Insulating sheath performance strengthening method, insulating sheath and high-voltage equipment

Abstract

The invention discloses an insulating sheath performance strengthening method, an insulating sheath and high-voltage equipment. The strengthening method comprises the following steps: constructing a high-voltage equipment-insulating sheath simulation model; obtaining interface electric field distribution of the high-voltage equipment and the insulating sheath based on the simulation model, and determining a voltage-sharing demand position and an electric field intensity boundary condition according to the interface electric field distribution; a semi-conductive coating is arranged at a voltage-sharing demand position, and interface electric field distribution under different conductivity of the semi-conductive coating is obtained; determining conductivity boundary conditions according to interface electric field distribution under different conductivity of the semi-conductive coating; setting feature points according to the electric field intensity boundary condition and the conductivity boundary condition, and performing fitting to obtain an electric field intensity-conductivity curve; determining a filler ratio in the base material according to the electric field intensity-conductivity curve; and preparing the insulating sheath according to the filler ratio. Under the condition that the size of the insulating sheath is not changed, the insulating performance of the insulating sheath is improved, and the electric field distribution of an interface is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulating sheaths, and particularly relates to a method for enhancing the performance of an insulating sheath, an insulating sheath, and a high-voltage device. Background Art

[0002] With the widespread use of electric locomotives, the problem of the external insulation performance of the high-voltage cable terminals on the roof has attracted more and more attention. Since the high-voltage cable terminals on the roof are often exposed to the external environment, especially in harsh environments (such as high humidity and high haze), higher requirements are imposed on the external insulation performance of the high-voltage equipment on the roof.

[0003] Due to its specific geometric structure, the high-voltage device will cause local electric field concentration, such as at cable joints or terminals, the high-voltage ends of insulators, the ends of motor bars, and the flange of the wall bushing. The local field strength at these positions is much higher than the average field strength, and may even reach several times the average field strength (i.e., distorted electric field), which brings certain difficulties to the design and manufacture of the device.

[0004] The method of increasing the insulation size to ensure the insulation performance of the device will greatly increase the manufacturing, transportation, and assembly costs of the device; and simply increasing the insulation size cannot relieve the local high field strength, but will accelerate the aging process of the insulation material, bringing potential risks to the long-term safe and reliable operation of the device. Therefore, reasonably improving the electric field distribution and relieving the high field strength at key positions are crucial for the insulation problem of high-voltage devices.

[0005] At present, semi-conductive materials, non-linear materials, etc. are coated on the surface of the high-voltage cable terminal to regulate the distribution of the interface electric field (i.e., the potential difference between different phases). However, this way of regulating the interface electric field requires a high stability of the electric field and is prone to an increase in the interface current density. When the non-linear material is applied to the interface, although it will improve the interface distorted electric field, it will increase the interface current density, thus rendering the function of the insulating sheath ineffective. This method is not applicable to the existing insulating sheath installation scheme. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for enhancing the performance of an insulating sheath, an insulating sheath, and a high-voltage device to solve the problem that the traditional insulating sheath cannot improve the distorted electric field at the interface between the high-voltage device and the insulating sheath.

[0007] The present invention solves the above technical problems through the following technical solutions: A method for enhancing the performance of an insulating sheath includes:

[0008] Constructing a simulation model of the high-voltage device-insulating sheath;

[0009] Obtain the electric field distribution at the interface between the high-voltage device and the insulating sheath based on the simulation model, and determine the voltage equalization required position and the electric field strength boundary conditions according to the electric field distribution at the interface between the high-voltage device and the insulating sheath;

[0010] Set a semi-conductive coating at the voltage equalization required position of the simulation model, and obtain the electric field distribution at the interface under the conductivity of different semi-conductive coatings;

[0011] Determine the conductivity boundary conditions according to the electric field distribution at the interface under the conductivity of different semi-conductive coatings;

[0012] Set multiple characteristic points according to the electric field strength boundary conditions and the conductivity boundary conditions;

[0013] Fit multiple said characteristic points to obtain the electric field strength-conductivity curve of the material;

[0014] Determine the filler ratio in the base material according to the electric field strength-conductivity curve; wherein, the base material refers to the material for making the insulating sheath;

[0015] Prepare the insulating sheath according to the filler ratio;

