A dry-type distribution transformer medium and low voltage foil coil winding processing technology and dry-type transformer

Abstract

The present invention discloses a process for processing low-voltage foil-wound coils in a dry-type distribution transformer and a dry-type transformer thereof, comprising a coil winding process and an integral coil casting process, wherein the low-voltage winding body is spirally wound and comprises a metal foil strip, an interlayer insulation layer located on one side of the metal foil strip, and end insulation layers located at both ends of the metal foil strip. An inner insulating mesh layer is provided on the inner surface of the low-voltage winding body, and an outer insulating mesh layer is provided on the outer wall surface of the low-voltage winding body. The entire low-voltage winding body is coated with an epoxy resin casting layer, and the epoxy resin casting layer covers the inner and outer insulating mesh layers. The present invention optimizes and adds an insulating mesh layer to enhance the adhesion and stability of the surface epoxy resin casting layer, thereby achieving fully enclosed, integral insulation coverage of the entire winding, reducing the insulation failure cycle and increasing the product's service life.

Description

Technical Field

[0001] The present invention relates to the technical field of dry-type distribution transformers, and in particular to a winding processing technology for medium and low voltage foil wound coils of dry-type distribution transformers and the dry-type transformer. Background Art

[0002] Dry-type transformers are designed to penetrate deep into load centers while also being fireproof, explosion-proof, and environmentally friendly. With the increasing density of residential buildings and the proliferation of high-rise and underground structures, urban power supply loads are constantly growing, and dry-type transformers are becoming increasingly widespread. Dry-type transformers generally consist of low-voltage coils, high-voltage coils, an iron core, an insulating barrel, upper and lower spacers, and other components. After a period of operation, dust accumulates on the transformer surface and on the spacers. This is particularly serious in humid environments with salt spray. Long-term exposure to these conditions corrodes the low-voltage windings, and soluble substances in the contaminants on the transformer insulation gradually dissolve in water, forming a conductive film on the surface. This significantly reduces the insulation level of the insulation layer, making it susceptible to violent discharges under the influence of an electric field, known as flashover, which can damage the dry-type transformer. Summary of the Invention

[0003] In response to the above problems, the present invention aims to provide a processing technology for low-voltage foil-wound coil windings of dry-type distribution transformers and a dry-type transformer thereof, which optimizes the addition of an insulating mesh layer to increase the adhesion and stability of the surface epoxy resin casting layer, achieves fully enclosed overall insulation covering of the entire winding, reduces the insulation failure cycle, and increases the product service life.

[0004] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0005] A process for processing medium and low voltage foil coil windings of dry-type distribution transformers, comprising:

[0006] S1. Coil winding process: S1.1. Select a winding die of corresponding specifications according to the inner diameter of the product to be processed, install the winding die on the foil winding machine, and evenly apply a release agent on the outer surface of the winding die; S1.2. Surround the outer surface of the winding die with at least one circle of insulating mesh layer, and then wrap the interlayer insulating layer around the winding die for 2 to 5 circles, and then use the fastening belt to fix the metal foil with the inner end metal row welded to the specified position of the winding die, and complete the adjustment and tightening to make the metal foil in a tensioned state; S1.3. Match the corresponding end insulation layer and interlayer insulation layer according to the thickness of the metal foil. The interlayer insulation layer is located on the lower surface of the metal foil, and the end insulation layer is located at both ends of the metal foil. Synchronous winding; S1.4, continue to synchronously wind the metal foil, end insulation layer and interlayer insulation layer. When the size required by the process is reached, place the air duct support according to the process requirements; wherein, no air duct support is placed at the metal busbar; the air duct support is placed for at least one week; S1.5, complete the placement of the air duct support, continue to synchronously wind the metal foil, end insulation layer and interlayer insulation layer, complete the winding of the number of turns specified by the process, and complete the shearing of the metal foil; wherein, when winding the last turn of the metal foil, use a welding machine to weld the outer end metal row to the metal foil at the end position; S1.6, continue to wrap the interlayer insulation layer around the completed coil along the periphery for 2 to 5 seconds. The end insulation layer is wound one more time than the interlayer insulation layer, leaving a thermometer plug-in port. A layer of epoxy prepreg is wrapped around the outermost layer. S1.7: Dry the wound coil at a temperature of 140-160°C for 150-210 minutes. S1.8: After cooling, remove the coil from the winding mold, perform dimensional grinding and trimming, and form a semi-finished coil. S2: Cast the entire coil: S2.1: Place the coil in the inner mold, surround the outer surface of the coil with an insulating mesh layer, close the mold, and apply mold sealant to the joints. After mold sealing, age the coil at room temperature for 60-120 minutes. S2. 2. After aging is completed, pre-bake at a temperature of 100-120 degrees Celsius for 600-900 minutes, then cool to 60-80 degrees Celsius for more than 150 minutes; S2.3. Vacuum the coil encapsulation mold internally, control the vacuum degree at 1-2 mbar, and the temperature at 80-90 degrees Celsius for more than 120 minutes; S2.4. After vacuuming, connect the casting tubes of the coil encapsulation mold and complete the casting; S2.5. Cool and solidify, remove the encapsulation mold after casting, and pass at least one curing cycle; S2.6. After demolding and trimming, obtain the finished product.

