Dry-type bushing electric field calculation method based on influence of voltage and temperature

Abstract

The 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, and the dry-type bushing comprises an end cover, an inner conductive tube, an outer conductive tube, an epoxy core, an insulating jacket, a flange and a plugging piece. The dry-type bushing electric field calculation method based on the voltage and temperature influence comprises the following steps: S1, importing a model of a dry-type direct current bushing into physical field simulation software, introducing direct current voltage U into the dry-type direct current bushing, and performing simulation to obtain a simulation electric field and a simulation temperature field; and S2, manually analyzing the simulated electric field and the simulated temperature field to obtain high-voltage current, and the size of the high-voltage current which is related to the size of the electric field and the material and the temperature of each layer of insulation structure in the insulation jacket. According to the dry-type bushing electric field calculation method based on the voltage and temperature influence, the problem that in the prior art, only an electric field can be simulated, and the electric field intensity of each layer of insulation structure cannot be predicted is solved.

Description

Technical Field

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

[0002] The Chinese patent discloses an optimal wave number selection and application method for solving the DC electric field of an infinitely long cylinder with an application number of CN201910156571.7. The optimal wave number selection and application method for solving the DC electric field of an infinitely long cylinder includes: using a numerical simulation calculation method to obtain an approximate analytical solution of the potential on the cross section of the infinitely long cylinder model; replacing the analytical solution under flat conditions with the approximate analytical solution of the potential on the cross section of the infinitely long cylinder model, and then using an optimization calculation method to obtain the optimal wave number sequence and the corresponding step length sequence. The above method can effectively improve the forward calculation accuracy of the DC electric field solution on the infinitely long cylinder model, but the method cannot calculate the electric field strength at the insulating structure of the insulating jacket in the dry DC bushing, resulting in the electric field strength method being hindered in some scenarios where the insulating jacket in the dry DC bushing has several layers of insulating structure.

[0003] In the prior art, the model of the dry DC bushing can only be imported into the physical field simulation software, and the DC voltage U is applied to the dry DC bushing to simulate the simulated electric field and the simulated temperature field, so as to obtain the electric field strength of the insulation structure through simulation. However, there is still a disadvantage that the electric field strength of each layer of the insulation structure cannot be directly predicted under the conditions of knowing the temperature, thermal resistivity, and the DC voltage U applied at each insulation structure, resulting in the problem of cumbersome operation of predicting the electric field strength of each layer of the insulation structure in some scenarios. Summary of the invention

[0004] The present invention provides a method for calculating the electric field of a dry bushing under 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 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 plugging 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, and an epoxy core is surrounded outside the outer conductive tube. An insulating jacket is surrounded outside the epoxy core, and an end of the insulating jacket is blocked 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. A flange is surrounded outside the epoxy core, and the flange is located at one end of the insulating jacket away from the end cap. Ends of the epoxy core, the inner conductive tube and the outer guide tube away from the end cap are blocked by the plugging piece.

[0007] The dry bushing electric field calculation method based on voltage and temperature influences comprises the following steps:

[0008] S1. Importing the model of the dry-type DC bushing into physical field simulation software, passing a DC voltage U through 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 obtain that the high voltage current, the insulation structure materials and the temperature of each layer in the insulation jacket are all related to the electric field size and the high voltage current size;

[0010] S3. The insulating jacket of the dry DC bushing has several layers of insulating structure. Assuming that the dry DC bushing consists of m layers of insulating structure, 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 insulating 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 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 DC bushing, r i,y is the inner radius of the wall of the i-th insulation structure in the dry 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 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 DC bushing, i = 1, 2, ..., m;

