Low-voltage cable branch box grounding abnormal emergency power-off control method

Abstract

This application provides an emergency power outage control method for grounding abnormalities in low-voltage cable branch boxes, comprising: acquiring instantaneous measured grounding resistance and soil moisture of the cable branch box after a grounding abnormality occurs; extracting the temporal characteristics of the grounding resistance and the abrupt change characteristics of the moisture; performing classification judgment to obtain the environmental interference classification result and interference intensity; judging whether the grounding resistance of the branch box is falsely compliant based on the degradation adjustment amount, degradation status file, current grounding resistance measurement value and environmental interference classification result; when the judgment conclusion is false compliance, generating a preset interlocking control command, adding the degradation adjustment amount to the interlocking control command and sending it to the incoming switch controller of the low-voltage circuit where the branch box is located, forcibly maintaining the open state.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to an emergency power outage control method for grounding abnormalities in low-voltage cable branch boxes. Background Technology

[0002] The safe operation of low-voltage distribution networks is the cornerstone of ensuring electricity supply to society. Among these, emergency power outage control for grounding abnormalities in cable branch boxes is a crucial line of defense against electric shock and fire accidents. After a grounding abnormality power outage, the conventional method of restoring power often relies on directly re-measuring the grounding resistance, assuming that as long as the re-measured value meets the standard, the power outage lockout can be lifted. The flaw in this approach is that it over-relies on the apparent compliance of instantaneous measurement results, ignoring the short-term masking effect of external environmental changes on electrical physical quantities, leading to blind spots in the safety verification process. Existing technology, CN122193708A, discloses a method, device, and system for measuring the grounding resistance of power transmission towers, relating to the field of power system detection technology. It addresses the problem of eliminating the interference of instantaneous fluctuations in the soil environment on the on-site measurement value of grounding resistance, obtaining resistance measurement results that more closely approximate the true stable state of the grounding device. The method includes: acquiring the real-time grounding resistance measurement value of the target power transmission tower and the real-time soil environmental parameters of the measurement area; determining the environmental correction factor for the target power transmission tower under the current measurement based on the real-time soil environmental parameters and the historical grounding resistance measurement values ​​and corresponding historical soil environmental parameters of multiple reference power transmission towers in the measurement area within a preset time period; correcting the real-time grounding resistance measurement value based on the environmental correction factor to obtain the corrected real-time grounding resistance value of the target power transmission tower; and providing an early warning of the grounding status of the target power transmission tower based on the corrected real-time grounding resistance value and a preset safety threshold. Specifically, the value of grounding resistance is highly susceptible to the influence of the surrounding soil environment. When power is cut off and rainfall or groundwater seepage occurs, soil moisture will rapidly increase in a short period. This rapid increase in moisture significantly enhances the conductivity of the soil, thus creating a false impression of a significant decrease in grounding resistance value during retesting. This illusion directly leads to a false appearance of compliance in a single measurement for a deteriorated grounding device that has already suffered material aging or structural damage. For example, in a city's power distribution network, a cable branch box's grounding resistance had slowly deteriorated to exceed safety limits (e.g., greater than 4Ω) due to long-term corrosion of the grounding down conductor. The system automatically triggered a power-off lockout upon detecting the anomaly. Subsequently, a thunderstorm occurred, causing rainwater to rapidly seep into the soil around the branch box, significantly increasing the local soil moisture content and conductivity. At this point, maintenance personnel or the automatic system retested the grounding resistance, finding it to be 2.8Ω, seemingly back to within acceptable limits. If the lockout were immediately lifted and power restored, the operation appeared compliant, but in reality, the physical deterioration of the grounding device itself, such as corrosion and breakage, remained unrepaired. As the soil moisture evaporated rapidly after the rain, the grounding resistance would rise again to dangerous levels within hours, while the equipment continued to operate in a faulty state. This greatly increased the risk of the box becoming energized or overheating and catching fire in the event of a subsequent leakage or short circuit due to the inability to effectively discharge the fault current. Summary of the Invention

[0003] This invention provides an emergency power outage control method for abnormal grounding of low-voltage cable branch boxes, mainly including: The instantaneous grounding resistance and soil moisture of the cable branch box after a grounding anomaly are obtained. The temporal characteristics of the grounding resistance and the abrupt change characteristics of the moisture are extracted, and a classification judgment is performed to obtain the environmental interference classification results and interference intensity. When environmental interference is detected, the degree of corrosion of the grounding electrode and the degree of looseness of the down conductor connection are read from the deterioration status file of the cable branch box, and the deterioration adjustment amount is determined in combination with the interference intensity. If there is no environmental interference, the current grounding resistance measurement value is deemed qualified, a power restoration command is generated to re-energize the circuit, the switch closing position and the circuit voltage signal are collected as execution feedback information, and a normal record text is generated according to the normal record template. Based on the aforementioned degradation adjustment amount, the degradation status file, the current grounding resistance measurement value, and the environmental interference classification result, determine whether the branch box grounding resistance is falsely compliant; When the judgment conclusion is false compliance, a preset interlocking control command is generated, and the deterioration adjustment amount is added to the interlocking control command and sent to the incoming switch controller of the low-voltage circuit where the cable branch box is located, forcibly maintaining the open state. For branch boxes in a forced tripping state, the grounding resistance is remeasured and soil moisture is collected simultaneously before the interlock is released. The grounding resistance remeasurement value, the real-time soil moisture value, and the grounding resistance rise after power failure are obtained. Combined with the aforementioned deterioration adjustment amount, it is confirmed that the grounding has stabilized and met the standards. Drive the incoming line switch to close and release the forced trip state, write the grounding resistance remeasurement value and the real-time soil moisture value back to the deterioration state file, update the historical trajectory of corrosion degree and connection loosening degree and refresh the current control state.

[0004] Furthermore, the instantaneous measurement of grounding resistance and soil moisture of the cable branch box after a grounding anomaly occurs includes: The instantaneous resistance value is read by the grounding resistance online monitoring terminal built into the box, and the soil volume moisture content reading is obtained synchronously by the moisture sampling probe buried in the soil around the grounding electrode. The instantaneous resistance value and the soil volume moisture content reading are aligned with the execution time according to a unified timestamp to obtain a resistance-humidity pairing sequence marked with timestamps. A sliding window is formed by extending forward and backward for a fixed duration from the power failure trigger time.

[0005] Furthermore, the extraction of grounding resistance timing characteristics and humidity abrupt change characteristics includes: The slope of the resistance decrease is fitted using the least squares method for the instantaneous resistance value subsequence within the sliding window. The maximum drop in resistance value is extracted and combined with the sequence fluctuation variance to form the time series feature of the grounding resistance. The first-order difference is obtained point by point for the soil volume moisture content subsequence within the same window to obtain the humidity increment. The humidity increment is compared with the humidity baseline of the same month and time period in history. Segments that deviate from the baseline and show a steep upward trend are marked as humidity mutation inflection points. The peak value of the humidity increment is taken and the time offset of the humidity mutation inflection point relative to the power outage trigger time is recorded. The combination is used to obtain the humidity mutation feature.

[0006] Furthermore, the step of determining the degradation adjustment amount based on the degradation status file of the cable branch box, which includes reading the degree of corrosion of the grounding electrode and the degree of looseness of the down conductor connection, combined with the interference intensity, includes: A file retrieval request is initiated to the distribution network operation and maintenance database based on the unique number of the cable branch box. The deterioration status file is pre-constructed based on the grounding electrode material label, anti-corrosion process type, installation year, and the down conductor connection status recorded in previous on-site inspections. The degree of corrosion of the grounding electrode is expressed as a deterioration score, which is a combination of the corrosion area ratio and the remaining cross-sectional thickness. The degree of looseness of the down conductor connection is expressed as the percentage decrease in the residual tightening torque relative to the factory rated torque. The attenuation coefficient is indexed from the attenuation lookup table according to the material label and anti-corrosion process type. The deterioration score is multiplied by the attenuation coefficient to obtain the corrosion correction component. The percentage decrease is multiplied by the attenuation coefficient to obtain the connection correction component. The two correction components are summed to obtain the basic deterioration adjustment amount. The interference intensity is used as a scaling factor and multiplied by the basic deterioration adjustment amount to obtain the deterioration adjustment amount.

