A transformer excitation inrush current suppression method and device

Abstract

This invention relates to the field of power system transformer protection technology, and discloses a method and device for suppressing transformer inrush current, comprising the following steps: disconnecting the bypass switch before energizing the transformer, so that the current-limiting reactor is in series; after the main circuit breaker is closed, the transient inrush current is limited by the current-limiting reactor; acquiring the transformer current signal, calculating the proportion of the second harmonic and the fluctuation rate of the fundamental current effective value; when the closing time or the proportion of the second harmonic and the effective value of the fundamental current both meet the preset switching criteria, calculating and outputting a closing command based on the current zero-crossing point and the inherent operating time of the bypass switch, short-circuiting the current-limiting reactor. This invention effectively limits the amplitude and duration of the inrush current at the moment of closing, while having no additional losses or voltage drop during normal operation. It has the advantages of simple principle, reliable operation, good economy and easy modification, and is applicable to various types of transformers.

Description

Technical Field

[0001] This invention relates to the field of power system transformer protection technology, specifically to a method and device for suppressing transformer inrush current. Background Technology

[0002] When a power transformer is switched on under no-load conditions, the core enters a saturated state, generating a high-amplitude inrush current. This inrush current causes a voltage dip in the power grid and produces an electrodynamic impact on the transformer windings. To suppress the inrush current, existing methods often involve temporarily connecting a current-limiting element in series in the transformer's power transmission circuit, and then short-circuiting the current-limiting element using a bypass switch after a fixed delay.

[0003] The fixed-delay bypass switching method has significant control blind spots. Due to fluctuations in grid operating parameters and variations in transformer residual magnetism, the inrush current decay period for each closing operation is not fixed. Relying on a single time setting cannot accurately determine the true moment when the transformer core exits saturation. A setting time that is too short will cause the bypass switch to operate before the inrush current has sufficiently decayed, triggering secondary electromagnetic disturbances in the system; a setting time that is too long will cause the current-limiting element to overheat due to prolonged load current. Furthermore, mechanical switches have inherent operating delays and time dispersion when performing closing operations. Existing control logic lacks phase compensation for the timing of operation, making it difficult to control the switch contacts to close precisely at the current zero-crossing point. This can cause transient operational overvoltages at the moment of bypass short-circuiting. In addition, the existing solution lacks a closed-loop backup protection mechanism for real-time monitoring of the heat accumulation of the current-limiting element when the bypass switch fails to operate due to mechanical jamming or control circuit malfunction. Once the switch fails to operate, the current-limiting element connected in series in the main circuit faces the safety risk of direct thermal damage.

[0004] Therefore, the purpose of this invention is to provide a method and apparatus for suppressing transformer inrush current, so as to overcome the shortcomings of the prior art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and apparatus for suppressing inrush current in transformers. This solves the problem that the use of a single fixed-delay control bypass switching during the transient process of transformer power transmission cannot accurately determine whether the core has left the saturation state, leading to secondary disturbances in the system. It also solves the safety hazards of the inability to accurately close at zero crossing due to the delay in the mechanical action of the switch, and the easy thermal damage of the current-limiting element when the bypass switch fails to operate.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a method for suppressing inrush current in a transformer, comprising the following steps: Before energizing the transformer, the controller outputs a trip command to drive the bypass switch to the open position, putting the current-limiting reactor into a series preparatory state; it controls the main circuit breaker to close, so that the bus voltage is applied to the transformer through the current-limiting reactor, which limits the inrush current generated at the moment of closing; after the main circuit breaker closes, the controller collects the transformer current signal in real time through the current transformer, extracts the second harmonic component from the current signal, and calculates the second harmonic ratio and the fundamental current RMS fluctuation rate; when the controller determines that the closing time, the second harmonic ratio, and the fundamental current RMS fluctuation rate all meet the preset switching criteria, it outputs a closing command; after outputting the closing command, the controller monitors the auxiliary contact signal change of the bypass switch in real time. If it is determined that the bypass switch has not closed on time based on the auxiliary contact signal change, it outputs a trip command to drive the main circuit breaker to trip, cutting off the power supply circuit to the transformer.

[0007] During implementation, the first terminal of the main circuit breaker is connected to the busbar, and the second terminal of the main circuit breaker is connected to the first terminal of the current-limiting reactor. The second terminal of the current-limiting reactor is connected to the power supply winding of the transformer, and a bypass switch is connected in parallel between the first and second terminals of the current-limiting reactor. A current transformer is installed in the primary circuit of the transformer to sense the current, and the signal output terminal of the current transformer is connected to the signal input terminal of the controller.

[0008] In the signal processing logic, the full-wave discrete Fourier transform algorithm is used to calculate the sampled data in the sliding data buffer, obtaining the real and imaginary coefficients corresponding to the harmonic orders, and calculating the effective values ​​of the fundamental current and the second harmonic current. The ratio of the effective value of the second harmonic current to the effective value of the fundamental current is taken as the second harmonic proportion. The difference between the effective value of the fundamental current of the current sampling cycle and the effective value of the fundamental current of the previous sampling cycle is calculated to obtain the effective fluctuation rate of the fundamental current.

[0009] In the state determination logic, the moment when the main circuit breaker completes the closing action is recorded, and the increment of the current moment relative to the moment of completion of the closing action is taken as the closing elapsed time. The controller performs a logical AND operation, and when all three conditions are met simultaneously—the closing elapsed time reaches a preset time criterion threshold, the second harmonic ratio is lower than a preset harmonic criterion threshold, and the fundamental current RMS volatility is lower than a preset volatility criterion threshold—the conditions for outputting the closing command are satisfied. This composite criterion mechanism solves the problem that single amplitude determination is easily affected by transient disturbances, ensuring the system's accuracy in identifying the critical point where the transformer core is out of saturation.

[0010] In terms of timing control, the phase information of the fundamental current's effective value is analyzed, and the zero-crossing point in the current sampling sequence is identified. Based on the system's rated frequency, the first current zero-crossing point after satisfying the output closing command condition is calculated as the target closing time. The difference between the target closing time and the pre-stored bypass switch's inherent operating time is calculated to determine the closing command issuance time. When the closing elapsed time reaches the closing command issuance time, the controller outputs an electrical signal to drive the bypass switch to perform the closing action. By compensating for the mechanical delay of the actuator, the transient electromagnetic shock generated by bypass switching on the system is reduced.

