Electrically insulating multilayer coil for power transformer
By introducing irregular overhang lengths into the multilayer coils of the power transformer to form a zigzag or progressive profile, the problem of arcing caused by traditional insulating fluids is solved, achieving higher insulation capacity and lower risk of pollution.
Patent Information
- Application Number
- CN202380071178.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-07
- Filing Date
- 2023-10-07
- Publication Date
- 2025-06-03
AI Technical Summary
In existing power transformers, arcs are likely to occur when using traditional insulating fluids, and when replaced with fluids with less contaminated, the insulation may be damaged, resulting in breakdown.
By introducing irregular overhang lengths into the electrically insulating layer of the multilayer coil, a serrated or progressive profile is formed, thereby improving the insulation capacity and preventing arcs from occurring.
It effectively improves the insulation capacity and prevents the occurrence of electric arcs. It is suitable for use of insulating fluids with dielectric strength lower than sulfur hexafluoride, reducing the risk of pollution.
Smart Images
Figure CN120092309A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of power transformers, and more particularly to multi-layer coils for power transformers. Background Art
[0002] Power transformers of the type described in IEC61869-1, IEC61869-3 and IEC61869-4 standards are known. This type of transformer includes a multi-layer coil (10), as Figure 1 shown. The coil (10) generally includes a conductive part (101) and an electrical insulation part (102).
[0003] The conductive part (101) includes a plurality of conductive layers. Each of the conductive layers includes a wire that is helically wound around an axis (A0) and axially extends from a first plane orthogonal to the axis to a second plane orthogonal to the axis. The conductive layers are arranged coaxially with each other.
[0004] The electrical insulation part (102) includes a plurality of electrical insulation layers. Each of the electrical insulation layers is arranged between two of the conductive layers such that the two conductive layers are insulated from each other. In practice, each of the electrical insulation layers can be in the form of a plurality of stacked insulator layers of the same length. The electrical insulation layer includes a first overhang region and a second overhang region, and the first overhang region and the second overhang region extend axially in the axial direction with a first overhang length and a corresponding second overhang length, respectively, beyond the first orthogonal plane and the corresponding second orthogonal plane of the longer conductive layer among the two conductive layers. These overhang regions are involved in limiting the generation of arcs between the conductive layers at the ends of the coil (10). This overhang length is the same for all layers. In addition, the overhang regions prevent the wires from slipping off the coil due to the mechanical tension applied by the machine during the winding process.
[0005] To increase the insulation between the conductive layers at the ends of the coil (10), the coil is arranged in a pressurized housing, and an electrical insulating fluid is injected into the housing to wrap the coil. These can be oil-based fluids or gas-based fluids.
[0006] However, the fluids with the best electrical insulation performance are also the most polluting fluids. We refer to these commonly used high-performance fluids as traditional insulating fluids. This is especially true for sulfur hexafluoride (SF6). Therefore, it is necessary to develop solutions that use less polluting fluids, such as oxygen, dinitrogen, carbon dioxide, fluoronitrile, fluoroketone, fluoronitrile or a mixture of fluoroketone and oxygen or dinitrogen or carbon dioxide, a mixture of sulfur hexafluoride and a large amount of dinitrogen, etc.
[0007] However, for the time being, simply replacing one fluid with another may damage the insulation to such an extent that an electric arc, called breakdown, may occur. On such transformers with a pressurized housing, the occurrence of an electric arc often leads to damage to the coils.
[0008] Accordingly, it is an object of the present invention to provide a multi-layer coil for a power transformer that is suitable for use with an insulating fluid having a dielectric strength lower than sulfur hexafluoride and preferably less polluting than conventional insulating fluids. Summary of the Invention
[0009] The solution proposed by the present invention is a coil for a power transformer, comprising:
[0010] - a conductive part, which comprises a plurality of conductive layers, each of the conductive layers comprising a wire that is helically wound around an axis and axially extends from a first plane orthogonal to the axis to a second plane orthogonal to the axis, the conductive layers being arranged coaxially around one another,
[0011] - an electrical insulation part, which comprises a plurality of electrical insulation layers, each of the electrical insulation layers being arranged between two of the conductive layers to insulate the two conductive layers from one another, the electrical insulation layers comprising a first overhang region and a second overhang region, the first overhang region and the second overhang region extending axially beyond the first plane and respectively the second plane of the longer of the two conductive layers by a first overhang length and respectively a second overhang length.
