Calculation method of electric field of dry-type bushing based on the influence of voltage and temperature

Abstract

The present invention discloses a method for calculating the electric field of a dry-type bushing under the influence of voltage and temperature. The method is based on a dry-type bushing, which includes an end cap, an inner conductive tube, an outer conductive tube, an epoxy core, an insulating jacket, a flange, and a sealing member. The method comprises the following steps: S1, importing a model of the dry-type DC bushing into physical field simulation software, applying a DC voltage U to the dry-type DC bushing, and simulating a simulated electric field and a simulated temperature field; S2, manually analyzing the simulated electric field and simulated temperature field to determine whether the high-voltage current, the insulation material of each layer in the insulating jacket, and the temperature are all related to the electric field magnitude. The method solves the problem of the prior art that can only simulate the electric field but cannot predict the electric field strength of each insulation layer.

Description

Technical Field

[0001] The present invention relates to the field of electric field calculation, and in particular to a dry-type bushing electric field calculation method based on the influence of voltage and temperature. Background Art

[0002] A Chinese patent application, CN201910156571.7, discloses an optimized wavenumber selection and application method for solving the DC electric field of an infinitely long cylinder. The method includes: using a numerical simulation method to obtain an approximate analytical solution for the potential on the cross-section of the infinitely long cylinder model; replacing the analytical solution under flat ground conditions with the approximate analytical solution for the potential on the cross-section of the infinitely long cylinder model; and then using an optimization calculation method to obtain the optimal wavenumber sequence and corresponding step size sequence. This method can effectively improve the forward calculation accuracy of the DC electric field solution on the infinitely long cylinder model. However, this method cannot calculate the electric field strength at the insulating structure of the insulating jacket in a dry-type DC bushing, which hinders the calculation of the electric field strength in some scenarios where the insulating jacket of the dry-type DC bushing has multiple layers of insulating structure.

[0003] In the prior art, the only way is to import the model of the dry-type DC bushing into physical field simulation software, apply a DC voltage U to the dry-type DC bushing, and simulate the simulated electric field and simulated temperature field to obtain the electric field strength of the insulation structure through simulation. However, a disadvantage still exists: the electric field strength of each layer of the insulation structure cannot be directly predicted under conditions such as the temperature, thermal resistivity, and applied DC voltage U at each insulation structure. This leads to the problem of cumbersome operation in predicting the electric field strength of each layer of the insulation structure in some scenarios. Summary of the Invention

[0004] The present invention aims to provide a dry bushing electric field calculation method based on the influence of voltage and temperature, so as to solve the problem that the prior art can only simulate the electric field but cannot predict the electric field strength of each layer of insulation structure.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a dry-type bushing electric field calculation method based on the influence of voltage and temperature. The object of the dry-type bushing electric field calculation method based on the influence of voltage and temperature is a dry-type bushing. The dry-type bushing comprises: an end cap, an inner conductive tube, an outer conductive tube, an epoxy core, an insulating jacket, a flange and a sealing piece. A central hole is opened in the inner conductive tube, and air is contained in the central hole. A section of the inner conductive tube is surrounded by the outer conductive tube. The outer conductive tube is surrounded by the epoxy core. The outer conductive tube is surrounded by the insulating jacket. The end of the insulating jacket is sealed by the end cap. The end cap is only for the end of the inner conductive tube away from the outer conductive tube to pass through. An SF6 gas-filled space is formed between the inner wall of the end cap, the inner wall of the insulating jacket, the outer wall of the inner conductive tube and the end face of the epoxy core. The outer surface of the epoxy core is surrounded by a flange. The flange is located at the end of the insulating jacket away from the end cap. The ends of the epoxy core, the inner conductive tube and the outer guide tube away from the end cap are sealed by the sealing piece.

[0007] The dry bushing electric field calculation method based on the influence of voltage and temperature includes the following steps:

[0008] S1. Importing the model of the dry-type DC bushing into physical field simulation software, applying a DC voltage U to the dry-type DC bushing, and simulating to obtain a simulated electric field and a simulated temperature field;

[0009] S2. Artificially analyze the simulated electric field and simulated temperature field, and find that the high voltage current, the insulation structure materials and temperatures of each layer in the insulation jacket are all related to the magnitude of the electric field and the magnitude of the high voltage current;

[0010] S3. The insulation jacket of the dry-type DC bushing has several layers of insulation structure. Assuming that the dry-type DC bushing consists of m layers of insulation structure, then under the action of DC voltage U, the radius is r n The maximum electric field strength E of the insulating structure of the nth cylindrical layer at n,max Calculated by the following formula:

[0011]

