Three-phase split-type transformer body structure for + / -500kV offshore direct-current power transmission

Abstract

The utility model relates to a three-phase split type transformer body structure for + / -500kV offshore direct current transmission, which comprises an iron core arranged in an oil tank, and a first network side coil, a valve side coil, a second network side coil and a balance coil are sequentially sleeved on each phase core column of the iron core from inside to outside. The head end of each phase of first network side coil and the head end of each phase of second network side coil are connected with two parallel network side alternating current cables, the tail end of each phase of first network side coil and the tail end of each phase of second network side coil are converged and connected, the head end of each phase of valve side coil is connected with a corresponding valve side direct current cable, and the tail ends of each phase of valve side coil are converged and connected. And the balance coils of all phases are connected in sequence. According to the utility model, each phase of network side double-path incoming line is adopted, and each path of incoming line adopts a double-cable parallel connection mode to reduce the network side voltage of the transformer from 220kV to 66kV, so that the purpose that electric power generated by an offshore wind turbine is directly connected to an offshore platform through a 66KV three-phase cable is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of transformers, in particular to a three-phase split transformer body structure for ±500kV offshore direct current transmission. Background Art

[0002] Currently, flexible direct current (HVDC) transmission technology is becoming the primary method for delivering deep-sea wind resources. It can facilitate the integration of a high proportion of offshore wind power, and high-voltage, large-capacity, lightweight three-phase flexible direct current (HVDC) transformers are more suitable for large-capacity offshore converter platforms. However, existing offshore wind power flexible direct current (HVDC) transmission line transformers have a maximum valve-side voltage rating of ±400kV, which cannot meet the increasing requirements of transmission lines. Furthermore, the grid-side voltage of the transformer is generally 220kV, which typically needs to be stepped up at an offshore substation before being fed into the flexible HVDC transformer. Therefore, each wind farm requires a substation and three-phase cables to connect them. Utility Model Content

[0003] The purpose of the utility model is to provide a three-phase split transformer body structure for ±500kV offshore DC transmission, which adopts dual-line (double split) on the grid side of each phase. Each line adopts a dual cable in parallel to reduce the transformer grid side voltage of 220kV to 66kV, thereby achieving the purpose of directly connecting the power generated by offshore wind turbines to the offshore platform through 66kV three-phase cables.

[0004] The purpose of this utility model is achieved through the following technical solutions:

[0005] A three-phase split-type transformer body structure for ±500kV offshore direct current transmission includes an iron core disposed within an oil tank, wherein each phase core leg of the iron core is sequentially fitted with a first grid-side coil, a valve-side coil, a second grid-side coil, and a balancing coil from the inside out, wherein the head end of each phase first grid-side coil and the head end of each phase second grid-side coil are connected to two parallel grid-side AC cables, the end of each phase first grid-side coil and the end of each phase second grid-side coil are merged and connected, the head end of each phase valve-side coil is respectively connected to the corresponding valve-side DC cable, the end of each phase valve-side coil is merged and connected, and the balancing coils of each phase are sequentially connected.

[0006] The oil tank is provided with a grid-side outlet box, a first grid-side neutral point bushing, and a second grid-side neutral point bushing. A grid-side bushing is provided in the grid-side outlet box, and the head end of the first grid-side coil of each phase and the head end of the second grid-side coil of each phase are respectively connected to two parallel grid-side AC cables introduced into the grid-side outlet box through the grid-side bushings in the corresponding grid-side outlet box. The ends of the first grid-side coils of each phase are merged and connected and then led out through the first grid-side neutral point bushing. The ends of the second grid-side coils of each phase are merged and connected and then led out through the second grid-side neutral point bushing.

[0007] The first grid-side neutral point bushing and the second grid-side neutral point bushing are respectively arranged at two ends of the oil tank, and each grid-side outlet box is arranged between the first grid-side neutral point bushing and the second grid-side neutral point bushing.