[0011] Regarding control parameter calibration, the moment the closing command is issued is recorded, and the actual contact moment of the bypass switch contacts is determined based on the change in auxiliary contact signals. The time deviation between the actual contact moment and the moment the closing command is issued is calculated, and this time deviation is compared with the pre-stored inherent operating time of the bypass switch within the controller. When the absolute value of the time deviation exceeds a preset step threshold, the pre-stored inherent operating time is automatically corrected. This feedback correction mechanism eliminates the operational variability caused by the long-term operation of the switch's mechanical components.

[0012] In the backup protection logic, the normally open and normally closed contact level signals of the bypass switch are acquired in real time, and the real-time physical location of the bypass switch is determined through logic state analysis. The logic state of the closing command is XORed with the real-time physical location to generate a state consistency error signal. If the state consistency error signal remains in a fault state for more than a preset time tolerance, it is determined that the bypass switch has not closed on time.

[0013] During the process of limiting the inrush current generated at the moment of closing the circuit breaker, thermal accumulation protection is simultaneously implemented for the current-limiting reactor. While the main circuit breaker is in the closed state and the bypass switch is in the open state, the controller performs a square operation on the current signal, and performs an integral accumulation operation based on the sampling step size and the internal resistance parameter of the current-limiting reactor to obtain the thermal accumulation amount of the current-limiting reactor. If the thermal accumulation amount exceeds the preset thermal limit safety threshold, a trip command is triggered to drive the main circuit breaker to trip. When a bypass switch closing fault or the thermal accumulation amount exceeds the thermal limit safety threshold is detected, a backup protection action signal is generated. The controller adds a preset execution delay to the time of backup protection action signal generation to determine the trip output time. At the trip output time, a control pulse is sent to the trip circuit of the main circuit breaker, and the audible and visual alarm device is activated to issue a fault warning. The above closed-loop monitoring logic prevents the current-limiting reactor from thermally damaged due to prolonged exposure to non-rated current.

[0014] The second aspect of the present invention provides a transformer inrush current suppression device, which is applied to a transformer inrush current suppression method provided in the first aspect of the present invention, including a busbar, a main circuit breaker, a current-limiting reactor, a bypass switch, a current transformer, and a controller.

[0015] The first terminal of the main circuit breaker is connected to the busbar. The first terminal of the current-limiting reactor is connected to the second terminal of the main circuit breaker, and the second terminal of the current-limiting reactor is connected to the primary winding of the transformer. This allows the current-limiting reactor to be connected in series to the transformer's power transmission circuit when the main circuit breaker is closed. A bypass switch is connected in parallel between the first and second terminals of the current-limiting reactor, allowing the current-limiting reactor to be connected or short-circuited by the opening and closing of the bypass switch. A current transformer is installed in the primary circuit of the transformer to collect current signals. The signal input terminals of the controller are connected to the signal output terminals of the current transformer and the auxiliary contacts of the bypass switch, respectively. The control output terminals of the controller are connected to the operating mechanism of the bypass switch and the tripping circuit of the main circuit breaker, respectively. Through the above connection structure of the primary-side hardware topology and the secondary-side control circuit, the entire process of intervention from physical current limiting to automatic bypass of inrush current is realized.

[0016] This invention provides a method and apparatus for suppressing transformer inrush current. It has the following beneficial effects: 1. This invention solves the problem of inaccurate bypass switching timing caused by single-time judgment by setting a composite criterion logic of current-limiting reactor and controller. At the initial stage of closing, it uses increased circuit impedance to suppress the peak inrush current and combines the second harmonic ratio and fundamental current fluctuation rate to identify the moment when the transformer leaves the saturation state. At the same time, it reduces the current impact on the transformer winding and the power grid during the power transmission process.

[0017] 2. This invention achieves precise short-circuiting of the current-limiting reactor at the current zero-crossing point by identifying the moment of current zero-crossing and compensating for the inherent operating time of the bypass switch. Combined with the automatic correction function for operating deviations, it can eliminate control errors caused by mechanical characteristic dispersion and reduce operating overvoltages and current surges caused by bypass operation.

[0018] 3. This invention integrates thermal accumulation monitoring of current-limiting reactors, status consistency verification, and backup tripping logic to construct an operational safety monitoring system. When the bypass switch fails to operate or the thermal load of the current-limiting reactor exceeds the safety threshold, the controller outputs a tripping command to cut off the main circuit, thus preventing thermal damage to the current-limiting components due to prolonged exposure to non-rated current and enhancing the reliability of system operation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the principle structure of the present invention; Figure 2 This is a system architecture diagram of the present invention; Figure 3 This is a flowchart illustrating the overall process of the method of the present invention. Figure 4 This is a transient current waveform diagram of the transformer at the moment of closing, according to an embodiment of the present invention. Figure 5 This is a waveform diagram showing the current decay trend over a longer time scale after the transformer is switched on, according to an embodiment of the present invention.

[0020] The components include: 1. Busbar; 2. Main circuit breaker; 3. Current-limiting reactor; 4. Bypass switch; 5. Current transformer; 6. Transformer; and 7. Controller. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] See attached document Figure 1 With appendix Figure 2 The present invention includes a busbar 1, a main circuit breaker 2, a current-limiting reactor 3, a bypass switch 4, a current transformer 5, a transformer 6, and a controller 7.

[0023] The main circuit breaker 2 is connected between bus 1 and the first terminal of the current-limiting reactor 3. The second terminal of the current-limiting reactor 3 is connected to the transformer 6. The bypass switch 4 is connected in parallel across the current-limiting reactor 3. The current transformer 5 is installed on the primary side of the transformer 6 to obtain the circuit current signal. The signal input terminal of the controller 7 is connected to the current transformer 5, and the control output terminal is connected to the opening and closing mechanism of the bypass switch 4 and the tripping coil of the main circuit breaker 2, respectively.

[0024] See attached document Figure 3 A method for suppressing transformer inrush current includes the following steps: The controller 7 outputs a command to drive the bypass switch 4 to the open position, so that the current limiting reactor 3 enters the series preparation state; When the main circuit breaker 2 closes, the voltage of bus 1 is applied to transformer 6 through current limiting reactor 3. Current limiting reactor 3 increases the circuit impedance at the moment of closing and limits the peak value of excitation inrush current. The controller 7 acquires the current signal of the transformer 6 in real time through the current transformer 5, extracts the second harmonic component of the current signal and calculates the effective value fluctuation rate of the fundamental current. Controller 7 determines that the closing time, the proportion of second harmonics and the fluctuation rate of the effective value of fundamental current all meet the preset switching criteria, and outputs a closing command to drive the bypass switch 4 to operate, short-circuiting the current limiting reactor 3, and the transformer 6 enters the normal operation state. The controller 7 monitors the signal change of the auxiliary contact of the bypass switch 4 in real time. If it is determined that the bypass switch 4 has not closed on time, the controller 7 outputs a trip command to drive the main circuit breaker 2 to trip and cut off the power supply circuit of the transformer 6.

