Oil-immersed casing pressure calculation method and system

Abstract

The invention relates to the technical field of transformer monitoring, and discloses a method and system for calculating the pressure of an oil-immersed bushing. The method performs geometric modeling on the geometric structure of the oil-immersed bushing, uses partial differential equations to perform numerical simulation on the physical fields of various structures of the bushing geometric model, and determines the distribution of various physical fields at the oil-gas interface in the bushing under steady state, thereby improving the calculation accuracy, and actually considering the change in air side pressure caused by the oil level change after the temperature inside the bushing changes. The transformer oil mass conservation principle is used to determine the transformer oil level change height according to the mass of the transformer oil at the oil-gas interface in the bushing before and after the steady state change, thereby more accurately calculating the transformer oil pressure after the transformer oil level changes.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer monitoring, and in particular to a method and system for calculating oil-immersed bushing pressure. Background Art

[0002] During the operation of oil-immersed bushings under load, as the temperature of the bushing changes, the internal pressure of the bushing is not at a constant pressure, but changes with the temperature. When the internal pressure of the bushing is abnormal, it may threaten the normal operation of the bushing or even the transformer. Therefore, it is necessary to calculate the internal pressure value of the oil-immersed bushing under different load changes, and to warn or repair the abnormal values ​​that may appear under different working conditions to avoid failure or damage of the bushing or transformer.

[0003] The existing pressure calculation of oil-immersed bushings is mostly based on solving partial differential equations under a constant liquid level. Based on finite element simulation software, the coupling simulation of the flow field and temperature field inside the bushing can be realized to calculate the pressure change characteristics of the transformer oil inside the bushing under non-isothermal flow conditions. The fluid boundary set in this type of method during calculation is fixed, but the oil level change is one of the important factors of pressure change, which makes it difficult to accurately calculate the internal pressure of the oil-immersed bushing. Summary of the invention

[0004] The invention provides a method and system for calculating the pressure of an oil-immersed casing, which solves the technical problem of poor accuracy of the internal pressure of the oil-immersed casing.

[0005] In view of this, a first aspect of the present invention provides a method for calculating oil-immersed casing pressure, comprising:

[0006] Performing geometric modeling on the geometric structure of the oil-immersed casing to obtain a casing geometric model;

[0007] Numerically simulating the physical fields of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation;

[0008] The partial differential equations are solved for the numerical simulation results to determine the distribution of various physical fields at the oil-gas interface in the casing under steady state;

[0009] Determine the quality of transformer oil at the oil-gas interface in a steady state according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing;

[0010] Based on the transformer oil mass conservation principle, the transformer oil level change height is determined according to the transformer oil mass before and after the steady-state change of the oil-gas interface in the bushing;

[0011] The pressure of the transformer oil after the transformer oil level changes is determined according to the transformer oil level change height, the air side pressure, and the density of the transformer oil corresponding to the transformer oil level change height.

[0012] Preferably, the structure of the casing geometric model includes a non-fluid structure and a fluid structure; the step of numerically simulating the physical field of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation comprises:

[0013] By setting partial differential equations, numerical simulations are respectively performed on the heat conduction process of the non-fluid structure of the bushing geometric model, the heat conduction process of the fluid structure, the flow process of the fluid structure, the heat conduction process of the contact surface between the bushing and the external air, and the heat conduction process of the contact surface between the inner part of the bushing riser and the transformer oil;

[0014] The boundary conditions of the partial differential equation are set, wherein the boundary conditions include that the initial value of the temperature of the bushing is a fixed value, the initial values ​​of the velocity field and the pressure field of the fluid structure are both zero, the convective heat transfer coefficient and the temperature of the contact surface between the bushing and the external air are both fixed values, the heat transfer coefficient and the temperature of the contact surface between the inner part of the bushing riser and the transformer oil are both fixed values, and the steady-state pressure of the air domain is normal pressure.

[0015] Preferably, the step of determining the quality of the transformer oil at the oil-gas interface in a steady state according to the distribution of each physical field at the oil-gas interface in a steady state in the bushing comprises:

[0016] The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​in the bushing in a steady state, so as to obtain the mass of the transformer oil at the oil-gas interface in a steady state.

