DESCRIPTION OF THE RELATED ART A conventional CTC is wrapped by an insulation paper in the outmost layer, which influences heat exchange and increases size of windings of the transformer.

The European Patent EP 0746 861 B 1 discloses a structure of wrapping CTC by using a woven strip dipping with epoxy resin. The warp and weft of the woven strips are formed with polyester or mixed glass silk/polyester. In such a way, heat exchange problem is partially solved. However, when the CTC is wrapped by using the woven strip dipping with epoxy resin, there are the following problems: polyester, as an ingredient of the woven strip, will hydrolyzed, i. e. when used in transformer oil, especially at working temperature of 80-100 C, the polyester material will dissolve gradually and even disappear thoroughly. Therefore, this polyester fabric mesh strip, used as binding strip, has problems in terms of long-term use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a CTC mainly used in large-scale transformers and wrapped by glass fiber net tape, so that its construction and performance can be maintained all the time when it is used so as to avoid hydrolyzation.

Another object of the present invention is to provide a method for manufacturing and using the CTC used in large-scale transformers and having the above mentioned characteristics.

In order to achieve the above objects, the present invention provides a CTC for transformer, wherein an outer surface of the CTC is wrapped by a glass fiber net tape.

Preferably, this CTC includes a first row of enameled wires and a second row of enameled wires, each row of which includes multiple enameled wires. The first

row of enameled wires pass through the second row of enameled wires via a bend.

The second row of enameled wires pass through the first row of enameled wires via another bend. These two rows of wires remain parallel all the time, so that transposition between the first row of enameled wires and the second row of enameled wires can be carried out.

Preferably, the glass fiber net tape is processed by immersing into a self-adhesive epoxy resin to enable the glass fiber net tape to be bonded to the CTC.

Preferably, the glass fiber net tape is wrapped by an insulation paper. More preferably, continuous threads are added between the glass fiber net tape and the insulation paper.

Preferably, the first and second rows of enameled wires are enlaced by the glass fiber net tape at a certain angle.

Preferably, the glass fiber net tape includes multiple warp glass fiber threads and multiple weft glass fiber threads. The warp glass fiber threads wind around weft glass fiber threads and they are braided and twisted by each other.

Preferably, the above mentioned CTC winds around a shaft.

The present invention further provides a method for manufacturing a glass fiber net tape CTC, comprising the steps of : preparing enameled wires; transposing said enameled wires together to form CTC; and winding obliquely glass fiber net tape on the periphery of the CTC.

Preferably, the aforesaid method further comprises the following step: wrapping insulation paper and threads on the outer layer of the glass fiber net tape CTC.

Preferably, the aforesaid method further comprises the following step: winding contractedly the glass fiber net tape CTC on the shaft.

The present invention further provides a method for using the glass fiber net tape CTC, comprising the steps of : releasing gradually the glass fiber net tape CTC wound around the shaft; bending the cable and removing the insulation paper and threads on the outer layer of the glass fiber net tape CTC; helically winding to form windings; heating to integrate the glass fiber net tape with the CTC.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view schematically showing the structure of the CTC in

the present invention ; Figs. 2A and 2B show a preferable structure of the glass fiber net tape for the CTC; and Fig. 3 is an analysis view schematically showing the force when the glass fiber net tape is wound, wherein Fig. 3A is an analysis view schematically showing the force when it is wound straightly and Fig. 3B is an analysis view schematically showing the force when it is wound obliquely.

DESCRIPTION OF THE PREFERRED EMBODEMENTS The invention will be described in combination of some preferable embodiments. It should be understood that these preferable embodiments are not limitation to the invention.

With reference to Fig. 1, it is a perspective view schematically showing the structure of the CTC in the present invention. In one preferable embodiment of the present invention, a CTC for transformer is provided, which comprises a first row of enameled wires 1 and a second row of enameled wires 2, each row of which includes multiple enameled wires 3. The first row of enameled wires 1 pass through the second row of enameled wires via a bend 4. The second row of enameled wires 2 pass through the first row of enameled wires 1 via another bend 4. Thus, transposition between the first row of enameled wires 1 and the second row of enameled wires 2 can be carried out. An outer surface of the CTC consisting of the first row of enameled wires 1 and the second row of enameled wires 2 is wrapped by a glass fiber net tape 5.

The glass fiber net tape 5 can be immersed into epoxy resin, so that the glass fiber net tape is capable to be bonded to the CTC.

The glass fiber net tape is wrapped by an insulation paper. Preferably, continuous threads are added between the glass fiber net tape and the insulation paper.

The periphery of the CTC is wrapped obliquely by the prepared glass fiber net tape 5 at a certain angle to cover the surface of the CTC, of which structure is shown in Fig. 1.

With reference to Figs. 2A and 2B, a preferable structure of the glass fiber net tape 5 is shown.