[0025] The current-limiting reactor 3 and the bypass switch 4 are connected in series in parallel between the main circuit breaker 2 and the transformer 6. The first end of the current-limiting reactor 3 is connected to the load side lead-out terminal of the main circuit breaker 2, and the second end of the current-limiting reactor 3 is connected to the high-voltage winding input terminal of the transformer 6. The two main contacts of the bypass switch 4 are respectively connected across the first end and the second end of the current-limiting reactor 3.

[0026] The current-limiting reactor 3 is selected from dry-type air-core reactors, dry-type iron-core reactors, or oil-immersed iron-core reactors. The selection of the inductance value of the current-limiting reactor 3 depends on the leakage reactance parameters of the transformer 6. In order to limit the peak value of the inrush current to below a preset multiple, the inductance value of the current-limiting reactor 3 satisfies the following calculation formula: ; in, Let be the inductance value of current-limiting reactor 3; This is the transient offset coefficient; This represents the peak value of the phase voltage on the power supply side. The system's rated frequency; The inrush limit threshold; This is the equivalent leakage inductance of the transformer converted to the primary side. Transient offset coefficient. The value ranges from 1.2 to 1.8. Inrush flow restriction threshold. The current is set to twice the rated current of transformer 6. The inductance value of current-limiting reactor 3 is used. The equivalent leakage inductance of the transformer converted to the original side. The combined effect ensures that, even under the most severe saturation conditions of transformer core 6, the total circuit impedance limits the current amplitude to the inrush current limiting threshold. Within.

[0027] Bypass switch 4 is selected from vacuum circuit breakers, SF6 circuit breakers, or load switches with arc-extinguishing capabilities. The rated current of bypass switch 4 is not less than the rated current of transformer 6. The insulation level of the break of bypass switch 4 must be higher than the maximum voltage drop peak generated by current-limiting reactor 3 when inrush current passes through. The operating mechanism of bypass switch 4 is selected from spring operating mechanism, permanent magnet operating mechanism, or electromagnetic operating mechanism. After the controller 7 outputs the closing command, the moving contact and stationary contact of bypass switch 4 close, and current-limiting reactor 3 is short-circuited. The circuit current flows through the conductive circuit of bypass switch 4, and current-limiting reactor 3 is taken out of operation.

[0028] The short-time thermal stability current and dynamic stability current of the current-limiting reactor 3 must meet the transient requirements of power supply. The short-time current-carrying time of the current-limiting reactor 3 is the time interval from the instant the main circuit breaker 2 closes to the complete closure of the bypass switch 4, and the time interval is set between 0.5 seconds and 5 seconds. The coil structure of the current-limiting reactor 3 must have the mechanical strength to withstand the electromotive force generated by the inrush current. Since the current-limiting reactor 3 only operates during the transient power supply process, the thermal capacity of the current-limiting reactor 3 is determined according to the short-time operating conditions.

[0029] The current-limiting reactor 3 and the bypass switch 4 are electrically connected via a rigid busbar or high-voltage cable. The auxiliary contacts of the bypass switch 4 are connected to the status monitoring interface of the controller 7 via a secondary control cable. The auxiliary contact signal is used to provide feedback on the actual physical position of the bypass switch 4. The mechanical mounting of the current-limiting reactor 3 and the bypass switch 4 is supported by post insulators. The insulation class of the post insulators matches the voltage class of busbar 1.

[0030] The controller 7 is connected to the secondary winding of the current transformer 5 via a secondary shielded cable. The current transformer 5 is installed at the primary side inlet of the transformer 6. The turns ratio of the current transformer 5 is configured based on the rated current of the transformer 6 and the peak value of the inrush current that will occur. The model selection of the current transformer 5 must meet the transient characteristic requirements to ensure that the current signal does not saturate and distort under transient inrush current impact.

[0031] The controller 7 internally incorporates an analog signal conditioning module and an analog-to-digital converter (ADC). The current signal enters the analog signal conditioning module for low-pass filtering to remove high-frequency interference components and perform level matching. The analog signal conditioning module contains a current-to-voltage conversion circuit that converts the current signal into a voltage signal recognizable by the microprocessor through a high-precision sampling resistor. The ADC then discretizes the processed voltage signal and converts it into a digital sequence. To support accurate analysis of the second harmonic content of the current signal, the sampling frequency of the ADC module is... The following relationship must be satisfied: ; in, The sampling frequency; The highest harmonic order for analysis; This is the system's rated frequency. The highest harmonic order analyzed. Set to an integer not less than 5 to ensure that controller 7 can acquire fine features of the current waveform and extract higher harmonic components. System rated frequency. It is usually 50Hz or 60Hz.

[0032] The controller 7 is equipped with a status signal input terminal. The normally open auxiliary contact of the main circuit breaker 2 is connected to the status signal input terminal. The normally open auxiliary contact of the main circuit breaker 2 is used to provide the controller 7 with a level signal indicating that the main circuit breaker 2 is closed. The normally open and normally closed auxiliary contacts of the bypass switch 4 are respectively connected to the status signal input terminal. The normally open and normally closed auxiliary contact signals together serve as feedback criteria for the physical position of the bypass switch 4, used for logical verification of whether the state of the bypass switch 4 has actually changed.

[0033] Controller 7 has a command output interface. This interface includes a bypass closing output contact and a safety trip output contact. The bypass closing output contact is connected to the closing coil circuit of bypass switch 4 via an intermediate relay. The safety trip output contact is connected to the trip coil circuit of main circuit breaker 2 via an intermediate relay. Control logic signals generated internally by controller 7 are transmitted to the command output interface via an optocoupler module. The optocoupler module is used to block transient electromagnetic pulses generated by high-power switching operations from interfering with the core processing unit of controller 7.

