Transformer excitation inrush current suppression method and system based on multi-stage voltage division starting resistor

Abstract

The invention relates to the field of power system relay protection, and provides a transformer excitation inrush current suppression method and system based on a multi-stage voltage division starting resistor, and the method comprises the steps: judging whether a transformer is in a no-load switching-on state or a load switching-on state according to the primary side input power and a power factor of the transformer; if the transformer is in a no-load switching-on state, the voltage division loop is switched on, the main loop is switched off, and the primary side voltage of the transformer smoothly rises by controlling the size and the time interval of resistors which are accessed into the voltage division loop in a grading manner; and when the primary side voltage of the transformer is detected to reach the rated voltage, the main loop is switched on, and the voltage division loop is switched off. According to the multi-stage voltage-dividing starting resistor, when the transformer is switched on in a light load or no load mode, a voltage-dividing loop part is input, and the primary side voltage of the transformer is smoothly increased by inputting the resistor in a grading mode, so that excitation inrush current caused by rapid increase of the voltage and saturation of iron core magnetic flux is avoided, and the service life of the transformer is prolonged. The problem that large magnetizing inrush current is generated when the transformer is switched on under the condition of light load or no load is solved.

Description

Technical Field

[0001] The present invention relates to the field of relay protection of power systems, and more specifically, to a method and system for suppressing transformer excitation inrush current based on a multi-stage voltage-dividing starting resistor, which utilizes the principle of resistor voltage division to gradually increase the voltage on the transformer side to achieve the purpose of suppressing the excitation inrush current. Background Art

[0002] When the power transformer is switched on with light load or no load, the transformer voltage changes suddenly. Due to the nonlinear characteristics of the core magnetization curve and the influence of residual magnetic flux, a large excitation inrush current will be generated, which can reach several times or even dozens of times the rated current. The excitation inrush current will not only cause the transformer differential protection to malfunction, but may also cause equipment overload heating, grid voltage fluctuations, and excessive mechanical stress on the transformer windings, affecting the equipment life and the safety and stability of system operation in the long term. Therefore, how to suppress the transformer excitation inrush current has become the focus of scholars' research.

[0003] For suppressing the excitation inrush current, one method is to use an inrush current suppressor composed of an anti-parallel thyristor and a filter circuit to ensure that the transformer primary voltage rises smoothly to a steady-state value, avoiding the generation of transient magnetic flux, so as to achieve the effect of suppressing the inrush current (by Li Chunyan. Transformer excitation inrush current suppression method based on soft start [J]. Chongqing University, 2020.). Since it uses anti-parallel thyristors to achieve voltage rise, the harmonics are large, the structure of the filter part used is complex, and the cost is high. Another method is to use a second-order underdamped circuit and a voltage divider to achieve a gradual increase in the voltage amplitude applied to the third winding of the three-winding transformer, thereby eliminating the excitation inrush current that occurs when the transformer is closed, but it requires the addition of a third winding, which is difficult to implement in engineering (He Yue. A method for directly eliminating the transformer closing excitation inrush current [J]. Huazhong University of Science and Technology, 2011.). Summary of the invention

[0004] In order to solve the problem of large excitation inrush current generated when the transformer is switched on under light load or no load conditions, the present invention provides a transformer excitation inrush current suppression method and system based on multi-stage voltage-dividing starting resistors to reduce the excitation inrush current generated when the transformer is switched on under light load or no load conditions.

[0005] According to a first aspect of the present invention, a method for suppressing transformer excitation inrush current based on a multi-stage voltage-dividing starting resistor is provided, comprising:

[0006] Obtain the transformer primary side input power and transformer primary side power factor;

[0007] According to the primary-side input power of the transformer and the primary-side power factor of the transformer, determining whether the transformer is in a no-load closing state or a load closing state;

[0008] If the transformer is in a no-load closing state, the voltage-dividing circuit is put into operation, the main circuit is disconnected, and the voltage on the primary side of the transformer rises smoothly by controlling the size and time interval of the resistances connected to the voltage-dividing circuit in stages;

[0009] When it is detected that the primary voltage of the transformer reaches the rated voltage, the main circuit is put into operation and the voltage dividing circuit is disconnected.

