CN-121983412-A - Low-capacity high-voltage double-winding power transformer and winding design method

CN121983412ACN 121983412 ACN121983412 ACN 121983412ACN-121983412-A

Abstract

The invention relates to a low-capacity high-voltage double-winding power transformer and a winding design method, wherein a medium-voltage winding, a high-voltage winding and a voltage regulating winding are sequentially arranged on the outer side of an iron core center column, the medium-voltage winding adopts a pattern-inserted and intertwined winding structure, a plurality of angle surrounding group sections are arranged at the upper end of the medium-voltage winding, a first winding angle ring is arranged on the upper side of the inner end of a first angle surrounding group section, the outer end of the first angle surrounding group section is connected with a medium-voltage winding head and is provided with a U-shaped paper groove, winding angle rings are arranged between turns with the largest potential difference between two adjacent angle surrounding group sections in the other angle surrounding group sections, electrostatic ring and angle ring assemblies are arranged at the upper ends of the medium-voltage winding and the high-voltage winding, the voltage regulating winding head is arranged in an outlet wire forming sleeve, an outlet wire protection angle ring is arranged between a bending part of the outlet wire forming sleeve and an iron core upper yoke, and the surface of the iron core column is wrapped with a ground screen. The invention can meet the requirements of small capacity and high voltage, and can also ensure the reliable performance of the double-winding transformer and meet the special requirements of users.

Inventors

LIU JIANSONG
XU CHUNMIAO
TANG TAO
LIN YANG
WANG GANG

Assignees

特变电工沈阳变压器集团有限公司

Dates

Publication Date: 20260505
Application Date: 20260306

Claims (10)