[0034] During the bypass execution process, controller 7 monitors the current signal in real time through current transformer 5 and identifies the closing status of transformer 6. After the controller 7 processes the current using a logic algorithm and determines that it has entered a stable range, it closes the bypass closing output contact. The closing coil of bypass switch 4 is energized and drives the mechanical mechanism to close. If, after issuing the closing command, controller 7 determines through the auxiliary contact signal of bypass switch 4 that bypass switch 4 has not completed its position change within a preset time, controller 7 determines that the bypass switch 4 mechanism is jammed or that there is a control circuit fault, and then closes the safety trip output contact. The trip coil of main circuit breaker 2 is energized and drives the main circuit breaker 2 mechanism to trip, cutting off the power supply circuit of transformer 6.

[0035] For the data bus wiring of the microprocessor inside controller 7 and the specific circuit design of the power management module, those skilled in the art can use mature microcomputer protection device hardware systems. The specific soldering process and secondary cabinet installation method are well-known technologies in this field and will not be elaborated upon here. Through the above signal acquisition and command loop configuration, the transformer inrush current suppression system achieves closed-loop control from primary side transient current monitoring to secondary side actuator control.

[0036] Bypass switch 4 rated voltage According to the system rated voltage Select. Bypass switch 4 rated voltage. Satisfy the following formula: ; in, The rated voltage for bypass switch 4; This is the system rated voltage. The insulation level of bypass switch 4 must match the insulation level of transformer 6. The insulation performance of the break of bypass switch 4 must ensure that it does not break down when the maximum transient voltage drop occurs across the current-limiting reactor 3.

[0037] Bypass switch 4 rated current According to the rated current of transformer 6 Configuration. Bypass switch 4 rated current. Satisfy the following formula: ; in, The rated current of bypass switch 4; The reliability coefficient; This refers to the rated current of transformer 6. Reliability factor. The value range is 1.1 to 1.3. When the bypass switch 4 is in the closed state, it needs to carry the rated current of the transformer 6 for a long time, and the temperature rise of the conductive circuit of the bypass switch 4 needs to meet the power equipment operation standards.

[0038] The rated short-time withstand current and rated peak withstand current of bypass switch 4 are checked against the maximum short-circuit current of the system. When a short-circuit fault occurs inside transformer 6 and bypass switch 4 is in the closed state, bypass switch 4 must be able to withstand the thermal effect and electromechanical strength of the short-circuit current. The arc-extinguishing medium of bypass switch 4 is selected from vacuum or sulfur hexafluoride gas to ensure that the circuit is connected when the controller 7 issues a bypass command.

[0039] Main circuit breaker 2 serves as the main switch for the power supply circuit of transformer 6. The rated breaking current of main circuit breaker 2 must be greater than the maximum short-circuit current of the system. Main circuit breaker 2 is equipped with a trip coil, which is physically connected to the safety trip output interface of controller 7. When bypass switch 4 fails to close or the auxiliary contact feedback signal is abnormal, main circuit breaker 2 receives the trip command from controller 7 and the actuator trips, cutting off the power supply circuit of transformer 6.

[0040] Regarding the mechanical life requirements of bypass switch 4 and main circuit breaker 2, since the inrush current suppression device involves periodic power supply operations, the mechanical life of bypass switch 4 should not be less than 10,000 cycles. The closing time accuracy of bypass switch 4 needs to remain stable, in conjunction with the adaptive bypass logic of controller 7. For the protection level of the switch element base bracket and external housing, those skilled in the art can select according to the pollution level and climatic conditions of the installation environment. The protective design of the installation structure is well-known in the art and will not be elaborated here. Through the above selection and configuration of switch elements, the transformer inrush current suppression system achieves backup physical protection against bypass operation failure.

[0041] Controller 7 receives the current sampling sequence output from the analog-to-digital converter module. The current sampling sequence is preprocessed by a digital low-pass filter. The digital low-pass filter is used to filter out high-frequency interference components in the signal and eliminate the DC component generated by the secondary circuit of current transformer 5. The cutoff frequency of the digital low-pass filter is determined according to the system's rated frequency to ensure that the amplitude of the fundamental component and lower harmonic components is not attenuated.

[0042] Controller 7 is equipped with a sliding data buffer. The length of the sliding data buffer is one complete power frequency cycle. (Based on the sampling frequency...) With the system's rated frequency Number of sampling points per week Satisfying the formula: The controller 7 stores the latest current sampling point into the sliding data buffer and removes the sampling point with the earliest timestamp in the sliding data buffer to maintain the real-time update of the data window.

[0043] Controller 7 employs the full-wave discrete Fourier transform algorithm to extract harmonic features from the sampled data within the sliding data buffer. (Highest harmonic order analyzed) Corresponding real coefficients With imaginary part coefficient Satisfy the following formula: ; ; in, For the first The real part coefficients of the second highest analytical harmonic order; For the first The imaginary part coefficient of the second highest analytical harmonic order; The highest harmonic order for analysis; The sampling point number ranges from 0 to... integers, This represents the number of sampling points per wave. For the first The instantaneous current value at each sampling point; Pi is a constant. When calculating the fundamental component, the harmonic order... The value is 1. When calculating the second harmonic component, the harmonic order is... The value is 2.

[0044] Controller 7 calculates the first part based on the real and imaginary coefficients. The effective value of the second harmonic current. The effective value of the second harmonic current satisfies the following formula: ; in, For the first The effective value of the current at the second highest harmonic order; For the first The real part coefficients of the second highest analytical harmonic order; For the first The imaginary part coefficient of the second highest analytical harmonic order is used. The controller 7 then calculates the effective value of the fundamental current using the formula. With the effective value of the second harmonic current .

[0045] Controller 7 uses the fundamental current RMS value With the effective value of the second harmonic current Calculate the proportion of second harmonics Second harmonic proportion Satisfy the following formula: ; in, The proportion of second harmonics; This is the effective value of the second harmonic current; This represents the RMS value of the fundamental current. The proportion of second harmonics... Used to reflect the saturation level of transformer 6 core. During the initial stage of the transformer 6 closing transient process, the proportion of second harmonics... Maintain above the preset harmonic threshold.

[0046] Controller 7 synchronously calculates the RMS fluctuation rate of the fundamental current. Controller 7 uses the effective value of the fundamental current for the current cycle. RMS value of fundamental current compared to the previous cycle Comparative analysis was conducted. Fundamental current RMS volatility. Satisfy the following formula: ; in, The effective value fluctuation rate of the fundamental current; This represents the effective value of the fundamental current for the current cycle. This represents the RMS value of the fundamental current from the previous cycle. Fundamental current RMS volatility. Used to determine whether transformer 6 has transitioned from a transient process to a steady-state operating state.