[0010] According to a second aspect of the present invention, there is provided a transformer excitation inrush current suppression system based on a multi-stage voltage-dividing starting resistor, comprising:

[0011] An acquisition module, used for acquiring the primary side input power of the transformer and the primary side power factor of the transformer;

[0012] A judgment module, used for judging whether the transformer is in a no-load closing state or a load closing state according to the primary-side input power of the transformer and the primary-side power factor of the transformer;

[0013] The switching module is used to switch on the voltage-dividing circuit and disconnect the main circuit if the transformer is in a no-load closing state, and to control the size and time interval of the resistance connected to the voltage-dividing circuit in stages so that the primary voltage of the transformer rises smoothly; and when it is detected that the primary voltage of the transformer reaches the rated voltage, the main circuit is switched on and the voltage-dividing circuit is disconnected.

[0014] The present invention provides a transformer excitation inrush current suppression method and system based on a multi-stage voltage-dividing starting resistor. The method and system determine whether the transformer is in a no-load closing state or a load closing state according to the input power and power factor of the transformer primary side. If the transformer is in a no-load closing state, the voltage-dividing circuit is put into operation, the main circuit is disconnected, and the voltage on the primary side of the transformer is smoothly increased by controlling the size and time interval of the resistors connected to the voltage-dividing circuit in stages. When it is detected that the voltage on the primary side of the transformer reaches the rated voltage, the main circuit is put into operation and the voltage-dividing circuit is disconnected. The present invention designs a multi-stage voltage-dividing starting resistor. When the transformer is lightly loaded or no-loaded and closed, the voltage-dividing circuit part is put into operation. By putting in resistors in stages, the voltage on the primary side of the transformer is smoothly increased, thereby avoiding the excitation inrush current caused by the rapid rise in voltage and the saturation of the core magnetic flux, and solving the problem of a large excitation inrush current generated when the transformer is closed under light load or no-load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a transformer excitation inrush current suppression method based on a multi-stage voltage-dividing starting resistor provided by the present invention;

[0016] Figure 2 A schematic diagram of a circuit system including a voltage dividing circuit provided by the present invention;

[0017] Figure 3 This is a schematic diagram of the magnetizing inrush current without a voltage divider device;

[0018] Figure 4 Schematic diagram of magnetizing inrush current at a closing angle of 0°;

[0019] Figure 5 Schematic diagram of magnetizing inrush current at a closing angle of 30°;

[0020] Figure 6 Schematic diagram of magnetizing inrush current at a closing angle of 60°;

[0021] Figure 7 Schematic diagram of magnetizing inrush current at a closing angle of 90°;

[0022] Figure 8 Schematic diagram of magnetizing inrush current when residual magnetism is 0;

[0023] Fig. 9 This is a schematic diagram of the excitation inrush current with a residual magnetism of 0.3;

[0024] Fig.10 This is a schematic diagram of the excitation inrush current with a residual magnetism of 0.5;

[0025] Fig.11 This is a schematic diagram of the excitation inrush current with a residual magnetism of 0.7;

[0026] Fig.12 The schematic diagram of magnetizing inrush current of transformer YYn connection;

[0027] Fig.13 It is the schematic diagram of the magnetizing inrush current of the transformer Ynd11 connection;

[0028] Fig.14 It is the schematic diagram of the excitation inrush current of the transformer Yd11 connection;

[0029] Fig.15 A schematic structural diagram of a transformer excitation inrush current suppression system based on a multi-stage voltage-dividing starting resistor provided by the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention can be arbitrarily combined with each other to form a feasible technical solution. This combination is not subject to the constraints of the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] Figure 1 The present invention provides a flow chart of a transformer excitation inrush current suppression method based on a multi-stage voltage-dividing starting resistor, such as Figure 1 As shown, the method includes:

[0032] Step 1: Obtain the transformer primary side input power and the transformer primary side power factor.

[0033] Understandably, see Figure 2 The line system includes a main circuit part and a voltage-dividing circuit part. The main circuit is connected to the line system through the circuit breaker QF1, and the voltage-dividing circuit is connected to the line system through the circuit breaker QF2.

[0034] When the line system operates normally, the main circuit breaker QF1 is switched on and the voltage-dividing circuit breaker QF2 is switched off. During the operation of the line system, the transformer primary side input power and transformer primary side power factor are obtained.

