Oil-immersed combined transformer for super-high voltage power system
By designing an oil-immersed insulated combined instrument transformer, the insulation and ferroresonance problems of existing combined instrument transformers in ultra-high voltage power systems are solved, achieving stability in insulation reliability and measurement accuracy, and making it suitable for ultra-high voltage power systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TBEA KONCAR (SHENYANG) INSTRUMENT TRANSFORMER CO LTD
- Filing Date
- 2023-08-15
- Publication Date
- 2026-07-14
AI Technical Summary
The existing combined instrument transformer structure cannot meet the application requirements of ultra-high voltage power systems above 500kV, and there are problems such as difficulty in matching the insulation potential distribution of voltage transformers and current transformers and ferroresonance.
The structure adopts an oil-immersed insulated combined instrument transformer, which includes a combination design of current transformer unit and voltage transformer unit. It utilizes integrated lead insulation and a single-core column yokeless iron core structure to ensure insulation reliability. It also converts primary high current and ultra-high voltage into secondary standard current and voltage through electromagnetic induction, avoiding ferroresonance.
It achieves stability in insulation reliability and measurement accuracy in ultra-high voltage power systems, avoids ferroresonance, and ensures safe operation of the product.
Smart Images
Figure CN116994867B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of power equipment, and more particularly to an oil-immersed insulation combined transformer for extra-high voltage power systems. Background Art
[0002] Combined transformers are commonly found in medium and low voltage power systems below 35 kV, and there are also a small number of combined transformers applied in high voltage power systems below 220 kV. The structure of such combined transformers is generally as Figure 9 shown. Its secondary winding of the current transformer is placed in an aluminum shell, and an aluminum tube is welded to the lower part of the aluminum shell to lead out the secondary lead. The outer insulation of the current transformer forms a secondary coil and is set on the current transformer body at the head. The primary and secondary windings of the voltage transformer are sleeved on the core columns of the "mouth" - shaped or "day" - shaped iron core of the voltage transformer to form the body part of the voltage transformer. It forms a combined transformer by assembling the voltage transformer body and the current transformer body in the same body shell. In this structure of the combined transformer, due to the reverse distribution of the insulation potentials of the voltage transformer and the current transformer inside the porcelain bushing after combination, the cooperation is not easy. And due to the structural limitations of the voltage transformer, it cannot meet the requirements of applications in extra-high voltage power systems above 500 kV. Summary of the Invention
[0003] The purpose of the present invention is to provide an oil-immersed insulation combined transformer for extra-high voltage power systems, which can not only ensure the reliability of insulation, avoid ferroresonance of the voltage transformer unit, but also ensure the stability of measurement accuracy, and can be safely applied to extra-high voltage power systems.
[0004] The purpose of the present invention is achieved by the following technical solutions:
[0005] An oil-immersed insulated combined instrument transformer for an ultra-high voltage power system includes an expansion tank, an oil conservator, a porcelain bushing, and a base connected sequentially from top to bottom. The oil conservator houses a current transformer unit, and the porcelain bushing houses a voltage transformer unit. Each voltage transformer unit includes a voltage transformer winding assembly and a voltage transformer core assembly. The oil conservator houses a current transformer aluminum shell, and the secondary winding of the current transformer in the current transformer unit is located within the current transformer aluminum shell. The current transformer aluminum shell is surrounded by annular insulation. The porcelain bushing contains an insulating tube and lead wire insulation, wherein the lead wire insulation is integrally formed with the annular insulation, and the insulating tube is located within the lead wire insulation. The voltage transformer core assembly includes a central strip... The voltage transformer core column has a lead-through hole, and the voltage transformer core column is located in the insulating tube. The current transformer secondary lead of the current transformer secondary winding passes through the lead-through hole. The voltage transformer winding assembly includes a voltage transformer primary winding and a voltage transformer secondary winding. The voltage transformer secondary winding is wound on the voltage transformer core column and located between the voltage transformer core column and the insulating tube. The voltage transformer primary winding is located outside the lead insulation. The voltage transformer primary winding includes multiple winding units connected in series. Multiple capacitor screens are provided inside the lead insulation, and the unit lead connection points of adjacent winding units are equipotentially connected to the corresponding capacitor screens inside the lead insulation.