[0012] The coil is characterized in that the first overhang length and / or the second overhang length of at least one first electrical insulation layer is greater than the first overhang length and / or respectively the second overhang length of at least one other electrical insulation layer.
[0013] Thus, creating irregularities in the overhang lengths of the different electrical insulation layers makes it possible to increase the insulation capacity to prevent the occurrence of an electric arc.
[0014] According to another advantageous feature of the present invention, by creating significant irregularities, the insulation capacity can be increased to prevent the appearance of an electric arc:
[0015] - each wire of the conductive layers has a diameter, and
[0016] - the first overhang length or the second overhang length of at least one first electrical insulation layer is at least twenty times greater than the first overhang length or respectively the second overhang length of a second electrical insulation layer by the diameter of the wire.
[0017] According to another advantageous feature of the present invention, by optimizing the overhang lengths, the insulation capacity can be increased to prevent the appearance of an electric arc:
[0018] - each wire of the conductive layers has a diameter, and
[0019] - The first and second overhang lengths of each electrically insulating layer are forty to three hundred and twenty times the diameter of the wire.
[0020] According to another advantageous feature of the present invention, by creating a serrated profile, the insulating ability can be improved to prevent the occurrence of electric arcs:
[0021] - The wire of each conductive layer has a diameter, and
[0022] - The electrically insulating layer is divided into a short overhang group and a long overhang group,
[0023] - The first and second overhang lengths of the electrically insulating layer of the short overhang group are forty to one hundred times the diameter of the wire,
[0024] - The first and second overhang lengths of the electrically insulating layer of the long overhang group are one hundred and twenty to three hundred and twenty times the diameter of the wire.
[0025] According to another advantageous feature of the present invention, by optimizing the width and thickness of the groove, the insulating ability can be improved to prevent the occurrence of electric arcs:
[0026] - The short overhang group consists of two to four short overhang subgroups of consecutive electrically insulating layers,
[0027] - The long overhang group consists of two to four long overhang subgroups of consecutive electrically insulating layers,
[0028] - The insulating portion is formed by the alternation between the short overhang subgroups and the long overhang subgroups.
[0029] According to another advantageous feature of the present invention, by creating an asymmetric serrated profile at both ends of the coil, the insulating ability can be improved to prevent the occurrence of electric arcs:
[0030] - The wire of each conductive layer has a diameter, and
[0031] - The electrically insulating layer is divided into a group with a first short overhang and a second long overhang, and a group with a first long overhang and a second short overhang,
[0032] - The first overhang length of the electrically insulating layer of the group with a first short overhang and a second long overhang, and the second overhang length of the electrically insulating layer of the group with a first long overhang and a second short overhang are forty to one hundred times the diameter of the wire,
[0033] - The second overhang length of the electrically insulating layer of the group with a first short overhang and a second long overhang, and the first overhang length of the electrically insulating layer of the group with a first long overhang and a second short overhang are one hundred and twenty to three hundred and twenty times the diameter of the wire.
[0034] According to another advantageous feature of the present invention, by optimizing the width and thickness of the grooves, the insulation ability can be improved to prevent the occurrence of electric arcs:
[0035] - The group having the first short overhang and the second long overhang consists of subgroups of the first short overhang and the second long overhang having two to four consecutive electrically insulating layers,
[0036] - The group having the first long overhang and the second short overhang consists of subgroups of the first long overhang and the second short overhang having two to four consecutive electrically insulating layers,
[0037] - The insulating portion is formed by an alternation between the subgroup having the first short overhang and the second long overhang and the subgroup having the first long overhang and the second short overhang.
