Alternating current GIL insulator metal particle driving electrode design method

Abstract

The invention relates to a design method of an alternating current GIL insulator metal particle driving electrode, which comprises the following steps: laying a wedge-shaped grounding driving electrode on the inner surface of an insulator grounding shell, changing the direction of an electric field near a contact area of an insulator and a grounding electrode, and influencing the stress and motion characteristics of metal particle foreign matters in the area; therefore, the motion behavior of charged particles around the insulator can be regulated and controlled. Through multi-physics field simulation calculation and particle stress analysis, charge and motion behaviors near a metal particle insulator under alternating current voltage are simulated, spherical metal particles are released at different positions of the inner surface of a GIL grounding shell, and motion characteristics of free metal particles in an alternating current GIL with different wedge-shaped grounding driving electrode designs are compared, so that the grounding driving electrode design of the alternating current GIL is simulated. The angle parameter of the driving electrode is preferably selected.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage equipment manufacturing, and specifically relates to a design method for a metal particle driving electrode for an AC GIL insulator. The AC GIL insulator suppresses metal particles based on the grounding driving electrode design, and its purpose is to improve the insulation reliability of the AC GIL transmission system and ensure the safe and stable transmission of electric power resources 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. In AC GIL, the pot insulator is located between the coaxial center conductor and the grounded shell. It is the core insulation component of the AC GIL equipment, and its insulation reliability affects the safe and stable operation of the transmission system. Due to inadequate cleaning, friction of metal parts, poor transportation and installation environment, and gas introduction, foreign matter such as metal particles are inevitably present inside the GIL. According to the failure statistics in recent years, the surface discharge failure of the pot insulator caused by free metal particles in the AC GIL cavity is frequent. The free metal particles move with charge in the AC GIL and tend to adhere to the surface of the insulator. The attached metal particle conductor shortens the insulation distance on the surface of the insulator, resulting in local electric field distortion and discharge problems, and ultimately causing insulation failures such as surface flashover.

[0003] In order to suppress the insulation damage of free metal particles inside the AC GIL to the insulator, reduce the adhesion rate of metal particles to the insulator surface, and improve the insulation reliability of the AC GIL equipment, the common solutions currently include laying particle traps near the insulator to capture free particles, coating the electrode surface to suppress the activity of free metal particles, and installing shielding electrodes on high-voltage conductors to drive away metal particles. 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 AC GIL equipment. By designing the structure of the grounded driving electrode near the AC GIL insulator, the electric field distribution and the stress of metal particles in the local area are changed, the adsorption trend of metal particles to the insulator surface under the action of the AC electric field is suppressed, and the metal particles are guided to move to a safe area, so as to realize the movement control of free metal particles in the pipeline. This method has the advantages of simple design, obvious driving effect, and easy industrialization. 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 provide a method for designing a metal particle driving electrode for an AC GIL insulator to solve the problem of metal particle adsorption inside a pipeline by an AC GIL insulator.

[0005] To achieve the above objectives, the present invention provides a method for designing a metal particle driving electrode for an AC GIL insulator. By optimizing the shape of the metal shell near the insulator, a wedge-shaped grounding electrode is added, the direction of the electric field near the insulator and the force conditions of the metal particles are changed, the movement characteristics of the metal particles are regulated, and their movement to the surface of the insulator is inhibited.

[0006] The technical solution proposed by the present invention is a method for designing a metal particle driving electrode for an AC GIL insulator, the method comprising the following steps:

[0007] Step 1: Build the simulation calculation model of AC GIL pot insulator and set the key parameters of the model;

[0008] Step 2: Based on the basin insulator model, analyze the electric-thermal-fluid multi-field coupling distribution around the GIL guide rod and insulator under operating conditions, analyze the stress of free metal particles in the pipeline under the multi-field coupling state, and establish a motion model of metal particles near the insulator;

[0009] Step 3: Set wedge-shaped driving electrodes with different angles on the inner surface of the insulator grounding shell, recalculate the AC electric field distribution of the GIL insulator, and couple 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 AC GIL grounding shell, and observe the effects of different driving electrode designs on the movement characteristics of metal particles near the convex and concave surfaces of the insulator, and statistically analyze the degree of adsorption of free metal particles by the insulator.

[0011] Furthermore, in step 1, the insulator model is a 500 kV AC GIL pot-type insulator, the insulator insulation distance is 160 mm, the insulator material is an epoxy resin / alumina composite material, and the relative dielectric constant is set to 5.

