A grassland power distribution line grounding judgment ability improving forest fire early warning method

Abstract

The application discloses a grassland distribution line grounding judgment ability improved forest fire early warning method and relates to the field of distribution network fault monitoring. The method comprises the following steps: obtaining a zero sequence voltage recording file based on a monitoring device; obtaining a first recording file grouping based on a distribution trunk grouping zero sequence voltage recording file, obtaining a first time of the first recording file grouping, obtaining a hidden danger event based on the first time and a first preset time range, and obtaining a hidden danger recording file of the hidden danger event; grouping the hidden danger recording file based on a preset zero sequence voltage range and a second preset time range to obtain a second recording file grouping, obtaining an out-of-area hidden danger point and an in-area hidden danger point based on recording data of the second recording file grouping; and obtaining early warning information based on the out-of-area hidden danger point and the in-area hidden danger point, which can solve the problem that the current single-phase grounding fault monitoring method of a grassland distribution network line can only reduce line electrical faults by quickly isolating single-phase grounding faults and cannot monitor line faults in advance.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault monitoring, specifically to a wildfire early warning method that improves the ability to determine grounding of power distribution lines in grasslands. Background Technology

[0002] Wildfires are a significant factor threatening ecological security, not only destroying natural resources but also endangering people's lives and property. With the continuous expansion of power distribution networks, power lines and cables traverse grasslands and forests, increasing the risk of wildfires. For a long time, power sectors and research institutions have conducted extensive research on the impact of wildfires on power lines and grid operations, resulting in a technical system for wildfire monitoring, early warning, and response.

[0003] Currently, power distribution lines crossing grasslands primarily rely on rapid isolation of single-phase ground faults to prevent fires caused by electrical faults. While rapid ground fault isolation can reduce the risk of fires caused by electrical issues, it only minimizes the damage after a fault occurs, not prevents it from happening altogether. Especially for lines operating long-term across grassland and forest areas, fires caused by tree-line connections or the gradual deterioration of line insulation leading to heat buildup are difficult to detect in the early stages of the fault. Summary of the Invention

[0004] To address the issue that current methods for monitoring single-phase grounding faults in power distribution lines crossing grasslands can only reduce electrical faults by quickly isolating single-phase grounding faults, but cannot detect faults in advance, this invention provides a wildfire early warning method that improves the grounding analysis capability of grassland power distribution lines. The method includes:

[0005] S1. Install monitoring equipment to key nodes of the distribution network lines to obtain the topology of the distribution network;

[0006] S2. Based on the monitoring equipment, obtain the line waveform recording file, filter the line waveform recording file, and obtain the zero-sequence voltage waveform recording file;

[0007] S3. Based on the power distribution trunk line, the zero-sequence voltage waveform file is grouped to obtain several first waveform file groups, the first time of the first waveform file group is obtained, the hidden danger event is obtained based on the first time and the first preset time range, and the hidden danger waveform file of the hidden danger event is obtained.

[0008] S4. Based on a preset zero-sequence voltage range and a second preset time range, the hidden danger recording files are grouped to obtain several second recording file groups. Based on the recording data of the second recording file groups, hidden danger points outside the area and hidden danger points inside the area are obtained, and the hidden danger points outside the area and the hidden danger points inside the area are marked.

[0009] S5. Based on the topology map, the hidden danger points outside the area and the hidden danger points inside the area, obtain several hidden danger areas, and obtain early warning information based on the hidden danger areas.

[0010] Within the zone, potential hazards refer to those where the current monitoring equipment's power direction is outward, while outside the zone, potential hazards refer to those where the current monitoring equipment's power direction is inward.

