A high-voltage high-energy non-linear adaptive power grid protection method and system

Abstract

The present invention relates to the technical field of power equipment, and discloses a high-voltage and high-energy non-linear adaptive power grid protection method and system. Different threshold coefficients are determined according to the waveform category of the residual current and the limit amplitude within the time window to obtain the actual threshold. The real-time data is compared with the actual threshold, and different protection states are entered according to the comparison result. At the same time, the voltage change rate is judged, and when the voltage change rate is greater than the set value, the protection state is changed. The present invention provides a high-voltage and high-energy non-linear adaptive power grid protection method and system, which can solve or at least mitigate the problem that the existing power grid protection method is not applicable to a high-proportion new energy power grid with large fluctuations and is prone to misjudgment and disconnection of power generation equipment due to voltage fluctuations.

Description

Technical Field

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

[0002] At present, ungrounded systems are generally adopted in distribution networks. Although the power supply reliability is improved, once a fault occurs, due to the lack of effective suppression measures, overvoltage is extremely likely to damage equipment and even threaten personal safety. 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 adopted to protect the safety of the power grid. After a single-phase grounding fault occurs, there is no obvious short-circuit current, and it can operate with power for two hours. Generally, the grounding line selection technology is used for treatment. 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 rise and develop into an interphase short circuit. After two-phase and three-phase faults occur, a large short-circuit current will be generated.

[0004] However, conventional neutral point grounding protection has low applicability in high-proportion new energy power grids (such as wind power and photovoltaic access scenarios). Due to the characteristics of new energy such as volatility, harmonic interference, and high failure rate in the power grid, higher requirements are put forward for power grid protection. The grid-connected voltage itself fluctuates greatly, and when a fault occurs in the equipment or lightning strikes, the voltage fluctuation is aggravated. Therefore, conventional protection methods are prone to misjudgment, resulting in equipment disconnection from the grid, and the resonance duration is relatively long, 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 a distribution line in a non-effectively grounded neutral point system, including: performing fault phase selection based on the power frequency electrical quantities of the distribution line monitored in real time to determine the fault type; using the fault type to selectively input protection measures for the distribution line such as single-phase grounding protection, two-phase grounding short-circuit protection, and three-phase short-circuit protection; when a single-phase grounding fault occurs, input the traveling wave protection based on the initial traveling wave polarity of the zero-mode voltage and current; when a two-phase grounding short-circuit fault occurs, input the non-channel protection based on the power frequency current and voltage information and the sudden change information of the sound-phase current; when a three-phase short-circuit fault occurs, input the small differential overcurrent protection using a fast circuit breaker. This invention determines the fault type through power frequency electrical quantities 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, there will be misjudgment of faults and isolation. Isolation means disconnection from the grid. Although the safety of the power grid is guaranteed, unnecessary disconnection from the grid will cause certain economic losses. Summary of the Invention

[0006] The object 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 methods are not applicable to high-proportion new energy power grids with large fluctuations, and provide a high-voltage and high-energy non-linear adaptive power grid protection method and system.

[0007] To achieve the above object, the present invention provides the following technical solutions: A high-voltage and high-energy non-linear adaptive power grid protection method, comprising the following steps:

[0008] S1. A current transformer and a voltage transformer monitor the waveform data of the residual current, as well as the real-time voltage and real-time current of the neutral point;

[0009] S2. Determine different threshold coefficients according to the waveform category of the residual current and the limit amplitude within the time window;

[0010] S3. Multiply the threshold coefficient obtained in step S2 by the corresponding determination threshold to obtain the actual threshold;

[0011] S4. Compare the data monitored in step S1 with the actual threshold in step S3, and enter different protection states according to the comparison result;

[0012] 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.

[0013] To further implement the present invention, the following technical solutions can be preferably selected:

[0014] Preferably, in step S1, the waveform category is determined by the ratio of the shorter duration to the longer duration of the positive and negative residual currents in the residual current waveform;

[0015] 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; when the ratio is 0 - 0.4, it is determined as a distorted wave.