[0007] Furthermore, if there is no environmental interference, the current grounding resistance measurement value is deemed qualified, a power restoration command is generated to re-energize the circuit, the switch closing position and circuit voltage signals are collected as execution feedback information, and a normal record text is generated according to the normal record template, including: The cable branch box's unique number and reading qualification conclusion are packaged according to the preset power restoration instruction format and sent to the incoming switch controller to drive the incoming switch to the closed state; the closing signal of the auxiliary contact of the switch body and the voltage transformer's live signal are collected and combined into the execution feedback information, and the restoration operation time, current grounding resistance measurement value and the execution feedback information are filled in according to the normal record template.

[0008] Furthermore, the step of determining whether the branch box grounding resistance is falsely compliant based on the degradation adjustment amount, the degradation status file, the current grounding resistance measurement value, and the environmental interference classification result includes: For cable branch boxes with environmental interference labels, a grounding resistance correction value is determined based on the degradation adjustment amount and the current grounding resistance measurement value. A safety threshold matching the cable branch box is indexed from a pre-established threshold mapping table based on the grounding electrode material label and anti-corrosion process category in the degradation status file. This threshold mapping table pre-records the limit benchmarks for low-voltage distribution network grounding resistance according to different material and process combinations. The grounding resistance correction value is compared with the safety threshold. If the grounding resistance correction value exceeds the safety threshold, the grounding resistance of the branch box is determined to be falsely compliant; otherwise, it is determined to be truly compliant.

[0009] Furthermore, when the judgment conclusion is a false compliance, a preset interlocking control command is generated, and the degradation adjustment amount is added to the interlocking control command and sent to the incoming switch controller of the low-voltage circuit where the cable branch box is located, forcibly maintaining the open state, including: The cable branch box's unique number, false compliance judgment conclusion, and interlocking action field are encapsulated according to the preset interlocking control instruction format. The degradation adjustment amount is written as an additional field into the interlocking control instruction load area and sent to the incoming switch controller via the fieldbus. The incoming switch controller locks the incoming switch closing circuit and maintains the open state, and retains the degradation adjustment amount in the local register.

[0010] Furthermore, for the branch box in the forced tripping state, before releasing the interlock, the grounding resistance is remeasured and soil moisture is collected simultaneously to obtain the remeasured grounding resistance value, the real-time soil moisture value, and the rise in grounding resistance after power failure, including: The grounding resistance remeasurement value is obtained by rereading the grounding resistance online monitoring terminal built into the enclosure, and the soil moisture value is obtained by synchronously collecting the soil volume moisture content by the humidity sampling probe; the lowest reading is extracted from the archived grounding resistance reading sequence between the forced tripping time and the current remeasurement time, and the grounding resistance remeasurement value is subtracted from the lowest reading to obtain the grounding resistance recovery amplitude after power failure.

[0011] Furthermore, the step of confirming that the grounding has stabilized and met the standards in conjunction with the degradation adjustment amount includes: The difference between the remeasured grounding resistance value and the deterioration adjustment amount is compared with the safety threshold corresponding to the cable branch box. If the difference is lower than or equal to the safety threshold, and the real-time soil moisture value falls back into the preset humidity baseline range, and the rise in grounding resistance after power failure exceeds the preset stability threshold, then it is confirmed that the grounding of the cable branch box has been stably up to standard.

[0012] Furthermore, the step of driving the incoming line switch to close and release the forced tripping state, and writing the remeasured grounding resistance value and the real-time soil moisture value back to the deterioration status file, includes: The cable branch box's unique number, stability compliance conclusion, and unlocking action field are encapsulated according to the preset power restoration command format. The command is then sent to the incoming switch controller via fieldbus to release the normally open state of the closing circuit interlock relay and drive the incoming switch to the closed state. The closing signal of the switch auxiliary contact and the voltage transformer's live signal are collected as status feedback. The stability compliance conclusion, the grounding resistance remeasurement value, the real-time soil moisture value, and the status feedback are all written back to the deterioration status file.

[0013] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses an emergency power outage control method for grounding anomalies in low-voltage cable branch boxes. Addressing the problem of misjudging power supply due to the difficulty in distinguishing between environmental interference and actual degradation when grounding anomalies occur, this method classifies environmental interference by extracting the temporal characteristics of grounding resistance and the abrupt changes in soil moisture. When environmental interference is present, the degradation status file of the branch box is retrieved to read the degree of corrosion of the grounding electrode and the looseness of the down conductor connection. The degradation adjustment amount is determined based on the interference intensity to correct the current reading. Based on the corrected value, it is determined whether it is a false compliance. If it is a false compliance, a lockout control command carrying the degradation adjustment amount is generated to forcibly maintain the open state. Before releasing the lockout, the grounding resistance and soil moisture are remeasured. The lockout is released and the degradation status file is updated only after confirming that the grounding has stabilized and met the standards by combining the remeasured grounding resistance value with the post-power outage recovery rate and the degradation adjustment amount. This achieves the separation, identification, and precise control of environmental interference and equipment degradation, avoiding false power outages caused by environmental factors and power supply with defects due to degradation masking, effectively improving the power supply reliability and operational safety of low-voltage power distribution systems. Attached Figure Description

[0014] Figure 1 This is a flowchart of an emergency power outage control method for grounding abnormalities in a low-voltage cable branch box according to the present invention.

[0015] Figure 2 This is a schematic diagram of an emergency power outage control method for grounding abnormalities in a low-voltage cable branch box according to the present invention.

[0016] Figure 3 This is another schematic diagram of an emergency power outage control method for grounding abnormalities in a low-voltage cable branch box according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. The described embodiments are merely some embodiments of the present invention.

[0018] like Figures 1-3 This embodiment of an emergency power outage control method for grounding abnormalities in a low-voltage cable branch box may specifically include: Step S101: Obtain the instantaneous grounding resistance and soil moisture of the cable branch box after a grounding anomaly occurs, extract the temporal characteristics of the grounding resistance and the abrupt change characteristics of the moisture, perform classification judgment, and obtain the environmental interference classification results and interference intensity.

[0019] When the cable branch box experiences a grounding abnormality and power outage, the instantaneous resistance value is read by the online monitoring terminal of the grounding resistance built into the box. Simultaneously, the soil volumetric moisture content reading is obtained by a humidity sampling probe buried in the soil around the grounding electrode. The instantaneous resistance value and the humidity sampling reading are aligned with a unified timestamp, and misaligned records caused by inconsistent sampling intervals are eliminated to obtain a time-stamped resistance-humidity pairing sequence. A sliding window is formed by extending a fixed duration forward and backward from the power outage trigger time, and the sliding window is used to define the value range for subsequent feature extraction. Based on the resistance-humidity pairing sequence defined by the sliding window, the least squares method is used to fit the decreasing slope of the resistance value over time in the instantaneous resistance value subsequence within the window, and the maximum drop amplitude of the resistance value and the variance of the sequence fluctuation are extracted and combined to form the grounding resistance time series characteristics; the first-order difference is obtained point by point for the soil volume moisture content subsequence in the same window to obtain the humidity increment, and the humidity increment is compared with the humidity baseline recorded by the branch box in the same month and period in history. The segments that deviate from the baseline and show a steep upward trend are marked as humidity mutation inflection points. The maximum value of the humidity increment in the segment is taken as the humidity increment peak value, and the time offset of the occurrence time of the mutation inflection point relative to the power outage trigger time is recorded, and the humidity mutation characteristics are combined to obtain the humidity mutation features. A joint feature vector is formed by concatenating the time-series characteristics of grounding resistance and the abrupt change characteristics of humidity according to dimensions. A pre-trained support vector machine classifier is used to classify the joint feature vector and output the environmental interference classification result. The classification result includes two classification labels: presence of environmental interference and absence of environmental interference. For samples whose classification label indicates presence of environmental interference, the product of the maximum drop in resistance and the peak value of the humidity increment is used as the initial value of interference intensity. The inverse of the time offset is used as a weighting coefficient and multiplied by the initial value of interference intensity to obtain the interference intensity value reflecting the strength of environmental interference.

