220kV transformer with Z-shaped wiring low-voltage coil

Abstract

The utility model belongs to the technical field of manufacturing of power transformers, and relates to a low-voltage coil Z-type wiring 220kV transformer for a power station, which comprises an iron core and a clamping piece, a second low-voltage coil, a first low-voltage coil, a high-voltage coil and a voltage regulating coil are sequentially sleeved on the periphery of the iron core and the clamping piece from inside to outside, the first ends r ', y' and b 'of the first low-voltage coil are led out from the upper part, and the second low-voltage coil is led out from the lower part. The tail ends r 'k, y' k and b 'k are led out from the lower part; the first ends r, y and b of the low-voltage second coil are led out from the upper part, and the tail ends rk, yk and bk are led out from the lower part; rk and y'k are connected through a low-voltage lead cable, yk and b 'k are connected through a low-voltage lead cable, and bk and r' k are connected through a low-voltage lead cable; the r ', the y' and the b 'are connected through low-voltage lead cables and then led out to a low-voltage neutral point, and the r, the y and the b are led out to low-voltage phase lines through the low-voltage lead cables respectively. According to the utility model, a low-voltage coil radial distribution structure and Z-shaped wiring are adopted, and the manufacturability of an insulation structure and a lead structure is good.

Description

Technical Field

[0001] The utility model belongs to the technical field of power transformer manufacturing, and specifically relates to a 220kV transformer with a Z-type connection of a low-voltage coil for a power plant. Background Art

[0002] YN connection: YN connection is to connect the three ends of the three-phase coil together as the neutral point, and lead out the three ends as phase lines.

[0003] ZN connection (i.e. Z-type connection): ZN connection is that each phase winding is divided into two halves, the upper half of one phase winding and the lower half of the other phase winding are reversely connected in series to form a group, and then the starting ends of the lower half of the other phase winding are connected together as the neutral point, and the three starting ends of the upper half of one phase winding are led out as phase lines.

[0004] In the power system, the high-voltage coil of the main transformer usually adopts star connection, and the low-voltage coil adopts triangle connection, and the connection group is YNd11 ("star-delta" connection method). However, in some distribution networks, the high-voltage and low-voltage coils of the transformer adopt triangle connection, and the connection group is Dd0 ("delta-delta" connection method). Once a single-phase ground short-circuit fault occurs, its capacitive current to the ground may break through the coil insulation and cause a phase-to-phase short circuit, so a grounding point is required. Compared with the YN connection method, when a single-phase short-circuit fault occurs in a transformer using the ZN connection method, its zero-sequence magnetic flux cancels each other, which can effectively reduce the short-circuit current value, while reducing the short-circuit force on each coil, thereby improving the transformer's ability to resist short circuits.

[0005] The Z-type connection method is more complicated than the star connection and delta connection method. The Z-type connection transformer is divided into two types: axial distribution and radial distribution according to the relative position of the coil. Since the voltage of the current small grounding transformer is low (up to 35kV) and the capacity is small, the axial distribution structure of the coil is mostly adopted. Although the advantages of the axial distribution of the coil are better short-circuit resistance, good short-circuit impedance matching, and easy realization of high-voltage coils, bodies, and leads, if a high-voltage transformer of 220kV is to be realized, its capacity must also be greater than that of a conventional grounding transformer. In addition, considering the short-circuit impedance matching and the overall structural processability, the axial distribution structure of the coil is not well suitable for the 220kV transformer with Z-type connection. Utility Model Content

[0006] In order to solve the above technical problems, the utility model proposes a 220kV transformer with a low-voltage coil Z-type connection. The technical solution adopted by the utility model is as follows:

[0007] A 220kV transformer with a low-voltage coil Z-connection comprises an iron core and a clamp, wherein the outer periphery of the iron core and the clamp is sequentially mounted with a low-voltage second coil, a low-voltage first coil, a high-voltage coil and a voltage regulating coil from the inside to the outside, the first end r', y' and b' of the low-voltage first coil are led out from the top, and the tail ends r'k, y'k and b'k are led out from the bottom; the first end r, y and b of the low-voltage second coil are led out from the top, and the tail ends rk, yk and bk are led out from the bottom; rk and y'k are connected through a low-voltage lead cable, yk and b'k, and bk and r'k are connected through a low-voltage lead cable; r', y' and b' are connected by using a low-voltage lead cable and then led out to a low-voltage neutral point, and r, y and b are respectively led out to a low-voltage phase line by using a low-voltage lead cable.