[0011] This invention uses a substation master station system as the carrier and monitoring equipment with waveform recording capabilities as nodes. By uploading waveform files from each key node to the master station, it focuses on the frequent transient fault characteristics before a permanent grounding fault occurs, i.e., a significant increase in zero-sequence voltage after a grounding fault. Only waveform files generated by sudden changes or exceeding limits in zero-sequence voltage are acquired. It targets more concealed grounding faults such as high-resistance grounding of distribution lines crossing forest areas and tree-line connections. Waveform files from the same trunk line are grouped together, and waveform files within the same time range are classified as potential incidents. Based on the magnitude and duration of the zero-sequence voltage, different grounding protection algorithms are used to process potential incidents, determine the direction of the incident, and thus obtain the potential incident area. The severity of the warning is represented by the number of fault segments per unit time. This allows for the early detection of wildfire hazards, effectively reducing wildfires caused by power outages. Further, in step S4, if the preset zero-sequence voltage range is a first voltage range and the second preset time range is a first time range, then a first zero-sequence voltage mutation point is obtained based on the second waveform file grouping; based on the first zero-sequence voltage mutation point, the zero-sequence voltage and zero-sequence current within a first preset period are obtained; the voltage value of the zero-sequence voltage and the current value of the zero-sequence current are obtained; and based on the voltage value and the current value, the external hidden danger point and the internal hidden danger point are obtained.

[0012] Further, in step S4, if the preset zero-sequence voltage range is the second voltage range and the second preset time range is the second time range, then the second zero-sequence voltage mutation point is obtained based on the second waveform file grouping. Based on the second zero-sequence voltage mutation point, several sampling points within the second preset period are obtained. The zero-sequence active power and zero-sequence reactive power of the sampling points are obtained. The zero-sequence active power and the zero-sequence reactive power are added together to obtain the total zero-sequence active power and the total zero-sequence reactive power. Based on the total zero-sequence active power and the total zero-sequence reactive power, the hidden danger points outside the area and the hidden danger points inside the area are obtained.

[0013] By summing the zero-sequence active power and zero-sequence reactive power of a single sampling point, and integrating the subtle grounding fault characteristics of high-resistance grounding within a unit of time, hidden and potential grounding characteristics can be revealed, allowing for a more accurate determination of the direction of potential hazards.

[0014] Furthermore, in step S5, based on the hidden danger area and preset rules, early warning information is obtained. The preset rules are: different scoring periods are preset, and each scoring period corresponds to an early warning threshold and an early warning level; based on the preset score and the scoring period, the hidden danger score of the hidden danger area is obtained; based on the hidden danger score and the early warning threshold, the early warning level is obtained; and based on the early warning level, the early warning information is obtained.

[0015] Setting different warning cycles can provide different levels of fault warnings, improving the timeliness and accuracy of warnings.

[0016] Considering a typical balanced line load, the zero-sequence voltage will be below 500V. A ground fault may occur when the voltage exceeds 1000V, with a duration of less than 40ms (less than two cycles), constituting an instantaneous ground fault. This is generally caused by tree branches occasionally touching the line under wind conditions, potentially leading to a high-voltage arc igniting the trees. For medium-to-low resistance ground faults, the zero-sequence voltage is generally above 12kV. If the zero-sequence voltage is between 1 and 8kV and persists for a long period, it is considered a high-resistance ground fault. In forests with this type of fault, although the fault current is relatively small, long-term heat accumulation still poses a risk of igniting shrubs. Therefore, this method classifies faults based on the following two ranges.

[0017] Furthermore, the first voltage range is greater than 1kV, and the first time range is less than 40ms; the second voltage range is greater than or equal to 1kV and less than or equal to 8kV, and the second time range is the time from the start of recording to the end of recording in the hidden danger recording file.

[0018] Furthermore, the specific steps for obtaining the external hidden danger points and the internal hidden danger points based on the voltage value and the current value include: obtaining the first-order difference value of the voltage value; if both the first-order difference value and the current value are positive or negative, then the monitoring device is an external hidden danger point; if neither the first-order difference value nor the current value are positive or negative, then the monitoring device is an internal hidden danger point.

[0019] Furthermore, the specific steps for obtaining the external hidden danger points and the internal hidden danger points based on the total zero-sequence active power and the total zero-sequence reactive power include: if the total zero-sequence active power is less than 0, then the monitoring device is an internal hidden danger point; if the total zero-sequence active power is greater than or equal to 0 and the total zero-sequence reactive power is less than 0, then the monitoring device is an external hidden danger point.

