Method for improving corona at end part of stator winding of large generator

Abstract

The invention discloses a large generator stator winding end portion corona improvement method, and belongs to the technical field of high voltage motor insulation, and the method comprises the steps: 1) based on a dry ice cleaning technology, using dry ice cleaning equipment, dry ice particles, an L-shaped metal nozzle and other tools to clean a stator winding end portion insulation surface; (2) high-performance putty-shaped nano modified epoxy resin glue is evenly smeared on gaps and corner angles of the insulation surface of the winding, and the smeared surface is trimmed into a smooth R corner; 3) locally filling air gaps on the insulating surface of the winding by using a polyester felt dipped with room-temperature curing epoxy resin glue, and smearing the surface of the filled part by using nano modified epoxy resin glue; and 4) spraying non-linear semiconductor high-resistance anti-corona paint on the insulating surface of the winding. The method has a remarkable effect of improving the corona problem of the end part of the stator winding of the large generator, and has the advantages of wide coverage, high universality, high efficiency and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage motor insulation, and in particular relates to a method for improving corona at the end of a stator winding of a large generator. Background Art

[0002] As we all know, the corona problem at the end of the stator winding of a large generator is one of the more common and difficult technical problems in the industry, especially in generators that use air as the cooling medium or in generators that use impregnated glass strands to tie and fix the stator winding ends. Because after the impregnated glass strands and other binding materials used in such generators are cured, the sharp corners and burrs formed on the insulation surface and other raised parts have a more concentrated electric field strength when the unit is running, making the electric field distribution at the end of the stator winding uneven, so corona discharge is prone to occur. And as large-scale generator sets develop towards higher voltage levels and larger rated capacities, the risk of corona discharge at the end of the stator winding is gradually increasing. Corona discharge will cause electrical corrosion on the insulation surface of the generator stator winding, which will reduce the life of the generator insulation system. The winding corona problem will bring great hidden dangers to the safe and stable operation of the generator. In recent years, the industry has paid more and more attention to the improvement methods of the corona problem at the end of the generator stator winding.

[0003] The traditional method to solve the corona problem at the end of the generator stator winding is to "manually polish the insulating surface where the corona discharge occurs, wipe it with solvents such as alcohol, and then apply insulating covering paint on the surface of the corona discharge area." However, this solution has a general effect on improving corona, is inefficient, and is time-consuming and labor-intensive. In addition, due to the limitation of operating space, the traditional manual corona treatment method does not thoroughly clean the areas between the upper and lower layers of the wire rods at the end of the generator stator winding and within the insulating folds, which can easily cause residual corona discharge and incomplete corona treatment.

[0004] Therefore, it is urgent to invent a method for improving the corona at the end of a large generator stator winding, which has obvious corona improvement effect, is scientific and reasonable, has strong versatility, is easy to operate, and has high efficiency. Summary of the invention

[0005] The present invention aims to solve the corona problem on the insulating surface of the stator winding end of a large generator, and provides a method for improving the corona on the stator winding end of a large generator based on a dry ice cleaning process. The method has the advantages of obvious corona improvement effect, scientific rationality, strong versatility, convenient operation, wide coverage, and high efficiency.

[0006] To achieve the above object, the technical solution of the present invention is specifically described as follows:

[0007] S1. Use dry ice cleaning equipment and dry ice particles, fix the non-standard L-shaped metal nozzle on the spray gun through the threaded joint, turn on the power, adjust the dry ice blasting pressure and dry ice blasting volume through the control switch, adjust the dry ice blasting distance and dry ice blasting angle through the spray gun and dry ice tube, use the compressed air in the spray gun to blow the low-temperature and high-speed moving dry ice particles to the insulation surface of the stator winding end of the large generator for dry ice cleaning, and eliminate the sharp corners and burrs on the insulation surface of the stator winding end and the dirt in the folds of the insulation surface, where the insulation surface includes the upper stator wire rod, the lower stator wire rod, the bevel pad, the glass fiber bundle binding rope, and the outer surface of the interlayer conformable material;