[0006] The current transformer unit includes a primary winding of a current transformer, and the primary winding of the current transformer passes through the secondary winding of the current transformer.
[0007] The aluminum shell of the current transformer is annular, and the secondary winding of the current transformer, which is composed of an annular iron core, is located in the aluminum shell of the current transformer. The aluminum shell of the current transformer is provided with an annular insulation, and the primary winding of the current transformer passes through the center of the annular insulation.
[0008] The base is provided with a current transformer secondary terminal box and a voltage transformer secondary terminal box. The current transformer secondary lead of the current transformer secondary winding passes through the lead through hole and is led into the current transformer secondary terminal box. The voltage transformer secondary lead of the voltage transformer secondary winding is led into the voltage transformer secondary terminal box.
[0009] The voltage transformer core assembly includes a core support, with the lower end of the voltage transformer core column and the lower end of the insulating tube both located on the core support, which is located on the base.
[0010] The voltage transformer core column is a single-column, yokeless core structure.
[0011] The winding unit includes a unit base and a winding conductor. The unit base has a mounting through hole in the middle for the insulation of the lead wire to pass through. The unit base has a limiting flange at both the upper and lower ends, and the winding conductor is wound between the two limiting flanges. The unit leads formed at both ends of the winding conductor pass through the limiting flanges on the corresponding sides and are connected to the adjacent winding unit.
[0012] The permeability G of the voltage transformer core column is calculated as follows:
[0013]
[0014] In the above formula (1), L is the height of the primary winding of the voltage transformer, M is the height of the voltage transformer core column above the primary winding of the voltage transformer, b is the average distance between each winding unit of the primary winding of the voltage transformer and the core column of the voltage transformer, k1, k2, and k3 are empirical coefficients, and d is the equivalent diameter of the core column of the voltage transformer.
[0015] The excitation current i0 of the voltage transformer unit is calculated as follows:
[0016]
[0017] In equation (2) above, l z B is the equivalent height of the core column of the voltage transformer. m The rated magnetic flux density is given by W1, which is the number of turns in the primary winding of the voltage transformer, and the permeability is given by μ.
[0018] The advantages and positive effects of this invention are as follows:
[0019] 1. This invention utilizes lead insulation integrally formed with the ring insulation of the current transformer unit to serve as the insulation of the voltage transformer unit. The voltage transformer core column of the voltage transformer unit adopts a single-core, yokeless core structure, which is housed within an insulating tube supporting the aluminum shell of the current transformer. This insulating tube is located within the lead insulation. Simultaneously, the secondary leads of the current transformer pass through lead through holes in the middle of the voltage transformer core column. The secondary winding of the voltage transformer is wound on the voltage transformer core column and positioned between the voltage transformer core column and the insulating tube. The primary winding of the voltage transformer is wound on the outside of the lead insulation. This combination of current transformer unit and voltage transformer unit converts the primary high current and ultra-high voltage of the power system into secondary standard current and voltage that can be measured and used for protection. Furthermore, the stability of the core material ensures the stability of the measurement accuracy. Figure 7 As shown, the excitation curve of the voltage transformer unit of the present invention will not intersect with the U-I characteristic curve of the actual capacitor in the power grid that affects the occurrence of ferroresonance, thereby avoiding the occurrence of ferroresonance and ensuring the safe operation of the product.