[0035] Step 2: judging whether the transformer is in a no-load closing state or a load closing state according to the primary-side input power of the transformer and the primary-side power factor of the transformer.

[0036] It is understandable that the transformer is in a no-load or load-closed state based on the transformer primary-side input power and the transformer primary-side power factor. When the transformer is judged to be closed without load, is the rated capacity of the transformer, otherwise it is judged that the transformer is closed with load; only one criterion is likely to cause malfunction, adding the power factor criterion, that is, when the power factor of the primary side of the transformer is It is judged that the transformer is closed without load. When the primary power factor of the transformer is It is judged that the transformer is closed with load. Therefore, the starting criterion is:

[0037] .

[0038] Step 3: If the transformer is in a no-load closing state, the voltage-dividing circuit is put into operation, the main circuit is disconnected, and the primary voltage of the transformer rises smoothly by controlling the size and time interval of the resistance connected to the voltage-dividing circuit in stages.

[0039] It is understandable that if the transformer is closed with load, the line system operates normally, the main circuit breaker QF1 continues to be connected, and the voltage-dividing circuit breaker QF2 is disconnected; if the transformer is closed with light load or no load, in order to avoid grid shock or equipment damage caused by excitation surge current, the main circuit breaker QF1 is disconnected, and at the same time, the voltage-dividing circuit breaker QF2 is connected to the circuit and starts to provide a voltage-dividing function to suppress the excitation surge current.

[0040] Among them, see Figure 2 The voltage-dividing circuit includes three groups of adjustable resistor sequences, each of which includes multiple resistors connected in series, wherein one end of the three groups of adjustable resistor sequences is connected to the A, B, and C phases of the line through three circuit breakers QF2, and the other end of the three groups of adjustable resistor sequences is grounded, and the A, B, and C phases of the primary side of the transformer are connected in parallel to the three groups of adjustable resistor sequences. Each resistor in each group of adjustable resistor sequences is connected to the line through a switching switch.

[0041] For each phase, the voltage change of the parallel part is achieved by adjusting the resistance value of the adjustable resistor connected in parallel with the primary side of the transformer through switching the switch. The primary side voltage of the transformer is the same as the resistor voltage division, so that the adjustable resistance increases steadily, which can realize the smooth rise of the primary side voltage of the transformer and achieve the purpose of suppressing the excitation inrush current.

[0042] Each set of adjustable resistor sequences in the voltage divider circuit includes n resistors, and the resistance of the first resistor is The remaining n-1 resistors have a resistance of , , n≥2, and n is a positive integer.

[0043] In a possible implementation of the present invention, by controlling the size and time interval of the resistors connected to the voltage dividing circuit in stages, the voltage on the primary side of the transformer rises smoothly, including: by setting the initial starting voltage of the primary side of the transformer in the no-load closing state, designing , n and The size of the transformer primary voltage can be designed by setting the difference in the voltage rise before and after each resistor is put into operation. , n and The size of , n and The size of the transformer is determined by putting a resistor into each stage and setting the time interval between the two stages of resistors so that the primary side voltage of the transformer rises smoothly.

[0044] Specifically, when designing the first large resistor in the adjustable resistor sequence And other resistors The resistance value and the number of resistors in each resistor sequence can be designed based on the initial starting voltage set after connecting to the voltage divider circuit and the difference in the amplitude of the voltage rise on the primary side of the transformer before and after the first-level resistor is put into use. , n and .

[0045] Among them, by setting the initial starting voltage of the primary side of the transformer in the no-load closing state, the design , n and Size, including:

[0046] according to , n and , the expression for calculating the initial starting voltage of the primary side of the transformer in the no-load closing state is ,in, is the rated voltage of the primary side of the transformer, is the initial starting voltage of the primary side of the transformer. , n and The starting voltage can be realized from arrive Adjustment is made to take into account both the rapidity of the system and the effect of suppressing the excitation inrush current.

[0047] Among them, the amplitude difference of the transformer primary side voltage rise before and after each level of resistance is put into use is set, and the design , n and Size, including:

[0048] according to , n and , calculate the difference in the voltage rise on the primary side of the transformer before and after each level of resistance is put into operation ,in, is the rated voltage of the primary side of the transformer, The difference in the voltage rise on the primary side of the transformer before and after each level of resistance is put into operation; by setting , n and The size of exist arrive between.