[0008] S2. Evenly apply the high-performance putty-like nano-modified epoxy resin glue to the gaps and corners of the insulation surface of the end of the generator stator winding. The corners are the corners of the contact area between the bevel pad and the upper stator wire rod. Use a scraper, a scraper hammer and other tools to trim the surface filled with the high-performance putty-like nano-modified epoxy resin glue into a smooth R angle, and cure it;

[0009] S3. Use polyester felt impregnated with room temperature curing epoxy resin glue to partially fill the air gaps generated on the insulation surface of the stator winding end during the assembly process. The compression amount of the polyester felt is 50%. The air gaps are caused by the inconsistency between the glass fiber bundle binding rope and the stator wire rod and the bevel pad. Use high-performance putty-like nano-modified epoxy resin glue to smoothly and evenly apply it on the surface of the polyester felt filling part. Be careful not to have raised residual glue, and cure it.

[0010] S4. Spray the entire insulation surface of the stator winding end of the generator with one or two coats of nonlinear semiconductor high-resistance anti-corona paint, and cure it.

[0011] In the above-mentioned method for improving corona at the end of the stator winding of a large generator, in S1, the air supply pressure of the dry ice cleaning equipment is 0.6-0.7 MPa, the particle size of the dry ice particles is 3 mm, the diameter of the non-standard L-shaped metal nozzle is 10 mm, the dry ice blasting pressure is 0.6-0.7 MPa; the dry ice blasting amount is 1-2 kg / min; the dry ice blasting distance is 50-300 mm, and the dry ice blasting angle is 45-60°.

[0012] In the above-mentioned method for improving the corona of the stator winding end of a large generator, in S2 and S3, the high-performance putty-like nano-modified epoxy resin glue is composed of a mixture of epoxy resin containing nano-fillers and a curing agent, and the insulation heat resistance grade is F grade. The viscosity of the mixture is 55000-70000 mPa·s, the thixotropic value is greater than 6.5, the dielectric strength is greater than 15 MV / m, and the volume resistivity is greater than 10 12Ω·m, tensile shear strength greater than 25MPa, pot life greater than 1h, and curing time less than 24h.

[0013] In the above-mentioned method for improving the corona at the end of the stator winding of a large generator, in S3, the polyester felt is composed of polyester fibers, and its insulation heat resistance grade is Class B and its tensile strength is greater than 5N / cm 2 , the elongation at break is less than 40%.

[0014] In the above-mentioned method for improving corona at the end of the stator winding of a large generator, in S3, the solvent-free room temperature curing epoxy resin glue is composed of a mixture of a low-viscosity epoxy resin and a curing agent, wherein the viscosity of the low-viscosity epoxy resin is 2000-5000 mPa·s, the insulation heat resistance grade of the mixture is F grade, the dielectric strength is greater than 20 MV / m, and the volume resistivity is greater than 10 5 MΩ·m, surface resistivity greater than 10 7 MΩ, bending strength greater than 70MPa, impact strength greater than 7kJ / m 2 , the applicable period is greater than 30 minutes and the curing time is less than 24 hours.

[0015] In the above-mentioned large generator stator winding end corona improvement method, in S4, the nonlinear semiconductor high resistance anti-corona paint is composed of epoxy resin, curing agent and silicon carbide, which is a single-component fast curing air-drying paint, and its main performance parameters are: surface resistivity 5.5×10 2 ~5.5×10 5 MΩ, solid content greater than 50%, pot life greater than 4h, drying time less than 24h.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention changes the traditional method of dealing with the corona problem at the end of the stator winding of a large generator. The present invention is based on the dry ice cleaning process, and its principle is: using compressed air to blow low-temperature dry ice particles to the surface of the object to be cleaned, so that the adhesion of dirty impurities becomes poor, and then under the impact of the high-speed moving dry ice particles, the sharp corners and burrs on the insulating surface, dirty impurities are separated from the surface of the object to be cleaned, and are removed with the high-speed airflow. The present invention cleans the sharp corners and burrs and dirty impurities on the insulating surface more thoroughly, and the corona residue is greatly reduced. It can eliminate the corona discharge problem at the end of the stator winding caused by the local electric field concentration at the sharp corners and burrs and dirty impurities, so that the insulating surface of the stator winding end is smooth and flat without protrusions, and then optimizes the electric field distribution on the insulating surface of the stator winding end, which has a more significant effect on corona improvement;