[0020] It should be noted that the cable branch box is usually installed on the roadside or in the green belt of the urban low-voltage power distribution network. A galvanized flat steel or copper-clad steel grounding electrode is buried under the box body, and the grounding down conductor is laid along the inner wall of the box and connected to the neutral busbar.

[0021] In one possible implementation, an online monitoring terminal for grounding resistance with a four-terminal measurement function is installed inside the enclosure. The current injection circuit and potential detection circuit of the terminal are respectively led to the grounding electrode and the auxiliary probe, so that the instantaneous resistance value can be read within the same second when a grounding abnormality is triggered by a power outage.

[0022] Specifically, the humidity sampling probe is a frequency domain reflectometer probe, buried at a depth of approximately 30 to 50 centimeters, and arranged horizontally adjacent to the grounding electrode. The output soil volumetric moisture content reading is expressed as a percentage. The instantaneous resistance value and humidity reading come from the electrical measurement circuit and the geotechnical measurement circuit, respectively, and their sampling frequencies are often inconsistent, thus requiring time alignment.

[0023] In one embodiment, time alignment employs a nearest neighbor matching method. For each instantaneous resistance value's timestamp, the record with the smallest time difference in the humidity reading sequence is searched for and paired. Pairs with time differences exceeding a preset tolerance are discarded, and the remaining pairs are concatenated in chronological order to form the resistance-humidity pairing sequence. The tolerance is typically set to half the sampling period.

[0024] For example, the sliding window takes the power outage trigger moment as the midpoint, extends forward for several sampling periods to retain the steady-state characteristics before the power outage, and extends backward for several sampling periods to cover the recovery trend after the power outage. The total window duration is generally on the order of several minutes. The window boundaries truncate the paired sequences, removing the beginning and end, to obtain the subsequences that fall within the window.

[0025] Understandably, the process of fitting the decreasing slope of the instantaneous resistance numerical subsequence using the least squares method involves using the time axis as the independent variable and the resistance value as the dependent variable, and solving for the first-order regression line that minimizes the sum of squared residuals. The slope of the resulting line is the decreasing slope. The maximum drop in resistance value is obtained by subtracting the minimum value from the initial value of the subsequence, and the variance of the sequence fluctuation is calculated according to the general definition in statistics. These three values ​​are concatenated dimensionally to form the time-series characteristics of grounding resistance.

[0026] Preferably, the humidity baseline is obtained by taking the average and standard deviation of the soil volumetric moisture content readings for the same month and time period over several previous years for the branch box, and stored in the power distribution network operation and maintenance database for retrieval. Whenever a grounding anomaly occurs, the corresponding baseline mean and baseline standard deviation are indexed according to the current month and current time period.

[0027] In one embodiment, the identification of humidity abrupt change inflection points is performed as follows: First, the first-order difference of the soil volumetric moisture content subsequence within the window is calculated point by point to obtain the humidity increment sequence; then, the humidity increment at each point is compared with a threshold obtained by adding several times the baseline standard deviation to the baseline mean; if the humidity increments of multiple consecutive sampling points simultaneously exceed the threshold and have the same sign showing a steep upward trend, then the segment is marked as a humidity abrupt change inflection point segment, and the maximum value of the humidity increment within the segment is taken as the humidity increment peak value. The difference between the time when the maximum value appears and the time when the power outage is triggered is recorded as the time offset. The humidity abrupt change feature is composed of the humidity increment peak value and the time offset.

[0028] For example, a cable branch box was suddenly hit by a thunderstorm in the afternoon. Within minutes of the power outage, the soil volumetric moisture content rapidly increased from 18% to 32%. The corresponding instantaneous resistance dropped from 5.6 ohms to 2.8 ohms. The slope of the drop was negative and the absolute value was significant. The maximum drop was about 2.8 ohms, the peak humidity increase was about 14%, and the time offset was about 2 minutes.

[0029] Specifically, the training process of the support vector machine classifier is completed offline in advance. The training samples are taken from grounding anomaly events in the historical archives of the power distribution network that have been manually verified. Each sample contains a joint feature vector composed of a set of time-series features of grounding resistance and humidity mutation features, along with its category label. The label is determined by the verification conclusion as either the presence or absence of environmental interference. During training, a radial basis function kernel is used to map the joint feature vector to a high-dimensional space, and the maximum margin separating hyperplane is solved. The resulting classifier is deployed in the emergency power outage control device as a model file. In the online judgment phase, the classifier outputs category labels for the real-time joint feature vector.

[0030] In one possible implementation, for samples determined to have environmental interference, the interference intensity value is obtained as follows: First, the initial interference intensity I0 is obtained by multiplying the maximum resistance drop amplitude ΔR by the peak humidity increment ΔH, i.e., I0 = ΔR × ΔH; then, the reciprocal of the time offset Δt is used as a weighting coefficient and multiplied by I0, resulting in interference intensity I = I0 ÷ Δt. Here, ΔR is in ohms, ΔH is a dimensionless percentage reading, and Δt is in minutes.

[0031] Understandably, a shorter time offset indicates that the humidity change occurs closer to the moment of power outage, resulting in a more severe instantaneous drop in the grounding resistance reading and a larger weighted interference intensity value. Conversely, a longer time offset results in a relatively smaller weighted interference intensity value. The interference intensity value, along with the environmental interference classification result, is output to the higher-level emergency power outage control process.

[0032] Step S102: When the environmental interference classification result determines that there is environmental interference, the degree of corrosion of the grounding body and the degree of looseness of the down conductor connection are read from the deterioration status file constructed based on the material of the grounding body of the branch box, the anti-corrosion process, the installation years and the connection status of the grounding down conductor recorded in previous tests. Combined with the interference intensity, the deterioration adjustment amount used to correct the current reading is determined.

[0033] For cable branch boxes identified as having environmental interference based on environmental interference classification results, a file retrieval request is initiated from the distribution network operation and maintenance database using the unique branch box number. The deterioration status file of the branch box is retrieved. The deterioration status file is pre-constructed based on the grounding electrode material label, anti-corrosion process type, installation year, and the grounding down conductor connection status recorded in previous on-site inspections. The material label distinguishes between galvanized flat steel and copper-clad steel, the anti-corrosion process type distinguishes between hot-dip galvanizing and electro-galvanizing, the installation year is expressed as the annual difference from the commissioning date to the current date, and the down conductor connection status is recorded as the residual value of the tightening torque. Based on the fields stored in the degradation status file, two degradation indicators are extracted: the degree of corrosion of the grounding electrode and the degree of looseness of the down conductor connection. The degree of corrosion is expressed as a degradation score formed by the ratio of the corrosion area on the grounding electrode surface to the remaining cross-sectional thickness. The degree of looseness is expressed as the percentage decrease in the residual tightening torque relative to the factory rated torque. The attenuation coefficient is indexed from a pre-established attenuation lookup table according to the material label and anti-corrosion process category. The attenuation lookup table pre-records the baseline values ​​of resistance attenuation coefficients for different material and process combinations under different installation years. The installation years are used as an auxiliary index item to index the query results, thereby obtaining an attenuation coefficient that matches the current status of the branch box. The corrosion correction component is obtained by multiplying the degradation score of the corrosion degree by the attenuation coefficient, and the connection correction component is obtained by multiplying the percentage decrease in the loosening degree by the same attenuation coefficient. The two correction components are combined by summing to obtain the degradation base adjustment amount. The degradation adjustment amount is obtained by multiplying the interference intensity as a scaling factor with the degradation base adjustment amount to correct the current grounding resistance reading. The degradation adjustment amount increases in the same direction as the interference intensity value increases, and also increases in the same direction as the corrosion degree and loosening degree worsen. Finally, it is output to the emergency power outage control process for subsequent reading correction.

