A transformer with continuously adjustable impedance and an adjustment method

Abstract

The present invention belongs to the field of transformers, and specifically discloses a transformer with continuously adjustable impedance. Among them, it includes: a core column; a low-voltage coil, a medium-voltage coil, and a high-voltage coil wound around the core column in sequence from inside to outside; a side column arranged on one side of the core column; an exciting coil, a voltage regulating coil, and an impedance regulating coil wound around the side column in sequence from inside to outside; the medium-voltage coil, the impedance regulating coil, and the exciting coil are connected in series in sequence. The present invention uses an impedance regulating coil to replace a reactor to adjust the impedance of the transformer, so that two axially parallel ampere-turn balanced coils with adjustable number of turns are directly wound on the core column. By adjusting the number of turns of the parallel ampere-turn balanced coil, the continuity and large-range adjustment of the transformer impedance are realized. The structure is simple and the occupied space in the oil tank is greatly reduced, reducing the manufacturing cost of such transformers.

Description

Technical Field

[0001] The invention belongs to the technical field of transformers, and in particular relates to a transformer capable of continuously adjusting impedance and an adjustment method. Background Art

[0002] When a conductor is energized, it will generate a magnetic field in a certain space it occupies, so all current-carrying conductors have inductance in a general sense. Impedance is an extremely important parameter of power transformers. It determines the short-circuit current and voltage regulation of the transformer, and has an important impact on the operation of the transformer, so power transformers must consider impedance. Impedance voltage is the percentage of the short-circuit voltage applied to the primary winding to the rated voltage when the short-circuit current of the secondary winding reaches the rated current by short-circuiting the secondary winding of the transformer and slowly increasing the voltage of the primary winding. The series reactor used in the power system is mainly used to limit the short-circuit current.

[0003] If you want to significantly change the transformer impedance under certain working conditions, the conventional way is to add a reactor and connect it in series with a coil in the winding package to achieve a significant change in the transformer impedance. This type of reactor cannot be wound on the iron core column of the transformer body. It is generally placed in a certain area inside the oil tank. It has only electrical connection with the transformer body, but no magnetic connection. Therefore, the reactor is not on the iron core magnetic circuit of the transformer body.

[0004] With the development of the electric power industry, the power system and power operation departments have such a demand. A transformer with continuously adjustable impedance is needed as a backup phase. When a transformer at a station is out of operation due to a fault or other reasons, this backup phase can be used to replace it, so as not to cause major accident hazards such as long-term, large-scale power outages. The premise that the backup phase can replace the faulty transformer and operate in the line is that the impedance must match the original faulty transformer.

[0005] Setting up a reactor in a transformer requires a large space to be reserved in the transformer oil tank, which increases the production cost of the transformer. In addition, the impedance of a conventional transformer changes under different extreme tapping conditions of the voltage regulating coil, but the technical specifications require that the impedance change range is very small when the impedance is at the maximum, rated, and minimum tapping. In order to achieve large-scale and continuous impedance adjustment, it is impossible to simply change the number of turns of the voltage regulating coil. Summary of the invention

[0006] The invention provides a transformer capable of continuously adjusting impedance, so as to solve the problems of high impedance adjustment cost and inability to adjust impedance continuously of the current transformer.

[0007] To solve the above technical problems, the technical solution of the present invention is: a transformer with continuously adjustable impedance, which includes: a core column; a low-voltage coil, a medium-voltage coil, and a high-voltage coil wound around the core column from the inside out in sequence; a side column arranged on one side of the core column; an exciting coil, a voltage regulating coil, and an impedance regulating coil wound around the side column from the inside out in sequence; the medium-voltage coil, the impedance regulating coil, and the exciting coil are connected in series in sequence.

[0008] In a preferred embodiment of the present invention, the transformer does not include a reactor.

[0009] In a preferred embodiment of the present invention, the impedance regulating coil includes two ampere-turn balance coils, and the two ampere-turn balance coils are connected in parallel axially.

[0010] In a preferred embodiment of the present invention, the number of turns of the ampere-turn balance coil is 50 - 200 turns.

[0011] In a preferred embodiment of the present invention, the directions of the currents flowing through the two ampere-turn balance coils are opposite.

[0012] In a preferred embodiment of the present invention, an adjusting switch for changing the number of turns connected is arranged on the ampere-turn balance coil.