[0038] According to another advantageous feature of the present invention, which makes it possible to produce a more gradually varying profile of the length by successively selecting the electrically insulating layers radially from the inside out, thereby improving the insulation ability to prevent the occurrence of electric arcs, the first overhang length and / or the second overhang length of the electrically insulating layer increases relative to the first overhang length and / or the second overhang length of the previous electrically insulating layer until a maximum length is reached, or decreases correspondingly until a minimum length is reached, and then decreases until the said minimum length is reached, or increases correspondingly until the said maximum length is reached.
[0039] According to another advantageous feature of the present invention, by optimizing the minimum length and the maximum length, the insulation ability can be improved to prevent the occurrence of electric arcs, the minimum length being between forty and one hundred times the diameter of the wire and the maximum length being between one hundred and twenty and three hundred and twenty times the diameter of the wire.
[0040] According to another advantageous feature of the present invention, the insulation ability can be improved to prevent the occurrence of electric arcs if the first overhang length and / or the second overhang length increases or decreases according to a sine function.
[0041] Another aspect of the present invention relates to a power transformer comprising
[0042] - a housing,
[0043] - at least one coil arranged inside the housing, and
[0044] - an electrically insulating fluid which is arranged inside the housing and surrounds the at least one coil.
[0045] The transformer is characterized in that the at least one coil is a coil as defined above.
[0046] Thus, in such a transformer, by creating irregularities in the overhang lengths of the different electrically insulating layers, the insulation ability can be improved to prevent the occurrence of electric arcs. Description of the Drawings
[0047] Other features and advantages of the present invention will become apparent from the following description of specific embodiments of the invention, which are given by way of example and are not limiting, with reference to the accompanying drawings, in which:
[0048] Figure 1 Schematic cross-sectional view of a coil of the prior art;
[0049] Figure 2 Is a schematic cross-sectional view of a first exemplary embodiment of a coil forming the object of the present invention, the coil having a symmetrical serrated insulation profile;
[0050] Figure 3 Is Figure 2 Schematic diagram of detail D1 of the first exemplary embodiment shown;
[0051] Figure 4 Is Figure 2 Schematic diagram of detail D2 of the first exemplary embodiment shown;
[0052] Figure 5 Is a schematic cross-sectional view of a second exemplary embodiment of a coil forming the object of the present invention, the coil having an asymmetrical serrated insulation profile;
[0053] Figure 6 Is a schematic cross-sectional view of a third exemplary embodiment of a coil forming the object of the present invention, the coil having a symmetrical sinusoidal insulation profile.
[0054] Figure 7 Is a schematic cross-sectional view of a fourth exemplary embodiment of a coil forming the object of the present invention, the coil having an insulation profile with a constant short overhang length;
[0055] Figure 8 Is a schematic cross-sectional view of a fifth exemplary embodiment of a coil forming the object of the present invention, the coil having a cylindrical conductive profile and a symmetrical serrated insulation profile;
[0056] Figure 9 Is a schematic cross-sectional view of a sixth exemplary embodiment of a coil forming the object of the present invention, the coil having a parabolic conductive profile and a symmetrical serrated insulation profile.
[0057] Figures 1 to 9 Do not reflect the actual dimensions of the components. For the convenience of the reader's understanding, the dimensions of some elements may be enlarged or reduced. In particular, the ratio of the overhang length to the wire diameter shown in the figures does not reflect the actual situation. Detailed Description
[0058] The present invention relates to a coil (1) for a power transformer. The power transformer can be a measuring transformer, a power transformer, or one of other types of transformers. The power transformer can be single-phase or three-phase.
[0059] The coil (1) comprises a conductive part (11). The latter comprises a plurality of conductive layers (11a, 11b, 11c, 11d, 11f, etc.). In other parts of the description, for the sake of simplicity, any conductive layer among all the conductive layers is designated as the conductive layer (11i). "i" is a variable and can take on the letters of the alphabet as values in order to distinguish between the conductive layers, as in the examples of Figure 3 and Figure 4 . Among them:
[0060] - i = a represents the conductive layer (11a) closest to the axis,
[0061] - i = b represents the second conductive layer (11b) closest to the axis (A),
[0062] - i = c represents the third conductive layer (11c) closest to the axis (A),
[0063] - and so on.
