Neutral point direct current magnetic bias suppression system shared by multiple transformers

Abstract

The utility model discloses a multi-transformer shared neutral point direct-current magnetic bias suppression system, which comprises a plurality of main transformers, and neutral points of the main transformers are mutually connected and jointly connected to the same direct-current magnetic bias suppression device. A second isolating switch is arranged between the neutral point and the direct-current magnetic bias suppression device, and the second isolating switch is connected with the neutral point in parallel and is connected with the direct-current magnetic bias suppression device in series; a first isolating switch, an air gap, a current transformer and a lightning arrester are arranged between the second isolating switch and the main transformer; the air gap and the current transformer are connected in series and are jointly connected with the first isolating switch and the lightning arrester in parallel, and the first isolating switch, the air gap and the lightning arrester are jointly connected with the neutral point and the second isolating switch. The utility model solves the problem that the direct-current magnetic bias current of the neutral point of the transformer exceeds the standard, can restrain the direct-current magnetic bias current, protects the normal operation of the transformer and a power system, and has the advantage of low cost.

Description

Technical Field

[0001] This utility model relates to the field of power system technology, specifically to a DC bias suppression system for multiple transformers sharing a neutral point. Background Technology

[0002] A series of high-voltage projects have been completed. When a DC project operates in monopolar mode, a large DC current flows into the ground through the grounding electrode, causing changes in the grounding electrode potential of surrounding substations, thus creating a potential difference. The DC current flows from the transmission line through the ground to the transformer neutral point, causing a DC component in the transformer and resulting in DC bias magnetization.

[0003] Exceeding the transformer's tolerance range with DC bias current can cause a rapid saturation of the transformer core's magnetic flux, increasing magnetic flux leakage, core losses, and copper losses. This can lead to overheating, insulation damage, reduced transformer lifespan, and even transformer failure. Simultaneously, DC bias current can severely distort the excitation current, generating numerous harmonics, affecting power quality, increasing reactive power losses in the power system, and resulting in enhanced vibration and significantly increased noise during transformer operation.

[0004] Therefore, it is necessary to address the issue of excessive DC bias current in transformers and resolve its impact on transformers and power systems. Utility Model Content

[0005] To overcome the shortcomings of the above-mentioned technologies, the purpose of this utility model is to provide a DC bias suppression system for multiple transformers sharing a neutral point, which solves the problem of excessive DC bias current, suppresses DC bias current, protects the normal operation of transformers and power systems, and has the advantage of low cost.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] A multi-transformer shared neutral point DC bias suppression system is characterized by the following: it includes multiple main transformers, whose neutral points are interconnected and connected to a single DC bias suppression device; the neutral point is the neutral point of either the high-voltage winding or the low-voltage winding of the main transformer; a second disconnecting switch is provided between the neutral point and the DC bias suppression device, the second disconnecting switch being connected in parallel with the neutral point and in series with the DC bias suppression device; a first disconnecting switch, an air gap, a current transformer, and a surge arrester are provided between the second disconnecting switch and the main transformer, the air gap and the current transformer being connected in series and connected in parallel with the first disconnecting switch and the surge arrester, and the first disconnecting switch, the air gap, and the surge arrester are all connected to the neutral point and the second disconnecting switch. This wiring scheme allows the transformer neutral point to operate in three states: ungrounded, directly grounded, or grounded through a DC blocking device, and enables switching between these three states.

[0008] As a preferred embodiment, the first disconnecting switch or the neutral point of the main transformer is connected to the second disconnecting switch via an overhead flexible conductor. Connecting the first and second disconnecting switches and the transformer neutral point together using an overhead flexible conductor offers advantages such as convenient wiring, high safety, and ease of maintenance. Only one additional second disconnecting switch is needed per main transformer to achieve a multi-transformer shared neutral point DC bias suppression system wiring system, offering advantages such as cost savings, simple wiring, and convenient operation.

[0009] As a preferred embodiment, the stationary contact of the second disconnecting switch is located on the neutral point side of the main transformer, and the moving contact is located on the side where the DC bias suppression device is located. The transformer neutral point is the energized side, and the side where the DC bias suppression device is located is the grounded side. Placing the moving contact on the grounded side ensures that the potential of the moving contact is ground potential when it operates, which can effectively improve the safety of the closing / opening operation of the second disconnecting switch.

[0010] Furthermore, the second disconnecting switch is connected to the high-voltage side of the DC bias suppression device, and the low-voltage side of the DC bias suppression device is grounded. By connecting the second disconnecting switch to the high-voltage side of the DC bias suppression device, the DC bias current on the transformer can be effectively introduced into the DC bias suppression device for suppression.

