Electromagnetic voltage transformer body based on four-section winding structure and winding method thereof

Abstract

The invention provides an electromagnetic voltage transformer body based on a four-section winding structure and a winding method of the electromagnetic voltage transformer body, a cross section circle of an iron core, a secondary winding, a main insulating layer and a primary winding are axially concentric, the iron core, the secondary winding, the main insulating layer and the primary winding are sequentially arranged from inside to outside, the primary winding is divided into four sections of mutually independent series coils in the axial direction, and the four sections of coils are connected in series. The two coils are respectively an S1 coil, an S2 coil, an S3 coil and an S4 coil, the winding directions of the adjacent coils are opposite, a lead on the outermost layer of the S1 coil is connected with an A end of a primary lead, a lead on the outermost layer of the S4 coil is connected with an N end of the primary lead, first insulating PMP paper and an insulating paper board are arranged between the iron core and the secondary winding, first semiconductor crepe paper is arranged between the secondary winding and the main insulating layer, and a second insulating paper board is arranged between the secondary winding and the main insulating layer. And second semiconductor crepe paper is arranged between the main insulating layer and the primary winding. The partial discharge capacity is remarkably reduced and is reduced by 81%-83% compared with that of traditional products of the same type, epoxy resin filling is convenient, the stability of the voltage transformer is improved, and the service life of the voltage transformer is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of voltage transformer technology, and specifically relates to the body of an electromagnetic voltage transformer based on a four-segment winding structure and its winding method. Background Technology

[0002] In the field of power system voltage measurement, the interlayer field strength control of the primary winding of an electromagnetic voltage transformer is a key factor determining the reliability of the equipment. As the voltage level of electromagnetic voltage transformers increases, the traditional winding structure reveals three fundamental defects: Firstly, there is the cumulative effect of electric field strength: In single- and double-segment winding structures, due to the large number of copper wire turns per layer, the volume of the voltage transformer mainly depends on its rated output and other parameters; the larger the parameters, the larger the volume. Since three units are usually installed in a cabinet, the width is limited, so the length needs to be increased accordingly, resulting in a longer iron core. The longer iron core makes the interlayer insulation paper of the primary winding wider, ultimately resulting in a large number of turns per layer in single- or double-segment windings. The interlayer voltage U is equal to the number of turns per layer N1 × the voltage per turn U1, and the interlayer voltage difference ΔU is proportional to the total number of turns N (ΔU=Ur×Δn / N, where Ur is the applied voltage, Δn is the number of copper wire turns per layer, and N is the total number of copper wire turns). This results in a potential difference between the innermost and outermost layers that can be as high as 0.8Ur; for example, the interlayer potential difference of a 35kV voltage transformer can be as high as 28kV.

[0003] Second, the risk of insulation failure: ① Excessive interlayer electric field strength. The formula for calculating the interlayer electric field strength E is: E=(2×U1×N1) / D, where: U1=voltage per turn of copper wire (V), N1=number of turns per layer of copper wire, and D=total thickness of the insulating paper between the two layers of copper wire (mm). In traditional single-segment or double-segment winding structures: the width of the interlayer insulating paper is relatively large, which leads to a significant increase in the number of turns N1 per layer of copper wire. According to the above formula, the increase of N1 directly leads to an increase in the interlayer electric field strength E. When the local peak value of the interlayer electric field strength exceeds the tolerance limit of the insulating material (7-18kV / mm), it may induce irreversible degradation of the insulating material, seriously threatening the long-term reliability of the equipment. ② Deterioration of transient response: Distributed capacitance imbalance leads to an increase in the probability of ferroresonance under chopped overvoltage. ③ Exacerbation of temperature rise problem: Under the same parameter conditions, when using a traditional single-segment or double-segment winding structure, the only way to reduce the interlayer voltage and electric field strength is to increase the thickness or number of layers of interlayer PMP paper. This will lead to a significant increase in winding volume (approximately 40%), which in turn worsens heat dissipation conditions, increases thermal resistance, and ultimately causes excessive temperature rise.