[0016] Further, the voltage equalization required position is the interface between the high-voltage device and the insulating sheath;

[0017] Further, use the least squares method to fit multiple said characteristic points to obtain the electric field strength-conductivity curve;

[0018] Further, the characteristic points include inner layer characteristic points and outer layer characteristic points;

[0019] Fit multiple said inner layer characteristic points to obtain the electric field strength-conductivity curve of the inner layer material;

[0020] Fit multiple said outer layer characteristic points to obtain the electric field strength-conductivity curve of the outer layer material;

[0021] At the same conductivity, the electric field strength of the inner layer material is less than that of the outer layer material;

[0022] Further, determining the filler ratio in the base material according to the electric field strength-conductivity curve includes:

[0023] Step A1: Add fillers to the base material, stir evenly and cure;

[0024] Step A2: Test the conductivity of the cured material under different electric field strengths;

[0025] Step A3: Determine whether the conductivity of the cured material at different electric field strengths is within the allowable error range of the electric field strength-conductivity curve; if so, obtain the filler ratio in the base material; if not, adjust the filler ratio and transfer to Step A1.

[0026] Based on the same concept, the present invention also provides an insulating sheath, which is prepared by using the insulating sheath performance strengthening method as described above.

[0027] Based on the same concept, the present invention also provides a high-voltage device, and an insulating sheath is provided outside the high-voltage device, and the insulating sheath is prepared by using the insulating sheath performance strengthening method as described above.

[0028] Further, a sealing cover is provided at the sealing portion of the insulating sheath.

[0029] Further, the sealing cover is made of silicone rubber material.

[0030] Further, the high-voltage device is a high-voltage cable terminal, and the insulating sheath is provided on the first umbrella skirt and the lower flange of the high-voltage cable terminal.

[0031] Beneficial Effects

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] Based on the electric field distribution at the interface between the high-voltage device and the insulating sheath, the present invention determines multiple characteristic points of the nonlinear material according to the electric field strength boundary condition and the conductivity boundary condition, obtains the electric field strength-conductivity curve of the nonlinear material according to the multiple characteristic points, and finally determines the ratio of the nonlinear material in the base material according to the electric field strength-conductivity curve, and then prepares the insulating sheath. Without changing the size of the insulating sheath, the present invention improves the insulation performance of the insulating sheath, improves the electric field distribution at the interface, improves the uniformity of the electric field distribution at the interface, and realizes better external insulation protection for the high-voltage device. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only one embodiment of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 is a flowchart of the insulating sheath performance strengthening method in the embodiment of the present invention;

[0036] Figure 2 is a semi-sectional view of the geometric model of the high-voltage cable terminal-insulating sheath in the embodiment of the present invention;

[0037] Figure 3 It is the interfacial electric field distribution diagram of the lower flange-insulating sheath in the embodiment of the present invention;

[0038] Figure 4 It is the electric field strength-conductivity curve of the inner layer material and the outer layer material in the embodiment of the present invention;

[0039] Figure 5 It is the front view of the insulating sheath with a sealing cover added in the embodiment of the present invention;

[0040] Figure 6 It is the top view of the insulating sheath with a sealing cover added in the embodiment of the present invention;

[0041] Figure 7 It is the front view of the sealing cover in the embodiment of the present invention;

[0042] Figure 8 It is the side view of the sealing cover in the embodiment of the present invention.

[0043] Explanation of reference numerals: 1-insulating sheath, 2-umbrella skirt, 3-lower flange. Detailed implementation manners

[0044] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0045] Next, the technical solutions of the present application will be described in detail with specific embodiments. The following several specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0046] Figure 1 The flowchart of the insulating sheath performance enhancement method provided by the present invention is shown. In this embodiment, a high-voltage cable terminal is taken as an example to illustrate the specific implementation steps of the method of the present invention. As Figure 1 shown, the insulating sheath performance enhancement method includes the following steps:

[0047] Step 1: Construct a simulation model of the high-voltage cable terminal-insulating sheath.

[0048] In the specific implementation manner of the present invention, the specific construction process of the simulation model of the high-voltage cable terminal-insulating sheath is as follows:

[0049] Step 1.1: Construct a geometric model of the high-voltage cable terminal-insulating sheath, as Figure 2 shown;

[0050] Step 1.2: Mesh the geometric model of the high-voltage cable terminal - insulation sheath to obtain a mesh model;

[0051] Step 1.3: Set the material properties and boundary conditions in the mesh model to obtain a simulation model.