[0008] The oil tank is provided with a valve side outlet box and a valve side neutral point bushing, wherein the valve side bushing is provided in the valve side outlet box, and the head end of the valve side coil of each phase is connected to the valve side DC cable introduced into the valve side outlet box through the valve side bushing in the corresponding valve side outlet box, and the ends of the valve side coils of each phase are converged and connected and led out by the valve side neutral point bushing.

[0009] The oil tank is provided with a balancing sleeve, and the balancing coils of each phase are connected end to end in sequence, and the head end of the A-phase balancing coil and the tail end of the C-phase balancing coil are respectively led out from the corresponding balancing sleeves on the oil tank.

[0010] The balance coil is provided with a balance coil electrostatic plate and a balance coil angle ring, wherein the balance coil electrostatic plate is provided at the end of the balance coil, and the balance coil angle ring is provided above the balance coil electrostatic plate.

[0011] The iron core is a three-phase five-column structure, wherein the three core columns in the middle of the iron core are covered with coil assemblies, and the side columns on both sides of the iron core are not covered with coils.

[0012] The advantages and positive effects of this utility model are:

[0013] 1. The utility model adopts dual-line (double-split) input on each phase grid side, and each input line adopts dual cables in parallel to reduce the transformer grid-side voltage of 220kV to 66kV, thereby achieving the purpose of directly connecting the power generated by the offshore wind turbine to the offshore platform via 66kV three-phase cable. This direct connection method eliminates the original wind farm booster station configuration and does not require three-phase cable, which can save a large amount of offshore AC cable. At the same time, while fully considering the insulation characteristics of the transformer, the utility model can also increase the valve side voltage to ±500kV.

[0014] 2. In order to ensure that the full-through impedance between the valve-side coil and the first grid-side coil, the half-through impedance between the valve-side coil and the second grid-side coil, and the split impedance between the first grid-side coil and the second grid-side coil are reasonably matched and meet the requirements of the splitting coefficient, the utility model splits the grid-side winding coil into the first grid-side coil and the second grid-side coil in the radial direction, and adds a balancing coil to eliminate the influence of high-order harmonics, thereby forming an arrangement structure of "first grid-side coil, valve-side coil, second grid-side coil, and balancing coil" from the inside to the outside. Compared with the existing technology, the utility model does not have a tap changer and does not set a voltage regulating coil, which further simplifies the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is a schematic diagram of the structure of the utility model.

[0016] Figure 2 for Figure 1 Schematic diagram of the connection relationship of the balance coils of each phase,

[0017] Figure 3 for Figure 1 A magnified diagram of the arrangement of the middle balance coil, valve side coil, and second network side coil.

[0018] Figure 4 for Figure 1 Schematic diagram of the connection relationship of the first grid-side coil of each phase,

[0019] Figure 5 for Figure 1 Schematic diagram of the connection relationship of the second grid-side coils of each phase,

[0020] Figure 6 for Figure 1 Schematic diagram of the connection relationship of the valve side coils of each phase,

[0021] Figure 7 This is a top view of the transformer structure using the utility model.

[0022] Figure 8 for Figure 7 The enlarged view of point A in the figure,

[0023] Figure 9 for Figure 8 The enlarged view of point B in the figure is as follows:

[0024] Figure 10 for Figure 7 In the I-direction view,

[0025] Figure 11 for Figure 10 Schematic diagram of the structure of the middle valve outlet box,

[0026] Figure 12 for Figure 7 Top view of the fuel tank.

[0027] Figure 13 This is a schematic diagram of the two-way split wiring principle of the utility model.

