Direct-current GIL grounding shell shape design method for repelling metal particles

Abstract

The invention relates to a method for designing the shape of a direct-current GIL grounding shell for repelling metal particles, and the method comprises the steps: carrying out the slope type design of an insulator grounding shell, changing the intensity and direction of an electric field near a basin-type insulator, and affecting the stress condition of free metal particles on the inner surface side of the grounding shell; motion behavior characteristics of metal particles in a direct-current electric field are changed, and the adsorption effect of the insulator on the metal particles in a pipeline wall is reduced. And through multi-physics field coupling simulation calculation, the charge process and the motion law of the metal particles in the direct-current GIL are explored. The spherical metal particles are released at different positions of the inner surface of the GIL grounding shell, the influence of the grounding shell shape design with different inclination angles on the motion characteristics of the metal particles is compared, the change of the inclination angles of the grounding shell on the adsorption rate of the insulator metal particles is summarized, and a grounding shell design scheme is preferably selected. According to the invention, the adsorption effect of the insulator on metal particles is successfully inhibited, and the surface insulation performance of the insulator is protected.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage equipment manufacturing, and specifically relates to a DC GIL grounding shell shape design method for driving away metal particles, the purpose of which is to improve the insulation reliability of the DC GIL transmission system and ensure the safe and stable operation of the transmission line under special environments. Background Art

[0002] Gas insulated transmission lines (GIL) have the advantages of large power transmission capacity, high stability, and strong environmental adaptability. They are suitable for stable power transmission in extreme and special geographical environments. The basin insulator is the core insulating component of the DC GIL equipment, and its insulation reliability affects the safe and stable operation of the transmission system. Due to inadequate cleaning, friction between metal parts, improper transportation and installation operations, foreign matter such as metal particles and dust are easily introduced into the DC GIL cavity. According to fault statistics, discharge accidents induced by the free movement of metal particles in the DC GIL cavity and surface discharge accidents of basin insulators occur frequently, seriously threatening the safe and stable operation of the power system. Under the action of the DC electric field, free metal particles are charged and start to move back and forth between the high-voltage conductor and the grounded casing, and finally adhere to the surface of the insulator, distorting the local electric field, shortening the insulation distance, destroying the insulation performance, and causing surface flashover faults.

[0003] In order to suppress the tendency of free metal particles inside the DC GIL to move to the surface of the insulator, improve the insulation performance of the DC GIL insulator, reduce the adsorption of free metal particles by the basin insulator, and improve the insulation reliability of the DC GIL equipment, the common solutions currently include laying particle traps near the insulator, coating the electrode surface, and installing shielding electrodes on the high-voltage conductor, etc. However, the above methods still have shortcomings in terms of stability, convenience, and economy, and have not completely solved the potential threat of metal particles to the DC GIL equipment. By optimizing the grounding shell structure near the DC GIL insulator, changing the DC electric field distribution and the stress of metal particles in the area near the insulator and the grounding shell, suppressing the movement activity of metal particles under the action of the DC electric field, guiding metal particles to move to a safe area, and realizing the movement behavior regulation of free metal particles in the pipeline, this method has the advantages of simple design, obvious metal particle suppression effect, and easy industrial application. Summary of the invention

[0004] Based on the above problems, the purpose of the present invention is to overcome the shortcomings of the prior art and propose a DC GIL grounding shell shape design method for driving away metal particles, so as to solve the problem of DC GIL insulator adsorbing metal particles inside the pipeline.

[0005] To achieve the above-mentioned purpose, the present invention provides a DC GIL grounding shell shape design method for driving away metal particles. By optimizing the shape of the metal grounding shell near the insulator, adjusting the inclination angle of the shell and the horizontal plane, changing the DC electric field distribution near the insulator and the force conditions of the metal particles, the movement behavior of the metal particles is regulated, and their movement tendency to the insulator surface is suppressed.