[0004] Third, epoxy resin filling is difficult: In single-segment or double-segment winding structures, excessively wide interlayer paper makes it difficult for epoxy resin to completely penetrate into the gaps between each layer of copper wire during the casting process, easily forming unfilled cavities. These cavities will seriously affect the electrical performance of electromagnetic voltage transformers. Summary of the Invention

[0005] The technical problem solved by this invention is to provide an electromagnetic voltage transformer body based on a four-segment winding structure and its winding method. It adopts a unique design that divides the primary winding into four independent coil segments along the axial direction, which solves the problems of large interlayer potential difference, easy insulation failure and difficulty in epoxy resin filling caused by traditional winding structures.

[0006] The technical solution adopted in this invention is: an electromagnetic voltage transformer body based on a four-segment winding structure, including an iron core, a secondary winding, a main insulation layer, and a primary winding. The cross-section of the iron core, the secondary winding, the main insulation layer, and the primary winding are concentric in the axial direction, and are arranged from the inside out as follows: iron core, secondary winding, main insulation layer, and primary winding. The primary winding is divided into four independent series coils along the axial direction, namely coil S1, coil S2, coil S3, and coil S4. The winding directions of adjacent coils are opposite. The outermost lead of coil S1 is connected to the A end of the primary lead, and the outermost lead of coil S4 is connected to the N end of the primary lead. A first insulating PMP paper and an insulating paperboard are provided between the iron core and the secondary winding. A first semiconductor crepe paper is provided between the secondary winding and the main insulation layer, and a second semiconductor crepe paper is provided between the main insulation layer and the primary winding.

[0007] Preferably, the number of turns of the S1 coil, S2 coil, S3 coil, and S4 coil are N respectively. S1 N S2 N S3 and N S4 The total number of turns in the primary winding N = N S1 +N S2 +N S3 +N S4 , and |N S1 -N S4 |≤0.05N, |N S2 -N S3 |≤0.05N.

[0008] Preferably, the primary winding is a single-layer parallel winding structure of multi-strand enameled copper wire, with coils S2 and S3 connected by connecting electrodes, coils S1 and S2 connected by wires, and coils S3 and S4 connected by wires.

[0009] Preferably, the spacing L between adjacent coils in the four independent coil segments meets the following requirements: 10mm≤L≤13mm for 10kV voltage level; 14mm≤L≤17mm for 20kV voltage level; and 18mm≤L≤22mm for 35kV voltage level; and the gaps between the four coil segments are filled with epoxy resin.

[0010] Preferably, the voltage difference ΔU between adjacent coils in the four independent coil segments is ≤0.25Ur.

[0011] Preferably, the winding tension T14 of the S1 coil and the S4 coil is 4N≤T14≤6N, and the winding tension T23 of the S2 coil and the S3 coil is 6N≤T23≤8N.

[0012] Preferably, the axial length of the iron core, secondary winding, main insulation layer and primary winding decreases layer by layer from the inside to the outside, and the end face is stepped.

[0013] A method for winding the body of an electromagnetic voltage transformer based on a four-segment winding structure includes the following steps: Step 1: Wrap the insulating cardboard into a straight cylinder, with the inner diameter of the cylinder being 5-7 mm larger than the diameter of the circumscribed circle of the iron core cross-section; Step 2: Insert the insulating cardboard tube into the iron core column, and wind multiple layers of first insulating PMP paper onto the insulating cardboard. Step 3: Winding the secondary winding; use one layer of first insulating PMP paper between adjacent layers of the same secondary winding, and use three layers of first insulating PMP paper between adjacent layers of different secondary windings. Wind five more layers of first insulating PMP paper on the outermost layer of the completed secondary winding. Step 4: Wrap a full layer of first semiconductor crepe paper on the first insulating PMP paper on the outer layer of the secondary winding in a half-overlap manner; Step 5: Wind the main insulating layer on the first semiconductor crepe paper layer. The main insulating layer is wound with multiple layers of second insulating PMP paper. The total width of the second insulating PMP paper after winding is smaller than the width of the first insulating PMP paper on the outer layer of the secondary winding, with a 5mm blank area on both sides. Step 6: Wrap a layer of second semiconductor crepe paper around the main insulating layer, and then axially spaced S1 coil, S2 coil, S3 coil, and S4 coil are wound sequentially on the second semiconductor crepe paper, with adjacent coils wound in opposite directions. The outermost lead of the S1 coil is used as the primary lead A terminal, and the outermost lead of the S4 coil is used as the primary lead N terminal. The S2 and S3 coils are connected by connecting electrodes. Preferably, the total width of the first semiconductor crepe paper after winding is slightly smaller than the width of the first insulating PMP paper on the outer layer of the secondary winding, with blank areas left on both sides.

