Device and method for suppressing inrush current on high-voltage side of voltage transformer

Abstract

The invention belongs to the technical field of power distribution networks, and particularly discloses a voltage transformer high-voltage side inrush current suppression device and method, and the device comprises a line module, a suppression module, an acquisition module, an analysis module, a power module, a control module, a communication module, a display module and an alarm signal module. According to the invention, the fault type is judged by monitoring the voltage and current of the line, the phase selection and line selection of the fault are completed, the corresponding gear of the current-limiting resistor string is switched at the moment that the fault disappears, and the inrush current in the neutral point ungrounded system is suppressed. The problems that in an existing suppression technology, due to the fact that the current is too large and the heat capacity is small in the suppression process, long-term use cannot be achieved, a voltage transformer fuse is easily fused, even a body is burnt out, power failure occurs, and safe and stable operation of an electric power system is affected are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power distribution network, and in particular relates to a device and method for suppressing inrush current on the high-voltage side of a voltage transformer. Background Art

[0002] With the continuous development of distribution network, the proportion of cable lines in urban distribution network is getting higher and higher, and the line-to-ground capacitance current is increasing day by day. When a single-phase grounding fault occurs in a neutral point ungrounded system, the non-fault voltage rises to the line voltage, and their ground capacitance will be charged with the amount of charge under the line voltage. When the grounding fault disappears, the path between the charge on the conductor-to-ground capacitance and the earth is cut off. At this time, the line-to-ground voltage needs to be restored to the level of normal working phase voltage. Since the grounding point has been cut off, the free charge can only be discharged to the earth through the primary winding of the voltage transformer, which will cause a large impact current, thereby burning the voltage transformer. At the same time, the capacitive current flowing through the fault point will also increase, and the fault arc is difficult to extinguish automatically, which is easy to develop into a phase-to-phase accident. At the moment when the fault disappears, the line capacitance discharge current will push the core of the voltage transformer into the saturation area. When the grounding fault develops into an intermittent grounding fault, the capacitive current when the fault disappears will repeatedly impact the primary side core of the voltage transformer, pushing the core into the deep saturation area, causing damage to the voltage transformer.

[0003] In the project, measures such as installing a detuning device on the open winding of the voltage transformer and installing a resistor between the neutral point and the ground on the high-voltage side of the voltage transformer have been adopted to prevent it from burning. Installing a detuning device on the open winding of the voltage transformer is prone to misjudgment and refusal to operate, and may frequently operate when single-phase grounding causes damage to the voltage transformer, and the detection and elimination time is long. Installing a resistor between the neutral point and the ground on the high-voltage side of the voltage transformer uses a current-sensitive resistor as the core component. Under a continuous and long-term impact current, the thermal capacity of the current-sensitive resistor is difficult to meet the heat dissipation requirements, and thermal breakdown will occur. Secondly, the current-sensitive resistor element is installed in a sealed box, and its operating status cannot be detected in real time during long-term use. It is easy to cause burning or explosion after aging, which poses a safety hazard. In addition, the parameters of the current-sensitive resistor are too sensitive, and the parameters of the current-sensitive resistor required by different electrical equipment and distribution networks vary greatly, resulting in excessively high indirect costs. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing suppression technology cannot be used for a long time due to excessive current and small thermal capacity during the suppression process, which easily causes the voltage transformer fuse to melt or even the body to burn out, causing fault power outages and affecting the safe and stable operation of the power system. A voltage transformer high-voltage side surge suppression device and method are proposed.