[0052] As Figure 2 shown, insulation sheaths 1 are provided on both the first umbrella skirt 2 and the lower flange 3 of the high-voltage cable terminal to prevent the influence of wet pollution, etc. on the high-voltage cable terminal.

[0053] Step 2: Obtain the interfacial electric field distribution between the high-voltage cable terminal and the insulation sheath based on the simulation model, and determine the voltage equalization required position and the electric field strength boundary conditions according to the interfacial electric field distribution between the high-voltage cable terminal and the insulation sheath.

[0054] Taking the lower flange and the insulation sheath as an example, Figure 3 shows the interfacial electric field distribution between the lower flange and the insulation sheath. It can be seen from Figure 3 that when there is no pollution on the outer surface of the insulation sheath and there is a dry band on the outer surface of the umbrella skirt, the average electric field strength at the interface between the umbrella skirt and the insulation sheath is of the order of 10 4 . Even if internal wet pollution (i.e., internal wetness) and air gaps appear on the interface, the electric field strength near the air gap only just reaches the order of 10 5 , which is much less than the breakdown field strength of the air gap. Therefore, local discharge problems basically do not occur at the interface between the umbrella skirt and the insulation sheath; when there is pure wet pollution (i.e., all wet) on the outer surface of the insulation sheath, the average electric field strength at the interface between the umbrella skirt and the insulation sheath is about 1.5×10 5 V / m; and in the case where there is internal wet pollution and air gaps at the interface between the umbrella skirt and the insulation sheath, the electric field strength near the air gap can reach the order of 10 6 . In this case, local discharge is extremely likely to occur inside the air gap. From this, it can be known that the voltage equalization required position (i.e., the position where voltage equalization is needed) is the interface between the umbrella skirt and the insulation sheath, and the electric field strength boundary condition is of the order of 10 6 .

[0055] The setting of the electric field strength - conductivity curve of the nonlinear material needs to comprehensively consider two factors: loss and voltage equalization. Set the angular frequency of the alternating voltage as ω, the interfacial electric field strength under the rated voltage condition as E N , the relative permittivity of the nonlinear material as ε, then the upper limit of the conductivity under the electric field strength of the rated voltage condition should satisfy σ(E N ) << ωε; when there is a high electric field strength E AC at the interface (reaching 10 6Order of V / m), for the voltage equalization required position, the space charge accumulates relatively fast. In order to generate enough reverse electric field to offset the distorted electric field, it is required that the minimum conductivity of the voltage equalization required position should satisfy σ(E AC ) >> ωε. For example, setting the relative permittivity ε of the nonlinear material to 3.34 and the traction network voltage frequency to 50 Hz, it can be determined that under normal operating conditions, the conductivity of the nonlinear material should satisfy σ(E N ) << 9.3×10 -9 S / m, while under the condition of high electric field strength at the interface, the conductivity of the nonlinear material should satisfy σ(E AC ) >> 9.3×10 -9 S / m.

[0056] Step 3: Set a semi-conductive coating at the voltage equalization required position of the simulation model, and obtain the electric field distribution at the interface under the conductivity of different semi-conductive coatings.

[0057] According to engineering practical experience, set a semi-conductive coating with a thickness of 1 mm on the interface between the inner surface of the insulating sheath and the petticoat, and observe the change of the electric field strength at the interface between the petticoat and the insulating sheath by changing the conductivity of the semi-conductive coating.

[0058] Step 4: Determine the conductivity boundary conditions according to the electric field distribution at the interface under the conductivity of different semi-conductive coatings.

[0059] According to the simulation results, when the conductivity of the semi-conductive coating is 1×10 -12 S / m, the semi-conductive coating does not have conductivity; when the conductivity of the semi-conductive coating is 1×10 -10 S / m, the semi-conductive coating begins to have conductivity; when the conductivity of the semi-conductive coating is 1×10 -7 S / m, the semi-conductive coating already shows the characteristic of resistance voltage equalization; when the conductivity of the semi-conductive coating exceeds 1×10 -6 S / m, the increase in the conductivity of the semi-conductive coating has basically no effect on the electric field at the interface. It can be determined from this that the conductivity boundary conditions are 1×10 -12 S / m (non-conductive), 1×10 -10 S / m (beginning to have conductivity) and 1×10 - 6 S / m (the conductivity has basically no effect on the electric field at the interface).