[0007] Furthermore, the metal foil strip is a copper foil strip or an aluminum foil strip, and the metal busbar is a copper busbar.

[0008] Furthermore, in step S1.3, the gap between the end insulation layer and the metal foil is maintained at 1.5 mm to 2.0 mm.

[0009] Furthermore, in step S1.4, an insulating mesh layer is provided on the outer surface of the airway strut, and the airway strut is placed in 2 circles.

[0010] Furthermore, in step S2.4, the preparation of the casting material is completed before pouring, including: S2.41, preheating the epoxy resin and curing agent at a temperature of 60~70 degrees Celsius, and the preheating time is 660min~750min; S2.42, placing the preheated epoxy resin and curing agent in their respective preheating tanks, and continuing to preheat, the preheating temperature is 60~70 degrees Celsius, vacuuming, and the vacuum degree is controlled at 0.5~1mbar, and the holding time is 120~240min; S2.42, the temperature in the final mixing tank is maintained at 60~70 degrees Celsius, the vacuum degree is controlled at 1~2mbar, and the epoxy resin and curing agent in their respective preheating tanks are placed in the final mixing tank.

[0011] Furthermore, in step S2.4, the pouring rate is such that the pouring amount of a single pouring pipe shall not exceed 1 kg per stroke, and the maximum flow rate of each pouring head shall not exceed 50 kg / h.

[0012] Furthermore, in step S2.4, after pouring is completed, the vacuuming time is maintained for 10 to 30 minutes.

[0013] A dry-type transformer using low-voltage foil winding and epoxy resin casting includes a low-voltage foil winding coil winding processing technology for a dry-type distribution transformer.

[0014] It includes a low-voltage winding body, which is spirally ring-shaped. The low-voltage winding body includes a metal foil strip, an interlayer insulation layer located on one side of the metal foil strip, and end insulation layers located at both ends of the metal foil strip. The inner surface of the low-voltage winding body is provided with an inner insulating grid layer, and the outer wall surface of the low-voltage winding body is provided with an outer insulating grid layer. The low-voltage winding body as a whole is coated with an epoxy resin casting layer, and the epoxy resin casting layer covers the inner insulating grid layer and the outer insulating grid layer.

[0015] It also includes a plurality of heat dissipation air channels, which are located in the low-voltage winding body. An air channel insulation grid layer is provided on the side wall of the heat dissipation air channel, and the outer surface of the air channel insulation grid layer is covered with an epoxy resin casting layer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: optimizing the winding process, facilitating the subsequent epoxy resin casting molding; optimizing the processing technology of the low-voltage winding, adding an insulating grid layer to increase the adhesion and stability effect of the surface epoxy resin casting layer, and performing epoxy resin casting in a vacuum environment, which is conducive to forming an overall coverage of a fully enclosed epoxy resin casting layer, reducing the insulation failure cycle, and increasing the product service life.

