A kind of calibration method suitable for explosion-proof sheet opening threshold of current transformer

Abstract

The application provides a kind of calibration method suitable for explosion-proof sheet opening threshold of current transformer, it is related to electrical equipment and equipment safety detection technical field;The method comprises;The energy generated when the current transformer explodes is calculated by energy equivalence formula;The size of the installed explosion-proof sheet is determined by measuring the structure of different models of current transformer;According to the material selection of explosion-proof sheet, the melting temperature, yield strength and stress sensitivity parameter of the material are determined;Combined with the melting temperature of the material, the ambient temperature and the explosion temperature when the transformer arcs and explodes, the temperature coefficient is introduced;The standard opening pressure of the explosion-proof sheet for the current transformer is determined by bringing in the energy proportionality coefficient.The application obtains the material characteristics of the explosion-proof sheet and the size of the current transformer explosion vent channel, thereby determining the calibration method of the explosion-proof sheet opening threshold, and improving the control accuracy of the explosion pressure of the current transformer.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment and equipment safety testing technology, and in particular to a calibration method for the opening threshold of explosion-proof plates used in current transformers. Background Technology

[0002] Current transformers are important electrical devices in power systems and are widely used in power grids with voltage levels of 220kV and above. They have a compact structure, with the secondary winding located inside the top tank. However, dozens of operational failures in the past decade have shown that if an arc discharge fault occurs inside the top tank of this type of transformer, it can easily cause the tank to rupture, damaging not only the transformer itself but also potentially endangering nearby equipment, resulting in wider equipment damage and power outages.

[0003] Explosion-proof safety devices have advantages such as simple structure, sensitivity, accuracy, no leakage, and strong discharge capacity. They can work reliably in viscous, high-temperature, low-temperature, and corrosive environments. As a key safety device for current transformers, they can quickly open the discharge channel during arcing and explosion, reducing the impact of pressure wave on the transformer tank and achieving safe pressure relief.

[0004] However, explosion-proof discs face various challenges in practical applications, such as pressure changes within the pressure vessel caused by temperature variations, which can affect their burst performance. For current transformers, manufacturers often rely on experience to set the pressure threshold for explosion-proof discs, without detailed consideration of material parameters and the impact of explosion pressure. Therefore, a calibration method for the opening threshold of explosion-proof discs used in current transformers needs to be designed. This method should comprehensively consider temperature, material properties, transformer configuration, and arc explosion energy to further improve the accuracy of the opening threshold and enhance pressure relief performance. Summary of the Invention

[0005] To overcome the problems existing in the prior art, this invention designs a calibration method for the opening threshold of explosion-proof discs used in current transformers, comprising: calculating the pressure required to be released when the current transformer explodes using an energy equivalence formula; determining the size of the explosion-proof disc by measuring the structure of different types of current transformers; determining the melting temperature, yield strength, and stress sensitivity parameters of the material according to the material selection of the explosion-proof disc; introducing a temperature coefficient by combining the melting temperature of the material, the ambient temperature, and the explosion temperature during the arc explosion of the transformer; and determining the standard opening pressure of the explosion-proof disc for current transformers based on the energy proportionality coefficient. This invention obtains the material characteristics of the explosion-proof disc and the size of the explosion relief channel of the current transformer, thereby determining the calibration method for the opening threshold of the explosion-proof disc, improving the control accuracy of the explosion pressure of the current transformer.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A calibration method for the opening threshold of explosion-proof elements used in current transformers includes the following steps: The pressure required to be released when a current transformer explodes is calculated using the energy equivalence formula. The dimensions of the explosion-proof sheet to be installed are determined by measuring the structure of different types of current transformers. The yield strength, equivalent plastic strain rate, and strain hardening coefficient of the material are determined according to the material selection of the explosion-proof sheet; A temperature coefficient is introduced by combining the melting temperature of the material, the ambient temperature, and the explosion temperature of the current transformer during arcing. The standard opening pressure of the explosion-proof diaphragm for current transformers is determined based on the energy ratio coefficient.

[0007] Furthermore, based on the model and size of the current transformer, the equivalent explosion energy is calculated, and its expression is: ; In the formula, α This is the equivalent coefficient of oil vapor clouds; V This refers to the total volume of the insulating oil, expressed in liters (L). Q Heat of combustion of insulating oil, expressed in J / L; S x The area of ​​the discharge channel is expressed in square meters (m²). 2 ; r max , r min These are the maximum and minimum tangential radii of the transformer oil tank, respectively, in meters.