[0060] Step 5: Set multiple characteristic points according to the electric field strength boundary conditions and the conductivity boundary conditions.

[0061] According to Figure 3From the simulation results, it can be seen that the distorted electric field is more likely to occur on the inner surface of the insulating sheath. Therefore, the insulating sheath is divided into an inner layer and an outer layer, and the characteristic points of the inner layer material are set smaller according to the electric field strength boundary condition and the conductivity boundary condition, so as to obtain a steeper electric field strength-conductivity curve of the inner layer material, making the conductivity of the inner layer material more sensitive to the change of the electric field. According to the electric field strength boundary condition (10 6 order of magnitude) determined in step 2 and the conductivity boundary condition determined in step 4, the inner layer characteristic points and the outer layer characteristic points are set as shown in Table 1.

[0062] Table 1 Characteristic points of non-linear materials

[0063]

[0064] Step 6: Fit multiple characteristic points to obtain the electric field strength-conductivity curve of the material.

[0065] As can be seen from step 5, the characteristic points include the inner layer characteristic points and the outer layer characteristic points. Therefore, the inner layer characteristic points and the outer layer characteristic points are fitted separately. Fit multiple inner layer characteristic points to obtain the electric field strength-conductivity curve of the inner layer material (i.e., the inner layer non-linear curve); fit multiple outer layer characteristic points to obtain the electric field strength-conductivity curve of the outer layer material (i.e., the outer layer non-linear curve), as Figure 4 shown. In the specific implementation manner of the present invention, the least squares method is used to fit multiple inner layer characteristic points to obtain the electric field strength-conductivity curve of the inner layer material; the least squares method is used to fit multiple outer layer characteristic points to obtain the electric field strength-conductivity curve of the outer layer material.

[0066] Step 7: Determine the filler ratio in the base material according to the electric field strength-conductivity curve; wherein, the base material refers to the material for making the insulating sheath.

[0067] As can be seen from step 6, the electric field strength-conductivity curve includes the electric field strength-conductivity curve of the inner layer material and the electric field strength-conductivity curve of the outer layer material. Therefore, determine the filler ratio in the inner layer base material according to the electric field strength-conductivity curve of the inner layer material, and then prepare the non-linear material for the inner layer of the insulating sheath according to the inner layer base material, the filler and the filler ratio in the inner layer base material, and then prepare the inner layer of the insulating sheath (i.e., the low non-linear layer). Determine the filler ratio in the outer layer base material according to the electric field strength-conductivity curve of the outer layer material, and then prepare the non-linear material for the outer layer of the insulating sheath according to the outer layer base material, the filler and the filler ratio in the outer layer base material. After the inner layer of the insulating sheath is cured, then prepare the outer layer of the insulating sheath (i.e., the high non-linear layer) thereon. Through the optimization of the non-linear materials of the inner layer and the outer layer, the purpose of optimizing the electric field near the entire insulating sheath is achieved, and the external insulation of the high-voltage cable terminal is strengthened.

[0068] In a specific embodiment of the present invention, the filler ratio in the inner or outer base material is determined according to the electric field strength - conductivity curve of the inner layer material or the outer layer material, including:

[0069] Step A1: Add fillers to the base material, stir evenly, and cure.

[0070] Step A2: Test the conductivity of the cured material at different electric field strengths.

[0071] Step A3: Determine whether the conductivity of the cured material at different electric field strengths is within the allowable error range of the electric field strength - conductivity curve; if so, obtain the filler ratio in the base material; if not, adjust the filler ratio and transfer to Step A1.

[0072] In this embodiment, the inner base material or the outer base material is silicone rubber, and the fillers are silicon carbide and zinc oxide. Simulation of the prepared nonlinear material shows a good voltage equalizing effect near the distorted electric field.

[0073] Step 8: Prepare an insulating sheath according to the filler ratio.

[0074] The embodiment of the present invention also provides an insulating sheath, and the insulating sheath is prepared by using the insulating sheath performance strengthening method in the embodiment of the present application.