[0017] The features of the present invention can be clearly understood by referring to the drawings and the following detailed description of preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 It is a partial cross-sectional structural diagram of the low-voltage winding body of the present invention;

[0020] Among them, 10, low-voltage winding body; 11, metal foil; 12, interlayer insulation layer; 13, end insulation layer; 20, heat dissipation duct; 30, outer metal busbar; 40, inner metal busbar; 50, epoxy resin casting layer; 61, outer insulation grid layer; 62, inner insulation grid layer; 63, air duct insulation grid layer. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific illustrations.

[0022] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are intended solely to illustrate the relative positional relationships and movement of components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly. Furthermore, references to "first," "second," and so on in the present invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one such feature.

[0023] Example 1

[0024] Combined with attachment Figures 1 to 2 As shown, this embodiment discloses a dry-type transformer using low-voltage foil winding and epoxy resin casting, including a low-voltage winding body 10. The low-voltage winding body 10 is spirally wound to form an internal hollow structure. The low-voltage winding body 10 is an elliptical structure as a whole and has an overall arc-shaped surface, which can well control the winding size.

[0025] Among them, the low-voltage winding body 10 includes a metal foil strip 11, an interlayer insulation layer 12 located on one side of the metal foil strip 11, and an end insulation layer 13 located at both ends of the metal foil strip 11. The metal foil strip 11 is made of copper foil strip or aluminum foil strip, and the metal foil strip 11 is preferably annealed before winding to eliminate internal stress and avoid cracking of the outer coating layer due to later deformation after the winding is cast, specifically to avoid cracking of the epoxy resin casting layer 50; the interlayer insulation layer 12 and the end insulation layer 13 are both made of DMD insulation paper, and the outermost side of the low-voltage winding body 10 is surrounded by 4 to 8 layers of interlayer insulation layers, and the outer side of the interlayer insulation layer 12 is surrounded by an outer insulation mesh layer 61 to increase the thickness of the outer surface insulation layer and improve the outer surface protection effect.

[0026] Preferably, an inner insulating mesh layer 62 is provided on the inner cavity surface of the low-voltage winding body 10, and an outer insulating mesh layer 61 is provided on the outer wall surface of the low-voltage winding body 10. The inner insulating mesh layer 62 and the outer insulating mesh layer 61 both use mesh cloth with a thickness of 1.0mm~1.5mm. The low-voltage winding body 10 as a whole is coated with an epoxy resin casting layer 50, and the epoxy resin casting layer 50 covers the inner insulating mesh layer 62 and the outer insulating mesh layer 61. The inner insulating mesh layer 62 and the outer insulating mesh layer 61 of the mesh structure can form good adhesion, so that the overall coating effect of the epoxy resin casting layer 50 is better, the adhesion stability is improved, and thus the service life is increased.

[0027] Preferably, a plurality of heat dissipation air ducts 20 are further included. The heat dissipation air ducts 20 are located in the low-voltage winding body 10. The heat dissipation air ducts 20 are a top-down through-structure. Before the epoxy resin is poured, they are usually filled and isolated with air duct plates. Then, 0.4mm~0.5mm thick mesh cloths are placed on both sides of the air duct plates to form an air duct insulation mesh layer 63, so that the side walls of the heat dissipation air ducts 20 are provided with an air duct insulation mesh layer 63, and the outer surface of the air duct insulation mesh layer 63 is covered with an epoxy resin pouring layer 50 to form a good adhesion effect.

[0028] In combination with the above, it also includes an inner metal bar 40 and an outer metal bar 30. The inner metal bar 40 is used to be welded and fixed to the metal foil strip 11 at the starting end inside the low-voltage winding body 10, and the outer metal bar 30 is used to be welded and fixed to the metal foil strip 11 at the outermost end of the low-voltage winding body 10. The heat dissipation ducts 20 are arranged at intervals with the two ends of the low-voltage winding body 10 between the inner metal bar 40 and the outer metal bar 30 as the starting and ending points. Several heat dissipation ducts 20 are arranged in a ring along the circumference, and the number of ring arrangements is at least 2 circumferences.