[0020] 2. The primary winding of the voltage transformer of the present invention includes multiple winding units sequentially mounted on lead insulation from top to bottom, and the lead connection points of adjacent winding units are equipotentially connected to the corresponding capacitor screens within the lead insulation, thus achieving... Figure 8 As shown, the voltage distribution of each winding unit of the primary winding of the voltage transformer is linear at various frequencies, thereby ensuring that the potential of the internal capacitor screen of the product of the present invention is close during operation, thus optimizing the distribution of the internal field strength of the insulation and making the insulation more reliable.
[0021] 3. The overall structure of the present invention is more compact, and it also solves the problem that existing combined instrument transformers cannot meet the application requirements of ultra-high voltage power systems above 500kV due to the structural limitations of voltage transformers. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of the present invention.
[0023] Figure 2 for Figure 1 The front view of the present invention,
[0024] Figure 3 for Figure 1 Enlarged view of point I in the image.
[0025] Figure 4 for Figure 1 A schematic diagram of the voltage transformer core assembly structure.
[0026] Figure 5 for Figure 4 Top view of the voltage transformer core assembly in the middle.
[0027] Figure 6 for Figure 1 Schematic diagram of the winding unit structure of the primary winding of a medium voltage transformer.
[0028] Figure 7 This is a schematic diagram of the excitation characteristic curve and capacitance UI characteristic curve of the voltage transformer unit of the present invention.
[0029] Figure 8 This is a schematic diagram of the voltage distribution characteristic curves of each winding unit of the primary winding of the voltage transformer of the present invention.
[0030] Figure 9 This is a schematic diagram of a combined current transformer structure in the prior art.
[0031] Among them, 1 is the expander, 2 is the oil conservator, 3 is the porcelain bushing, 4 is the secondary terminal box of the current transformer, 5 is the secondary terminal box of the voltage transformer, 6 is the base, 7 is the secondary winding of the current transformer, 8 is the aluminum shell of the current transformer, 9 is the ring insulation, 10 is the primary winding of the current transformer, 11 is the insulating tube, 12 is the lead wire insulation, 13 is the core column of the voltage transformer, 14 is the secondary lead of the current transformer, 15 is the secondary winding of the voltage transformer, 16 is the primary winding of the voltage transformer, 161 is the winding unit, 1611 is the limiting flange, 1612 is the mounting through hole, 162 is the winding conductor, 1621 is the unit lead wire, 17 is the core support, 18 is the capacitor screen, 19 is the core assembly of the voltage transformer, 20 is the lead wire through hole, 21 is the core, 22 is the body of the current transformer, and 23 is the body of the voltage transformer. Detailed Implementation
[0032] The invention will now be described in further detail with reference to the accompanying drawings.
[0033] like Figures 1-8 As shown, the present invention includes an expander 1, an oil tank 2, a porcelain bushing 3, and a base 6 connected sequentially from top to bottom. The oil tank 2 houses a current transformer unit, which includes a secondary winding 7 and a primary winding 10 passing through the secondary winding 7. Both ends of the primary winding 10 are fixed to the oil tank 2. The porcelain bushing 3 houses a voltage transformer unit, which includes a voltage transformer winding assembly and a voltage transformer core assembly 19. Figures 4-5 As shown, the voltage transformer core assembly 19 includes a voltage transformer core column 13 with a lead through hole 20 in the middle, and as... Figures 1-3 As shown, the secondary lead 14 of the current transformer secondary winding 7 passes through the lead through hole 20 and is led to the secondary terminal box 4 of the current transformer on the base 6. The voltage transformer winding assembly includes a primary winding 16 and a secondary winding 15. The secondary winding 15 is wound on the core column 13 of the voltage transformer, and the secondary lead of the secondary winding 15 is led to the secondary terminal box 5 of the voltage transformer on the base 6. The secondary winding 15 is provided with lead insulation 12 on the outside, and the primary winding 16 is located outside the lead insulation 12.