[0034] It should be noted that the degradation status file is pre-stored in the distribution network operation and maintenance database, indexed by the unique number of the cable branch box. Each record corresponds to one branch box and contains several static fields and several dynamic fields. The static fields cover the grounding electrode material label, anti-corrosion process type, and commissioning date, which are entered at once from the branch box's factory data and commissioning file. The dynamic fields cover the percentage of corrosion area on the grounding electrode surface, remaining cross-sectional thickness, residual tightening torque, and inspection date recorded in each on-site inspection, which are updated by the inspection personnel according to the planned cycle.

[0035] Specifically, the material label field uses a number as its value, with number 1 indicating galvanized flat steel and number 2 indicating copper-clad steel; the anti-corrosion process category field also uses a number as its value, with number 1 indicating hot-dip galvanizing and number 2 indicating electro-galvanizing. Galvanized flat steel combined with hot-dip galvanizing is typically used in low-voltage power distribution scenarios in ordinary urban areas, while copper-clad steel combined with electro-galvanizing is typically used in coastal areas with high salt spray or in industrial environments with severe corrosion.

[0036] In one possible implementation, the installation lifespan is calculated as the annual difference between the commissioning date and the current date, with the annual difference in whole years. For example, if a branch box was commissioned in June 2008 and the current date is June 2026, then the installation lifespan is 18 years.

[0037] It is understandable that the degree of corrosion of the grounding electrode is not expressed by a single index, but rather by a deterioration score obtained by combining two physical quantities.

[0038] Specifically, the percentage of corroded area on the grounding electrode surface is denoted as 'a', a decimal between 0 and 1, obtained through visual inspection or image segmentation during previous on-site inspections; the ratio of the remaining cross-sectional thickness to the factory-rated cross-sectional thickness is denoted as 'b', also a decimal between 0 and 1, obtained by measurement with an ultrasonic thickness gauge or calipers. The degradation score S is synthesized using the formula S = a × (1 - b), where 'a' reflects the extent of surface corrosion expansion, and '1 - b' reflects the degree of cross-sectional thickness attenuation. The larger the product of the two, the more severe the corrosion. The degradation score monotonically increases over time and is stored in a dynamic field of the degradation status archive for retrieval.

[0039] For example, the degree of looseness of the down conductor connection is expressed as a percentage decrease in the residual tightening torque relative to the factory rated torque. Let the factory rated torque be T0, and the currently detected residual tightening torque be T1. Then the percentage decrease D is obtained by (T0-T1)÷T0, and the value is a decimal between 0 and 1. The larger this percentage decrease is, the more significant the loosening of the bolts fastening the down conductor to the grounding electrode or to the neutral busbar.

[0040] Preferably, the attenuation lookup table is pre-established in the reference table area of ​​the operation and maintenance database. Its rows use a pairwise combination of material label and anti-corrosion process category as the primary key, and its columns use several intervals of installation years as secondary keys. Each cell in the table stores a baseline attenuation coefficient, which is obtained from historical sampling data of the distribution network in the following way: Regression analysis is performed on grounding electrodes with the same material and process combination using the least squares method. The installation years T of the grounding electrode is used as the independent variable, and the ratio of the measured grounding resistance R to the factory nominal resistance R0 is used as the dependent variable. The attenuation curve R divided by R0 is equal to a multiplied by T raised to the power of b plus c, where a, b, and c are regression coefficients. The function value at the median point of the fitted curve in each age interval is used as the baseline attenuation coefficient for that interval and filled into the table, reflecting the baseline attenuation ratio of the resistance for that material and process combination in the corresponding age interval.

[0041] In one embodiment, when indexing a branch box, the primary key row is first selected based on its material label and anti-corrosion process category, and then the secondary key column is selected based on the range in which its installation year falls. The cell at the intersection of the row and column is the attenuation coefficient matching the current state of the branch box. For example, for a branch box with material label No. 1, anti-corrosion process category No. 1, and installation year of 18 years, the indexing result falls within the cells in the 16 to 20 year range under the hot-dip galvanized combination of galvanized flat steel.

[0042] Specifically, the corrosion correction component C1 is obtained by multiplying the deterioration score S by the attenuation coefficient K, calculated as C1 = S × K. The connection correction component C2 is obtained by multiplying the decrease percentage D by the same attenuation coefficient K, calculated as C2 = D × K. The deterioration score S ranges from 0 to 1, representing the degree of corrosion; the decrease percentage D ranges from 0 to 1, representing the degree of decrease in connection performance; and the attenuation coefficient K is a dimensionless adjustment coefficient, typically ranging from 0.5 to 2.0, used to control the weight of deterioration's impact on the overall assessment. Both C1 and C2 are dimensionless adjustment quantities, physically representing the contribution value of the deterioration degree after weighting. The basic deterioration adjustment quantity C0 is obtained by summing the two correction components, calculated as C0 = C1 + C2. Sharing the same attenuation coefficient K ensures that rust channels and loosening channels are calculated under the same benchmark, ensuring the comparability and additivity of the contribution values ​​for different deterioration types. For example, when S is 0.6, D is 0.4, and K is 1.5, then C1 is 0.9, C2 is 0.6, and C0 is 1.5.

[0043] Understandably, the interference intensity value I output by the environmental monitoring module in the previous step reflects the instantaneous drop in grounding resistance reading caused by changes in environmental humidity. This value is obtained by comparing the deviation rate between the reference resistance under standard conditions and the current measured resistance, with a range of 1.0 to 3.5. The larger the value, the more the reading is suppressed by the environment, and the greater the resistance compensation should be for the actual degradation. The positive relationship between the interference intensity value and the degradation adjustment amount stems from the following mechanism: the higher the environmental humidity, the thicker the surface conductive film, and the more significant the reduction in measured resistance. The increase in contact resistance caused by actual corrosion and loosening of the equipment is more deeply masked, thus requiring a larger compensation amount to restore the true degradation state. The degradation adjustment amount C is obtained by multiplying the interference intensity value I by the degradation base adjustment amount C0, i.e., C = I × C0. The degradation adjustment amount increases in the same direction as the interference intensity value increases, and also increases in the same direction as the degree of corrosion and loosening worsens. For example, if a branch box in a coastal industrial zone has a material label of No. 2, an anti-corrosion process category of No. 2, and an installation period of 12 years, with a degradation score S of approximately 0.36, a decrease percentage D of approximately 0.20, and an attenuation coefficient K obtained from the index of approximately 1.15, then the corrosion correction component C1 is approximately 0.414, the connection correction component C2 is approximately 0.230, and the degradation base adjustment C0 is approximately 0.644. This, combined with the current interference intensity value, yields the corresponding degradation adjustment. This degradation adjustment is then fed back to the reading correction stage in the emergency power outage control process, serving as a compensation benchmark for the current grounding resistance reading of the branch box for subsequent correction. Optionally, the correction method involves subtracting the degradation adjustment from the current grounding resistance measurement value to obtain the corrected grounding resistance value.