[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 an AC voltage of 500 kV, 50 Hz, 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, and the relative dielectric constant is 1.

[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 AC 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 height of the wedge-shaped driving electrode arranged on the inner surface of the insulator grounding shell is 3-5 mm, the angle between the driving electrode and the inner surface of the grounding shell is 2-10°, the material parameters of the driving electrode are consistent with the grounding shell, the potential is 0, and the driving electrode is respectively located on the convex and concave sides of the insulator grounding position.

[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 insulator surface is 10-30 mm, the release time of different particles on the convex and concave sides of the insulator is the same, and the particles move to the insulator surface and stop.

[0018] The beneficial effects brought by the present invention are:

[0019] Compared with traditional horizontal grounding electrodes, wedge-shaped grounding driving electrodes can effectively change the movement characteristics of metal particles near the insulator, drive the metal particles to a safe area, and protect the insulation performance of the insulator from being destroyed.

[0020] The method of the present invention can effectively inhibit the adsorption of nearby metal particles by insulators in AC GIL, prevent the occurrence of insulation failure accidents such as discharge and surface flashover caused by the adsorption of metal particles on the surface of the insulator, and improve the reliability and stability of high-voltage electrical equipment. The method has the advantages of simple design, obvious effect, and easy industrialization.

[0021] The present invention can enhance the expulsion effect of the basin-type insulator in the AC 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a 500kV AC GIL pot insulator and driving electrode model;

[0023] Figure 2 The AC electric field distribution of the insulator under different driving electrode design schemes;

[0024] Figure 3 To communicate the temperature and airflow distribution inside the GIL;

[0025] Figure 4Movement characteristics of metal particles near the insulator under different driving electrode design schemes. DETAILED DESCRIPTION

[0026] How the present invention is implemented is further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] A design of a metal particle driving electrode for an AC GIL insulator includes the following steps:

[0028] First, build a 500kV AC GIS pot-type insulator model, as shown in the attached figure. Figure 1 As shown in (a), the coaxial conductor is arranged parallel to the metal shell and kept parallel to the horizontal plane. The high-voltage conductor is connected to a 500kV, 50Hz AC voltage. Its voltage real-time amplitude changes periodically, which can be expressed by the following formula:

[0029]

[0030] Where U rms is the effective value of the AC voltage, f is the AC voltage frequency, which is set to 50Hz in this model. is the initial phase, t is the time, the unit is s. The metal shell is grounded. The pot insulator is set between the high-voltage conductor and the grounded shell, and plays an important role such as electrical insulation.

[0031] In order to achieve the goal of driving away the metal particles, two wedge-shaped driving electrodes are set near the grounding side insulator. Figure 1 As shown in (b), the material parameters and potential of the driving electrode are consistent with those of the grounded shell. The height of the driving electrode is h = 5mm, and the angle between it and the inner surface of the horizontal grounded shell is θ. Under different design schemes, the angle θ is set to 2°, 5° and 10° respectively. Spherical metal particles with a radius of r = 0.1mm are released on the inner surface of the grounded shell and released on both sides of the concave and convex surfaces of the insulator at the same time. The horizontal distance l from the insulator surface is 10, 20 and 30mm respectively.

[0032] Based on the obtained basin insulator model, the AC 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. For uniform insulators, the electric field distribution is highly non-uniform, and the electric field strength gradually decreases from the high-voltage conductor to the ground electrode. After laying wedge-shaped electrodes on the inner surface of the grounded shell near the insulator, the electric field distribution does not change significantly, and this design will not introduce new distorted electric field problems. Based on the AC GIL insulator model, the electric-thermal-fluid multi-physics coupling field distribution around the GIL guide rod and insulator under operating conditions is calculated, as shown in the attached figure. Figure 3 As shown, the temperature gradually decreases from the high-voltage conductor to the grounded shell, and gas circulation occurs inside the pipeline, affecting the movement characteristics of the metal particles inside the pipeline.

[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 grounded shell, and the amount of charge can be calculated by the following formula:

[0034]

[0035] In the formula, ε0 and ε r are vacuum and relative dielectric constants respectively, d is the particle size of spherical metal particles, E is the electric field strength at the location of the metal particles, and the Coulomb force Fq, gravity G, and electric field gradient force F acting on the metal particles are considered. grad As well as the effect of fluid force Fv, the real-time motion trajectory of metal particles under the transient action of AC electric field is calculated. The specific force conditions of 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; v g is the flow rate of SF6 insulating gas, m / s.