[0005] The technical scheme of the present invention is as follows: in the first aspect, a voltage transformer high-voltage side surge suppression device comprises a line module, a suppression module, a collection module, an analysis module, a power module, a control module, a communication module, a display module and an alarm signal module; the line module comprises a voltage transformer primary winding circuit, a voltage transformer three-phase voltage circuit and a voltage transformer open triangle circuit, and the voltage transformer primary winding circuit, the voltage transformer three-phase voltage circuit and the voltage transformer open triangle circuit adopt a Y0 / Y0 / open triangle connection mode; the suppression module is connected to the ground terminal of the voltage transformer primary winding circuit in the line module; the power module, the control module and the communication module are all connected to the analysis module; the collection module is connected to the analysis module; The acquisition module is used to acquire voltage data on the low-voltage side of the line module and current data on the high-voltage side of the line module; The analysis module is used to receive and process the voltage data and the current data, and output the fault status information of the neutral point ungrounded system; the analysis module includes a trigger action signal unit, which is used to receive the fault status information of the neutral point ungrounded system and output the signal to the signal transceiver unit; The power module is used for supplying power; The control module is used to input fixed values ​​and control the operating status of the equipment; The communication module is used to realize the communication between the voltage transformer high-voltage side surge suppression device and the monitoring system; The suppression module is used to receive the fault status information of the neutral point ungrounded system, perform fault phase selection and fault line selection, and complete inrush current suppression; The suppression module includes a signal transceiver unit, a trigger unit and a current limiting resistor string; the signal transceiver unit is respectively connected to the trigger action signal unit and the trigger unit; the current limiting resistor string is respectively connected to the trigger unit and the current acquisition unit; The current-limiting resistor string is provided with a switch K and 4 gears of A, B, C and D, wherein gear A is connected to one end of the 9MΩ resistor R1, gear B is connected to one end of the 4MΩ resistor R2, gear C is connected to one end of the 1MΩ resistor R3, and gear D is directly grounded; the other end of the resistor R1, the other end of the resistor R2 and the other end of the resistor R3 are all grounded; The switch K is used to switch the corresponding gear of the current limiting resistor string to perform inrush current suppression.

[0006] Preferably, the acquisition module includes a three-phase voltage acquisition unit on the low-voltage side of the voltage transformer, an open triangle voltage acquisition unit on the low-voltage side of the voltage transformer, and a neutral point current acquisition unit on the high-voltage side of the voltage transformer; the three-phase voltage acquisition unit on the low-voltage side of the voltage transformer, the open triangle voltage acquisition unit on the low-voltage side of the voltage transformer, and the neutral point current acquisition unit on the high-voltage side of the voltage transformer are all connected to the analysis module; The voltage transformer low-voltage side three-phase voltage acquisition unit is used to acquire the voltage transformer low-voltage side three-phase voltage; The voltage transformer low-voltage side open triangle voltage acquisition unit is used to acquire the voltage transformer low-voltage side open triangle voltage; The voltage transformer high-voltage side neutral point current acquisition unit is used for the voltage transformer to acquire the high-voltage side neutral point current.

[0007] Preferably, the analysis module comprises a microprocessor and a trigger action signal unit; the microprocessor is connected to the trigger action signal unit; The microprocessor is used to receive and process the voltage data and current data, and output the fault status information of the neutral point ungrounded system; The trigger action signal unit is used to receive the neutral point ungrounded system fault state information and output a signal to the signal transceiver unit.

[0008] Preferably, the suppression module comprises a signal transceiver unit, a trigger unit and a current limiting resistor string; the signal transceiver unit is respectively connected to the trigger action signal unit and the trigger unit; the current limiting resistor string is respectively connected to the trigger unit and the current acquisition unit; The current-limiting resistor string is provided with a switch K and 4 gears of A, B, C and D, wherein gear A is connected to one end of the 9MΩ resistor R1, gear B is connected to one end of the 4MΩ resistor R2, gear C is connected to one end of the 1MΩ resistor R3, and gear D is directly grounded; the other end of the resistor R1, the other end of the resistor R2 and the other end of the resistor R3 are all grounded; The switch K is used to switch the corresponding gear of the current limiting resistor string to perform inrush current suppression.

