Methods for analyzing abnormal trends in secondary circuit monitoring data

Abstract

This invention discloses a method for analyzing abnormal trends in secondary circuit monitoring data. It acquires secondary circuit models, monitoring data, and operational status data, and establishes topological relationships between protection devices, transformer windings, terminal blocks, neutral lines, grounding wires, N600 branches, monitoring terminals, and temperature sensors. Data segments are divided according to operational status, and topological mirror loops of the target circuit are selected. Time alignment is performed on the mirror loop data to generate common current and temperature trend baselines. This invention relates to the field of substation secondary circuit status monitoring technology. This method extracts recurring common current and temperature trends with consistent changing directions from multiple topological mirror loops and uses median fusion to generate a common trend baseline. This can weaken common fluctuations caused by load changes, operating mode switching, and ambient temperature changes, highlighting the local abnormal trends formed by the target circuit itself.

Description

Technical Field

[0001] This invention relates to the field of secondary circuit status monitoring in substations, and more specifically, to a method for analyzing abnormal trends in secondary circuit monitoring data. Background Technology

[0002] Substation secondary circuits undertake relay protection, measurement, control, and signal transmission functions. Anomalies in these circuits often manifest as slow shifts in neutral current, grounding current, N600 current, or terminal temperature. Existing technologies mostly set criteria for single fault types. For example, CN120254472A locates multi-point grounding branches by comparing the waveform distance between the neutral grounding current and the currents in each branch of the PT secondary circuit; CN120639597A establishes logical and physical connection link models and locates secondary system fault nodes based on anomaly weights; CN114935705B comprehensively analyzes DC line differential current and transient temperature distribution to identify latent faults. While these solutions improve the ability to identify specific faults, they do not address the problem of overlapping common trends and local anomalies caused by load changes, operating state switching, and ambient temperature. They also fail to utilize structurally similar circuits to form a baseline for comparison and lack joint analysis of the topological propagation of local residuals, electro-thermal response time delays, and cross-cycle evolution processes. Therefore, it is necessary to propose a method for analyzing abnormal trends in secondary loop monitoring data that can separate common trends, locate abnormal locations, and determine the stage of abnormal development. Summary of the Invention

[0003] The purpose of this invention is to provide a method for analyzing abnormal trends in secondary circuit monitoring data, which solves the problems of existing secondary circuit monitoring methods that make it difficult to distinguish between common operating trends and local abnormal trends, difficult to use the response time delay between current and temperature to locate abnormal locations, and difficult to determine the stage of abnormal development.

[0004] This invention achieves the above objective through the following technical solution: a method for analyzing abnormal trends in secondary circuit monitoring data, the method comprising:

[0005] The substation secondary circuit model, continuous monitoring data, and operating status data are acquired. The continuous monitoring data includes neutral current, grounding current, N600 current, and terminal temperature. The operating status data includes circuit breaker status, pressure plate status, air switch status, maintenance status, and load status. Based on the time of change of the state combination of the operating status data, the continuous monitoring data is divided into operating status data segments. For the target circuit, according to the protection function, transformer winding type, grounding method, terminal connection level and monitoring point location, multiple topological mirror circuits that are in the same operating state as the target circuit are selected from the secondary circuit model. Time alignment is performed on the monitoring data of the target loop and each topological mirror loop within the same operating state data segment. The common current trend and common temperature trend that recur and change in the same direction in each topological mirror loop are extracted to generate the common current trend baseline and common temperature trend baseline. Subtract the current common trend baseline from the current monitoring trend of the target circuit to obtain the local current trend residual. Subtract the temperature common trend baseline from the temperature monitoring trend of the target circuit to obtain the local temperature trend residual. Based on the distribution direction and amplitude attenuation relationship of the local trend residuals corresponding to each monitoring point along the secondary circuit topology, determine the local anomaly candidate region. The effective starting point of change of the local trend residual of the current and the response starting point of the local trend residual of the temperature are determined. The time difference between the two is used as the electro-thermal response time delay. The stable electro-thermal response relationship is judged based on the degree of dispersion of the time delay and the direction of residual change in each operating cycle. Using the local current trend residual as the first trajectory variable and the local temperature trend residual after compensation according to the electro-thermal response time delay as the second trajectory variable, an electro-thermal time delay evolution trajectory is constructed according to the sampling time sequence. Based on the rising segment, falling segment, hysteresis degree, and cross-operational cycle expansion characteristics of the electro-thermal time-delay evolution trajectory, and combined with the propagation relationship of local trend residuals within the local anomaly candidate region, the anomaly type, anomaly location, and anomaly development stage are determined.

[0006] Furthermore, the process of establishing the secondary loop model includes: The protection device, transformer winding, terminal block, monitoring terminal and temperature sensor are set as topology nodes, and the neutral line, grounding line, N600 branch and terminal connection line are set as topology edges. Configure protection function identifiers, transformer winding type identifiers, grounding method identifiers, terminal connection level identifiers, and monitoring point location identifiers for each topology node, and associate the continuous monitoring data with the corresponding topology node or topology edge; The connection direction, upstream and downstream relationships, and shared grounding relationship between topology nodes are determined based on the secondary wiring relationship, forming a directed topology structure used to characterize the propagation path of local trend residuals.

[0007] Furthermore, the process of dividing the running status data segment includes: The status of circuit breakers, pressure plates, air switches, and maintenance are discretely coded, and the load status is coded according to the load rate range. The codes are then combined into an operating status code. The moment when the running status code changes is determined as the status segment node, and the data between adjacent status segment nodes is divided into a running status data segment. The state transition periods are deleted from the beginning and end of each running state data segment, and the deleted data is used for topology mirror loop screening and common trend baseline generation.

[0008] Furthermore, the screening process for the topological mirror loop includes: Among the secondary circuits with the same operating status code as the target circuit, they are selected in sequence according to the following conditions: same protection function, same transformer winding type, same grounding method, same terminal connection level, and same relative position of monitoring point. The secondary loops that meet all the screening criteria are identified as first-level topological mirror loops. When the number of first-level topology mirror circuits is less than 3, under the condition that the operating status code, protection function, transformer winding type and grounding method are the same, the terminal connection level consistency condition and the monitoring point relative position consistency condition are cancelled in turn, the newly added secondary circuits are determined as supplementary topology mirror circuits, and the screening level corresponding to each topology mirror circuit is recorded.

[0009] Furthermore, the process of generating the common trend baseline includes: The continuous monitoring data of the target loop and multiple topological mirror loops are resampled to a unified sampling time, and the start time of the corresponding running state data segment is used as the time alignment reference. Within a continuous sliding window, determine the direction of current change, the direction of temperature change, and the duration of the trend for each topological mirror loop. When the same direction of change is repeated in at least 60% of the topological mirror loops, and the duration of the trend is not less than 50% of the duration of the corresponding sliding window, the change is identified as a common trend component. The first-level topological mirror loop is preferred for generating a common trend baseline; When there are fewer than 3 mirror loops in the first-level topology, the supplementary mirror loops are added to the calculation of the common trend baseline, and the median of the common trend components at the same sampling time is fused to obtain the current common trend baseline and the temperature common trend baseline.

