No-load tap changer insulation shielding structure

Abstract

The utility model belongs to the technical field of transformer manufacturing, and relates to an insulation shielding structure of a no-load tap changer, which comprises an inner side insulation paper tube, a shielding tube and an outer side insulation paper tube, and the inner side insulation paper tube, the shielding tube and the outer side insulation paper tube are sequentially and fixedly arranged on the periphery of the no-load tap changer from inside to outside. Gaps are reserved among the inner-side insulating paper tube, the shielding tube and the outer-side insulating paper tube, smooth arcs are arranged at the upper end and the lower end of the shielding tube, the shielding tube is surrounded by the shielding tube insulator, and the upper end and the lower end of the shielding tube after being wrapped by the shielding tube insulator are still of smooth arc structures. According to the utility model, the insulation shielding structure of the no-load tap changer is optimized, the arrangement of the insulation shielding structure is compact, the insulation distance between the no-load tap changer and the coil is increased under the condition that the overall insulation distance is not increased, the safety margin requirement of a high-voltage and large-capacity transformer can be finally met, and the safe operation of a product is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of transformer manufacturing and relates to an insulation shielding structure of a no-load voltage regulating switch. Background Art

[0002] At present, the scale of power grids and electricity demand are constantly expanding. Many transformer manufacturers are committed to the development of high-voltage, large-capacity power transformers. The reliability of transformer insulation structure is particularly important in the safe operation of high-voltage, large-capacity transformers.

[0003] The off-load voltage regulator used in high-voltage and large-capacity transformers has a small insulation distance from the high-voltage coil. If the safety margin is insufficient, the insulation reliability will be poor and it will not be able to withstand short-term power frequency and impulse withstand voltage tests, which will pose a safety hazard. The shape, layout and thickness of the insulating material all affect the insulation reliability of the off-load voltage regulator. Once there is an insulation shielding defect, it may affect the electric field strength distribution of the off-load voltage regulator, damage the insulation structure, and affect the normal operation of the high-voltage and large-capacity transformer. Utility Model Content

[0004] In order to solve the above-mentioned technical problems, the utility model provides an insulation shielding structure of a no-load voltage regulating switch, aiming to improve the insulation reliability of the transformer without increasing the overall insulation distance and without giving up the economic index. The technical solution adopted by the utility model is:

[0005] An insulating shielding structure for an off-load voltage-regulating switch, the insulating shielding structure comprising an inner insulating paper tube, a shielding tube and an outer insulating paper tube, the outer circumference of the off-load voltage-regulating switch being fixedly installed with the inner insulating paper tube, the shielding tube and the outer insulating paper tube in sequence from the inside to the outside, with gaps left between the inner insulating paper tube, the shielding tube and the outer insulating paper tube, smooth arcs being arranged at the upper and lower ends of the shielding tube, the shielding tube insulation being surrounded at the outer circumference of the shielding tube, and the upper and lower ends of the shielding tube after wrapping the shielding tube insulation are still smooth arc structures.

[0006] Preferably, the upper and lower ends of the inner insulating paper tube are respectively fixedly connected to the body insulation in the oil tank, and the outer periphery of the inner insulating paper tube is respectively provided with upper and lower groups of insulating fixing components of the same structure, and the insulating fixing components include a plurality of first insulating fixing blocks evenly distributed on the outer periphery of the inner insulating paper tube, and through holes corresponding to the positions and sizes are respectively provided on the inner insulating paper tube and the first insulating fixing blocks, and the nuts are tightened at the ends of the bolts after the bolts pass through the two through holes, and the four corners of the first insulating fixing blocks are all chamfered; smooth grooves corresponding to the smooth arc of the shielding tube are respectively provided at the bottom of the upper first insulating fixing block and the top of the lower first insulating fixing block, and the shielding tube is clamped in the upper and lower smooth grooves; an annular groove is provided on the lower nut, and the width of the annular groove matches the thickness of the outer insulating paper tube, the bottom of the outer insulating paper tube is clamped in the annular groove of the lower nut, and the top of the outer insulating paper tube is close to the outer surface of the upper first insulating fixing block.

[0007] Preferably, the shielding tube includes two upper and lower shielding tubes, a second insulating fixing block is arranged between the upper and lower opposite first insulating fixing blocks, the thickness of the second insulating fixing block is less than or equal to the thickness of the first insulating fixing block, and internal threaded holes corresponding to the positions and sizes are respectively opened on the inner insulating paper tube and the second insulating fixing block, the outer side of the internal threaded hole on the second insulating fixing block is a groove step, the screw is screwed into the two internal threaded holes in sequence from the outer side of the second insulating fixing block, the top of the upper shielding tube is clamped in the smooth groove at the bottom of the upper first insulating fixing block, the bottom of the upper shielding tube abuts against the upper surface of the second insulating fixing block, the bottom of the lower shielding tube is clamped in the smooth groove at the top of the lower first insulating fixing block, and the top of the lower shielding tube abuts against the lower surface of the second insulating fixing block.