[0008] Preferably, the clamping member includes a low-pressure upper clamping member, a low-pressure lower clamping member, a high-pressure upper clamping member and a high-pressure lower clamping member.

[0009] Preferably, a fixed steel plate is welded on the low-voltage upper clamp and the low-voltage lower clamp, a wire clamp has an opening, and an insulating screw and an insulating nut pass through the opening of the wire clamp to fix the wire clamp and the fixed steel plate, and two adjacent wire clamps are fixed to the low-voltage lead cable by insulating screws and insulating nuts.

[0010] Beneficial effects of the utility model:

[0011] The utility model innovatively adopts the low-voltage coil radial distribution structure and Z-type wiring, which has the following advantages: 1. The short-circuit impedance calculation value and the agreement value match well, and the impedance deviation is small; 2. The lightning resistance is good and the factory insulation strength test is passed in one time; 3. Under the three-phase unbalanced load, the neutral point offset is effectively reduced; 4. The insulation structure and the lead structure have good processability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the arrangement of coils of a low voltage Z-connection transformer according to an embodiment of the utility model;

[0013] Figure 2 A schematic diagram of high voltage leads of a low voltage Z-connection transformer according to an embodiment of the utility model;

[0014] Figure 3 A schematic diagram of low-voltage leads of a low-voltage Z-connection transformer according to an embodiment of the utility model;

[0015] Figure 4 It is a schematic diagram of the principle of a low voltage Z-connection transformer according to an embodiment of the utility model;

[0016] In the figure, 1 is the high-voltage coil, 2 is the low-voltage coil 1, 3 is the low-voltage coil 2, 4 is the voltage regulating coil, 5 is the iron core and clamps, 6 is the high-voltage phase line, 7 is the high-voltage neutral point, 8 is the low-voltage phase line, and 9 is the low-voltage neutral point. DETAILED DESCRIPTION

[0017] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings. The described embodiments are only part of the embodiments of the present utility model, rather than all of the embodiments.

[0018] like Figure 1 , Figure 2 , Figure 3 As shown, it is a coil arrangement diagram and high and low voltage lead diagram of the low-voltage Z-type connection transformer provided by an embodiment of the utility model. The low-voltage Z-type connection transformer includes an iron core and a clamp 5. The outer periphery of the iron core and the clamp 5 is sequentially mounted with a low-voltage second coil 3, a low-voltage first coil 2, a high-voltage coil 1 and a voltage regulating coil 4 from the inside to the outside. According to the capacity of the transformer and the direct resistance balance, a low-voltage lead cable with a suitable cross-section is selected. According to the electrical principle connection group diagram, the low-voltage second coil 3 and the low-voltage first coil 2 are connected using a low-voltage lead cable. The head r', y' and b' of the low-voltage first coil 2 are led out from the top, and the tail r'k, y'k and b'k are led out from the bottom; the head r, y and b of the low-voltage second coil 3 are led out from the top, and the tail rk, yk and bk are led out from the bottom. According to the winding connection diagram, rk and y'k are connected through a low-voltage lead cable, and yk and b'k as well as bk and r'k are connected using a low-voltage lead cable; r', y', and b' are connected using a low-voltage lead cable and then led out to a low-voltage neutral point 9, and r, y, and b are led out to a low-voltage phase line 8 using a low-voltage lead cable.