[0019] S5. Acquisition of experimental data, the acquisition steps are as follows: importing the model of the dry DC bushing into the physical field simulation software, passing a DC voltage U through the dry DC bushing, and the DC voltage U has several different values, and simulating to obtain several groups of simulated electric field strength E and simulated temperature field T, the simulated electric field strength E contains E0, E i ,……,E m , E i 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 calculation method containing T0, T i ,……,T m The simulated temperature field T and formula three 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] Preferably, U, T and R are established. 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 constant calculation in the subsequent formula 4. The analysis formula 2 and formula 3 were established to obtain the heat flow Q i The radial thermal resistance R of the i-th insulation structure in the dry 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, through simulation, Formula 5 can be obtained first, thereby obtaining a model for predicting T (that is, Formula 5), ​​and then the heat flow Q can be obtained 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 DC bushing, and several E i Composition E), to 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 embodied 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 , plugging piece 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 in conjunction with 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 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 plugging piece 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 tube 3. 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-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 plugging piece 7.

[0032] The dry bushing electric field calculation method based on voltage and temperature influences comprises the following steps:

[0033] S1. Importing the model of the dry-type DC bushing into physical field simulation software, passing a DC voltage U through 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 obtain that the high voltage current, the insulation structure materials and the temperature of each layer in the insulation jacket are all related to the electric field size and the high voltage current size;

[0035] S3. The insulating jacket of the dry DC bushing has several layers of insulating structure. Assuming that the dry DC bushing consists of m layers of insulating structure, 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 insulating 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 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 DC bushing, r i,yis the inner radius of the wall of the i-th insulation structure in the dry 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 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: (This formula can be used to directly combine the radial thermal resistance R i The temperature T of the outer wall of the i-th insulation structure in the dry DC bushing i The relationship between Q i 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 DC bushing, i = 1, 2, ..., m;

[0043] S5. Acquisition of experimental data, the acquisition steps are as follows: importing the model of the dry DC bushing into the physical field simulation software, passing a DC voltage U through the dry DC bushing, and the DC voltage U has several different values, and simulating to obtain several groups of simulated electric field strength E and simulated temperature field T, the simulated electric field strength E contains E0, E i ,……,E m , E i 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 through 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-forecasting.

[0048] Establish U, T, and R i The relationship model of , the relationship model of prediction T is as follows: In the formula, 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. When the subsequent prediction is separated from the simulation software, it provides the calculation data basis for formulas 3 and 4.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should 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 bushing electric field calculation method under the influence of voltage and temperature is a dry bushing, which includes: an end cap, an inner conductive tube, an outer conductive tube, an epoxy core, an insulating jacket, a flange and a plugging piece. A central hole is opened in the inner conductive tube, and there is air in the central hole. A section of the inner conductive tube is surrounded by the outer conductive tube, and an epoxy core is surrounded outside the outer conductive tube. An insulating jacket is surrounded outside the epoxy core, and the end of the insulating jacket is blocked 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-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. A flange is surrounded outside the epoxy core, and the flange is located at one 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 blocked by the plugging piece. The dry bushing electric field calculation method based on voltage and temperature influences comprises the following steps: S1. Importing the model of the dry-type DC bushing into physical field simulation software, passing a DC voltage U through the dry-type DC bushing, and simulating to obtain a simulated electric field and a simulated temperature field; S2. Artificially analyze the simulated electric field and simulated temperature field, and obtain that the high voltage current, the insulation structure materials and the temperature of each layer in the insulation jacket are all related to the electric field size and the high voltage current size; S3. The insulating jacket of the dry DC bushing has several layers of insulating structure. Assuming that the dry DC bushing consists of m layers of insulating structure, 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 insulating 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 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 DC bushing, r i,y is the inner radius of the wall of the i-th insulation structure in the dry 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 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 DC bushing, i = 1, 2, ..., m; S5. Acquisition of experimental data, the acquisition steps are as follows: importing the model of the dry DC bushing into the physical field simulation software, passing a DC voltage U through the dry DC bushing, and the DC voltage U has several different values, and simulating to obtain several groups of simulated electric field strength E and simulated temperature field T, the simulated electric field strength E contains E0, E i ,……,E m , E i 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 is performed and before step S6 is performed, the following preparatory calculations are performed: Using T0, T i ,……,T m The simulated temperature field T and formula three 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 is 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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