[0028] Among them, 1 is the first grid-side coil, 2 is the valve-side coil, 3 is the second grid-side coil, 4 is the balancing coil, 5 is the grid-side bushing, 6 is the grid-side AC cable, 7 is the valve-side bushing, 8 is the valve-side DC cable, 9 is the oil tank, 10 is the oil tank magnetic shield, 11 is the iron core, 1101 is the core column, 1102 is the side column, 12 is the balancing coil electrostatic plate, 13 is the balancing coil angle ring, 14 is the balancing bushing, 15 is the valve-side neutral point bushing, 1601 is the first grid-side neutral point bushing, 1602 is the second grid-side neutral point bushing, 17 is the water cooler, 18 is the oil storage cabinet, 19 is the grid-side outlet box, 20 is the valve-side outlet box, 21 is the control cabinet, and 22 is the oil drainage system. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] like Figures 1 to 13 As shown, the utility model includes an iron core 11 arranged in the oil tank 9, and as shown in FIG. Figure 1 As shown, each phase core 1101 of the core 11 is sequentially provided with a first grid side coil 1, a valve side coil 2, a second grid side coil 3 and a balance coil 4 from the inside to the outside, wherein Figures 4-5 As shown, the head end of each phase first grid-side coil 1 and the head end of each phase second grid-side coil 3 are connected to two parallel grid-side AC cables 6, and the end of each phase first grid-side coil 1 and the end of each phase second grid-side coil 3 are connected together, as shown in FIG. Figure 6 As shown, the head end of each phase valve side coil 2 is connected to the corresponding valve side DC cable 8, and the end of each phase valve side coil 2 is connected together. Figure 2 As shown, the balancing coils 4 of each phase are connected in sequence.

[0031] like Figure 13 As shown, first, in order to reduce the grid-side voltage of the transformer to 66kV, the present invention adopts a two-way line-in method, that is, the grid-side winding coil is split into a first grid-side coil 1 and a second grid-side coil 3. Secondly, in order to ensure that the full-through impedance between the valve-side coil 2 and the first grid-side coil 1, the half-through impedance between the valve-side coil 2 and the second grid-side coil 3, and the split impedance matching between the first grid-side coil 1 and the second grid-side coil 3 are reasonable and meet the requirements of the splitting coefficient, the present invention splits the grid-side winding coil into a first grid-side coil 1 and a second grid-side coil 3 in the radial direction, and arranges the first grid-side coil 1, the valve-side coil 2 and the second grid-side coil 3 in order from the inside to the outside. Thirdly, in order to eliminate the influence of high-order harmonics, the present invention adds a balancing coil 4. At the same time, by checking the impedance of the balancing coil 4 to the grid-side and valve-side coils to meet the short-circuit capacity requirements between the various coils of the transformer, the following is formed. Figure 1The arrangement order of "first grid-side coil 1, valve-side coil 2, second grid-side coil 3, and balancing coil 4" from inside to outside is shown. Compared with the prior art, the present invention does not have a tap changer and a voltage regulating coil. At the same time, since the coil voltage of the present invention is ±500kV, considering the influence of the voltage transmitted through the valve-side coil 2 on the balancing coil 4, as shown in FIG. Figure 3 As shown, the present invention increases the distance X between the second grid-side coil 3 and the balance coil 4, and adds a balance coil electrostatic plate 12 and a balance coil angle ring 13 to the balance coil 4 for protection, wherein the balance coil electrostatic plate 12 is arranged at the end of the balance coil 4, and the balance coil angle ring 13 is arranged on the upper side of the balance coil electrostatic plate 12.

[0032] like Figures 7-11 As shown, the oil tank 9 is provided with a grid side outlet box 19, a first grid side neutral point bushing 1601 and a second grid side neutral point bushing 1602, wherein Figures 4-5 and Figures 9-10 As shown, a grid-side bushing 5 is provided in the grid-side outlet box 19, and the head end of the first grid-side coil 1 of each phase and the head end of the second grid-side coil 3 of each phase are connected to two parallel grid-side AC cables 6 introduced into the grid-side outlet box 19 through the grid-side bushing 5 in the corresponding grid-side outlet box 19, and as shown Figures 4-5 and Figures 7-8 As shown, the ends of the first grid-side coils 1 of each phase are connected together and then led out from the first grid-side neutral point bushing 1601 , and the ends of the second grid-side coils 3 of each phase are connected together and then led out from the second grid-side neutral point bushing 1602 .

