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RU-2861629-C1 - METHOD FOR MANUFACTURING NON-DETACHABLE HIGH-VOLTAGE BUSHING WITH COMPOSITE INSULATION FOR MEDIUM VOLTAGE CLASS OIL-FILLED POWER TRANSFORMER

RU2861629C1RU 2861629 C1RU2861629 C1RU 2861629C1RU-2861629-C1

Abstract

FIELD: electrical engineering. SUBSTANCE: invention relates to technologies for manufacturing non-condenser type non-detachable bushings with composite insulation for oil-filled power transformers of medium voltage classes. EFFECT: increasing the mechanical strength, quality and operational reliability of a high-voltage bushing for medium-voltage oil-filled transformers by creating a monolithic structure from composite materials without an internal cavity, eliminating the heterogeneity of the "glass fibre - binder" structure, improving the quality of its impregnation without air inclusions, reducing internal mechanical stresses and thereby increasing the physical and mechanical characteristics of the composite insulation under tension in the radial direction, especially during temperature changes (from minus 40°C to plus 90°C), as well as reducing material consumption, simplifying the assembly technology of the transformers themselves and their maintenance techniques. 9 cl, 5 dwg, 2 tbl, 5 ex

Inventors

  • Guseinov Gasan Abdulali ogly
  • Iarmarkin Mikhail Kirillovich
  • Guseinov Chingiz Gasan ogly

Dates

Publication Date
20260506
Application Date
20251114

Claims (9)

  1. 1. A method for manufacturing a high-voltage non-detachable bushing with composite insulation for an oil-filled medium-voltage power transformer, characterized in that a conductive sublayer based on a two-component liquid silicone in the presence of an adhesive is applied to the surface of a copper current-carrying conductor; the current-carrying conductor is installed coaxially in the central part of a bundle of unidirectional zero-twist glass threads; the glass thread bundle impregnated with a polymer binder with the current-carrying conductor installed therein is pulled through a heated cylindrical forming die at a speed of 0.5-1.0 m/s to obtain a primary cylindrical blank; A unidirectional zero-twist glass yarn impregnated with a polymer binder is wound onto the resulting primary cylindrical blank of the bushing insulating body with a current-carrying conductor installed therein using the row winding method at a winding speed of 18-30 m/min, forming a zone of threaded fastening of the grounded flange and a zone of application of the silicone sheath. During the drawing of the glass yarn bundle and the winding of the unidirectional glass yarn, the direction of laying of the unidirectional reinforcing glass yarns is ensured to be perpendicular to the vector of the electric field strength between the current-carrying conductor and the grounded flange; then, the blank obtained as a result of winding is subjected to thermal curing of the binder in a chamber under rotating conditions; mechanical processing is performed in the zone of threaded fastening of the grounded flange to impart precise dimensions and thread cutting; and an outer silicone sheath is applied to the blank under pressure using solid or liquid silicone rubber.
  2. 2. The method according to paragraph 1, characterized in that when winding unidirectional glass thread in the area where the silicone shell is applied, the thickness of the row winding over the primary cylindrical blank is provided to be 1.5-2.0 mm.
  3. 3. The method according to paragraph 1, characterized in that when winding unidirectional glass thread in the area of the threaded fastening of the grounded flange, the thickness of the row winding over the primary cylindrical blank is ensured to be up to 10 mm.
  4. 4. The method according to paragraph 1, characterized in that when pulling a unidirectional bundle of glass threads and winding a unidirectional glass thread, the ratio of the volumes of glass threads and polymer binder in the composition of the composite material is ensured in percent (75±5)/(25±5).
  5. 5. The method according to paragraph 1, characterized in that epoxy resin is used as the polymer binder.
  6. 6. The method according to paragraph 1, characterized in that the impregnation of the unidirectional glass thread with a polymer binder is carried out at a temperature of the impregnation bath with the binder of 60-80°C.
  7. 7. The method according to paragraph 1, characterized in that the drawing of the unidirectional glass thread with a polymer binder is carried out at a temperature of the heated forming die of 165±5°C and a binder curing time of 80 minutes.
  8. 8. The method according to paragraph 1, characterized in that the curing of the polymer binder is carried out at a chamber temperature of 165±5°C and a binder curing time of 50-80 minutes.
  9. 9. The method according to paragraph 1, characterized in that unidirectional glass thread of the EC6-200 or EC10-400 brand is selected for drawing and winding.

