A synthetic ester superheat fault gas production simulation device and method based on high-frequency induction heating

Abstract

The application discloses a kind of based on high-frequency induction heating's synthetic ester overheating fault gas production simulation device and method, belong to electric power equipment insulating medium technical field, the device includes: transparent reaction container of containing synthetic ester oil, sealing flange being arranged at the top of container, copper bar, high-frequency induction coil, inner layer insulating paper, outer layer insulating paper and optical fiber temperature sensor.Copper bar vertically penetrates sealing flange and is fixed by its upper portion, lower portion is immersed in synthetic ester oil, copper bar lower outer side is successively wrapped with inner layer insulating paper and outer layer insulating paper, optical fiber temperature sensor is arranged between two layers of insulating paper, copper bar and two layers of insulating paper jointly constitute simulation heating module, high-frequency induction coil is in non-contact form and is surrounded outside simulation heating module.By the present application, the problem that existing technology cannot simulate local superhigh temperature overheating can be solved.

Description

Technical Field

[0001] This invention relates to the technical field of insulating media for power equipment, and more particularly to a device and method for simulating gas generation during overheating faults of synthetic esters based on high-frequency induction heating. Background Technology

[0002] With the widespread application of high-frequency electromagnetic equipment and power insulation equipment, synthetic ester oil, as the core insulating heat exchange medium, is increasingly posing a risk of equipment failure due to its high-temperature overheating and gas generation. Therefore, conducting accurate simulation tests of synthetic ester oil overheating and gas generation failures is of great significance for assessing the safe operation of equipment.

[0003] Existing technologies for simulating gas production failures due to overheating of synthetic ester oil generally employ traditional overall heating methods such as resistance heating and heating jackets. These traditional heating platforms suffer from severe thermal balance bottlenecks: the heating element has low power density, and the input heat and oil heat dissipation reach thermal equilibrium prematurely at lower temperatures. This makes it impossible to create the localized ultra-high temperature overheating conditions that occur during actual equipment operation, and it is difficult to trigger the actual high-temperature cracking and gas production behavior of synthetic ester oil. Consequently, the simulation of the failure is extremely poor. Summary of the Invention

[0004] This invention provides a device and method for simulating gas generation from overheating faults in synthetic esters based on high-frequency induction heating. The device can solve the problem that existing technologies cannot simulate local ultra-high temperature overheating.

[0005] An embodiment of the present invention provides a synthetic ester overheating fault gas generation simulation device based on high frequency induction heating, comprising: a transparent reaction vessel containing synthetic ester oil, a sealing flange disposed on the top of the transparent reaction vessel, a copper rod, a high frequency induction coil, an inner layer of insulating paper, an outer layer of insulating paper, and an optical fiber temperature sensor. The copper rod passes vertically through the sealing flange, and the upper part of the copper rod is fixed by the sealing flange. The lower part of the copper rod is immersed in synthetic ester oil. The outer surface of the lower part of the copper rod is wrapped with the inner layer of insulating paper and the outer layer of insulating paper. An optical fiber temperature sensor is set between the inner layer of insulating paper and the outer layer of insulating paper. The copper rod, the inner layer of insulating paper and the outer layer of insulating paper constitute a simulated heating module. The high-frequency induction coil is arranged in a non-contact manner around the outer periphery of the simulated heating module.

[0006] Furthermore, it also includes: an oil extraction valve; The oil extraction valve is installed at a predetermined distance from the bottom of the transparent reaction vessel.

[0007] Following that, it also includes: an oil injection valve, a pressure gauge, and a pressure relief valve; The oil injection valve, pressure gauge, and pressure relief valve are all installed on the top of the sealing flange.

[0008] Furthermore, the synthetic ester oil in the transparent reaction vessel occupies four-fifths of the volume of the transparent reaction vessel.

[0009] An embodiment of the present invention also provides a method for simulating gas generation in synthetic ester overheating faults based on high-frequency induction heating, comprising: Obtain the excitation parameters of the high-frequency induction coil, the physical and geometric parameters of the copper rod, the parameters of the insulating paper, and the state parameters of the synthetic ester oil; The high-frequency input power is determined based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod. Based on the state parameters of the synthetic ester oil, the equivalent total heat capacity of the synthetic ester oil is determined; Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, the maximum allowable heating time for simulating gas generation during overheating faults of synthetic ester oil is calculated. The high-frequency induction coil is activated based on the excitation parameters to heat the synthetic ester oil. The simulation ends when the heating time reaches the maximum allowable heating time.

[0010] Furthermore, it also includes: During the heating process, the real-time local temperature of the synthetic ester oil after heating is collected by a fiber optic temperature sensor. The simulation ends when the heating duration is found to be less than the maximum allowable heating duration, but the real-time local temperature reaches the preset target local temperature.