[0014] Preferably, the thickness H of the main insulation layer meets the following requirements: 12mm≤H≤15mm for 10kV voltage level, 16mm≤H≤18mm for 20kV voltage level, and 19mm≤H≤25mm for 35kV voltage level.

[0015] The beneficial effects of this invention are: it significantly reduces partial discharge, by 81% to 83% compared to traditional products of the same type; epoxy resin filling is convenient; and it improves the stability and service life of voltage transformers. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the body structure of an electromagnetic voltage transformer based on a four-segment winding structure.

[0017] Figure 2 This is a schematic diagram of the axial cross-sectional structure of the coil of an electromagnetic voltage transformer based on a four-segment winding structure.

[0018] Figure 3 This is a front view of the body of an electromagnetic voltage transformer based on a four-segment winding structure.

[0019] Figure 4 This is a cross-sectional view of the primary coil in a single coil layer.

[0020] Figure 5 This is a schematic diagram of the outermost layer of the secondary winding.

[0021] Reference numerals: 1-S1 coil, 2-S2 coil, 3-S3 coil, 4-S4 coil, 5-Primary lead A end, 6-Primary lead N end, 7-First semiconductor crepe paper, 8-Main insulation layer, 9-Second semiconductor crepe paper, 10-Secondary winding, 11-First insulating PMP paper, 12-Insulating cardboard, 13-Iron core, 14-Secondary lead, 15-Connecting electrode, 16-Second insulating PMP paper, 17-Enameled copper wire, 18-Blank area. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] like Figures 1 to 3As shown, an electromagnetic voltage transformer body based on a four-segment winding structure includes an iron core 13, a secondary winding 10, a main insulation layer 8, and a primary winding. The cross-sectional circle of the iron core 13, the secondary winding 10, the main insulation layer 8, and the primary winding are concentric in axis, and are arranged sequentially from the inside to the outside. The axial length of the iron core 13, the secondary winding 10, the main insulation layer 8, and the primary winding decreases layer by layer from the inside to the outside, and the end face is stepped. The primary winding is divided into four independent series coils along the axis, namely coil 1 (S1), coil 2 (S2), coil 3 (S3), and coil 4 (S4). The winding directions of adjacent coils are opposite. The outermost lead of coil 1 (S1) is connected to the primary lead A end 5, and the outermost lead of coil 4 (S4) is connected to the primary lead N end 6. The two ends of the secondary winding 10 are connected to the secondary lead 14. A first insulating PMP paper 11 and an insulating paperboard 12 are provided between the iron core 13 and the secondary winding 10. A first semiconductor crepe paper 7 is provided between the secondary winding 10 and the main insulation layer 8. A second semiconductor crepe paper 9 is provided between the main insulation layer 8 and the primary winding. The first semiconductor crepe paper 7 is 15mm wide, the second semiconductor crepe paper 9 is 20mm wide, the first insulating PMP paper 11 is 0.1mm thick, and the second insulating PMP paper 16 is 0.2mm thick.

[0024] like Figure 4 As shown, the primary winding is a single-layer parallel winding structure of multi-strand enameled copper wire 17. The diameter of a single copper core ranges from φ0.06mm to φ0.18mm, and the number of parallel strands is at least 5, usually 5 to 7. For example, φ0.11*6 indicates the use of 6 enameled copper wire 17 with a copper core diameter of φ0.11mm wound in parallel. Cross-sectional area calculation: When calculating the cross-sectional area of ​​the primary winding conductor, it is based on the copper core diameter (excluding the enamel) and the number of parallel strands. Taking φ0.11*6 as an example, the total cross-sectional area is 6×(π×(φ0.11 / 2)²). When multi-strand parallel winding, the copper wires must be arranged closely together in sequence, and there should be no stacking. Therefore, multi-strand parallel winding can be understood as a "flat" copper wire. Its actual physical thickness is only the sum of the copper core diameter and the enamel thickness. The thickness of the second insulating PMP paper 16 between layers is 0.2mm, and the winding structure is a single layer of full copper wire and a single layer of second insulating PMP paper 16 alternating.