[0016] Preferably, when the waveform category is a sine wave and the limit amplitude within the time window is greater than the first determination value, change the threshold coefficient;

[0017] When the waveform category is a distorted wave and the limit amplitude within the time window is greater than the second determination value, change the threshold coefficient;

[0018] When the waveform category is a half-wave and the amplitude within the time window is stable, change the threshold coefficient;

[0019] 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.

[0020] Preferably, in the step S3, the determination thresholds include a first voltage threshold, a second voltage threshold, and a first current threshold, and the first voltage actual threshold, the second voltage actual threshold, and the first current actual threshold are obtained by multiplying the first voltage threshold, the second voltage threshold, and the first current threshold by a threshold coefficient respectively.

[0021] Preferably, the step S4 includes the following steps:

[0022] 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;

[0023] S402. Compare the real-time current monitored by the current transformer with the first current actual threshold. When the real-time current is less than the first current actual threshold, enter the normal protection state. When the real-time current is greater than the first current actual threshold, enter the resonance protection state;

[0024] S403. Compare the real-time current monitored by the current transformer with the first current actual threshold. When the real-time current is less than the first current actual threshold, enter the arc extinction protection state. When the real-time current is greater than the first current actual threshold, enter the overvoltage protection state.

[0025] Preferably, the step S5 includes the following steps:

[0026] 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 rates of each time window in turn;

[0027] S52. Compare 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, enter step S53. When the voltage change rates of the multiple time windows are all positive and all exceed the set value, enter step S54;

[0028] S53. Maintain the protection state in step S4;

[0029] S54. Change the protection state determined in step S4 to the overvoltage protection state, and enter step S55;

[0030] S55. Maintain the overvoltage protection state in the protection state within the first subsequent time window;

[0031] S56. The protection status within the subsequent second time window is changed according to the voltage change rates within the subsequent first time window and the second time window.

[0032] Preferably, step 56 includes the following steps:

[0033] S561. Determine the positive or negative status of the voltage change rate within the subsequent first time window. If the voltage change rate is positive, proceed to step S562a; if the voltage change rate is negative, proceed to step S562b.

[0034] S562a. Determine the positive or negative status of the voltage change rate within the subsequent second time window. If the voltage change rate is positive, maintain the overvoltage protection status; if the voltage change rate is negative, proceed to step S563a.

[0035] S562b. Determine the positive or negative status of the voltage change rate within the subsequent second time window. If the voltage change rate is negative, change the protection status to the protection status determined in step S4; if the voltage change rate is positive, proceed to step S563b.

[0036] 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 status; if the absolute value of the voltage change rate is greater than the set value, change to the protection status determined in step S4.

[0037] 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 status; if the absolute value of the voltage change rate is less than the set value, change to the protection status determined in step S4.

[0038] Preferably, while performing steps S52 - S56 in step S5, the following steps are also performed:

[0039] S57. Monitor the voltage boost value within the time window. When the boost value is greater than the warning threshold, change the protection status to the overvoltage protection status.

[0040] A high - voltage and high - energy non - linear adaptive power grid protection system, which adopts a high - voltage and high - energy non - linear adaptive power grid protection method. The power grid protection system includes a grounding protection part, and the grounding protection part includes a grounding resistor, a small resistor, a compensating resistor, and a self - healing capacitor. Both the grounding resistor and the compensating resistor are non - linear resistors;

[0041] The front end of the grounding resistor is connected to the neutral point through a fuse, the rear end of the grounding resistor is grounded after being connected in series with the small resistor, and the self - healing capacitor and the compensating resistor are connected in series in sequence and are connected in parallel with the small resistor;

[0042] During the normal protection status and the resonance protection status, the connection relationship of the grounding protection part remains unchanged;

[0043] In the arc extinguishing protection state, the self-healing capacitor and the compensating resistor are disconnected from the grounding protection part;

[0044] In the overvoltage protection state, the small resistor is disconnected from the grounding protection part;

[0045] 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.