[0020] The zero-sequence power direction method calculates the power criterion within a unit time based on a single sampling point to identify the fault. However, high-resistance grounding faults have relatively small fault currents, and the power calculated from a single sampling point is insufficient to meet the power criterion requirements. Therefore, this method determines the fault direction by integrating the sampling point over a unit time, thus improving the accuracy of the determination.

[0021] Furthermore, the first calculation formula for obtaining the total zero-sequence active power is:

[0022]

[0023] The second calculation formula for obtaining the total zero-sequence reactive power is:

[0024]

[0025] in, Represents zero-sequence voltage. Represents zero-sequence current. Indicates the zero-sequence voltage angle. ∠Z represents the zero-sequence current angle, ∠Z represents the zero-sequence impedance angle, P0_total represents the total zero-sequence active power, Q0_total represents the total zero-sequence reactive power, i represents the i-th sampling point, and n represents the number of sampling points.

[0026] Furthermore, if the effective value of the zero-sequence current at the potential hazard point in the area is less than a preset current threshold, then the marker of the potential hazard point in the area is deleted.

[0027] To ensure the accuracy of the judgment results, a lower limit value for the zero-sequence current is set. The maximum effective value of the waveform zero-sequence current that is judged as an internal grounding fault should be greater than this value. If it is less than this value, it will not participate in the early warning. This reduces the problem that the accuracy will not meet the requirements due to the zero-sequence current being too small, thus affecting the algorithm's judgment.

[0028] Considering that branches on both sides of the road in the forest area will grow in spring, and the newly grown branches may overlap the road, causing line failure, this method predicts the growth direction of branches in real time by using continuous growth images of branches within a certain time range. It obtains the real-time growth rate of the current branches by using the length of the branches that have grown, the changing diameter of the branches, and the growth time of the current branches. Then, it infers the growth rate of different types of branches at different diameters. Combining the growth rate and diameter, it predicts the maximum growth length. By combining the growth direction and the maximum growth length, it judges whether the branches will overlap the road, thereby providing an early warning for the affected branch areas, pruning them, reducing the occurrence of line failures, and further reducing the occurrence of wildfires.

[0029] Furthermore, the method also includes:

[0030] The system acquires forest area images, obtains a first distance between tree branches and a road based on the forest area images, and identifies dangerous areas based on a preset distance range and the first distance. It then acquires dangerous branches within the dangerous areas, obtains the branch tips of the dangerous branches, obtains the branch diameter of the branch tips, acquires branch images of the dangerous branches within a preset time range, and obtains the growth diameter based on the branch images. It acquires a first line from the branch images, predicts the growth direction of the dangerous branches based on the first line, obtains the growth length based on the first line, obtains a first growth rate based on the growth diameter, the growth length, and the preset time range, and presets a second growth rate for the dangerous branches under different branch diameters based on the first growth rate. It predicts the longest growth length of different types of branches based on the second growth rate and the branch diameter, and obtains a danger warning based on the preset danger direction, the longest growth length, and the growth direction.

[0031] This system captures only branches in hazardous areas, reducing the number of branches to be monitored and enabling faster early warning responses. It captures the real-time growth of different types of branches at different times from continuous images, showing changes in their morphology, appearance, weather, and growing environment. Through image comparison, it obtains the real-time growth direction, speed, and diameter of different types of branches, prioritizing the longest growth length along a straight line in the current direction (the longest growth length without change). If the predicted length exceeds the hazardous area, an early warning is issued, reducing the difficulty in calculating branch lengths after changes in morphology and appearance, and ensuring timely warnings. It comprehensively considers changes in branch type, size, and shape, and can capture changes even with human and animal interference, thus achieving accurate hazard warnings.

[0032] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0033] 1. This invention uses a substation master station system as the carrier and monitoring equipment with waveform recording function as nodes. By uploading waveform files of each key node to the master station, it is based on the frequent transient fault characteristics before the occurrence of permanent grounding faults. After the occurrence of a grounding fault, the zero-sequence voltage will increase significantly. Therefore, only waveform files generated by sudden changes or exceeding limits of zero-sequence voltage are acquired. It targets relatively hidden grounding faults such as high-resistance grounding of distribution lines crossing forest areas and tree-line splicing. The waveform files of the same trunk line are grouped together, and the waveform files of the same time range are classified as hidden danger events. According to the magnitude and duration of zero-sequence voltage, different grounding protection algorithms are used to process hidden danger events, determine the direction of the hidden danger, and thus obtain the hidden danger area. The fault segment count per unit time is used to represent the degree of crisis of the warning. It can detect wildfire hazards in the early stage of fault occurrence and effectively reduce wildfires caused by power failures.