[0017] Preferably, the step of determining the transformer oil level change height based on the transformer oil mass conservation principle and according to the mass of the transformer oil at the oil-gas interface in the bushing before and after the steady-state change comprises:

[0018] The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​after the steady-state change of the bushing, so as to obtain the mass of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing;

[0019] Based on the transformer oil mass conservation principle, the transformer oil level change height is determined by the mass of the transformer oil at the oil-gas interface before and after the steady-state change of the bushing, wherein the expression of the transformer oil mass conservation principle is:

[0020]

[0021] In the formula, Indicates the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the quality of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing. Indicates the change in transformer oil level. Indicates the height of the oil-gas interface before the casing changes to a steady state. Indicates the density of the top layer of transformer oil after the temperature rises, It represents the bottom area where the top layer of transformer oil rises after the temperature rises, and d is the differential operation symbol.

[0022] Preferably, the method further comprises:

[0023] The pressure of the transformer oil after the transformer oil level changes is calculated by the following formula according to the transformer oil level change height, the air side pressure and the density of the transformer oil corresponding to the transformer oil level change height. The pressure of the transformer oil after the transformer oil level changes is:

[0024]

[0025] In the formula, is the transformer oil pressure after the transformer oil level changes, is the air side pressure, is the height of the transformer oil level after the change, , is the density of the transformer oil at the oil-gas interface after the transformer oil level changes, is the acceleration due to gravity, d is the differential operation symbol, Indicates the height of the oil-gas interface before the casing changes to a steady state.

[0026] Preferably, the method further comprises:

[0027] The volume of air is integrated by the density of air at multiple different temperature values ​​after the casing changes steadily, so as to obtain the mass of air at the oil-gas interface in the casing in the casing steady state;

[0028] According to the mass of air at the oil-gas interface in the casing under the steady state, the air density at the oil-gas interface after the casing steady state changes is calculated by the following formula. The air density at the oil-gas interface after the casing steady state changes is:

[0029]

[0030] In the formula, is the air density at the oil-gas interface after the casing changes steadily, is the mass of air at the oil-gas interface in the casing under steady state, is the volume of the air side at the oil-gas interface in the casing under steady state;

[0031] The air side pressure is determined by the air density at the oil-gas interface after the casing steady-state change through the correlation expression between the air density and the air side pressure.

[0032] In a second aspect, the present invention further provides an oil-immersed casing pressure calculation system, comprising:

[0033] A geometric modeling module is used to perform geometric modeling on the geometric structure of the oil-immersed casing to obtain a casing geometric model;

[0034] A numerical simulation module, used for numerically simulating the physical field of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation;

[0035] The equation solving module is used to solve the partial differential equations of the numerical simulation results and determine the distribution of various physical fields at the oil-gas interface in the casing under steady state;

[0036] The oil quality calculation module is used to determine the quality of the transformer oil at the oil-gas interface in a steady state according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing;

[0037] The oil level height calculation module is used to determine the transformer oil level change height based on the transformer oil mass conservation principle and the transformer oil mass before and after the oil-gas interface in the bushing changes in a steady state;

[0038] The pressure calculation module is used to determine the pressure of the transformer oil after the transformer oil level changes according to the transformer oil level change height, the air side pressure and the density of the transformer oil corresponding to the transformer oil level change height.

[0039] In a third aspect, the present invention further provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the oil-immersed casing pressure calculation method as described in the first aspect.

[0040] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed, the steps of the oil-immersed casing pressure calculation method as described in the first aspect are implemented.

[0041] In a fifth aspect, the present invention further provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the oil-immersed casing pressure calculation method as described in the first aspect.

[0042] It can be seen from the above technical solutions that the present invention has the following advantages:

[0043] The present invention performs geometric modeling on the geometric structure of the oil-immersed bushing, uses partial differential equations to perform numerical simulation on the physical fields of various structures of the bushing geometric model, and determines the distribution of various physical fields at the oil-gas interface in the bushing under steady state, thereby improving the calculation accuracy, and actually considers the change in air-side pressure caused by the oil level change after the temperature inside the bushing changes. Through the transformer oil mass conservation principle, the transformer oil level change height is determined according to the mass of the transformer oil at the oil-gas interface in the bushing before and after the steady-state change, thereby more accurately calculating the transformer oil pressure after the transformer oil level change. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A flow chart of a method for calculating oil-immersed casing pressure provided by an embodiment of the present invention;

