprises the following steps: S1: Senses the oil pressure and temperature at every moment of the day and transmits the information to the data processing library; S2: The data processing library processes the received information and performs curve fitting to obtain the oil pressure function and oil temperature function; S3: Repeat the operations of step S1 and step S2 for one week, and process the data obtained in one week to obtain the average data; S4: performing curve fitting on the average data obtained in step S3 to obtain an oil pressure average function and an oil temperature average function; S5: The data processing library calculates the oil pressure and oil temperature according to theoretical conditions and obtains theoretical oil pressure data and theoretical oil temperature data; S6: Perform curve fitting on the theoretical data obtained in step S5 to obtain a theoretical function of oil pressure and a theoretical function of oil temperature; S7: The data processing library compares the oil pressure average function obtained in step S4 with the oil pressure theoretical function obtained in step S6, and the oil temperature average function obtained in step S4 with the oil temperature theoretical function obtained in step S6, to obtain the maximum and minimum differences in oil pressure and oil temperature at each moment; S8: Monitor the oil pressure and oil temperature every day and perform curve fitting on the data of the day to derive a function. Use the function to predict the oil temperature and oil pressure of the next period. Compare the predicted results with the theoretical function to obtain the difference at each moment. S9: Compare the difference value at each moment obtained in step S8 with the maximum difference and minimum difference obtained in step S7. When the difference value is greater than the maximum value in step S7 and the difference value is less than the minimum value in step S7, a feedback warning is issued. At the same time, the actual value at each moment is subtracted from the predicted value to obtain the maximum difference and minimum difference. When the maximum difference is greater than the maximum value in step S7 and the minimum difference is less than the minimum value in step S7, a feedback warning is issued.

2. The micro-power wireless oil pressure sensor system monitoring method according to claim 1, characterized in that: In step S5, according to the phase cusp theory of cavitation bubble dynamics and fluid mechanics, water vapor and oil vapor are ideal gases, and the ideal gas state equations of water vapor and oil vapor are: P g ·V=n g ·R * ·T (1) P V ·V=n V ·R * ·T (2) Where V is the bubble volume; R* is the ideal gas constant; T is the thermodynamic temperature of the ideal gas, which is a constant; n g and n V is the amount of water vapor and oil vapor; P g and P V is the partial pressure of water vapor and oil vapor; The internal pressure is composed of the partial pressure of gas and steam. The partial pressure of steam can be obtained from the quantitative relationship between water and oil vapor: P g +P V =P1+P δ (3) P1=P atm +P oil =P atm +ρ·g·h (5) P V =x·P w +y·P0 (6) Where P1 is the fluid pressure; P δ is the surface tension of the oil; δ is the surface tension coefficient; R is the radius of the bubble in the oil; ρ is the density of the current transformer oil; g is the acceleration of gravity; h is the depth of the oil; P atm is atmospheric pressure; P oil is the liquid pressure of the oil; x and y represent the percentage of water and oil respectively; W is the molecular weight of gaseous water in the oil; M w and M δ Represent the molar mass of water and oil respectively; P w is the saturated vapor pressure of water; P0 is the saturated vapor pressure of oil, and P is obtained by the following formula w 、P0: log 10 (P W )=A-(B / (T+C)) (8) ln(P0)=D+E / T (9) Among them, A, B, C, and D are constants; For a given external pressure, the above formula gives a direct relationship between pressure and radius. If the external pressure changes, the bubble will change its volume to reach a new equilibrium state. Therefore, an equation can be used to relate the determined state to the initial state to determine the state. The initial state is represented by 0. Then the initial state equation can be expressed as: P g0 +P v0 =P 10 +P δ0 (10) Among them, P g0 is the initial partial pressure of the gas; P v0 is the initial partial pressure of steam; P 10 is the pressure under certain conditions; P δ0 is the initial saturated vapor pressure of the oil; At high load rates, the upper limit of the oil temperature rise rate in the current transformer is 15°C / min, so it is considered an isothermal process and satisfies the following relationship: p g0 V0=p g V (11) Where V0 is the initial steam volume; p g0 is the initial partial pressure of the gas; p g is the partial pressure of the gas; At the same time, regardless of temperature changes, the vapor pressure does not change. Combining formulas (3), (4), (10), and (11), we can obtain: Where R0 is the initial radius of the bubble in the oil; R is the determined radius of the bubble in the oil; When the liquid pressure completely offsets the additional pressure of surface tension and the total inward pressure can no longer balance the outward pressure, the oil body will expand. The following formula is the derivative of the above formula: By solving the above equation, we can get the following equation: Among them, R C is the critical radius of bubbles in oil; By combining (12) and (14), the critical pressure value R is obtained C : Therefore, the theoretical pressure value P of the oil in the current transformer is B is the difference between the liquid pressure and the critical pressure, as shown in the following formula: Thus the theoretical value of oil pressure is obtained, and multi-time calculation is performed to obtain the theoretical oil pressure data at multiple times; Secondly, for the theoretical calculation of oil temperature, through the mass conservation equation, energy conservation equation and momentum conservation equation, the oil density does not change with time, and its differential form is: in, is the Hamiltonian operator; V is the fluid velocity vector; ρ represents the current transformer oil density; f is the unit fluid mass force; p is the fluid pressure; μ is the dynamic viscosity of the fluid; e is the internal energy of the fluid; q is the volume heat source of the fluid; k is the thermal conductivity of the fluid; S is the portion of the fluid mechanical energy converted into thermal energy under the combined action of the oil viscosity and the internal heat source of the fluid; T1 is the current transformer oil temperature; Since the relative velocity of the oil in the current transformer to the box is 0, the surface temperature of the solid box is consistent with the temperature of the oil. If the current transformer shell and the radiator shell are simplified as smooth planes, the heat dissipation process of the current transformer shell can be considered as longitudinal flat plate convection heat transfer. According to the basic theory of heat transfer, the Nusselt number N of the horizontal plate is uh and the Nusselt number λ of the vertical plate uv They are as follows: l Ra =λ Gr l Pr (24) Among them, λ Pr is the Prandtl number; λ Gr is the Grashof number; λ Ra is the Rayleigh number; g is the acceleration due to gravity; β is the corresponding fluid expansion coefficient; v is the kinematic viscosity of the fluid; L is the characteristic size; c is the specific heat capacity of the fluid; θ is the temperature difference between the wall and the external fluid; Substituting the obtained Nusselt number into formula (25) can obtain the convective heat transfer coefficient of the current transformer: Where h1 is the convective heat transfer coefficient; N ui is the Nusselt number; i is the current value; Heat flow q generated by radiation heat transfer of current transformer housing r It can be expressed by the following formula: Where ε is the surface emissivity of the current transformer housing; σ is the Stefan-Boltzmann constant, 5.67×10 -8 W / (m 2 ·K 4 );T w is the transformer casing temperature; T a is the external ambient temperature of the current transformer; The process of the thermal physical parameters of the current transformer oil changing with temperature is shown below: μ(T1)=exp(F)T1 -E (27) Where, E = 9.55 ± 0.23, F = 50.24 ± 1.33; μ(T1) is the dynamic viscosity of the current transformer; S=μ(T1)·q r (28) q=q r (29) e=h1q r (30) Substituting (28), (29), and (30) into formula (19), we obtain: According to the above formula, the current scale temperature T1 can be obtained, and the theoretical temperature value at each moment can be deduced from it.