[0018] 2. The present invention fills and applies high-performance putty-like nano-modified epoxy resin glue to the gaps and corners of the insulation surface of the end of the generator stator winding, and repairs the surface of the filled and applied epoxy resin glue into a smooth R angle to reduce the local electric field intensity concentration at the gaps and corners of the insulation surface, thereby increasing the corona discharge starting voltage and effectively suppressing corona discharge;

[0019] 3. The present invention uses polyester felt impregnated with solvent-free room temperature curing epoxy resin glue to partially fill the air gap generated on the insulation surface of the stator winding end during the assembly process, and uses high-performance putty-like nano-modified epoxy resin glue to smoothly and evenly apply the surface of the filling part. The present invention can eliminate corona discharge in the local air gap;

[0020] 4. The present invention sprays the insulating surface of the entire stator winding end of the generator with one or two coats of nonlinear semiconductor high-resistance anti-corona paint, which can further optimize the overall electric field distribution of the stator winding end, weaken the concentration of electric field intensity, inhibit corona discharge, reduce the number of corona discharge photons, increase the corona starting voltage of the generator stator winding, and improve the corona problem at the stator winding end.

[0021] 5. The present invention has a significant effect on improving the corona problem at the ends of stator windings of large generators, can extend the life of the generator insulation system, and improve the operating stability of the generator set. It has the advantages of being scientific and reasonable, having good effects, strong versatility, wide coverage, and high operating efficiency. The present invention has successfully helped some generator sets improve the corona problem at the ends of stator windings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is an overall schematic diagram of the present invention;

[0023] Figure 2 for Figure 1 A partial schematic diagram of the insulation surface of the stator winding end;

[0024] Figure 3 for Figure 2 A partial enlarged main view of the .

[0025] Explanation of the marks in the attached drawings: 1-dry ice cleaning equipment; 2-power supply; 3-control switch; 4-dry ice particles; 5-spray gun; 6-metal nozzle; 7-L-shaped metal nozzle; 8-insulation surface of the stator winding end; 9-upper stator wire rod; 10-lower stator wire rod; 11-bevel pad; 12-glass fiber bundle binding rope; 13-interlayer conformable material; 14-dry ice tube; 15-smooth R angle. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different structures.

[0027] Example 1

[0028] This embodiment provides a method for improving the corona at the end of the stator winding of a large generator. Figure 1 , Figure 2 , Figure 3 As shown, the following steps are included:

[0029] S1. Turn on the power supply 2 of the dry ice cleaning equipment 1, put the dry ice particles 4 into the container, and fix the metal nozzle 6 on the spray gun 5 through the threaded joint. Due to the limitation of the operating space, the metal nozzle 6 on the spray gun 5 can be replaced with an L-shaped metal nozzle 7 when cleaning the interlayer conformable material 13. The dry ice spraying pressure is 0.6-0.7MPa and the dry ice spraying amount is adjusted to 1-2kg / min by controlling the switch 3. The spray gun 5 is held, and the dry ice spraying distance is adjusted to 50-300mm and the dry ice spraying angle is adjusted to 45-60° through the spray gun 5 and the dry ice tube 14. The impact of the compressed air in the spray gun 5 is used to spray the low-temperature and high-speed moving dry ice particles. The particles 4 are blown onto the insulating surface 8 of the end of the stator winding of a large generator for dry ice cleaning, wherein the insulating surface 8 includes the outer surface of the upper stator wire rod 9, the lower stator wire rod 10, the bevel pad 11, the glass fiber bundle binding rope 12, and the interlayer conformable material 13. The cleaning standard is to just ensure that the insulating surface 8 of the stator winding end is not damaged and to achieve the ideal cleaning effect. When cleaning, it should be noted that mobile sweeping should be performed, and continuous spraying cleaning should not be performed on the same position, so as to eliminate the sharp corners and burrs on the insulating surface 8 of the stator winding end and the dirt in the insulating folds, so that they are removed with the high-speed airflow, so that the insulating surface 8 is smooth, flat, and has no protrusions;