[0045] Figure 2a A schematic diagram of the head structure of an oil-immersed transformer bushing provided in an embodiment of the present invention;

[0046] Figure 2b A schematic diagram of the middle structure of an oil-immersed transformer bushing provided in an embodiment of the present invention;

[0047] Figure 2c A schematic diagram of the bottom structure of an oil-immersed transformer bushing provided in an embodiment of the present invention;

[0048] Figure 3a A schematic diagram of the heat exchange boundary between the casing and the air contact portion provided in an embodiment of the present invention;

[0049] Figure 3b A schematic diagram of the inner part of the bushing riser and the transformer oil boundary provided by an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of the oil-gas interface provided by an embodiment of the present invention;

[0051] Figure 5 A schematic diagram of the structure of an oil-immersed casing pressure calculation system provided by an embodiment of the present invention;

[0052] Figure 6 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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, 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.

[0054] like Figure 1 As shown, a method for calculating the pressure of an oil-immersed casing is provided.

[0055] This embodiment is applicable to the case of calculating the oil-immersed casing pressure. The method can be executed by an oil-immersed casing pressure calculation device. The oil-immersed casing pressure calculation device can be implemented in the form of hardware and / or software. The oil-immersed casing pressure calculation device can be configured in a computer device.

[0056] An oil-immersed casing pressure calculation method provided in an embodiment of the present invention includes steps S1 to S6:

[0057] Step S1, geometric modeling is performed on the geometric structure of the oil-immersed casing to obtain a casing geometric model.

[0058] The geometric structure of the oil-immersed bushing is determined according to the actual structure of the oil-immersed bushing. For example, a 126kV / 630A oil-immersed transformer bushing produced by a bushing manufacturer is used as an example. Figure 2a~2c As shown, the oil-immersed transformer bushing is divided into a head, a middle and a bottom structure in sequence.

[0059] For the head structure of oil-immersed transformer bushing, such as Figure 2a As shown, the head structure of the oil-immersed transformer bushing includes a general cap, a cable connector, an oil pillow and a cover plate, air, a compression nut, a cable, a paper tube and transformer oil.

[0060] For the middle structure of oil-immersed transformer bushing, such as Figure 2b As shown, the middle structure of the oil-immersed transformer bushing includes an upper insulator and a flange.

[0061] For the bottom structure of oil-immersed transformer bushing, such as Figure 2c As shown, the bottom structure of the oil-immersed transformer bushing includes a capacitor core, a lower insulator and a bottom nut.

[0062] For the materials of each component of the bushing, set the material property parameters and divide the mesh. The solid (non-fluid) material parameter settings are shown in Table 1. Solid refers to all parts other than fluid (air, transformer oil), specifically including the bushing flange, oil pillow, rolled tube, metal guide rod, capacitor core and other solid parts. The fluid material parameter expression is shown in Table 2. Since the change in oil height is caused by the thermal expansion and contraction of transformer oil and air, the fluid material parameters are related to temperature T and pressure pA.

[0063] Table 1 Solid material parameters

[0064]

[0065] Table 2 Fluid material parameters

[0066]

[0067] Step S2: numerically simulate the physical fields of each structure of the casing geometric model by setting partial differential equations and boundary conditions of the partial differential equations.

[0068] The structure of the casing geometric model includes a non-fluid structure and a fluid structure. Specifically, step S2 includes:

[0069] Step S201, by setting partial differential equations, numerical simulation is performed on the heat conduction process of the non-fluid structure of the bushing geometric model, the heat conduction process of the fluid structure, the flow process of the fluid structure, the heat conduction process of the contact surface between the bushing and the external air, and the heat conduction process of the contact surface between the inner part of the bushing riser and the transformer oil.

[0070] The partial differential equation satisfied by the heat conduction process of non-fluid structure is:

[0071]

[0072] In the formula, is the density of the structural material, is the specific heat capacity of the solid, is the thermal conductivity of the solid, Q is the heat generation rate of the heat source, is the temperature, For time, is the Del operator, is the heat transfer vector;

[0073] The partial differential equation satisfied by the heat conduction process of the fluid structure is:

[0074]

[0075] Where u represents the velocity vector of the fluid;

[0076] The partial differential equation satisfied by the flow process of the fluid structure is:

[0077]

[0078] Where p is the absolute pressure of the fluid (unit: Pa), μ is the dynamic viscosity of the fluid (unit: Pa•s), I is the unit vector, and F is the external force vector acting on the fluid (unit: N).