[0034] 2. The zero-sequence active power and zero-sequence reactive power of a single sampling point are accumulated separately. By integrating the subtle grounding fault characteristics of high-resistance grounding within a unit of time, hidden and potential grounding characteristics are revealed, and the direction of potential hazards can be determined more accurately.

[0035] 3. Based on the potential hazard area and preset rules, early warning information is obtained, and different early warning cycles can be set to provide different levels of fault warnings, thereby improving the timeliness and accuracy of early warnings.

[0036] 4. Danger warnings are obtained based on branch diameter, growth direction, and growth rate. By predicting the growth direction, growth rate, and maximum growth length of branches, it is determined whether they will overlap with the power line, thereby issuing a warning for the branch area and pruning it to reduce the occurrence of power line failures, and further reducing the occurrence of wildfires. Attached Figure Description

[0037] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0038] Figure 1 This is a flowchart illustrating a wildfire early warning method for improving the grounding assessment capability of grassland power distribution lines, as described in this invention.

[0039] Figure 2 This is a flowchart illustrating the process of obtaining potential hazard points both outside and inside the area.

[0040] Figure 3 This is a schematic diagram showing that the first-order difference value and the current value are opposite in this invention. Detailed Implementation

[0041] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0042] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0043] Example 1

[0044] refer to Figures 1-3 This embodiment provides a wildfire early warning method to improve the grounding judgment capability of grassland power distribution lines. The method includes:

[0045] S1. Install monitoring equipment to key nodes of the distribution network line and obtain the topology map of the distribution network; In this embodiment, the monitoring equipment can be a primary and secondary fusion terminal device with waveform recording function. The primary and secondary fusion terminal device can identify electrical characteristic quantities (zero-sequence voltage) and waveform recording files generated by transgressive waveform recording changes.

[0046] Key nodes can be substation outgoing points, branch line connection points, line sectionalizing switches, important user access points, and cable and overhead line conversion points, etc., because these locations are critical for power distribution, diversion, and fault isolation, which are related to the reliability and balance of power supply. In addition, some nodes involve special protection needs or are prone to failure and difficult to maintain, which are crucial to the smooth operation of the distribution network. Therefore, they are selected as key nodes.

[0047] S2. Based on the monitoring equipment, obtain the line waveform file, filter the line waveform file to obtain the zero-sequence voltage waveform file; the zero-sequence voltage is very small and almost zero during normal operation of the distribution network, but the zero-sequence voltage will increase significantly after a ground fault occurs. Therefore, only obtain the waveform file generated by the sudden change or over-limit of the zero-sequence voltage channel characteristic value. The over-limit value can be set to 0.5~1kV, which can be determined according to the line load imbalance and the degree of high resistance to be identified.

[0048] A waveform recording typically contains eight analog data channels and one status data channel. The eight analog data channels represent the three-phase voltages and currents (A, B, and C), as well as the zero-sequence voltage and zero-sequence current. The characteristic value of the zero-sequence voltage channel refers to the sampled value of the zero-sequence voltage recorded in the waveform recording file.

[0049] S3. Group the zero-sequence voltage waveform files based on the power distribution trunk line to obtain several first waveform file groups, obtain the first time of the first waveform file group, obtain the hidden danger event based on the first time and the first preset time range, and obtain the hidden danger waveform file of the hidden danger event; if the grouping is based on the same trunk line of the same substation, if it is found that the same trunk line has zero-sequence voltage waveform files within a certain time range (e.g., 10s) after grouping, the waveform files of the same trunk line are classified as a single fault hidden danger event; perform preliminary screening and analysis on the waveform files of a single fault hidden danger event.