[0064] Alternatively, the variables "j" or "k" can be used in a similar manner in other parts of the description.
[0065] In practice, the coil (1) can comprise 50 to 150 conductive layers (11i). Each of the conductive layers (11i) comprises a wire (111). The wire (111) is preferably an enameled wire. The wire (111) preferably comprises a core made of copper, but it can be made of aluminum or any other conductive material considered suitable by those skilled in the art. The wire (111) of each conductive layer (11i) can have a diameter (D). The latter can be from 0.125 mm to 0.3 mm. The wire (111) is wound around the axis (A) in a helical form and extends axially from a first plane (P1i) orthogonal to the axis (A) to a second plane (P2i) orthogonal to the axis (A). The conductive layers (11i) are arranged coaxially with each other.
[0066] Each turn of the wire (111) in the conductive layer (11i) is called a turn. For each conductive layer (11i), the number of turns can be from 1 to 2500. In some embodiments, for example Figures 2 to 6 and Figure 9 in the illustrated embodiments, the number of turns can decrease from the conductive layer (11a) closest to the axis to the conductive layer furthest from the axis. The number of turns can decrease linearly, as in the embodiment Figures 2 to 6 shown. This type of coil is generally referred to as a "trapezoidal coil". The number of turns can decrease in a non-linear manner, for example as inFigure 9 In the exemplary embodiment shown, it decreases according to a parabola. A coil of the latter type is generally referred to as a "parabolic coil". In other embodiments, especially in Figure 8 the exemplary embodiment of, the number of turns of all the conductive layers (11i) can be the same. A coil of this type is generally referred to as a "cylindrical coil". In other embodiments not shown, for every three to ten conductive layers (11i), the number of turns can be reduced by one to five turns.
[0067] The coil (1) further includes an electrical insulation part (12). The electrical insulation part (12) includes a plurality of electrical insulation layers (12i). In other parts of the description, for the sake of simplicity, we will designate any electrical insulation layer among all the electrical insulation layers as the electrical insulation layer (12i). "i" is a variable and can take on the letters of the alphabet as values in order to distinguish between the electrical insulation layers, as in Figure 3 and Figure 4 the example of, where:
[0068] - i = a represents the electrical insulation layer (12a) closest to the axis,
[0069] - i = b represents the electrical insulation layer (12b) second closest to the axis (A),
[0070] - i = c represents the electrical insulation layer (12c) third closest to the axis (A),
[0071] - and so on.
[0072] Alternatively, the variables "j" or "k" can be used in a similar manner in other parts of the description.
[0073] Each electrical insulation layer (12i) includes one or more electrical insulation materials of the polyester film type, and both side portions thereof are covered with glue or other materials. Preferably, the dielectric strength of the insulation material is greater than 50 kV / mm. Each of the electrical insulation layers (12i) is arranged between two of the conductive layers (11i) so as to insulate the two conductive layers from each other. In practice, the electrical insulation layer (12i) can be made by winding a strip of electrical insulation material around the conductive layer. In this case, the width of the strip of electrical insulation material can be from 50 mm to 350 mm, and the thickness can be from 20 μm to 50 μm. The winding can be edge-to-edge or with an overlap. The electrical insulation layer (12i) can include a plurality of stacked turns made of the same insulation material or different insulation materials. Advantageously, the electrical insulation layer (12i) includes 2 to 4 stacked turns.
[0074] Each electrical insulation layer (12i) includes a first overhang region and is extended by the first overhang region, and the first overhang region extends axially along a first overhang length (L1i) beyond the first orthogonal plane (P1i) of the longer of two adjacent conductive layers (11i).
[0075] As can also be seen from the figures, for all embodiments to be described, the conductive layers (11i) at least partially overlap axially.
[0076] The electrical insulation layers (12i) are generally cylindrical, and the electrical insulation layers (12i) are arranged coaxially around each other and at least partially overlap axially.