[0079] The contact surface between the bushing and the external air and the transformer oil in the riser should satisfy the following heat convection equation:

[0080]

[0081] In the formula, n represents the normal vector of the contact surface, and q0 represents the heat per unit area caused by the temperature difference between the inside and outside of the contact surface (unit: W / m 2 ), q represents the heat transfer vector (unit W / m 2 ), Text represents the external temperature (unit K), h represents the heat transfer coefficient (unit W / (m 2 K)).

[0082] Step S202, setting boundary conditions of the partial differential equation, the boundary conditions include that the initial value of the temperature of the bushing is a fixed value, the initial values ​​of the velocity field and the pressure field of the fluid structure are both zero, the convective heat transfer coefficient and the temperature of the contact surface between the bushing and the external air are both fixed values, the heat transfer coefficient and the temperature of the contact surface between the inner part of the bushing riser and the transformer oil are both fixed values, and the steady-state pressure of the air domain is normal pressure.

[0083] For example, given the initial temperature value of each finite element of the casing, the given initial temperature value is 293.15K for the entire casing, we have:

[0084]

[0085] For the fluid domain, the initial values ​​of the velocity field and pressure field are both 0, and we have:

[0086]

[0087] like Figure 3a As shown in the figure, for the heat transfer boundary of the part where the casing contacts the air, the convection heat transfer coefficient is set to 5 W / (m 2 K), ambient temperature 323.15K; Figure 3b As shown in the figure, the heat transfer coefficient between the inner part of the bushing riser and the transformer oil boundary is 100 W / (m 2 K), ambient temperature 363.15K.

[0088] The steady-state pressure in the air domain is normal pressure, that is:

[0089] .

[0090] Step S3, solving partial differential equations for the numerical simulation results to determine the distribution of various physical fields at the oil-gas interface in the casing under steady state.

[0091] There is no limitation on the setting of the oil-gas interface in the casing under steady state. Figure 2c The leftmost point at the bottom of the mid-through cable is the coordinate origin, and the liquid level at a height of 2280 mm is the oil-gas interface in a steady state. Figure 4 shown.

[0092] For the calculation area with rapid numerical changes and large range, the method of solving partial differential equations is used for calculation. The distribution of various physical fields at the oil-gas interface in the casing under steady state includes oil temperature distribution, oil density distribution, air temperature distribution and air density distribution.

[0093] Step S4, determining the quality of the transformer oil at the oil-gas interface in a steady state according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing.

[0094] Specifically, the volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​in the bushing in a steady state, so as to obtain the mass of the transformer oil at the oil-gas interface in a steady state.

[0095] That is, the mass of transformer oil at the oil-gas interface in a steady state is:

[0096]

[0097] In the formula, is the quality of transformer oil at the oil-gas interface in a steady state, is the density of transformer oil at the oil-gas interface in a steady state, is the volume of transformer oil at the oil-gas interface in a steady state.

[0098] Step S5: Based on the transformer oil mass conservation principle, the transformer oil level change height is determined according to the mass of the transformer oil at the oil-gas interface in the bushing before and after the steady-state change.

[0099] It should be noted that the steady-state of the bushing refers to the situation where the load remains unchanged, the heating power of the conductive rod remains unchanged, and the oil level of the transformer remains unchanged. The change of the steady-state of the bushing refers to the situation where the load changes, the heating power of the conductive rod changes, and the oil level of the transformer changes.

[0100] The embodiment of the present invention takes into account the transformer oil mass conservation principle. Although the transformer oil level change height of the oil-gas interface in the bushing changes before and after the steady-state change due to the increase in temperature and density, in order to conserve the transformer oil mass, it is approximately considered that the top density of the transformer oil is a constant value, that is, the transformer oil mass should be conserved and unchanged. Therefore, for a small range calculation area with a small value change, an approximate constant value method is used to perform approximate numerical calculation, thereby improving the calculation accuracy and calculation speed.