[0033] like Figure 7 As shown, the first grid-side neutral point bushing 1601 and the second grid-side neutral point bushing 1602 are respectively arranged at both ends of the oil tank 9, and each grid-side outlet box 19 is arranged between the first grid-side neutral point bushing 1601 and the second grid-side neutral point bushing 1602.

[0034] like Figures 7-11 As shown, the oil tank 9 is provided with a valve side outlet box 20 and a valve side neutral point bushing 15, wherein Figure 6 and Figures 10-11 As shown, the valve side outlet box 20 is provided with a valve side bushing 7, and the head end of each phase valve side coil 2 is connected to the valve side DC cable 8 introduced into the valve side outlet box 20 through the valve side bushing 7 in the corresponding valve side outlet box 20. Figure 6 and Figure 7 As shown, the ends of the valve-side coils 2 of each phase are connected together and led out through the valve-side neutral point bushing 15 .

[0035] like Figure 7As shown, a water cooler 17 and an oil drain system 22 are provided on one side of the oil tank 9, and the valve side neutral point sleeve 15 is provided on the side of the oil tank 9 close to the water cooler 17. The water cooler 17 and the oil drain system 22 are well known in the art.

[0036] like Figures 7-11 As shown, the oil tank 9 is provided with a balancing sleeve 14, and as shown Figure 2 As shown, in this embodiment, the B-phase balancing coil 402 is wound in a left-hand direction, and the A-phase balancing coil 401 and the C-phase balancing coil 403 are wound in a right-hand direction, wherein the end Wx of the A-phase balancing coil 401 is connected to the beginning Wb of the B-phase balancing coil 402, and the end Wy of the B-phase balancing coil 402 is connected to the beginning Wc of the C-phase balancing coil 403, and the beginning Wa of the A-phase balancing coil 401 and the end Wz of the C-phase balancing coil 403 are respectively led out from the corresponding balancing sleeves 14 on the oil tank 9.

[0037] like Figure 7 As shown, the balancing bushing 14 is provided on the side of the oil tank 9 away from the water cooler 17 , and each valve-side outlet box 20 is provided between the balancing bushing 14 and the valve-side neutral point bushing 15 .

[0038] like Figure 4 As shown, in this embodiment, the head end A1 of the first grid-side coil 101 of phase A is connected to the grid-side AC cables A11 and A12 in parallel, the head end B1 of the first grid-side coil 102 of phase B is connected to the grid-side AC cables B11 and B12 in parallel, and the head end C1 of the first grid-side coil 103 of phase C is connected to the grid-side AC cables C11 and C12 in parallel. The end X1 of the first grid-side coil 101 of phase A, the end Y1 of the first grid-side coil 102 of phase B, and the end Z1 of the first grid-side coil 103 of phase C are connected to the neutral point O1, and as shown in FIG. Figure 8 As shown, the cable drawn from the neutral point 01 is drawn out through the first network side neutral point bushing 1601. Figure 5 As shown, the head end A2 of the second grid-side coil 301 of phase A is connected to the parallel grid-side AC cables A21 and A22, the head end B2 of the second grid-side coil 302 of phase B is connected to the parallel grid-side AC cables B21 and B22, and the head end C2 of the second grid-side coil 303 of phase C is connected to the parallel grid-side AC cables C21 and C22. The end X2 of the second grid-side coil 301 of phase A, the end Y2 of the second grid-side coil 302 of phase B, and the end Z2 of the second grid-side coil 303 of phase C are connected to the neutral point O2, and as shown Figure 8 As shown, the cable led out from the neutral point 02 is led out through the second grid-side neutral point sleeve 1602.