[0009] Preferably, the device further comprises a display screen module and an alarm signal module; the display screen module and the alarm signal module are both connected to the analysis module; The display screen module is used to display the fault current size and equipment parameters; The alarm signal module is used to send out an alarm signal after a fault is detected.

[0010] In a second aspect, a method for suppressing inrush current on the high-voltage side of a voltage transformer comprises the following steps: S1. Monitor and collect voltage data and current data of the voltage transformer line module; S2. Analyze and process the voltage data and current data to obtain the fault information of the neutral point ungrounded system; S3. According to the fault status information of the neutral point ungrounded system, fault phase selection and fault line selection are performed to complete inrush current suppression.

[0011] Preferably, the step S2 specifically includes the following sub-steps: S21. Setting a threshold for the open delta voltage of the voltage transformer; S22. Determine whether the voltage transformer open delta voltage rise exceeds the threshold value according to the voltage data. If so, a single-phase grounding fault occurs in the neutral point ungrounded system; if not, execute step S23; S23. Determine whether the zero-sequence current at the head end of the line has a sudden change according to the current data. If so, execute step S24. If not, the neutral point ungrounded system has no fault and continues to operate normally; S24. Determine whether the zero-sequence current signals of each feeder and branch line of the neutral point ungrounded system mutate at the same time. If so, a single-phase grounding fault occurs in the neutral point ungrounded system; if not, a warning signal is issued and normal operation continues.

[0012] Preferably, the step S3 specifically includes the following sub-steps: S31. Perform fault phase selection and fault line selection according to the single-phase grounding fault, and display detailed information of the single-phase grounding fault on the display module. When the single-phase grounding fault disappears, execute step S32; S32. By triggering the action signal unit to send a signal to the signal receiving unit, the switch K is switched to the corresponding gear of the current limiting resistor string to suppress the inrush current, and execute step S33; S33. Determine whether the voltage data and the current data are less than a preset threshold value. If so, execute step S35; if not, return to step S31; S34. Send a signal to the signal receiving unit by triggering the action signal unit, switch the switch K to the D position of the current limiting resistor string and directly ground it to complete the inrush current suppression.

[0013] Preferably, the fault phase selection in step S3 specifically includes the following steps: S301. Analyze the three-phase voltage of the system with ungrounded neutral point; S302. According to the three-phase voltage analysis results of the neutral point ungrounded system, determine whether one phase voltage is close to 0 and the other two phase voltages are close to the line voltage. If so, it is a metallic grounding fault and the phase with voltage close to 0 is the fault phase; if not, execute step S303; S303. Determine whether in the three-phase voltage of the neutral point ungrounded system there is a situation where the first phase voltage is less than the second phase voltage, the first phase voltage is less than the third phase voltage, and the second phase voltage is greater than the third phase voltage. If so, it is determined to be a small resistance single-phase grounding fault, and the first phase voltage is the faulty phase; if not, it is determined to be a large resistance single-phase grounding fault, and the third phase voltage is the faulty phase.

[0014] Preferably, the fault line selection in step S3 specifically includes the following steps: S311. Close the busbar grounding bypass switch and analyze the zero-sequence current waveform of each feeder; wherein the busbar is connected to the primary winding circuit of the voltage transformer; S312. According to the zero-sequence current recordings of each feeder, determine whether the direction of the zero-sequence current is opposite to that of the zero-sequence current of other lines and whether the amplitude is the largest. If not, determine that the line is a non-fault line; if so, execute step S313; S313. Determine whether the direction of the zero-sequence current changes before and after the busbar grounding bypass switch is actuated. If not, determine that the line is a non-fault line; if so, determine that the line is a fault line.

[0015] The beneficial effects of the present invention are: 1. Each acquisition module and analysis module is flexible and reliable by performing real-time monitoring and calculation of the voltage and current of the voltage transformer.