[0077] For example, with reference to Figure 3 , the electrical insulation layer (12a) includes a first overhanging region that extends axially by a first overhanging length (L1a) beyond the first orthogonal plane (P1a) of the longer of two adjacent conductive layers (11a, 11b). The same applies to:
[0078] - for the electrical insulation layer (12b) having a first overhanging length (L1b) with respect to the first orthogonal plane (P1b),
[0079] - for the electrical insulation layer (12c) having a first overhanging length (L1c) with respect to the first orthogonal plane (P1c),
[0080] - for the electrical insulation layer (12d) having a first overhanging length (L1d) with respect to the first orthogonal plane (P1d),
[0081] - for the electrical insulation layer (12e) having a first overhanging length (L1e) with respect to the first orthogonal plane (P1e),
[0082] - for the electrical insulation layer (12f) having a first overhanging length (L1f) with respect to the first orthogonal plane (P1f),
[0083] - and so on.
[0084] Advantageously, the first overhanging length (L1i) is greater than forty times the diameter (D) of the wire. Preferably, the first overhanging length (L1i) is greater than seventy times the diameter (D) of the wire.
[0085] Each electrical insulation layer (12i) includes a second overhanging region that extends axially by a second overhanging length (L2i) beyond the second orthogonal plane (P2i) of the longer of two adjacent conductive layers (11i).
[0086] For example, with reference to Figure 4 , the electrical insulation layer (12a) includes a second overhanging region that extends axially by a second overhanging length (L2a) beyond the second orthogonal plane (P2a) of the longer of two conductive layers (11a, 11b). The same applies to:
[0087] - For the electrical insulation layer (12b) having a second overhang length (L2b) with respect to the second orthogonal plane (P2b),
[0088] - For the electrical insulation layer (12c) having a second overhang length (L2c) with respect to the second orthogonal plane (P2c),
[0089] - For the electrical insulation layer (12d) having a second overhang length (L2d) with respect to the second orthogonal plane (P2d),
[0090] - For the electrical insulation layer (12e) having a second overhang length (L2e) with respect to the second orthogonal plane (P2e),
[0091] - For the electrical insulation layer (12f) having a first overhang length (L2f) with respect to the first orthogonal plane (P2f),
[0092] - And so on.
[0093] Advantageously, the second overhang length (L2i) is greater than forty times the diameter (D) of the wire. Preferably, the second overhang length (L2i) is greater than seventy times the diameter (D) of the wire.
[0094] With reference to Figure 2 and Figures 5 to 9 , the power transformer is characterized in that the first overhang length (L1j) and / or the second overhang length (L2j) of at least one first electrical insulation layer (12j) is greater than the overhang length (L1k) and / or the second overhang length (L2k) of at least one other electrical insulation layer (12k).
[0095] In a manufacturing process based on cutting electrical insulation layers of the same initial size, it can be noted that the technical effect of the present invention is obtained without increasing additional costs and without increasing the electrical insulation layer material, and the best breakdown resistance performance is obtained.
[0096] The first overhang length (L1j) or the second overhang length (L2j) of at least one first electrical insulation layer (12j) is advantageously at least twenty times the diameter (D) of the wire (111) greater than the first overhang length (L1k) or correspondingly the second overhang length (L2k) of the second electrical insulation layer (12k), preferably at least fifty times the diameter (D) of the wire (111), and preferably at least one hundred times the diameter (D) of the wire (111).
[0097] Advantageously, the first overhang length (L1i) and the second overhang length (L2i) of each electrical insulation layer (12i) are forty to three hundred and twenty times the diameter (D) of the wire (111).
[0098] Each electrical insulation layer (12i) may include:
[0099] - either two long overhangs
[0100] - or two short overhangs
[0101] - or one long overhang and one short overhang.
[0102] "Short overhang" means that the overhang length (L1i, L2i) of the electrical insulation layer is forty to one hundred times the diameter (D) of the wire (111). The short overhangs can have different lengths, as shown in the exemplary embodiments of Figures 1 to 6 , Figure 8 and Figure 9 . In alternative embodiments, and as in the exemplary embodiments shown in Figure 7 , the short overhangs can all have the same length. For example, conventional overhangs can be kept as short overhangs and some overhangs can be extended to make them long overhangs. In other embodiments not shown, some short overhangs can have the same length while others do not.