[0101] Based on this, step S5 includes steps S501-S502:

[0102] Step S501, integrating the volume of the transformer oil by the density of the transformer oil at a plurality of different temperature values ​​after the steady-state change of the bushing, and obtaining the mass of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing.

[0103] Among them, the mass of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing is:

[0104]

[0105] In the formula, It indicates the quality of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing, wherein the oil-gas interface in the bushing after the steady-state change of the bushing is consistent with the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the density of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing, It indicates the volume of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing.

[0106] Step S502: Based on the transformer oil mass conservation principle, the transformer oil level change height is determined by the mass of the transformer oil at the oil-gas interface before and after the bushing steady-state change, wherein the transformer oil mass conservation principle is expressed as:

[0107]

[0108] In the formula, Indicates the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the change in transformer oil level. Indicates the height of the oil-gas interface before the casing changes to a steady state. Indicates the density of the top layer of transformer oil after the temperature rises, It represents the bottom area where the top layer of transformer oil rises after the temperature rises, and d is the differential operation symbol.

[0109] Among them, the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing That is, the quality of the transformer oil at the oil-gas interface in a steady state.

[0110] Step S6: determining the pressure of the transformer oil after the transformer oil level changes according to the transformer oil level change height, the air side pressure, and the density of the transformer oil corresponding to the transformer oil level change height.

[0111] Specifically, the pressure of the transformer oil after the transformer oil level changes is calculated by the following formula according to the transformer oil level change height, the air side pressure and the transformer oil density corresponding to the transformer oil level change height. The pressure of the transformer oil after the transformer oil level changes is:

[0112]

[0113] In the formula, is the transformer oil pressure after the transformer oil level changes, is the air side pressure, is the height of the transformer oil level after the change, , is the density of the transformer oil at the oil-gas interface after the transformer oil level changes, is the acceleration due to gravity, d is the differential operation symbol, Indicates the height of the oil-gas interface before the casing changes to a steady state.

[0114] Since the air side pressure is unknown, in some embodiments, the method further includes steps S61 to S63:

[0115] Step S61, integrating the volume of air by the density of air at a plurality of different temperature values ​​after the casing changes in a steady state, and obtaining the mass of air at the oil-gas interface in the casing in a steady state.

[0116] Among them, the mass of air at the oil-gas interface in the casing under the steady state is:

[0117]

[0118] In the formula, is the mass of air at the oil-gas interface in the casing under steady state, is the air density at the oil-gas interface in the casing under the steady state, It is the air volume at the oil-gas interface in the casing under the steady state.

[0119] Step S62: Calculate the air density at the oil-gas interface after the casing steady-state changes according to the mass of air at the oil-gas interface in the casing in the steady state by the following formula. The air density at the oil-gas interface after the casing steady-state changes is:

[0120]

[0121] In the formula, is the air density at the oil-gas interface after the casing changes steadily, is the mass of air at the oil-gas interface in the casing under steady state, It is the volume of the air side at the oil-gas interface in the casing under steady state.

[0122] Among them, it is approximately assumed that the air temperature and density in the oil pillow are constant.

[0123] Step S63: Determine the air side pressure according to the air density at the oil-gas interface after the casing steady-state change by using the correlation expression between the air density and the air side pressure.

[0124] Among them, the correlation expression between air density and air side pressure is:

[0125] =p air2 0.02897 / 8.314 / T air2

[0126] In the formula, p air2 is the air side pressure, T air2 is the air side temperature.

[0127] It should be noted that the present invention performs geometric modeling on the geometric structure of the oil-immersed bushing, uses partial differential equations to perform numerical simulation on the physical fields of each structure of the bushing geometric model, and determines the distribution of each physical field at the oil-gas interface in the bushing under steady state, thereby improving the calculation accuracy and actually considering the change in air side pressure caused by the oil level change after the temperature inside the bushing changes. Through the transformer oil mass conservation principle, the transformer oil level change height is determined according to the mass of the transformer oil at the oil-gas interface in the bushing before and after the steady-state change, thereby more accurately calculating the transformer oil pressure after the transformer oil level change.

[0128] Based on the same inventive concept, an embodiment of the present application further provides an oil-immersed casing pressure calculation system for implementing the above-mentioned oil-immersed casing pressure calculation.