[0044] In step S103, if there is no environmental interference, the current grounding resistance measurement value is directly deemed valid, a power restoration command is generated and the circuit is re-energized, and the switch closing position and circuit voltage signal are collected as execution feedback information. Normal record text containing restoration operation and verification status is generated according to the normal record template.

[0045] For cable branch boxes where environmental interference classification results indicate no environmental interference, the current grounding resistance measurement value is directly deemed valid without needing to retrieve the deterioration status file for reading correction. The branch box's unique number and the valid reading conclusion are encapsulated according to a preset power restoration command format and sent to the incoming switch controller of the low-voltage circuit where the branch box is located. This drives the incoming switch to switch from open to closed, re-energizing the low-voltage circuit. For the incoming switch after the power restoration command is issued, the closing signal output from the auxiliary contacts of the switch body and the live signal output from the voltage transformer on the circuit's outgoing side are collected. These two signals are combined as execution feedback information, and the restoration operation time, current grounding resistance measurement value, and the execution feedback information are filled in according to a preset normal record template to generate a normal record text containing the restoration operation and verification status.

[0046] For cable branch boxes where the environmental interference classification results indicate that there is no environmental interference, the current grounding resistance measurement value is not affected by the sudden change in soil moisture, and the reading itself is capable of reflecting the true state of the grounding device, so there is no need to retrieve the deterioration status file for secondary correction.

[0047] In one possible implementation, the emergency power outage control device encapsulates the unique number of the branch box, the valid reading conclusion, and the issuance time according to a preset power restoration instruction format, and sends it to the incoming switch controller of the low-voltage circuit where the branch box is located via fieldbus.

[0048] Specifically, after receiving the power restoration command, the incoming line switch controller drives its internal partial closing coil to switch the incoming line switch from the open state to the closed state, and the bus of the low-voltage circuit is restored from the undervoltage state to the energized state.

[0049] In one embodiment, the incoming line switch is typically a molded case circuit breaker or a frame circuit breaker, with auxiliary contacts on its body side to reflect the opening and closing positions of the main contacts. Further, for the incoming line switch after the power restoration command is issued, the closing signal output by the auxiliary contacts of the switch body and the live signal output by the voltage transformer on the outgoing side of the circuit are collected. A closing signal of 1 indicates that the main contacts are fully closed, and a live signal of 1 indicates that the three-phase voltage on the outgoing side of the circuit is within the rated range. When both signals are simultaneously 1, the power restoration is considered successful.

[0050] For example, the normal record template is pre-stored in the template library of the operation and maintenance database, and includes fields for branch box number, recovery operation time, current grounding resistance measurement value, and execution feedback information. The emergency power outage control device fills in the corresponding fields according to the template to obtain a normal record text containing the recovery operation and verification status, and archives it into the operation file of the branch box according to the branch box number.

[0051] Step S104: Based on the degradation adjustment amount, degradation status file, current grounding resistance measurement value and environmental interference classification results, determine whether the branch box grounding resistance is falsely compliant.

[0052] For cable branch boxes with environmental interference labels, a degradation adjustment is used to compensate for the current grounding resistance measurement. Specifically, the degradation adjustment is added to the current grounding resistance measurement as a compensation increment to obtain a grounding resistance correction value that reflects the removal of the instantaneous reduction in environmental humidity. This correction value represents the true resistance level of the grounding device after removing the illusion of moisture. Based on the grounding body material label and anti-corrosion process category stored in the degradation status file, the corresponding safety threshold for the branch box is indexed from a pre-established threshold mapping table. This threshold mapping table is independent of the aforementioned attenuation lookup table and pre-records the limit benchmarks for low-voltage distribution network grounding resistance according to different material and process combinations to obtain a safety threshold matching the current state of the branch box. A numerical comparison is performed between the grounding resistance correction value and the safety threshold. If the correction value exceeds the safety threshold, the grounding resistance of the branch box is determined to be falsely compliant; otherwise, it is determined to be truly compliant, resulting in a false compliance determination conclusion. This conclusion is written back to the emergency power outage control process according to the unique branch box number for subsequent interlocking procedures.

[0053] In one possible implementation, the emergency power outage control device simultaneously retrieves the degradation adjustment amount, the degradation status file, and the current grounding resistance measurement value according to the unique number of the cable branch box, and enters the false compliance judgment process.

[0054] Specifically, the compensation direction follows these principles: sudden changes in environmental humidity temporarily increase soil conductivity after a power outage, causing the measured instantaneous resistance to be lower than the actual resistance, thus suppressing the current grounding resistance measurement. The degradation adjustment is added to the current grounding resistance measurement as a compensation increment. Let the current grounding resistance measurement be R0 and the degradation adjustment be C. The grounding resistance correction value Rc is then obtained as Rc = R0 + C. This correction value represents the true resistance level of the branch box grounding device after removing the moisture illusion. For example, if the current grounding resistance measurement R0 of a branch box is 2.8 ohms and the degradation adjustment C is approximately 1.5 ohms, then the grounding resistance correction value Rc is approximately 4.3 ohms. Furthermore, the threshold mapping table is pre-established in the reference table area of ​​the operation and maintenance database, existing independently of the aforementioned attenuation lookup table. Its rows are based on a pairwise combination of the grounding body material label and the anti-corrosion process category as the primary key. Each row stores a safety threshold value, which is obtained by combining the low-voltage distribution network grounding resistance limit regulations with the allowable deviations of different materials and processes.

[0055] In one embodiment, when performing threshold indexing for a branch box, a row is selected based on the grounding electrode material label and anti-corrosion process category stored in its deterioration status file. The value recorded in the row is the safety threshold matching the current state of the branch box. For example, for a branch box with material label number 1 and anti-corrosion process category number 1, the indexing result falls in the row corresponding to the hot-dip galvanized combination of galvanized flat steel, and the safety threshold value is typically in the range of 4 ohms.

[0056] Specifically, the false compliance determination process compares the grounding resistance correction value Rc with the safety threshold Rs: if Rc is greater than Rs, it indicates that the actual resistance of the branch box grounding device has exceeded the safety limit, and the current grounding resistance measurement value R0 is within the limit only due to the illusion of moisture, and the branch box grounding resistance is determined to be false compliance; if Rc is less than or equal to Rs, it indicates that the actual resistance of the grounding device is still within the safety limit, and the current grounding resistance measurement value has a true compliance meaning, and is determined to be true compliance.

[0057] It is understandable that the environmental interference classification result of the previous stage serves as the switching condition for whether to initiate this correction and judgment. If the environmental interference classification result determines that there is no environmental interference, the current grounding resistance measurement value will not enter this judgment process; if it is determined that there is environmental interference, the above-mentioned compensation, indexing, and comparison actions will be executed sequentially. For example, if a branch box in a coastal industrial area is within a short time window after a thunderstorm, the current grounding resistance measurement value R0 is 3.1 ohms, which appears to be below the 4-ohm safety threshold. However, after a deterioration adjustment amount C totaling 1.6 ohms of compensation, the grounding resistance correction value Rc reaches 4.7 ohms, exceeding the safety threshold of the corresponding row item for this branch box. Therefore, the grounding resistance of this branch box is determined to be falsely compliant. The false compliance judgment conclusion is written back to the judgment result field of the emergency power outage control process according to the unique number of the branch box, serving as the basis for whether to perform subsequent blocking measures on the branch box.

[0058] Step S105: When the judgment conclusion is false compliance, a preset interlocking control command is generated, and the deterioration adjustment amount is added to the interlocking control command and sent to the incoming switch controller of the low-voltage circuit where the branch box is located to forcibly maintain the open state.