[0050] S4. Based on a preset zero-sequence voltage range and a second preset time range, the hidden danger waveform recording files are grouped to obtain several second waveform recording file groups. Based on the waveform recording data of the second waveform recording file groups, hidden danger points outside the area and hidden danger points inside the area are obtained, and the hidden danger points outside the area and the hidden danger points inside the area are marked. The waveforms are classified and analyzed according to the magnitude and duration of the zero-sequence voltage to more accurately determine the direction of the hidden danger.

[0051] In step S4, if the preset zero-sequence voltage range is a first voltage range and the second preset time range is a first time range, then a first zero-sequence voltage abrupt change point is obtained based on the second waveform file grouping. Based on the first zero-sequence voltage abrupt change point, the zero-sequence voltage and zero-sequence current within a first preset period are obtained. For example, based on the zero-sequence voltage and zero-sequence current within the first half-wave period after the zero-sequence voltage abrupt change point, the voltage value of the zero-sequence voltage and the current value of the zero-sequence current are obtained. Based on the voltage value and the current value, the external hidden danger point and the internal hidden danger point are obtained. This is used to analyze transient grounding faults.

[0052] The specific steps for obtaining the external and internal hidden danger points based on the voltage and current values ​​include: obtaining the first-order difference value of the voltage; if both the first-order difference value and the current value are positive or negative, the monitoring device is an external hidden danger point; if neither the first-order difference value nor the current value are positive or negative, the monitoring device is an internal hidden danger point. (Reference) Figure 3 Obtain the waveforms of the first-order differential value and the current value. If the waveforms are opposite in the same time period, they are marked as hidden danger points within the area. Similarly, if they are the same, they are hidden danger points outside the area.

[0053] In step S4, if the preset zero-sequence voltage range is the second voltage range and the second preset time range is the second time range, then based on the second waveform file grouping, a second zero-sequence voltage mutation point is obtained. Based on the second zero-sequence voltage mutation point, several sampling points within a second preset period are obtained, and the zero-sequence active power and zero-sequence reactive power of the sampling points are obtained. For example, the zero-sequence active power and zero-sequence reactive power of the sampling points two periods after the zero-sequence voltage mutation point are obtained. The zero-sequence active power and the zero-sequence reactive power are added together to obtain the total zero-sequence active power and the total zero-sequence reactive power. Based on the total zero-sequence active power and the total zero-sequence reactive power, the external hidden danger points and the internal hidden danger points are obtained. Analysis is then performed on high-resistance grounding.

[0054] The specific steps for obtaining the external hidden danger points and the internal hidden danger points based on the total zero-sequence active power and the total zero-sequence reactive power include:

[0055] If the total zero-sequence active power is less than 0, the monitoring device is a potential hazard point within the area. If the total zero-sequence active power is greater than or equal to 0 and the total zero-sequence reactive power is less than 0, the monitoring device is a potential hazard point outside the area.

[0056] If the effective value of the zero-sequence current of a potential hazard point within the zone is less than a preset current threshold, then the marker of the potential hazard point within the zone is deleted.

[0057] Wherein, the first voltage range is greater than 1kV, and the first time range is less than 40ms; the second voltage range is greater than or equal to 1kV and less than or equal to 8kV, and the second time range is the time from the start of recording to the end of recording in the hidden danger recording file.

[0058] S5. Based on the topology map, the external hidden danger points, and the internal hidden danger points, several hidden danger areas are obtained, and early warning information is obtained based on the hidden danger areas. For example, the primary and secondary fusion terminal devices of switch 3 are marked as internal hidden danger points (i.e., the direction of power outflow), and the primary and secondary fusion terminal devices of switches 2 and 4 are marked as external hidden danger points (i.e., the direction of power inflow). According to the topology map, the line areas at the front end of switches 2 and 4 and the rear end of switch 3 are marked as hidden danger areas.

[0059] In step S5, based on the potential hazard area and preset rules, early warning information is obtained. The preset rules are:

[0060] Different scoring periods are preset, and each scoring period corresponds to a warning threshold and a warning level; for example, long-term period, medium-term period and short-term period are preset, each period corresponds to a preset threshold, and the warning levels are set to general, severe and critical in sequence.