[0034] like Figure 1As shown, the oil tank 2 contains an aluminum shell 8 for a current transformer, and the porcelain bushing 3 contains an insulating tube 11. The aluminum shell 8 for the current transformer is located at the upper end of the insulating tube 11 and is supported by the insulating tube 11. The aluminum shell 8 for the current transformer is annular, with a through hole in its center for the primary winding 10 of the current transformer to pass through. The secondary winding 7 of the current transformer, which is composed of an annular iron core, is located in the aluminum shell 8 for the current transformer. The aluminum shell 8 for the current transformer is surrounded by an annular insulation 9, and the primary winding 10 of the current transformer passes through the center of the annular insulation 9. The lead insulation 12 is integrally formed with the annular insulation 9. Figure 3 As shown, the insulating tube 11 is disposed within the lead insulation 12, the voltage transformer core column 13 is disposed within the insulating tube 11, and the voltage transformer secondary winding 15 is disposed between the voltage transformer core column 13 and the lead insulation 12. Figure 1 and Figures 4-5 As shown, the voltage transformer core assembly 19 includes a core support 17. The lower ends of the voltage transformer core column 13 and the insulation tube 11 are both located on the core support 17, and the lower end of the core support 17 is located on the base 6.
[0035] like Figure 3 As shown, the lead insulation 12 is inserted into a capacitor screen 18 made of semiconductor material during the wrapping process to better utilize the insulation and uniformly insulate the internal electric field.
[0036] like Figure 1 As shown, the primary winding 16 of the voltage transformer includes multiple winding units 161 arranged sequentially from top to bottom outside the lead insulation 12, such as... Figure 6 As shown, the winding unit 161 includes a unit base and a winding conductor 162. The unit base has a mounting through hole 1612 in the middle for the lead insulation 12 to pass through. The unit base has limiting flanges 1611 at both the upper and lower ends, and the winding conductor 162 is wound between the two limiting flanges 1611. The unit leads 1621 formed at both ends of the winding conductor 162 pass through the limiting flanges 1611 on the corresponding sides and are connected in series with the adjacent winding unit 161. In order to ensure that the voltage borne by each winding unit 161 is linearly distributed and has good resistance to impulse voltage, the connection point of the unit leads 1621 of the adjacent winding units 161 is equipotentially connected to the corresponding capacitor screen 18 in the lead insulation 12.
[0037] The current transformer unit and voltage transformer unit combination of the present invention converts the primary high current and ultra-high voltage of the power system into secondary standard current and voltage that can be measured and protected through the principle of electromagnetic induction. Furthermore, the stability of the material of the voltage transformer core column 13 ensures stable measurement accuracy. In addition, the primary winding 16 of the voltage transformer of the present invention is uniformly distributed along the height of the voltage transformer core column 13, and the insulation between it and the voltage transformer core column 13 is capacitive insulation.
[0038] The permeability G of the voltage transformer core column 13 of the voltage transformer unit of the present invention is calculated as follows:
[0039]
[0040] In the above formula (1), L is the height of the primary winding 16 of the voltage transformer, M is the height of the voltage transformer core column 13 above the primary winding 16 of the voltage transformer, b is the average distance between each winding unit 161 of the primary winding 16 of the voltage transformer and the voltage transformer core column 13 of the voltage transformer, k1, k2, and k3 are empirical coefficients, and d is the equivalent diameter of the voltage transformer core column 13.
[0041] The excitation current i0 of the voltage transformer unit of this invention is calculated as follows:
[0042]
[0043] In equation (2) above, l z B is the equivalent height of voltage transformer core column 13. m The rated magnetic flux density is given by the W1 voltage transformer, which has 16 turns in its primary winding and a permeability of μ.
[0044] Based on the above analysis and calculations, as well as sample tests, it can be seen that the aforementioned characteristics ensure that the excitation curve of the voltage transformer unit of this invention will not intersect with the U-I characteristic curve of the actual capacitance in the power grid that affects the occurrence of ferroresonance (e.g., Figure 7 As shown), this avoids ferroresonance and ensures safe product operation. The voltage distribution of each winding unit 161 of the primary winding 16 of the voltage transformer, distributed along the lead insulation, is linear at various frequencies (e.g., ...). Figure 8 As shown in the figure, this ensures that the potential of the capacitor screen inside the lead insulation 12 is close during operation, thereby optimizing the field strength distribution inside the lead insulation 12 and making the insulation more reliable.