[0046] Preferably, the grounding protection part further includes a discharging mechanism, and the discharging mechanism is connected in parallel with the self-healing capacitor;

[0047] In the resonance protection state, the discharging frequency of the discharging mechanism is linked with the resonance frequency to suppress ferroresonance and accelerate energy dissipation.

[0048] The beneficial effects of the present invention are as follows:

[0049] 1. The present invention distinguishes the power grid state through the residual current waveform recognition technology, dynamically adjusts the actual threshold according to the waveform type, and enters the protection states of different scenarios according to the actual threshold, improving the accuracy of the protection action, reducing the misjudgment rate on the premise of ensuring the equipment safety, and reducing the disconnection rate of the equipment.

[0050] 2. The present invention determines the rate of change of voltage, thereby correcting the protection state, predicting the voltage fluctuation, and adjusting the protection state in combination with the output characteristics of the new energy power grid to ensure the equipment safety.

[0051] 3. The grounding protection part of the present invention makes matching adjustments according to different protection states, which can not only play a better protection role, but also improve the accuracy of fault isolation. Brief Description of the Drawings

[0052] Figure 1 It is a flowchart of the protection method of the present invention.

[0053] Figure 2 It is a flowchart of step S4 of the present invention.

[0054] Figure 3 It is a flowchart of step S5 of the present invention.

[0055] Figure 4 It is a flowchart of step S56 of the present invention. Detailed Embodiments

[0056] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "installed", "connected", and "coupled" 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0057] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0058] Embodiment 1

[0059] Conventional neutral point grounding protection has low applicability in a high-proportion new energy power grid (such as wind power and photovoltaic access scenarios). Due to the characteristics of new energy such as volatility, harmonic interference, and high failure rate, higher requirements are put forward for power grid protection. The grid-connected voltage itself fluctuates greatly, and when a fault occurs in the equipment or lightning strikes occur, the voltage fluctuation is aggravated. Therefore, conventional protection methods are prone to misjudgment, resulting in equipment disconnection from the grid, and the resonance duration is relatively long, which is more likely to cause equipment damage.

[0060] This embodiment discloses a high-voltage and high-energy non-linear adaptive power grid protection system. The power grid protection system includes a grounding protection part, and the grounding protection part includes a grounding resistor, a small resistor, a compensation resistor, and a self-healing capacitor, and both the grounding resistor and the compensation resistor are non-linear resistors.

[0061] The front end of the grounding resistor is connected to the neutral point through a fuse, and the rear end of the grounding resistor is grounded after being connected in series with the small resistor. The self-healing capacitor and the compensation resistor are connected in series in sequence and are connected in parallel with the small resistor.

[0062] In the normal protection state and the resonance protection state, the connection relationship of the grounding protection part remains unchanged; when operating normally, the neutral point voltage is very low, the grounding resistor is in a high-resistance state, and the current flowing through it is very small, basically in an open-circuit state, which is equivalent to not being grounded, and has the characteristics of high power supply reliability and good safety in the ungrounded mode. When resonance occurs, the huge energy capacity of the grounding resistor quickly absorbs the resonance energy, while the small resistor provides additional damping. The self-healing capacitor is connected in parallel with the small resistor 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 ferroresonance and broken-line resonance overvoltages; the current passing through the fuse in this state is small, and the fuse is not easily burned out.

[0063] In the arc extinguishing protection state, the self-healing capacitor and the compensation resistor are disconnected from the grounding protection part. The grounding resistor timely absorbs the grounding charge energy and limits the arc path recovery voltage, promoting the rapid extinction of the arc. The small resistor shortens the reignition time by discharging the residual charge. The current passing through the fuse in this state is not high, reducing the probability of the fuse blowing, and at the same time quickly extinguishing the arc to ensure the safety of equipment and the power grid.