[0019] The upper outgoing line of the high-voltage coil 1 is the three-phase high-voltage phase line 6, and the lower outgoing line of the high-voltage coil 1 is led out to the high-voltage neutral point 7 through the on-load tap changer, so that the high-voltage coil realizes YN connection, the upper outgoing line of the low-voltage second coil is the low-voltage head end, and the lower outgoing line of the low-voltage second coil is connected to the lower outgoing line of the low-voltage first coil. The upper outgoing line of the three-phase low-voltage first coil is connected and then led out to the low-voltage neutral point 9, so that the low-voltage coil realizes ZN connection.

[0020] Figure 4 In the figure, R, Y and B are the outlets of the high-voltage coil 1, r, y and b are the head of the low-voltage second coil 3, rk, yk and bk are the tail of the low-voltage second coil 3, r', y' and b' are the head of the low-voltage first coil 2, r'k, y'k and b'k are the tail of the low-voltage first coil 2, O is the high-voltage neutral point 7, and o is the low-voltage neutral point 9.

[0021] In order to meet the insulation distance between the low-voltage lead cable and the box wall, coil and structural parts, etc., to improve the mechanical strength of the low-voltage lead cable and ensure the stability of the transportation process, the low-voltage lead cable needs to be clamped by a wire clamp, and the low-voltage upper clamp and the low-voltage lower clamp need to be welded to a fixed steel plate. The wire clamp is made of laminated wood, and a hole is opened in the wire clamp. It is connected to the fixed steel plate welded by the low-voltage upper clamp and the low-voltage lower clamp through an insulating screw and an insulating nut. Two adjacent wire clamps fix the low-voltage lead cable through insulating screws and insulating nuts.

[0022] According to the transformer capacity, rated voltage, and short-circuit impedance parameters, it is determined that the low-voltage amplitude distribution method is used to achieve low-voltage Z-shaped wiring. According to the coil arrangement and winding direction, the same-name end number of each coil is determined, and the high and low voltage coil outlets are correctly connected through the lead cable, and finally the transformer YNzn11 connection group is realized.

[0023] In the embodiments of the utility model, the technical features not described in detail are all existing technologies or conventional technical means and will not be described in detail here.

[0024] Finally, it should be noted that the above embodiments are only specific implementation methods of the present utility model, which are used to illustrate the technical solution of the present utility model, rather than to limit it, and the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any technician familiar with the technical field can modify the technical solution recorded in the above embodiments within the technical scope disclosed by the present utility model, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiment of the present utility model, and should be covered within the protection scope of the present utility model.

Claims

1. A 220kV transformer with a low-voltage coil Z-connection, comprising an iron core and a clamp, wherein the outer periphery of the iron core and the clamp is sequentially provided with a low-voltage second coil, a low-voltage first coil, a high-voltage coil and a voltage regulating coil from the inside to the outside, characterized in that: The first ends r', y' and b' of the low voltage coil 1 are led out from the top, and the tail ends r'k, y'k and b'k are led out from the bottom; the first ends r, y and b of the low voltage coil 2 are led out from the top, and the tail ends rk, yk and bk are led out from the bottom; rk and y'k are connected through a low voltage lead cable, and yk and b'k, as well as bk and r'k, are connected through a low voltage lead cable; Use a low-voltage lead cable to connect r', y', and b' and lead them out to the low-voltage neutral point. Use a low-voltage lead cable to lead r, y, and b to the low-voltage phase line respectively.

2. A 220kV transformer with a low-voltage coil Z-connection according to claim 1, characterized in that: The clamping pieces include a low-pressure upper clamping piece, a low-pressure lower clamping piece, a high-pressure upper clamping piece and a high-pressure lower clamping piece.

3. A 220kV transformer with a low-voltage coil Z-connection according to claim 2, characterized in that: A fixed steel plate is welded on the low-voltage upper clamp and the low-voltage lower clamp, a wire clamp has an opening, and an insulating screw and an insulating nut pass through the opening of the wire clamp to fix the wire clamp and the fixed steel plate, and two adjacent wire clamps are fixed to the low-voltage lead cable by the insulating screws and insulating nuts.

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