In consideration of various using requirements of the glass fiber net tape CTC and performances of raw material of glass fiber etc., the present invention uses, but is not limited to, the glass fiber net tape having the following properties as wrapping

material: Glass Fiber: No-alkali electronic degree-glass type Mesh Size: 3mmx3mm Base weight of the glass fiber not processed: >60g/m2 Tensile Strength: Warp : >800N/30mm width Weft: >1000N/30mm width Width of the net tape: 30mm (adjustable depending on the applying conditions) As shown in Figs. 2A and 2B, warp glass fibers 51a-51d, for example, include three or four fibers, in which warp glass fibers 51a and 51b are twisted around weft glass fibers 52a-52d, warp glass fiber 51c, or warp glass fiber 51c and 51d, as intensifying fiber, reinforces a structure constituted by warp glass fibers 5 la, 51b and weft glass fibers 52a, 52b, and warp glass fibers 51a, 51b and weft glass fibers 52c, 52d. Thus, the whole glass fiber net tape gathers to be a tight integrity so as to ensure mechanical intensity and stability of the structure.

According to the glass fiber net tape having the aforesaid preferable structure, the wrapping stability of the glass fiber net tape is improved in the present invention, so as to ensure that the whole glass fiber net tape remains undistorted when the glass fiber net tape CTC is wound to form a winding, so as to improve mechanical intensity of the glass fiber net tape CTC.

The glass fiber net tape, having the aforesaid structure, is wrapped full-automatically and obliquely. As shown in Fig. 1, the surface of the whole CTC can be covered full-automatically and continuously in such a wrapping way, so as to ensure a consistency of the glass fiber net tape CTC and reduce distortion of the glass fiber net tape owing to bending of the CTC, when the winding is formed.

With reference to Fig. 3, it is an analysis view schematically showing the force when the glass fiber net tape is wound, wherein Fig. 3A is an analysis view schematically showing the force when it is wound straight and Fig. 3B is an analysis view schematically showing the force when it is wound obliquely. Seen from the simple force analysis, the net tape, when it is wound straightly, is forced only in warp direction and supposed to be Al, there is no force in weft direction. If it is wound obliquely the warp force is A4 and weft force is A3, which bear Al together.

Therefore, we can conclude that oblique winding enables uniform force and is superior to straight winding.

The new type of CTC is mainly used in large-scale transformers having a power of greater than 220kVA so as to enhance heat exchange between the CTC and transformer oil, reduce the size of winding, and improve use efficiency of CTC

material.

According to the wrapping glass fiber net tape of the present invention, contact of the CTC enameled conductor with transformer oil can be in the greatest extent so as to maximize heat exchange.

A conventional CTC is wrapped by an insulation paper, which influences heat exchange and increases size of windings of the transformer. The structural improvement of the present invention enables reduction of sizes of the winding and the whole transformer and cost economy.

The glass fiber net tape used in the present invention, compared with the currently used polyester mesh tape, satisfies the existing characteristic and further overcomes innate defects of the polyester material. The glass fiber net tape is chemically stable and unreactive, mechanically stable and remains unchanged for a long time, fracture resistant, and has a good binding performance.

The glass fiber net tape in the present invention is wound obliquely, so that winding speed is increased and extensively automatic production is improved. Also, oblique winding, compared with straight winding, has a good damage resistance due to incontinuity. Thus, a transformer winding as small as possible is formed according to the customers'requirement.

The glass fiber net tape can be dipped with self-adhesive epoxy resin, which on the one hand improves mechanical performance and on the other hand further enhances mechanical intensity of the transformer winding, because the net tape is bonded to the CTC conductor after the transformer winding is heated.

In order to prevent foreign matter from damaging the glass fiber net tape CTC, another insulation paper can be additionally wrapped. Continuous threads are added between the glass fiber net tape and the insulation paper. When forming a transformer winding, the continuous thread is dragged to cut off the insulation paper in the outermost layer so as to make it take off automatically. The insulation paper not only has a protection function but also has no influence to the use of the glass fiber net tape CTC.

The glass fiber net tape CTC is manufactured as follows: Preparing enameled wires; transposing said enameled wires together to form CTC; and winding obliquely the glass fiber net tape on the periphery of the CTC ; wrapping insulation paper and threads on the outer layer of the glass fiber net tape CTC; winding tightly the glass fiber net tape CTC on a shaft.

The method for using the glass fiber net tape CTC are as follows: releasing

gradually the glass fiber net tape CTC wound around a shaft; bending the cable and removing the insulation paper and threads on the outer layer of the glass fiber net tape CTC; helically winding to form windings; heating to integrate the glass fiber net tape with the CTC.

The present invention is described according to some preferable embodiments above. However, the present invention is not limited to the embodiments. Those skilled in the art can make various alterations and changes according to the spirit of the invention. The present invention includes various equivalent embodiments.