[0061] Based on a preset score and the scoring period, a hazard score for each hazard area is obtained. Based on the hazard score and the warning threshold, a warning level is obtained. Based on the warning level, the warning information is obtained. For example, a score is assigned to each hazard area, and the number of hazard areas in each period is counted to obtain a total score. This total score is then compared with a preset threshold; if it exceeds the threshold, a warning is issued.

[0062] In the scenario of grounding fault assessment for power lines crossing forest and grassland areas, transient grounding faults and high-resistance grounding faults are common fault types that significantly impact the safe and stable operation of the system. Transient grounding faults are specific to scenarios involving frequent contact between trees and power lines under wind conditions, while high-resistance grounding faults are specific to scenarios where heat accumulates over a prolonged period due to insulation degradation, potentially leading to wildfires. These fault identification methods are highly targeted. For these two types of faults, the first half-wave method and the zero-sequence power integration method are used for assessment, respectively. This approach is based on a comprehensive consideration of fault characteristics, detection principles, and practical application requirements, and each method possesses unique advantages.

[0063] At the initial stage of protection activation, this invention can select a suitable ground fault judgment algorithm based on waveform characteristics (the first half-wave method is used for instantaneous ground faults, and the zero-sequence power integration method is used for high-resistance ground faults), thereby improving the accuracy of ground fault judgment.

[0064] Transient grounding faults are often caused by tree branches occasionally touching lines under wind force, and are characterized by their short duration, generally less than 40ms. At the moment of the fault, the transient capacitive current characteristics are obvious. When a single-phase grounding occurs at the moment the phase voltage is close to its maximum value, the transient capacitive current is much larger than the transient inductive current flowing through the arc suppression coil. The transient inductive current is negligible, causing the first half-wave of the first cycle of the transient zero-sequence current of the faulty line to be opposite to that of the non-faulty line. Therefore, this invention utilizes this characteristic of the first half-wave method to quickly capture the characteristics of transient grounding faults. In the early stage of the fault, it is only necessary to analyze the zero-sequence voltage and current in the first half-wave cycle after the zero-sequence voltage mutation point to obtain the voltage and current values. By judging the positive and negative relationship between the first-order difference value of the voltage value and the current value, it is possible to determine whether the monitoring equipment is an external or internal potential fault point, achieving rapid judgment of the fault direction. This results in a faster response to transient faults, timely detection of potential fault hazards, and a reduction in situations that may be overlooked due to the short duration of the fault. Meanwhile, this method focuses on the transient characteristics at the moment of fault occurrence, avoiding interference from other factors during the steady-state process and improving the accuracy of fault judgment.

[0065] High-resistance grounding faults refer to grounding of feeders through non-metallic conductive media such as grass, concrete, and tree branches. The fault current and zero-sequence power are relatively small, and the fault characteristics are weak, but the fault persists and can lead to serious consequences. Traditional detection methods based on traveling wave waveforms and higher harmonic components, as well as methods that directly use a single sampling point for zero-sequence active and zero-sequence reactive power, have limitations in detecting high-resistance grounding faults and are difficult to accurately identify.

[0066] This invention employs the zero-sequence power integration method, an upgrade and innovation based on the zero-sequence power direction method. By integrating and accumulating the weak zero-sequence power per unit time, and separately accumulating the zero-sequence active and reactive power of a single sampling point, the subtle grounding fault characteristics of high-resistance grounding are integrated within a unit time, thereby revealing hidden and potential grounding features. By calculating the total zero-sequence active and reactive power and determining the external and internal potential fault points based on their numerical relationship, the fault direction can be determined more accurately, effectively overcoming the difficulty in detecting high-resistance grounding faults and improving the detection sensitivity and accuracy of such faults. Integrating and accumulating the weak zero-sequence power per unit time during high-resistance grounding faults allows for faster and more accurate detection of high-resistance grounding faults caused by insulation degradation, solving the problem that the traditional zero-sequence power direction method is limited by the small zero-sequence power of high-resistance grounding faults.