[0006] The technical solution proposed by the present invention is a method for designing the shape of a DC GIL grounding shell for driving away metal particles. The method comprises the following steps:

[0007] Step 1: Build a DC GIL pot-type insulator simulation calculation model and set the key dielectric parameters of the model;

[0008] Step 2: Based on the basin insulator model, analyze the DC electric field distribution around the GIL insulator, analyze the stress of free metal particles in the pipeline under operating conditions, and establish a metal particle motion model inside the DC GIL cavity;

[0009] Step 3: Setting a grounding shell design with different inclination angles on the inner surface of the insulator grounding shell, recalculating the DC electric field distribution of the GIL insulator, and coupling the electric field calculation results with the metal particle motion model;

[0010] Step 4: Release free metal particles at different locations on the inner surface of the DC GIL grounding shell, observe the effects of different grounding shell designs on the movement characteristics of metal particles near the insulator, and statistically compare the adsorption rates of the insulators to the nearby free metal particles under different designs.

[0011] Furthermore, in step 1, the insulator model is a ±500 kV DC GIL pot insulator, the insulator insulation distance is 160 mm, the insulator material is epoxy resin / alumina composite material, the relative dielectric constant is set to 5, and the conductivity is 10 -15 S / m.

[0012] Furthermore, other models in step one include a coaxially arranged metal high-voltage conductor and a grounded shell, etc. The outer radius and inner radius of the center conductor and the shell are 90 and 250 mm respectively, the center conductor is connected to a +500 kV DC voltage, the metal shell is grounded, and the materials are all aluminum alloy.

[0013] Furthermore, in step 1, other areas inside the model are filled with SF6 insulating gas, the gas pressure is set to 0.5 MPa, the relative dielectric constant is set to 1, and the conductivity is set to 10 -20 S / m.

[0014] Furthermore, in step 2, the free metal particles are set to be spherical particles with a radius of 0.1 mm, and the material thereof is consistent with that of the high-voltage conductor and the grounding shell.

[0015] Furthermore, in step 2, the metal particles are charged in contact with the grounded shell under the action of DC voltage, and their motion model takes into account the effects of electric field force, gravity, electric field gradient force and fluid force under the multi-physical field coupling state.

[0016] Furthermore, in step three, the axial length of the grounding shell slope set on the inner surface of the insulator grounding shell is 140-160mm, and the angle between it and the inner surface of the grounding shell is 5-15°, and its material parameters are consistent with the grounding shell, the electric potential is 0, and it is located on the convex and concave sides of the insulator grounding position respectively.

[0017] Furthermore, in step 4, free metal particles are released at different positions on the inner surface of the AC GIL grounding shell, the horizontal distance between the release position and the convex surface of the insulator ranges from 10 to 140 mm, the interval between the metal particles is 10 mm, and the release time of different particles on the convex and concave sides of the insulator is the same, and the movement stops until the particles adhere to the surface of the insulator.

[0018] Furthermore, in step 4, after the movement of the metal particles is completed, the number of metal particles adsorbed on the surface of the insulator is counted, and the metal particle adsorption rate is calculated.

[0019] The beneficial effects brought by the present invention are:

[0020] Compared with the traditional horizontally laid grounding electrode, the angled grounding electrode successfully suppresses the adsorption of metal particles by the insulator, drives the metal particles away from the insulator surface, and protects the surface insulation performance of the insulator.

[0021] The present invention can enhance the expulsion effect of the basin-type insulator in the DC GIL on nearby charged metal particles, inhibit the aggregation and movement of metal particles to the surface of the insulator, protect the insulation performance of the insulator, and effectively prevent insulation failure accidents caused by the adsorption of metal particles on the surface of the insulator. It is of great significance to solve the discharge problem of metal particles attached to the surface of the insulator and improve the operating reliability of high-voltage electrical equipment.

[0022] The method of the present invention can effectively inhibit the adsorption of metal particles inside the cavity by the DC GIL insulator, prevent the occurrence of insulation failure accidents such as discharge and surface flashover caused by the charged movement of free metal particles and their final adsorption on the insulator surface, and improve the reliability and stability of high-voltage electrical equipment. The method has the advantages of simple design, obvious inhibition effect, and easy industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The model of 500kV DC GIL pot insulator and the driving electrode setting of grounded metal shell;

[0024] Figure 2The DC electric field distribution near the insulator under different grounding shell design schemes;

[0025] Figure 3 The motion characteristics of metal particles near the insulator under different grounding shell design schemes;