[0039] like Figure 6As shown, the first end a of the A-phase valve side coil 201, the first end b of the B-phase valve side coil 202, and the first end c of the C-phase valve side coil 203 are respectively connected to the corresponding valve side DC cables 8, and the end x of the A-phase valve side coil 201, the end y of the B-phase valve side coil 202, and the end z of the C-phase valve side coil 203 are connected to the neutral point O, and as shown Figure 7 As shown, the cable led out from the neutral point O is led out through the valve-side neutral point bushing 15 .

[0040] like Figure 12 As shown, the oil tank 9 is provided with an arcuate segment on its wall, and a magnetic shield 10 is provided on this arcuate segment. This magnetic shield 10 is well known in the art. The present invention utilizes an arcuate segment in the area closest to the centerline of the device body and the oil tank 9 wall. Based on the distribution of the leakage magnetic field, the magnetic shield 10 is welded to the arcuate segment. This minimizes the installation size and overall weight while ensuring reliable insulation and mechanical structures.

[0041] like Figure 1 As shown, the iron core 11 is a three-phase five-column structure, wherein the three central core columns 1101 are provided with coils, and the side columns 1102 on both sides serve as magnetic flux circuits and are not provided with coils.

[0042] like Figure 7 and Figure 10 As shown, an oil storage cabinet 18 is provided on the upper side of the oil tank 9, and the oil storage cabinet 18 is a well-known technology in the art.

[0043] In addition, due to insufficient space on the offshore platform, the utility model cancels the 500kV test bushing, and the valve side center point withstand voltage test is carried out through the on-site neutral point GIS test bushing (valve side neutral point bushing 15). In order to facilitate the test and reduce the total working time, test bushings are installed at the grid side head end (grid side bushing 5) and the valve side center point (valve side neutral point bushing 15). In this way, the three-phase transformer can be subjected to partial discharge and withstand voltage tests continuously at one time.

[0044] The working principle of this utility model is:

[0045] like Figure 13As shown, in order to reduce the grid-side voltage of the transformer to 66 kV, the present invention adopts a two-way line-in method, that is, the grid-side winding coil is split into a first grid-side coil 1 and a second grid-side coil 3. At the same time, in order to ensure that the full-through impedance between the valve-side coil 2 and the first grid-side coil 1, the half-through impedance between the valve-side coil 2 and the second grid-side coil 3, and the split impedance matching between the first grid-side coil 1 and the second grid-side coil 3 are reasonable and meet the requirements of the splitting coefficient, the present invention splits the grid-side winding coil in the radial direction into a first grid-side coil 1 and a second grid-side coil 3. The transformer connection group of the present invention is YNYNyn0+d, and in order to eliminate the influence of high-order harmonics, a balancing coil 4 is added. The present invention does not have a tap switch and a voltage regulating coil, and the power generated by the offshore wind turbine is directly connected to the offshore platform through a 66 kV three-phase cable, which eliminates the original wind farm booster station configuration and does not require a three-phase cable. This direct connection method can save a large amount of offshore AC cables. At the same time, taking full account of the insulation characteristics of the transformer, the present invention can also increase the valve-side voltage to ±500 kV.

[0046] In addition, Figures 7-11 As shown, the utility model is provided with a grid side outlet box 19, a first grid side neutral point bushing 1601, a second grid side neutral point bushing 1602, a valve side outlet box 20, a valve side neutral point bushing 15, a balance bushing 14 and other structures on the oil tank 9 to realize the lead-out of the head end and the end end of each coil, and considering the problem of insufficient space on the offshore platform, the utility model cancels the 500kV test bushing, and the valve side center point withstand voltage test can be tested by the on-site neutral point GIS test bushing (valve side neutral point bushing 15), and in order to test In order to facilitate and reduce the total working time, test bushings are all installed at the grid side head end (grid side bushing 5) and the valve side center point (valve side neutral point bushing 15), so that the three-phase transformer can be continuously subjected to partial discharge and withstand voltage tests at one time. At the same time, the utility model adopts an arc-shaped segment tank wall at the place where the center line of the device body is closest to the tank wall of the oil tank 9, and welds a magnetic shield 10 on the arc-shaped segment tank wall according to the distribution of the leakage magnetic field. In this way, while ensuring the reliability of the product insulation structure and mechanical structure, the installation size is minimized and the overall weight is reduced.