[0011] As a preferred embodiment, the second disconnecting switch is connected to the DC bias suppression device by a power cable.

[0012] As a preferred embodiment, the DC bias suppression device can be a resistive DC bias suppression device, a capacitive DC bias suppression device, or other DC bias suppression devices; when it is a resistive DC bias suppression device, its resistance can be adjusted. By setting an adjustable resistor, the DC bias current on the transformer can be suppressed by adjusting the resistance value, so as to ensure that the DC current flowing through the transformer neutral point is within the transformer's tolerance range, thereby ensuring the normal operation of the transformer and the power system.

[0013] Furthermore, the resistance of the resistive DC bias suppression device can be adjusted within a range of 0 to 5 Ω.

[0014] As a preferred option, the second disconnecting switch is installed on the equipment bracket at a height of not less than 2.5 meters. According to the requirements for outdoor power distribution equipment layout, the lowest point of the insulation of outdoor equipment should be at least 2.5 meters above the ground; otherwise, a fixed barrier should be installed.

[0015] As a preferred embodiment, the DC bias suppression device is mounted on the equipment base.

[0016] Furthermore, the foundation height of the equipment is 0.2 to 0.5 meters. This is based on the installation requirements and maintenance requirements of the DC bias magnetizer foundation, which are set between 0.2 and 0.5 meters.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] This utility model provides a DC bias suppression system for a shared neutral point of multiple transformers, which achieves the effect of controlling DC bias of multiple transformers, reduces the DC current flowing through the neutral point of the transformer to a range that the transformer can withstand, protects the normal operation of the transformer and the power system, and has the advantages of low cost and simple operation. Attached Figure Description

[0019] Figure 1 This is a connection diagram of a multi-transformer shared neutral point DC bias suppression system in a specific implementation embodiment;

[0020] Figure 2 for Figure 1 Installation diagram of a DC bias suppression system for multiple transformers sharing a neutral point;

[0021] Figure 3 This is a connection diagram of another multi-transformer shared neutral point DC bias suppression system in a specific implementation;

[0022] In the diagram: 100, main transformer; 101, first disconnecting switch; 102, air gap; 103, surge arrester; 104, second disconnecting switch; 105, flexible conductor; 106, power cable; 107, DC bias suppression device; 108, current transformer. Detailed Implementation

[0023] To better explain this utility model, the main contents of this utility model are further illustrated below with reference to the accompanying drawings and specific embodiments, but the contents of this utility model are not limited to the following embodiments.

[0024] like Figure 1 As shown, this utility model discloses a multi-transformer shared neutral point DC bias suppression system, comprising two main transformers 100, namely, main transformer #1 and main transformer #2. The neutral points of the two main transformers 100 are interconnected and jointly connected to the same DC bias suppression device 107; the neutral point is the neutral point of the 220kV side high-voltage winding of the main transformer 100; a second disconnecting switch 104 is provided between the neutral point and the DC bias suppression device 107, the second disconnecting switch 104 is connected in parallel with the neutral point and in series with the DC bias suppression device 107; a first disconnecting switch 101, an air gap 102, a current transformer 108, and a surge arrester 103 are provided between the second disconnecting switch 104 and the main transformer 100, the air gap 102 and the current transformer 108 are connected in series and jointly connected in parallel with the first disconnecting switch 101 and the surge arrester 103, and the first disconnecting switch 101, the air gap 102, and the surge arrester 103 are jointly connected to the neutral point and the second disconnecting switch 104. The first disconnecting switch 101, surge arrester 103, and current transformer 108 are all grounded.

[0025] like Figure 2 As shown, the second disconnecting switch 104, the first disconnecting switch 101, and the neutral point of the main transformer 100 are connected in sequence by an overhead flexible conductor 105.

[0026] The stationary contact of the second disconnecting switch 104 is located on the neutral point side of the main transformer 100, and the moving contact is located on the side where the DC bias suppression device 107 is located.

[0027] The second disconnecting switch 104 is connected to the high-voltage side of the DC bias suppression device 107, and the low-voltage side of the DC bias suppression device 107 is grounded.

[0028] The second disconnecting switch 104 is connected to the DC bias suppression device 107 by a power cable 106.

[0029] The DC bias suppression device 107 is a resistive DC bias suppression device with adjustable resistance ranging from 0 to 5Ω.