[0016] 2. The voltage acquisition unit and the current acquisition unit in the acquisition module are used to conduct a comprehensive monitoring of the neutral point ungrounded system, so as to determine the type of fault, the phase selection of the fault and the line selection of the fault, and switch the current limiting resistor string to the corresponding gear in time, which is helpful for the staff to maintain the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure shows a principle block diagram of the voltage transformer high-voltage side surge suppression device provided in Example 1 of the present invention.

[0018] Figure 2 Shown is a schematic diagram of a current-limiting resistor string provided in Example 1 of the present invention.

[0019] Figure 3 The figure shows a flow chart of the method for suppressing inrush current on the high-voltage side of a voltage transformer provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0020] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to explain the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0021] Embodiment 1: like Figure 1As shown, a voltage transformer (PT) high-voltage side surge suppression device comprises a line module, a suppression module, a collection module, an analysis module, a power module, a control module, a communication module, a display module and an alarm signal module; the line module comprises a voltage transformer primary winding circuit, a voltage transformer three-phase voltage circuit and a voltage transformer open triangle circuit, and the voltage transformer primary winding circuit, the voltage transformer three-phase voltage circuit and the voltage transformer open triangle circuit adopt a Y0 / Y0 / open triangle connection mode; the suppression module is connected to the ground terminal of the voltage transformer primary winding circuit in the line module; the power module, the control module and the communication module are all connected to the analysis module; the collection module is connected to the analysis module; The acquisition module is used to acquire voltage data on the low-voltage side of the line module and current data on the high-voltage side of the line module; The analysis module is used to receive and process the voltage data and current data, and output the fault status information of the neutral point ungrounded system; The power module is used for supplying power; The control module is used to input fixed values ​​and control the operating status of the equipment; The communication module is used to realize the communication between the voltage transformer high-voltage side surge suppression device and the monitoring system; The suppression module is used to receive the fault status information of the neutral point ungrounded system, perform fault phase selection and fault line selection, and complete inrush current suppression.

[0022] In this embodiment, the device further comprises an alarm signal module and a display module, and the display module and the alarm signal module are both connected to the analysis module; The display screen module is used to display the fault current size and equipment parameters; The alarm signal module is used to send out an alarm signal after a fault is detected.

[0023] In this embodiment, the acquisition module includes a three-phase voltage acquisition unit on the low-voltage side of the voltage transformer, an open triangle voltage acquisition unit on the low-voltage side of the voltage transformer, and a neutral point current acquisition unit on the high-voltage side of the voltage transformer; the three-phase voltage acquisition unit on the low-voltage side of the voltage transformer, the open triangle voltage acquisition unit on the low-voltage side of the voltage transformer, and the neutral point current acquisition unit on the high-voltage side of the voltage transformer are all connected to the analysis module; The voltage transformer low-voltage side three-phase voltage acquisition unit is used to acquire the voltage transformer low-voltage side three-phase voltage; The voltage transformer low-voltage side open triangle voltage acquisition unit is used to acquire the voltage transformer low-voltage side open triangle voltage; The voltage transformer high-voltage side neutral point current acquisition unit is used for the voltage transformer to acquire the high-voltage side neutral point current.

[0024] In this embodiment, the analysis module includes a microprocessor and a trigger action signal unit; the microprocessor is connected to the trigger action signal unit; The microprocessor is used to receive and process the voltage data and current data, complete fault type judgment and phase and line selection, and compare with the threshold value; The trigger action signal unit is used to receive the neutral point ungrounded system fault state information and output a signal to the signal transceiver unit.

[0025] In this embodiment, the suppression module includes a signal transceiver unit, a trigger unit and a current limiting resistor string; the signal transceiver unit is respectively connected to the trigger action signal unit and the trigger unit; the current limiting resistor string is respectively connected to the trigger unit and the current acquisition unit.