[0026] Figure 4 This is the relationship between different grounding shell inclination angles and metal particle adsorption rate. DETAILED DESCRIPTION

[0027] How the present invention is implemented is further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] A method for designing a DC GIL grounding shell shape for driving away metal particles comprises the following steps:

[0029] First, build a ±500kV DC GIL pot insulator model, as shown in the attached Figure 1 As shown, the coaxial conductor is arranged in parallel with the metal shell and kept parallel to the horizontal plane, and the high-voltage conductor is connected to a +500kV DC voltage. The pot-type insulator is set between the high-voltage conductor and the grounded shell, and plays important roles such as electrical insulation, mechanical support and air chamber isolation. In order to achieve the active expulsion of metal particles during movement, a slope with a fixed angle and fixed length is designed starting from the position of the three-way junction of the grounded shell and the insulator. The slope angle θ satisfies the following formula:

[0030]

[0031] l is the horizontal length of the grounding electrode slope, which is set to 150mm. Wherein h is the height of the grounding electrode slope, which changes with the change of the slope angle θ. Under different design schemes, the slope angle θ is set to 5°, 10° and 15° respectively. In addition, θ=0° is set as a control group to compare the effects of different slope angles on the motion characteristics of metal particles. In the simulation of the motion characteristics of metal particles, 14 spherical metal particles with a radius of r=0.1mm are released on the inner surface of the grounding shell, and the horizontal distance from the convex surface of the insulator ranges from 10 to 140mm, and the metal particle spacing is 10mm.

[0032] Based on the above basin insulator model, the DC electric field distribution around the GIL guide rod and insulator under operating conditions is calculated, as shown in the attached figure. Figure 2 As shown in the figure, when comparing the DC GIL models with different grounding electrode slope designs, the electric field intensity near the insulator changes slightly when the grounding electrode slope angle changes, and only the area with reduced electric field intensity appears at the slope. However, due to the design of the slope, the direction of the normal electric field on the surface of the grounded shell at the slope changes significantly.

[0033] Based on the above multi-physics field coupling model, the force of free metal particles in the pipeline under the multi-field coupling state is analyzed, and the charging and motion model of free metal particles in the pipeline space is established. The metal particles are charged after colliding with the metal conductor or the grounded shell, and the amount of charge can be approximately calculated by the following formula:

[0034]

[0035] In the formula, ε0 and ε r are the relative dielectric constants of vacuum and material, r is the radius of metal particles, E n is the normal electric field strength at the collision position of the metal particles. During the movement of the metal particles, the force analysis of the free metal particles shows that the electric field force F exerted on the charged metal particles inside the DC GIL device is q , gravity G, electric field gradient force F grad and air resistance F v The real-time motion trajectory of metal particles under the transient action of the AC electric field is calculated. The specific force conditions of the metal particles are as follows:

[0036] F q =qE

[0037]

[0038] Where g is the acceleration due to gravity, m / s 2 ; q is the charge of the metal particles, C; ρ g is the density of SF6 insulating gas, kg / m 3 ; Re is the Reynolds number; Δv is the relative velocity between metal particles and insulating gas medium, m / s.

[0039] Based on the above metal particle motion model, spherical metal particles with a radius of r = 0.1 mm are released at different positions on the surface of the DC GIL grounding electrode. The closest and farthest distances from the convex surface of the insulator are 10 and 140 mm respectively, and the metal particle spacing is 10 mm. The effect of uniform insulator on particle motion before optimization is shown in the attached figure. Figure 3 As shown in (a). Under the action of DC voltage, the metal particles released from the surface of the grounding shell start to move toward the high-voltage electrode and finally adhere to the surface of the insulator under the action of the combined force. The farthest distance between the metal particles and the insulator surface is 140 mm.