[0029] The present invention optimizes the low-voltage winding structure, adds an insulating grid layer to enhance the adhesion and stabilization effect of the surface epoxy resin casting layer, adopts an overall epoxy resin coating structure to form an overall coverage of a fully enclosed epoxy resin casting layer, reduces the insulation failure cycle, and increases the product service life.

[0030] Example 2

[0031] In combination with Example 1, this embodiment discloses a low-voltage foil-wound coil winding process for dry-type distribution transformers, including: S1, coil winding process, which requires equipment such as a foil winding machine, a sub-arc welding machine, an air compressor, and a crane; S1.1, familiarizing oneself with the coil drawing, clarifying its technical requirements, selecting a winding die of corresponding specifications according to the inner diameter of the product to be processed, preparing the required materials and tools according to the drawing, checking whether the equipment is normal, and only after it is correct can winding be carried out, installing the winding die on the foil winding machine, and evenly applying a release agent on the outer surface of the winding die; S1.2, winding At least one insulating mesh layer is wrapped around the outer surface of the wire die, and then the interlayer insulating layer is wrapped around the winding die for 2 to 5 times. The metal foil strip welded with the inner end metal row is then fixed and tied with a fastening tape at the specified position of the winding die, and the adjustment and tension are completed so that the metal foil strip is in a tensioned state. S1.3. The corresponding end insulation layer and interlayer insulation layer are matched according to the thickness of the metal foil strip. The interlayer insulation layer is located on the lower surface of the metal foil strip, and the end insulation layer is located at both ends of the metal foil strip to complete the synchronous winding. The gap between the end insulation layer and the metal foil strip is kept at 1.5mm~2.0mm. S1.4. Continue to wind the metal foil, end insulation layer and interlayer insulation layer synchronously. When the size required by the process is reached, place the air duct support bar according to the process requirements. No air duct support bar is placed at the metal busbar. The air duct support bar is placed for at least one week. An insulating grid layer is provided on the outer surface of the air duct support bar. The number of air duct support bars placed is preferably 2 weeks. S1.5. After the placement of the air duct support bar is completed, continue to wind the metal foil, end insulation layer and interlayer insulation layer synchronously, complete the winding of the number of turns specified by the process, and complete the shearing of the metal foil. When the last turn of the metal foil is wound, Use a welding machine to weld and fix the outer end metal bar to the metal foil strip; S1.6. Wrap the interlayer insulation layer around the completed coil along the outer circumference for 2 to 5 times, with the end insulation layer wrapped one more time than the interlayer insulation layer, retaining the thermometer plug interface, and wrap a layer of epoxy prepreg around the outermost layer; S1.7. Dry the completed coil at a temperature of 140 to 160 degrees Celsius for 150 to 210 minutes; S1.8. After cooling, demold the coil from the winding mold, grind and trim the size to form a semi-finished coil.

[0032] S2. The coil is cast as a whole: S2.1. The coil is placed in the inner film, and an insulating mesh layer is placed around the outer surface of the coil. The mold is then closed and the mold sealing glue is applied at the joints. After the mold sealing is completed, the coil is aged at room temperature for 60 to 120 minutes. S2.2. After the aging is completed, a pre-baking treatment is performed at a temperature of 100 to 120 degrees Celsius for 600 to 900 minutes, and then the temperature is lowered to 60 to 80 degrees Celsius for more than 150 minutes. S2.3. The mold for encapsulating the coil is internally vacuumed, and the vacuum degree is controlled at 1 to 2 mbar and the temperature is controlled at 80 to 90 degrees Celsius for more than 120 minutes. S2.4. After the vacuum treatment, the mold for encapsulating the coil is connected to the pouring pipe and the pouring is completed. S2.5. Cool and solidify, take out the encapsulated mold after casting, and pass at least one curing cycle. S2.6. After demolding and trimming, the finished product is obtained.

[0033] Furthermore, the metal foil strip is a copper foil strip or an aluminum foil strip, and the metal busbar is a copper busbar.