1. The low-capacity high-voltage double-winding power transformer is characterized by comprising an iron core, wherein a medium-voltage winding (3), a high-voltage winding (4) and a voltage regulating winding (5) are sequentially arranged outside an iron core column (1) of the iron core from inside to outside; the medium voltage winding (3) adopts a flower-arrangement entangled winding structure, the upper end of the medium voltage winding is provided with a plurality of angle surrounding group sections, the upper side of the inner end of the uppermost first angle surrounding winding section (301) is provided with a first winding angle ring (3011), the outer end of the first angle surrounding winding section is connected with a medium voltage winding head (6) and is provided with a U-shaped paper groove (3012), winding angle rings are arranged between turns with the largest potential difference of two adjacent angle surrounding group sections in the rest angle surrounding winding sections, the upper end of the medium voltage winding (3) is provided with a medium voltage electrostatic ring (14), the upper side of the medium voltage electrostatic ring (14) is provided with a medium voltage angle ring component, the upper end of the high voltage winding (4) is provided with a high voltage electrostatic ring (15), the upper end of the high voltage regulating winding (5) is provided with a voltage regulating angle ring component, the medium voltage winding head (6) is arranged in an outgoing line forming sleeve (29), the outgoing line forming sleeve (29) forms an outgoing line horizontal part towards the outer part, the outgoing line horizontal part is bent towards the outgoing line horizontal part, the insulating angle ring component is arranged between the high voltage ring component and the high voltage ring component (28), an outgoing line protection angle ring (30) is arranged between the bending part of the outgoing line forming sleeve (29) and the iron core upper yoke (7) of the iron core, and the surface of the iron core column (1) is wrapped with a ground screen.
2. The low-capacity high-voltage double-winding power transformer according to claim 1, wherein the second angular surrounding group section (302) of the medium-voltage winding (3) is separated from the inner end of the third angular surrounding group section (303) by a second winding angular ring (3021), the outer end of the third angular surrounding group section (303) is separated from the outer end of the fourth angular surrounding group section (304) by a third winding angular ring (3031), and the inner end of the fourth angular surrounding group section (304) is separated from the inner end of the fifth angular surrounding group section (305) by a fourth winding angular ring (3041).
3. The low-capacity high-voltage double-winding power transformer according to claim 2, wherein the first winding corner ring (3011), the second winding corner ring (3021) and the fourth winding corner ring (3041) are formed corner rings, the formed corner rings are buckled on the corresponding corner surrounding group section ends, the third winding corner ring (3031) is a corrugated paper corner ring (9), and insulating crepe paper (12) is wrapped outside the corrugated paper corner ring (9).
4. The low capacity high voltage double winding power transformer according to claim 1, wherein the medium voltage corner ring assembly on the upper side of the medium voltage electrostatic ring (14) comprises a medium voltage inner corner ring and a medium voltage outer corner ring which are staggered, the high voltage corner ring assembly on the upper side of the high voltage electrostatic ring (15) comprises a high voltage inner corner ring and a high voltage outer corner ring which are staggered, and the medium voltage corner ring assembly height is larger than the high voltage corner ring assembly height.
5. The low-capacity high-voltage double-winding power transformer of claim 4, wherein medium-voltage inner corner ring fillet radii arranged from bottom to top in the medium-voltage corner ring assembly are sequentially reduced, and medium-voltage outer corner ring fillet radii arranged from bottom to top are sequentially reduced.
6. The low-capacity high-voltage double-winding power transformer according to claim 4, wherein a first corner ring protection cylinder (10) is integrally arranged on a first middle-voltage outer corner ring (16) positioned at a bottom layer of the middle-voltage corner ring assembly, a second corner ring protection cylinder (11) is integrally arranged on a first middle-voltage inner corner ring (18) positioned at the bottom layer, and the first corner ring protection cylinder (10) and the second corner ring protection cylinder (10) are in butt joint to form a closed space for accommodating the middle-voltage winding head (6).
7. The low-capacity high-voltage double-winding power transformer according to claim 1, wherein the voltage regulating corner ring assembly comprises a voltage regulating inner corner ring and a voltage regulating outer corner ring which are staggered and overlapped at the upper end of the voltage regulating winding (5) from bottom to top.
8. A method for designing a winding of a low-capacity high-voltage double-winding power transformer according to claim 1, comprising the steps of: Step one, determining that both the high-voltage winding (4) and the medium-voltage winding (3) adopt a tangled winding structure, and determining the maximum potential gradient U max of a lightning impulse voltage test acting on the high-voltage winding (4) or the medium-voltage winding (3) according to the following formula (4): (4); In the formula (4), U 0 is the input voltage; c is the capacitance of the winding to the ground, K is the capacitance of the winding in series, l is the total length of the winding; step two, because the winding capacitance to ground C can not be changed due to the limitation of the transformer structure, the winding series capacitance K is increased to reduce the potential gradient between winding segments, and is determined according to the following formula (5): (5); in the formula (5), C z is the winding turn-to-turn capacitance; Epsilon is the dielectric constant of oil paper insulation, A is the contact area of two turns of wires, d is the insulation thickness of the turns of the wires, N is the total number of turns of the winding, and C b is the inter-cake capacitance of the winding; Step three, determining a winding series capacitance K according to the step two, then determining a potential gradient U max, according to the step one, and then further determining specific structures of the high-voltage winding (4) and the medium-voltage winding (3) according to the potential gradient U max ; And step four, further designing a winding insulation structure aiming at the medium-voltage winding (3) structure determined in the step three.
9. The method of claim 8, wherein in the second step, the inter-winding pancake capacitor C b comprises a wire turn insulation capacitor C b1 , a pad capacitor C b2 and an oil gap capacitor C b3 , wherein: the turn insulation capacitance C b1 is calculated according to the following equation (6): (6); In the above formula (6), epsilon 1 is the turn insulation dielectric constant, d 1 is the thickness of the turn insulation after compression, R is the outer diameter of the winding, and R is the inner diameter of the winding. The pad capacitance C b2 is calculated according to the following equation (7): (7); In the above formula (7), epsilon 2 is the dielectric constant of the paperboard of the cushion block, d 2 is the thickness of the compressed cushion block, q is the number of the cushion blocks, and b is the width of a single cushion block. The oil gap capacitance C b3 is calculated according to the following equation (8): (8); in the formula (8), epsilon 3 is the dielectric constant of transformer oil; Finally, calculating the inter-winding cake capacitance C b according to the following formula (9): (9)。
10. The method for designing a small-capacity high-voltage double-winding power transformer winding according to claim 9, wherein in the third step, it is determined that the high-voltage winding (4) still adopts a conventional entangled winding structure according to a potential gradient U max calculated by the high-voltage winding (4), it is determined that the medium-voltage winding (3) adopts an inserted-flower entangled winding structure according to a potential gradient U max calculated by the medium-voltage winding (3), and a winding series capacitance of the inserted-flower entangled winding structure is calculated according to the following formula (10): (10); In the fourth step, each corner surrounding group section and each winding corner ring are designed aiming at the flower arrangement and knot-shape winding structure of the medium-voltage winding (3).