[0047] For the underlying drivers of floating-point operations and the FFT fast algorithm within controller 7, those skilled in the art can use standard mathematical function libraries of digital signal processors or field-programmable gate arrays. Specific register configurations and addressing methods are well-known in the art and will not be elaborated upon here. Through the above signal processing logic, the transformer inrush current suppression system transforms the acquired current sampling sequence into criterion features with physical meaning.

[0048] The built-in timing unit of controller 7 records the running time after the main circuit breaker 2 is closed. Controller 7 will run time Compared with the preset time criterion threshold Compare the time criterion thresholds. The numerical setting references the longest closing transient process of transformer 6, with a value range between 300 milliseconds and 800 milliseconds. The time criterion is used to ensure the physical duration of the current-limiting reactor 3 connected to the circuit, avoiding malfunction of the bypass switch 4 due to signal disturbances at the moment of closing.

[0049] Controller 7 monitors the proportion of second harmonics in real time. Controller 7 will determine the proportion of second harmonics. With the preset harmonic criterion threshold Comparison. Harmonic criterion threshold. The critical point reflecting the disappearance of the saturation state of transformer 6 core is set between 15% and 20%. During the initial closing phase of transformer 6, the inrush current contains a second harmonic component, with the second harmonic accounting for a certain percentage. Greater than the harmonic criterion threshold When the second harmonic accounts for a certain percentage Reduced to harmonic criterion threshold The following determines that the 6th core of the transformer has desaturated.

[0050] Controller 7 monitors the fluctuation rate of the fundamental current RMS value in real time. Controller 7 will control the fluctuation rate of the fundamental current RMS value. Compared with the preset volatility criterion threshold Compare them. Volatility criterion threshold. Used to measure the stability of a current signal, with a numerical range set between 3% and 5%. When the effective value fluctuation of the fundamental current... Less than the volatility criterion threshold It is determined that the excitation current of transformer 6 has entered the steady-state decay range.

[0051] Controller 7 performs composite criterion logic operations. These operations utilize an AND gate structure, and the closing command status value... The following decision logic must be met: ; in, This is the status value of the closing command; Runtime; The time criterion threshold; The proportion of second harmonics; The threshold for harmonic criterion; The effective value fluctuation rate of the fundamental current; This is the volatility criterion threshold. Closing command status value. A value of 1 indicates that the bypass switching condition is met. When the running time criterion, the second harmonic criterion, and the fundamental current RMS fluctuation rate criterion are all met simultaneously, the controller 7 outputs a closing command. The multi-criteria composite judgment mechanism can avoid logical misjudgments caused by transient saturation of the current transformer 5 or signal noise.

[0052] After satisfying the composite criterion logic, controller 7 outputs a closing command to the drive circuit of bypass switch 4. Bypass switch 4 performs a closing action, short-circuiting the current-limiting reactor 3. Controller 7 confirms the physical position change through the feedback signal from the auxiliary contact of bypass switch 4. Controller 7 has an internal action timeout threshold. If the time elapsed after issuing the closing command exceeds the action timeout threshold, and controller 7 does not receive a closing signal from the normally open auxiliary contact, controller 7 determines that the bypass action has failed and outputs a trip command to the trip coil of main circuit breaker 2, cutting off the power supply circuit of transformer 6.

[0053] For the specific algorithm implementation of the periodic scanning mechanism of logic instructions and signal debouncing processing involved in controller 7, those skilled in the art can use conventional microcomputer protection programming logic. The design of software interrupt priority management and watchdog protection circuits are well-known technologies in this field and will not be elaborated upon here. Through the above composite criterion model, the transformer inrush current suppression system achieves the identification of transformer 6 from transient saturation state to steady-state operation state.

[0054] After controller 7 determines that the closing command status value is equal to 1, it enters the action timing calculation process. This process compensates for the physical action delay of bypass switch 4 and reduces secondary transient disturbances generated during the exit process of current-limiting reactor 3. Controller 7 has pre-stored the inherent closing time of bypass switch 4. This inherent closing time is determined based on the mechanical characteristic test data of bypass switch 4 and represents the time from energization of the closing coil to complete contact closure.

[0055] Controller 7 uses the fundamental current phase information to identify the zero-crossing point of the current sampling sequence. Controller 7 calculates the target closing time based on the system's rated frequency. The target closing time is selected at the current zero-crossing point one or more half-cycles after the closing conditions are met. The target closing time satisfies the following formula: ; in, The moment when the target is closed; The moment when the current sampling sequence crosses zero; It is a positive integer; The system's rated frequency. A positive integer. The value must ensure the target closure time. Later than the current calculation time.

[0056] Controller 7 based on the target closing time With the inherent closing time of bypass switch 4 Calculate the time when the closing command is issued The time when the closing command is issued. Satisfy the following formula: ; in, The time when the closing command is issued; The moment when the target is closed; This is the inherent closing time for bypass switch 4. The internal timer of controller 7 will issue the closing command when the running time reaches the specified time. When the command output interface is triggered, the bypass closing output contact is closed, and the bypass switch 4 closing coil is energized.

[0057] Controller 7 has the inherent closing time of bypass switch 4 Self-calibration function. Controller 7 records the time when the closing command is issued. The actual closing time of the contacts is determined based on the feedback signal from the auxiliary contacts of bypass switch 4. Controller 7 calculates the actual motion deviation. Actual movement deviation Satisfy the following formula: ; in, This is due to deviation from the actual action. This is the actual moment the contact closes; The time when the closing command is issued; This is the inherent closing time of bypass switch 4. If the actual operation deviates... When the absolute value exceeds the preset correction step size, the controller 7 adjusts the pre-stored inherent closing time of the bypass switch 4. Perform a numerical update.

[0058] For the implementation of the internal timer interrupt service function and auxiliary contact signal capture logic of controller 7, those skilled in the art can use the input capture function of a real-time operating system. The specific underlying driver encapsulation and interrupt management are well-known technologies in the field and will not be elaborated here. Through the above-mentioned action timing selection scheme, the transformer inrush current suppression system can counteract the mechanical inertia of the actuator, ensuring that the current-limiting reactor 3 is short-circuited at the current zero-crossing point.

[0059] The controller 7 acquires the auxiliary contact feedback signals of the bypass switch 4 in real time. The auxiliary contact feedback signals include normally open contact level signals and normally closed contact level signals. The controller 7 performs logical combination analysis on these level signals to determine the physical position state of the bypass switch 4. The physical position state of the bypass switch 4 is a binary variable; a value of 1 represents that the bypass switch 4 is in the closed position, and a value of 0 represents that the bypass switch 4 is in the open position.