[0013] In a preferred embodiment of the present invention, the ampere-turn balance coil is wound with transposed conductors, the transposed conductors include a plurality of enameled copper flat wires, and the transposed conductors are multi-core transposed conductors.

[0014] In a preferred embodiment of the present invention, the wire width of the enameled copper flat wire is below 5.5 mm, and the wire thickness is less than 1.3 mm.

[0015] The present invention also discloses an impedance regulating method for the transformer according to any one of claims 1 - 8, which is characterized in that the steps include:

[0016] S1: Perform magnetic field energy simulation according to the transformer design parameters to obtain the magnetic field energy storage value W;

[0017] S2: Obtain the per-unit value U of the high-medium impedance through formula (1) K :

[0018]

[0019] where ω is the angular velocity, W is the magnetic field energy storage, I is the current value, and R is the impedance base value;

[0020] The impedance base value R is obtained through formula (2):

[0021]

[0022] where U额 is the rated voltage of the transformer, V 额 is the rated capacity of the transformer;

[0023] S3: Replace the number of turns n of the access of the different ampere-turn balance coils, repeat S1 and S2 to calculate the corresponding per-unit value U of the high-medium impedance K ;

[0024] S4: Determine the mapping relationship between the number of turns n of the access of the ampere-turn balance coils and the per-unit value U of the high-medium impedance K ;

[0025] S5: Test or calculate the target per-unit value U of the high-medium impedance of the actual transformer, and determine the number of turns n of the access of the ampere-turn balance coils from the mapping relationship between the number of turns n of the access of the ampere-turn balance coils and the per-unit value U of the high-medium impedance, and access the corresponding number of turns n in the actual transformer. K In a preferred embodiment of the present invention, in step S1, the magnetic field energy simulation method is the MAGNET time-harmonic field method. K Compared with the prior art, the technical solution provided by the present invention has the following advantages: The present invention uses an impedance adjustment coil to replace the reactor to adjust the impedance of the transformer, so that two axially parallel ampere-turn balance coils with adjustable turns are directly wound on the iron core column, and by adjusting the number of turns of the parallel ampere-turn balance coils, the continuity and large-range adjustment of the transformer impedance are realized. The structure is simple and the occupied space in the fuel tank is greatly reduced, and the manufacturing cost of such transformers is reduced.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings. FIG.

[0028] is a schematic diagram of the coil arrangement of a transformer with continuously adjustable impedance according to an embodiment of the present invention;

[0029] Figure 1 is a schematic wiring diagram of a transformer with continuously adjustable impedance according to an embodiment of the present invention.

[0030] Figure 2 As shown in the figure:

[0031] Shown in the figure:

[0032] 10 - Iron core column; 11 - Low - voltage coil; 12 - Medium - voltage coil; 13 - High - voltage coil; 20 - Side column; 21 - Excitation coil; 22 - Voltage - regulating coil; 23 - Impedance - regulating coil. Detailed implementation manners

[0033] For the convenience of understanding, the following describes the transformer capable of continuously adjusting impedance in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0034] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation and positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0036] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0037] As Figure 1 shown, the present invention discloses a transformer capable of continuously adjusting impedance and an adjustment method. Among them, it includes an iron core column 10, a low - voltage coil 11, a medium - voltage coil 12, and a high - voltage coil 13 wound around the iron core column 10 in sequence from the inside to the outside, a side column 20 arranged on one side of the iron core column 10, and an excitation coil 21, a voltage - regulating coil 22, and an impedance - regulating coil 23 wound around the side column 20 in sequence from the inside to the outside.

[0038] The transformer in the present invention does not include a reactor. The impedance - regulating coil 23 is used to connect the medium - voltage coil 12, the impedance - regulating coil 23, and the excitation coil 21 in series in sequence. In combination withFigure 2 As shown, the impedance regulating coil 23 includes two ampere-turn balanced coils, which are axially connected in parallel. The number of turns of each ampere-turn balanced coil is 50 - 200 turns, and the directions of the currents flowing through the two ampere-turn balanced coils are opposite.

[0039] What is not shown in the figure is that an adjusting switch for changing the number of turns connected is provided on the ampere-turn balanced coil. By changing the tap level of the adjusting switch, the number of turns connected of the two ampere-turn balanced coils can be made equal. Since the adjustment of the tap switch is continuous, continuous adjustment of the transformer impedance can thus be achieved.

