High-voltage high-energy nonlinear adaptive power grid protection method and system

Abstract

The invention relates to the technical field of power equipment, and discloses a high-voltage high-energy nonlinear self-adaptive power grid protection method and system, and the method comprises the steps: determining different threshold coefficients according to the waveform type of residual current and the limit amplitude in a time window, obtaining an actual threshold, comparing real-time data with the actual threshold, and obtaining a protection result of the real-time data; and entering different protection states according to a comparison result, judging a voltage change rate, and changing the protection state when the voltage change rate is greater than a set value. The invention provides a high-voltage high-energy nonlinear self-adaptive power grid protection method and system, and can solve or at least alleviate the problems that an existing power grid protection method is not suitable for a high-proportion new energy power grid with large fluctuation, and power generation equipment is easily misjudged to be off the grid due to voltage fluctuation.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection and control, and in particular to a high-voltage and high-energy nonlinear adaptive power grid protection method and system. Background Art

[0002] At present, the distribution network generally adopts an ungrounded system. Although it improves the reliability of power supply, once a fault occurs, it is very easy to cause overvoltage to damage equipment and even threaten personal safety due to the lack of effective suppression measures. In order to improve the safety and reliability of power supply, corresponding measures need to be taken to suppress fault overvoltage.

[0003] Therefore, the neutral point grounding method can be used to protect the safety of the power grid. After a single-phase grounding fault occurs, there is no obvious short-circuit current and the power grid can be operated for two hours. Generally, grounding line selection technology is used for processing. However, the grounding point of a single-phase grounding fault will cause electric shock accidents to people and animals; it will also cause the voltage of the non-grounded phase to increase and develop into a phase-to-phase short circuit. After a two-phase and three-phase fault occurs, a large short-circuit current will be generated.

[0004] However, conventional neutral point grounding protection is less applicable in power grids with a high proportion of new energy (such as wind power and photovoltaic access scenarios). The power grid has higher requirements for power grid protection due to the volatility of new energy, harmonic interference and high failure rate. The grid-connected voltage itself fluctuates greatly, and when equipment fails or lightning strikes, the voltage fluctuation is aggravated. Therefore, conventional protection methods are prone to misjudgment, causing equipment to be disconnected from the grid, and the resonance lasts for a long time, which is more likely to cause equipment damage.

[0005] For example, the invention patent with the publication number CN112436481B discloses an adaptive protection method for distribution lines in a neutral point non-effective grounding system, including: selecting fault phases according to the power frequency electrical quantities of the distribution lines monitored in real time to determine the fault type; using the fault type, targeted single-phase grounding protection, two-phase grounding short-circuit protection, and three-phase short-circuit protection distribution line protection measures are put into use; when a single-phase grounding fault occurs, the traveling wave protection based on the initial traveling wave polarity of the zero-mode voltage and current is put into use; when a two-phase grounding short-circuit fault occurs, the channelless protection based on the power frequency current and voltage information and the healthy phase current mutation information is put into use; when a three-phase short-circuit fault occurs, the small differential overcurrent protection using a fast circuit breaker is put into use. The invention determines the fault type by the power frequency electrical quantity, and selectively isolates the fault point for different fault types, thereby improving the power supply reliability of the distribution line. However, it only considers safety and reliability. If it is used in a high-proportion new energy power grid, during fluctuations, fault misjudgment will occur and the fault will be isolated. Isolation means disconnection from the grid. Although the grid safety is guaranteed, unnecessary disconnection from the grid will bring certain economic losses. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art, solve or at least alleviate the problem that the existing power grid protection method is not suitable for a high-proportion new energy power grid with large fluctuations, and provide a high-voltage and high-energy nonlinear adaptive power grid protection method and system.