[0025] S2 coil 2 and S3 coil 3 are connected by connecting electrode 15, S1 coil 1 and S2 coil 2 are connected by a wire (copper sheet), and S3 coil 3 and S4 coil 4 are connected by a wire (copper sheet). The number of turns of S1 coil 1, S2 coil 2, S3 coil 3 and S4 coil 4 are respectively N S1 N S2 N S3 and N S4 The total number of turns in the primary winding N = N S1 +NS2 +N S3 +N S4 , and |N S1 -N S4 |≤0.05N, |N S2 -N S3 |≤0.05N. The spacing L between adjacent coils in the four independent coil segments meets the following requirements: 10mm≤L≤13mm for 10kV voltage level; 14mm≤L≤17mm for 20kV voltage level; 18mm≤L≤22mm for 35kV voltage level. The gaps between the four coil segments are filled with epoxy resin. The voltage difference ΔU between adjacent coils in the four independent coil segments is ≤0.25Ur. The winding tension T14 of coil 1 (S1) and coil 4 (S4) is 4N≤T14≤6N, and the winding tension T23 of coil 2 (S2) and coil 3 (S3) is 6N≤T23≤8N.

[0026] The thickness H of the main insulation layer 8 meets the following requirements: 12mm≤H≤15mm for 10kV voltage level, 16mm≤H≤18mm for 20kV voltage level, and 19mm≤H≤25mm for 35kV voltage level.

[0027] To more intuitively verify the technical effects of this invention, a series of performance tests were conducted. The tested product was a 35kV electromagnetic voltage transformer, and the technical effect test comparisons are as follows: Partial discharge quantity: 45 pC for single-segment winding; 42 pC for double-segment winding; 8 pC for the four-segment winding of this invention. The partial discharge quantity is significantly reduced by approximately 81% to 83%.

[0028] Extinguishing voltage (kV): Measured voltage: 48.6kV, single-segment winding 30kV; double-segment winding 31kV; the four-segment winding of this invention 42kV; an increase of approximately 29%.

[0029] A method for winding the body of an electromagnetic voltage transformer based on a four-segment winding structure includes the following steps: Step 1: Use 0.5mm thick insulating cardboard 12 as a base and wrap it into a straight cylinder. The inner diameter of the cylinder is 5-7mm larger than the outer diameter of the cross-section of the iron core 13.

[0030] Step 2: Insert the insulating cardboard tube into the core post of the iron core 13, and wind multiple layers of first insulating PMP paper 11 on the insulating cardboard 12; Step 3: Wind the secondary winding 10; use one layer of first insulating PMP paper 11 between adjacent layers of the same secondary winding 10, and use three layers of first insulating PMP paper 11 between adjacent layers of different secondary windings 10. Wind five more layers of first insulating PMP paper 11 on the outermost layer of the completed secondary winding 10. Connect the two ends of the secondary winding 10 to the secondary lead wire 14. Step 4: On the outer layer of the secondary winding 10, the first insulating PMP paper 11 is wrapped with a full layer of the first semiconductor crepe paper 7 in a half-overlap manner; as shown Figure 5 As shown, the total width of the first semiconductor crepe paper 7 after winding is slightly smaller than the width of the first insulating PMP paper 11 on the outer layer of the secondary winding 10, with blank areas 18 left on both sides.

[0031] Step 5: Wind the main insulating layer 8 on the first semiconductor crepe paper 7 layer. The main insulating layer 8 is wound in multiple layers using the second insulating PMP paper 16. The total width of the second insulating PMP paper 16 after winding is less than the width of the first insulating PMP paper 7 on the outer layer of the secondary winding 10, with a 5mm blank area on both sides. Step 6: Wrap a layer of second semiconductor crepe paper 9 around the main insulating layer 8, and axially spaced S1 coil 1, S2 coil 2, S3 coil 3 and S4 coil 4 on the second semiconductor crepe paper 9, wherein the winding directions of adjacent coils are opposite. The outermost lead of S1 coil 1 is used as the primary lead A end 5, and the outermost lead of S4 coil 4 is used as the primary lead N end 6. S2 coil 2 and S3 coil 3 are connected by connecting electrode 15.