[0010] Furthermore, the process of determining the local anomaly candidate region includes: From the historical operating status data segments with the same operating status and confirmed to be without abnormalities, the absolute values ​​of the local trend residuals of current and temperature are statistically analyzed, and the 99th percentile values ​​of their respective statistical distributions are determined as the current residual threshold and temperature residual threshold. Monitoring points where the local trend residual of current or the local trend residual of temperature continuously exceeds the corresponding residual threshold are identified as abnormal candidate monitoring points. The upstream and downstream associated monitoring points of the anomaly candidate monitoring points are obtained along the directed topology, and the residual propagation direction is determined according to the time sequence of the local trend residuals of each associated monitoring point crossing the corresponding residual threshold. The residual amplitudes of adjacent monitoring points are compared along the residual propagation direction, and the topological nodes whose residual amplitudes increase for the first time or do not continue to decay, along with their adjacent topological edges, are identified as local anomaly candidate regions.

[0011] Furthermore, the process for determining the electro-thermal response time delay includes: Based on historical operating status data segments with the same operating status and confirmed to be without abnormalities, the thresholds for current residual change rate and temperature residual change rate are determined respectively. The first sampling moment in which the local trend residual of the current or its rate of change continuously exceeds the corresponding threshold and maintains the same direction of change is determined as the effective starting point of change. Starting from the effective change point, the first sampling moment in which the local temperature trend residual or its rate of change continuously exceeds the corresponding threshold and maintains the same direction of change is determined as the response starting point; Obtain the electro-thermal response time delay for no less than 5 operating cycles. When the deviation of each electro-thermal response time delay from its median does not exceed 20%, and the local trend residual of current and the local trend residual of temperature change in the same direction within each operating cycle, the stable electro-thermal response relationship is determined to exist.

[0012] Furthermore, the process of constructing the electro-thermal time-delay evolution trajectory includes: The local temperature trend residual is shifted forward along the time axis by the electro-thermal response time delay, so that the response start point is aligned with the effective change start point. Using the local current trend residual at each sampling time as the abscissa and the local temperature trend residual after translation at the same sampling time as the ordinate, the trajectory coordinate points are connected according to the sampling time sequence. The trajectory rising segment is determined by the process of the local trend residual of the current increasing from the initial value to the peak value, and the trajectory falling segment is determined by the process of the local trend residual of the current falling back from the peak value. Calculate the temperature local trend residual interval between the rising and falling segments within the same current local trend residual interval, and use the interval to characterize the degree of trajectory hysteresis.

[0013] Furthermore, the process of determining the anomaly type, anomaly location, and anomaly development stage includes: When the local trend residual of current changes before the local trend residual of temperature, there is a stable electro-thermal response relationship, and the trajectory envelope of the continuous operating cycle expands sequentially, the anomaly type is determined to be current-induced heating type progressive anomaly. When the local current trend residual continues to increase and a stable electro-thermal response relationship is not formed, the anomaly type is determined to be a current path anomaly based on the neutral line, ground line, or N600 branch to which the local anomaly candidate area belongs. When the local temperature trend residual continues to increase and there is no prior change in the local current trend residual, the anomaly type is determined to be a local heat accumulation anomaly. The topological node whose local trend residual crosses the corresponding residual threshold earliest and whose residual amplitude first increases along the propagation direction is identified as an anomaly location. Based on the number of trajectory envelope expansions, changes in trajectory hysteresis, and continuous exceeding of limits in local trend residuals during continuous operation cycles, the abnormal development stage is determined as the abnormal initiation stage, abnormal development stage, or abnormal aggravation stage.

[0014] Furthermore, the process of outputting the analysis results includes: Write the anomaly type, anomaly location, anomaly development stage, electro-thermal response time delay, and local anomaly candidate region into the attribute fields of the corresponding topology node or topology edge. The target loop, topological mirror loop, current common trend baseline, temperature common trend baseline, current local trend residual, temperature local trend residual, and electro-thermal time delay evolution trajectory are displayed according to the associated data segments of the operating status. Generate an anomaly trend analysis record that includes target loop identifier, operating status code, anomaly type, anomaly location, anomaly development stage, residual limit exceedance start and end times, and electro-thermal response time delay.

[0015] The beneficial effects of this invention are as follows: 1. This invention selects topological mirror circuits based on operating status, protection function, transformer winding type, grounding method, terminal connection level and relative position of monitoring points. Circuits with similar structures and consistent operating status are used as the reference objects for the target circuits, which can avoid the reference deviation caused by different circuit structures and different operating conditions.

[0016] 2. This invention extracts recurring common current and temperature trends with consistent direction of change from multiple topological mirror loops, and uses median fusion to generate a common trend baseline. This can reduce the common fluctuations caused by load changes, operation mode switching and ambient temperature changes, and highlight the local abnormal trends formed by the target loop itself.

[0017] 3. This invention calculates the difference between the target loop monitoring trend and the corresponding common trend baseline, and combines the local trend residual along the propagation direction of the secondary loop directional topology and the amplitude attenuation relationship to determine the local anomaly candidate area, which can locate the anomaly range to the terminal, connection line, neutral line, grounding line or N600 branch.

[0018] 4. This invention determines the electro-thermal response time delay by detecting the effective change starting point of the local current trend residual and the response starting point of the local temperature trend residual, and verifies the stability of the time delay using multiple operating cycles. It can distinguish between current-induced heating anomalies, current path anomalies, and local heat accumulation anomalies.

[0019] 5. This invention constructs an electro-thermal time-delay evolution trajectory through time-delay compensation and extracts the trajectory's rising segment, falling segment, hysteresis degree, and cross-cycle expansion characteristics. It can identify the stages of abnormal initiation, abnormal development, and abnormal aggravation, realizing the transformation from single-point over-limit alarm to abnormal evolution process analysis. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the overall method of the present invention; Figure 2 This is a schematic diagram of the secondary loop topology model and the topological mirror loop screening of the present invention; Figure 3 This is a schematic diagram of the common trend baseline and local trend residual analysis of the present invention; Figure 4 This is a schematic diagram of the electro-thermal response time delay and the electro-thermal time delay evolution trajectory of the present invention; Figure 5 This is a schematic diagram of the anomaly localization and analysis results output of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. It should be understood that the described embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention. Adaptive adjustments made by those skilled in the art to the sampling period, analysis window, number of monitoring points, and judgment threshold without departing from the technical concept of the present invention should all fall within the scope of protection of the present invention. The present invention identifies and locates abnormal trends in secondary circuits through the division of operating status data segments, screening of topological mirror loops, generation of common trend baselines, extraction of local trend residuals, detection of electro-thermal response time delays, and analysis of electro-thermal time delay evolution trajectories.

[0022] In this invention, current is uniformly measured in milliamperes (mA), temperature in degrees Celsius (°C), time in seconds (sec), current change rate in milliamperes per second (mA / s), and temperature change rate in degrees Celsius per second (°C / s). The local trend residuals of current and temperature are used as two coordinate variables of the electro-thermal time-delay evolution trajectory, and data with different dimensions are not directly added together.