[0059] For cable branch boxes whose compliance determination is false, the unique number of the branch box, the false compliance determination, and the interlocking action field are encapsulated according to a preset interlocking control instruction format. The degradation adjustment amount is also written as an additional field into the load area of ​​the interlocking control instruction to obtain an interlocking control instruction with degradation adjustment amount. According to the interlocking control instruction with degradation adjustment amount, the instruction is sent to the incoming switch controller of the low-voltage circuit via fieldbus according to the circuit identifier of the low-voltage circuit where the branch box is located. After receiving the interlocking control instruction, the incoming switch controller locks the closing circuit of the incoming switch and maintains its open state. At the same time, the degradation adjustment amount is retained in the controller's local register as the reference parameter for unlocking determination, so that the cable branch box is in a forced open state.

[0060] Optionally, during subsequent unlocking determination, the incoming switch controller will superimpose and correct the real-time collected temperature value of the cable branch box with the deterioration adjustment amount to obtain the corrected temperature value. Then, the corrected temperature value will be compared with the original determination threshold. When the corrected temperature value is continuously lower than the original determination threshold for more than 10 minutes, it is determined that the branch box has returned to normal, and the controller will automatically release the lockout and allow the closing operation.

[0061] It should be noted that the interlocking control command is a fixed message structure agreed upon between the emergency power-off control device and the incoming switch controller. Its load area is arranged in the order of the branch box unique number, false compliance judgment conclusion, interlocking action field and issuance time. The field length and field type are all agreed upon in advance in the communication protocol.

[0062] In one possible implementation, after the emergency power outage control device retrieves the record whose judgment conclusion is false compliance according to the unique number of the cable branch box, it fills in the corresponding field according to the above message structure, and writes the degradation adjustment amount output in the previous stage as an additional field into the load area of ​​the interlocking control command.

[0063] Specifically, the introduction of the additional field allows the interlocking control command to simultaneously carry a forced tripping command and the current degradation resistance compensation benchmark of the branch box. Upon receiving this, the incoming line switch controller can retain the degradation adjustment amount in its local register as a reference benchmark for subsequent unlocking determination. Further, the interlocking control command with the degradation adjustment amount is sent to the incoming line switch controller of the low-voltage circuit via the fieldbus according to the circuit identifier of the low-voltage circuit where the branch box is located. In one embodiment, the fieldbus uses shielded twisted-pair cable, and the communication rate is as specified in the protocol. After receiving the interlocking control command, the incoming line switch controller performs field parsing on the load area, extracting the interlocking action field and the degradation adjustment amount. For example, the incoming line switch controller has an internal tripping and closing drive circuit. Upon receiving the interlocking action field, the drive circuit inserts an interlocking relay contact into the power supply branch of the closing coil. The normally open interlocking relay contact is disconnected, preventing the closing coil from being excited by a remote or local closing command, and the main contacts of the incoming line switch remain in the open state.

[0064] In one embodiment, the local register is implemented with non-volatile memory, and the degradation adjustment remains valid even after the controller loses power.

[0065] It is understood that the cable branch box is in a forced open state while the locking relay contact remains normally open, and the low-voltage circuit outgoing side remains de-energized.

[0066] Step S106: For the branch box in the forced tripping state, remeasure the grounding resistance and collect soil moisture before releasing the lockout. Obtain the grounding resistance remeasurement value, the real-time soil moisture value and the grounding resistance recovery range after power failure. Combine the deterioration adjustment amount to confirm that the grounding has stabilized and met the standard.

[0067] For the cable branch box in a forced trip state, before the lockout is released, the grounding resistance is reread by the online grounding resistance monitoring terminal built into the box to obtain a remeasured grounding resistance value. Simultaneously, a humidity sampling probe buried around the grounding electrode collects soil volumetric moisture content to obtain a real-time soil humidity value. The remeasured grounding resistance value and the real-time soil humidity value are paired and stored in the database with a unified timestamp. Based on the archived grounding resistance reading sequence from the forced trip time to the current remeasurement time, the lowest reading in the sequence is extracted. The remeasured grounding resistance value is subtracted from the lowest reading to obtain the grounding resistance recovery amplitude after power failure. This recovery amplitude reflects the degree to which the grounding resistance recovers to its true state after the ambient humidity decreases over time. A joint determination is performed based on the rise in grounding resistance and the degradation adjustment amount stored in the local register of the incoming switch controller. If the remeasured grounding resistance value minus the degradation adjustment amount is lower than or equal to the safety threshold corresponding to the branch box, and the real-time soil moisture value falls back into the preset humidity baseline range, and the rise exceeds the preset stability threshold, then it is confirmed that the grounding of the cable branch box has been stably up to standard.

[0068] It should be noted that after the cable branch box is forced to remain in the open state by the interlocking control command with attached degradation adjustment, it enters the stability observation stage before the interlock is released.

[0069] In one embodiment, the emergency power outage control device periodically triggers the built-in online grounding resistance monitoring terminal of the box to reread the grounding resistance according to a preset retesting cycle, obtaining the retested grounding resistance value. The retesting cycle is determined according to the soil type: 30 minutes for sandy soil or dry environments, 2 hours for clay or humid environments, and 1 hour for general soils. Simultaneously, a moisture sampling probe buried in the soil around the grounding electrode synchronously collects the soil volumetric moisture content according to the same retesting cycle, obtaining the real-time soil moisture value. The retested grounding resistance value and the real-time soil moisture value are written to the maintenance database in pairs with a unified timestamp and stored in the retesting record area of ​​the branch box. Each record includes the branch box identifier, timestamp, grounding resistance retesting value in ohms, and real-time soil moisture value in percentage.

[0070] Specifically, from the moment the cable branch box is forcibly tripped, the online monitoring terminals for grounding resistance do not stop sampling, but continuously transmit the grounding resistance reading sequence back to the maintenance database according to the background rhythm. Each reading is accompanied by a timestamp, and the lowest reading in the sequence corresponds to the instantaneous state after the power outage when the soil moisture has not yet subsided and the resistance value is suppressed to its lowest point. Let the grounding resistance remeasurement value be Rf, and the lowest reading in the reading sequence be Rmin, then the rise in grounding resistance after the power outage is... For example, if a branch box is forcibly tripped after a thunderstorm, the lowest reading Rmin is approximately 2.8 ohms. After 2 hours of drying, the remeasured grounding resistance Rf is approximately 4.6 ohms. Therefore, the grounding resistance recovery amplitude ΔR is approximately 1.8 ohms. Furthermore, the preset humidity baseline interval is calculated in advance based on multi-year historical soil volumetric moisture content data for the current month and time period at the branch box's geographical location. The historical mean is denoted as μ, the standard deviation as σ, and the lower limit of the interval is... Upper limit of the interval When the real-time soil moisture value falls back within the specified range, it indicates that the ambient humidity has returned to normal. The preset stability threshold is obtained by statistically analyzing historical data on the recovery amplitude of similar power outage events in the distribution network area where the branch box is located. The 75th percentile of all historical recovery amplitudes is taken as the threshold value, which is typically between 1.5 ohms and 2.5 ohms. When the monitored recovery amplitude ΔR exceeds the stability threshold, and the resistance change rate is less than 0.05 ohms per 10 minutes within the past 30 minutes, it is determined that the grounding resistance has recovered from a wet state to a stable state.