[0011] Furthermore, the excitation parameters of the high-frequency induction coil include the number of turns of the high-frequency induction coil, the amplitude of the high-frequency alternating current supplied to the high-frequency induction coil, the frequency of the high-frequency alternating current supplied to the high-frequency induction coil, and the heating length of the high-frequency induction coil on the copper rod; the physical geometric parameters of the copper rod include the conductivity of the copper rod, the permeability of the copper rod, and the radius of the copper rod. The high-frequency input power is determined based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod, including: The magnetomotive force amplitude of the high-frequency induction coil is determined based on the number of turns and the amplitude of the high-frequency alternating current. The amplitude of the axial alternating magnetic field strength generated inside the heating section of the copper rod is obtained based on the ratio of the magnetomotive force amplitude to the heating length. Based on the frequency, conductivity, and permeability of the high-frequency alternating current, the radial characteristic depth at which the amplitude of the high-frequency alternating electromagnetic field attenuates to 1 / e of the surface amplitude when the high-frequency alternating electromagnetic field penetrates into the interior of the copper rod is calculated, thus obtaining the skin depth. The surface impedance of the copper rod is determined based on the skin depth and conductivity. The average surface heat flux density of the copper rod is obtained by multiplying the square of the amplitude of the axial alternating magnetic field intensity and the modulus of the surface impedance of the copper rod. The high-frequency input power is determined by the product of the average surface heat flux density, the radius of the copper rod, and the heating length.

[0012] Next, the state parameters of the synthetic ester oil include the density, specific heat capacity, and volume of the synthetic ester oil. Based on the state parameters of the synthetic ester oil, the equivalent total heat capacity of the synthetic ester oil is determined, including: The equivalent total heat capacity of the synthetic ester oil is calculated by multiplying its density, specific heat capacity, and volume.

[0013] Furthermore, the insulating paper parameters include the first thickness of the inner insulating paper and the second thickness of the outer insulating paper; the synthetic ester oil state parameters also include the initial temperature of the synthetic ester oil; Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, the maximum allowable heating time for simulating gas generation during synthetic ester oil overheating faults is calculated, including: Based on the radius, first thickness, heating length of the copper rod and the preset thermal conductivity of the insulating paper, a first equivalent thermal resistance is generated from the outer surface of the copper rod to the gap between the inner and outer insulating papers. Based on the radius of the copper rod, the first thickness, the second thickness, the heating length, the preset thermal conductivity of the insulating paper, and the preset natural convection heat transfer coefficient between the outer surface of the outer insulating paper and the synthetic ester oil, a second equivalent thermal resistance is generated from the gap region between the inner and outer insulating papers to the synthetic ester oil region. Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating faults in synthetic ester oil is obtained.

[0014] Next, the maximum allowable heating time for simulating gas production from overheating faults in synthetic ester oil is obtained based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, including: Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating of synthetic ester oil is calculated using the following formula: ; in, The maximum allowable heating time for simulating gas generation during overheating failure of synthetic ester oil; The preset target local temperature; This is the initial temperature for synthesizing the ester oil; For high-frequency input power; The first equivalent thermal resistance for heat transfer from the outer surface of the copper rod to the gap between the inner and outer insulating paper layers; The second equivalent thermal resistance for heat transfer from the gap between the inner and outer insulating paper layers to the synthetic ester oil region; This represents the equivalent total heat capacity of the synthetic ester oil.

[0015] The following benefits can be obtained by implementing the present invention: This invention involves wrapping the lower outer periphery of a copper rod with an inner layer of insulating paper and an outer layer of insulating paper, and placing a fiber optic temperature sensor between the two layers of insulating paper. A high-frequency induction coil is arranged in a non-contact manner to simulate the heating module. Based on the principle of high-frequency induction heating, the copper rod generates a localized concentrated heat source, which can reproduce the local overheating condition of the synthetic ester oil close to the insulating structure. The fiber optic temperature sensor in the gap between the two layers of insulating paper can directly collect the temperature signal of the overheating hot spot area. The transparent reaction vessel facilitates intuitive observation of the gas production and phase change phenomena of the synthetic ester after heating. With the addition of a sealing flange, the internal environment of the vessel is sealed, which can stably carry out the simulation test of gas production due to overheating of synthetic ester oil, and obtain overheating temperature characteristics and gas production evolution information close to the real working condition. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating, provided in an embodiment of the present invention.

[0018] Figure 2 This is a schematic flowchart of a method for simulating gas generation due to overheating faults in synthetic esters based on high-frequency induction heating, provided in one embodiment of this application.

[0019] Figure 3 This is a schematic diagram of a one-dimensional radial lumped parameter thermal circuit model provided in an embodiment of this application.