[0040] Since the impedance regulating coil itself will generate additional losses after being energized, in the present invention, the ampere-turn balanced coil is wound with multi-core transposed conductors. The ampere-turn balanced coil is wound with transposed conductors, and the transposed conductors include several enameled copper rectangular wires. The transposed conductors are multi-core transposed conductors. The wire width of the enameled copper rectangular wire is below 5.5 mm, and the wire thickness is less than 1.3 mm. By using multi-core transposed conductors and reducing the wire width of the enameled copper rectangular wire, the losses are far less than those brought by using a reactor. Experiments show that the loss cost is less than 5% of the cost of a reactor.

[0041] Referring to Figure 2 As shown, the steps of impedance regulation using the transformer in this solution include:

[0042] S1: Perform magnetic field energy simulation using the MAGNET time-harmonic field method according to the transformer design parameters to obtain the magnetic field energy storage value W;

[0043] S2: Obtain the high-medium impedance per-unit value U through Equation (1) K :

[0044]

[0045] where ω is the angular velocity, W is the magnetic field energy storage, I is the current value, and R is the impedance base value;

[0046] The impedance base value R is obtained through Equation (2):

[0047]

[0048] where U 额 is the rated voltage of the transformer, and V 额 is the rated capacity of the transformer;

[0049] S3: Change the number of turns n connected of different ampere-turn balanced coils, and repeat S1 and S2 to calculate the corresponding high-medium impedance per-unit value U K ;

[0050] S4: Determine the number of turns n of the ampere-turn balanced coil and the per-unit value U of the high-medium impedance K The mapping relationship;

[0051] S5: Test or calculate the target high-medium impedance per unit value U of the actual transformer K , from the number of turns n of the ampere-turn balanced coil and the per-unit value of high-medium impedance U K The number of turns n of the ampere-turn balanced coil is determined in the mapping relationship, and the corresponding number of turns n is connected in the actual transformer. The mapping relationship is a discrete data group or a mapping function fitted according to the discrete data group.

[0052] Taking a 500kV single-phase autotransformer ODFS-334000 / 500kV as an example, the parameters of this type of transformer are as follows:

[0053] Rated capacity (kVA) high / medium / low: 334000 / 334000 / 100000; rated voltage (kV) high / medium / low: (505√3) / (230 / √3)±2×2.5% / 36; rated current (A): high / medium / low: 1145.6 / 1380.2 / 2777.8.

[0054] In the original structure transformer body, the magnetic field energy W obtained by finite element numerical calculation is 57604.1061117916 J. According to the magnetic field energy storage formula Where: W is magnetic field energy storage, L is inductance, and I is current.

[0055] The magnetic field energy storage W can be obtained through the numerical simulation of the magnetic field, where the current I is a known quantity. Thus, the inductance L = 0.175569H and the inductive reactance ωL = 55.15658Ω can be calculated; the impedance base value From this, the high-medium impedance is calculated as: U k =55.15658 / 254.516=21.6712%.

[0056] Taking the ampere-turn balanced coil with 100 turns as an example, the finite element numerical calculation results in the magnetic field energy W = 70810.5983280587J, inductance L = 0.215831106H, inductive reactance: ωL = 67.80534163Ω, and the impedance base value: R = 254.516. Therefore, the high-medium impedance is calculated as: U k =26.6409%, achieving the continuity and wide adjustment of high-medium impedance between 18% and 27%.

[0057] Repeat the above simulation experiments and calculations multiple times, and draw a corresponding table between the ampere-turn balanced coil and the per-unit value of the high and medium impedance. The relationship between the number of turns of the ampere-turn balanced coil of a 500 kV single-phase auto-transformer ODFS-334000 / 500 kV and the per-unit value of the high-medium impedance is as follows:

[0058] Ampere-turn balance type coil turns Per-unit value of high-medium impedance 0 21.671 20 22.665 40 23.659 60 24.653 80 25.647 100 26.641

[0059] In this embodiment, a simulation experiment is carried out every 20 turns, so as to obtain the mapping relationship between the number of turns n of the ampere-turn balanced coil and the per-unit value of the high-medium impedance. In actual use, the number of turns to be connected is determined according to the target per-unit value of the high-medium impedance. For example, when the target per-unit value of the high-medium impedance is 25.647, 80 turns can be directly connected.