[0034] Furthermore, in step S2.4, the preparation of the casting material is completed before pouring, including: S2.41, preheating the epoxy resin and curing agent at a temperature of 60~70 degrees Celsius, and the preheating time is 660min~750min; S2.42, placing the preheated epoxy resin and curing agent in their respective preheating tanks, and continuing to preheat, the preheating temperature is 60~70 degrees Celsius, vacuuming, and the vacuum degree is controlled at 0.5~1mbar, and the holding time is 120~240min; S2.42, the temperature in the final mixing tank is maintained at 60~70 degrees Celsius, the vacuum degree is controlled at 1~2mbar, and the epoxy resin and curing agent in their respective preheating tanks are placed in the final mixing tank.

[0035] Furthermore, in step S2.4, the pouring rate is such that the pouring amount of a single pouring pipe shall not exceed 1 kg per stroke, and the maximum flow rate of each pouring head shall not exceed 50 kg / h.

[0036] Furthermore, in step S2.4, after pouring is completed, the vacuuming time is maintained for 10 to 30 minutes.

[0037] In the above, the casting materials are mainly epoxy resin and curing agent, and the auxiliary materials are release agent, polyethyl acetate, gypsum powder, xylene, alcohol and other materials. In the casting ratio, 100 parts of epoxy resin are matched with 80 parts of curing agent.

[0038] In the above, the sealing glue is made of gypsum powder with an appropriate amount of vinyl acetal glue and polyvinyl acetate until it becomes viscous. It is usually mixed with 100 parts of gypsum powder, 40 parts of polyvinyl acetal glue and 15 parts of polyvinyl acetate.

[0039] project tensile strength Bending strength Weak base effect Weak acid effect Strong acid effects Environmental level Power frequency withstand voltage to ground Low voltage ordinary foil winding 195Mpa 200Mpa erosion erosion erosion E1 7kV Low voltage foil wound epoxy resin cast winding 290Mpa 350Mpa Slightly affected none Small E2 level 10kV

[0040] The present invention optimizes the winding process, making it convenient to combine with the subsequent epoxy resin casting molding; optimizes the processing technology of the low-voltage winding, adds an insulating grid layer to increase the adhesion and stability effect of the surface epoxy resin casting layer, and performs epoxy resin casting in a vacuum environment, which is conducive to forming an overall coverage of the fully enclosed epoxy resin casting layer, reducing the insulation failure cycle, and increasing the product service life.

[0041] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the invention. Any simple modification, equivalent change or modification made to the above embodiment based on the technical principle of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A process for processing medium and low voltage foil coil windings of dry-type distribution transformers, characterized by: include, S1. Coil winding process: S1.

1. Select a winding die of corresponding specifications according to the inner diameter of the product to be processed, install the winding die on the foil winding machine, and evenly apply a release agent on the outer surface of the winding die; S1.

2. Surround the outer surface of the winding mold with at least one insulating mesh layer. Then wrap the interlayer insulating layer around the winding mold 2 to 5 times. Then, use a fastening tape to secure the metal foil strip welded with the inner end metal strip to the specified position on the winding mold. Adjust and tighten the metal foil strip to keep it in a tensioned state. S1.

3. Match the end insulation layer and interlayer insulation layer according to the thickness of the metal foil. The interlayer insulation layer is located on the bottom surface of the metal foil, and the end insulation layer is located at both ends of the metal foil to complete synchronous winding. S1.

4. Continuously and synchronously wind the metal foil, end insulation layer, and interlayer insulation layer. When the dimensions required by the process are reached, place airway stays according to the process requirements. Airway stays are not placed on the metal busbars. Airway stays are placed for at least one full circle. S1.

5. After placing the airway stays, continue to wind the metal foil, end insulation layer, and interlayer insulation layer simultaneously, completing the number of turns specified by the process, and then shearing the metal foil. When winding the last turn of the metal foil, weld the outer end metal bar to the metal foil at the end using a welder. S1.

6. Wrap the interlayer insulation layer around the completed coil 2 to 5 times along the outer circumference. The number of turns of the end insulation layer should be one more than the interlayer insulation layer. Keep the thermometer plug-in interface, and wrap a layer of epoxy prepreg around the outermost layer. S1.