[0020] Explanation of reference numerals in the attached drawings: 1. Transparent reaction vessel; 2. Outer insulating paper; 3. Inner insulating paper; 4. Synthetic ester oil; 5. Sealing flange; 6. Copper rod; 7. Pressure relief valve; 8. Pressure gauge; 9. Oil injection valve; 10. Fiber optic temperature sensor; 11. High-frequency induction coil; 12. Oil extraction valve. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0026] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0027] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0028] See Figure 1 To address the problem that existing technologies cannot simulate localized ultra-high temperature overheating, an embodiment of the present invention provides a synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating, comprising: a transparent reaction vessel 1 containing synthetic ester oil 4, a sealing flange 5 disposed on the top of the transparent reaction vessel 1, a copper rod 6, a high-frequency induction coil 11, an inner insulating paper 3, an outer insulating paper 2, and an optical fiber temperature sensor 10. The copper rod 6 passes vertically through the sealing flange 5, and the upper part of the copper rod 6 is fixed by the sealing flange 5. The lower part of the copper rod 6 is immersed in the synthetic ester oil 4. The outer surface of the lower part of the copper rod 6 is wrapped with the inner insulating paper 3 and the outer insulating paper 2, and an optical fiber temperature sensor 10 is provided between the inner insulating paper 3 and the outer insulating paper 2. The copper rod 6, the inner insulating paper 3 and the outer insulating paper 2 constitute a simulated heating module. The high-frequency induction coil 11 is arranged in a non-contact manner around the outer periphery of the simulated heating module.

[0029] Specifically, after the high-frequency induction coil 11 is connected to a high-frequency induction power supply, a high-frequency alternating current of 10kHz~500kHz is passed through it, thereby generating an alternating magnetic field. High-frequency eddy currents are induced inside the copper rod 6 within this magnetic field range. Due to the skin effect, the eddy currents are concentrated on the surface of the copper rod 6, which greatly increases the power density on the surface of the copper rod 6 and causes the temperature to rise rapidly. The heat generated by the copper rod 6 is transferred outward to the inner insulating paper 3 and the outer insulating paper 2 wrapped on the outside. The transparent reaction container 1 maintains an internal sealed environment through the sealing flange 5 set at the top. The transparent reaction container 1 contains synthetic ester oil 4. The lower part of the copper rod 6, the inner insulating paper 3, and the outer insulating paper 2 are all immersed in the synthetic ester oil 4, thereby reproducing the local overheating condition close to the insulating structure. The fiber optic temperature sensor 10 arranged between the inner insulating paper 3 and the outer insulating paper 2 collects the temperature data of the hot spot area in real time. Under the action of local high temperature, the synthetic ester oil 4 inside the transparent reaction container 1 undergoes cracking and gas production and phase change.

[0030] In this invention, a transparent reaction vessel 1 is used to hold the synthetic ester oil 4, and allows for direct observation of the gas production and phase change process of the oil after heating. The sealing flange 5, located on the top of the transparent reaction vessel 1, ensures the internal space of the vessel is sealed to guarantee a stable experimental environment, and also serves to fix and limit the upper part of the copper rod 6. The simulated heating module, composed of the copper rod 6, the inner insulating paper 3, and the outer insulating paper 2, can replicate the real structure of conductors and insulation layers in power equipment, recreating the overheating scenario in actual operation. The high-frequency induction coil 11 arranged around the copper rod 6 can achieve efficient local heating of the copper rod 6 in a non-contact manner, overcoming the shortcomings of traditional overall heating methods that are difficult to form local ultra-high temperatures. The fiber optic temperature sensor 10, arranged between the inner insulating paper 3 and the outer insulating paper 2, can accurately capture the temperature signal of the overheating hotspot, providing reliable temperature data support for analyzing the overheating temperature characteristics and gas production evolution law.

[0031] Preferably, it also includes: an oil extraction valve 12; The oil extraction valve 12 is installed at a predetermined distance from the bottom of the transparent reaction vessel 1.

[0032] Specifically, after the device completes the synthetic ester oil overheating fault simulation test, the oil sampling valve 12, which is installed at a preset distance (e.g., 5-20 mm, this value is only an illustrative preferred implementation range) from the bottom of the transparent reaction vessel 1, is opened. The synthetic ester oil sample that has been produced by high-temperature pyrolysis inside the transparent reaction vessel 1 can flow out through the oil sampling valve 12 to obtain the oil sample after the test. Subsequently, dissolved gas detection and analysis can be carried out on the extracted oil sample.

[0033] Preferably, it also includes: an oil injection valve 9, a pressure gauge 8, and a pressure relief valve 7; The oil injection valve 9, pressure gauge 8, and pressure relief valve 7 are all installed on the top of the sealing flange 5.

[0034] Specifically, before conducting the synthetic ester oil overheating fault simulation test, synthetic ester oil 4 can be added into the transparent reaction vessel 1 through the oil injection valve 9 installed on the top of the sealing flange 5. The pressure gauge 8 can collect the pressure value inside the vessel in real time and display it externally. During the test, the synthetic ester oil 4 will generate gas due to thermal decomposition, causing the pressure inside the vessel to rise. When the pressure inside the vessel reaches the set condition, the pressure relief valve 7 can be opened to release the excess gas inside the vessel, thereby regulating the pressure state inside the transparent reaction vessel 1 and maintaining the pressure inside the vessel within a controllable range during the test.