[0049] Specifically, by setting the size and number of resistors in each stage, the magnitude of the voltage rise difference can be changed. The magnitude of the voltage rise difference is or The voltage rise amplitude difference should not be too large, which will generate a large excitation inrush current; the rise amplitude difference should not be too small, which will prolong the time for the transformer to reach the rated voltage and affect the stability of the system. After repeated verification, When the excitation inrush current is suppressed, the effect is better and the requirements of fast and stable system can be met.

[0050] In addition, when each level of resistance is put into use, the time interval for switching on and off of each level of circuit breaker can be set, so that the time interval for voltage rise can be controlled. The voltage rise time interval is generally set to Ts, so that the voltage can rise in different periods. Since the voltage divider circuit adopts resistive voltage division, there are fewer harmonics.

[0051] Specifically, the voltage divider circuit is put into operation, and the resistance of the first resistor in the voltage divider circuit is And other resistors , first put the largest resistor , Different resistance values ​​can be set according to different working conditions. After repeated verification, when the initial input voltage is 65% of the rated voltage, the initial excitation inrush current can be basically ignored. Then gradually put other small resistors in, and the time interval between each small resistor is Ts. In order to make the primary side voltage of the transformer rise smoothly with the power frequency cycle without generating large harmonics, Ts is taken as 0.02 here. By adjusting the resistance value of the initial input resistor , the resistance value and number of the subsequent small resistors can flexibly adjust the initial value of the primary voltage of the transformer, the rise time and the flatness of the voltage change curve to meet the needs of different working conditions. This voltage division method can effectively suppress the large excitation inrush current generated by the transformer due to voltage mutation, and also avoid the generation of large harmonic components.

[0052] Step 4: When it is detected that the primary voltage of the transformer reaches the rated voltage, the main circuit is switched on and the voltage dividing circuit is disconnected.

[0053] It is understandable that after all the resistors are put into operation, the voltage on the primary side of the transformer reaches the rated voltage and the system is stable. After the primary side of the transformer reaches the rated voltage, the voltage divider circuit QF2 is disconnected, the main circuit breaker QF1 is put into operation again, and the main circuit operates normally.

[0054] The transformer excitation inrush current suppression method based on multi-stage voltage-dividing starting resistors provided by the present invention is described below with multiple examples.

[0055] Example: A model was built in PSCAD for simulation verification, and the suppression of excitation inrush current under different closing angles and residual magnetism was verified. The excitation inrush current suppression effect of this method under the conditions of initial closing and reclosing was studied.

[0056] The system parameters are as follows: the power supply is 500KV RRL power supply, the transformer ratio is 500KV / 220KV, the capacity is 100MV·A, the short-circuit voltage percentage is 10.5%, the YY connection is adopted, and the voltage division method mentioned in the present invention is not adopted. The excitation inrush current of direct no-load closing is as follows Figure 3 shown.

[0057] Without using the voltage division method, after the transformer was closed under no-load condition, the primary side voltage directly reached the rated voltage, the excitation inrush current rose sharply, the maximum excitation inrush current reached 2.12KA, and then dropped rapidly, dropping to 0 after about 2.3s.

[0058] Example 1: Verify the transformer excitation inrush current under different closing angles. After setting different closing angles and adding the voltage divider circuit, it can be seen that the transformer excitation inrush current is well suppressed, and the maximum excitation inrush current is 0.38KA, which is much smaller than the excitation inrush current without the voltage divider. Figure 4~Figure 7 The figure shows the transformer excitation inrush current diagram for different closing angles. Figure 4 Schematic diagram of transformer excitation inrush current at a closing angle of 0°. Figure 5 Schematic diagram of transformer excitation inrush current at a closing angle of 30°. Figure 6 Schematic diagram of transformer excitation inrush current at a closing angle of 60°. Figure 7 Figure 1 is a schematic diagram of transformer excitation inrush current with a closing angle of 90°. Figures 4 to 7 It can be seen that the excitation inrush current is the most serious when the circuit breaker is closed at 0°, and the excitation inrush current is smaller when the circuit breaker is closed at 90°. After repeated verification, when the initial input voltage is 65% of the rated voltage, the initial excitation inrush current can be basically ignored. It can also be seen from the above figure that the excitation inrush current is basically 0 when the voltage is first input at 0.1s.