[0067] Example 2

[0068] Based on Example 1, in this example, the first calculation formula for obtaining the total zero-sequence active power is:

[0069]

[0070] The second calculation formula for obtaining the total zero-sequence reactive power is:

[0071]

[0072] in, Represents zero-sequence voltage. Represents zero-sequence current. Indicates the zero-sequence voltage angle. ∠Z represents the zero-sequence current angle, ∠Z represents the zero-sequence impedance angle, P0_total represents the total zero-sequence active power, Q0_total represents the total zero-sequence reactive power, i represents the i-th sampling point, and n represents the number of sampling points.

[0073] The zero-sequence power direction method is improved by using the integral of zero-sequence active and zero-sequence reactive power per unit time instead of directly using the zero-sequence active and zero-sequence reactive power of a single sampling point. This amplifies the characteristics of grounding faults and helps to detect high-resistance grounding faults more sensitively.

[0074] Example 3

[0075] Based on the above embodiments, in this embodiment, the method further includes:

[0076] Acquire forest area images, obtain a first distance between tree branches and the railway line based on the forest area images, and identify dangerous areas based on a preset distance range and the first distance; for example, acquire images around the railway line using acquisition devices such as drones, obtain the distance between tree branches and the railway line, the distance may include horizontal distance and vertical distance, and filter areas where tree branches are close to the railway line based on the distance;

[0077] The process involves: acquiring dangerous branches in the danger zone; acquiring the branch tip region of the dangerous branches; acquiring the branch diameter of the branch tip region; acquiring branch images of the dangerous branches within a preset time range; obtaining the growth diameter based on the branch images; acquiring the first line of the branch images; predicting the growth direction of the dangerous branches based on the first line; acquiring continuous growth images of dangerous branches within a week; obtaining data on changes in branch diameter through continuous growth images; extracting lines from the growth images; and obtaining the current real-time growth direction by comparing the lines.

[0078] The growth length is obtained based on the first line, and the first growth rate is obtained based on the growth diameter, the growth length, and the preset time range. The second growth rate of the dangerous branch under different branch diameters is preset based on the first growth rate. For example, by comparing the lines, the growth length of the dangerous branch within a circumference of the current growth environment is obtained. The growth rate under the current diameter is predicted based on the change data of the diameter and the growth length. Then, by combining the relevant data of this type of branch (such as a deep learning model pre-trained based on the growth data of the branch), the growth rate under different diameters in the later period is predicted.

[0079] The maximum growth length of different types of branches is predicted based on the second growth rate and the branch diameter; if the minimum diameter that different types of branches can grow is preset, the maximum growth length is predicted by combining the minimum diameter, the second growth rate and the current diameter.

[0080] Danger warnings are obtained based on a preset danger direction, the longest growth length, and the growth direction. For example, it is first determined whether the growth direction is within the preset danger direction range. If so, the longest growth length is used to determine whether it will exceed the danger zone. If so, a danger warning is issued, allowing for early pruning of branches and reducing line faults caused by branches overlapping the wiring.

[0081] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for improving the ability of grassland distribution line grounding judgment in forest fire early warning, characterized by, The method comprises: S1, install a monitoring device to a key node of a power distribution network line, and obtain a topology graph of the power distribution network; S2, obtain a line recording file based on the monitoring device, filter the line recording file, and obtain a zero sequence voltage recording file; S3, group the zero sequence voltage recording file based on a power distribution trunk line, obtain a plurality of first recording file groups, obtain a first time of the first recording file group, obtain a hidden danger event based on the first time and a first preset time range, and obtain a hidden danger recording file of the hidden danger event; S4, group the hidden danger recording file based on a preset zero sequence voltage range and a second preset time range, obtain a plurality of second recording file groups, obtain an out-of-area hidden danger point and an in-area hidden danger point based on recording data of the second recording file group, and mark the out-of-area hidden danger point and the in-area hidden danger point; S5, obtain a plurality of hidden danger areas based on the topology graph, the out-of-area hidden danger point, and the in-area hidden danger point, and obtain early warning information based on the hidden danger areas.