[0129] The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more embodiments of the oil-immersed casing pressure calculation system provided below can refer to the limitations on the oil-immersed casing pressure calculation method above, and will not be repeated here.

[0130] like Figure 5 As shown, an oil-immersed casing pressure calculation system provided by an embodiment of the present invention includes:

[0131] A geometric modeling module 100 is used to perform geometric modeling on the geometric structure of the oil-immersed casing to obtain a casing geometric model;

[0132] The numerical simulation module 200 is used to perform numerical simulation on the physical fields of each structure of the casing geometric model by setting partial differential equations and boundary conditions of the partial differential equations;

[0133] The equation solving module 300 is used to solve the partial differential equations for the numerical simulation results to determine the distribution of various physical fields at the oil-gas interface in the casing under steady state;

[0134] The oil quality calculation module 400 is used to determine the quality of the transformer oil at the oil-gas interface in a steady state according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing;

[0135] The oil level height calculation module 500 is used to determine the transformer oil level change height based on the transformer oil mass conservation principle and according to the transformer oil mass before and after the oil-gas interface in the bushing changes in a steady state;

[0136] The pressure calculation module 600 is used to determine the pressure of the transformer oil after the transformer oil level changes according to the transformer oil level change height, the air side pressure and the density of the transformer oil corresponding to the transformer oil level change height.

[0137] In some embodiments, the structure of the bushing geometric model includes a non-fluid structure and a fluid structure. The numerical simulation module 200 is specifically used to numerically simulate the heat conduction process of the non-fluid structure of the bushing geometric model, the heat conduction process of the fluid structure, the flow process of the fluid structure, the heat conduction process of the contact surface between the bushing and the external air, and the heat conduction process of the contact surface between the inner part of the bushing riser and the transformer oil by setting partial differential equations; it is also used to set the boundary conditions of the partial differential equations, the boundary conditions include that the initial value of the bushing temperature is a fixed value, the initial values ​​of the velocity field and the pressure field of the fluid structure are both zero, the convective heat transfer coefficient and temperature of the contact surface between the bushing and the external air are both fixed values, the heat transfer coefficient and temperature of the contact surface between the inner part of the bushing riser and the transformer oil are both fixed values, and the air domain steady-state pressure is normal pressure.

[0138] In some embodiments, the oil quality calculation module 400 is used to integrate the volume of the transformer oil through the density of the transformer oil at multiple different temperature values ​​in the bushing in a steady state to obtain the mass of the transformer oil at the oil-gas interface in a steady state.

[0139] In some embodiments, the oil level height calculation module 500 is specifically used to integrate the volume of the transformer oil by the density of the transformer oil at multiple different temperature values ​​after the steady-state change of the bushing, so as to obtain the mass of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing; based on the transformer oil mass conservation principle, the transformer oil level change height is determined by the mass of the transformer oil at the oil-gas interface before and after the steady-state change of the bushing, wherein the expression of the transformer oil mass conservation principle is:

[0140]

[0141] In the formula, Indicates the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the quality of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing. Indicates the change in transformer oil level. Indicates the height of the oil-gas interface before the casing changes to a steady state. Indicates the density of the top layer of transformer oil after the temperature rises, It indicates the bottom area where the top layer of transformer oil rises after the temperature rises.

[0142] In some embodiments, the pressure calculation module 600 is specifically used to calculate the pressure of the transformer oil after the transformer oil level changes according to the transformer oil level change height, the air side pressure, and the density of the transformer oil corresponding to the transformer oil level change height by the following formula. The pressure of the transformer oil after the transformer oil level changes is:

[0143]

[0144] In the formula, is the transformer oil pressure after the transformer oil level changes, is the air side pressure, is the height of the transformer oil level after the change, , is the density of the transformer oil at the oil-gas interface after the transformer oil level changes, is the acceleration due to gravity.