[0071] In one embodiment, the joint determination is performed as follows: First, the grounding resistance remeasurement value Rf is compared with the aforementioned degradation adjustment amount C stored in the local register of the incoming switch controller, wherein the degradation adjustment amount C records the resistance offset value of the branch box grounding device caused by corrosion and loosening, and is calculated... First, obtain the current true resistance Rt after deducting the effects of degradation; second, compare Rt with the safety threshold Rs corresponding to the branch box, requiring Rt ≤ Rs; third, require the real-time soil moisture value to fall back within the preset moisture baseline range; fourth, require the grounding resistance rise amplitude ΔR to exceed the preset stability threshold, which is typically between 0.5 ohms and 2 ohms. When all four conditions are met simultaneously, it is confirmed that the grounding of the cable branch box has been stably up to standard.

[0072] Understandably, if any condition is not met, the current retest will not trigger the release of the lockout, and the cable branch box will continue to maintain the forced trip state, waiting for the next retest cycle to re-execute the above judgment process. For example, if the retested grounding resistance Rf of a branch box is 4.6 ohms and the degradation adjustment C is 1.0 ohm, then Rt is 3.6 ohms, which is less than the safety threshold of 4 ohms for that branch box; at the same time, the real-time soil moisture value falls back to the baseline range, and the rise ΔR is greater than the stability threshold, confirming that the grounding of the branch box has stabilized and met the standard. The confirmation conclusion is written back to the retest judgment field of the emergency power outage control process according to the unique number of the branch box, as a prerequisite for releasing the lockout and restoring power.

[0073] Step S107: After confirming that the grounding has been stable and meets the standards, generate a power restoration command and drive the incoming line switch to close and release the forced tripping state. Collect the switch closing signal and the circuit voltage signal as status feedback. Write back the conclusion that the grounding has been stable and meets the standards, the grounding resistance remeasurement value and the soil moisture value to the deterioration status file, update the historical trajectory of the degree of corrosion and the degree of connection loosening, and refresh the current control status in the emergency power outage control system.

[0074] For cable branch boxes whose grounding has been confirmed to be stable and up to standard, the unique number of the branch box, the stability achievement conclusion, and the unlocking action field are encapsulated according to the preset power restoration command format. This is then sent via fieldbus to the incoming switch controller of the low-voltage circuit where the branch box is located. The incoming switch controller releases the normally open state of the lockout relay contact loaded in the closing circuit, driving the incoming switch to switch from the forced open state to the closed state, thus re-energizing the low-voltage circuit. For the cable branch box after the incoming switch closing action is completed, the closing signal output by the auxiliary contact of the switch body and the voltage signal output by the voltage transformer on the circuit outgoing side are collected as status feedback. The stability achievement conclusion, the grounding resistance re-measurement value, the real-time soil moisture value, and the status feedback are written back to the corresponding record in the deterioration status file according to the unique number of the branch box, resulting in a file record containing the re-measurement data. Based on the historical value sequence of the corrosion degree field and the connection looseness field in the archive record containing the data of this retest, the current value is appended to the end of the two fields to form a historical trajectory update entry, and the current control status is flipped from the forced trip mark to the normal operation mark according to the unique number of the branch box, thus refreshing the current control status of the branch box in the emergency power outage control system.

[0075] It should be noted that the cable branch box has been jointly determined and confirmed to be grounding stable in the previous stage, and the confirmation conclusion has been written back to the retest judgment field of the emergency power outage control process.

[0076] In one possible implementation, the emergency power outage control device retrieves a record showing a stable and compliant status in the retest judgment field based on the unique number of the cable branch box. Then, it encapsulates the unique number of the branch box, the stability compliance conclusion, and the unlocking action field according to a preset power restoration command format, and sends this command via fieldbus to the incoming switch controller of the low-voltage circuit where the branch box is located. The power restoration command format uses a fixed-length data frame structure, sequentially including a frame header identifier field, a branch box unique number field, a retest conclusion field, an unlocking action field, a timestamp field, and a checksum field. The unlocking action field is 1 byte long; a value of 0x01 indicates that the power outage lock is released and power restoration is allowed; a value of 0x02 indicates that the lock is released but manual confirmation is required before power restoration; and a value of 0x00 indicates that the lock is maintained. When encapsulating the command, the control device assigns the unlocking action field value to 0x01 based on the retest conclusion showing stable compliance, and encapsulates it together with the branch box number and the current timestamp into a complete command frame, which is then sent to the target incoming switch controller via fieldbus.

[0077] Specifically, during the previous stage of interlocking, the closing circuit of the incoming line switch controller is connected in series with the interlocking relay contact, which remains normally open to prevent the closing coil from being energized. Upon receiving the power restoration command, the incoming line switch controller parses the unlocking action field, drives the interlocking relay to reset, and restores the interlocking relay contact from the normally open state to the normally closed state, reconnecting the closing circuit. Further, the incoming line switch controller then sends a closing pulse to the closing coil, causing the main contacts of the incoming line switch to switch from the open position to the closed position, restoring the busbar of the low-voltage circuit where the cable branch box is located from an undervoltage state to a energized state. For the cable branch box after the incoming line switch closing action is completed, the closing signal output by the auxiliary contacts of the switch body and the voltage signal output by the voltage transformer on the circuit's outgoing side are collected. A closing signal value of 1 indicates that the main contacts are fully closed, and a voltage signal value of 1 indicates that the three-phase voltage on the circuit's outgoing side is within the rated range. When both signals are simultaneously 1, the status feedback for this power restoration is entered into the database.

[0078] Specifically, the file rewriting process locates the corresponding record in the deterioration status file based on the unique branch box number. A new entry is added to the retest data area of ​​this record. This entry includes the current stability compliance conclusion, the retested grounding resistance value, the real-time soil moisture value, the closing signal value, the live signal value, and the time of this retest. The retest data area arranges the previous entries in chronological order to obtain the file record containing the current retest data. The file rewriting process locates the corresponding record in the deterioration status file based on the unique branch box number. A new entry is added to the retest data area of ​​this record. This entry includes the current stability compliance conclusion, the retested grounding resistance value, the real-time soil moisture value, the closing signal value, the live signal value, and the time of this retest. The retest data area arranges the previous entries in chronological order to obtain the file record containing the current retest data. For example, the conclusion that a branch box in a coastal industrial zone has achieved stable compliance, the grounding resistance retest value is 4.6 ohms, the real-time soil moisture value is 19%, the closing signal value is 1, the live signal value is 1, and the retest time is 11:20 on June 14, 2026, are all added as new entries to the retest data area.

[0079] It is understood that, in addition to the retest data area, the degradation status file also includes a corrosion degree field and a connection looseness field. These two fields record the values ​​of the branch box for each test in chronological order of the test date. The corrosion degree degradation score corresponding to this retest is synthesized from the latest on-site inspection data, and the percentage decrease in connection looseness corresponding to this retest is also synthesized from the latest on-site inspection data. These two values ​​are appended to the end of the corrosion degree field and the connection looseness field, respectively, forming historical trajectory update entries. Furthermore, the emergency power outage control system maintains a current control status table with the branch box's unique number as the primary key. Each row in the table records the current control status flag of the branch box. After power restoration, the flag for the corresponding row of the branch box changes from forced tripping to normal operation. After the flag reversal is recorded, the current control status of the branch box in the emergency power outage control system is refreshed. The cable branch box thus completes the full closed loop from this round of ground fault power outage to power restoration. Subsequent inspection data can be generated based on the file records containing this retest data and the newly written historical trajectory update entries.