[0035] In this invention, the oil injection valve 9 provides a channel for injecting synthetic ester oil 4 into the device, facilitating the filling of the test medium; the pressure gauge 8 can provide real-time feedback on the internal pressure of the transparent reaction vessel 1, making it easy for test personnel to monitor the pressure changes inside the vessel; the pressure relief valve 7 can perform pressure relief operation when the internal pressure is abnormal, preventing the internal pressure of the sealed container from being too high and ensuring the safe operation of the entire simulation device when conducting overheating gas generation tests.

[0036] Preferably, the synthetic ester oil 4 in the transparent reaction vessel 1 occupies four-fifths of the volume of the transparent reaction vessel 1.

[0037] Specifically, synthetic ester oil 4 is added into the transparent reaction vessel 1, occupying four-fifths of its volume, with the remaining one-fifth reserved as a gas phase space. During the overheating fault simulation test, the synthetic ester oil 4 undergoes pyrolysis under localized high temperatures, generating gas. This gas can enter the reserved empty space inside the vessel, facilitating subsequent research on the characteristics of fault-generated gas. Simultaneously, it buffers pressure fluctuations during the test, mitigating the risk of a rapid pressure increase due to full oil filling, thus enhancing the overall safety of the simulation test.

[0038] Specifically, the transparent reaction container is made of quartz glass to form a hollow cylindrical structure to withstand the high temperature and pressure generated inside during the test. The high-frequency magnetic field generated by the high-frequency induction coil 11 passes through the transparent reaction container 1. The quartz glass does not interact with the high-frequency magnetic field, and the high-frequency magnetic field can penetrate the container wall without loss. The magnetic field can act normally on the copper rod 6 inside the container, so that the copper rod 6 can generate eddy currents normally to achieve heating. At the same time, the container maintains its own transparent properties, and the various changes of the internal synthetic ester oil 4 after heating can be directly observed from the outside.

[0039] In this invention, a hollow cylindrical structure made of quartz glass is used as a transparent reaction vessel 1. This material has the properties of high temperature and high pressure resistance, and can withstand the temperature under the overheating test conditions of synthetic ester oil and the pressure brought by internal gas generation, thus meeting the working conditions requirements of the closed overheating gas generation simulation test. Quartz glass will not react with high-frequency magnetic fields, and high-frequency magnetic fields can penetrate the container wall without damage, without interfering with the high-frequency induction heating process. The cylindrical structure is convenient for accommodating the test medium and internal components, and the transparency also allows for direct observation of the gas generation and phase change test phenomena of the oil inside the container.

[0040] See Figure 2 This invention provides a method for simulating gas generation during overheating failures in synthetic esters based on high-frequency induction heating, comprising: S1. Obtain the excitation parameters of the high-frequency induction coil, the physical and geometric parameters of the copper rod, the parameters of the insulating paper, and the state parameters of the synthetic ester oil. Specifically, the excitation parameters of the high-frequency induction coil include the number of turns of the high-frequency induction coil, the amplitude of the high-frequency alternating current flowing through the high-frequency induction coil, the frequency of the high-frequency alternating current flowing through the high-frequency induction coil, and the heating length of the high-frequency induction coil on the copper rod. The physical and geometric parameters of the copper rod include the conductivity, permeability, and radius of the copper rod. The insulating paper parameters include the first thickness of the inner insulating paper and the second thickness of the outer insulating paper. The synthetic ester oil state parameters include the density, specific heat capacity, volume, and initial temperature of the synthetic ester oil. Collecting all the above parameters provides all the basic input information for subsequent experiments.

[0041] S2. Determine the high-frequency input power based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod; Preferably, the excitation parameters of the high-frequency induction coil include the number of turns of the high-frequency induction coil, the amplitude of the high-frequency alternating current supplied to the high-frequency induction coil, the frequency of the high-frequency alternating current supplied to the high-frequency induction coil, and the heating length of the high-frequency induction coil on the copper rod; the physical geometric parameters of the copper rod include the conductivity of the copper rod, the permeability of the copper rod, and the radius of the copper rod. The high-frequency input power is determined based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod, including: The magnetomotive force amplitude of the high-frequency induction coil is determined based on the number of turns and the amplitude of the high-frequency alternating current. The amplitude of the axial alternating magnetic field strength generated inside the heating section of the copper rod is obtained based on the ratio of the magnetomotive force amplitude to the heating length. Based on the frequency, conductivity, and permeability of the high-frequency alternating current, the radial characteristic depth at which the amplitude of the high-frequency alternating electromagnetic field attenuates to 1 / e of the surface amplitude when the high-frequency alternating electromagnetic field penetrates into the interior of the copper rod is calculated, thus obtaining the skin depth. The surface impedance of the copper rod is determined based on the skin depth and conductivity. The average surface heat flux density of the copper rod is obtained by multiplying the square of the amplitude of the axial alternating magnetic field intensity and the modulus of the surface impedance of the copper rod. The high-frequency input power is determined by the product of the average surface heat flux density, the radius of the copper rod, and the heating length.