[0059] Example 2: Verify the transformer excitation inrush current under different residual magnetism conditions

[0060] The transformer is switched on at 0°, and the excitation inrush current is verified when the residual magnetism is 0, 0.3, 0.5, and 0.7. Figure 8~Figure 11 The figure shows the transformer excitation inrush current diagram under different residual magnetism. Figure 8 This is a schematic diagram of transformer excitation inrush current with zero residual magnetism. Fig. 9 This is a schematic diagram of transformer excitation inrush current with a residual magnetism of 0.3. Fig.10 This is a schematic diagram of transformer excitation inrush current with a residual magnetism of 0.5. Fig.11 This is a schematic diagram of the transformer excitation inrush current with a residual magnetism of 0.7.

[0061] Residual magnetism mainly affects the excitation surge current generated when the set voltage is reached for the first time. As can be seen from the above figure, the greater the residual magnetism, the greater the initial excitation surge current, reaching a maximum of 0.33KA, while the residual magnetism has less influence on the second excitation surge current, reaching a maximum of 0.38KA.

[0062] Example 3: Verify the transformer excitation inrush current under different transformer connection group numbers

[0063] Figure 12~Figure 14 The figure shows the transformer excitation inrush current diagram under different transformer connection group numbers. Fig.12 The schematic diagram of the excitation inrush current of the transformer YYn connection is shown in Figure 1. Fig.13 This is the schematic diagram of the excitation inrush current of the transformer Ynd11 connection. Fig.14 Schematic diagram of the excitation inrush current of transformer Yd11 connection.

[0064] The suppression effect of this method on excitation inrush current is verified under different transformer connection group numbers. Figure 12 to Figure 14 It can be seen that this method has strong adaptability and has a good suppression effect on the magnetizing inrush current of transformers with different connection group numbers.

[0065] See also Fig.15 , a transformer excitation inrush current suppression system based on a multi-stage voltage-dividing starting resistor provided by the present invention, the system comprising:

[0066] An acquisition module 1501 is used to acquire the primary side input power of the transformer and the primary side power factor of the transformer;

[0067] A judgment module 1502 is used to judge whether the transformer is in a no-load closing state or a load closing state according to the primary-side input power of the transformer and the primary-side power factor of the transformer;

[0068] The switching module 1503 is used to switch on the voltage-dividing circuit and disconnect the main circuit if the transformer is in a no-load closing state, and to make the primary side voltage of the transformer rise smoothly by controlling the size and time interval of the resistance connected to the voltage-dividing circuit in stages; and to switch on the main circuit and disconnect the voltage-dividing circuit when it is detected that the primary side voltage of the transformer reaches the rated voltage.

[0069] It can be understood that the transformer excitation inrush current suppression system based on multi-stage voltage-dividing starting resistors provided by the present invention corresponds to the transformer excitation inrush current suppression method based on multi-stage voltage-dividing starting resistors provided in the aforementioned embodiments. The relevant technical features of the transformer excitation inrush current suppression system based on multi-stage voltage-dividing starting resistors can refer to the relevant technical features of the transformer excitation inrush current suppression method based on multi-stage voltage-dividing starting resistors, which will not be repeated here.

[0070] The embodiment of the present invention provides a transformer excitation inrush current suppression method and system based on a multi-level voltage-dividing starting resistor, which has the following beneficial effects:

[0071] (1) A method for suppressing transformer excitation inrush current based on resistor voltage division is provided. It only adds a multi-stage resistor voltage division structure to suppress the transformer excitation inrush current. Compared with other methods, it has a simple structure, reduces investment costs, and has engineering practicality.

[0072] (2) Since this method uses resistor voltage division, the harmonic content is very small, and the rise time and initial voltage can be adjusted, which is suitable for a variety of working conditions;

[0073] (3) This method has a good effect in suppressing the excitation inrush current and can suppress the excitation inrush current under various working conditions, and has strong adaptability.