[0007] To achieve the above object, the present invention provides the following technical solution: a high voltage and high energy nonlinear adaptive power grid protection method, comprising the following steps: S1, current transformer and voltage transformer monitor the waveform data of residual current and the real-time voltage and current of neutral point; S2. Determine different threshold coefficients according to the waveform type of the residual current and the limit amplitude within the time window; S3, multiplying the threshold coefficient obtained in step S2 by the corresponding determination threshold to obtain an actual threshold; S4, comparing the data monitored in step S1 with the actual threshold in step S3, and entering different protection states according to the comparison result; S5. While performing steps S2 and S3, determine the voltage change rate. When the voltage change rate is greater than the set value, change the protection state in S4.

[0008] In order to further realize the present invention, the following technical solutions may be preferably selected: Preferably, in step S1, the waveform type is determined by the ratio of the shorter time to the longer time in the positive and negative residual current durations in the residual current waveform; When the ratio is 0.75-1, it is determined as a sine wave, when the ratio is 0.4-0.75, it is determined as a half wave, and when the ratio is 0-0.4, it is determined as a distorted wave.

[0009] Preferably, the threshold coefficient is changed when the waveform type is a sine wave and the limit amplitude in the time window is greater than the first determination value; When the waveform type is a distorted wave and the limit amplitude in the time window is greater than a second determination value, the threshold coefficient is changed; When the waveform type is half-wave and the amplitude in the time window is stable, the threshold coefficient is changed; The threshold coefficient when the waveform category is a sine wave is greater than the threshold coefficient when the waveform category is a distorted wave, and the threshold coefficient when the waveform category is a distorted wave is greater than the threshold coefficient when the waveform category is a half wave.

[0010] Preferably, in step S3, the determination threshold comprises a first voltage threshold, a second voltage threshold and a first current threshold, and the first voltage threshold, the second voltage threshold and the first current threshold are respectively multiplied by threshold coefficients to obtain a first voltage actual threshold, a second voltage actual threshold and a first current actual threshold.

[0011] Preferably, step S4 comprises the following steps: S401, compare the real-time voltage monitored by the voltage transformer with the first voltage actual threshold and the second voltage actual threshold. When the real-time voltage is greater than the second voltage actual threshold, enter the overvoltage guarantee state. When the real-time voltage is less than the first voltage actual threshold, enter step S402. When the real-time voltage is greater than the first voltage actual threshold and less than the second voltage actual threshold, enter step S403. S402, comparing the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, entering the conventional protection state, when the real-time current is greater than the first current actual threshold value, entering the resonance protection state; S403, compare the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, enter the arc extinguishing protection state, when the real-time current is greater than the first current actual threshold value, enter the overvoltage protection state.

[0012] Preferably, step S5 comprises the following steps: S51, monitor the real-time voltage through the voltage transformer, and obtain the voltage change rate of the current time window, and record the voltage change rate of each time window in turn; S52, comparing the voltage change rate of the current time window with the voltage change rates of the previous multiple time windows. When the voltage change rates of the multiple time windows are not all positive and do not all exceed the set value, proceed to step S53. When the voltage change rates of the multiple time windows are all positive and all exceed the set value, proceed to step S54. S53, maintaining the protection state in step S4; S54, the protection state determined in step S4 is changed to the overvoltage protection state, and the process proceeds to step S55; S55, the protection state in the subsequent first time window remains in the overvoltage protection state; S56: The protection state in the subsequent second time window is changed according to the voltage change rate in the subsequent first time window and the second time window.

[0013] Preferably, the step 56 comprises the following steps: S561, determine the positive or negative state of the voltage change rate in the first subsequent time window. If the voltage change rate is positive, proceed to step S562a; if the voltage change rate is negative, proceed to step S562b; S562a, judging the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is positive, the protection state remains in the overvoltage protection state. If the voltage change rate is negative, proceed to step S563a; S562b, determine the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is negative, the protection state is changed to the protection state determined in step S4. If the voltage change rate is positive, proceed to step S563b; S563a, determine the absolute value of the voltage change rate, if the absolute value of the voltage change rate is less than the set value, maintain the overvoltage protection state, if the absolute value of the voltage change rate is greater than the set value, change to the protection state determined in step S4; S563b, determine the absolute value of the voltage change rate. If the absolute value of the voltage change rate is greater than the set value, maintain the overvoltage protection state. If the absolute value of the voltage change rate is less than the set value, change to the protection state determined in step S4.

