Oil-immersed insulating combined transformer for ultrahigh-voltage electric power system

Abstract

An oil-immersed insulating combined transformer for an ultrahigh-voltage electric power system, wherein a current transformer secondary winding (7) in an oil conservator (2) of the combined transformer is arranged in an aluminum current transformer housing (8); ring insulation (9) is provided outside the aluminum current transformer housing (8); an insulating tube (11) and lead insulation (12) are provided inside a porcelain bushing (3), and the lead insulation (12) and the ring insulation (9) are integrally arranged; the insulating tube (11) supports the aluminum current transformer housing (8) and is arranged in the lead insulation (12); a voltage transformer core assembly (19) comprises a voltage transformer core column (13), which has a lead through hole (20) in the middle and is arranged in the insulating tube (11); a secondary lead of the current transformer secondary winding (7) passes through the lead through hole (20); and a voltage transformer secondary winding (15) is wound on the voltage transformer core column (13) and is arranged between the voltage transformer core column (13) and the insulating tube (11). The transformer can be safely applied to an ultrahigh-voltage electric power system.

Description

An oil-immersed insulated combined transformer for ultra-high voltage power system Technical Field

[0001] The present invention relates to the field of electric power equipment, in particular to an oil-immersed insulated combined mutual inductor for an ultra-high voltage electric power system. Background Art

[0002] Combined instrument transformers are commonly found in medium and low voltage power systems below 35kV. A small number of combined instrument transformers are also used in high voltage power systems below 220kY. The structure of such a combined instrument transformer is generally shown in Figure 9. The secondary winding of the current transformer is placed in an aluminum shell. An aluminum tube is welded to the lower part of the aluminum shell to lead out the secondary lead. The secondary coil is formed by outsourcing the insulation of the current transformer and is arranged on the head of the current transformer body. The primary and secondary windings of the voltage transformer are set on the core column of the voltage transformer with a "mouth" or "sun" shaped iron core to form the voltage transformer body. The combined instrument transformer is formed by assembling the voltage transformer body and the current transformer body in the same body shell. Since the potential of the voltage transformer and the current transformer insulation are distributed in opposite directions inside the porcelain sleeve after the combination, the combined instrument transformer with this structure is difficult to match. In addition, due to the structural limitations of the voltage transformer, it cannot meet the application requirements of ultra-high voltage power systems above 500kV.

[0003] Summary of the Invention

[0004] The purpose of the present invention is to provide an oil-immersed insulated combined transformer for an ultra-high voltage power system, which can not only ensure the reliability of insulation, but also avoid the ferromagnetic harmonic resonance of the voltage transformer unit, while also ensuring the stability of measurement accuracy, and can be safely used in ultra-high voltage power systems.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] An oil-immersed insulated combination transformer for an ultra-high voltage power system comprises an expander, an oil conservator, a porcelain sleeve and a base connected in sequence from top to bottom, wherein a current transformer unit is provided in the oil conservator, a voltage transformer unit is provided in the porcelain sleeve, and the voltage transformer unit comprises a voltage transformer winding assembly and a voltage transformer core assembly; a current transformer aluminum shell is provided in the oil conservator, and a current transformer secondary winding in the current transformer unit is provided in the current transformer aluminum shell, a ring insulation is provided on the outside of the current transformer aluminum shell, an insulating tube and lead insulation are provided in the porcelain sleeve, wherein the lead insulation is integrally provided with the ring insulation, the insulating tube is provided in the lead insulation, and the voltage transformer core assembly comprises a middle strip A voltage transformer core column with a lead through hole, and the voltage transformer core column is arranged 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, wherein the voltage transformer secondary winding is wound on the voltage transformer core column and arranged between the voltage transformer core column and the insulating tube, the voltage transformer primary winding is arranged on the outside of the lead insulation, the voltage transformer primary winding includes a plurality of winding units connected in series in sequence, a plurality of capacitor screens are provided in the lead insulation, and the unit lead connection points of adjacent winding units are connected to the corresponding capacitor screens in the lead insulation at the same potential.

[0007] The current transformer unit includes a current transformer primary winding, and the current transformer primary winding passes through the current transformer secondary winding.