[0026] In this embodiment, the current-limiting resistor string is provided with a switch K and 4 gears of A, B, C and D, wherein gear A is connected to one end of the 9MΩ resistor R1, gear B is connected to one end of the 4MΩ resistor R2, gear C is connected to one end of the 1MΩ resistor R3, and gear D is directly grounded; the other end of the resistor R1, the other end of the resistor R2 and the other end of the resistor R3 are all grounded; The switch K is used to switch the corresponding gear of the current limiting resistor string to perform inrush current suppression. During normal operation, the current limiting resistor string is switched to gear D. When a single-phase grounding fault occurs and a fault elimination signal is received, the current limiting resistor string is switched to gear C and switched to the corresponding gear according to the line capacitor discharge current calculated by the analysis module.

[0027] In this embodiment, the threshold value is determined by detecting the impact intensity of the line capacitor discharge current of the ungrounded neutral point system on the primary side of the voltage transformer, and determining that when the line capacitor discharge current exceeds 500mA, it will affect the safe use of the voltage transformer and there is a risk of burning the voltage transformer. When it exceeds 1500mA, the voltage transformer will be destroyed in a short time. The threshold value is input into the microprocessor through the control module.

[0028] The neutral point ungrounded system monitors the voltage and current of the voltage transformer in real time, sets a threshold for the open triangle voltage of the voltage transformer, and if the voltage transformer voltage rises above the threshold, it is determined that a single-phase grounding fault occurs in the neutral point ungrounded system; if the voltage transformer voltage rises within the threshold, it continues to monitor. When the open triangle voltage of the voltage transformer does not exceed the limit, but there is a sudden change in the zero-sequence current at the head end of the line, a zero-sequence current sudden change signal is first issued, and then a comprehensive analysis is made to see whether the zero-sequence current signals of each feeder and branch line of the neutral point ungrounded system have all mutated at the same time. If so, it is determined to be a single-phase grounding fault, and the fault transition resistance is large; if only the zero-sequence current on individual lines suddenly changes, it is considered to be a zero-sequence current sudden change caused by other reasons such as unbalanced load in the neutral point ungrounded system, and the neutral point ungrounded system only sends a signal and continues to restore the monitoring state. At the moment the fault disappears, switch to the corresponding gear of the current limiting resistor string to suppress the inrush current in the neutral point ungrounded system, thereby avoiding damage to the voltage transformer.

[0029] Embodiment 2: Based on the voltage transformer high-voltage side surge suppression device described in Example 1, this embodiment provides a voltage transformer high-voltage side surge suppression method, comprising the following steps: S1. Monitor and collect voltage data and current data of the voltage transformer line module; S2. Analyze and process the voltage data and current data to obtain the fault information of the neutral point ungrounded system; S3. According to the fault status information of the neutral point ungrounded system, fault phase selection and fault line selection are performed to complete inrush current suppression.

[0030] In this embodiment, step S2 specifically includes the following sub-steps: S21. Setting a threshold for the open delta voltage of the voltage transformer; S22. Determine whether the voltage transformer open delta voltage rise exceeds the threshold value according to the voltage data. If so, a single-phase grounding fault occurs in the neutral point ungrounded system; if not, execute step S23; S23. Determine whether the zero-sequence current at the head end of the line has a sudden change according to the current data. If so, execute step S24. If not, the neutral point ungrounded system has no fault and continues to operate normally; S24. Determine whether the zero-sequence current signals of each feeder and branch line of the ungrounded neutral point system suddenly change at the same time. If so, a single-phase grounding fault occurs in the ungrounded neutral point system; if not, the ungrounded neutral point system sends a warning signal and continues normal operation.