[0014] Preferably, in step S5, while performing steps S52 to S56, the following steps are also performed: S57, monitoring the voltage boost value within the time window, when the voltage boost value is greater than the warning threshold, the protection state is changed to the overvoltage protection state.

[0015] A high-voltage and high-energy nonlinear adaptive power grid protection system adopts a high-voltage and high-energy nonlinear adaptive power grid protection method. The power grid protection system includes a grounding protection unit, the grounding protection unit includes a grounding resistor, a small resistor, a compensation resistor and a self-healing capacitor, and the grounding resistor and the compensation resistor are both nonlinear resistors; The front end of the grounding resistor is connected to the neutral point through a fuse, the rear end of the grounding resistor is connected in series with the small resistor and then grounded, and the self-healing capacitor and the compensation resistor are connected in series and in parallel with the small resistor in sequence; In the conventional protection state and the resonance protection state, the connection relationship of the grounding protection part remains unchanged; In the arc extinguishing protection state, the self-healing capacitor and the compensation resistor are disconnected from the grounding protection part; In the overvoltage protection state, the small resistor is disconnected from the grounding protection part; In the overvoltage protection state, the small resistor is disconnected from the grounding protection part, and the self-healing capacitor is in a short-circuit state.

[0016] Preferably, the grounding protection unit further includes a discharge mechanism, and the discharge mechanism is connected in parallel to the self-healing capacitor; In the resonance protection state, the discharge frequency of the discharge mechanism is linked with the resonance frequency to suppress ferromagnetic resonance and accelerate energy discharge.

[0017] The beneficial effects of the present invention are: 1. The present invention distinguishes the grid status through residual current waveform recognition technology, dynamically adjusts the actual threshold according to the waveform type, and enters the protection state of different scenarios according to the actual threshold, thereby improving the accuracy of protection action, reducing the misjudgment rate while ensuring the safety of equipment, and reducing the off-grid rate of equipment.

[0018] 2. The present invention determines the voltage change rate to correct the protection state, predicts voltage fluctuations, adjusts the protection state in combination with the output characteristics of the new energy power grid, and ensures equipment safety.

[0019] 3. The grounding protection unit of the present invention makes matching adjustments according to different protection states, which can not only provide better protection but also improve the accuracy of fault isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart of the protection method of the present invention.

[0021] Figure 2 This is a flow chart of step S4 of the present invention.

[0022] Figure 3 This is a flow chart of step S5 of the present invention.

[0023] Figure 4 This is a flow chart of step S56 of the present invention. DETAILED DESCRIPTION

[0024] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] Embodiment 1 Conventional neutral point grounding protection is less applicable in power grids with a high proportion of new energy (such as wind power and photovoltaic access scenarios). The power grid has higher requirements for power grid protection due to the volatility, harmonic interference and high failure rate of new energy. The grid-connected voltage itself fluctuates greatly, and when equipment fails or lightning strikes, the voltage fluctuation is aggravated. Therefore, conventional protection methods are prone to misjudgment, causing equipment to be disconnected from the grid, and the resonance lasts for a long time, which is more likely to cause equipment damage.

[0027] This embodiment discloses a high-voltage and high-energy nonlinear adaptive power grid protection system, which includes a grounding protection unit, which includes a grounding resistor, a small resistor, a compensation resistor and a self-healing capacitor. The grounding resistor and the compensation resistor are both nonlinear resistors.

[0028] The front end of the grounding resistor is connected to the neutral point through a fuse, the rear end of the grounding resistor is connected in series with the small resistor and then grounded, and the self-healing capacitor and the compensation resistor are connected in series in sequence and in parallel with the small resistor.