[0060] The present invention uses an impedance regulating coil to replace the reactor to regulate the impedance of the transformer, so that two axially parallel ampere-turn balanced coils with adjustable number of turns are directly wound on the iron core column. By adjusting the number of turns of the parallel ampere-turn balanced coil, the continuity and large-range adjustment of the transformer impedance are realized. The structure is simple and the occupied space in the oil tank is greatly reduced, and the manufacturing cost of such transformers is reduced.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transformer with continuously adjustable impedance, characterized in that, Comprising: Core column; A low-voltage coil, a medium-voltage coil, and a high-voltage coil wound around the core column from inside to outside in sequence; a side column provided on one side of the core column; An exciting coil, a voltage regulating coil, and an impedance regulating coil wound around the side column from inside to outside in sequence; the medium-voltage coil, the impedance regulating coil, and the exciting coil are connected in series in sequence; The impedance regulating coil includes two ampere-turn balanced coils, and the two ampere-turn balanced coils are axially connected in parallel; The impedance regulating method of the continuously adjustable impedance transformer includes the following steps: S1: Perform magnetic field energy simulation according to the transformer design parameters to obtain the magnetic field energy storage value W; S2: Obtain the per-unit value U of high-medium impedance through Equation (1) K : Wherein, ω is the angular velocity, W is the magnetic field energy storage, I is the current value, and R is the impedance base value; The impedance base value R is obtained through formula (2): Among them, U 额 is the rated voltage of the transformer, V 额 is the rated capacity of the transformer; S3: Replace the number of turns n of the access of the ampere-turn balance coil, and repeat S1 and S2 to calculate the corresponding per-unit value U of the high-medium impedance K ; S4: Determine the mapping relationship between the number of turns n of the ampere-turn balance coil and the per-unit value U of the high-medium impedance K ; S5: Test or calculate the per-unit value U of the target high-medium impedance of the actual transformer K , and determine the number of turns n of the ampere-turn balance type coil from the mapping relationship between the number of turns n of the ampere-turn balance type coil and the per-unit value U K of the high-medium impedance, and connect the corresponding number of turns n in the actual transformer.

2. The transformer capable of continuously adjusting impedance according to claim 1, wherein: The transformer does not include a reactor.

3. The transformer capable of continuously adjusting impedance according to claim 1, wherein: The number of turns of the ampere-turn balanced coil is 50 - 200 turns.

4. A transformer capable of continuously adjusting impedance according to claim 1, characterized in that: The directions of the currents flowing through the two ampere-turn balanced coils are opposite.

5. The transformer with continuously adjustable impedance according to claim 1, wherein: An adjusting switch for changing the number of turns connected is provided on the ampere-turn balanced coil.

6. The transformer capable of continuously adjusting impedance according to claim 1, wherein: The ampere-turn balanced coil is wound with transposed conductors, the transposed conductors include a plurality of enameled copper flat wires, and the transposed conductors are multi-core transposed conductors.

7. A transformer with continuously adjustable impedance according to claim 6, characterized in that: The width of the enameled copper flat wire is below 5.5 mm, and the thickness is less than 1.3 mm.

8. An impedance adjustment method for a transformer according to any one of claims 1-7, characterized in that: steps Comprising: S1: Perform magnetic field energy simulation according to the transformer design parameters to obtain the magnetic field energy storage value W; S2: Obtain the per-unit value U of high-medium impedance through formula (1) K : Wherein, ω is the angular velocity, W is the magnetic field energy storage, I is the current value, and R is the impedance base value; The impedance base value R is obtained through formula (2): Among them, U 额 is the rated voltage of the transformer, V 额 is the rated capacity of the transformer; S3: Replace the number of turns n of the tapped turns of different ampere-turn balance coils, and repeat S1 and S2 to calculate the corresponding per-unit value U of the high-medium impedance K ; S4: Determine the mapping relationship between the number of turns n of the ampere-turn balanced coil and the per-unit value U of the high-medium impedance K ; S5: Test or calculate the per-unit value U of the target high-medium impedance of the actual transformer K , determine the number of turns n of the ampere-turn balance type coil from the mapping relationship between the number of turns n of the ampere-turn balance type coil and the per-unit value U K of the high-medium impedance, and connect the corresponding number of turns n in the actual transformer.

9. The impedance regulation method of the transformer according to claim 8, characterized in that: The magnetic field energy simulation method in step S1 is the MAGNET time-harmonic field method.

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