[0008] Preferably, the thickness of the inner insulating paper tube is 6.5 mm.

[0009] Preferably, the thickness of the shielding tube is 3 mm.

[0010] Preferably, the thickness of the outer insulating paper tube is 6 mm.

[0011] The beneficial effects of the utility model are:

[0012] The utility model optimizes the insulation shielding structure of the no-load voltage regulating switch. The insulation shielding structure is compactly arranged. Without increasing the overall insulation distance, the insulation distance between the no-load voltage regulating switch and the coil is increased, and ultimately the safety margin requirements of high-voltage and large-capacity transformers can be met to ensure the safe operation of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0014] Figure 1 A cross-sectional view of the insulation shielding structure of the no-load voltage regulating switch according to an embodiment of the utility model;

[0015] In the figure: 1 is the inner insulating paper tube, 2 is the first insulating fixing block, 3 is the bolt, 4 is the nut, 5 is the shielding tube, 6 is the shielding tube insulation, 7 is the outer insulating paper tube, 8 is the second insulating fixing block, and 9 is the screw. DETAILED DESCRIPTION

[0016] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present utility model, rather than all of the embodiments.

[0017] like Figure 1 As shown, the insulation shielding structure of the no-load voltage regulating switch includes: an inner insulating paper tube 1, a first insulating fixing block 2, bolts 3, nuts 4, a shielding tube 5, shielding tube insulation 6, an outer insulating paper tube 7, a second insulating fixing block 8 and a screw 9.

[0018] The transformer oil tank is provided with body insulation, and the upper and lower ends of the inner insulating paper tube 1 are respectively fixedly mounted on the body insulation in the oil tank by bolts, and the inner insulating paper tube 1 surrounds the outer periphery of the no-load voltage regulator, and the inner insulating paper tube 1 plays an overall insulating role for the no-load voltage regulator. The thickness of the inner insulating paper tube 1 is preferably 6.5 mm to ensure that the safety requirements of the electric field strength can be met.

[0019] The outer periphery of the inner insulating paper tube 1 is respectively provided with two upper and lower groups of insulating fixing components of the same structure, the insulating fixing components include a plurality of (for example, four or six) first insulating fixing blocks 2 uniformly distributed on the outer periphery of the inner insulating paper tube 1, through holes of corresponding positions and sizes are respectively provided on the inner insulating paper tube 1 and the first insulating fixing blocks 2, the bolt 3 passes through the two through holes from the inside to the outside in sequence, and the nut 4 is tightened at the end of the bolt 3, the first insulating fixing block 2 is fixedly installed on the outer periphery of the inner insulating paper tube 1 by the bolt 3 and the nut 4, and the first insulating fixing block 2 is used to fix and install the shielding tube 5. The four corners of the first insulating fixing block 2 are all rounded.

[0020] A second insulating fixing block 8 is arranged between two upper and lower opposite first insulating fixing blocks 2. The thickness of the second insulating fixing block 8 is less than or equal to the thickness of the first insulating fixing block 2. Internal threaded holes corresponding in position and size are respectively provided on the inner insulating paper tube 1 and the second insulating fixing block 8. The outer side of the internal threaded hole on the second insulating fixing block 8 is a groove step. The screw 9 is screwed into the two internal threaded holes in sequence from the outer side of the second insulating fixing block 8. The second insulating fixing block 8 is fixedly installed on the outer periphery of the inner insulating paper tube 1 by the screw 9. The second insulating fixing block 8 is used to install the shielding tube 5.

[0021] The shielding tube 5 includes two parts, the upper and lower parts, and the shielding tube 5 plays a shielding role. The shielding tube insulation 6 surrounds the outer periphery of the shielding tube 5, and plays an insulating role for the shielding tube 5. The shielding tube 5 is completely wrapped by the shielding tube insulation 6. The shielding tube insulation 6 is an insulating paper, which is wrapped around the outer periphery of the shielding tube 5, and finally the insulating paper is bonded and fixed by bonding. The upper and lower ends of the shielding tube 5 are both provided with smooth arcs. The shape of the shielding tube insulation 6 after surrounding the outer periphery of the shielding tube 5 is as similar as possible to the shape of the original shielding tube 5 to ensure a smooth transition of the ends. The thickness of the shielding tube 5 is preferably 3 mm to ensure that the safety requirements of the electric field strength can be met. The shielding tube 5 is divided into two sections, the upper and lower sections, which is convenient for manufacturing and installation.