[0008] The current transformer aluminum shell is annular, and the current transformer secondary winding composed of an annular iron core is arranged in the current transformer aluminum shell. The current transformer aluminum shell is provided with an annular insulation, and the current transformer primary winding passes through the center of the annular insulation.

[0009] A current transformer secondary terminal box and a voltage transformer secondary terminal box are provided on the base. 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.

[0010] The voltage transformer core assembly includes a core bracket, the lower end of the voltage transformer core column and the lower end of the insulating tube are both arranged on the core bracket, and the core bracket is arranged on the base.

[0011] The voltage transformer iron core leg is a single-leg, yoke-free iron core structure.

[0012] The winding unit includes a unit seat and a winding wire. A mounting through hole is provided in the middle of the unit seat for the lead wire to pass through insulated. The upper and lower ends of the unit seat are provided with limiting flanges, and the winding wire is wound between the two limiting flanges. The unit leads formed at both ends of the winding wire are respectively passed through the limiting flanges on the corresponding side and connected to the adjacent winding unit.

[0013] The magnetic permeability G of the voltage transformer core is calculated as follows:

[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 leg 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 leg of the voltage transformer, k1, k2, and k3 are empirical coefficients, and d is the equivalent diameter of the core leg of the voltage transformer.

[0015] The excitation current i0 of the voltage transformer unit is calculated as follows:

[0016] In the above formula (2), z B is the equivalent height of the voltage transformer core, m is the rated magnetic flux density, W1 is the number of turns of the primary winding of the voltage transformer, and μ is the magnetic permeability.

[0017] The advantages and positive effects of the present invention are:

[0018] 1. The present invention utilizes the lead insulation integrally provided with the ring insulation of the current transformer unit to serve as the insulation of the voltage transformer unit, and the voltage transformer core leg of the voltage transformer unit adopts a single-core leg yokeless iron core structure, which is provided in the insulating tube supporting the aluminum shell of the current transformer, and the insulating tube is provided in the lead insulation. At the same time, the current transformer secondary lead of the current transformer unit passes through the lead through-hole in the middle of the voltage transformer core leg, and the voltage transformer secondary winding is wound on the voltage transformer core leg and provided in the voltage transformer core leg. Between the core column and the insulating tube, the primary winding of the voltage transformer is wound on the outside of the lead insulation. The combination of the current transformer unit and the voltage transformer unit of the present invention converts the primary large current and ultra-high voltage of the power system into secondary standard current and voltage that can be used for measurement and protection, and the stability of the iron core material ensures the stability of the measurement accuracy. As shown in Figure 7, the excitation curve of the voltage transformer unit of the present invention and the UI characteristic curve of the actual capacitance in the power grid that affects the occurrence of ferromagnetic resonance will not produce an intersection, thereby avoiding the occurrence of ferromagnetic resonance and ensuring the safe operation of the product.

[0019] 2. The primary winding of the voltage transformer of the present invention includes a plurality of winding units sequentially sleeved on the lead insulation from top to bottom, and the unit lead connection points of adjacent winding units are connected to the corresponding capacitor screens in the lead insulation at the same potential. As shown in Figure 8, 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 capacitor screen inside the insulation is close during operation of the product of the present invention, optimizing the field strength distribution in the insulation, and making the insulation more reliable.

[0020] 3. The overall structure of the present invention is more compact, and it also solves the problem that the existing combined transformer cannot meet the application of ultra-high voltage power systems above 500kY due to the structural limitations of the voltage transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of the present invention,

[0022] FIG2 is a front view of the present invention in FIG1 ,

[0023] Figure 3 is an enlarged view of point I in Figure 1,

[0024] FIG4 is a schematic diagram of the structure of the voltage transformer core assembly in FIG1 ,

[0025] FIG5 is a top view of the voltage transformer core assembly in FIG4 ,

[0026] FIG6 is a schematic diagram of the winding unit structure of the primary winding of the voltage transformer in FIG1 ,

[0027] FIG7 is a schematic diagram of the excitation characteristic curve and the capacitance UI characteristic curve of the voltage transformer unit of the present invention,

[0028] FIG8 is a schematic diagram of the voltage distribution characteristic curve of each winding unit of the primary winding of the voltage transformer of the present invention,

[0029] FIG9 is a schematic diagram of the structure of a combined mutual inductor in the prior art.