7. Dry the coil after winding at a temperature of 140-160 degrees Celsius for 150-210 minutes. S1.

8. After cooling, the coil is demoulded and separated from the winding die, and the size is polished and trimmed to form a semi-finished coil; S2. Coil integral casting: S2.

1. Place the coil in the inner film and surround the outer surface of the coil with an insulating mesh layer. Then complete the mold closing and fill the joints with mold sealing glue. After the mold sealing is completed, age at room temperature for 60-120 minutes. S2.

2. After aging, pre-bake at a temperature of 100-120 degrees Celsius for 600-900 minutes, then cool to 60-80 degrees Celsius for more than 150 minutes. S2.

3. The mold for encapsulating the coil is vacuumed, with the vacuum degree controlled at 1-2 mbar and the temperature controlled at 80-90 degrees Celsius for more than 120 minutes. S2.

4. After the vacuum treatment, the mold for encapsulating the coil is connected to the casting pipe and the casting is completed; S2.

5. Cool and solidify, remove the cast package mold, and allow it to go through at least one curing cycle; S2.

6. After demoulding and trimming, the finished product is obtained.

2. A process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 1, characterized in that: The metal foil strips are copper foil strips or aluminum foil strips, and the metal busbars are copper busbars.

3. The process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 2, characterized in that: In step S1.3, the gap between the end insulation layer and the metal foil tape is maintained at 1.5 mm to 2.0 mm.

4. The process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 1, characterized in that: In step S1.4, an insulating mesh layer is provided on the outer surface of the airway struts, and the airway struts are placed for 2 weeks.

5. The process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 1, characterized in that: In step S2.4, the preparation of the casting material is completed before pouring, including: S2.41, preheating the epoxy resin and curing agent at a temperature of 60-70 degrees Celsius, respectively, and the preheating time is 660min-750min; S2.42, placing the preheated epoxy resin and curing agent in their respective preheating tanks, and continuing to preheat, the preheating temperature is 60-70 degrees Celsius, vacuuming, and the vacuum degree is controlled at 0.5-1mbar, and the holding time is 120-240min; S2.42, the temperature in the final mixing tank is maintained at 60-70 degrees Celsius, the vacuum degree is controlled at 1-2mbar, and the epoxy resin and curing agent in their respective preheating tanks are placed in the final mixing tank.

6. The process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 5, characterized in that: In step S2.4, the pouring rate is such that the pouring amount of a single pouring pipe shall not exceed 1 kg per stroke, and the maximum flow rate of each pouring head shall not exceed 50 kg / h.

7. The process for processing medium and low voltage foil coil windings of dry-type distribution transformers according to claim 6, characterized in that: In step S2.4, after pouring is completed, the vacuum time is maintained for 10 to 30 minutes.

8. A low-voltage foil-wound epoxy resin cast dry-type transformer, characterized by: The invention comprises a process for processing low-voltage foil-wound coil windings of a dry-type distribution transformer as described in any one of claims 1 to 7.

9. The low-voltage foil-wound epoxy resin cast dry-type transformer according to claim 8, characterized in that: It includes a low-voltage winding body, which is spirally ring-shaped. The low-voltage winding body includes a metal foil strip, an interlayer insulation layer located on one side of the metal foil strip, and end insulation layers located at both ends of the metal foil strip. The inner surface of the low-voltage winding body is provided with an inner insulating grid layer, and the outer wall surface of the low-voltage winding body is provided with an outer insulating grid layer. The low-voltage winding body as a whole is coated with an epoxy resin casting layer, and the epoxy resin casting layer covers the inner insulating grid layer and the outer insulating grid layer.

10. The low-voltage foil-wound epoxy resin cast dry-type transformer according to claim 9, characterized in that: It also includes a plurality of heat dissipation air channels, which are located in the low-voltage winding body. An air channel insulation grid layer is provided on the side wall of the heat dissipation air channel, and the outer surface of the air channel insulation grid layer is covered with an epoxy resin casting layer.

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