[0031] In this embodiment, step S3 specifically includes the following sub-steps: S31. Perform fault phase selection and fault line selection according to the single-phase grounding fault, and display detailed information of the single-phase grounding fault on the display screen. When the single-phase grounding fault disappears, execute step S32; S32. By triggering the action signal unit to send a signal to the signal receiving unit, the switch K is switched to the corresponding gear of the current limiting resistor string to suppress the inrush current, and then execute step S33; S33 determines whether the voltage data and the current data are less than a preset threshold value. If so, execute step S35; if not, return to step S31; S34 sends a signal to the signal receiving unit by triggering the action signal unit, switching the switch K to the D position of the current limiting resistor string to directly ground, thereby completing the inrush current suppression.

[0032] In this embodiment, the fault phase selection described in step S3 is specifically as follows: the phase selection basis for the single-phase grounding fault is the three-phase voltage of the bus after the fault. If one phase voltage is close to 0 and the other two phase voltages are close to the line voltage, it means that the fault transition resistance is very small and close to a metallic grounding fault, and the phase with a voltage close to 0 can be directly judged as the fault phase; and in this case, the magnitude of the three-phase voltage is very obvious in the transient process. If the fault phase selection time needs to be shortened, the three-phase voltage transient value can be directly used for judgment. Otherwise, it is judged whether there is a first phase voltage less than the second phase voltage, the first phase voltage less than the third phase voltage and the second phase voltage greater than the third phase voltage in the three-phase voltage of the neutral point ungrounded system. If so, it is judged as a small resistance single-phase grounding fault, and the first phase voltage is the fault phase; if not, it is judged as a large resistance single-phase grounding fault, and the third phase voltage is the fault phase. In a specific power distribution system, the three-phase voltage amplitude at the critical situation of a small resistance grounding fault can be analyzed according to the system voltage level, and then the accurate judgment criteria can be set using the three-phase voltage magnitude.

[0033] In this embodiment, the fault line selection described in step S3 is specifically: the busbar grounding bypass switch is actuated and closed, wherein the busbar is connected to the primary winding circuit of the voltage transformer, and the faulty line is determined by analyzing the zero-sequence current recording at the head end of each feeder. If the zero-sequence current on a certain line is opposite to the zero-sequence current of all other lines before the busbar grounding bypass switch is closed, and the amplitude is greater than that of other lines, and the zero-sequence current direction changes before and after the busbar grounding bypass switch is actuated, then the line can be determined to be a faulty line; and if any one of the above two points is not satisfied, it means that the line is a non-faulty line.

[0034] The surge suppression device on the high-voltage side of the voltage transformer uses a current-limiting resistor connected in series between the primary neutral point of the voltage transformer and the ground. The current-limiting resistor string has 4 gears, namely, gear A is 9MΩ, gear B is 4MΩ, gear C is 1MΩ, and gear D is directly grounded. Under normal operation, the three-phase voltage on the primary side of the voltage transformer is balanced, and the switch K is directly grounded in gear D, so that the voltage transformer can operate normally. When a single-phase grounding fault occurs in a neutral point ungrounded system and a fault elimination signal is received, the current-limiting resistor string switches to gear C, and switches to the corresponding gear according to the line capacitor discharge current calculated by the analysis module.

[0035] In summary, the present invention proposes a voltage transformer protection strategy that uses a current limiting resistor in series and switches to a corresponding gear to suppress inrush current when the fault disappears. By monitoring the voltage and current of the voltage transformer, it is determined whether the fault caused by the neutral point ungrounded system is a single-phase grounding fault, and the moment when the fault disappears is monitored in real time. When the grounding fault disappears, the path between the charge on the conductor-to-ground capacitor and the earth is cut off. At this time, the voltage of each line to the ground needs to be restored to the level of the normal working phase voltage. Since the grounding point has been cut off, the free charge can only be discharged to the earth through the primary winding of the voltage transformer, which will A large impact current will appear, which will burn the voltage transformer. Therefore, after monitoring that the single-phase grounding fault has disappeared, the trigger action signal unit will send a signal to the trigger device in the suppression module to switch the switch K to the gear to connect the current limiting resistor, so as to suppress the inrush current in the neutral point ungrounded system. When the neutral point ungrounded system is judged to be restored to normal through the monitored voltage and current, the trigger action signal unit will send a signal to the trigger device in the suppression module again to switch the switch K back to the direct grounding gear to disconnect the current limiting resistor, so that the neutral point ungrounded system can resume normal working state.