[0030] Among them, 1 is an expander, 2 is an oil storage cabinet, 3 is a porcelain sleeve, 4 is a current transformer secondary terminal box, 5 is a voltage transformer secondary terminal box, 6 is a base, 7 is a current transformer secondary winding, 8 is a current transformer aluminum shell, 9 is a ring insulation, 10 is a current transformer primary winding, 11 is an insulating tube, 12 is a lead insulation, 13 is a voltage transformer core column, 14 is a current transformer secondary lead, 15 is a voltage transformer secondary winding, 16 is a voltage transformer primary winding, 161 is a winding unit, 1611 is a limit flange, 1612 is a mounting through hole, 162 is a winding wire, 1621 is a unit lead, 17 is a core bracket, 18 is a capacitor screen, 19 is a voltage transformer core assembly, 20 is a lead through hole, 21 is a core, 22 is a current transformer body, and 23 is a voltage transformer body. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] As shown in Figures 1 to 8, the present invention includes an expander 1, an oil conservator 2, a porcelain sleeve 3, and a base 6 connected in sequence from top to bottom, wherein the oil conservator 2 is provided with a current transformer unit, the current transformer unit including a current transformer secondary winding 7 and a current transformer primary winding 10 passing through the current transformer secondary winding 7, and the two ends of the current transformer primary winding 10 are fixed to the oil conservator 2, the porcelain sleeve 3 is provided with a voltage transformer unit, and the voltage transformer unit includes a voltage transformer winding assembly and a voltage transformer core assembly 19, wherein as shown in Figures 4 to 5, the voltage transformer core assembly 19 includes a voltage transformer core column 13 with a lead through hole 20 in the middle. , and as shown in Figures 1 to 3, the current transformer secondary lead 14 of the current transformer secondary winding 7 passes through the lead through-hole 20 and is led to the current transformer secondary terminal box 4 on the base 6, and 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 iron core column 13, and the voltage transformer secondary lead of the voltage transformer secondary winding 15 is led to the voltage transformer secondary terminal box 5 on the base 6, a lead insulation 12 is provided on the outside of the voltage transformer secondary winding 15, and the voltage transformer primary winding 16 is provided on the outside of the lead insulation 12.

[0033] As shown in FIG1 , a current transformer aluminum shell 8 is provided in the oil conservator 2, an insulating tube 11 is provided in the porcelain sleeve 3, and the current transformer aluminum shell 8 is provided at the upper end of the insulating tube 11. The current transformer aluminum shell 8 is supported by the insulating tube 11. The current transformer aluminum shell 8 is annular, and a through hole is provided in the center thereof for the current transformer primary winding 10 to pass through. The current transformer secondary winding 7 composed of an annular iron core is provided in the current transformer aluminum shell 8. The current transformer aluminum shell 8 is provided with a ring insulation 9 on the outside, and the current transformer primary winding 10 is supported by the ring insulation 9. The center passes through, the lead insulation 12 and the ring insulation 9 are integrally arranged, as shown in Figure 3, the insulating tube 11 is arranged in the lead insulation 12, the voltage transformer core column 13 is arranged in the insulating tube 11, and the voltage transformer secondary winding 15 is arranged between the voltage transformer core column 13 and the lead insulation 12. As shown in Figures 1 and 4 to 5, the voltage transformer core assembly 19 includes a core bracket 17, the lower end of the voltage transformer core column 13 and the lower end of the insulating tube 11 are both arranged on the core bracket 17, and the lower end of the core bracket 17 is arranged on the base 6.

[0034] As shown in FIG3 , the lead insulation 12 is inserted with a capacitor screen 18 made of semiconductor material during the wrapping process to better utilize the insulation and evenly insulate the internal electric field.

[0035] As shown in Figure 1, the primary winding 16 of the voltage transformer includes a plurality of winding units 161 arranged in sequence from top to bottom on the outside of the lead insulation 12. As shown in Figure 6, the winding unit 161 includes a unit seat and a winding wire 162, wherein the middle part of the unit seat is provided with a mounting through hole 1612 for the lead insulation 12 to pass through, and the upper and lower ends of the unit seat are provided with limiting flanges 1611, and the winding wire 162 is wound between the two limiting flanges 1611. The unit leads 1621 formed at both ends of the winding wire 162 are respectively passed through the limiting flanges 1611 on the corresponding side and are connected in series with the adjacent winding units 161. In order to ensure that the voltage borne by each winding unit 161 is linearly distributed and has good impact voltage resistance, the connection point of the unit leads 1621 of adjacent winding units 161 is set with an equipotential connection with the corresponding capacitor screen 18 in the lead insulation 12.