[0029] In the conventional protection state and the resonance protection state, the connection relationship of the grounding protection part remains unchanged; in normal operation, the neutral point voltage is very low, the grounding resistance is in a high resistance state, the current flowing through it is very small, and it is basically in an open circuit state, which is equivalent to being ungrounded. It has the characteristics of high reliability and good safety of ungrounded power supply. When resonance occurs, the huge energy capacity of the grounding resistance quickly absorbs the resonance energy, and the small resistance provides additional damping. The self-healing capacitor is connected in parallel with the small resistance to reduce the impedance to high-frequency current and reduce the resonance caused by self-excited oscillation. The combination of the two can effectively eliminate ferromagnetic resonance and line break resonance overvoltage; in this state, the current passing through the fuse is small, and the fuse is not easy to be burned out.

[0030] In the arc extinguishing protection state, the self-healing capacitor and the compensation resistor are disconnected from the grounding protection part. The grounding resistor absorbs the grounding charge energy and limits the arc recovery voltage in time, prompting the arc to extinguish quickly. The small resistor shortens the reignition time by discharging the residual load. In this state, the current passing through the fuse is not high, reducing the probability of fuse burning, and quickly extinguishing the arc to ensure the safety of equipment and power grid.

[0031] In the overvoltage protection state, the small resistor is disconnected from the grounding protection part, and the neutral point voltage will increase at the same time. The grounding resistor absorbs energy and becomes conductive, limiting the voltage within the set range. The small resistor is disconnected to avoid burning, and the self-healing capacitor absorbs the overvoltage in the peak state to prevent voltage mutation. After the self-healing capacitor is fully charged, the compensation resistor continues to absorb energy, reducing the residual pressure and accelerating energy discharge. In this state, the current passing through the fuse is relatively high. The self-healing capacitor and the compensation resistor prevent the current fluctuation from increasing and causing the fuse to be directly disconnected, thereby reducing the probability of the fuse burning. On the premise of ensuring the safety of equipment and power grid, the probability of accidental disconnection of power generation equipment is reduced.

[0032] In the overvoltage protection state, the small resistor is disconnected from the grounding protection part, and the self-healing capacitor is in a short-circuit state to prevent the small resistor from burning. In this state, the current passing through the fuse is high, and the grounding resistor and the compensation resistor quickly absorb energy to ensure that the overvoltage of the system is limited to less than 2 times, avoiding equipment damage. At the same time, the current can increase rapidly and quickly burn out the fuse to isolate the equipment from the power grid.

[0033] In addition, the grounding protection unit further includes a discharge mechanism, which is connected in parallel to the self-healing capacitor. In the resonance protection state, the discharge frequency of the discharge mechanism is linked with the resonance frequency to suppress ferromagnetic resonance and accelerate energy discharge.

[0034] The grounding protection unit of the present invention makes matching adjustments according to different protection states, which can not only provide better protection, but also improve the accuracy of fault isolation and reduce the possibility of misjudgment of power generation equipment being disconnected from the grid due to voltage fluctuations.

[0035] Embodiment 2 The existing power grid protection method selectively isolates the fault point according to different fault types, thereby improving the reliability of power supply of distribution lines. However, it only considers safety and reliability. If it is used in a high-proportion new energy power grid, during fluctuations, faults may be misjudged and isolated. Isolation means disconnection from the grid. Although the grid safety is guaranteed, unnecessary disconnection from the grid will bring certain economic losses.

[0036] Reference Figure 1-Figure 4 , a high voltage and high energy nonlinear adaptive power grid protection method, comprising the following steps: S1, current transformer and voltage transformer monitor the waveform data of residual current and the real-time voltage and current of neutral point; S2. Determine different threshold coefficients according to the waveform type of the residual current and the limit amplitude within the time window; S3, multiplying the threshold coefficient obtained in step S2 by the corresponding determination threshold to obtain an actual threshold; S4, comparing the data monitored in step S1 with the actual threshold in step S3, and entering different protection states according to the comparison result; S5. While performing steps S2 and S3, determine the voltage change rate. When the voltage change rate is greater than the set value, change the protection state in S4.