[0064] In the overvoltage protection state, the small resistor is disconnected from the grounding protection part, and the neutral point voltage will rise simultaneously. After absorbing energy, the grounding resistor becomes conductive and limits the voltage within the set range. The disconnection of the small resistor avoids burning. 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 voltage and accelerating the energy discharge. The current passing through the fuse in this state is relatively high. By means of the self-healing capacitor and the compensation resistor, the current fluctuation is avoided from rising and causing the fuse to directly disconnect, reducing the probability of the fuse blowing. On the premise of ensuring the safety of equipment and the power grid, the probability of accidental disconnection of the power generation equipment is reduced.

[0065] 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, avoiding the burning of the small resistor. The current passing through the fuse in this state is high. The grounding resistor and the compensation resistor quickly absorb energy to ensure that the overvoltage of the system is limited below 2 times, avoiding equipment damage. At the same time, the current can rise rapidly and quickly blow the fuse to isolate the equipment from the power grid.

[0066] In addition, the grounding protection part further includes a discharge mechanism, which is connected in parallel with the self-healing capacitor. In the resonance protection state, the discharge frequency of the discharge mechanism is linked with the resonance frequency to suppress ferroresonance and accelerate energy discharge.

[0067] The grounding protection part of the present invention makes matching adjustments according to different protection states, which can not only play a better protection role, but also improve the accuracy of fault isolation and reduce the misjudgment and disconnection of the power generation equipment due to voltage fluctuation.

[0068] Embodiment 2

[0069] Existing power grid protection methods selectively isolate the fault point for different fault types to improve 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, there will be misjudgment of faults and isolation. Isolation means disconnection from the grid. Although the safety of the power grid is ensured, unnecessary disconnection will cause certain economic losses.

[0070] Refer to Figures 1-4 , a high-voltage and high-energy non-linear adaptive power grid protection method, including the following steps:

[0071] S1. The current transformer and voltage transformer monitor the waveform data of the residual current, as well as the real-time voltage and real-time current of the neutral point;

[0072] S2. Determine different threshold coefficients according to the waveform category of the residual current and the extreme amplitude within the time window;

[0073] S3. Multiply the threshold coefficient obtained in step S2 by the corresponding determination threshold to obtain the actual threshold;

[0074] S4. Compare the data monitored in step S1 with the actual threshold in step S3, and enter different protection states according to the comparison result;

[0075] 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.

[0076] Specifically, in step S1, the waveform category is determined by the ratio of the shorter duration to the longer duration of the positive and negative residual currents in the residual current waveform;

[0077] 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; when the ratio is 0 - 0.4, it is determined as a distorted wave.

[0078] When the waveform category is a sine wave and the extreme amplitude within the time window is greater than the first determination value, change the threshold coefficient;

[0079] When the waveform category is a distorted wave and the extreme amplitude within the time window is greater than the second determination value, change the threshold coefficient;

[0080] When the waveform category is a half wave and the amplitude is stable within the time window, change the threshold coefficient;

[0081] 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;

[0082] In this embodiment, the threshold coefficient when the waveform category is a sine wave is 0.9 - 1, the threshold coefficient when the waveform category is a distorted wave is 0.75 - 0.9, and the threshold coefficient when the waveform category is a half wave is 0.6 - 0.75.

[0083] Specifically, in step S3, the determination thresholds include a first voltage threshold, a second voltage threshold, and a first current threshold. The first voltage threshold, the second voltage threshold, and the first current threshold are respectively multiplied by the threshold coefficient to obtain a first voltage actual threshold, a second voltage actual threshold, and a first current actual threshold.

[0084] Refer to Figure 2, step S4 includes the following steps:

[0085] S401. Compare the real-time voltage monitored by the voltage transformer with the first actual voltage threshold and the second actual voltage threshold. When the real-time voltage is greater than the second actual voltage threshold, enter the overvoltage guarantee state. When the real-time voltage is less than the first actual voltage threshold, enter step S402. When the real-time voltage is greater than the first actual voltage threshold and less than the second actual voltage threshold, enter step S403;

[0086] S402. Compare the real-time current monitored by the current transformer with the first actual current threshold. When the real-time current is less than the first actual current threshold, enter the conventional protection state. When the real-time current is greater than the first actual current threshold, enter the resonance protection state;

[0087] S403. Compare the real-time current monitored by the current transformer with the first actual current threshold. When the real-time current is less than the first actual current threshold, enter the arc extinction protection state. When the real-time current is greater than the first actual current threshold, enter the overvoltage protection state.