[0042] Specifically, first determine that the effective number of turns of the high-frequency induction coil is N, and the high-frequency alternating current flowing through the high-frequency induction coil is N. ( It is the current amplitude, (This refers to the current frequency). The amplitude of the axial alternating magnetic field intensity inside the heating section of the copper rod can be obtained using Ampere's circuital law. The calculation formula is: ; In the formula, N is the effective number of turns of the high-frequency induction coil; This refers to the amplitude of the high-frequency alternating current. This represents the heating length of the high-frequency induction coil on the copper rod.

[0043] For conductivity , magnetic permeability Using a copper rod, calculate the skin depth caused by high-frequency eddy currents. The calculation formula is: ; In the formula, f is the frequency of the high-frequency alternating current passed into the high-frequency induction coil; The permeability of the copper rod; Let be the electrical conductivity of the copper rod.

[0044] Copper rod surface resistance The calculation formula is: ; In the formula, j is the imaginary unit; Then, based on Poynting's theorem, the average electromagnetic power density on the surface of the copper rod, i.e., the surface heat flux density, is given. The calculation formula is: ; Finally, considering the radius of the copper rod in the heating zone... Calculate the total effective heat power on the surface of the input copper rod, i.e., the high-frequency input power. The calculation formula is: ; In the formula, Let be the radius of the copper rod.

[0045] In this invention, the magnetic field amplitude calculation relationship can determine the strength of the magnetic field at the copper rod, and the skin depth and surface impedance calculation relationship can reflect the penetration effect of the high-frequency magnetic field on the copper rod and the electromagnetic confinement characteristics of the copper rod surface. The phasor parameters used in Poynting's theorem are used to solve for the active power, eliminating reactive components that do not generate heat, and obtaining the heat flux level per unit heated area of ​​the copper rod and the overall heating power received by the copper rod. By adjusting the number of coil turns, current amplitude, and current frequency, the operator can quantitatively control the heating power and heating rate of the copper rod, providing a calculation basis for setting various overheating conditions in the synthetic ester oil overheating gas production test. At the same time, combined with the copper rod's own conductivity and magnetic permeability, radius, and heating length, the heating effect can be predicted in advance, ensuring controllable test conditions and reproducible test results.

[0046] S3. Determine the equivalent total heat capacity of the synthetic ester oil based on its state parameters; Preferably, the state parameters of the synthetic ester oil include the density of the synthetic ester oil, the specific heat capacity of the synthetic ester oil, and the volume of the synthetic ester oil. Based on the state parameters of the synthetic ester oil, the equivalent total heat capacity of the synthetic ester oil is determined, including: The equivalent total heat capacity of the synthetic ester oil is calculated by multiplying its density, specific heat capacity, and volume.

[0047] Specifically, based on the physical structure of a synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating, a model was constructed as follows: Figure 3 The corresponding one-dimensional radial lumped parameter thermal circuit model is shown. Representing the high-frequency input power, serving as the heat source input for the thermal circuit; the temperature of node ① is denoted as... The corresponding temperature of the copper rod, connected in parallel The heat capacity of the copper rod is denoted as ; the temperature at node ② is denoted as . The real-time local temperature of the synthetic ester oil corresponding to the gap between the inner and outer insulating papers, in parallel. The equivalent heat capacity between the inner and outer paper layers; the temperature at node ③ is denoted as The corresponding overall average temperature of the synthetic ester oil, in parallel The equivalent total heat capacity of the synthetic ester oil is given. The calculation expression is as follows ; In the formula The density of synthetic ester oil, The specific heat capacity of synthetic ester oils This represents the volume of the synthesized ester oil inside the transparent reaction vessel. thermal resistance The first equivalent thermal resistance represents the region between the outer surface of the copper rod and the gap between the inner and outer insulating papers. The second equivalent thermal resistance represents the region between the inner and outer insulating paper layers and the synthetic ester oil region. This represents the thermal resistance of synthetic ester oil to the external environment. Representing the external environmental reference temperature, this parameter can be taken from the measured ambient temperature at the test site or used as a preset boundary condition in simulation calculations. Substituting the density, specific heat capacity, and volume from the state parameters of the synthetic ester oil into the formula, the equivalent total heat capacity of the synthetic ester oil is obtained. This heat capacity is used as the heat capacity of the third node in the thermal circuit model to participate in subsequent thermal circuit calculations.

[0048] In this invention, the equivalent total heat capacity of the synthetic ester oil is a key parameter in the radial lumped parameter thermal circuit model. This heat capacity characterizes the synthetic ester oil's ability to store heat and reflects the ease with which the oil's temperature changes after receiving heat. Quantitative calculation of the equivalent total heat capacity using the density, specific heat capacity, and volume of the synthetic ester oil provides accurate nodal heat capacity input for the one-dimensional radial thermal circuit model. This supports the simulation calculation of the radial heat transfer process between the copper rod, two layers of insulating paper, and the synthetic ester oil, facilitating the deduction of the temperature change patterns at each node over time. This, in turn, aids in the analysis of the heat transfer process under experimental conditions, enabling predictive analysis of internal temperature changes during the experiment.