Description

The invention relates to electrical engineering, in particular to technologies for manufacturing non-detachable, non-capacitor-type bushings with composite insulation for oil-filled power transformers of medium voltage classes. Bushings are insulating structures of detachable and non-detachable design used in locations where a live metal conductor, such as a rod or pipe, must pass through the grounded metal enclosure of electrical equipment. The bushing provides mechanical fastening of the current-carrying conductor and the required level of electrical strength for the structure. Bushings operate under extremely harsh conditions. While one section of the bushing, located inside the transformer tank, is exposed to relatively high temperatures (up to 90°C and above) and oil, the other section, located above the cover, can be exposed to subzero temperatures (minus 40°C and below) and various aggressive substances in the surrounding environment. The detachable design of the input means that the current-carrying conductor can be removed from the input during maintenance or repair work. In the case of a non-detachable input, the current-carrying conductor is integral with the composite insulation of the input and cannot be separated from it. Analogue 1 A method is known for manufacturing transformer and switch bushings [1] of 35 kV voltage class with a composite or porcelain insulating cover and a non-detachable frame with RIP insulation (Resin Impregnated Paper). The manufacturing process includes the following stages: 1. Layers of crepe paper and aluminum foil are wound sequentially onto the current-carrying conductor, forming insulation with a system of capacitor plates. 2. The resulting input body blank is vacuumed and impregnated with epoxy compound. 3. The frame blank is heated and kept in the oven until the epoxy compound is completely polymerized. 4. The frame blank is turned to the required diameter. The bushing frame manufactured in this manner is equipped with a grounded flange and a cover made of a composite material (fiberglass with a silicone protective coating or porcelain). The current-carrying conductor has an upper contact for connection to external electrical networks and a lower contact for connection to the transformer winding taps. The lower part of the bushing, installed on the transformers, is immersed in oil and is always under slight overpressure created by the oil level in the conservator. A disadvantage of the described manufacturing method is that when impregnating the wound core, it is difficult to ensure penetration of the impregnating material into the thin layers between the capacitor plates. The manufacturing process is complex, requiring expensive equipment and highly qualified maintenance personnel. Analogue 2 The paper [2] describes the design of a bushing for oil-filled medium-voltage power transformers. In this design, a cylindrical composite insulation (fiberglass) manufactured by cross-winding unidirectional reinforcing glass thread impregnated with a polymer binder onto a mandrel of the appropriate diameter is used as a polymer insulating housing. A tracking- and weather-resistant ribbed protective silicone sheath is installed on top of the polymer insulating housing made of the composite material. The current-carrying conductor is installed in the internal cavity of the polymer insulating housing and is secured using upper and lower flanges and tightened using bolts. The current-carrying conductor has an upper contact for connection to external electrical networks and a lower contact for connection to the transformer winding taps. A metal flange with holes for fastening to the grounded transformer housing is installed on the outside of the middle part of the bushing. The bushing's interior contains an oil channel that connects the transformer's interior to the atmosphere through a special opening with a valve on the bushing's top cover. The oil in the bushing's interior is under slight excess pressure, created by the oil level in the expansion tank. The disadvantage of this design is that the fiberglass used as the composite insulating body of the transformer bushing is manufactured using the cross-winding method. During the winding process, reinforcing glass filaments impregnated with a polymer binder are laid onto the surface of a rotating mandrel of the appropriate diameter in a helical motion. The winding mandrel must have a shape and size that precisely matches the shape and size of the inner surface of the product being wound (the internal cavity of the input) and maintain these dimensions under all forces and temperatures during winding and curing. After thermal curing of the polymer binder, the finished product is machined to the required dimensions. The spiral winding of the internal composite insulation is accomplished by the reciprocating motion of the thread guide along a rotating mandrel. Under these conditions, the same thread repeatedly passes from one end