[0103] "Long overhang" means that the overhang length (L1i, L2i) of the electrical insulation layer is one hundred twenty to three hundred twenty times the diameter (D) of the wire (111). The long overhangs can have different lengths, as shown in the exemplary embodiments of Figures 1 to 6 , Figure 8 and Figure 9 . In alternative embodiments not shown, the long overhangs can have the same length. In other embodiments not shown, some short overhangs can have the same length while others do not.
[0104] In some embodiments, the innermost electrical insulation layer (12a) of the coil (1) can have two short overhangs. In other embodiments, the innermost electrical insulation layer (12a) of the coil (1) can have two long overhangs. In still other embodiments, the innermost electrical insulation layer (12a) of the coil (1) can have both long and short overhangs.
[0105] In the first embodiment, the electrical insulation layer (12i) is divided into a short overhang group (122) and a long overhang group (121). In other words:
[0106] - the first overhang length (L1j) and the second overhang length (L2j) of the electrical insulation layer (12j) of the short overhang group (122) are forty to one hundred times the diameter (D) of the wire (111), and
[0107] - the first overhang length (L1k) and the second overhang length (L2k) of the electrical insulation layer (12k) of the long overhang group (121) are one hundred twenty to three hundred twenty times the diameter (D) of the wire (111).
[0108] Typically, the short overhang group (122) can consist of two to four short overhang subgroups of consecutive electrically insulating layers (12j). Additionally, the long overhang group (121) can consist of two to four long overhang subgroups of consecutive electrically insulating layers (12k). Thus, the insulating portion (12) is formed by the alternation between the short overhang subgroups and the long overhang subgroups.
[0109] In Figure 2 the exemplary embodiment shown, the short overhang group (122) consists of:
[0110] - three short overhang subgroups of three consecutive electrically insulating layers (12j), and
[0111] - one short overhang subgroup of two consecutive electrically insulating layers (12j).
[0112] The long overhang group (121) consists of three long overhang subgroups of three consecutive electrically insulating layers (12k).
[0113] In a second embodiment, the electrically insulating layer (12i) is divided into a group (123) having a first short overhang and a second long overhang and a group (124) having a first long overhang and a second short overhang. In other words:
[0114] - For the electrically insulating layer (12j) of the group (123) having a first short overhang and a second long overhang:
[0115] o The first overhang length (L1j) is forty to a hundred times the diameter (D) of the wire (111), and
[0116] o The second overhang length (L2j) is a hundred and twenty to three hundred and twenty times the diameter (D) of the wire (111);
[0117] - For the electrically insulating layer (12k) of the group (124) having a first long overhang and a second short overhang:
[0118] o The first overhang length (L1k) is a hundred and twenty to three hundred and twenty times the diameter (D) of the wire (111), and
[0119] o The second overhang length (L2k) is forty to a hundred times the diameter (D) of the wire (111).
[0120] Typically, the first short overhang and second long overhang group (123) consists of a first short overhang subgroup and a second long overhang subgroup of two to four consecutive electrically insulating layers (12j). Additionally, the first long overhang and second short overhang group (124) consists of a first long overhang and second short overhang subgroup of two to four consecutive electrically insulating layers (12k). Thus, the insulating portion (12) is formed by the alternation between the subgroup having a first short overhang and a second long overhang and the subgroup having a first long overhang and a second short overhang.
[0121] In Figure 5 the exemplary embodiment shown, the short overhangs and the second long overhangs group (123) consists of:
[0122] - three subgroups, each having short overhangs and second long overhangs of three consecutive electrically insulating layers (12i), and
[0123] - one subgroup having short overhangs and second long overhangs of two consecutive electrically insulating layers (12i).
[0124] The group (124) having the first long overhangs and the second short overhangs itself consists of three subgroups having the first long overhangs and the second short overhangs, each subgroup having three consecutive electrically insulating layers (12j).
[0125] In the third embodiment, the overhang lengths increase or decrease gradually.