[0039] Based on the above metal particle motion model, spherical metal particles at different positions on the surface of the AC GIL grounding electrode are placed to simulate the motion characteristics of charged metal particles and the uniform insulator on the metal particles. The effect of the uniform insulator on the particle motion is shown in the attached figure. Figure 4 (a) As shown. Under the action of AC voltage, the metal particles released on the concave surface of the insulator show fluctuating movements, move toward the insulator and finally adsorb on the surface of the insulator. When released at different positions, the metal particles will move toward the insulator. The metal particles released on the convex surface of the insulator show different movement trends. When they are close to the surface of the insulator (l = 10mm), the metal particles move toward the surface of the insulator and adhere to it. When they are far away from the surface of the insulator, the metal particles no longer tend to move toward the surface of the insulator, and there will be no insulation damage caused by the particles adhering to the surface of the insulator.

[0040] Based on the above results of the uniform metal particle movement near the insulator, a wedge-shaped grounding driving electrode is added to release metal particles at the same position on the concave and convex surfaces of the insulator. The particle movement characteristics are shown in the attached figure. Figure 4 (bd) As shown in Figure 2, under the influence of the wedge-shaped electrode, the metal particles on the inner surface of the grounding shell are subjected to the electric field force component F away from the insulator surface in the axial direction. z As shown below:

[0041]

[0042] Under the action of the axial component of the electric field force, the motion state of the metal particles changes. After colliding with the wedge-shaped grounded driving electrode, its velocity component also moves away from the insulator. When θ=2°, all particles on the convex surface of the insulator can be driven away, but the particles on the concave surface still show a wave-like movement trend toward the insulator surface. When θ=5°, all particles on the convex surface of the insulator can be driven away, but the particles on the concave surface far away begin to show an obvious driving effect. Only the metal particles at the position away from the concave surface of the insulator (l=10mm) still move toward the insulator surface; when θ=10°, the particles at different positions on the convex and concave surfaces of the insulator all show a movement trend away from the insulator surface, and the particle driving effect is obvious. In summary, after adding the grounded wedge-shaped driving electrode, the axial force direction changes, thereby effectively inhibiting the adsorption of the insulator on the metal particles and improving the insulation performance of the insulator.

Claims

1. A method for designing a metal particle driving electrode for an AC GIL insulator, characterized in that: The following steps are involved: Step 1: Build a simulation model for AC GIL pot insulator; Step 2: Based on the basin insulator model, analyze the electric-thermal-fluid multi-field coupling distribution around the GIL guide rod and insulator under operating conditions, analyze the stress of free metal particles in the pipeline under the multi-field coupling state, and establish a motion model of metal particles near the insulator; Step 3: Set wedge-shaped driving electrodes with different angles on the grounded side of the insulator, recalculate the AC 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 surface of the AC GIL grounding shell, and observe the effects of different driving electrode designs on the movement characteristics of metal particles near the convex and concave surfaces of the insulator, and calculate the degree of adsorption of free metal particles nearby by the insulator; The included angle between the driving electrode and the inner surface of the grounded shell is 2-10°, the material and parameters of the driving electrode are consistent with those of the grounded shell, and the potential is 0; The driving electrodes are respectively located on the convex side and the concave side of the grounding position of the insulator.

2. The method for designing a metal particle driving electrode for an AC GIL insulator according to claim 1, characterized in that: In step 1, the insulator model is a 500 kV AC GIL pot-type insulator, the insulator insulation distance is 160 mm, the insulator material is an epoxy resin / alumina composite material, and the relative dielectric constant is set to 5.

3. The method for designing a metal particle driving electrode for an AC GIL insulator 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 an AC voltage of 500 kV and 50 Hz. The metal shell is grounded and the materials are all aluminum alloy.

4. The method for designing a metal particle driving electrode for an AC GIL insulator 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, and the relative dielectric constant is 1.

5. The method for designing a metal particle driving electrode for an AC GIL insulator 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 a metal particle driving electrode for an AC GIL insulator according to claim 1, characterized in that: In step 2, the metal particles are charged when in contact with the grounded shell under the action of AC 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 a metal particle driving electrode for an AC GIL insulator according to claim 1, characterized in that: In step 3, a wedge-shaped driving electrode with a height of 3-5 mm is set on the surface of the insulator grounding shell.

8. The method for designing a metal particle driving electrode for an AC GIL insulator 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 insulator surface is 10-30 mm. The release time of different particles on the convex and concave sides of the insulator is the same, and the particles move to the insulator surface and stop.

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