[0036] The current transformer unit and voltage transformer unit combination of the present invention converts the primary large 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. The stability of the material of the voltage transformer core column 13 can ensure stable measurement accuracy. In addition, the primary winding 16 of the voltage transformer of the present invention is highly evenly distributed along the voltage transformer core column 13, and the insulation between it and the voltage transformer core column 13 is capacitive insulation.

[0037] The magnetic permeability G of the voltage transformer core leg 13 of the voltage transformer unit of the present invention is calculated as follows:

[0038] In the above formula (1), L is the height of the voltage transformer primary winding 16, M is the height of the voltage transformer core leg 13 above the voltage transformer primary winding 16, b is the average distance between each winding unit 161 of the voltage transformer primary winding 16 and the voltage transformer core leg 13, k1, k2, and k3 are empirical coefficients, and d is the equivalent diameter of the voltage transformer core leg 13.

[0039] The excitation current i0 of the voltage transformer unit of the present invention is calculated as follows:

[0040] In the above formula (2), z is the equivalent height of the voltage transformer core column 13, B m is the rated magnetic flux density, W1 is the primary winding of the voltage transformer with 16 turns, and μ is the magnetic permeability.

[0041] According to the above analysis and calculation and sample tests, the above characteristics make the excitation curve of the voltage transformer unit of the present invention and the U-I characteristic curve of the actual capacitance that affects the occurrence of ferromagnetic resonance in the power grid not intersect (as shown in Figure 7), thereby avoiding the occurrence of ferromagnetic resonance and ensuring the safe operation of the product. Moreover, 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 (as shown in Figure 8), thereby ensuring that the potential of the internal capacitance screens of the lead insulation 12 is close when the present invention is operating, optimizing the field strength distribution inside the lead insulation 12, and making the insulation more reliable.

[0042] The working principle of the present invention is as follows:

[0043] As shown in Figure 9, in the combined transformer structure in the prior art, the secondary winding of the current transformer is placed in an aluminum shell, an aluminum tube is welded at the lower part of the aluminum shell to lead out the secondary lead, and the outer package of the current transformer insulation forms the current transformer body 22 with the secondary coil at the head. The primary and secondary windings of the voltage transformer are sleeved on the "mouth" - shaped or "day" - 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 outer shell to form a combined transformer. In the combined transformer with this structure, due to the reverse distribution of the potentials of the voltage transformer and the current transformer insulation inside the porcelain bushing after combination, it is not easy to cooperate, and due to the structural limitations of the voltage transformer, it cannot meet the requirements of applications in ultra - high - voltage power systems above 500 kV.

[0044] As shown in Figures 1 to 8, the present invention utilizes the lead insulation 12 integrally provided with the ring insulation 9 of the current transformer unit as the insulation of the voltage transformer unit, and the voltage transformer core column 13 adopts a single-core yokeless core structure, the voltage transformer core column 13 is provided in the insulating tube 11 supporting the current transformer aluminum shell 8, and the insulating tube 11 is provided in the lead insulation 12. At the same time, the current transformer 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 voltage transformer secondary winding 15 is wound on the voltage transformer core column 13 and is provided between the voltage transformer core column 13 and the insulating tube 11, the voltage transformer primary winding 16 is wound on the outside of the lead insulation 12, and the voltage transformer primary winding 16 includes a plurality of winding units 161, adjacent The connection point of the unit lead 1621 of the winding unit 161 is set with an equipotential connection with the corresponding capacitor screen 18 in the lead insulation 12. Therefore, the structure of the present invention can not only ensure the reliability of insulation, but also avoid the ferromagnetic harmonic resonance of the voltage transformer unit. At the same time, it can also ensure the stability of measurement accuracy and can be safely used in ultra-high voltage power systems. As shown in Figure 7, the excitation curve of the voltage transformer unit of the present invention and the UI characteristic curve of the actual capacitance in the power grid that affects the occurrence of ferromagnetic resonance will not produce an intersection, thereby avoiding the occurrence of ferromagnetic resonance and ensuring the safety of product operation. As shown in Figure 8, 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 insulation is close during operation of the product of the present invention, optimizing the field strength distribution in the insulation, and making the insulation more reliable.