[0045] The working principle of this invention is as follows:
[0046] like Figure 9As shown, the existing combined transformer structure places the secondary winding of the current transformer in an aluminum shell, welds an aluminum tube to the bottom of the aluminum shell to lead out the secondary lead, and encases the current transformer insulation to form the secondary coil at the head of the current transformer body 22. The primary and secondary windings of the voltage transformer are mounted on the "U"-shaped or "Sun"-shaped iron core 21 to form the voltage transformer body 23. The voltage transformer body 22 and the current transformer body 23 are assembled in the same shell to form a combined transformer. Because the potential of the voltage transformer and the current transformer insulation are distributed in opposite directions inside the porcelain bushing after the combination, the combined transformer is difficult to match. Furthermore, due to the structural limitations of the voltage transformer, it cannot meet the requirements of ultra-high voltage power system applications above 500kV.
[0047] And such Figures 1-8 As shown, this invention utilizes lead insulation 12, which is integrally formed with the ring insulation 9 of the current transformer unit, to serve as the insulation of the voltage transformer unit. The voltage transformer core column 13 adopts a single-core, yokeless core structure. The voltage transformer core column 13 is housed within an insulating tube 11 supporting the aluminum shell 8 of the current transformer. The insulating tube 11 is located within the lead insulation 12. Simultaneously, the secondary lead 14 of the current transformer unit passes through the lead through-hole 20 in the middle of the voltage transformer core column 13. The secondary winding 15 of the voltage transformer is wound around the voltage transformer core column. The voltage transformer core column 13 is positioned between the voltage transformer core column 13 and the insulating tube 11. The primary winding 16 of the voltage transformer is wound around the outside of the lead insulation 12, and the primary winding 16 includes multiple winding units 161. The connection points of the unit leads 1621 of adjacent winding units 161 are equipotentially connected to the corresponding capacitor screen 18 inside the lead insulation 12. Therefore, the structure of this invention can ensure the reliability of insulation, avoid ferroresonant resonance of the voltage transformer units, and ensure the stability of measurement accuracy. It can be safely applied in ultra-high voltage power systems, such as... Figure 7 As shown, the excitation curve of the voltage transformer unit of this invention will not intersect with the U-I characteristic curve of the actual capacitor in the power grid that affects the occurrence of ferroresonance, thereby avoiding ferroresonance and ensuring the safe operation of the product. Figure 8 As shown, the voltage distribution of each winding unit 161 of the primary winding 16 of the voltage transformer distributed along the lead insulation 12 of the present invention is linear at various frequencies, thereby ensuring that the potential of the internal capacitor screen of the product of the present invention is close during operation, optimizing the distribution of the internal field strength of the insulation and making the insulation more reliable.