[0037] Specifically, in step S1, the waveform type is determined by the ratio of the shorter time to the longer time in the positive and negative residual current durations in the residual current waveform; When the ratio is 0.75-1, it is determined as a sine wave, when the ratio is 0.4-0.75, it is determined as a half wave, and when the ratio is 0-0.4, it is determined as a distorted wave.

[0038] When the waveform type is a sine wave and the limit amplitude in the time window is greater than a first determination value, the threshold coefficient is changed; When the waveform type is a distorted wave and the limit amplitude in the time window is greater than a second determination value, the threshold coefficient is changed; When the waveform type is half-wave and the amplitude in the time window is stable, the threshold coefficient is changed; The threshold coefficient when the waveform category is a sine wave is greater than the threshold coefficient when the waveform category is a distorted wave, and the threshold coefficient when the waveform category is a distorted wave is greater than the threshold coefficient when the waveform category is a half wave; In this embodiment, the threshold coefficient when the waveform type is a sine wave is 0.9-1, the threshold coefficient when the waveform type is a distorted wave is 0.75-0.9, and the threshold coefficient when the waveform type is a half wave is 0.6-0.75.

[0039] Specifically, in step S3, the determination threshold includes a first voltage threshold, a second voltage threshold and a first current threshold, and the first voltage threshold, the second voltage threshold and the first current threshold are respectively multiplied by threshold coefficients to obtain a first voltage actual threshold, a second voltage actual threshold and a first current actual threshold.

[0040] Reference Figure 2 , the step S4 comprises the following steps: S401, compare the real-time voltage monitored by the voltage transformer with the first voltage actual threshold and the second voltage actual threshold. When the real-time voltage is greater than the second voltage actual threshold, enter the overvoltage guarantee state. When the real-time voltage is less than the first voltage actual threshold, enter step S402. When the real-time voltage is greater than the first voltage actual threshold and less than the second voltage actual threshold, enter step S403. S402, comparing the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, entering the conventional protection state, when the real-time current is greater than the first current actual threshold value, entering the resonance protection state; S403, compare the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, enter the arc extinguishing protection state, when the real-time current is greater than the first current actual threshold value, enter the overvoltage protection state.

[0041] The present invention distinguishes the grid status through residual current waveform recognition technology, dynamically adjusts the actual threshold according to the waveform type, and enters the protection state of different scenarios according to the actual threshold, thereby improving the accuracy of protection action, reducing the misjudgment rate while ensuring the safety of equipment, and reducing the off-grid rate of equipment.

[0042] The present invention also determines the voltage change rate to correct the protection state, predicts voltage fluctuations, adjusts the protection state in combination with the output characteristics of new energy, and ensures equipment safety.

[0043] Embodiment 3 According to the output characteristics of the new energy power grid, the determination of the voltage change rate is optimized, so that the protection status can be adjusted more accurately according to the voltage fluctuation.

[0044] Reference Figure 3, the step S5 comprises the following steps: S51, monitor the real-time voltage through the voltage transformer, and obtain the voltage change rate of the current time window, and record the voltage change rate of each time window in turn; S52, comparing the voltage change rate of the current time window with the voltage change rates of the previous multiple time windows. When the voltage change rates of the multiple time windows are not all positive and do not all exceed the set value, proceed to step S53. When the voltage change rates of the multiple time windows are all positive and all exceed the set value, proceed to step S54. S53, maintaining the protection state in step S4; S54, the protection state determined in step S4 is changed to the overvoltage protection state, and the process proceeds to step S55; S55, the protection state in the subsequent first time window remains in the overvoltage protection state; S56: The protection state in the subsequent second time window is changed according to the voltage change rate in the subsequent first time window and the second time window.