[0022] Smooth grooves corresponding to the smooth arc of the shielding tube 5 are respectively provided at the bottom of the upper first insulating fixed block 2 and the top of the lower first insulating fixed block 2. The top of the upper shielding tube 5 is clamped in the smooth groove at the bottom of the upper first insulating fixed block 2. The bottom of the upper shielding tube 5 abuts against the upper surface of the second insulating fixed block 8. The upper shielding tube 5 is installed and fixed by the upper first insulating fixed block 2 and the second insulating fixed block 8. The bottom of the lower shielding tube 5 is clamped in the smooth groove at the top of the lower first insulating fixed block 2. The top of the lower shielding tube 5 abuts against the lower surface of the second insulating fixed block 8. The lower shielding tube 5 is installed and fixed by the lower first insulating fixed block 2 and the second insulating fixed block 8.

[0023] An outer insulating paper tube 7 is sleeved on the outer periphery of the upper and lower insulating fixing components. In order to install the outer insulating paper tube 7, an annular groove is provided on the lower nut 4. The width of the annular groove matches the thickness of the outer insulating paper tube 7. The bottom of the outer insulating paper tube 7 is clamped in the annular groove of the lower nut 4, and the top of the outer insulating paper tube 7 is close to the outer surface of the upper first insulating fixing block 2. The outer insulating paper tube 7 further plays an overall insulating role for the no-load voltage regulating switch. The thickness of the outer insulating paper tube 7 is preferably 6 mm to ensure that the safety requirements of the electric field strength can be met.

[0024] There is a certain gap between the inner insulating paper tube 1, the shielding tube 5 (with the shielding tube insulation 6 wrapped on the outside) and the outer insulating paper tube 7. The no-load voltage regulating switch is placed in the oil tank of a high-voltage, large-capacity transformer, and the space between the inner insulating paper tube 1, the shielding tube 5 and the outer insulating paper tube 7 will be filled with transformer oil.

[0025] The above-mentioned no-load voltage regulating switch insulation shielding structure is compactly arranged, which increases the insulation distance between the no-load voltage regulating switch and the coil, and has a good insulation effect on the safe operation of high-voltage and large-capacity transformers.

[0026] The insulation shielding structure of the no-load voltage regulating switch provided by the utility model is verified by simulation, and the rationality of its structure and the effectiveness of insulation are proved. The simulation verification steps are as follows:

[0027] Step 1: Establish a software simulation model of the no-load voltage regulating switch through the drawings of the no-load voltage regulating switch product, and process the simulation model, such as: crop the simulation model before importing it into the software, retain only the right half (or left half), remove pattern filling, unnecessary bolts and nuts, etc., and import the processed simulation model into the electric field dedicated calculation software MainInsulation;

[0028] Step 2. In the MainInsulation software, select the type of material to be used, such as cardboard, paper, or oil;

[0029] Step 3. According to the conditions selected in step 2, set the insulation area type in the MainInsulation software, such as cardboard, paper, and oil, set the boundary conditions, the boundary conditions are grounding or potential value, select the analysis type, such as short-time power frequency withstand voltage calculation, and apply the finite element method for simulation analysis;

[0030] Step 4: Post-process the calculated field intensity distribution to obtain various characteristic parameters of the electric field, such as the maximum field intensity value, the allowable field intensity value, etc. These parameters can be obtained from the software; draw the corresponding potential, field intensity cloud map and safety margin distribution map as needed;

[0031] Step 5: According to the verification results obtained in step 4, the electric field strength of the no-load voltage regulating switch model is analyzed to obtain the local starting field strength allowable value E of the no-load voltage regulating switch. CP , E CP =A·d -0.37, unit is kV / mm, A is a coefficient related to the gas content of transformer oil, oil gap position, etc., d is the length of the oil gap along the power line direction, unit is mm. For the withstand voltage test of 50HZ power frequency and 1min, the value of A is selected as follows: (1) between degassed oil and paperboard, A=21.4; (2) between gas-saturated oil and paperboard, A=18.5; (3) between degassed oil and insulated electrode accessories, A=18.0; (4) between degassed oil and oil-paper interface, A=15; (5) near degassed oil and bare electrode, A=14.5.

[0032] For different withstand voltage tests, due to the different application time of the test voltage, corrections should be made according to the following situations: (1) For the full-wave impulse test, the value of A is 2.3 times of the above situation; (2) For the operating wave impulse test, the value of A is 1.8 times of the above situation. Then the average electric field strength E on the no-load voltage regulator is obtained: AB , The unit is kV / mm, U AB is the voltage between power lines A and B, in kV, d is the distance between power lines A and B, in mm, and the electric field safety margin value S at each location is the ratio of the allowable electric field strength to the average electric field strength, that is, The key to transformer insulation reliability lies in the safety margin S ≥ 1.0, and the test pass rate is 100%. Therefore, it is necessary to ensure that the safety margin of each part of the insulation structure is greater than 1.