[0023] Example 1: Please see Figures 1 to 5 As shown, this invention provides a method for analyzing abnormal trends in secondary circuit monitoring data, applied to an online monitoring platform for substation secondary circuits. The online monitoring platform is communicatively connected to protection devices, a secondary circuit monitoring terminal, a terminal temperature sensor, and an operating status acquisition interface. The secondary circuit monitoring terminal is used to collect neutral current, grounding current, and N600 current. The current monitoring channel's range is set to 0–500 mA, with a resolution no greater than 0.1 mA and a measurement error no greater than ±1%. The upper limit of the current monitoring channel's range is determined based on the maximum effective current of the same type of circuit in the target substation over the past year, and the upper limit is no less than 1.5 times the maximum effective current to retain a margin for abnormal current monitoring. The terminal temperature sensor is installed at the terminal block connection, grounding connection, or N600 branch connection, with a temperature measurement range of… The temperature range is 20–120 ℃, with a resolution of no more than 0.1 ℃ and a measurement error of no more than ±0.5 ℃. The temperature measurement range covers the ambient temperature of the cabinet, the normal operating temperature rise of the terminals, and the abnormal heating temperature. The original sampling period for current monitoring data is 1 s, and the original sampling period for terminal temperature data is 10 s. To ensure a consistent time scale between the current monitoring data and the terminal temperature data, the current monitoring data is resampled according to a uniform analysis period of 10 s, and the median of the current sampled values ​​within each analysis period is used as the current value at the corresponding analysis time. The timestamp deviation between the resampled current data and the temperature data is no more than 1 s. Using the median for resampling reduces the impact of isolated outliers caused by switching transients, electromagnetic interference pulses, and communication jitter on the trend analysis results.

[0024] The method in this embodiment includes the following steps: S1. Establish the topology model of the secondary loop. Obtain the substation's secondary wiring diagram, terminal block diagram, cabinet configuration data, and on-site verified wiring records. Based on this data, establish a secondary circuit topology model. Designate protection devices, instrument transformer windings, terminal blocks, secondary circuit monitoring terminals, and terminal temperature sensors as topology nodes. Designate the neutral line, grounding wire, N600 branch, and terminal connection lines as topology edges. Configure node identifiers, protection function identifiers, instrument transformer winding type identifiers, grounding method identifiers, terminal connection level identifiers, and monitoring point location identifiers for each topology node.

[0025] Protection function identifiers are used to distinguish between line protection circuits, busbar protection circuits, transformer protection circuits, and measurement circuits; transformer winding type identifiers are used to distinguish between protection windings and measurement windings; grounding method identifiers are used to distinguish between independent grounding and shared grounding; terminal connection level identifiers are used to indicate whether the monitoring point is located in the transformer side terminal layer, intermediate transfer terminal layer, protection device input terminal layer, or grounding point terminal layer.

[0026] The connection direction, upstream and downstream relationships, and common grounding relationships between each topology node are determined based on the secondary wiring direction. The signal transmission direction from the current transformer winding to the protection device is determined as the positive topology direction, and the topology association relationship corresponding to the common grounding point and the common N600 branch is recorded, thereby forming a directed topology structure.

[0027] Each monitoring channel is associated with a corresponding topology node or topology edge through a unique channel identifier, enabling neutral current, grounding current, N600 current, and terminal temperature to be mapped to specific terminals, connection lines, or grounding branches.

[0028] S2. Divide the running status data segment The status of circuit breakers, pressure plates, air switches, maintenance, and loads are acquired through the operation status acquisition interface, and each operation status is discretely encoded.

[0029] Circuit breaker status codes are either open or closed; switch plate status codes are either deactivated or activated; air switch status codes are either open or closed; and maintenance status codes are either maintenance or non-maintenance. Load status is categorized based on the load rate of the primary equipment corresponding to the target circuit. A load rate not exceeding 20% ​​is defined as a light load; a load rate greater than 20% but not exceeding 50% is defined as a low load; a load rate greater than 50% but not exceeding 80% is defined as a medium load; and a load rate greater than 80% is defined as a high load. Load status boundary values ​​are determined based on equipment operating procedures and historical load distribution. During the initial commissioning phase, the load rate distribution over the most recent 90 days is statistically analyzed, and boundary values ​​are selected around 20%, 50%, and 80% to ensure that the number of valid samples in each load interval is not less than 10% of the total sample size. This avoids situations where a particular load status lacks sufficient sample size to generate effective comparative data. The circuit breaker status code, pressure plate status code, air switch status code, maintenance status code, and load status code at the same sampling time are combined to form the operating status code. The operating status codes at adjacent sampling times are compared in chronological order. When the operating status code changes, the corresponding time is determined as the status segment node, and the monitoring data between two adjacent status segment nodes is divided into an operating status data segment.

[0030] Considering the transient disturbances that occur after circuit breaker operation, pressure plate engagement / disengagement, or air switch switching, 60 seconds of state transition data are deleted from both the beginning and end of each operating status data segment. This 60 seconds is determined based on at least 30 state transition processes.

[0031] Specifically: The time required for current monitoring data to recover to the normal fluctuation range after each state switch was statistically analyzed. These recovery times were then arranged in ascending order, and the recovery time covering at least 95% of the state switch processes was selected as the state switch transition duration. After deleting the state switch transition data, the effective duration of the operating status data segment should be no less than 30 minutes. Operating status data segments with an effective duration of less than 30 minutes are not included in the calculation of the common trend baseline, but are retained for state switch recording and transient anomaly verification.

[0032] S3, Filter topological mirror circuits For the target circuit to be analyzed, topology mirror circuits are selected from secondary circuits with the same operating status code as the target circuit. A topology mirror circuit refers to a secondary circuit that has the same or corresponding protection function, transformer winding type, grounding method, terminal connection level, and relative position of monitoring point as the target circuit, and is in the same operating status.

[0033] First, secondary circuits that share the same protection function, transformer winding type, grounding method, terminal connection level, and relative position of monitoring points as the target circuit are selected. These selected secondary circuits are then designated as first-level topology mirror circuits. The relative position of monitoring points is determined based on the number of topological edges from the monitoring point to the transformer winding, the protection device input terminal, and the grounding point. When two monitoring points correspond to the same terminal connection level and have the same number of topological edges from each of the three reference nodes, the relative positions of the two monitoring points are considered consistent.

[0034] When the number of first-level topological mirror loops is no less than 3, the first-level topological mirror loops are used to generate a common trend baseline.

[0035] When the number of mirrored circuits in the first-level topology is less than 3, the operating status code, protection function, transformer winding type and grounding method are kept the same, the screening condition of consistent terminal connection level is cancelled, and the newly added secondary circuit is determined as the first supplementary topology mirrored circuit.

[0036] When the total number of the first-level topological mirror loop and the first supplementary topological mirror loop is still less than 3, the screening condition of the relative position of the monitoring points is further removed, and the newly added secondary loop is determined as the second supplementary topological mirror loop.

[0037] When generating a common trend baseline, the first-level topological mirror loop is used first. If the number of first-level topological mirror loops is insufficient, they are added to the calculation in the order of the first supplementary topological mirror loop and the second supplementary topological mirror loop.

[0038] The number of topological mirror loops is set to 3 to 10. The lower limit is 3 to ensure that the common trend is supported by at least 3 independent loops; the upper limit is 10 to restrict loops with large topological differences from being included in the calculation of the common trend baseline.

[0039] When the number of loops that meet the screening criteria exceeds 10, the top 10 loops are selected in descending order of the relative position of the monitoring points, the terminal connection level, and the historical data integrity rate. The topology mirror loops are not determined by weighting.