[0145] In some specific embodiments, the system further includes:

[0146] The air quality calculation module is used to integrate the volume of air by the density of air at multiple different temperature values ​​after the casing changes steadily, so as to obtain the mass of air at the oil-gas interface in the casing in the casing steady state;

[0147] The air density calculation module is used to calculate the air density at the oil-gas interface after the casing steady-state changes according to the mass of the air at the oil-gas interface in the casing under the steady-state of the casing by the following formula. The air density at the oil-gas interface after the casing steady-state changes is:

[0148]

[0149] In the formula, is the air density at the oil-gas interface after the casing changes steadily, is the mass of air at the oil-gas interface in the casing under steady state, is the volume of the air side at the oil-gas interface in the casing under steady state;

[0150] The air pressure calculation module is used to determine the air side pressure according to the air density at the oil-gas interface after the casing steady-state change through the correlation expression between the air density and the air side pressure.

[0151] like Figure 6 As shown, the present invention also provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, when the computer program is executed by the processor 30, the processor 30 executes the steps of the oil immersed casing pressure calculation method in any of the above embodiments.

[0152] The present invention further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed, the steps of the oil-immersed casing pressure calculation method in any of the above embodiments are implemented.

[0153] The present invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the oil-immersed casing pressure calculation method in any of the above embodiments.

[0154] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0155] In several embodiments provided by the present invention, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and a part of a module, a program segment or a code includes one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0156] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components 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 an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0157] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0158] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0159] If the integrated unit is implemented in the form of a software functional unit 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 executing all or part of the steps of the method described in each embodiment of the present invention through a computer device (which can be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk and other media that can store program codes.

[0160] 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 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 oil-immersed casing pressure, characterized in that: include: Performing geometric modeling on the geometric structure of the oil-immersed casing to obtain a casing geometric model; Numerically simulating the physical fields of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation; The structure of the casing geometric model includes a non-fluid structure and a fluid structure; the step of numerically simulating the physical field of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation includes: By setting partial differential equations, numerical simulations are respectively performed on the heat conduction process of the non-fluid structure of the bushing geometric model, the heat conduction process of the fluid structure, the flow process of the fluid structure, the heat conduction process of the contact surface between the bushing and the external air, and the heat conduction process of the contact surface between the inner part of the bushing riser and the transformer oil; The boundary conditions of the partial differential equation are set, wherein the boundary conditions include that the initial value of the temperature of the bushing is a fixed value, the initial values ​​of the velocity field and the pressure field of the fluid structure are both zero, the convective heat transfer coefficient and the temperature of the contact surface between the bushing and the external air are both fixed values, the heat transfer coefficient and the temperature of the contact surface between the inner part of the bushing riser and the transformer oil are both fixed values, and the steady-state pressure of the air domain is normal pressure; The partial differential equations are solved for the numerical simulation results to determine the distribution of various physical fields at the oil-gas interface in the casing under steady state; The quality of the transformer oil at the oil-gas interface in a steady state is determined according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing, including: The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​in the steady state in the bushing to obtain the mass of the transformer oil at the oil-gas interface in the steady state; Based on the transformer oil mass conservation principle, the transformer oil level change height is determined according to the transformer oil mass before and after the steady-state change of the oil-gas interface in the bushing, including: The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​after the steady-state change of the bushing, so as to obtain the mass of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing; Based on the transformer oil mass conservation principle, the transformer oil level change height is determined by the mass of the transformer oil at the oil-gas interface before and after the steady-state change of the bushing, wherein the expression of the transformer oil mass conservation principle is: ； In the formula, Indicates the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the quality of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing. Indicates the change in transformer oil level. Indicates the height of the oil-gas interface before the casing changes to a steady state. Indicates the density of the top layer of transformer oil after the temperature rises, It represents the bottom area where the top layer of transformer oil rises after the temperature rises, and d is the differential operation symbol; The pressure of the transformer oil after the transformer oil level changes is determined according to the transformer oil level change height, the air side pressure, and the density of the transformer oil corresponding to the transformer oil level change height.

2. The oil-immersed casing pressure calculation method according to claim 1, characterized in that: Also includes: The pressure of the transformer oil after the transformer oil level changes is calculated by the following formula according to the transformer oil level change height, the air side pressure and the density of the transformer oil corresponding to the transformer oil level change height. The pressure of the transformer oil after the transformer oil level changes is: ； In the formula, is the transformer oil pressure after the transformer oil level changes, is the air side pressure, is the height of the transformer oil level after the change, , is the density of the transformer oil at the oil-gas interface after the transformer oil level changes, is the acceleration due to gravity, d is the differential operation symbol, Indicates the height of the oil-gas interface before the casing changes to a steady state.