[0008] Furthermore, the explosion-proof sheet structure dimensions are determined by different types of current transformer models. Specifically, the explosion-proof sheets used for current transformers are all of the reverse arched groove type. The discharge diameter and discharge channel height are determined by the diameter and height of the expansion joint at the top of the current transformer. The discharge diameter is equal to the cross-sectional diameter of the expansion joint, and the discharge channel height is equal to the short axis length of the transformer plus the height of the expansion joint.

[0009] Furthermore, the strain characteristics of the explosion-proof sheet under different degrees of bending were obtained through finite element simulation. Specifically, explosion-proof sheet models of different structural sizes were established using SolidWorks software, generating STEP files, and then HyperMesh meshes were generated to create mesh files. These were then imported into LS-DYNA finite element simulation. The explosion load was equivalent to a triangular uniformly distributed load applied directly to the explosion-bearing surface. A pulsed loading curve was used to simulate the pressure change over time during the explosion process, obtaining the explosion temperature and explosion pressure of the explosion-proof sheet under the corresponding structural configuration.

[0010] Furthermore, based on the ambient temperature characteristics and the energy proportionality coefficient, the standard opening pressure of the explosion-proof disc is calculated, and its expression is as follows: ; In the formula, Temperature coefficient; T, T r 、T m These are the burst temperature, material melting temperature, and reference temperature, respectively, all in K. σ q The yield stress of the material is expressed in Pa. σ k The explosion pressure of the corresponding explosion-proof sheet is expressed in Pa. d s This is a stress-sensitive parameter; This is the standard energy proportion coefficient; D、h These are the explosion-proof venting diameter and the venting channel height, respectively, in meters (m).

[0011] Compared with the prior art, the present invention has the following features and beneficial effects: 1. This invention obtains the arc explosion energy of a current transformer and combines it with temperature, material properties, and the maximum stress construction function to calculate the opening threshold of explosion-proof discs for different current transformers, thereby improving the accuracy of the explosion-proof disc opening threshold. 2. This invention combines the actual situation of current transformers with the working mechanism of explosion-proof discs, making the explosion-proof discs more suitable for the application of current transformers. Attached Figure Description

[0012] Figure 1 A flowchart illustrating the calibration method for the opening threshold of explosion-proof elements used in current transformers provided by this invention; Figure 2 This is a schematic diagram of the discharge diameter and discharge channel height provided by the present invention. Detailed Implementation

[0013] To overcome the problems existing in the prior art, this invention designs a calibration method suitable for the opening threshold of explosion-proof plates used in current transformers, such as... Figure 1 and Figure 2 As shown, the method includes: calculating the pressure required to be released when a current transformer explodes using an energy equivalence formula; determining the size of the explosion-proof disc by measuring the structure of different types of current transformers; determining the melting temperature, yield strength, and stress sensitivity parameters of the explosion-proof disc according to its material selection; introducing a temperature coefficient by combining the melting temperature of the material, ambient temperature, and the explosion temperature during the transformer's arc explosion; and determining the standard opening pressure of the explosion-proof disc for the current transformer by incorporating an energy proportionality coefficient. This invention provides a calibration method for determining the opening threshold of the explosion-proof disc by obtaining the material characteristics of the explosion-proof disc and the size of the explosion relief channel of the current transformer, thereby improving the control accuracy of the explosion pressure of the current transformer.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: A calibration method for the opening threshold of explosion-proof elements used in current transformers includes the following steps: The pressure required to be released when a current transformer explodes is calculated using the energy equivalence formula. The dimensions of the explosion-proof sheet to be installed are determined by measuring the structure of different types of current transformers. The yield strength, equivalent plastic strain rate, and strain hardening coefficient of the material are determined according to the material selection of the explosion-proof sheet; A temperature coefficient is introduced by combining the melting temperature of the material, the ambient temperature, and the explosion temperature of the current transformer during arcing. By incorporating the energy ratio coefficient, determine the standard opening pressure of the explosion-proof diaphragm for the current transformer.

[0015] Furthermore, based on the model and size of the current transformer, the equivalent explosion energy is calculated, and its expression is: ; In the formula, α This is the equivalent coefficient of oil vapor clouds; V This refers to the total volume of the insulating oil, expressed in liters (L). Q Heat of combustion of insulating oil, expressed in J / L; S x The area of ​​the discharge channel is expressed in square meters (m²). 2 ; r max , r min These are the maximum and minimum tangential radii of the transformer oil tank, respectively, in meters.

[0016] In this embodiment of the invention, the appropriate explosion-proof sheet structure size is determined by different types of current transformer models. Specifically, the explosion-proof sheets used for current transformers are all of the reverse arched groove type. The discharge diameter and discharge channel height are determined by the diameter and height of the expansion joint at the top of the current transformer. The discharge diameter is equal to the cross-sectional diameter of the expansion joint, and the discharge channel height is equal to the short axis length of the transformer plus the height of the expansion joint.