[0040] S4, Common trend baseline for generated current and common trend baseline for temperature Monitoring data from the target loop and each topological mirror loop within the same operational status data segment are extracted and resampled according to a uniform analysis cycle of 10 seconds. Using the start time of the operational status data segment as the time alignment benchmark, the monitoring data of the target loop and each topological mirror loop are mapped to the same time axis. For data with a continuous missing duration not exceeding 30 seconds, linear interpolation is performed using the effective sampled values ​​before and after the missing interval. When the data missing rate within an operational status data segment exceeds 10%, this segment is not used to generate a common trend baseline.

[0041] The data missing percentage threshold is determined based on the data continuity required for trend analysis. Historical complete data is used for missing data simulation. When the missing percentage does not exceed 10%, the consistency rate of the trend direction before and after interpolation is no less than 95%. Therefore, 10% is used as the data segment validity threshold. Current and temperature sliding windows are set separately. The current sliding window duration is set to 60 seconds, and the temperature sliding window duration is set to 300 seconds.

[0042] The current sliding window duration is no less than 6 times the current unified analysis period, used to eliminate short-duration electromagnetic interference; the temperature sliding window duration is no less than 30 times the temperature sampling period, used to cover the thermal inertial response process of terminal temperature.

[0043] Within each sliding window, the difference between the first and last values ​​of the monitoring data for each topological mirror loop is calculated. When the difference between the first and last values ​​is greater than the corresponding trend change threshold, the sliding window is marked as an upward trend; when the difference between the first and last values ​​is less than the negative value of the corresponding trend change threshold, the sliding window is marked as a downward trend; the remaining sliding windows are marked as stable trends.

[0044] When the same direction of change occurs repeatedly in at least 60% of the topological mirror loops, and the duration of the change is not less than 50% of the duration of the corresponding sliding window, the change is identified as a common trend component.

[0045] The 60% repetition rate and 50% continuity rate are determined based on historical normal operation data. At least 30 normal operation cycles are selected, and the repetition and continuity rates are adjusted incrementally. The minimum rate that ensures a false identification rate of no more than 5% for normal operation data and a public load change identification rate of no less than 90% is chosen as the final determination rate.

[0046] The median trend values ​​of the topological mirror loops at the same sampling time are fused to obtain the common trend baseline of current and the common trend baseline of temperature, which are then calculated according to formula (1):

[0047] In the formula, express Common trend baseline of current at time t, in units of ; express The baseline for the common temperature trend at any given time, in °C; Indicates the first A topological mirror loop in Current trend value at time t, in units of ; Indicates the first A topological mirror loop in Temperature trend value at any given time, in °C; This indicates the number of topological mirror loops participating in the calculation of the common trend baseline. This represents median calculation. Using median fusion instead of weighted average can reduce the impact of anomalies in individual topological mirror loops on the common trend baseline, while avoiding the introduction of weight parameters that lack clear physical basis.

[0048] When a topological mirror loop deviates from the median trend of other topological mirror loops for three consecutive sliding windows, and the deviation exceeds the 99th percentile of the absolute value of the corresponding historical normal deviation, the topological mirror loop is removed from the current common trend baseline calculation, and anomaly analysis is initiated separately for the loop.

[0049] S5. Calculate the local trend residuals and identify candidate regions for local anomalies. Subtract the common current trend baseline from the current monitoring trend of the target circuit to obtain the local current trend residual; subtract the common temperature trend baseline from the temperature monitoring trend of the target circuit to obtain the local temperature trend residual, and calculate it according to formula (2):

[0050] In the formula, Indicates the target loop is in Local trend residual of current at time t, in units of ; Indicates the target loop is in Local temperature trend residual at time point, in °C; Indicates the target loop is in Current monitoring trend at any given time, in units of ; Indicates the target loop is in Temperature monitoring trend at any time, in °C.

[0051] The local current trend residual reflects the independent current variation of the target circuit relative to structurally similar circuits, while the local temperature trend residual reflects the independent temperature variation of the target terminal relative to similar terminals. By subtracting the common trend baseline, the impact of load changes, operating mode changes, and ambient temperature changes on anomaly analysis can be reduced.

[0052] From historical operating status data segments whose operating status codes are identical to the current operating status code and have been confirmed to be normal through maintenance records and manual verification, the absolute values ​​of local trend residuals for current and temperature are statistically analyzed. The historical operating status data segments are selected from the most recent 90 days, with a minimum of 30 segments. The 99th percentile of the distribution of the absolute values ​​of the local trend residuals for current and temperature is determined as the initial threshold for current residuals. To prevent the statistical thresholds from falling below the sensor's detection capability, the current residual threshold must not be lower than three times the absolute value of the maximum measurement error of the current monitoring channel, and the temperature residual threshold must not be lower than three times the absolute value of the maximum measurement error of the temperature sensor. The final residual threshold is the larger of the statistically obtained 99th percentile value and the corresponding three times measurement error value.

[0053] In this embodiment, the current residual threshold is determined to be 18 mA and the temperature residual threshold is 1.5 °C based on historical data. When the local trend residual of the current continuously exceeds 18 mA for a duration of not less than 60 s, the corresponding current monitoring point is identified as a candidate monitoring point for current anomalies; when the local trend residual of the temperature continuously exceeds 1.5 °C for a duration of not less than 180 s, the corresponding temperature monitoring point is identified as a candidate monitoring point for temperature anomalies. The 60 s and 180 s are determined based on the duration of the instantaneous current interference and the terminal thermal response time, respectively. The duration of short-term current fluctuations and short-term temperature fluctuations under normal operating conditions is statistically analyzed, and the duration that can cover not less than 95% of normal short-term fluctuations is selected as the over-limit confirmation duration.

[0054] Starting from the candidate anomaly monitoring point, upstream and downstream associated monitoring points are obtained along the directed topology. The moment when the local trend residual of each associated monitoring point first crosses the corresponding residual threshold is recorded, and the propagation direction of the local trend residual is determined according to the order of the threshold crossing moments.

[0055] When there are no valid time limits for adjacent monitoring points, the propagation direction is determined according to the order in which the local trend residual begins to increase continuously. The residual amplitudes of adjacent monitoring points are compared along the propagation direction. If the residual amplitude of a subsequent monitoring point is not less than 90% of the residual amplitude of the previous monitoring point, the local trend residual is determined to have not effectively attenuated; if the residual amplitude of a subsequent monitoring point is greater than the residual amplitude of the previous monitoring point, the local trend residual is determined to have increased locally. 90% is determined based on the residual propagation ratio of adjacent monitoring points under normal operating conditions. The ratio of residual amplitudes of adjacent monitoring points under normal operating conditions is statistically analyzed, and the upper limit of the ratio that can cover no less than 95% of the normally attenuated samples is set as the non-attenuation judgment threshold.

[0056] Topological nodes where the local trend residual first increases or fails to decay effectively for the first time, along with their adjacent topological edges, are identified as candidate regions for local anomalies. These candidate regions correspond to terminal sections, neutral line connection sections, grounding line connection sections, N600 branch connection sections, or monitoring terminal access locations within terminal blocks.

[0057] S6. Determine the electro-thermal response time delay and determine the steady-state electro-thermal response relationship. From historical operating status data segments with the same code as the current operating status and confirmed to be without anomalies, the local trend residual change rates of current and temperature are statistically analyzed. The local trend residual change rate of current is expressed in mA / s, and the local trend residual change rate of temperature is expressed in ℃ / s. The 99th percentile of the absolute value distribution of the local trend residual change rate of current is determined as the threshold value of the current residual change rate, and the 99th percentile of the absolute value distribution of the local trend residual change rate of temperature is determined as the threshold value of the temperature residual change rate.