[0088] The present invention distinguishes the power grid state through the residual current waveform recognition technology, dynamically adjusts the actual threshold according to the waveform type, and enters the protection states of different scenarios according to the actual threshold, improving the accuracy of the protection action, reducing the misjudgment rate on the premise of ensuring the equipment safety, and reducing the off-grid rate of the equipment.

[0089] The present invention also determines the rate of change of voltage, thereby correcting the protection state, predicting the voltage fluctuation, and adjusting the protection state in combination with the output characteristics of new energy to ensure the equipment safety.

[0090] Embodiment III

[0091] Optimize the determination of the rate of change of voltage according to the output characteristics of the new energy power grid, so as to adjust the protection state more accurately according to the voltage fluctuation.

[0092] Refer to Figure 3 , step S5 includes the following steps:

[0093] S51. Monitor the real-time voltage through the voltage transformer, and obtain the rate of change of voltage in the current time window, and record the rate of change of voltage in each time window in turn;

[0094] S52. Compare the rate of change of voltage in the current time window with the rate of change of voltage in multiple previous time windows. When the rate of change of voltage in multiple time windows is not all positive and does not all exceed the set value, enter step S53. When the rate of change of voltage in multiple time windows is all positive and all exceed the set value, enter step S54;

[0095] S53. Maintain the protection status in step S4;

[0096] S54. Change the protection status determined in step S4 to overvoltage protection status, and enter step S55;

[0097] S55. Maintain the overvoltage protection status within the first subsequent time window;

[0098] S56. Change the protection status within the second subsequent time window according to the voltage change rates within the first and second subsequent time windows.

[0099] Refer to Figure 4 , in order to more accurately determine whether the fluctuation has ended after adjusting the protection status, so as to reduce the misjudgment probability, step 56 includes the following steps:

[0100] S561. Judge the positive or negative state of the voltage change rate within the first subsequent time window. If the voltage change rate is positive, enter step S562a; if the voltage change rate is negative, enter step S562b;

[0101] S562a. Judge the positive or negative state of the voltage change rate within the second subsequent time window. If the voltage change rate is positive, maintain the overvoltage protection status; if the voltage change rate is negative, enter step S563a;

[0102] S562b. Judge the positive or negative state of the voltage change rate within the second subsequent time window. If the voltage change rate is negative, change the protection status to the protection status determined in step S4; if the voltage change rate is positive, enter step S563b;

[0103] S563a. Judge 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 status; if the absolute value of the voltage change rate is greater than the set value, change to the protection status determined in step S4;

[0104] S563b. Judge 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 status; if the absolute value of the voltage change rate is less than the set value, change to the protection status determined in step S4.

[0105] In order to avoid damage to the equipment and the power grid caused by accidental instantaneous faults, the following steps are also carried out while performing steps S52 - S56 in step S5:

[0106] S57. Monitor the voltage boost value within the time window. When the boost value is greater than the warning threshold, change the protection status to overpressure protection status.