Claims

1. An oil-immersed insulated combined transformer for an ultra-high voltage power system, characterized in that: The invention comprises an expander (1), an oil storage cabinet (2), a porcelain sleeve (3) and a base (6) which are connected in sequence from top to bottom, wherein a current transformer unit is arranged in the oil storage cabinet (2), a voltage transformer unit is arranged in the porcelain sleeve (3), and the voltage transformer unit comprises a voltage transformer winding assembly and a voltage transformer iron core assembly (19); a current transformer aluminum shell (8) is arranged in the oil storage cabinet (2), and a current transformer secondary winding (7) in the current transformer unit is arranged at In the current transformer aluminum shell (8), a ring insulation (9) is provided outside the current transformer aluminum shell (8), an insulating tube (11) and a lead insulation (12) are provided inside the porcelain sleeve (3), wherein the lead insulation (12) and the ring insulation (9) are integrally arranged, the insulating tube (11) is arranged in the lead insulation (12), the voltage transformer core assembly (19) comprises a voltage transformer core column (13) with a lead through hole (20) in the middle, and The voltage transformer iron core column (13) is arranged in the insulating tube (11), the current transformer secondary lead (14) of the current transformer secondary winding (7) passes through the lead through hole (20), and 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 iron core column (13) and arranged on the voltage transformer. The primary winding (16) of the voltage transformer is arranged between the core column (13) of the transformer and the insulating tube (11), and the primary winding (16) of the voltage transformer is arranged outside the lead insulation (12). The primary winding (16) of the voltage transformer includes a plurality of winding units (161) connected in series in sequence, and a plurality of capacitor screens (18) are arranged in the lead insulation (12), and the connection points of the unit leads (1621) of adjacent winding units (161) are connected to the corresponding capacitor screens (18) in the lead insulation (12) at the same potential.

2. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1, characterized in that: The current transformer unit comprises a current transformer primary winding (10), and the current transformer primary winding (10) passes through the current transformer secondary winding (7).

3. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 2, characterized in that: The current transformer aluminum shell (8) is annular, and the current transformer secondary winding (7) composed of an annular iron core is arranged in the current transformer aluminum shell (8). The current transformer aluminum shell (8) is provided with an annular insulation (9) outside, and the current transformer primary winding (10) passes through the center of the annular insulation (9).

4. The oil-immersed insulated combined transformer for an ultra-high voltage power system 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 wire (14) of the current transformer secondary winding (7) passes through the lead wire through hole (20) and is led into the current transformer secondary terminal box (4); the voltage transformer secondary lead wire of the voltage transformer secondary winding (15) is led into the voltage transformer secondary terminal box (5).

5. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1, characterized in that: The voltage transformer core assembly (19) comprises 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 arranged on the core support (17), and the core support (17) is arranged on the base (6).

6. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1 or 5, characterized in that: The voltage transformer iron core column (13) is a single-column iron core structure without a yoke.

7. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1, characterized in that: The winding unit (161) comprises a unit seat and a winding wire (162); a mounting through hole (1612) is provided in the middle of the unit seat for the lead wire insulation (12) to pass through; the upper and lower ends of the unit seat are provided with limiting flanges (1611), and the winding wire (162) is wound between the two limiting flanges (1611); the unit leads (1621) formed at both ends of the winding wire (162) are respectively passed through the limiting flanges (1611) on the corresponding sides and connected to the adjacent winding unit (161).

8. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1, characterized in that: The magnetic permeability G of the voltage transformer iron core column (13) is calculated as follows: 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 iron 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 iron core column (13), k1, k2, k3 are empirical coefficients, and d is the equivalent diameter of the iron core column (13) of the voltage transformer.

9. The oil-immersed insulated combined transformer for an ultra-high voltage power system according to claim 1, characterized in that: The excitation current i0 of the voltage transformer unit is calculated as follows: In the above formula (2), z is the equivalent height of the voltage transformer core column (13), B m is the rated magnetic flux density, W1 is the number of turns of the primary winding (16) of the voltage transformer, and μ is the magnetic permeability.

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