[0049] S4. Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, calculate the maximum allowable heating time for simulating gas generation during synthetic ester oil overheating faults. Preferably, the insulating paper parameters include the first thickness of the inner insulating paper and the second thickness of the outer insulating paper; the synthetic ester oil state parameters also include the initial temperature of the synthetic ester oil; Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, the maximum allowable heating time for simulating gas generation during synthetic ester oil overheating faults is calculated, including: Based on the radius, first thickness, heating length of the copper rod and the preset thermal conductivity of the insulating paper, a first equivalent thermal resistance is generated from the outer surface of the copper rod to the gap between the inner and outer insulating papers. Based on the radius of the copper rod, the first thickness, the second thickness, the heating length, the preset thermal conductivity of the insulating paper, and the preset natural convection heat transfer coefficient between the outer surface of the outer insulating paper and the synthetic ester oil, a second equivalent thermal resistance is generated from the gap region between the inner and outer insulating papers to the synthetic ester oil region. Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating faults in synthetic ester oil is obtained.

[0050] Preferably, the step of obtaining the maximum allowable heating time for simulating gas production in synthetic ester oil overheating faults based on the first equivalent thermal resistance, the second equivalent thermal resistance, high-frequency input power, equivalent total heat capacity, initial temperature, and preset target local temperature includes: Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating of synthetic ester oil is calculated using the following formula: ; in, The maximum allowable heating time for simulating gas generation during overheating failure of synthetic ester oil; The preset target local temperature; This is the initial temperature for synthesizing the ester oil; For high-frequency input power; The first equivalent thermal resistance for heat transfer from the outer surface of the copper rod to the gap between the inner and outer insulating paper layers; The second equivalent thermal resistance for heat transfer from the gap between the inner and outer insulating paper layers to the synthetic ester oil region; This represents the equivalent total heat capacity of the synthetic ester oil.

[0051] Specifically, the first equivalent thermal resistance of the region from the outer surface of the copper rod to the gap between the inner and outer insulating papers. The calculation formula is: ; In the formula, Let be the radius of the copper rod, and d be the thickness of the single layer of insulating paper. The thermal conductivity of the insulating paper is preset, with an exemplary range of 0.18-0.22 W / (m·K). This represents the heating length of the high-frequency induction coil on the copper rod.

[0052] The second equivalent thermal resistance from the gap between the inner and outer insulating paper layers to the synthetic ester oil region. The calculation formula is: ; In the formula, The natural convection heat transfer coefficient between the outer surface of the outer insulating paper and the synthetic ester oil is preset, and an exemplary value of 80 W / (m²・K) is taken; in this embodiment, the first thickness of the inner insulating paper and the second thickness of the outer insulating paper are equal, both taken as d.

[0053] The first equivalent thermal resistance With the second equivalent thermal resistance The sum of these values ​​yields the total local thermal resistance. To address the characteristic of localized extreme heat but overall stagnant temperature in the experiment, the system temperature was decoupled into two parts: a fast response from localized hot spots and a slow overall response from the synthetic ester oil. The overall average temperature of the synthetic ester oil was... The slow drift, reflecting the accumulation of heat in the oil volume, serves only as the physical background for the one-dimensional radial lumped parameter thermal circuit model and is not involved in the subsequent algebraic solution for heating time. The corresponding relationship is: ; Real-time local temperature of synthetic ester oil at the gap between the inner and outer insulating paper layers It can be approximated as the superposition of the local steady-state temperature difference and the overall oil temperature drift mentioned above, with the corresponding relationship as follows: ; Real-time local temperature of ester oil synthesized at interstitial sites Equal to the preset target local temperature Transform and rearrange the time variable, then substitute it into... The formula for calculating the maximum allowable heating time is derived to obtain the maximum allowable heating time. : ; In the formula, The maximum allowable heating time for simulating gas generation during overheating failures in synthetic ester oils; This represents a preset target local temperature. For example, the value range for low-temperature overheating is 150~300 degrees Celsius, the value range for medium-temperature overheating is 300~700 degrees Celsius, and the value range for high-temperature overheating is 700~900 degrees Celsius. This corresponds to the real-time local temperature of the synthetic ester oil at the gap between the inner and outer insulating paper in the thermal circuit model. The desired set value; Represents the initial temperature of the synthetic ester oil; Represents high-frequency input power; This represents the first equivalent thermal resistance. This represents the second equivalent thermal resistance. This represents the equivalent total heat capacity of synthetic ester oil.

[0054] Under the test conditions of this embodiment, the power density of high-frequency induction heating is extremely high, and the local heating rate is much greater than the heat dissipation rate through the container wall to the external environment. The heating process can be approximated as an adiabatic process. At the same time, the test environment temperature is constant and the heating time is extremely short. The heat loss accounts for a very small proportion of the total input heat and can be ignored.