[0033] Step 6. From the simulation verification analysis results, it can be seen that the electric field at the upper end of the shielding tube 5 of the no-load voltage regulating switch is relatively concentrated (the maximum field strength is 7.758 kV / mm). In order to improve the electric field distribution, the shape of the shielding tube insulation 6 of the utility model after wrapping is as close as possible to the original shape of the shielding tube 5, and the end is smoothly transitioned as needed. The four corners of the first insulating fixed block 2 are rounded to avoid corners; the outer insulating paper tube 7 separates the large oil gap and improves the electric field distribution. Through the above comprehensive improvement measures, the allowable electric field strength in the oil is increased and the safety margin S is improved.

[0034] The voltages of various operating conditions are applied to the no-load voltage regulating switch with an added insulation shielding structure to monitor whether there is discharge. If discharge occurs, the insulation shielding structure is optimized and strengthened, such as increasing the thickness of the insulation material and adjusting the insulation distance.

[0035] The insulation shielding structure of the no-load voltage regulating switch provided in the embodiment of the utility model can be applied to a 500kV transformer.

[0036] In the embodiments of the utility model, the technical features not described in detail are all existing technologies or conventional technical means and will not be described in detail here.

[0037] Finally, it should be noted that the above embodiments are only specific implementation methods of the present utility model, which are used to illustrate the technical solution of the present utility model, rather than to limit it, and the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any technician familiar with the technical field can modify the technical solution recorded in the above embodiments within the technical scope disclosed by the present utility model, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiment of the present utility model, and should be covered within the protection scope of the present utility model.

Claims

1. The insulation shielding structure of the no-load voltage regulating switch is characterized by: The insulating shielding structure includes an inner insulating paper tube, a shielding tube and an outer insulating paper tube. The inner insulating paper tube, the shielding tube and the outer insulating paper tube are fixedly installed on the outer periphery of the no-load voltage regulating switch in sequence from the inside to the outside. A gap is left between the inner insulating paper tube, the shielding tube and the outer insulating paper tube. Smooth arcs are arranged on the upper and lower ends of the shielding tube. The shielding tube insulation surrounds the outer periphery of the shielding tube. After the shielding tube insulation is wrapped, the upper and lower ends of the shielding tube are still smooth arc structures.

2. The insulation shielding structure of the no-load voltage regulating switch according to claim 1 is characterized in that: The upper and lower ends of the inner insulating paper tube are respectively fixedly connected to the body insulation in the oil tank, and the outer periphery of the inner insulating paper tube is respectively provided with upper and lower groups of insulating fixing components of the same structure, and the insulating fixing components include a plurality of first insulating fixing blocks uniformly distributed on the outer periphery of the inner insulating paper tube, and through holes corresponding to positions and sizes are respectively provided on the inner insulating paper tube and the first insulating fixing blocks, and nuts are tightened at the ends of the bolts after the bolts pass through the two through holes, and the four corners of the first insulating fixing blocks are all chamfered; smooth grooves corresponding to the smooth arc of the shielding tube are respectively provided at the bottom of the upper first insulating fixing block and the top of the lower first insulating fixing block, and the shielding tube is clamped in the upper and lower smooth grooves; an annular groove is provided on the lower nut, and the width of the annular groove matches the thickness of the outer insulating paper tube, the bottom of the outer insulating paper tube is clamped in the annular groove of the lower nut, and the top of the outer insulating paper tube is close to the outer surface of the upper first insulating fixing block.

3. The insulation shielding structure of the no-load voltage regulating switch according to claim 2 is characterized in that: The shielding tube includes two upper and lower shielding tubes, a second insulating fixing block is arranged between the upper and lower opposite first insulating fixing blocks, the thickness of the second insulating fixing block is less than or equal to the thickness of the first insulating fixing block, the inner insulating paper tube and the second insulating fixing block are respectively provided with internal threaded holes corresponding in position and size, the outer side of the internal threaded hole on the second insulating fixing block is a groove step, the screw is screwed into the two internal threaded holes in sequence from the outer side of the second insulating fixing block, the top of the upper shielding tube is clamped in the smooth groove at the bottom of the upper first insulating fixing block, the bottom of the upper shielding tube abuts against the upper surface of the second insulating fixing block, the bottom of the lower shielding tube is clamped in the smooth groove at the top of the lower first insulating fixing block, and the top of the lower shielding tube abuts against the lower surface of the second insulating fixing block.

4. The insulation shielding structure of the no-load voltage regulating switch according to any one of claims 1 to 3, characterized in that: The thickness of the inner insulating paper tube is 6.5 mm.

5. The insulation shielding structure of the no-load voltage regulating switch according to any one of claims 1 to 3, characterized in that: The thickness of the shielding tube is 3 mm.

6. The insulation shielding structure of the no-load voltage regulating switch according to any one of claims 1 to 3, characterized in that: The thickness of the outer insulating paper tube is 6 mm.

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