[0075] The embodiment of the present invention also provides a high - voltage cable terminal. An insulating sheath is provided on the first umbrella skirt and the lower flange of the high - voltage cable terminal, and the insulating sheath is prepared by using the insulating sheath performance strengthening method in the embodiment of the present application.

[0076] The existing sealing method of the insulating sheath is usually: at the sealing part of the insulating sheath, epoxy screws are used for tight pressing, so that the insulating sheath is tightly sealed. In actual operation, this sealing method cannot avoid the entry of a humid environment into the inner surface of the insulating sheath, resulting in partial discharge. In the specific embodiment of the present invention, as Figures 5 to 8 shown, a sealing cover is provided at the sealing part of the insulating sheath. The sealing cover is made of soft silicone rubber material. Screw holes are provided on both sides of the sealing cover, and the screw holes and the sealing part of the insulating sheath are tightly pressed and sealed together with epoxy screws, so that the sealing cover completely seals the sealing part of the insulating sheath, effectively avoiding the entry of a humid environment through the sealing part into the inner surface of the insulating sheath.

[0077] The above - disclosed are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or variations within the technical scope disclosed by the present invention, and all of them should be covered by the protection scope of the present invention.

Claims

1. A method for enhancing the performance of an insulating sheath, characterized in that: The strengthening method comprises: Construct a simulation model of high voltage equipment-insulating sheath; Based on the simulation model, the electric field distribution at the interface between the high-voltage equipment and the insulating sheath is obtained, and the voltage equalization requirement position and the electric field strength boundary condition are determined according to the electric field distribution at the interface between the high-voltage equipment and the insulating sheath; Disposing a semi-conductive coating at a position where equalization of pressure is required in the simulation model, and obtaining the interfacial electric field distribution under different conductivities of the semi-conductive coating; Determining the conductivity boundary condition according to the interfacial electric field distribution under the conductivity of different semiconductive coatings; Setting a plurality of characteristic points according to the electric field strength boundary condition and the conductivity boundary condition; Fitting a plurality of the characteristic points to obtain an electric field strength-conductivity curve of the material; Determining the filler ratio in the base material according to the electric field strength-conductivity curve; wherein the base material refers to the material for making the insulating sheath; An insulating sheath is prepared according to the filler ratio.

2. The method for enhancing the performance of the insulating sheath according to claim 1, characterized in that: The voltage equalization required position is the interface between the high voltage equipment and the insulating sheath.

3. The method for enhancing the performance of the insulating sheath according to claim 1, characterized in that: The least square method is used to fit the plurality of characteristic points to obtain an electric field strength-conductivity curve.

4. The method for enhancing the performance of an insulating sheath according to claim 1, characterized in that: The feature points include inner feature points and outer feature points; Fitting a plurality of the inner layer characteristic points to obtain an electric field strength-conductivity curve of the inner layer material; Fitting a plurality of the outer layer characteristic points to obtain an electric field strength-conductivity curve of the outer layer material; At the same conductivity, the electric field strength of the inner material is smaller than that of the outer material.

5. The method for enhancing the performance of an insulating sheath according to any one of claims 1 to 4, characterized in that: Determining the filler ratio in the base material according to the electric field strength-conductivity curve includes: Step A1: Add filler to the base material, stir evenly and solidify; Step A2: testing the conductivity of the cured material under different electric field strengths; Step A3: Determine whether the conductivity of the cured material under different electric field strengths and the electric field strength-conductivity curve are within the allowable error range; if so, obtain the filler ratio in the base material; if not, adjust the filler ratio and proceed to step A1.

6. An insulating sheath, characterized in that: The insulating sheath is prepared by the insulating sheath performance enhancement method according to any one of claims 1 to 5.

7. A high voltage device, characterized in that: An insulating sheath is arranged outside the high-voltage equipment, and the insulating sheath is prepared by the insulating sheath performance enhancement method according to any one of claims 1 to 5.

8. The high voltage device according to claim 7, characterized in that A sealing cover is provided at the sealing portion of the insulating sheath.

9. The high voltage device according to claim 8, characterized in that The sealing cover is made of silicone rubber material.

10. The high voltage device according to any one of claims 7 to 9, characterized in that: The high-voltage equipment is a high-voltage cable terminal, and the insulating sheath is provided on the first shed and the lower flange of the high-voltage cable terminal.

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