[0126] For example, by successively selecting the electrically insulating layers radially from the inside to the outside, the first overhang length (L1j) of the electrically insulating layer (12j) increases relative to the first overhang length (L1k) of the previous electrically insulating layer (12k) until it reaches the maximum length or decreases until it reaches the corresponding minimum length, and then decreases until it reaches the minimum length or increases correspondingly until it reaches the corresponding maximum length.
[0127] Alternatively to or in combination with the foregoing paragraph, the second overhang length (L2j) of the electrically insulating layer (12j) increases relative to the second overhang length (L2k) of the previous electrically insulating layer (12k) until it reaches the maximum length, or decreases until it reaches the corresponding minimum length, and then decreases to the minimum length, or increases correspondingly to the corresponding maximum length.
[0128] Advantageously, the minimum length is forty to one hundred times the diameter of the wire. Also advantageously, the maximum length is one hundred twenty to three hundred twenty times the diameter of the wire.
[0129] Conveniently, as Figure 6 shown in the exemplary embodiment, the first overhang length (L1i) and / or the second overhang length (L2i) increase or decrease according to a sine function (S).
[0130] Another aspect of the invention relates to a power transformer. The power transformer can be a measuring transformer, intended to supply power to measuring devices, meters, relays and other similar devices. In particular, the transformer can be a voltage transformer. The transformer can also be a power transformer. The power transformer can be single-phase or three-phase.
[0131] The power transformer includes a housing. The housing is preferably metallic, but can also be made of any material considered suitable by those skilled in the art. The housing preferably has a cylindrical shape, but it can also have any shape considered suitable by those skilled in the art.
[0132] The power transformer further includes at least one coil (1) according to the present invention. The coil (1) is arranged inside the housing. When the power transformer is single-phase, the transformer includes a single coil (1) arranged inside the housing. When the power transformer is three-phase, the transformer includes three coils (1) arranged inside the housing.
[0133] The transformer further includes an electrically insulating fluid arranged inside the housing and surrounding the coil (1). The electrically insulating fluid can be, for example, an oil as described in the IEC 60296 standard, an insulating fluid as described in the IEC 60867 standard, sulfur hexafluoride (SF6), or any other electrically insulating fluid considered suitable by those skilled in the art. Preferably, in order to limit the pollution risk associated with possible leakage of the housing, the type of fluid used is oxygen, nitrogen, carbon dioxide, fluoronitrile, fluoroketone, fluoronitrile or a mixture of fluoroketone with oxygen or nitrogen or carbon dioxide, or a mixture of sulfur hexafluoride with a large amount of nitrogen, etc. In practice, the dielectric strength of the insulating fluid is greater than 2 kV / mm. The fluid can be arranged inside the housing under pressure. In particular, the fluid pressure can be from 3.5 bar rel to 6.3 bar rel.
Claims
1. A coil (1) for a power transformer, comprising: - A conductive part (11), which includes a plurality of conductive layers (11i), each of the conductive layers includes a wire (111), the wire is helically wound around an axis (A) and axially extends from a first plane (P1i) orthogonal to the axis to a second plane (P2i) orthogonal to the axis, and the conductive layers are arranged coaxially with each other, - An electrical insulation part (12), which includes a plurality of electrical insulation layers (12i), each of the electrical insulation layers is arranged between two of the conductive layers to insulate the two conductive layers from each other, the electrical insulation layer includes a first overhang area and a second overhang area, and the first overhang area and the second overhang area extend axially beyond the first plane (P1i) and correspondingly the second plane (P2i) of the longer conductive layer among the two conductive layers by a first overhang length (L1i) and correspondingly a second overhang length (L2i), characterized in that the first overhang length (L1j) and / or the second overhang length (L2j) of at least one first electrical insulation layer (12j) is greater than the first overhang length (L1k) and / or correspondingly the second overhang length (L2k) of at least one other electrical insulation layer (12k).
2. The coil according to claim 1, characterized in that the conductive layers at least partially overlap axially.
3. The coil according to claim 1 or 2, characterized in that the electrical insulation layer (12i) is generally cylindrical, and the electrical insulation layers are arranged coaxially with each other and at least partially overlap axially.
4. The coil according to any one of claims 1 to 3, characterized in that the electrical insulation layer extends axially through the first overhang area and the second overhang area.