[0017] In this embodiment of the invention, the strain characteristics of the explosion-proof sheet under different degrees of bending are obtained through finite element simulation. Specifically, explosion-proof sheet models of different structural sizes are established using SolidWorks software, generating STEP files, and then HyperMesh meshing is performed to generate mesh files. These are then imported into LS-DYNA finite element simulation, where the explosion load is equivalent to a triangular uniformly distributed load directly applied to the explosion-bearing surface. A pulsed loading curve is used to simulate the pressure change over time during the explosion process, thereby obtaining the explosion temperature and explosion pressure of the explosion-proof sheet under the corresponding structural configuration.

[0018] In this embodiment of the invention, the standard opening pressure of the explosion-proof disc is calculated based on the ambient temperature characteristics and the energy proportionality coefficient, and its expression is as follows: ; In the formula, Temperature coefficient; T, T r 、T m These are the burst temperature, material melting temperature, and reference temperature, respectively, all in K. σ q The yield stress of the material is expressed in Pa. σ k The explosion pressure of the corresponding explosion-proof sheet is expressed in Pa. d s This is a stress-sensitive parameter; This is the standard energy proportion coefficient; D、h These are the explosion-proof venting diameter and the venting channel height, respectively, in meters (m).

Claims

1. A calibration method for the opening threshold of explosion-proof plates used in current transformers, characterized in that, Includes the following steps: The pressure required to be released when a current transformer explodes is calculated using the energy equivalence formula. The dimensions of the explosion-proof sheet were determined by measuring the structure of different types of current transformers. Determine the melting temperature, yield strength, and stress sensitivity parameters of the material based on the material selection of the explosion-proof sheet; A temperature coefficient is introduced by combining the melting temperature of the material, the ambient temperature, and the explosion temperature of the current transformer during arcing. The standard opening pressure of the explosion-proof diaphragm for current transformers is determined based on the energy ratio coefficient.

2. The calibration method for the opening threshold of an explosion-proof diaphragm for a current transformer according to claim 1, characterized in that, Based on the model and size of the current transformer, the equivalent explosion energy is calculated, and its expression is as follows: ； In the formula, α This is the equivalent coefficient of oil vapor clouds; V This refers to the total volume of the insulating oil, expressed in liters (L). Q Heat of combustion of insulating oil, expressed in J / L; S x The area of ​​the discharge channel is expressed in square meters (m²). 2 ; r max , r min These are the maximum and minimum tangential radii of the transformer oil tank, respectively, in meters.

3. The calibration method for the opening threshold of an explosion-proof diaphragm for a current transformer according to claim 1, characterized in that, The structural dimensions of the explosion-proof diaphragm are determined by different types of current transformers, which in turn determines the discharge diameter and discharge channel height, including: The explosion-proof discs used for current transformers are all of the inverted arched groove type. The discharge diameter and discharge channel height are determined by the diameter and height of the expansion joint at the top of the current transformer. The discharge diameter is equal to the cross-sectional diameter of the expansion joint, and the discharge channel height is equal to the short axis length of the transformer plus the height of the expansion joint.

4. The calibration method for the opening threshold of an explosion-proof diaphragm for a current transformer according to claim 1, characterized in that, The strain characteristics of the explosion-proof sheet under different degrees of bending were obtained through finite element simulation, including: Explosion-proof disc models of different structural sizes were created using SolidWorks software, generating STEP files. HyperMesh meshes were then generated to create mesh files, which were imported into LS-DYNA finite element simulation. The explosion load was equivalent to a triangular uniformly distributed load applied directly to the explosion-bearing surface. A pulsed loading curve was used to simulate the pressure change over time during the explosion, obtaining the explosion temperature and explosion pressure of the explosion-proof disc under the corresponding structural configuration.

5. The calibration method for the opening threshold of an explosion-proof diaphragm for a current transformer according to claim 1, characterized in that, The standard opening pressure of the explosion-proof disc is calculated based on the ambient temperature characteristics and the energy proportionality coefficient, and its expression is as follows: ； In the formula, Temperature coefficient; T, T r 、T m These are the burst temperature, material melting temperature, and reference temperature, respectively, all in K. σ q The yield stress of the material is expressed in Pa. σ k The explosion pressure of the corresponding explosion-proof sheet is expressed in Pa. d s This is a stress-sensitive parameter; This is the standard energy proportion coefficient; D、h These are the explosion-proof venting diameter and the venting channel height, respectively, in meters (m).

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