Description

Low-capacity high-voltage double-winding power transformer and winding design method Technical Field The invention relates to the field of power transformers, in particular to a low-capacity high-voltage double-winding power transformer and a winding design method. Background The high-voltage power transformers in the prior art are large-capacity autotransformers for supplying power to a power grid, such as 334MVA/500kV single-phase autotransformers in China and 500MVA/400kV three-phase autotransformers in foreign countries. The high-capacity autotransformer is a three-winding transformer no matter in which the high-capacity autotransformer and the medium-capacity autotransformer are three windings, wherein the voltages of the high-voltage winding and the medium-voltage winding are 500 (or 400) kV and 220kV respectively, the high-voltage winding and the medium-voltage winding form autotransformer, the low-voltage winding is an independent angle joint winding (at most 33 or 10 kV voltage levels), and the winding arrangement is iron core-low voltage-medium voltage-high voltage in sequence. In some special scenarios, however, a power transformer user may need some special transformers, such as in a port project abroad, the user needs a power transformer with a capacity of only 50MVA, the high-voltage side of which is connected to a 400kV power grid, the low-voltage side of which supplies power to a 220kV transformer in the port (i.e., the transformation ratio is 400/220 kV), and the transformer has only two windings. Compared with the conventional high-capacity high-voltage transformer, the low-capacity high-voltage transformer has some special requirements: 1. The conventional high-capacity high-voltage transformer has high electric field distribution due to large capacity and large volume. The small-capacity high-voltage transformer has small volume, so that the electric field distribution is concentrated, and the insulation design needs to be particularly enhanced. 2. The conventional high-capacity high-voltage transformer has the low-voltage winding, and the low-voltage winding is close to the iron core at the innermost diameter side, so that the potential difference between the medium-voltage winding and the low-voltage winding is relatively smaller (220 kV-33 kV), and the electrode shape of the low-voltage winding is better, so that the insulation distance between the medium-voltage winding and the iron core is increased. The low-voltage winding is omitted, the original 220kV medium-voltage winding is arranged at the innermost diameter side near the iron core instead of the low-voltage winding, namely, the three windings are changed into a double-winding structure, the potential difference between the medium-voltage winding and the iron core is larger, namely, the 220kV winding directly corresponds to the 0 potential of the iron core, sharp angles are actually formed on the surface of the iron core in the grading manner, the electrode shape is far worse than that of the low-voltage winding, and therefore, after the low-voltage winding is omitted, the insulation design of other windings is also particularly enhanced. 3. The low-voltage winding exists in the conventional high-capacity high-voltage transformer, the middle-voltage winding head is far away from the core limb of the iron core, and meanwhile, the middle-voltage winding head is far away from the yoke and the clamping piece on the iron core after extending out of the pressing plate. The small-capacity high-voltage transformer is influenced by factors such as small capacity of the medium-voltage winding, small radial width of the medium-voltage winding, very close distance between the medium-voltage winding and the core limb, very close distance between the medium-voltage winding and the core upper yoke and the clamping piece, and the like, so that the insulation problem of the upper part of the medium-voltage winding of 220kV also needs to be paid attention to. Disclosure of Invention The invention aims to provide a low-capacity high-voltage double-winding power transformer and a winding design method, which can meet the requirements of low capacity (such as 50 MVA) and high voltage (such as 400 kV) and simultaneously ensure the reliable performance of the double-winding power transformer so as to meet the special requirements of users. The aim of the invention is realized by the following technical scheme: A low-capacity high-voltage double-winding power transformer comprises an iron core, wherein a middle-voltage winding, a high-voltage winding and a voltage regulating winding are sequentially arranged on the outer side of an iron core column of the iron core from inside to outside, the middle-voltage winding adopts a pattern-inserted and entangled winding structure, a plurality of angle surrounding group sections are arranged at the upper end of the middle-voltage winding, a first winding angle ring is arranged on the upper side of the inner e