[0032] The above describes specific embodiments of the present invention and the technical principles employed. Any modifications or equivalent transformations based on the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A transformer body based on a four-segment winding structure of an electromagnetic voltage transformer, characterized in that: The device includes an iron core, a secondary winding, a main insulation layer, and a primary winding. The cross-section of the iron core, the secondary winding, the main insulation layer, and the primary winding are concentric in axis, and arranged from the inside out as follows: iron core, secondary winding, main insulation layer, and primary winding. The primary winding is divided into four independent series coils along the axis, namely coil S1, coil S2, coil S3, and coil S4. The winding directions of adjacent coils are opposite. The outermost lead of coil S1 is connected to the A end of the primary lead, and the outermost lead of coil S4 is connected to the N end of the primary lead. A first insulating PMP paper and an insulating paperboard are provided between the iron core and the secondary winding. A first semiconductor crepe paper is provided between the secondary winding and the main insulation layer, and a second semiconductor crepe paper is provided between the main insulation layer and the primary winding.

2. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The number of turns of the S1, S2, S3, and S4 coils are respectively N S1 N S2 N S3 and N S4 The total number of turns in the primary winding N = N S1 +N S2 +N S3 +N S4 , and |N S1 -N S4 |≤0.05N, |N S2 -N S3 |≤0.05N.

3. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The primary winding is a single-layer parallel winding structure of multi-strand enameled copper wire. The S2 coil and the S3 coil are connected by connecting electrodes, the S1 coil and the S2 coil are connected by wires, and the S3 coil and the S4 coil are connected by wires.

4. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The spacing L between adjacent coils in the four independent coil segments meets the following requirements: 10mm≤L≤13mm for 10kV voltage level; 14mm≤L≤17mm for 20kV voltage level; and 18mm≤L≤22mm for 35kV voltage level. The gaps between the four coil segments are filled with epoxy resin.

5. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The voltage difference ΔU between adjacent coils in the four independent coil segments is ≤0.25Ur.

6. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The winding tension T14 of coils S1 and S4 is 4N≤T14≤6N, and the winding tension T23 of coils S2 and S3 is 6N≤T23≤8N.

7. The electromagnetic voltage transformer body based on a four-segment winding structure according to claim 1, characterized in that: The axial length of the iron core, secondary winding, main insulation layer and primary winding decreases layer by layer from the inside to the outside, and the end face is stepped.

8. A method for winding the body of an electromagnetic voltage transformer based on a four-segment winding structure, characterized in that, Includes the following steps: Step 1: Wrap the insulating cardboard into a straight cylinder, with the inner diameter of the cylinder being 5-7 mm larger than the diameter of the circumscribed circle of the iron core cross-section; Step 2: Insert the insulating cardboard tube into the iron core column, and wind multiple layers of first insulating PMP paper onto the insulating cardboard. Step 3: Winding the secondary winding; use one layer of first insulating PMP paper between adjacent layers of the same secondary winding, and use three layers of first insulating PMP paper between adjacent layers of different secondary windings. Wind five more layers of first insulating PMP paper on the outermost layer of the completed secondary winding. Step 4: Wrap a full layer of first semiconductor crepe paper on the first insulating PMP paper on the outer layer of the secondary winding in a half-overlap manner; Step 5: Wind the main insulating layer on the first semiconductor crepe paper layer. The main insulating layer is wound with multiple layers of second insulating PMP paper. The total width of the second insulating PMP paper after winding is smaller than the width of the first insulating PMP paper on the outer layer of the secondary winding, with a 5mm blank area on both sides. Step 6: Wrap a layer of second semiconductor crepe paper around the main insulating layer, and axially spaced S1 coil, S2 coil, S3 coil and S4 coil are wound sequentially on the second semiconductor crepe paper, with adjacent coils having opposite winding directions. The outermost lead of the S1 coil is used as the primary lead A end, and the outermost lead of the S4 coil is used as the primary lead N end. The S2 coil and S3 coil are connected by connecting electrodes.

9. The electromagnetic voltage transformer body based on a four-segment winding structure and its winding method according to claim 8, characterized in that: The total width of the first semiconductor crepe paper after winding in step 4 is slightly smaller than the width of the first insulating PMP paper on the outer layer of the secondary winding, with blank areas left on both sides.

10. The electromagnetic voltage transformer body based on a four-segment winding structure and its winding method according to claim 8, characterized in that: The thickness H of the main insulation layer meets the following requirements: 12mm≤H≤15mm for 10kV voltage level, 16mm≤H≤18mm for 20kV voltage level, and 19mm≤H≤25mm for 35kV voltage level.

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