[0060] Controller 7 performs a consistency check between the closing command status value and the physical position status of bypass switch 4. Controller 7 introduces a consistency error flag as the basis for judgment. The consistency error flag satisfies the following formula: ; in, This serves as a consistency error indicator. This is the status value of the closing command; This represents the physical position state of bypass switch 4. Operator Represents a logical XOR operation. When the consistency error flag is active... If the value is 1, it indicates that there is an inconsistency between the control command and the actual physical action of the bypass switch 4.

[0061] Controller 7 startup action confirmation timing process. (Inconsistency error flag) When the error duration is equal to 1, controller 7 accumulates the error duration. Controller 7 compares the error duration with the preset operating time tolerance. The operating time tolerance is determined based on the inherent closing time of bypass switch 4, and the value setting range is 1.5 to 2.5 times the inherent closing time of bypass switch 4. If the error duration exceeds the operating time tolerance, controller 7 determines that bypass switch 4 has experienced a mechanical failure to operate or an auxiliary contact circuit open fault.

[0062] Controller 7 synchronously monitors the effectiveness of the current sensing loop. Controller 7 acquires the RMS value of the fundamental current. The position status of main circuit breaker 2 is extracted. A position status value of 1 for main circuit breaker 2 indicates that the main circuit is connected. (Sensing circuit fault coefficient) Satisfy the following formula: ; in, The fault coefficient of the sensing circuit; This represents the effective value of the fundamental current. The no-load current threshold; Main circuit breaker 2 position status. When the sensor circuit fault coefficient... An equal value of 1 indicates a signal loss or abnormality in current transformer 5 or the signal transmission link. No-load current threshold. The setting is based on 1% to 2% of the rated current of transformer 6.

[0063] Controller 7 based on consistency error flag With the failure coefficient of the sensing circuit A protection action command is generated. After determining that the mechanical failure of the bypass switch 4 has caused a continuous consistency error, the controller 7 sends a trip command to the trip coil of the main circuit breaker 2. The main circuit breaker 2 performs the trip operation, cutting off the power supply circuit of the transformer 6 and preventing the current-limiting reactor 3 from operating under overload for an extended period of time.

[0064] For the design of the digital input debouncing filter and the priority allocation scheme for concurrent processing of multiple signals involved in the controller 7, those skilled in the art can use the programmable logic controller 7 or standard logic components of an industrial control computer. The opto-isolation and surge protection design of the input circuit are well-known technologies in the field and will not be elaborated upon here. Through the above-described closed-loop monitoring logic, the transformer inrush current suppression system achieves full-process operation monitoring from control commands to physical execution.

[0065] The controller 7 has a non-volatile counter in its internal memory to record the number of times the bypass switch 4 operates. Each time the controller 7 detects a closing command status value equal to 1 and the physical position status of the bypass switch 4 changes from 0 to 1, it increments the count of bypass switch 4 operations. The controller 7 compares this count with a preset mechanical life warning threshold. The mechanical life warning threshold is determined according to the mechanical characteristics specification of the bypass switch 4, and its value ranges from 8000 to 10000 operations. If the number of bypass switch 4 operations reaches the mechanical life warning threshold, the controller 7 outputs a maintenance warning signal through the communication interface.

[0066] Controller 7 monitors the thermal accumulation status of current-limiting reactor 3. Since current-limiting reactor 3 carries the inrush current during the transient closing process of transformer 6, if the closing time of bypass switch 4 is delayed, heat will accumulate in current-limiting reactor 3. Controller 7 calculates the thermal accumulation of current-limiting reactor 3 based on the current sampling sequence. The thermal accumulation of current-limiting reactor 3 satisfies the following formula: ; in, This refers to the heat accumulation of the current-limiting reactor 3. For the first The instantaneous current value at each sampling point; The sampling period; The equivalent resistance of current-limiting reactor 3; This represents the total number of sampling points from the moment the main circuit breaker 2 changes position state to 1 until the bypass switch 4 changes physical position state to 1. Sampling period. Based on sampling frequency It is determined that the following relation is satisfied: .

[0067] Controller 7 compares the accumulated heat of current-limiting reactor 3 with a preset thermal limit threshold. The thermal limit threshold is determined based on the short-time withstand heat capacity of current-limiting reactor 3. Controller 7 generates a thermal overload warning indicator. The thermal overload warning indicator satisfies the following logic: ; in, This is a thermal overload warning sign. This refers to the heat accumulation of the current-limiting reactor 3. This is the thermal limit threshold. When a thermal overload warning indicator appears... When the value is equal to 1, the controller 7 blocks the bypass switching logic and sends a trip command to the trip coil of the main circuit breaker 2, cutting off the power supply circuit of the transformer 6.

[0068] Controller 7 performs synchronous parameter drift diagnosis. Controller 7 statistically analyzes and compares the actual action deviations across multiple operating cycles. If the actual movement deviates from the preset number of consecutive steps... It exhibits a monotonically increasing trend, or the actual actions deviate. If the absolute value exceeds the deviation alarm limit, it is determined that the bypass switch 4 operating mechanism has mechanically deteriorated. Controller 7 determines the mechanical deterioration based on the actual action deviation. The output mechanism status maintenance signal is changed.

[0069] For the non-volatile memory read / write protocol and communication bus application layer message encapsulation involved in controller 7, those skilled in the art can use standard memory management logic and industrial communication protocols. Specific flash memory driver development and RS485 communication link design are well-known technologies in the field and will not be elaborated upon here. Through the above fault diagnosis and early warning scheme, the transformer inrush current suppression system achieves online assessment of the health status of core components.

[0070] Controller 7 generates a comprehensive backup trip trigger signal based on the operating status of bypass switch 4 and the physical status of current-limiting reactor 3. This comprehensive backup trip trigger signal is driven by a combination of logic consistency anomalies, thermal overload risks, and sensor circuit faults. The comprehensive backup trip trigger signal satisfies the following logical relationship: ; in, To integrate backup trip trigger signals; This serves as a consistency error indicator. The duration of the error; For action time tolerance; This is a thermal overload warning sign. The fault coefficient of the sensing loop. Operator For logical AND operation, operator The operation is a logical OR operation. When the result of the above logical combination is 1, the controller 7 determines that the backup protection tripping condition is met.