[0058] In this embodiment, the threshold for the rate of change of current residual is 0.020 mA / s, and the threshold for the rate of change of temperature residual is 0.0010 °C / s. These values ​​were obtained from data collected over 30 normal operating cycles and configured according to different circuit types.

[0059] Starting from the beginning of the current operating state data segment, the local current trend residual and its rate of change are detected sequentially. When the local current trend residual exceeds 18 mA, or the rate of change of the local current trend residual exceeds 0.020 mA / s, and maintains the same direction of change for 6 consecutive analysis times, the sampling time that first meets the conditions is determined as the effective starting point of the local current trend residual change. .

[0060] Since the unified analysis period is 10 s, six consecutive analysis times correspond to 60 s. Starting from the effective change starting point tI, the local temperature trend residual and its rate of change are detected sequentially. When the local temperature trend residual exceeds 1.5 ℃, or the rate of change of the local temperature trend residual exceeds 0.0010 ℃ / s, and the same direction of change is maintained for 18 consecutive analysis times, the sampling time that first meets the conditions is determined as the response starting point of the local temperature trend residual. Eighteen consecutive analysis times correspond to 180 seconds, used to exclude short-term fluctuations in temperature sensors and transient temperature changes caused by ventilation in the cabinet. The electro-thermal response time delay is determined based on the time difference between the temperature response start point and the effective current change start point, and is calculated according to formula (3):

[0061] In the formula, Indicates the electro-thermal response time delay, in units of ; This indicates the effective starting point of change in the local trend residual of the current, in units of... ; This represents the response start point of the local temperature trend residual, in units of... .

[0062] Obtain the electro-thermal response time delay of the target circuit for no less than 5 operating cycles, and eliminate operating cycles with inconsistent operating status codes, maintenance operations, or data missing ratios exceeding 10%.

[0063] Calculate the deviation ratio of the electro-thermal response time delay relative to the median time delay for each effective operating cycle. When each deviation ratio does not exceed 20%, and the local trend residuals of current and temperature change in the same direction within each operating cycle, a stable electro-thermal response relationship is determined to exist between them.

[0064] 20% was determined through historical current-induced thermal anomaly samples or on-site terminal loading tests. The electro-thermal response time delays of similar terminals within the same load range were statistically analyzed, and the deviation proportion that could cover no less than 95% of valid anomaly samples was set as the time delay stability threshold.

[0065] When there are fewer than 10 valid historical anomaly samples, a terminal contact resistance loading test is used to obtain time delay samples. In the loading test, four current levels are set according to 30%, 50%, 70%, and 90% of the rated current of the target circuit. The circuit is kept running for no less than 30 minutes at each current level, and the time difference between the start of the current change and the start of the temperature response is recorded.

[0066] S7. Constructing the electro-thermal time-delay evolution trajectory When a stable electrothermal response relationship exists between the local current trend residual and the local temperature trend residual, the electrothermal response time delay is shifted forward along the time axis by the local temperature trend residual. This aligns the response starting point of the local temperature trend residual with the effective change starting point of the local current trend residual, resulting in a time-delay compensated local temperature trend residual.

[0067] The local trend residual of the current at each sampling time is used as the abscissa, with the unit being mA; the local trend residual of the temperature after time delay compensation at the same sampling time is used as the ordinate, with the unit being ℃; the coordinate points of each trajectory are connected in the order of sampling time to form the electro-thermal time delay evolution trajectory. The trajectory segment where the local trend residual of the current continuously increases from the initial value to the local peak value is determined as the rising segment, and the trajectory segment where the local trend residual of the current continuously decreases from the local peak value is determined as the falling segment. Within the local trend residual interval of the current covered by the rising segment and the falling segment, the corresponding time delay compensated temperature local trend residual is compared according to the same level of local trend residual of the current, and the trajectory hysteresis degree is determined by formula (4):

[0068] In the formula, Indicates the degree of trajectory hysteresis, in degrees Celsius; This represents the level of local trend residuals of the current, in units of... ; This represents the local trend residual range of the current, which is jointly covered by the rising and falling segments. This indicates the residual level of the local trend of the current during the rising segment. The time-delay compensated temperature local trend residual, in °C; This indicates the residual level of the local trend of the current during the fallback segment. The time-delay compensated temperature local trend residual is given in °C.

[0069] The greater the hysteresis of the trajectory, the higher the terminal temperature remains after the local trend residual of the current falls back. There is a possibility of heat accumulation, reduced heat dissipation capacity, or continuous increase in contact resistance in the local area.

[0070] The median of the temperature residual difference between the rising and falling segments is used to characterize the trajectory hysteresis, which reduces the impact of fluctuations at individual trajectory points on the analysis results and eliminates the need for manual weighting. Electro-thermal time-delay evolution trajectories for continuous operating cycles are obtained, and the envelope range of the trajectory for each operating cycle is determined. The unit of measurement for the trajectory envelope area is mA·℃.

[0071] When the trajectory envelope area of ​​the subsequent operating cycle increases by no less than 20% relative to the previous operating cycle, and the increase occurs continuously for two operating cycles, it is determined that the electro-thermal time-delay evolution trajectory has cross-operating cycle expansion characteristics.

[0072] 20% is determined based on the change in trajectory envelope area when historical anomalies transition from a normal state to a clearly developing state. The area increase of adjacent operating cycles for similar anomaly samples is statistically analyzed, and the minimum area increase that can cover no less than 95% of the anomaly development samples is set as the expansion threshold. The cross-cycle expansion of the electro-thermal time-delay evolution trajectory is manifested by an increase in the peak value of the local current trend residual, an increase in the peak value of the local temperature trend residual, an increase in the degree of trajectory hysteresis, or an increase in the duration of the fallback segment.

[0073] S8. Determine the anomaly type, location, and stage of development. When the local current trend residual changes before the local temperature trend residual, and a stable electrothermal response relationship exists between the two, and the trajectory envelope of the continuous operating cycle expands sequentially, the anomaly type is identified as a current-induced heating asymptotic anomaly. A current-induced heating asymptotic anomaly indicates that local current changes cause terminal temperature rise, and the coupling relationship between current and temperature strengthens with increasing operating cycle.

[0074] When the local current trend residual continuously exceeds the current residual threshold but a stable electro-thermal response relationship is not formed, the anomaly type is determined based on the topological edge to which the local anomaly candidate region belongs. If the local anomaly candidate region is located in the neutral line connection segment, it is determined to be a neutral line current path anomaly; if it is located in the grounding line connection segment, it is determined to be a grounding line current path anomaly; if it is located in the N600 branch connection segment, it is determined to be an N600 current path anomaly.

[0075] When the local temperature trend residual continuously exceeds the temperature residual threshold and there is no prior change in the local current trend residual, the anomaly type is determined to be a local heat accumulation anomaly.

[0076] For localized heat accumulation anomalies, further compare the temperature changes of adjacent temperature sensors within the same cabinet. When adjacent temperature sensors all show synchronous temperature rises, treat this temperature rise as a common change in the cabinet's ambient temperature; when only the residual temperature trend of the target terminal continues to increase, retain the identification result of the localized heat accumulation anomaly.