[0036] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A voltage transformer high-voltage side surge suppression device, characterized in that: It includes a line module, a suppression module, a collection module, an analysis module, a power module, a control module, a communication module, a display module and an alarm signal module; the line module includes a voltage transformer primary winding circuit, a voltage transformer three-phase voltage circuit and a voltage transformer open triangle circuit, and the voltage transformer primary winding circuit, the voltage transformer three-phase voltage circuit and the voltage transformer open triangle circuit adopt a Y0 / Y0 / open triangle connection mode; the suppression module is connected to the ground terminal of the voltage transformer primary winding circuit in the line module; the power module, the control module and the communication module are all connected to the analysis module; the collection module is connected to the analysis module; The acquisition module is used to acquire voltage data on the low-voltage side of the line module and current data on the high-voltage side of the line module; The analysis module is used to receive and process the voltage data and the current data, and output the fault status information of the neutral point ungrounded system; the analysis module includes a trigger action signal unit, which is used to receive the fault status information of the neutral point ungrounded system and output the signal to the signal transceiver unit; The power module is used for supplying power; The control module is used to input fixed values ​​and control the operating status of the equipment; The communication module is used to realize the communication between the voltage transformer high-voltage side surge suppression device and the monitoring system; The suppression module is used to receive the fault status information of the neutral point ungrounded system, perform fault phase selection and fault line selection, and complete inrush current suppression; The suppression module includes a signal transceiver unit, a trigger unit and a current limiting resistor string; the signal transceiver unit is respectively connected to the trigger action signal unit and the trigger unit; the current limiting resistor string is respectively connected to the trigger unit and the current acquisition unit; The current-limiting resistor string is provided with a switch K and 4 gears of A, B, C and D, wherein gear A is connected to one end of the 9MΩ resistor R1, gear B is connected to one end of the 4MΩ resistor R2, gear C is connected to one end of the 1MΩ resistor R3, and gear D is directly grounded; the other end of the resistor R1, the other end of the resistor R2 and the other end of the resistor R3 are all grounded; The switch K is used to switch the corresponding gear of the current limiting resistor string to perform inrush current suppression.

2. The voltage transformer high-voltage side surge suppression device according to claim 1, characterized in that: The acquisition module includes a three-phase voltage acquisition unit on the low-voltage side of a voltage transformer, an open triangle voltage acquisition unit on the low-voltage side of a voltage transformer, and a neutral point current acquisition unit on the high-voltage side of a voltage transformer; the three-phase voltage acquisition unit on the low-voltage side of a voltage transformer, the open triangle voltage acquisition unit on the low-voltage side of a voltage transformer, and the neutral point current acquisition unit on the high-voltage side of a voltage transformer are all connected to the analysis module; The voltage transformer low-voltage side three-phase voltage acquisition unit is used to acquire the voltage transformer low-voltage side three-phase voltage; The voltage transformer low-voltage side open triangle voltage acquisition unit is used to acquire the voltage transformer low-voltage side open triangle voltage; The voltage transformer high-voltage side neutral point current acquisition unit is used for the voltage transformer to acquire the high-voltage side neutral point current.

3. The voltage transformer high-voltage side surge suppression device according to claim 1, characterized in that: The analysis module further comprises a microprocessor; the microprocessor is connected to the trigger action signal unit; The microprocessor is used to receive and process the voltage data and current data, and output the fault status information of the neutral point ungrounded system.

4. The voltage transformer high-voltage side surge suppression device according to claim 3, characterized in that: The device also includes a display screen module and an alarm signal module; the display screen module and the alarm signal module are both connected to the analysis module; The display screen module is used to display the fault current size and equipment parameters; The alarm signal module is used to send out an alarm signal after a fault is detected.