[0071] Controller 7 determines the trip execution time. The trip execution time has a fixed time delay relative to the closing command issuance time. The trip execution time satisfies the following formula: ; in, The trip execution time; The time when the closing command is issued; Backup trip delay. Backup trip delay The numerical settings require balancing the inherent closing time of bypass switch 4 and the thermal withstand time of current-limiting reactor 3. Backup trip delay. The numerical setting range is from 100 milliseconds to 300 milliseconds.

[0072] Controller 7 generates a trip control pulse. The width of the trip control pulse is determined by the pulse holding width. The pulse holding width is determined based on the electrical characteristics of the trip coil of the main circuit breaker 2, and is used to ensure that the main circuit breaker 2 completes the tripping action. The trip control pulse satisfies the following timing characteristics: ; in, This is a trip control pulse; This indicates that the output interface is at a high level; This indicates that the output interface is at a low level. The trip execution time; Runtime; Maintain pulse width. Pulse width maintenance. The numerical setting range is from 50 milliseconds to 150 milliseconds.

[0073] Controller 7 transmits trip control pulses through the safety trip output interface. The signal is sent to the tripping circuit of main circuit breaker 2. After main circuit breaker 2 performs the tripping operation, controller 7 confirms that the main circuit has been disconnected by detecting that the position status value of main circuit breaker 2 changes from 1 to 0. If a tripping control pulse is sent... During the preset observation period, the position status of the main circuit breaker 2 remains at 1, and the controller 7 activates the local audible and visual alarm.

[0074] For the hard-wired design of the trip output circuit and the anti-interference configuration of the intermediate relay involved in controller 7, those skilled in the art can adopt the wiring standards of industrial-grade relay protection devices. The specific anti-tripping circuit design and the trip coil current monitoring logic are well-known technologies in the field and will not be described in detail here. Through the above backup protection tripping timing scheme, the transformer inrush current suppression system constructs a protection closed loop from actuator failure to safe circuit disconnection.

[0075] Specific application examples: To further illustrate the application effect of the present invention in actual engineering, a preferred embodiment of the present invention will be described in detail below with reference to specific substation equipment parameters and waveform diagrams.

[0076] In this embodiment, transformer 6 is selected as a three-phase power transformer with a rated voltage of 110kV / 35kV and a rated capacity of 50MVA, and the rated current of the high-voltage winding is approximately 262A. To limit the peak excitation inrush current to less than twice the rated current of transformer 6 (i.e., the inrush current limit threshold is set to 524A), according to the inductance value calculation formula of current-limiting reactor 3, dry-type iron-core reactor with an inductive reactance value of approximately 20% to 50% of the short-circuit reactance of transformer 6 is selected for current-limiting reactor 3 in this embodiment. Bypass switch 4 is selected as a vacuum circuit breaker with a rated voltage of 126kV and a rated current of 630A to meet the reliability requirements of long-term rated current carrying and transient withstand of the system. At the same time, the action timeout threshold (i.e., the preset maximum delay time) in controller 7 is set to 2 seconds to limit the maximum allowable time for current-limiting reactor 3 to be connected to the system.

[0077] See attached document Figure 4 and attached Figure 5 , Figure 4 This is a transient current waveform diagram of transformer 6 at the moment of closing according to an embodiment of the present invention; Figure 5 This is a waveform diagram showing the current decay trend over a longer time scale after the transformer 6 is switched on, according to an embodiment of the present invention.

[0078] Combination Figure 4 and Figure 5 First, in the initial closing phase, as shown in the attached... Figure 4 As shown in the transient waveform, at the instant the main circuit breaker 2 closes, the total impedance of the closing circuit increases significantly due to the current-limiting reactor 3 being in a series preparatory state. The waveform diagram shows that the three-phase current did not experience a severe excitation impact of several thousand amperes during the closing transient; the initial positive peak value was effectively limited to approximately 600A to 800A, close to the preset 524A limit threshold. The image characteristics indicate that the early connection of the current-limiting reactor 3 effectively weakened the mechanical impact of the transient electrodynamic force on the windings of transformer 6.

[0079] Secondly, in the transient decay and state determination stage, as shown in the appendix... Figure 5 As shown in the global waveform envelope trend, the loop current exhibits a significant exponential smooth decay from the moment of closing. During this decay period, the controller 7 collects the current signal in real time and extracts the proportion of the second harmonic and the fluctuation rate of the fundamental current RMS value. When the closing operation time continues until the waveform gradually becomes symmetrical, the proportion of the second harmonic decays to below the preset harmonic criterion threshold, and the fluctuation rate of the fundamental current RMS value enters the stable range.

[0080] Subsequently, controller 7 determines that the closing time, second harmonic ratio, and volatility all meet the composite switching criteria, and after compensating for the inherent operating time of bypass switch 4, accurately outputs a closing command at the moment the current crosses zero. Bypass switch 4 successfully completes its closing action within the set maximum delay time window of 2 seconds, short-circuiting the current-limiting reactor 3. At this time, the current waveform smoothly transitions to the normal no-load operating state of transformer 6, without obvious secondary operation overvoltage or current surge disturbances. If, after issuing the command, controller 7 still does not detect the auxiliary contact closing signal of bypass switch 4 when the 2-second operating timeout threshold is reached, it directly triggers the backup protection trip sequence, driving the main circuit breaker 2 to trip and disconnect the power supply circuit of transformer 6, preventing thermal overload of current-limiting reactor 3.

[0081] Through the combination of the above-mentioned specific parameter configurations and control logic, this embodiment achieves safe suppression of inrush current during no-load closing of large-capacity transformer 6 and smooth bypass switching.

Claims

1. A method for suppressing inrush current in a transformer, characterized in that, Includes the following steps: Before power is supplied to the transformer (6), the controller (7) outputs a trip command to drive the bypass switch (4) to the open position, so that the current limiting reactor (3) enters the series preparation state; The main circuit breaker (2) is closed, so that the voltage of the bus (1) is applied to the transformer (6) through the current limiting reactor (3), and the inrush current generated at the moment of closing is limited by the current limiting reactor (3); After the main circuit breaker (2) is closed, the controller (7) collects the current signal of the transformer (6) in real time through the current transformer (5), extracts the second harmonic component from the current signal, and calculates the proportion of the second harmonic and the fluctuation rate of the effective value of the fundamental current. When the controller (7) determines that the closing time since the main circuit breaker (2) is closed, the proportion of the second harmonic, and the fluctuation rate of the effective value of the fundamental current all meet the preset switching criteria, it outputs a closing command. After the closing command is output, the controller (7) monitors the change of the auxiliary contact signal of the bypass switch (4) in real time. If it is determined that the bypass switch (4) has not closed on time according to the change of the auxiliary contact signal, the controller (7) outputs a trip command to drive the main circuit breaker (2) to trip and cut off the power supply circuit of the transformer (6).