[0030] S2. After the high-performance putty-like nano-modified epoxy resin glue is uniformly stirred into a putty-like mixture, the putty-like mixture is uniformly filled and applied to the gaps and corners of the insulating surface 8 of the stator winding end of the generator using a glue injection gun. The corners are the corners of the contact area between the bevel pad 11 and the upper stator wire rod 9. A scraper and a scraper hammer are used to trim the surface filled and applied with the high-performance putty-like nano-modified epoxy resin glue into a smooth R angle 15, and the curing is completed;

[0031] S3. Use a stirring rod to stir the solvent-free room temperature curing epoxy resin glue evenly, and use polyester felt impregnated with room temperature curing epoxy resin glue to partially fill the air gap generated on the insulating surface 8 of the stator winding end during the assembly process, wherein the compression amount of the polyester felt is 50%, and the air gap is caused by the incompatibility between the glass fiber bundle binding rope 12 and the stator wire rod 9 and the bevel pad 11, and use a high-performance putty-like nano-modified epoxy resin glue to smoothly apply the surface of the filling part and cure it. It should be noted that no raised residual glue should appear;

[0032] S4. Use a stirring rod to stir the nonlinear semiconductor high-resistance anti-corona paint evenly, spray the entire stator winding end insulation surface 8 of the generator with the nonlinear semiconductor high-resistance anti-corona paint once or twice, and cure it to further optimize the overall electric field distribution of the stator winding end.

[0033] The high-performance putty-like nano-modified epoxy resin adhesive is composed of a mixture of epoxy resin containing nano-fillers and a curing agent, and has an insulation heat resistance grade of F, a viscosity of the mixture of 55000-70000 mPa·s, a thixotropic value greater than 6.5, a dielectric strength greater than 15 MV / m, and a volume resistivity greater than 10 12 Ω·m, tensile shear strength greater than 25MPa, applicable period greater than 1h, curing time less than 24h, the mixture has fine particle size and excellent conformability.

[0034] The polyester felt is composed of polyester fibers, and its insulation heat resistance grade is B grade, and its tensile strength is greater than 5N / cm 2 , the elongation at break is less than 40%.

[0035] The solvent-free room temperature curing epoxy resin adhesive is composed of a mixture of a low-viscosity epoxy resin and a curing agent, wherein the viscosity of the low-viscosity epoxy resin is 2000-5000 mPa·s, the insulation heat resistance grade of the mixture is F grade, the dielectric strength is greater than 20 MV / m, and the volume resistivity is greater than 10 5 MΩ·m, surface resistivity greater than 10 7 MΩ, bending strength greater than 70MPa, impact strength greater than 7kJ / m 2 , the applicable period is greater than 30 minutes and the curing time is less than 24 hours.