[0012] In the above formula, ε n is the dielectric constant of the nth layer, r n is the radius of the nth layer of insulation structure, ε i is the dielectric constant of the i-th insulating structure, ε i is the dielectric constant of the i-th insulating structure;

[0013] S4, radial thermal resistance R of the i-th insulation structure in the dry-type DC bushing i Calculated by the following formula:

[0014]

[0015] In the above formula, β is the thermal resistivity of the material, and the unit of β is K·m / W; r i,xis the outer wall radius of the i-th insulation structure in the dry-type DC bushing, r i,y is the inner radius of the wall of the i-th insulation structure in the dry-type DC bushing, r i,x and r i,y The unit is m; L is the wall thickness of the i-th layer insulation structure in the dry-type DC bushing, and the unit of L is m.

[0016] S4. Assuming the total thickness of the insulation jacket in the dry-type DC bushing is L1, calculate the heat flux Q at the outer wall of the i-th insulation structure in the dry-type DC bushing. i , Q i The calculation formula is:

[0017]

[0018] In the above formula, T0 is the temperature of the outer wall of the inner conductive tube; T i is the temperature of the outer wall of the i-th insulation structure in the dry-type DC bushing, i = 1, 2, ..., m;

[0019] S5. Acquisition of experimental data. The acquisition steps are as follows: import the model of the dry-type DC bushing into the physical field simulation software, apply DC voltage U to the dry-type DC bushing, and the DC voltage U has several different values, and simulate to obtain several sets of simulated electric field intensity E and simulated temperature field T. The simulated electric field intensity E contains E0, E i 、……、E m , E i It represents the electric field strength of the i-th insulation structure in the dry-type DC bushing. The simulated temperature field T contains T0, T i 、……、T m ;

[0020] S6, all Q i Form a heat flow group Q, establish a relationship model among E, U, T and Q, and calculate E through the relationship model.

[0021] Preferably, after step S5 and before step S6, the following preparatory calculation is performed: using the data containing T0, T i ,……,T m The simulated temperature field T and formula 3 are used to calculate the heat flow group Q obtained from the experimental data.

[0022] Preferably, the relationship model of E, U, T and Q is: Wherein, a0, a1, a2, a3, c1, c2 and c3 are all constants, and the constants are obtained by substituting experimental data into formula 4 through regression algorithm.

[0023] Preferably, E in Formula 4 i The constraint condition is Formula 1.

[0024] It is preferred to establish U, T and R i The relationship model of , the relationship model of prediction T is as follows: Wherein, e0, e1, e2, e3, f1, f2 and f3 are all constants, and the constants are obtained by substituting experimental data into Formula 5 through regression algorithm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Through the simulation software, the simulation experimental data was obtained, and the experimental data was obtained for the calculation of the constant in the subsequent formula 4. The analytical formulas 2 and 3 were established to obtain the heat flow Q i The radial thermal resistance R of the i-th insulation structure in the dry-type DC bushing i Relationship between heat flow Q i and radial thermal resistance R i It is also closely related to T. Therefore, in this application, the simulation can first obtain Formula 5, thereby obtaining a model for predicting T (that is, Formula 5), ​​and then obtain the heat flow Q through the established Formula 3. i ; Then, the predicted E can be directly calculated by the established formula 4 under known conditions, without using simulation to obtain the predicted E (E i is the electric field strength of the i-th insulation structure in the dry-type DC bushing, and several E i It is composed of E), which can predict E without simulation software, providing convenience for many scenarios such as design.

[0027] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional view of the dry-type bushing in the present invention.

[0029] Reference numerals: end cap 1 , inner conductive tube 2 , outer conductive tube 3 , epoxy core 4 , insulating jacket 5 , flange 6 , sealing member 7 . DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, objectives and functions of the present invention clearer and easier to understand, the present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0031] The present invention discloses a method for calculating the electric field of a dry bushing under the influence of voltage and temperature. The object of the method for calculating the electric field of a dry bushing under the influence of voltage and temperature is a dry bushing, such as Figure 1As shown, the dry-type bushing includes: an end cap 1, an inner conductive tube 2, an outer conductive tube 3, an epoxy core 4, an insulating jacket 5, a flange 6 and a sealing member 7. A central hole is opened in the inner conductive tube 2, and there is air in the central hole. A section of the inner conductive tube 2 is surrounded by the outer conductive tube 3, and the epoxy core 4 is surrounded by the outer conductive tube 3. The insulating jacket 5 is surrounded by the outer conductive jacket 5, and the end of the insulating jacket 5 is blocked by the end cap 1. The end cap 1 is only for the end of the inner conductive tube 2 away from the outer conductive tube 3 to pass through. An SF6 gas-filled space is formed between the inner wall of the end cap 1, the inner wall of the insulating jacket 5, the outer wall of the inner conductive tube 2 and the end face of the epoxy core 4. The outer surface of the epoxy core 4 is surrounded by a flange 6, and the flange 6 is located at the end of the insulating jacket 5 away from the end cap 1. The ends of the epoxy core 4, the inner conductive tube 2 and the outer guide tube away from the end cap 1 are blocked by the sealing member 7.