[0040] Based on the above results of the metal particle movement near the uniform insulator, a ground slope driving electrode was added. The metal particles were released at the same position on the ground electrode surface on the convex side of the insulator as in the control group. The particle movement characteristics are shown in the attached figure. Figure 3(bd) As shown in Figure 2, under the influence of the sloped grounding shell, the metal particles on the inner surface of the grounding shell are subjected to the radial and axial components of the electric field force away from the insulator surface in the axial direction. r With F z As shown below:

[0041]

[0042]

[0043] Under the action of the axial component of the electric field force r, the starting speed of the metal particles decreases, and under the action of the axial component of the electric field force z, the movement direction of the metal particles changes significantly. When θ = 5°, the metal particles farther away from the insulator no longer adsorb to the surface of the insulator, and the distance between the farthest attached metal particles and the insulator surface drops to 120mm. When θ = 10°, the number of metal particles that can be driven away further increases, and the distance between the farthest attached metal particles and the insulator surface drops to 90mm, and the particle driving effect is obvious. When θ = 15°, nearly half of the metal particles can be driven away from the insulator surface, and the metal particle adsorption area range drops to 60mm, which is nearly 50% lower. Figure 4 The relationship between different grounding shell inclination angles and the metal particle adsorption rate is shown. As the grounding shell inclination angle increases, the number of metal particles adsorbed decreases significantly. The grounding shell inclination angle design effectively inhibits the adsorption of metal particles by the insulator and improves the insulation performance of the insulator.

Claims

1. A DC GIL grounding shell shape design method for driving away metal particles, characterized in that: The following steps are involved: Step 1: Build a simulation model for DC GIL pot insulator; Step 2: Based on the basin insulator model, analyze the DC electric field distribution around the GIL insulator, analyze the stress of free metal particles in the pipeline under operating conditions, and establish a metal particle motion model inside the DC GIL cavity; Step 3: Set a grounding shell with different inclination angles on the grounding side of the insulator, recalculate the DC electric field distribution of the GIL insulator, and couple the electric field calculation results with the metal particle motion model; Step 4: Release free metal particles at different locations on the inner surface of the DC GIL grounding shell, observe the effects of different grounding shell designs on the movement characteristics of metal particles near the insulator, and statistically compare the adsorption rates of free metal particles near the insulator under different designs; In the step 3, a grounding shell slope is arranged near the insulator, the angle between the grounding shell slope and the inner surface of the grounding shell is 5-15°, the material parameters of the grounding shell slope are consistent with the grounding shell, and the potential is 0; The grounding shell slopes are respectively located at the grounding sides of the convex surface and the concave surface of the insulator.

2. A DC GIL grounding shell shape design method for driving away metal particles according to claim 1, characterized in that: The insulator model in step 1 is a ±500kV DC GIL pot-type insulator, the insulator insulation distance is 160mm, the insulator material is epoxy resin / alumina composite material, the relative dielectric constant is set to 5, and the conductivity is 10-15S / m.

3. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: Other models in step 1 include a coaxially arranged metal high-voltage conductor and a grounded shell. The outer radius and inner radius of the center conductor and the shell are 90 and 250 mm respectively. The center conductor is connected to a +500 kV DC voltage, and the metal shell is grounded. The materials are all aluminum alloy.

4. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: In step 1, other areas inside the model are filled with SF6 insulating gas, the gas pressure is set to 0.5 MPa, the relative dielectric constant is 1, and the conductivity is set to 10-20 S / m.

5. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: In step 2, the free metal particles are set to be spherical particles with a radius of 0.1 mm, and the material thereof is consistent with that of the high-voltage conductor and the grounding shell.

6. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: In step 2, the metal particles are charged in contact with the grounded shell under the action of DC voltage, and their motion model takes into account the effects of electric field force, gravity, electric field gradient force and fluid force under the multi-physical field coupling state.

7. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: The axial length of the grounding shell slope described in step 2 is 140-160 mm.

8. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: In step 4, free metal particles are released at different positions on the inner surface of the AC GIL grounding shell. The horizontal distance between the release position and the convex surface of the insulator ranges from 10 to 140 mm, the interval between the metal particles is 10 mm, and the release time of different particles on the convex and concave sides of the insulator is the same, and the movement stops until the particles adhere to the surface of the insulator.

9. The method for designing the shape of a DC GIL grounding shell for driving away metal particles according to claim 1, characterized in that: In step 4, after the movement of the metal particles is completed, the number of metal particles adsorbed on the surface of the insulator is counted, and the metal particle adsorption rate is calculated.

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