[0036] The nonlinear semiconductor high resistance anti-corona paint is composed of epoxy resin, curing agent and silicon carbide, and is a single-component fast curing air-drying paint with a surface resistivity of 5.5×10 2 ~5.5×10 5 MΩ, solid content greater than 50%, applicable period greater than 4h, drying time less than 24h, the paint film surface is complete and uniform without defects after drying.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving corona at the end of stator winding of a large generator, characterized in that: The steps include: S1. Use dry ice cleaning equipment (1) and dry ice particles (4) to fix a non-standard L-shaped metal nozzle (7) on a spray gun (5) through a threaded joint, adjust the dry ice spray pressure and dry ice spray volume through a control switch (3), adjust the dry ice spray distance and dry ice spray angle through the spray gun (5) and a dry ice tube (14), use the compressed air in the spray gun (5) to blow the low-temperature and high-speed moving dry ice particles (4) to the insulating surface (8) of the stator winding end of a large generator for dry ice cleaning, and eliminate the sharp corners, burrs and dirt on the insulating surface (8) of the stator winding end, wherein the insulating surface (8) includes the outer surface of the upper stator wire rod (9), the lower stator wire rod (10), the bevel pad (11), the glass fiber bundle binding rope (12), and the interlayer conformable material (13); S2, evenly apply the high-performance putty-like nano-modified epoxy resin glue to the gaps and corners of the insulation surface (8) of the end of the generator stator winding, where the corners are the corners of the contact area between the bevel pad (11) and the upper stator wire rod (9), and use a scraper to trim the surface of the high-performance putty-like nano-modified epoxy resin glue into a smooth R angle (15); S3, using polyester felt impregnated with room temperature curing epoxy resin glue to partially fill the air gap generated on the insulation surface (8) of the stator winding end during the assembly process, wherein the compression amount of the polyester felt is 50%, and a high-performance putty-like nano-modified epoxy resin glue is used to smoothly apply the surface of the filling part, and the air gap is caused by the lack of fit between the glass fiber bundle binding rope (12) and the upper stator wire rod (9) and the bevel pad (11); S4. Spraying the entire insulating surface (8) of the stator winding end with one or two coats of nonlinear semiconductor high-resistance anti-corona paint.

2. The method for improving corona at the end of a large generator stator winding according to claim 1 is characterized in that: In S1, the air supply pressure of the dry ice cleaning equipment (1) is 0.6-0.7 MPa, the particle size of the dry ice particles (4) is 3 mm, the diameter of the non-standard L-shaped metal nozzle (7) is 10 mm, the dry ice blasting pressure is 0.6-0.7 MPa; the dry ice blasting amount is 1-2 kg / min; the dry ice blasting distance is 50-300 mm, and the dry ice blasting angle is 45-60°.

3. The method for improving corona at the end of a large generator stator winding according to claim 1 is characterized in that: In S2 and S3, the high-performance putty-like nano-modified epoxy resin adhesive is composed of a mixture of epoxy resin containing nano-fillers and a curing agent, and the insulation heat resistance grade is F grade. The viscosity of the mixture is 55000-70000 mPa·s, the thixotropic value is greater than 6.5, the dielectric strength is greater than 15 MV / m, and the volume resistivity is greater than 10 12 Ω·m, tensile shear strength greater than 25MPa, pot life greater than 1h, and curing time less than 24h.

4. The method for improving corona at the end of a large generator stator winding according to claim 1 is characterized in that: In S3, the polyester felt is composed of polyester fibers, and its insulation and heat resistance grade is B, and its tensile strength is greater than 5N / cm 2 , the elongation at break is less than 40%.

5. The method for improving corona at the end of a large generator stator winding according to claim 1 is characterized in that: In S3, the solvent-free room temperature curing epoxy resin glue is composed of a mixture of a low viscosity epoxy resin and a curing agent, wherein the viscosity of the low viscosity epoxy resin is 2000-5000 mPa·s, the insulation heat resistance grade of the mixture is F grade, the dielectric strength is greater than 20 MV / m, and the volume resistivity is greater than 10 5 MΩ·m, surface resistivity greater than 10 7 MΩ, bending strength greater than 70MPa, impact strength greater than 7kJ / m 2 , the applicable period is greater than 30 minutes and the curing time is less than 24 hours.

6. The method for improving corona at the end of a large generator stator winding according to claim 1 is characterized by: In S4, the nonlinear semiconductor high resistance anti-corona paint is composed of epoxy resin, curing agent and silicon carbide, which is a single-component fast curing air-drying paint, and its main performance parameters are: surface resistivity 5.5×10 2 ~5.5×10 5 MΩ, solid content greater than 50%, pot life greater than 4h, drying time less than 24h.

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