[0080] It should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. A method for emergency power outage control in case of grounding abnormality in a low-voltage cable branch box, characterized in that, The method includes: The instantaneous grounding resistance and soil moisture of the cable branch box after a grounding anomaly are obtained. The temporal characteristics of the grounding resistance and the abrupt change characteristics of the moisture are extracted, and a classification judgment is performed to obtain the environmental interference classification results and interference intensity. When environmental interference is detected, the degree of corrosion of the grounding electrode and the degree of looseness of the down conductor connection are read from the deterioration status file of the cable branch box, and the deterioration adjustment amount is determined in combination with the interference intensity. If there is no environmental interference, the current grounding resistance measurement value is deemed qualified, a power restoration command is generated to re-energize the circuit, the switch closing position and the circuit voltage signal are collected as execution feedback information, and a normal record text is generated according to the normal record template. Based on the aforementioned degradation adjustment amount, the degradation status file, the current grounding resistance measurement value, and the environmental interference classification result, determine whether the branch box grounding resistance is falsely compliant; When the judgment conclusion is false compliance, a preset interlocking control command is generated, and the deterioration adjustment amount is added to the interlocking control command and sent to the incoming switch controller of the low-voltage circuit where the cable branch box is located, forcibly maintaining the open state. For branch boxes in a forced tripping state, the grounding resistance is remeasured and soil moisture is collected simultaneously before the interlock is released. The grounding resistance remeasurement value, the real-time soil moisture value, and the grounding resistance rise after power failure are obtained. Combined with the aforementioned deterioration adjustment amount, it is confirmed that the grounding has stabilized and met the standards. Drive the incoming line switch to close and release the forced trip state, write the grounding resistance remeasurement value and the real-time soil moisture value back to the deterioration state file, update the historical trajectory of corrosion degree and connection loosening degree and refresh the current control state.

2. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, The instantaneous measurement of grounding resistance and soil moisture of the cable branch box after a grounding anomaly occurs includes: The instantaneous resistance value is read by the grounding resistance online monitoring terminal built into the box, and the soil volume moisture content reading is obtained synchronously by the moisture sampling probe buried in the soil around the grounding electrode. The instantaneous resistance value and the soil volume moisture content reading are aligned with the execution time according to a unified timestamp to obtain a resistance-humidity pairing sequence marked with timestamps. A sliding window is formed by extending forward and backward for a fixed duration from the power failure trigger time.

3. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 2, characterized in that, The extraction of grounding resistance timing characteristics and humidity abrupt change characteristics includes: The slope of the resistance decrease is fitted using the least squares method for the instantaneous resistance value subsequence within the sliding window. The maximum drop in resistance value is extracted and combined with the sequence fluctuation variance to form the time series feature of the grounding resistance. The first-order difference is obtained point by point for the soil volume moisture content subsequence within the same window to obtain the humidity increment. The humidity increment is compared with the humidity baseline of the same month and time period in history. Segments that deviate from the baseline and show a steep upward trend are marked as humidity mutation inflection points. The peak value of the humidity increment is taken and the time offset of the humidity mutation inflection point relative to the power outage trigger time is recorded. The combination is used to obtain the humidity mutation feature.

4. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, The process involves reading the degree of corrosion of the grounding electrode and the degree of looseness of the down conductor connection based on the deterioration status file of the cable branch box, and determining the deterioration adjustment amount in conjunction with the interference intensity, including: A file retrieval request is initiated to the distribution network operation and maintenance database based on the unique number of the cable branch box. The deterioration status file is pre-constructed based on the grounding electrode material label, anti-corrosion process type, installation year, and the down conductor connection status recorded in previous on-site inspections. The degree of corrosion of the grounding electrode is expressed as a deterioration score, which is a combination of the corrosion area ratio and the remaining cross-sectional thickness. The degree of looseness of the down conductor connection is expressed as the percentage decrease in the residual tightening torque relative to the factory rated torque. The attenuation coefficient is indexed from the attenuation lookup table according to the material label and anti-corrosion process type. The deterioration score is multiplied by the attenuation coefficient to obtain the corrosion correction component. The percentage decrease is multiplied by the attenuation coefficient to obtain the connection correction component. The two correction components are summed to obtain the basic deterioration adjustment amount. The interference intensity is used as a scaling factor and multiplied by the basic deterioration adjustment amount to obtain the deterioration adjustment amount.

5. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, If there is no environmental interference, the current grounding resistance measurement value is deemed qualified, a power restoration command is generated to re-energize the circuit, the switch closing position and circuit voltage signals are collected as execution feedback information, and a normal record text is generated according to the normal record template, including: The cable branch box's unique number and reading qualification conclusion are packaged according to the preset power restoration instruction format and sent to the incoming switch controller to drive the incoming switch to the closed state; the closing signal of the auxiliary contact of the switch body and the voltage transformer's live signal are collected and combined into the execution feedback information, and the restoration operation time, current grounding resistance measurement value and the execution feedback information are filled in according to the normal record template.

6. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, The determination of whether the branch box grounding resistance is falsely compliant based on the degradation adjustment amount, the degradation status file, the current grounding resistance measurement value, and the environmental interference classification result includes: For cable branch boxes with environmental interference labels, a grounding resistance correction value is determined based on the degradation adjustment amount and the current grounding resistance measurement value. A safety threshold matching the cable branch box is indexed from a pre-established threshold mapping table based on the grounding electrode material label and anti-corrosion process category in the degradation status file. This threshold mapping table pre-records the limit benchmarks for low-voltage distribution network grounding resistance according to different material and process combinations. The grounding resistance correction value is compared with the safety threshold. If the grounding resistance correction value exceeds the safety threshold, the grounding resistance of the branch box is determined to be falsely compliant; otherwise, it is determined to be truly compliant.

7. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, When the judgment conclusion is false compliance, a preset interlocking control command is generated, and the degradation adjustment amount is added to the interlocking control command and sent to the incoming switch controller of the low-voltage circuit where the cable branch box is located, forcibly maintaining the open state, including: The cable branch box's unique number, false compliance judgment conclusion, and interlocking action field are encapsulated according to the preset interlocking control instruction format. The degradation adjustment amount is written as an additional field into the interlocking control instruction load area and sent to the incoming switch controller via the fieldbus. The incoming switch controller locks the incoming switch closing circuit and maintains the open state, and retains the degradation adjustment amount in the local register.

8. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, For the branch box in the forced tripping state, before releasing the lockout, the grounding resistance is remeasured and soil moisture is collected simultaneously to obtain the remeasured grounding resistance value, the real-time soil moisture value, and the rise in grounding resistance after power failure, including: The grounding resistance remeasurement value is obtained by rereading the grounding resistance online monitoring terminal built into the enclosure, and the soil moisture value is obtained by synchronously collecting the soil volume moisture content by the humidity sampling probe; the lowest reading is extracted from the archived grounding resistance reading sequence between the forced tripping time and the current remeasurement time, and the grounding resistance remeasurement value is subtracted from the lowest reading to obtain the grounding resistance recovery amplitude after power failure.

9. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, The confirmation that the grounding has stabilized and met the standards, based on the aforementioned degradation adjustment amount, includes: The difference between the remeasured grounding resistance value and the deterioration adjustment amount is compared with the safety threshold corresponding to the cable branch box. If the difference is lower than or equal to the safety threshold, and the real-time soil moisture value falls back into the preset humidity baseline range, and the rise in grounding resistance after power failure exceeds the preset stability threshold, then it is confirmed that the grounding of the cable branch box has been stably up to standard.

10. The emergency power outage control method for abnormal grounding of low-voltage cable branch boxes according to claim 1, characterized in that, The process of driving the incoming line switch to close and release the forced tripping state, and writing the remeasured grounding resistance value and the real-time soil moisture value back to the deterioration status file includes: The cable branch box's unique number, stability compliance conclusion, and unlocking action field are encapsulated according to the preset power restoration command format. The command is then sent to the incoming switch controller via fieldbus to release the normally open state of the closing circuit interlock relay and drive the incoming switch to the closed state. The closing signal of the switch auxiliary contact and the voltage transformer's live signal are collected as status feedback. The stability compliance conclusion, the grounding resistance remeasurement value, the real-time soil moisture value, and the status feedback are all written back to the deterioration status file.

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