[0055] In this invention, the first equivalent thermal resistance characterizes the conduction resistance that hinders heat transfer from the outer wall of the copper rod to the gap between the two layers of insulating paper. The second equivalent thermal resistance includes two parts: the solid conduction thermal resistance of the outer insulating paper and the convective heat transfer thermal resistance between the outer surface of the insulating paper and the oil. These two parts can quantitatively characterize the heat transfer resistance during the process of heat transfer from the copper rod through the inner and outer insulating papers to the synthetic ester oil. The calculated thermal resistance is affected by parameters such as the thickness of the insulating paper, the thermal conductivity of the insulating paper, and the convective heat transfer coefficient. The maximum allowable heating time is obtained by solving the above formula. This ensures that the real-time local temperature of the synthetic ester oil at the gap between the insulating papers reaches the preset target local temperature, while constraining the experimental heating time. This avoids the problem of the overall temperature of the synthetic ester oil exceeding the safe decomposition threshold due to excessive heating time, and prevents the synthetic ester oil from undergoing non-target overall high-temperature decomposition. It ensures that the experiment only reproduces the local overheating and gas generation phenomenon near the insulating paper, ensuring consistency between the simulated working conditions and the local overheating faults of real power equipment. At the same time, it improves the safety of the experimental process and facilitates the quantitative reproduction of experimental conditions under different working conditions.

[0056] S5. Based on the excitation parameters of the high-frequency induction coil, control the high-frequency induction coil to start in order to heat the synthetic ester oil. The simulation ends when the heating time reaches the maximum allowable heating time.

[0057] Preferably, during the heating process, the real-time local temperature of the synthetic ester oil after heating is collected by a fiber optic temperature sensor; The simulation ends when the heating duration is found to be less than the maximum allowable heating duration, but the real-time local temperature reaches the preset target local temperature.

[0058] Specifically, the high-frequency induction coil is started according to the excitation parameters of the high-frequency induction coil to heat the synthetic ester oil. During the heating process, the real-time local temperature of the synthetic ester oil is collected by the fiber optic temperature sensor. If the heating time has not reached the maximum allowable heating time, but the real-time local temperature reaches the preset target local temperature first, the overheating fault gas generation simulation process is terminated directly. If the real-time local temperature has not risen to the preset target local temperature, but the actual heating time reaches the maximum allowable heating time first, the overheating fault gas generation simulation process is also terminated.

[0059] In this invention, the high-frequency induction coil performs heating according to the excitation parameters, and the fiber optic temperature sensor can directly obtain the real-time local temperature at the gap of the insulating paper, forming a temperature closed-loop judgment logic. The dual termination conditions are set to ensure that the local hot spot can reach the overheating temperature required for the test and complete the fault reproduction, while the maximum allowable heating time can be used to constrain the time limit and prevent the synthetic ester oil from undergoing unexpected high-temperature cracking due to prolonged heating. This balances the test effect and test safety, and realizes reliable control of the transformer local overheating fault simulation process.

[0060] It is understood that the above method embodiments correspond to the device embodiments of the present invention, and can realize the above device embodiments of the present invention providing a synthetic ester overheating fault gas generation simulation device based on high frequency induction heating.

[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A device for simulating gas generation due to overheating failure in synthetic esters based on high-frequency induction heating, characterized in that, include: A transparent reaction vessel containing synthetic ester oil, a sealing flange located on top of the transparent reaction vessel, a copper rod, a high-frequency induction coil, an inner layer of insulating paper, an outer layer of insulating paper, and a fiber optic temperature sensor; The copper rod passes vertically through the sealing flange, and the upper part of the copper rod is fixed by the sealing flange. The lower part of the copper rod is immersed in synthetic ester oil. The outer surface of the lower part of the copper rod is wrapped with the inner layer of insulating paper and the outer layer of insulating paper. An optical fiber temperature sensor is set between the inner layer of insulating paper and the outer layer of insulating paper. The copper rod, the inner layer of insulating paper and the outer layer of insulating paper constitute a simulated heating module. The high-frequency induction coil is arranged in a non-contact manner around the outer periphery of the simulated heating module.

2. The synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating as described in claim 1, characterized in that, Also includes: Oil extraction valve; The oil extraction valve is installed at a predetermined distance from the bottom of the transparent reaction vessel.

3. The synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating as described in claim 2, characterized in that, Also includes: Oil injection valve, pressure gauge, and pressure relief valve; The oil injection valve, pressure gauge, and pressure relief valve are all installed on the top of the sealing flange.

4. The synthetic ester overheating fault gas generation simulation device based on high-frequency induction heating as described in claim 3, characterized in that, The synthetic ester oil in the transparent reaction vessel occupies four-fifths of the vessel's volume.

5. A method for simulating gas generation due to overheating faults in synthetic esters based on high-frequency induction heating, characterized in that, Applicable to the synthetic ester overheating failure gas generation simulation device as described in claims 1-4; The method for simulating gas generation due to overheating failure in synthetic esters includes: Obtain the excitation parameters of the high-frequency induction coil, the physical and geometric parameters of the copper rod, the parameters of the insulating paper, and the state parameters of the synthetic ester oil; The high-frequency input power is determined based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod. Based on the state parameters of the synthetic ester oil, the equivalent total heat capacity of the synthetic ester oil is determined; Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, the maximum allowable heating time for simulating gas generation during overheating faults of synthetic ester oil is calculated. The high-frequency induction coil is activated based on the excitation parameters to heat the synthetic ester oil. The simulation ends when the heating time reaches the maximum allowable heating time.

