JPS60200509A - Transformer for dc power transmission - Google Patents

Abstract

PURPOSE:To improve the DC dielectric strength while reducing the electric field of DC windings by a method wherein the coated insulating papers of outermost layer strand and inermost layer strand of unit disc windings adjacently arranged on a clamp ring are eliminated. CONSTITUTION:A DC winding 2 is composed of unit disc windings 9 laminated in the axial direction. A clamp ring 12 is arranged at the end of DC windings 2. The outermost layer strand 18 and the innermost layer strand 19 of unit disc winding 17 adjacent to the clamp ring 12 are respectively composed of bare conductor without coating paper while the intermediate strands between the strands 18 and 19 are respectively composed of a conductor 20 and a coated insulating paper 20. The electric field is lower in an oil layer 4 with rough equipotential line gap while it is higher in insulating papers 5, 11 with close equipotential line gap. However the DC dielectric strength may be improved since the electric field is not higher on the surface of bare conductor strand 18 without coated insulating paper reducing the electric field on the strand surface of DC winding 2.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a transformer, such as an AC/DC conversion transformer for DC power transmission, to which a voltage waveform including a DC component is applied during operation, and in particular, to a transformer that has good DC dielectric strength. Concerning transformer windings.

[Background of the invention]

High DC voltage is applied to the DC windings of AC/DC conversion transformers in DC power transmission during operation and during insulation specification verification tests at the time of product completion.

FIG. 1 shows a conventional example of the internal winding structure of a transformer having a primary winding, a secondary winding, and a tertiary winding.

-Next winding 1. Secondary winding 2. A tertiary winding 3 is arranged in a coaxial cylindrical shape around the outer circumference of the iron core 4, and transformer oil 4. The structure between the end of the winding and the core 4 is shown in a winding in which a plurality of oil-impregnated paper barriers 5 are arranged alternately. - The secondary winding 1 and the tertiary winding 3 are AC windings, and the secondary winding 2 is DC winding. In other words, high DC voltage is applied to the 1st winding 2 during operation of the transformer or during tests to confirm insulation performance at the time of product completion. Unit disk windings 9 are constructed by winding a wire conductor 8 coated with a plurality of turns in a disk shape, and are stacked in the axial direction of the disks. At the lower end of the winding 2, a clamp ring 12 is disposed adjacent to the disc winding, and is constructed by covering the surface of a conductor 10, which has an external cross section with a large radius of curvature, with oil-impregnated paper 11. AC windings 1 and 3 as well as winding 2
Assume that it has a structure similar to .

Oil-impregnated paper barrier 5.13 located adjacent to the DC winding 2
, 14 are bent at a right angle near the end of the clamp ring 12 to form an L-shaped barrier, as shown. Further, the oil-impregnated paper barriers 15 and 16 constitute cylindrical barriers as shown in the figure.

The DC potential distribution when a DC high voltage is applied to the DC winding 2 becomes a current field dominated by the resistivity of the constituent insulators. Since the resistivity of the insulating paper is more than one order of magnitude higher than the resistivity of the transformer oil, the internal electric field of the insulating layer is more than one order of magnitude larger than the electric field inside the oil layer. In the embodiment of FIG. 1, the conductor lO
9 strand conductor 6 potential 100%, iron core 4. AC winding 1, 3
FIG. 2 shows the distribution of the dotted line (■) among the potential distributions with the potential of 0%. The figure shows a distribution displayed at an interval of 1.3% between equipotential lines. The electric field is low in the oil layer 4 where the equipotential lines are closely spaced, and the electric field is high in the insulating paper 5°7.11 where the equipotential lines are closely spaced.

The part that generates the highest electric field is the covering insulating paper 7, which has the disadvantage of being a weak point in direct current insulation.

[Purpose of the invention]

An object of the present invention is to provide an AC/DC conversion transformer having high DC dielectric strength by reducing the electric field of the DC winding.

[Summary of the invention]

The gist of the present invention is that the covering insulating paper is eliminated in order to eliminate the high electric field inside the covering insulating paper of the outermost M strands and the innermost layer strands of the unit disk winding arranged adjacent to the clamp ring. .

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

In the figure, the DC winding 2 is constructed by stacking unit disk windings 9 in the axial direction. A clamp ring 12 is arranged at the end of the DC winding 2 .

Outermost layer strand 18 of unit disk winding 17 adjacent to clamp ring 12. Each of the innermost layer strands 19 is composed of a bare conductor without a covering paper. The strands in the middle of the strands 18 and 19 each consist of a conductor 21 and an insulating paper 20 .

In the figure, conductor 10. The potential of the bare wire conductor 6 is 100%,
Iron core 4. FIG. 4 shows the part of the broken line frame ■ of the potential distribution with the potential of AC winding 3 set to 0%. The figure shows a distribution displayed at an interval of 1.3% between equipotential lines. The electric field is low in the oil layer 4 where the equipotential lines are closely spaced, and the electric field is high in the insulating papers 5 and 11 where the equipotential lines are closely spaced.

This is because there is no covering insulating paper on the surface of the bare conductor wire 18.

High electric fields no longer occur here.

According to one embodiment of the present invention, the electric field on the surface of the strands of the DC winding 2 is reduced, so that the DC withstand voltage can be improved.

FIG. 5 shows another embodiment of the invention. The difference from FIG. 3 is that in the DC winding 2, the outermost layer 1 [1B, 22.24
and i inner layer strands 19, 23'.

The reason is that each of 25 is made of a bare conductor without covering insulation paper.

This embodiment also has the effect of reducing the surface electric fields of the outermost layer strands and the innermost layer strands of the plurality of stages of unit disk windings around the clamp ring 12.

〔Effect of the invention〕

According to the present invention, since the peripheral portion of the clamp ring has a DC winding that does not generate a high DC electric field, the DC dielectric strength can be increased.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view illustrating a conventional technique, FIG. 2 is a potential distribution diagram illustrating the operation of FIG. 1, and FIG. 3 is a diagram illustrating an embodiment of the present invention. 4 is a potential distribution diagram illustrating the operating principle of the present invention, and FIG. 5 is a sectional view showing another embodiment of the present invention. 4... Oil layer, 5... Oil soaked paper layer, 10... Conductor, 1
1... Covered insulating paper, 12... Clamp ring, 18
...Bare conductor strand 6 Agent Patent attorney Akio Takahashi Figure 5

Claims (1)

[Scope of Claims] (1) A conductor ring having a cross section with a large curvature, which is formed by stacking multiple layers of disk windings in the axial direction, each consisting of a wire conductor coated with insulating paper and wound multiple times in a disk shape; A DC power transmission transformer configured by disposing a clamp ring whose surface is covered with the insulating paper at both ends of the disc winding, wherein the clamp ring on the outermost layer of the disc winding is disposed adjacent to the clamp ring. A transformer for direct current power transmission, characterized in that the strand conductor and the strand conductor in the innermost layer are each composed of a bare conductor strand without the insulating paper, and the intermediate portion of the strand conductor is covered with the insulating paper. . 2. The DC power transmission transformer according to claim 1, wherein a plurality of layers of the disk winding are arranged adjacent to the clamp ring.