[0077] The topological node whose local trend residual first crosses the corresponding residual threshold and whose residual amplitude first increases or fails to decay effectively along the propagation direction is identified as an anomaly. When the interval between the threshold crossing points of two adjacent topological nodes is less than a unified analysis period, i.e., less than 10 s, the two topological nodes and the topological edge between them are jointly identified as the anomaly location range to avoid misjudgment of anomaly locations due to sampling time resolution.

[0078] The abnormal development stage includes the abnormal initiation stage, the abnormal development stage, and the abnormal intensification stage.

[0079] When the local trend residuals intermittently exceed the corresponding residual threshold, a stable electro-thermal response relationship has not yet been formed, and the trajectory envelope does not continuously expand within the continuous operating cycle, it is determined to be the abnormal initiation stage.

[0080] When the local trend residual continuously exceeds the corresponding residual threshold, forming a stable electro-thermal response relationship, and the trajectory envelope area expands for two consecutive operating cycles, it is determined to be in the abnormal development stage. When the increase in the trajectory envelope area relative to the previous operating cycle is not less than 20% for two consecutive times, and the trajectory hysteresis degree increases by not less than 30% relative to the historical normal upper limit, it is determined to be in the abnormal aggravation stage.

[0081] The historical normal upper limit is determined by the 99th percentile of the trajectory hysteresis degree during normal operation cycles under the same operating conditions. 30% is determined based on abnormal samples before historical maintenance. When there are no fewer than 10 sets of valid abnormal samples, the increase in trajectory hysteresis degree before the abnormality enters the on-site maintenance state is statistically analyzed, and the minimum increase that can cover no less than 95% of the samples is set as the judgment threshold; when there are fewer than 10 sets of valid abnormal samples, the judgment threshold is determined by a terminal contact resistance loading test.

[0082] S9. Connect the secondary loop topology model and output the analysis results. Write the anomaly type, anomaly location, anomaly development stage, electro-thermal response time delay, and local anomaly candidate region into the attribute fields of the corresponding topology node or topology edge.

[0083] The system displays the target loop, topological mirror loop, common current trend baseline, common temperature trend baseline, local current trend residual, local temperature trend residual, and electro-thermal time delay evolution trajectory according to the associated data segments of the operating status. Anomaly trend analysis records include the target loop identifier, operating status code, start and end times of the operating status data segment, topological mirror loop identifier, mirror loop filtering level, start and end times of current residual exceeding limits, start and end times of temperature residual exceeding limits, electro-thermal response time delay, trajectory hysteresis degree, trajectory envelope area, anomaly type, anomaly location, and anomaly development stage.

[0084] During the initial stage of an anomaly, the online monitoring platform generates trend monitoring alerts; during the development stage, it generates on-site verification alerts; and during the escalation stage, it generates priority maintenance alerts and displays the upstream and downstream topology nodes corresponding to the anomaly location, providing a basis for locating the anomaly by checking terminal fastening status, detecting contact resistance, and inspecting connection lines.

[0085] Example 2: This embodiment uses the N600 branch in the secondary circuit of a substation voltage transformer as the target circuit to illustrate the specific analysis process of the method of the present invention.

[0086] The circuit breaker corresponding to the target circuit is in the closed position, the protection pressure plate is in the engaged position, the air switch is in the closed position, the substation is in the non-maintenance position, and the primary equipment load rate is 64%. Therefore, the load status corresponding to the target circuit is the medium load status.

[0087] Five first-level topology mirror circuits were obtained by screening based on operating status code, protection function, transformer winding type, grounding method, terminal connection level, and relative position of monitoring points. All five mirror circuits and the target circuit belong to the voltage transformer protection winding circuit, share a common N600 grounding method, and have monitoring points located at the intermediate transfer terminal layer.

[0088] Thirty operating cycles within the most recent 90 days, confirmed by maintenance records and manual verification to be free of abnormalities, were selected as historical normal samples. Based on the statistical analysis of these historical normal samples, the 99th percentile of the absolute value of the local trend residual was 18 mA, the 99th percentile of the absolute value of the local trend residual was 1.5 ℃, the 99th percentile of the absolute value of the rate of change of the local trend residual was 0.020 mA / s, and the 99th percentile of the absolute value of the rate of change of the local trend residual was 0.0010 ℃ / s.

[0089] During the analysis period, the N600 current of the five topology mirror circuits showed a synchronous upward trend with the increase of load, and the terminal temperature of the five topology mirror circuits changed synchronously with the ambient temperature of the cabinet.

[0090] According to formula (1), the median values ​​of the current trend and temperature trend of the five topological mirror loops are fused to generate the common current trend baseline and the common temperature trend baseline.

[0091] Calculate the local current trend residual and local temperature trend residual of the target circuit according to formula (2). Target circuit terminal X2 The local current trend residual at the 14 downstream monitoring points gradually increased from 8 mA to 31 mA, exceeding 18 mA for 720 consecutive seconds; the corresponding local temperature trend residual at the terminal gradually increased from 0.4 ℃ to 3.2 ℃, exceeding 1.5 ℃ for 940 consecutive seconds. Analysis was performed along the directed topology of the secondary loop, with terminal X2... The local current trend residual at the 14 upstream monitoring points consistently does not exceed 9mA, from terminal X2 Starting from node 14 in the corresponding topology, the local current trend residual does not continue to decay, and terminal X2 The residual amplitude at the downstream monitoring point 14 is higher than that at the upstream monitoring point. Therefore, terminal X2... 14 and its downstream connecting lines were identified as local anomaly candidate areas.

[0092] The effective change start point of current and the temperature response start point are obtained in six consecutive operating cycles with the same operating state. According to formula (3), the electro-thermal response time delays corresponding to the six operating cycles are 390 s, 410 s, 420 s, 430 s, 440 s and 450 s respectively.

[0093] The median of the six electro-thermal response delays is 425 s. The deviation of each electro-thermal response delay from the median does not exceed 20%, and the local trend residuals of current and temperature both show the same direction of change, increasing sequentially within each operating cycle. Therefore, a stable electro-thermal response relationship is determined to exist between the local trend residuals of current and temperature.

[0094] Based on the electro-thermal response time delay corresponding to each operating cycle, the local temperature trend residual is shifted forward along the time axis to align the temperature response start point with the effective current change start point, and the electro-thermal time delay evolution trajectory for 6 operating cycles is constructed. According to formula (4), the trajectory hysteresis degrees corresponding to the 6 operating cycles are calculated to be 0.62 ℃, 0.71 ℃, 0.86 ℃, 1.04 ℃, 1.28 ℃ and 1.53 ℃ respectively, showing a trend of increasing period by period. The trajectory envelope areas corresponding to the 4th, 5th and 6th operating cycles are 181 mA respectively. ℃, 223 mA ℃ and 274 mA ℃. The trajectory envelope area of ​​the 5th operating cycle increased by 23.2% compared to the 4th operating cycle, and the trajectory envelope area of ​​the 6th operating cycle increased by 22.9% compared to the 5th operating cycle, exceeding the 20% trajectory expansion threshold twice consecutively. The 99th percentile of the trajectory hysteresis degree of the historical normal operating cycle was 0.91 ℃, and the trajectory hysteresis degree of the 6th operating cycle was 1.53 ℃, an increase of 68.1% compared to the historical normal upper limit, exceeding the 30% anomaly aggravation judgment threshold. Since the local trend residual of current changes before the local trend residual of temperature, there is a stable electro-thermal response relationship between the two, and the electro-thermal time delay evolution trajectory expands for multiple operating cycles, the anomaly type is determined to be current-induced heating type asymptotic anomaly. Since the local trend residual from terminal X2 The increase begins at point 14 and no longer effectively attenuates; therefore, the terminal x2 is adjusted. 14 and its downstream connecting lines were identified as abnormal locations.