Claims

1. A three-phase split transformer body structure for ±500kV offshore DC transmission, characterized by: The invention comprises an iron core (11) arranged in an oil tank (9), and each phase core column (1101) of the iron core (11) is sequentially provided with a first grid side coil (1), a valve side coil (2), a second grid side coil (3) and a balance coil (4) from the inside to the outside, wherein the head end of each phase first grid side coil (1) and the head end of each phase second grid side coil (3) are connected to two parallel grid side AC cables (6), the end of each phase first grid side coil (1) and the end of each phase second grid side coil (3) are merged and connected, the head end of each phase valve side coil (2) is respectively connected to the corresponding valve side DC cable (8), the end of each phase valve side coil (2) is merged and connected, and the balance coils (4) of each phase are sequentially connected.

2. The ±500kV three-phase split transformer body structure for offshore DC transmission according to claim 1 is characterized in that: The oil tank (9) is provided with a grid-side outlet box (19), a first grid-side neutral point bushing (1601), and a second grid-side neutral point bushing (1602). A grid-side bushing (5) is provided in the grid-side outlet box (19), and the head end of each phase first grid-side coil (1) and the head end of each phase second grid-side coil (3) are respectively connected to two parallel grid-side AC cables (6) introduced into the grid-side outlet box (19) through the grid-side bushing (5) in the corresponding grid-side outlet box (19). The ends of the first grid-side coils (1) of each phase are connected and then led out from the first grid-side neutral point bushing (1601), and the ends of the second grid-side coils (3) of each phase are connected and then led out from the second grid-side neutral point bushing (1602).

3. The ±500kV offshore DC transmission three-phase split transformer body structure according to claim 2 is characterized in that: The first grid-side neutral point bushing (1601) and the second grid-side neutral point bushing (1602) are respectively arranged at both ends of the oil tank (9), and each grid-side outlet box (19) is arranged between the first grid-side neutral point bushing (1601) and the second grid-side neutral point bushing (1602).

4. The ±500kV three-phase split transformer body structure for offshore DC transmission according to claim 1 is characterized in that: The oil tank (9) is provided with a valve side outlet box (20) and a valve side neutral point bushing (15), wherein a valve side bushing (7) is provided in the valve side outlet box (20), and the head end of each phase valve side coil (2) is connected to the valve side DC cable (8) introduced into the valve side outlet box (20) through the valve side bushing (7) in the corresponding valve side outlet box (20), and the ends of each phase valve side coil (2) are connected and led out by the valve side neutral point bushing (15).

5. The ±500kV three-phase split transformer body structure for offshore DC transmission according to claim 1 is characterized in that: The oil tank (9) is provided with a balancing sleeve (14), and the balancing coils of each phase are connected end to end in sequence, and the head end of the A-phase balancing coil (401) and the tail end of the C-phase balancing coil (403) are respectively led out from the corresponding balancing sleeve (14) on the oil tank (9).

6. The ±500kV three-phase split transformer body structure for offshore DC transmission according to claim 1 is characterized in that: The balance coil (4) is provided with a balance coil electrostatic plate (12) and a balance coil angle ring (13), wherein the balance coil electrostatic plate (12) is provided at the end of the balance coil (4), and the balance coil angle ring (13) is provided on the upper side of the balance coil electrostatic plate (12).

7. The ±500 kV three-phase split transformer body structure for offshore DC transmission according to claim 1 is characterized in that: The iron core (11) is a three-phase five-column structure, wherein the three core columns (1101) in the middle of the iron core (11) are covered with coil assemblies, and the side columns (1102) on both sides of the iron core (11) are not covered with coils.

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