[0032] The dry bushing electric field calculation method based on the influence of voltage and temperature includes the following steps:

[0033] S1. Importing the model of the dry-type DC bushing into physical field simulation software, applying a DC voltage U to the dry-type DC bushing, and simulating to obtain a simulated electric field and a simulated temperature field;

[0034] S2. Artificially analyze the simulated electric field and simulated temperature field, and find that the high voltage current, the insulation structure materials and temperatures of each layer in the insulation jacket are all related to the magnitude of the electric field and the magnitude of the high voltage current;

[0035] S3. The insulation jacket of the dry-type DC bushing has several layers of insulation structure. Assuming that the dry-type DC bushing consists of m layers of insulation structure, then under the action of DC voltage U, the radius is r n The maximum electric field strength E of the insulating structure of the nth cylindrical layer at n,max Calculated by the following formula:

[0036]

[0037] In the above formula, ε n is the dielectric constant of the nth layer, r n is the radius of the nth layer of insulation structure, ε i is the dielectric constant of the i-th insulating structure, ε i is the dielectric constant of the i-th insulating structure;

[0038] S4, radial thermal resistance R of the i-th insulation structure in the dry-type DC bushing i Calculated by the following formula:

[0039]

[0040] In the above formula, β is the thermal resistivity of the material, and the unit of β is K·m / W; r i,x is the outer wall radius of the i-th insulation structure in the dry-type DC bushing, r i,yis the inner radius of the wall of the i-th insulation structure in the dry-type DC bushing, r i,x and r i,y The unit is m; L is the wall thickness of the i-th layer insulation structure in the dry-type DC bushing, and the unit of L is m.

[0041] S4. Assuming the total thickness of the insulation jacket in the dry-type DC bushing is L1, calculate the heat flux Q at the outer wall of the i-th insulation structure in the dry-type DC bushing. i , Q i The calculation formula is: (The calculation of this formula can directly combine the radial thermal resistance R i The temperature T of the outer wall of the i-th insulation structure in the dry-type DC bushing i The relationship between Q i It can directly reflect the insulation structure material, insulation structure size, simulation temperature T i For the subsequent formula 4, E i The influence of simplifies formula 4)

[0042] In the above formula, T0 is the temperature of the outer wall of the inner conductive tube; T i is the temperature of the outer wall of the i-th insulation structure in the dry-type DC bushing, i = 1, 2, ..., m;

[0043] S5. Acquisition of experimental data. The acquisition steps are as follows: import the model of the dry-type DC bushing into the physical field simulation software, apply DC voltage U to the dry-type DC bushing, and the DC voltage U has several different values, and simulate to obtain several sets of simulated electric field intensity E and simulated temperature field T. The simulated electric field intensity E contains E0, E i 、……、E m , E i It represents the electric field strength of the i-th insulation structure in the dry-type DC bushing. The simulated temperature field T contains T0, T i 、……、T m ;

[0044] S6, all Q i Form a heat flow group Q, establish a relationship model among E, U, T and Q, and calculate E through the relationship model.

[0045] After step S5 and before step S6, the following preparatory calculation is performed: using the i ,……,T m The simulated temperature field T and formula 3 are used to calculate the heat flow group Q obtained from the experimental data. This provides data for the subsequent calculation of formula 4 and simplifies formula 4.

[0046] The relationship model among E, U and Q is: Wherein, a0, a1, a2, a3, c1, c2 and c3 are all constants, and the constants are obtained by substituting experimental data into formula 4 through regression algorithm.

[0047] And E in formula 4 i The constraint condition is formula 1. It is limited to predict E by formula 4. i The maximum value obtained. When E is predicted by formula 4 i Greater than E n,max When E i Can only be equal to E n,max , to avoid over-predictions.