[0095] Since the trajectory envelope area increased by at least 20% twice consecutively, and the trajectory hysteresis increased by more than 30% relative to the historical normal upper limit, the abnormal development stage was identified as the abnormal aggravation stage. The online monitoring platform correlated the above analysis results with terminal X2. The topology node corresponding to 14 generates a priority maintenance prompt and outputs the target circuit identifier, operating status code, local anomaly candidate area, electro-thermal response time delay, trajectory hysteresis degree, trajectory envelope area, anomaly type, anomaly location, and anomaly development stage. On-site maintenance personnel then adjust terminal X2 according to the prompt. 14. An inspection was conducted, and the test results showed that the tightening torque of the terminal was lower than the specified value for terminals of the same specification, and the contact resistance was higher than the contact resistance of the adjacent normal terminals, thus verifying the abnormal trend analysis results of the present invention.

[0096] Example 3: This embodiment uses the N600 branch in the secondary circuit of a substation voltage transformer as the analysis object to illustrate the process of identifying and locating the anomaly in the N600 current path when the local current trend residual continuously increases but a stable electro-thermal response relationship has not yet been formed. The circuit breaker corresponding to the target circuit is in the closed position, the protection plate is in the engaged position, the air switch is in the closed position, the substation is in a non-maintenance state, and the primary equipment load rate is 47%, corresponding to a low load state. The original sampling period for current monitoring data is 1 second, and the original sampling period for terminal temperature data is 10 seconds. The current monitoring data is resampled according to a unified analysis period of 10 seconds. Based on the target circuit's operating status code, protection function, transformer winding type, grounding method, terminal connection level, and relative position of the monitoring point, six first-level topology mirror circuits are selected from the secondary circuit topology model.

[0097] All six mirror loops and the target loop belong to the voltage transformer protection winding loop, all use the N600 single-point grounding method, and the monitoring points are all set at the intermediate transition terminal layer. The number of topological edges from each monitoring point to the transformer winding, the protection device input terminal, and the N600 grounding point are all the same. Thirty-two operating cycles within the most recent 90 days, confirmed to be normal by operation records, maintenance records, and manual verification, were selected as historical normal samples. According to the aforementioned threshold determination rules, the current residual threshold was 14 mA, the temperature residual threshold was 1.3 ℃, the current residual change rate threshold was 0.016 mA / s, and the temperature residual change rate threshold was 0.0009 ℃ / s.

[0098] Specifically, the current residual threshold and temperature residual threshold are taken as the larger of the 99th percentile of the absolute value distribution of the corresponding historical local trend residuals and three times the absolute value of the sensor's maximum measurement error; the current residual change rate threshold and temperature residual change rate threshold are taken as the 99th percentile of the absolute value distribution of the corresponding historical residual change rate. Within the data segment of the operating state to be analyzed, the effective data duration of the target loop and the six topological mirror loops is 3.5 hours, and the data missing rate is less than 1%, which meets the conditions for generating a common trend baseline.

[0099] The N600 current of the six topological mirror loops all showed a slow increase and then a stable change process with the change of primary equipment load. The repetition rate of the same current change direction in each topological mirror loop was 83.3%, and the duration of the change accounted for 66.7% of the corresponding current sliding window duration. Therefore, this change was identified as the common current trend component. The terminal temperature of the six topological mirror loops changed synchronously with the ambient temperature of the cabinet. The repetition rate of the same temperature change direction was 100%, and the duration of the change accounted for 73.3% of the temperature sliding window duration. Therefore, this change was identified as the common temperature trend component. According to formula (1), the median values ​​of the current trend and temperature trend of the six topological mirror loops were fused to obtain the common current trend baseline and the common temperature trend baseline. According to formula (2), the common current trend baseline was subtracted from the N600 current monitoring trend of the target loop to obtain the local current trend residual; the common temperature trend baseline was subtracted from the temperature monitoring trend of the corresponding terminal of the target loop to obtain the local temperature trend residual. The analysis results show that the terminal X3 of the target loop The residual current trend at the upstream monitoring point 07 remained between 6 and 10 mA, not exceeding the 14 mA current residual threshold; Terminal X3 The local trend residual of the current at monitoring point 07 gradually increased from 9 mA to 26 mA; terminal X3 The local current trend residual at the downstream monitoring point 07 gradually increased from 11 mA to 29 mA. Terminal X3 The local trend residual of the current at monitoring point 07 exceeded 14 mA for 2860 s continuously, terminal X3 The local current trend residual at the downstream monitoring point 07 exceeded 14 mA for 2710 s, meeting the criteria for candidate monitoring points with current anomalies. The residual propagation relationship at each monitoring point was analyzed along the directed topology of the secondary loop. Terminal X3 No valid limit exceedance occurred at the upstream monitoring point 07, terminal X3 The monitoring point corresponding to 07 first exceeds the current residual threshold, terminal X3 The downstream monitoring point 07 crossed the current residual threshold 40 seconds later, thus determining the local current trend residual from terminal X3. 07 propagates downstream. Terminal X3 The peak value of the local current trend residual at monitoring point 07 is 26 mA, and the peak value of the local current trend residual at its upstream monitoring point is 10 mA. Terminal X3 The residual amplitude at point 07 is significantly larger than that at the upstream monitoring point. Terminal X3 The residual peak value at the downstream monitoring point 07 is 29 mA, which is not lower than terminal X3. The residual peak value at point 07 is 90%, indicating that the local trend of the current residual originates from terminal X3. The increase begins at point 07 and does not effectively attenuate along the propagation direction. Therefore, terminal X3... 07. Terminal X3 The connection line between grounding convergence point 07 and N600, and the corresponding N600 branch, are identified as a local anomaly candidate area. Within the same operating status data segment, terminal X3... The maximum value of the local temperature trend residual at position 07 was 0.8 ℃, which did not exceed the temperature residual threshold of 1.3 ℃; the maximum rate of change of the local temperature trend residual was 0.0006 ℃ / s, which did not exceed the rate of change threshold of 0.0009 ℃ / s. Therefore, no effective temperature response starting point corresponding to the local current trend residual was detected. Further verification was performed using five consecutive operating cycles with the same operating conditions. Within these five operating cycles, terminal X3... The peak values ​​of the local current trend residuals at monitoring points 07 were 19 mA, 21 mA, 24 mA, 26 mA, and 27 mA, all exceeding the current residual threshold of 14 mA; the peak values ​​of the corresponding local temperature trend residuals were 0.5 ℃, 0.7 ℃, 0.6 ℃, 0.8 ℃, and 0.7 ℃, all below the temperature residual threshold of 1.3 ℃. Since no effective temperature response start point was formed in multiple operating cycles, the electro-thermal response time delay with continuous comparability could not be obtained according to formula (3). Therefore, it was determined that there was no stable electro-thermal response relationship between the local current trend residuals and the local temperature trend residuals, and the hysteresis degree calculation of the electro-thermal time delay evolution trajectory was not performed. According to the topological location of the candidate local anomaly region, terminal X3 Line 07 and its downstream connections are located in the N600 branch, and the anomaly is mainly characterized by a continuous increase in the localized residual current, without a stable temperature rise response. Therefore, the anomaly type is determined to be an anomaly in the N600 current path. To rule out drift of the current monitoring terminal itself, terminal X3... 07 Upstream monitoring point, terminal X3 07 Corresponding monitoring points and terminals X3 07. A portable current detection device was used for synchronous retesting at the downstream monitoring point. The measurement error of the portable current detection device was no greater than ±0.5%, and the maximum deviation between the retested value and the online monitoring value was 0.9 mA, which was less than the absolute value of the maximum measurement error of the online current monitoring channel, thus ruling out any abnormality in the online monitoring channel.