5. The coil according to any one of claims 1 to 4, characterized in that: - The wire (111) of each conductive layer (11i) has a diameter (D), and - The first overhang length (L1j) or the second overhang length (L2j) of the at least one first electrical insulation layer (12j) is at least twenty times the diameter (D) of the wire greater than the first overhang length (L1k) or correspondingly the second overhang length (L2k) of the second electrical insulation layer (12k).
6. The coil according to any one of the foregoing claims, characterized in that: - The wire (111) of each conductive layer (11i) has a diameter (D), and - The first overhang length (L1i) and the second overhang length (L2i) of each electrical insulation layer (12i) are forty to three hundred and twenty times the diameter (D) of the wire.
7. The coil according to any one of the foregoing claims, characterized in that: - The wire (111) of each conductive layer (11i) has a diameter (D), and - The electrical insulation layer (12i) is divided into a short overhang group (122) and a long overhang group (121), - The first overhang length (L1j) and the second overhang length (L2j) of the electrical insulation layers (12j) in the short overhang group are forty to one hundred times the diameter (D) of the wire, - The first overhang length (L1k) and the second overhang length (L2k) of the electrical insulation layer (12k) of the long overhang group are 120 to 320 times the diameter (D) of the wire.
8. The coil according to claim 7, wherein: - The short overhang group (122) consists of two to four sub - groups of short overhangs of consecutive electrical insulation layers (12j), - The long overhang group (121) consists of two to four sub - groups of long overhangs of consecutive electrical insulation layers (12k), - The insulating part (12) is formed by the alternation between the short overhang sub - groups and the long overhang sub - groups.
9. The coil according to any one of claims 1 to 6, wherein: - The wire (111) of each conductive layer (11i) has a diameter (D), and - The electrical insulation layer (12i) is divided into a group (123) with a first short overhang and a second long overhang and a group (124) with a first long overhang and a second short overhang, - The first overhang length (L1j) of the electrical insulation layer (12j) of the group (123) with a first short overhang and a second long overhang, and the second overhang length (L2k) of the electrical insulation layer (12k) of the group (124) with a first long overhang and a second short overhang are 40 to 100 times the diameter (D) of the wire, - The second overhang length (L2j) of the electrical insulation layer (12j) of the group (123) with a first short overhang and a second long overhang, and the first overhang length (L1k) of the electrical insulation layer (12k) of the group (124) with a first long overhang and a second short overhang are 120 to 320 times the diameter (D) of the wire.
10. The coil according to claim 7, wherein: - The group (123) with a first short overhang and a second long overhang consists of sub - groups of a first short overhang and a second long overhang of two to four consecutive electrical insulation layers (12j), - The group (124) with a first long overhang and a second short overhang consists of sub - groups of a first long overhang and a second short overhang of two to four consecutive electrical insulation layers (12k), - The insulating part is formed by the alternation between the sub - groups of a first short overhang and a second long overhang and the sub - groups of a first long overhang and a second short overhang.
11. The coil according to any one of the preceding claims, wherein, by successively selecting the electrical insulation layers (12i) radially from the inside to the outside, the first overhang length (L1i) and / or the second overhang length (L2i) of the electrical insulation layer (L2i) increases relative to the first overhang length (L1j) and / or correspondingly the second overhang length (L2j) of the previous electrical insulation layer (12j) until reaching the maximum length or decreases until reaching the correspondingly minimum length, and then decreases until reaching the minimum length or correspondingly increases to reach the correspondingly maximum length.
12. The coil according to claim 11, wherein, The minimum length is 40 to 100 times the diameter of the wire, and the maximum length is 120 to 320 times the diameter of the wire.
13. The coil according to any one of claims 11 or 12, characterized in that, the first overhang length (L1i) and / or the second overhang length (L2i) increases or decreases according to a sine function (S).
14. A power transformer, comprising: - a housing; - at least one coil (1) arranged within the housing; and - an electrically insulating fluid, which is arranged within the housing and envelopes the at least one coil; characterized in that the at least one coil is the coil according to any one of the preceding claims.