[0045] Reference Figure 4 In order to more accurately determine whether the fluctuation has ended after adjusting the protection state, thereby reducing the probability of misjudgment, the step 56 includes the following steps: S561, determine the positive or negative state of the voltage change rate in the first subsequent time window. If the voltage change rate is positive, proceed to step S562a; if the voltage change rate is negative, proceed to step S562b; S562a, judging the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is positive, the protection state remains in the overvoltage protection state. If the voltage change rate is negative, proceed to step S563a; S562b, determine the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is negative, the protection state is changed to the protection state determined in step S4. If the voltage change rate is positive, proceed to step S563b; S563a, determine the absolute value of the voltage change rate, if the absolute value of the voltage change rate is less than the set value, maintain the overvoltage protection state, if the absolute value of the voltage change rate is greater than the set value, change to the protection state determined in step S4; S563b, determine the absolute value of the voltage change rate. If the absolute value of the voltage change rate is greater than the set value, maintain the overvoltage protection state. If the absolute value of the voltage change rate is less than the set value, change to the protection state determined in step S4.

[0046] In order to avoid damage to the equipment and the power grid caused by unexpected instantaneous faults, the following steps are performed while performing steps S52 to S56 in step S5: S57. The voltage boost value within the monitoring time window is monitored. When the voltage boost value is greater than the warning threshold, the protection state is changed to the overvoltage protection state.

[0047] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high voltage and high energy nonlinear adaptive power grid protection method, characterized in that: The following steps are involved: S1, current transformer and voltage transformer monitor the waveform data of residual current and the real-time voltage and current of neutral point; S2. Determine different threshold coefficients according to the waveform type of the residual current and the limit amplitude within the time window; S3, multiplying the threshold coefficient obtained in step S2 by the corresponding determination threshold to obtain an actual threshold; S4, comparing the data monitored in step S1 with the actual threshold in step S3, and entering different protection states according to the comparison result; S5. While performing steps S2 and S3, determine the voltage change rate. When the voltage change rate is greater than the set value, change the protection state in S4.

2. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 1, characterized in that: In the step S1, the waveform type is determined by the ratio of the shorter time to the longer time in the positive and negative residual current durations in the residual current waveform; When the ratio is 0.75-1, it is determined as a sine wave, when the ratio is 0.4-0.75, it is determined as a half wave, and when the ratio is 0-0.4, it is determined as a distorted wave.

3. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 2, characterized in that: When the waveform type is a sine wave and the limit amplitude in the time window is greater than a first determination value, the threshold coefficient is changed; When the waveform type is a distorted wave and the limit amplitude in the time window is greater than a second determination value, the threshold coefficient is changed; When the waveform type is half-wave and the amplitude in the time window is stable, the threshold coefficient is changed; The threshold coefficient when the waveform category is a sine wave is greater than the threshold coefficient when the waveform category is a distorted wave, and the threshold coefficient when the waveform category is a distorted wave is greater than the threshold coefficient when the waveform category is a half wave.

4. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 1, characterized in that: In step S3, the determination threshold includes a first voltage threshold, a second voltage threshold and a first current threshold, and the first voltage threshold, the second voltage threshold and the first current threshold are multiplied by threshold coefficients to obtain a first voltage actual threshold, a second voltage actual threshold and a first current actual threshold.

5. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 4, characterized in that: The step S4 comprises the following steps: S401, compare the real-time voltage monitored by the voltage transformer with the first voltage actual threshold and the second voltage actual threshold. When the real-time voltage is greater than the second voltage actual threshold, enter the overvoltage guarantee state. When the real-time voltage is less than the first voltage actual threshold, enter step S402. When the real-time voltage is greater than the first voltage actual threshold and less than the second voltage actual threshold, enter step S403. S402, comparing the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, entering the conventional protection state, when the real-time current is greater than the first current actual threshold value, entering the resonance protection state; S403, compare the real-time current monitored by the current transformer with the first current actual threshold value, when the real-time current is less than the first current actual threshold value, enter the arc extinguishing protection state, when the real-time current is greater than the first current actual threshold value, enter the overvoltage protection state.

6. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 5, characterized in that: The step S5 comprises the following steps: S51, monitor the real-time voltage through the voltage transformer, and obtain the voltage change rate of the current time window, and record the voltage change rate of each time window in turn; S52, comparing the voltage change rate of the current time window with the voltage change rates of the previous multiple time windows. When the voltage change rates of the multiple time windows are not all positive and do not all exceed the set value, proceed to step S53. When the voltage change rates of the multiple time windows are all positive and all exceed the set value, proceed to step S54. S53, maintaining the protection state in step S4; S54, the protection state determined in step S4 is changed to the overvoltage protection state, and the process proceeds to step S55; S55, the protection state in the subsequent first time window remains in the overvoltage protection state; S56: The protection state in the subsequent second time window is changed according to the voltage change rate in the subsequent first time window and the second time window.

7. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 6, characterized in that: S56 includes the following steps: S561, determine the positive or negative state of the voltage change rate in the first subsequent time window. If the voltage change rate is positive, proceed to step S562a; if the voltage change rate is negative, proceed to step S562b; S562a, judging the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is positive, the protection state remains in the overvoltage protection state. If the voltage change rate is negative, proceed to step S563a; S562b, determine the positive or negative state of the voltage change rate in the subsequent second time window. If the voltage change rate is negative, the protection state is changed to the protection state determined in step S4. If the voltage change rate is positive, proceed to step S563b; S563a, determine the absolute value of the voltage change rate, if the absolute value of the voltage change rate is less than the set value, maintain the overvoltage protection state, if the absolute value of the voltage change rate is greater than the set value, change to the protection state determined in step S4; S563b, determine the absolute value of the voltage change rate. If the absolute value of the voltage change rate is greater than the set value, maintain the overvoltage protection state. If the absolute value of the voltage change rate is less than the set value, change to the protection state determined in step S4.

8. A high voltage and high energy nonlinear adaptive power grid protection method according to claim 6, characterized in that: In step S5, while performing steps S52 to S56, the following steps are also performed: S57. The voltage boost value within the monitoring time window is monitored. When the voltage boost value is greater than the warning threshold, the protection state is changed to the overvoltage protection state.

9. A high-voltage high-energy nonlinear adaptive power grid protection system, which adopts the high-voltage high-energy nonlinear adaptive power grid protection method as described in any one of claims 5 to 8, characterized in that: The power grid protection system comprises a grounding protection unit, which comprises a grounding resistor, a small resistor, a compensation resistor and a self-healing capacitor, wherein the grounding resistor and the compensation resistor are both non-linear resistors; The front end of the grounding resistor is connected to the neutral point through a fuse, the rear end of the grounding resistor is connected in series with the small resistor and then grounded, and the self-healing capacitor and the compensation resistor are connected in series and in parallel with the small resistor in sequence; In the conventional protection state and the resonance protection state, the connection relationship of the grounding protection part remains unchanged; In the arc extinguishing protection state, the self-healing capacitor and the compensation resistor are disconnected from the grounding protection part; In the overvoltage protection state, the small resistor is disconnected from the grounding protection part; In the overvoltage protection state, the small resistor is disconnected from the grounding protection part, and the self-healing capacitor is in a short-circuit state.

10. A high voltage and high energy nonlinear adaptive power grid protection system according to claim 9, characterized in that: The grounding protection unit further includes a discharge mechanism, which is connected in parallel to the self-healing capacitor; In the resonance protection state, the discharge frequency of the discharge mechanism is linked with the resonance frequency to suppress ferromagnetic resonance and accelerate energy discharge.

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