2. The method according to claim 1, wherein, In the S4, if the preset zero sequence voltage range is a first voltage range and the second preset time range is a first time range, a first zero sequence voltage mutation point is obtained based on the second recording file group, a zero sequence voltage and a zero sequence current within a first preset period are obtained based on the first zero sequence voltage mutation point, a voltage value of the zero sequence voltage and a current value of the zero sequence current are obtained, and the out-of-area hidden danger point and the in-area hidden danger point are obtained based on the voltage value and the current value.

3. The method of claim 2, wherein the method further comprises: In the S4, if the preset zero sequence voltage range is a second voltage range and the second preset time range is a second time range, a second zero sequence voltage mutation point is obtained based on the second recording file group, a plurality of sampling points within a second preset period are obtained based on the second zero sequence voltage mutation point, zero sequence active power and zero sequence reactive power of the sampling points are obtained, the zero sequence active power and the zero sequence reactive power are added, total zero sequence active power and total zero sequence reactive power are obtained, and the out-of-area hidden danger point and the in-area hidden danger point are obtained based on the total zero sequence active power and the total zero sequence reactive power.

4. The method of claim 1, wherein the method comprises: In the S5, early warning information is obtained based on the hidden danger areas and a preset rule, and the preset rule is: Different scoring periods are preset, and each scoring period corresponds to a warning threshold and a warning level; A hidden danger score of the hidden danger area is obtained based on a preset score and the scoring period, a warning level is obtained based on the hidden danger score and the warning threshold, and the early warning information is obtained based on the warning level.

5. The method of claim 3, wherein the method is characterized by, The first voltage range is greater than 1kV, and the first time range is less than 40ms; the second voltage range is greater than or equal to 1kV and less than or equal to 8kV, and the second time range is from the time when the hidden danger recording file starts recording to the time when it ends recording.

6. The method of claim 2, wherein the method is characterized by, The specific steps of obtaining the out-of-area hidden danger point and the in-area hidden danger point based on the voltage value and the current value include: A first-order differential value of the voltage value is obtained, if the first-order differential value and the current value are both positive or negative, the monitoring device is an out-of-zone hidden danger point, if the first-order differential value and the current value are not both positive or negative, the monitoring device is an in-zone hidden danger point.

7. The method of claim 3, wherein the method further comprises: Based on the total zero sequence active power and the total zero sequence reactive power, the specific steps of obtaining the out-of-zone hidden danger point and the in-zone hidden danger point include: If the total zero sequence active power is less than 0, the monitoring device is an in-zone hidden danger point, if the total zero sequence active power is greater than or equal to 0 and the total zero sequence reactive power is less than 0, the monitoring device is an out-of-zone hidden danger point.

8. The method of claim 3, wherein the method is characterized by, A first calculation formula for obtaining the total zero sequence active power is: A second calculation formula for obtaining the total zero sequence reactive power is: wherein denotes the zero sequence voltage, denotes the zero sequence current, denotes the zero sequence voltage angle, denotes the zero sequence current angle, denotes the zero sequence impedance angle, P0total denotes the total zero sequence active power, Q0total denotes the total zero sequence reactive power, i denotes the i-th sample point, n denotes the number of sample points.

9. The method of claim 3, wherein the method is characterized by, If the zero sequence current effective value of the in-zone hidden danger point is less than a preset current threshold, the label of the in-zone hidden danger point is deleted.

10. The method of claim 1, wherein the method is used for improving the ability of the grassland distribution line ground fault detection to early warn of forest fires. The method further includes: An image of a forest area is obtained, a first distance between a branch and a line is obtained based on the image of the forest area, a dangerous area is obtained based on a preset distance range and the first distance; A dangerous branch of the dangerous area is obtained, a branch tip area of the dangerous branch is obtained, a branch diameter of the branch tip area is obtained, a branch image of the dangerous branch in a preset time range is obtained, and a growth diameter is obtained based on the branch image; A first line of the branch image is obtained, and a growth direction of the dangerous branch is predicted based on the first line; A growth length is obtained based on the first line, a first growth speed is obtained based on the growth diameter, the growth length and the preset time range, and a second growth speed of the dangerous branch under different branch diameters is preset based on the first growth speed; The longest growth length of different types of branches is predicted based on the second growth speed and the branch diameter; A dangerous warning is obtained based on a preset dangerous direction, the longest growth length and the growth direction.

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