5. A method for suppressing inrush current on the high-voltage side of a voltage transformer based on the inrush current suppression device on the high-voltage side of a voltage transformer according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1. Monitor and collect voltage data and current data of the voltage transformer line module; S2. Analyze and process the voltage data and current data to obtain the fault information of the neutral point ungrounded system; S3. According to the fault status information of the neutral point ungrounded system, fault phase selection and fault line selection are performed to complete inrush current suppression.

6. The method for suppressing inrush current at the high-voltage side of a voltage transformer according to claim 5, characterized in that: The step S2 specifically includes the following sub-steps: S21. Setting a threshold for the open delta voltage of the voltage transformer; S22. Determine whether the voltage transformer open delta voltage rise exceeds the threshold value according to the voltage data. If so, a single-phase grounding fault occurs in the neutral point ungrounded system; if not, execute step S23; S23. Determine whether the zero-sequence current at the head end of the line has a sudden change according to the current data. If so, execute step S24. If not, the neutral point ungrounded system has no fault and continues to operate normally; S24. Determine whether the zero-sequence current signals of each feeder and branch line of the neutral point ungrounded system mutate at the same time. If so, a single-phase grounding fault occurs in the neutral point ungrounded system; if not, a warning signal is issued and normal operation continues.

7. The method for suppressing inrush current at the high-voltage side of a voltage transformer according to claim 6, characterized in that: The step S3 specifically includes the following sub-steps: S31. Perform fault phase selection and fault line selection according to the single-phase grounding fault, and display detailed information of the single-phase grounding fault on the display module. When the single-phase grounding fault disappears, execute step S32; S32. By triggering the action signal unit to send a signal to the signal receiving unit, the switch K is switched to the corresponding gear of the current limiting resistor string to suppress the inrush current, and execute step S33; S33. Determine whether the voltage data and the current data are less than a preset threshold value. If so, execute step S35; if not, return to step S31; S34. Send a signal to the signal receiving unit by triggering the action signal unit, switch the switch K to the D position of the current limiting resistor string and directly ground it to complete the inrush current suppression.

8. The method for suppressing inrush current at the high-voltage side of a voltage transformer according to claim 7, characterized in that: The fault phase selection in step S3 specifically includes the following steps: S301. Analyze the three-phase voltage of the system with ungrounded neutral point; S302. According to the three-phase voltage analysis results of the neutral point ungrounded system, determine whether one phase voltage is close to 0 and the other two phase voltages are close to the line voltage. If so, it is determined to be a metallic grounding fault, and the phase with a voltage close to 0 is the fault phase; if not, execute step S303; S303. Determine whether in the three-phase voltage of the neutral point ungrounded system there is a situation where the first phase voltage is less than the second phase voltage, the first phase voltage is less than the third phase voltage, and the second phase voltage is greater than the third phase voltage. If so, it is determined to be a small resistance single-phase grounding fault, and the first phase voltage is the faulty phase; if not, it is determined to be a large resistance single-phase grounding fault, and the third phase voltage is the faulty phase.

9. The method for suppressing inrush current at the high-voltage side of a voltage transformer according to claim 5, characterized in that: The fault line selection in step S3 specifically includes the following steps: S311. Close the busbar grounding bypass switch and analyze the zero-sequence current waveform of each feeder; wherein the busbar is connected to the primary winding circuit of the voltage transformer; S312. According to the zero-sequence current recordings of each feeder, determine whether the direction of the zero-sequence current is opposite to that of the zero-sequence current of other lines and whether the amplitude is the largest. If not, determine that the line is a non-fault line; if so, execute step S313; S313. Determine whether the direction of the zero-sequence current changes before and after the busbar grounding bypass switch is actuated. If not, determine that the line is a non-fault line; if so, determine that the line is a fault line.

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