[0048] Establish U, T, and R i The relationship model of , the relationship model of prediction T is as follows: Where e0, e1, e2, e3, f1, f2, and f3 are all constants obtained by substituting experimental data into Formula 5 through a regression algorithm. This provides the calculation data basis for Formulas 3 and 4 when subsequent predictions are made without simulation software.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the electric field of a dry bushing under the influence of voltage and temperature, characterized in that: The object of the dry-type bushing electric field calculation method under the influence of voltage and temperature is a dry-type bushing, which includes: an end cap, an inner conductive tube, an outer conductive tube, an epoxy core, an insulating jacket, a flange and a sealing piece. The inner conductive tube is provided with a central hole, and air is contained in the central hole. A section of the inner conductive tube is surrounded by the outer conductive tube, and an epoxy core is surrounded by the outer conductive tube. The outer conductive tube is surrounded by an insulating jacket, and the end of the insulating jacket is sealed by the end cap. The end cap is only for the end of the inner conductive tube away from the outer conductive tube to pass through. An SF6 gas-filled space is formed between the inner wall of the end cap, the inner wall of the insulating jacket, the outer wall of the inner conductive tube and the end face of the epoxy core. The outer surface of the epoxy core is surrounded by a flange, and the flange is located at the end of the insulating jacket away from the end cap. The ends of the epoxy core, the inner conductive tube and the outer guide tube away from the end cap are sealed by the sealing piece. The dry bushing electric field calculation method based on the influence of voltage and temperature includes the following steps: S1. Import the dry-type DC bushing model into the physical field simulation software, apply a DC voltage U to the dry-type DC bushing, and simulate to obtain a simulated electric field and a simulated temperature field; S2. Artificially analyze the simulated electric field and simulated temperature field, and find that the high voltage current, the insulation structure materials and temperatures of each layer in the insulation jacket are all related to the magnitude of the electric field and the magnitude of the high voltage current; S3. The insulation jacket of the dry-type DC bushing has several layers of insulation structure. Assuming that the dry-type DC bushing consists of m layers of insulation structure, then under the action of DC voltage U, the radius is r n The maximum electric field strength E of the insulating structure of the nth cylindrical layer at n,max Calculated by the following formula: In the above formula, ε n is the dielectric constant of the nth layer, r n is the radius of the nth layer of insulation structure, ε i is the dielectric constant of the i-th insulating structure, ε i is the dielectric constant of the i-th insulating structure; S4, radial thermal resistance R of the i-th insulation structure in the dry-type DC bushing i Calculated by the following formula: In the above formula, β is the thermal resistivity of the material, and the unit of β is K·m / W; r i,x is the outer wall radius of the i-th insulation structure in the dry-type DC bushing, r i,y is the inner radius of the wall of the i-th insulation structure in the dry-type DC bushing, r i,x and r i,y The unit of L is m; L is the wall thickness of the i-th layer insulation structure in the dry-type DC bushing, and the unit of L is m; S4. Assuming the total thickness of the insulation jacket in the dry-type DC bushing is L1, calculate the heat flux Q at the outer wall of the i-th insulation structure in the dry-type DC bushing. i , Q i The calculation formula is: In the above formula, T0 is the temperature of the outer wall of the inner conductive tube; T i is the temperature of the outer wall of the i-th insulation structure in the dry-type DC bushing, i = 1, 2, ..., m; S5. Acquisition of experimental data. The acquisition steps are as follows: import the model of the dry-type DC bushing into the physical field simulation software, apply DC voltage U to the dry-type DC bushing, and the DC voltage U has several different values, and simulate to obtain several sets of simulated electric field intensity E and simulated temperature field T. The simulated electric field intensity E contains E0, E i 、……、E m , E i It represents the electric field strength of the i-th insulation structure in the dry-type DC bushing. The simulated temperature field T contains T0, T i ,……,T m ; S6, all Q i Form a heat flow group Q, establish a relationship model among E, U, T and Q, and calculate E through the relationship model.

2. The dry bushing electric field calculation method based on voltage and temperature influence according to claim 1 is characterized in that: After step S5 and before step S6, the following preparatory calculations are performed: Using T0, T i ,……,T m The simulated temperature field T and formula 3 are used to calculate the heat flow group Q obtained from the experimental data.

3. The dry bushing electric field calculation method based on voltage and temperature influence according to claim 2, characterized in that: The relationship model among E, U and Q is: Wherein, a0, a1, a2, a3, c1, c2 and c3 are all constants, and the constants are obtained by substituting experimental data into formula 4 through regression algorithm.

4. The dry bushing electric field calculation method based on voltage and temperature influence according to claim 3 is characterized in that: And E in formula 4 i The constraint condition is Formula 1.

5. The dry bushing electric field calculation method based on voltage and temperature influence according to claim 4 is characterized in that: Establish U, T, and R i The relationship model of , the relationship model of prediction T is as follows: Wherein, e0, e1, e2, e3, f1, f2 and f3 are all constants, and the constants are obtained by substituting experimental data into Formula 5 through regression algorithm.

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