[0107] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A high-voltage high-energy non-linear adaptive power grid protection method, characterized in that, It includes the following steps: S1. The current transformer and voltage transformer monitor the waveform data of the residual current, as well as the real-time voltage and real-time current of the neutral point; S2. Determine different threshold coefficients according to the waveform category of the residual current and the limit amplitude within the time window; S3. Multiply the threshold coefficient obtained in step S2 by the corresponding judgment threshold. The judgment thresholds include the first voltage threshold, the second voltage threshold, and the first current threshold. The first voltage threshold, the second voltage threshold, and the first current threshold are respectively multiplied by the threshold coefficient to obtain the first actual voltage threshold, the second actual voltage threshold, and the first actual current threshold; S4. Compare the data monitored in step S1 with the actual thresholds in step S3, and enter different protection states according to the comparison results; S5. While performing steps S2 and S3, judge the voltage change rate. When the voltage change rate is greater than the set value, change the protection state in S4; The step S4 includes the following steps: S401. Compare the real-time voltage monitored by the voltage transformer with the first actual voltage threshold and the second actual voltage threshold. When the real-time voltage is greater than the second actual voltage threshold, enter the overvoltage protection state. When the real-time voltage is less than the first actual voltage threshold, enter step S402. When the real-time voltage is greater than the first actual voltage threshold and less than the second actual voltage threshold, enter step S403; S402. Compare the real-time current monitored by the current transformer with the first actual current threshold. When the real-time current is less than the first actual current threshold, enter the normal protection state. When the real-time current is greater than the first actual current threshold, enter the resonance protection state; S403. Compare the real-time current monitored by the current transformer with the first actual current threshold. When the real-time current is less than the first actual current threshold, enter the arc extinction protection state. When the real-time current is greater than the first actual current threshold, enter the overvoltage protection state.

2. The high-voltage high-energy non-linear adaptive power grid protection method according to claim 1, wherein, When the waveform category is a sine wave and the limit amplitude within the time window is greater than the first judgment value, change the threshold coefficient; When the waveform category is a distorted wave and the limit amplitude within the time window is greater than the second judgment value, change the threshold coefficient; When the waveform category is a half wave and the amplitude within the time window is stable, change the threshold coefficient; 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.

3. A high-voltage high-energy non-linear adaptive power grid protection method according to claim 1, characterized in that The step S5 includes 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 rates of each time window in turn; S52. Compare 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, enter step S53. When the voltage change rates of the multiple time windows are all positive and all exceed the set value, enter step S54; S53. Maintain the protection state in step S4; S54. Change the protection state determined in step S4 to the overvoltage protection state, and enter step S55; S55. Maintain the overvoltage protection state within the first subsequent time window; S56. Change the protection state within the second subsequent time window according to the voltage change rates within the first and second subsequent time windows.

4. A high-voltage high-energy non-linear adaptive power grid protection method according to claim 3, characterized in that Step 56 includes the following steps: S561. Determine the positive or negative state of the voltage change rate within 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. Determine the positive or negative state of the voltage change rate within the second subsequent time window. If the voltage change rate is positive, maintain 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 within the second subsequent time window. If the voltage change rate is negative, change the protection state 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.

5. The high-voltage and high-energy non-linear adaptive power grid protection method according to claim 3, characterized in that While performing steps S52 - S56 in step S5, the following steps are also performed: S57. Monitor the voltage boost value within the time window. When the boost value is greater than the warning threshold, change the protection state to the overvoltage protection state.

6. A high-voltage high-energy non-linear adaptive power grid protection system, which is applicable to the high-voltage high-energy non-linear adaptive power grid protection method as described in any one of claims 3-5, and is characterized in that, The power grid protection system includes a grounding protection unit, and the grounding protection unit includes a grounding resistor, a small resistor, a compensating resistor, and a self-healing capacitor. Both the grounding resistor and the compensating resistor are non-linear resistors; The front end of the grounding resistor is connected to the neutral point through a fuse, and the rear end of the grounding resistor is grounded in series with the small resistor. The self-healing capacitor and the compensating resistor are connected in series in sequence and are connected in parallel with the small resistor; During the normal protection state and the resonance protection state, the connection relationship of the grounding protection unit remains unchanged; During the arc extinction protection state, the self-healing capacitor and the compensating resistor are disconnected from the grounding protection unit; During the overvoltage protection state, the small resistor is disconnected from the grounding protection unit; During the overvoltage protection state, the small resistor is disconnected from the grounding protection unit, and the self-healing capacitor is in a short-circuit state.

7. An ultra-high voltage and high energy non-linear adaptive power grid protection system according to claim 6, wherein The grounding protection unit further includes a discharge mechanism, and the discharge mechanism is connected in parallel with the self-healing capacitor; During the resonance protection state, the discharge frequency of the discharge mechanism is linked with the resonance frequency to suppress ferroresonance and accelerate energy dissipation.

Images