[0030] like Figure 2 As shown, the second disconnector 104 is mounted on an equipment bracket at a height of 3.15 meters. The first disconnector 101, air gap 102, current transformer 108, and surge arrester 103 connected to each main transformer 100 are all mounted on the same equipment bracket at a height of 3 meters. The brackets for the second disconnector 104 and the first disconnector 101 are placed vertically parallel to each other on the ground, with a 3-meter gap between the two brackets.

[0031] The DC bias suppression device 107 is arranged in a suitable open space in the station area; the DC bias suppression device 107 is installed on the equipment foundation, and the equipment foundation height is 0.3 meters.

[0032] The first disconnecting switch 101 and the second disconnecting switch 104 are model GW13-126W / 1250.

[0033] The model of the flexible conductor 105 is steel-cored aluminum stranded wire LGJ-400 / 35.

[0034] The model of power cable 106 is ZRB-YJV62-26 / 35-1×300.

[0035] Table 1: Status of disconnecting switches under different operating conditions

[0036]

[0037] The above wiring scheme can meet the different grounding methods of the neutral points of different main transformers in the station. Under the operating conditions of different grounding requirements of the neutral points of the main transformers, the opening and closing states of the first disconnecting switch 101 and the second disconnecting switch 104 of different main transformers are shown in Table 1. In Table 1, the DC blocking device is the DC bias suppression device 107.

[0038] In another specific implementation, such as Figure 3 As shown, there are three main transformers 100, namely main transformer #1, main transformer #2, and main transformer #3. The other parts are the same as above, so they will not be described in detail here.

[0039] The wiring scheme of the multi-transformer shared neutral point DC bias suppression system in this utility model connects the neutral points of multiple transformers to the DC bias suppression device through disconnecting switches. This can simultaneously meet the following requirements: 1) reduce the DC current flowing through the neutral point of the transformer to within the transformer's tolerance range, protecting the normal operation of the transformer and the power system; 2) the DC bias control of multiple transformers can be achieved by simply setting up cables, disconnecting switches and DC bias suppression devices, effectively reducing the cost of controlling excessive DC current at the transformer neutral point.

[0040] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. A multi-transformer common neutral DC bias mitigation system, comprising: The application relates to a power supply system for a plurality of main transformers (100), wherein the neutral points of the main transformers (100) are connected to each other and to a same DC bias suppression device (107); the neutral points are neutral points of high-voltage windings or low-voltage windings of the main transformers (100); a second disconnecting switch (104) is arranged between the neutral points and the DC bias suppression device (107), and is connected in parallel with the neutral points and in series with the DC bias suppression device (107); a first disconnecting switch (101), an air gap (102), a current transformer (108) and a surge arrester (103) are arranged between the second disconnecting switch (104) and the main transformers (100), the air gap (102) and the current transformer (108) are connected in series and are connected in parallel between the first disconnecting switch (101) and the surge arrester (103), and the first disconnecting switch (101), the air gap (102) and the surge arrester (103) are connected to the neutral points and the second disconnecting switch (104).

2. The multi-transform common neutral DC biasing suppression system of claim 1, wherein: The first disconnecting switch (101) or the neutral points of the main transformers (100) are connected to the second disconnecting switch (104) through an overhead flexible conductor (105).

3. The multi-transform common neutral DC biasing suppression system of claim 1, wherein: The static contact of the second disconnecting switch (104) is arranged on the side of the neutral points of the main transformers (100), and the dynamic contact is arranged on the side of the DC bias suppression device (107).

4. The multi-transform common neutral DC biasing suppression system of claim 1, wherein: The second disconnecting switch (104) is connected to the high-voltage side of the DC bias suppression device (107), and the low-voltage side of the DC bias suppression device (107) is grounded.

5. The multi-transform common neutral DC bias suppression system of claim 1, wherein: The second disconnecting switch (104) and the DC bias suppression device (107) are connected through a power cable (106).

6. The multi-transform common neutral DC bias suppression system of claim 1, wherein: The DC bias suppression device (107) is a resistance type DC bias suppression device or a capacitive DC bias suppression device; the resistance of the resistance type DC bias suppression device can be adjusted.

7. The multi-transform common neutral DC biasing suppression system of claim 6, wherein: The resistance of the resistance type DC bias suppression device can be adjusted in a range of 0-5 ohms.

8. The multi-transform common neutral DC biasing suppression system of claim 1, wherein: The second disconnecting switch (104) is installed on a device support, and the installation height is not less than 2.5 meters.

9. The multi-transform common neutral DC biasing system of any of claims 1-8, wherein: The DC bias suppression device (107) is installed on a device foundation.

10. The multi-transform common neutral DC biasing suppression system of claim 9, wherein: The height of the device foundation is 0.2-0.5 meters.

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