2. The transformer inrush current suppression method according to claim 1, characterized in that, Before energizing the transformer (6), the following are also included: Connect the first end of the main circuit breaker (2) to the busbar (1), and connect the second end of the main circuit breaker (2) to the first end of the current limiting reactor (3); The second end of the current-limiting reactor (3) is connected to the power supply winding of the transformer (6), and the bypass switch (4) is connected in parallel between the first end of the current-limiting reactor (3) and the second end of the current-limiting reactor (3). The current transformer (5) is installed in the primary circuit of the transformer (6) to sense the current, and the signal output terminal of the current transformer (5) is connected to the signal input terminal of the controller (7).

3. The transformer inrush current suppression method according to claim 1, characterized in that, Extracting the second harmonic component from the current signal and calculating the proportion of the second harmonic and the effective value fluctuation rate of the fundamental current specifically includes: The full-wave discrete Fourier algorithm is used to calculate the sampled data in the sliding data buffer to obtain the real and imaginary coefficients corresponding to the harmonic order, and the effective values ​​of the fundamental current and the second harmonic current are calculated respectively. The ratio of the effective value of the second harmonic current to the effective value of the fundamental current is taken as the proportion of the second harmonic. The effective value of the fundamental current in the current sampling cycle is calculated to obtain the fluctuation rate of the effective value of the fundamental current.

4. The transformer inrush current suppression method according to claim 3, characterized in that, The determination that the closing time since the main circuit breaker (2) is closed, the proportion of the second harmonic, and the fluctuation rate of the effective value of the fundamental current all meet the preset switching criteria, specifically including: Record the moment when the main circuit breaker (2) completes the closing action, and use the increment of the current moment relative to the moment when the closing action is completed as the closing time. The logic AND operation is performed. When the following three conditions are met simultaneously: the closing time reaches a preset time criterion threshold, the proportion of the second harmonic is lower than a preset harmonic criterion threshold, and the effective value volatility of the fundamental current is lower than a preset volatility criterion threshold, the conditions for outputting the closing command are determined to be met.

5. A method for suppressing transformer inrush current according to claim 4, characterized in that, The output closing command specifically includes: Analyze the phase information of the effective value of the fundamental current and identify the zero crossing time in the current sampling sequence. Calculate the first current zero crossing time after the conditions for outputting the closing command are met according to the system rated frequency, and use it as the target closing time. Calculate the difference between the target closing time and the inherent operating time of the bypass switch (4) pre-stored inside the controller (7) to obtain the closing command issuance time; When the closing time reaches the closing command issuance time, the controller (7) outputs an electrical signal to drive the bypass switch (4) to perform the closing action.

6. The transformer inrush current suppression method according to claim 5, characterized in that, The output closing command also includes a step of automatically correcting the inherent operating time of the bypass switch (4), specifically: Record the time when the closing command is issued, and determine the actual contact time of the bypass switch (4) contacts based on the change of the auxiliary contact signal; Calculate the time deviation between the actual contact time and the time when the closing command is issued, and compare the time deviation with the inherent operating time of the bypass switch (4) that is pre-stored inside the controller (7); When the absolute value of the time deviation is greater than the preset step size threshold, the inherent action time of the bypass switch (4) stored in the controller (7) is automatically corrected.

7. The transformer inrush current suppression method according to claim 1, characterized in that, The determination of whether the bypass switch (4) failed to close on time based on the change of the auxiliary contact signal includes: The normally open contact level signal and normally closed contact level signal of the bypass switch (4) are collected in real time, and the real-time physical location of the bypass switch (4) is determined through logic state analysis. The logical state of the closing command is XORed with the real-time physical location to generate a state consistency error signal. If the state consistency error signal remains in a fault state for a period of time exceeding the preset time tolerance, it is determined that the bypass switch (4) has not closed on time.

8. A method for suppressing transformer inrush current according to claim 1, characterized in that, The process of limiting the inrush current generated at the moment of closing also includes the step of performing thermal accumulation protection on the current-limiting reactor (3), specifically: During the period when the main circuit breaker (2) is in the on state and the bypass switch (4) is in the off state, the controller (7) performs a square operation on the current signal, and performs an integral accumulation operation in combination with the sampling step size and the internal resistance parameter of the current limiting reactor (3) to obtain the heat accumulation of the current limiting reactor (3). If the accumulated heat exceeds the preset heat limit safety threshold, the output trip command is triggered to drive the main circuit breaker (2) to trip.

9. A method for suppressing transformer inrush current according to claim 8, characterized in that, The output trip command drives the main circuit breaker (2) to trip, specifically including: When a backup protection action signal is generated, the bypass switch (4) is detected to have a closing fault or the heat accumulation exceeds the heat limit safety threshold. The controller (7) adds a preset execution delay to the time when the backup protection action signal is generated to determine the trip output time; At the trip output moment, a control pulse is sent to the trip circuit of the main circuit breaker (2) and the audible and visual alarm device is driven to issue a fault warning.

10. A transformer inrush current suppression device, characterized in that, The transformer inrush current suppression method according to any one of claims 1-9 includes: Busbar (1); Main circuit breaker (2), the first end of which is connected to the busbar (1); A current-limiting reactor (3) is provided. The first end of the current-limiting reactor (3) is connected to the second end of the main circuit breaker (2). The second end of the current-limiting reactor (3) is connected to the primary winding of the transformer (6). The current-limiting reactor (3) is connected in series to the power supply circuit of the transformer (6) when the main circuit breaker (2) is closed. Bypass switch (4), the bypass switch (4) is connected in parallel between the first end of the current limiting reactor (3) and the second end of the current limiting reactor (3), and is used to enable or short-circuit the current limiting reactor (3) by opening and closing the bypass switch (4); Current transformer (5), which is installed in the primary side circuit of the transformer (6) for collecting current signals; The controller (7) has its signal input terminal connected to the signal output terminal of the current transformer (5) and the auxiliary contact of the bypass switch (4), respectively. The controller (7) has its control output terminal connected to the operating mechanism of the bypass switch (4) and the tripping circuit of the main circuit breaker (2), respectively.

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