3. The micro-power wireless oil pressure sensor system monitoring method according to claim 1, characterized in that: The specific method in step S2 is: S2.1: Monitor the oil temperature and oil pressure of oil-immersed electrical equipment through sensors; S2.2: Upload the monitoring data to the data processing library in real time through the wireless communication module; S2.3: After the data processing library completes data processing, it transmits the results to the port for the next step.

4. A micro-power wireless oil pressure sensor system device, characterized in that: A micro-power wireless oil pressure sensor system monitoring method applicable to any one of claims 1 to 3, comprising: a movable portion, a fixed portion, and a data monitoring component; The fixing portion is fixedly mounted on the transformer and includes: a No. 1 oil passage and a No. 2 oil passage. The No. 1 oil passage is arranged inside the fixing portion along the axial direction of the fixing portion and passes through one end of the fixing portion. The No. 2 oil passage is arranged inside the fixing portion and passes through the fixing portion, and connects the internal oil circuit of the transformer with the No. 1 oil passage. The movable portion is connected to the fixed portion and includes: a shell and a pipe. The shell is a hollow structure. The pipe is arranged at the center of the shell, one end of which passes through the shell and is connected to the interior thereof, and the other end is inserted into the first oil passage. An oil inlet hole is provided on the end of the pipe away from the shell, and an exhaust hole is provided at the portion of the pipe that contacts the shell. The exhaust hole passes through the pipe and the shell and is connected to the outside. The data monitoring component is arranged in the hollow area inside the shell, and includes: a sensor chip and a wireless communication module. The sensor chip is connected to the pipeline, and the wireless communication module is installed at the upper end of the interior of the shell, and is used to sense the oil pressure and oil temperature at each time of the day, and transmit the information of the oil pressure and oil temperature to the data processing library.

5. The micro-power wireless oil pressure sensor system according to claim 4, characterized in that: The wireless communication module is a Lora module, which is a low-power micro-power wireless communication module that uploads the collected monitoring data wirelessly.

6. The micro-power wireless oil pressure sensor system according to claim 4, characterized in that: A No. 1 spring is provided inside the No. 1 oil channel away from the through end, and the No. 1 spring is connected to the stopper.

7. The micro-power wireless oil pressure sensor system according to claim 4, characterized in that: The fixing portion further comprises a screw head and a hexagonal mounting block, wherein the screw head is threadedly connected to the transformer, and the hexagonal mounting block is fixedly mounted to the screw head.

8. The micro-power wireless oil pressure sensor system according to claim 7, characterized in that: The hexagonal mounting block is provided with a first slide groove and a second slide groove; The first and second chutes are arc-shaped chutes, the first chute is provided on the surface of the hexagonal mounting block, and the second chute is provided inside the hexagonal mounting block. The first and second chutes are connected, and the cross-sections of the first and second chutes along the height direction of the hexagonal mounting block are L-shaped; The housing is provided with a slider, which is an L-shaped structure, with a first side of the L-shaped structure connected to the housing and a second side perpendicular to the first side. The slider matches the cross-sectional shape of the first and second chutes, and the slider is inserted into the trough body, with the side wall of the trough body fitting against the wall surface of the slider; A mounting groove is provided at the end of the No. 1 slide groove. The mounting groove is larger than the No. 1 slide groove in the width direction and can accommodate the first side of the slider.

9. The micro-power wireless oil pressure sensor system according to claim 8, characterized in that: A No. 2 spring is provided inside the No. 2 slide groove, and one end of the No. 2 spring is connected to a baffle.

10. The micro-power wireless oil pressure sensor system according to claim 4, characterized in that: A sealing ring is provided on one end of the side wall of the No. 1 oil channel away from the spiral head.

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