6. The method for simulating gas generation due to overheating failure in synthetic esters using high-frequency induction heating as described in claim 5, characterized in that, Also includes: During the heating process, the real-time local temperature of the synthetic ester oil after heating is collected by a fiber optic temperature sensor. The simulation ends when the heating duration is found to be less than the maximum allowable heating duration, but the real-time local temperature reaches the preset target local temperature.

7. The method for simulating gas generation due to overheating faults in synthetic esters based on high-frequency induction heating as described in claim 6, characterized in that, The excitation parameters of the high-frequency induction coil include the number of turns of the high-frequency induction coil, the amplitude of the high-frequency alternating current supplied to the high-frequency induction coil, the frequency of the high-frequency alternating current supplied to the high-frequency induction coil, and the heating length of the high-frequency induction coil on the copper rod; the physical and geometric parameters of the copper rod include the conductivity of the copper rod, the permeability of the copper rod, and the radius of the copper rod. The high-frequency input power is determined based on the excitation parameters of the high-frequency induction coil and the physical and geometric parameters of the copper rod, including: The magnetomotive force amplitude of the high-frequency induction coil is determined based on the number of turns and the amplitude of the high-frequency alternating current. The amplitude of the axial alternating magnetic field strength generated inside the heating section of the copper rod is obtained based on the ratio of the magnetomotive force amplitude to the heating length. Based on the frequency, conductivity, and permeability of the high-frequency alternating current, the radial characteristic depth at which the amplitude of the high-frequency alternating electromagnetic field attenuates to 1 / e of the surface amplitude when the high-frequency alternating electromagnetic field penetrates into the interior of the copper rod is calculated, thus obtaining the skin depth. The surface impedance of the copper rod is determined based on the skin depth and conductivity. The average surface heat flux density of the copper rod is obtained by multiplying the square of the amplitude of the axial alternating magnetic field intensity and the modulus of the surface impedance of the copper rod. The high-frequency input power is determined by the product of the average surface heat flux density, the radius of the copper rod, and the heating length.

8. The method for simulating gas generation due to overheating failure in synthetic esters based on high-frequency induction heating as described in claim 7, characterized in that, The state parameters of the synthetic ester oil include the density, specific heat capacity, and volume of the synthetic ester oil. Based on the state parameters of the synthetic ester oil, the equivalent total heat capacity of the synthetic ester oil is determined, including: The equivalent total heat capacity of the synthetic ester oil is calculated by multiplying its density, specific heat capacity, and volume.

9. The method for simulating gas generation due to overheating faults in synthetic esters based on high-frequency induction heating as described in claim 8, characterized in that, The insulating paper parameters include the first thickness of the inner insulating paper and the second thickness of the outer insulating paper; the synthetic ester oil state parameters also include the initial temperature of the synthetic ester oil; Based on the high-frequency input power, equivalent total heat capacity, insulating paper parameters, synthetic ester oil state parameters, and preset target local temperature, the maximum allowable heating time for simulating gas generation during synthetic ester oil overheating faults is calculated, including: Based on the radius, first thickness, heating length of the copper rod and the preset thermal conductivity of the insulating paper, a first equivalent thermal resistance is generated from the outer surface of the copper rod to the gap between the inner and outer insulating papers. Based on the radius of the copper rod, the first thickness, the second thickness, the heating length, the preset thermal conductivity of the insulating paper, and the preset natural convection heat transfer coefficient between the outer surface of the outer insulating paper and the synthetic ester oil, a second equivalent thermal resistance is generated from the gap region between the inner and outer insulating papers to the synthetic ester oil region. Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating faults in synthetic ester oil is obtained.

10. The method for simulating gas generation due to overheating failure in synthetic esters based on high-frequency induction heating as described in claim 9, characterized in that, The maximum allowable heating time for simulating gas production from overheating faults in synthetic ester oil is obtained based on the first equivalent thermal resistance, the second equivalent thermal resistance, high-frequency input power, equivalent total heat capacity, initial temperature, and preset target local temperature, including: Based on the first equivalent thermal resistance, the second equivalent thermal resistance, the high-frequency input power, the equivalent total heat capacity, the initial temperature, and the preset target local temperature, the maximum allowable heating time for simulating gas production during overheating of synthetic ester oil is calculated using the following formula: ； in, The maximum allowable heating time for simulating gas generation during overheating failure of synthetic ester oil; The preset target local temperature; This is the initial temperature for synthesizing the ester oil; For high-frequency input power; The first equivalent thermal resistance for heat transfer from the outer surface of the copper rod to the gap between the inner and outer insulating paper layers; The second equivalent thermal resistance for heat transfer from the gap between the inner and outer insulating paper layers to the synthetic ester oil region; This represents the equivalent total heat capacity of the synthetic ester oil.

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