3. The oil-immersed casing pressure calculation method according to claim 2, characterized in that: Also includes: The volume of air is integrated by the density of air at multiple different temperature values ​​after the casing changes steadily, so as to obtain the mass of air at the oil-gas interface in the casing in the casing steady state; According to the mass of air at the oil-gas interface in the casing under the steady state, the air density at the oil-gas interface after the casing steady state changes is calculated by the following formula. The air density at the oil-gas interface after the casing steady state changes is: ； In the formula, is the air density at the oil-gas interface after the casing changes steadily, is the mass of air at the oil-gas interface in the casing under steady state, is the volume of the air side at the oil-gas interface in the casing under steady state; The air side pressure is determined by the air density at the oil-gas interface after the casing steady-state change through the correlation expression between the air density and the air side pressure.

4. An oil-immersed casing pressure calculation system, characterized in that: include: A geometric modeling module is used to perform geometric modeling on the geometric structure of the oil-immersed casing to obtain a casing geometric model; A numerical simulation module, used for numerically simulating the physical field of each structure of the casing geometric model by setting a partial differential equation and boundary conditions of the partial differential equation; The structure of the casing geometric model includes a non-fluid structure and a fluid structure; the numerical simulation of the physical field of each structure of the casing geometric model by setting a partial differential equation and a boundary condition of the partial differential equation includes: By setting partial differential equations, numerical simulations are respectively performed on the heat conduction process of the non-fluid structure of the bushing geometric model, the heat conduction process of the fluid structure, the flow process of the fluid structure, the heat conduction process of the contact surface between the bushing and the external air, and the heat conduction process of the contact surface between the inner part of the bushing riser and the transformer oil; The boundary conditions of the partial differential equation are set, wherein the boundary conditions include that the initial value of the temperature of the bushing is a fixed value, the initial values ​​of the velocity field and the pressure field of the fluid structure are both zero, the convective heat transfer coefficient and the temperature of the contact surface between the bushing and the external air are both fixed values, the heat transfer coefficient and the temperature of the contact surface between the inner part of the bushing riser and the transformer oil are both fixed values, and the steady-state pressure of the air domain is normal pressure; The equation solving module is used to solve the partial differential equations of the numerical simulation results and determine the distribution of various physical fields at the oil-gas interface in the casing under steady state; The oil quality calculation module is used to determine the quality of the transformer oil at the oil-gas interface in a steady state according to the distribution of various physical fields at the oil-gas interface in a steady state in the bushing, including: The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​in the steady state in the bushing to obtain the mass of the transformer oil at the oil-gas interface in the steady state; The oil level height calculation module is used to determine the transformer oil level change height based on the transformer oil mass conservation principle and according to the transformer oil mass before and after the steady-state change of the oil-gas interface in the bushing, including: The volume of the transformer oil is integrated by the density of the transformer oil at multiple different temperature values ​​after the steady-state change of the bushing, so as to obtain the mass of the transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing; Based on the transformer oil mass conservation principle, the transformer oil level change height is determined by the mass of the transformer oil at the oil-gas interface before and after the steady-state change of the bushing, wherein the expression of the transformer oil mass conservation principle is: ； In the formula, Indicates the quality of transformer oil at the oil-gas interface in the bushing before the steady-state change of the bushing. Indicates the quality of transformer oil at the oil-gas interface in the bushing after the steady-state change of the bushing. Indicates the change in transformer oil level. Indicates the height of the oil-gas interface before the casing changes to a steady state. Indicates the density of the top layer of transformer oil after the temperature rises, It represents the bottom area where the top layer of transformer oil rises after the temperature rises, and d is the differential operation symbol; The pressure calculation module is used to determine the pressure of the transformer oil after the transformer oil level changes according to the transformer oil level change height, the air side pressure and the density of the transformer oil corresponding to the transformer oil level change height.

5. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the oil-immersed casing pressure calculation method according to any one of claims 1 to 3.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the oil-immersed casing pressure calculation method according to any one of claims 1 to 3 are implemented.

7. A computer program product, characterized in that The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the steps of the oil-immersed casing pressure calculation method according to any one of claims 1 to 3.

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