[0074] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0075] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0076] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0077] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0078] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0079] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for suppressing transformer excitation inrush current based on multi-stage voltage-dividing starting resistors, characterized in that: include: Obtain the transformer primary side input power and transformer primary side power factor; According to the primary-side input power of the transformer and the primary-side power factor of the transformer, determining whether the transformer is in a no-load closing state or a load closing state; If the transformer is in a no-load closing state, the voltage-dividing circuit is put into operation, the main circuit is disconnected, and the voltage on the primary side of the transformer rises smoothly by controlling the size and time interval of the resistances connected to the voltage-dividing circuit in stages; When it is detected that the primary voltage of the transformer reaches the rated voltage, the main circuit is put into operation and the voltage dividing circuit is disconnected.

2. The transformer excitation inrush current suppression method according to claim 1, characterized in that: The step of judging whether the transformer is in a no-load closing state or a load closing state according to the primary-side input power of the transformer and the primary-side power factor of the transformer comprises: If satisfied and , it is determined that the transformer is in the no-load closing state; If satisfied and , it is determined that the transformer is in the on-load closing state; in, is the primary side input power of the transformer, is the rated capacity of the transformer, is the primary side power factor of the transformer.

3. The transformer excitation inrush current suppression method according to claim 1, characterized in that: The voltage dividing circuit includes three groups of adjustable resistance sequences, each group of the adjustable resistance sequences includes a plurality of resistors connected in series, wherein the three groups of the adjustable resistance sequences are respectively connected to the A, B, and C phases of the line through the circuit breaker, and the A, B, and C phases of the primary side of the transformer are connected in parallel to the three groups of the adjustable resistance sequences; For each phase, the resistance of the adjustable resistor connected in parallel with the primary side of the transformer is adjusted by switching the switch to adjust the voltage on the primary side of the transformer.

4. The transformer excitation inrush current suppression method according to claim 3, characterized in that: Each group of the adjustable resistor sequence in the voltage divider loop includes n resistors, wherein the resistance of the first resistor is The remaining n-1 resistors have a resistance of , , n≥2, and n is a positive integer.

5. The transformer excitation inrush current suppression method according to claim 4, characterized in that: The step of controlling the magnitude and time interval of the resistors connected to the voltage dividing loop in stages so that the primary side voltage of the transformer rises smoothly comprises: By setting the initial starting voltage of the transformer primary side in the no-load closing state, the design , n and The size of the transformer primary voltage can be designed by setting the difference in the voltage rise before and after each resistor is put into operation. , n and size; According to the settings , n and The size of the resistor is set, one resistor is put into each level, and the time interval between the two levels of resistors is set.

6. The transformer excitation inrush current suppression method according to claim 5, characterized in that: By setting the initial starting voltage of the primary side of the transformer in the no-load closing state, the design , n and Size, including: according to , n and , the expression for calculating the initial starting voltage of the primary side of the transformer in the no-load closing state is ,in, is the rated voltage of the primary side of the transformer, is the initial starting voltage of the primary side of the transformer; By setting , n and The size of exist arrive between.

7. The transformer excitation inrush current suppression method according to claim 5, characterized in that: The voltage rise amplitude difference of the transformer primary side before and after each level of resistance is set, and the design , n and Size, including: according to , n and , calculate the difference in the voltage rise on the primary side of the transformer before and after each level of resistance is put into operation ,in, is the rated voltage of the primary side of the transformer, It is the difference in the voltage rise amplitude of the primary side of the transformer before and after each level of resistance is put into operation; By setting , n and The size of exist arrive between.

8. The transformer excitation inrush current suppression method according to claim 5, characterized in that: The time interval Ts between the two-stage resistors is 0.02s.

9. A transformer excitation inrush current suppression system based on multi-stage voltage-dividing starting resistors, characterized in that: include: An acquisition module, used for acquiring the primary side input power of the transformer and the primary side power factor of the transformer; A judgment module, used for judging whether the transformer is in a no-load closing state or a load closing state according to the primary-side input power of the transformer and the primary-side power factor of the transformer; The switching module is used to switch on the voltage-dividing circuit and disconnect the main circuit if the transformer is in a no-load closing state, and to control the size and time interval of the resistance connected to the voltage-dividing circuit in stages so that the primary voltage of the transformer rises smoothly; and when it is detected that the primary voltage of the transformer reaches the rated voltage, the main circuit is switched on and the voltage-dividing circuit is disconnected.

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