Claims
1. An oil-immersed insulated combined instrument transformer for ultra-high voltage power systems, characterized in that: The system includes an expander (1), an oil tank (2), a porcelain bushing (3), and a base (6) connected sequentially from top to bottom. The oil tank (2) contains a current transformer unit, and the porcelain bushing (3) contains a voltage transformer unit. The voltage transformer unit includes a voltage transformer winding assembly and a voltage transformer core assembly (19). The oil tank (2) contains a current transformer aluminum shell (8), and the secondary winding (7) of the current transformer in the current transformer unit is located at... In the current transformer aluminum shell (8), the current transformer aluminum shell (8) is provided with an annular insulation (9) on the outside, and the porcelain bushing (3) is provided with an insulating tube (11) and a lead wire insulation (12), wherein the lead wire insulation (12) is integrally formed with the annular insulation (9), and the insulating tube (11) is located in the lead wire insulation (12). The voltage transformer core assembly (19) includes a voltage transformer core column (13) with a lead wire through hole (20) in the middle, and Furthermore, the voltage transformer core column (13) is disposed in the insulating tube (11), and the current transformer secondary lead (14) of the current transformer secondary winding (7) passes through the lead through hole (20). The voltage transformer winding assembly includes a voltage transformer primary winding (16) and a voltage transformer secondary winding (15), wherein the voltage transformer secondary winding (15) is wound on the voltage transformer core column (13) and disposed in the voltage transformer. Between the core column (13) and the insulating tube (11), the primary winding (16) of the voltage transformer is located outside the lead insulation (12). The primary winding (16) of the voltage transformer includes multiple winding units (161) connected in series. Multiple capacitor screens (18) are provided inside the lead insulation (12), and the unit lead (1621) connection of adjacent winding units (161) is equipotentially connected to the corresponding capacitor screen (18) inside the lead insulation (12). The voltage transformer core column (13) is a single-core column unyoke core structure; The winding unit (161) includes a unit base and a winding conductor (162). The unit base has a mounting through hole (1612) in the middle for the lead insulation (12) to pass through. The unit base has a limiting flange (1611) at both the upper and lower ends. The winding conductor (162) is wound between the two limiting flanges (1611). The unit leads (1621) formed at both ends of the winding conductor (162) pass through the limiting flanges (1611) on the corresponding sides and are connected to the adjacent winding unit (161). The permeability G of the core column (13) of the voltage transformer is calculated as follows: （1）； In the above formula (1), The height of the primary winding (16) of the voltage transformer, The height of the core column (13) of the voltage transformer is higher than that of the primary winding (16) of the voltage transformer. The average distance between each winding unit (161) of the primary winding (16) of the voltage transformer and the core column (13) of the voltage transformer is given. , , This is an empirical coefficient. The equivalent diameter of the core column (13) of the voltage transformer; The excitation current of the voltage transformer unit Calculate as follows: （2）； In the above formula (2), The equivalent height of the voltage transformer core column (13) is given. The rated magnetic flux density, Number of turns in the primary winding (16) of the voltage transformer Let G be the magnetic permeability, which is also obtained from equation (1) above; Based on the above analysis and calculation, the excitation curve of the voltage transformer unit will not intersect with the U-I characteristic curve of the actual capacitor in the power grid that affects the occurrence of ferroresonance.
2. The oil-immersed insulated combined instrument transformer for ultra-high voltage power systems according to claim 1, characterized in that: The current transformer unit includes a primary winding (10) of the current transformer, and the primary winding (10) of the current transformer passes through the secondary winding (7) of the current transformer.
3. The oil-immersed insulated combined instrument transformer for ultra-high voltage power systems according to claim 2, characterized in that: The aluminum shell (8) of the current transformer is annular, and the secondary winding (7) of the current transformer, which is composed of an annular iron core, is located in the aluminum shell (8). The aluminum shell (8) of the current transformer is provided with annular insulation (9), and the primary winding (10) of the current transformer passes through the center of the annular insulation (9).
4. The oil-immersed insulated combined instrument transformer for ultra-high voltage power systems according to claim 1, characterized in that: The base (6) is provided with a current transformer secondary terminal box (4) and a voltage transformer secondary terminal box (5). The current transformer secondary lead (14) of the current transformer secondary winding (7) passes through the lead through hole (20) and is led into the current transformer secondary terminal box (4). The voltage transformer secondary lead of the voltage transformer secondary winding (15) is led into the voltage transformer secondary terminal box (5).
5. The oil-immersed insulated combined instrument transformer for ultra-high voltage power systems according to claim 1, characterized in that: The voltage transformer core assembly (19) includes a core support (17), the lower end of the voltage transformer core column (13) and the lower end of the insulating tube (11) are both located on the core support (17), and the core support (17) is located on the base (6).