[0100] In the abnormal development stage assessment, although the local current trend residual of the target circuit exceeded the current residual threshold for multiple consecutive operating cycles, a stable electro-thermal response relationship was not formed, and there was no continuously comparable electro-thermal time-delay evolution trajectory envelope. Therefore, according to the abnormal development stage assessment rules, this abnormality was determined to be in the abnormal initiation stage. The online monitoring platform detected the abnormality in the N600 current path and terminal X3. 07. Terminal X3 The connection lines between the grounding collection points 07 and N600, the abnormal initiation stage, and the corresponding local current trend residuals are written into the secondary circuit topology model, and on-site verification records are generated.

[0101] On-site maintenance personnel inspected the local anomaly candidate areas marked according to the topology model and found terminal X3. 07. The insulation layer of the downstream connection line has localized damage, with the damaged area intermittently contacting the grounding metal component of the cabinet, thus creating an unintended additional grounding path. After removing the damaged connection line and replacing it with an insulated conductor of the same specification, data was collected again for three operating cycles under the same operating conditions. Terminal X3 The peak values ​​of the local current trend residuals at monitoring points 07 decreased to 7 mA, 8 mA, and 7 mA, respectively, all below the 14 mA current residual threshold, verifying the identification and location results of the N600 current path anomaly in this embodiment. The above embodiments are merely preferred embodiments of the present invention. Those skilled in the art can make equivalent substitutions or adjustments to the monitoring point configuration, data window, and threshold determination rules without departing from the principles of the present invention, and all such substitutions or adjustments should be included within the protection scope of the present invention.

[0102] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for analyzing abnormal trends in secondary circuit monitoring data, characterized in that, The method includes: The substation secondary circuit model, continuous monitoring data, and operating status data are acquired. The continuous monitoring data includes neutral current, grounding current, N600 current, and terminal temperature. The operating status data includes circuit breaker status, pressure plate status, air switch status, maintenance status, and load status. Based on the time of change of the state combination of the operating status data, the continuous monitoring data is divided into operating status data segments. For the target circuit, according to the protection function, transformer winding type, grounding method, terminal connection level and monitoring point location, multiple topological mirror circuits that are in the same operating state as the target circuit are selected from the secondary circuit model. Time alignment is performed on the monitoring data of the target loop and each topological mirror loop within the same operating state data segment. The common current trend and common temperature trend that recur and change in the same direction in each topological mirror loop are extracted to generate the common current trend baseline and the common temperature trend baseline. Subtract the current common trend baseline from the current monitoring trend of the target circuit to obtain the local current trend residual. Subtract the temperature common trend baseline from the temperature monitoring trend of the target circuit to obtain the local temperature trend residual. Based on the distribution direction and amplitude attenuation relationship of the local trend residuals corresponding to each monitoring point along the secondary circuit topology, determine the local anomaly candidate region. The effective starting point of change of the local trend residual of the current and the response starting point of the local trend residual of the temperature are determined. The time difference between the two is used as the electro-thermal response time delay. The stable electro-thermal response relationship is judged based on the degree of dispersion of the time delay and the direction of residual change in each operating cycle. Using the local current trend residual as the first trajectory variable and the local temperature trend residual after compensation according to the electro-thermal response time delay as the second trajectory variable, an electro-thermal time delay evolution trajectory is constructed according to the sampling time sequence. Based on the rising segment, falling segment, hysteresis degree, and cross-operational cycle expansion characteristics of the electro-thermal time-delay evolution trajectory, and combined with the propagation relationship of local trend residuals within the local anomaly candidate region, the anomaly type, anomaly location, and anomaly development stage are determined.

2. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 1, characterized in that, The process of establishing the secondary loop model includes: The protection device, transformer winding, terminal block, monitoring terminal and temperature sensor are set as topology nodes, and the neutral line, grounding line, N600 branch and terminal connection line are set as topology edges. Configure protection function identifiers, transformer winding type identifiers, grounding method identifiers, terminal connection level identifiers, and monitoring point location identifiers for each topology node, and associate the continuous monitoring data with the corresponding topology node or topology edge; The connection direction, upstream and downstream relationships, and shared grounding relationship between topology nodes are determined based on the secondary wiring relationship, forming a directed topology structure used to characterize the propagation path of local trend residuals.

3. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 1, characterized in that, The process of dividing the running status data segment includes: The status of circuit breakers, pressure plates, air switches, and maintenance are discretely coded, and the load status is coded according to the load rate range. The codes are then combined into an operating status code. The moment when the running status code changes is determined as the status segment node, and the data between adjacent status segment nodes is divided into a running status data segment. The state transition periods are deleted from the beginning and end of each running state data segment, and the deleted data is used for topology mirror loop screening and common trend baseline generation.

4. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 3, characterized in that, The process of filtering the topological mirror loop includes: Among the secondary circuits with the same operating status code as the target circuit, they are selected in sequence according to the following conditions: same protection function, same transformer winding type, same grounding method, same terminal connection level, and same relative position of monitoring point. The secondary loops that meet all the screening criteria are identified as first-level topological mirror loops. When the number of first-level topology mirror circuits is less than 3, under the condition that the operating status code, protection function, transformer winding type and grounding method are the same, the terminal connection level consistency condition and the monitoring point relative position consistency condition are cancelled in turn, the newly added secondary circuits are determined as supplementary topology mirror circuits, and the screening level corresponding to each topology mirror circuit is recorded.

5. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 4, characterized in that, The process of generating the common trend baseline includes: The continuous monitoring data of the target loop and multiple topological mirror loops are resampled to a unified sampling time, and the start time of the corresponding running state data segment is used as the time alignment reference. Within a continuous sliding window, determine the direction of current change, the direction of temperature change, and the duration of the trend for each topological mirror loop. When the same direction of change is repeated in at least 60% of the topological mirror loops, and the duration of the trend is not less than 50% of the duration of the corresponding sliding window, the change is identified as a common trend component. The first-level topological mirror loop is preferred for generating a common trend baseline; When there are fewer than 3 mirror loops in the first-level topology, the supplementary mirror loops are added to the calculation of the common trend baseline, and the median of the common trend components at the same sampling time is fused to obtain the current common trend baseline and the temperature common trend baseline.

6. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 2, characterized in that, The process of determining the local anomaly candidate region includes: From the historical operating status data segments with the same operating status and confirmed to be without abnormalities, the absolute values ​​of the local trend residuals of current and temperature are statistically analyzed, and the 99th percentile values ​​of their respective statistical distributions are determined as the current residual threshold and temperature residual threshold. Monitoring points where the local trend residual of current or the local trend residual of temperature continuously exceeds the corresponding residual threshold are identified as abnormal candidate monitoring points. The upstream and downstream associated monitoring points of the anomaly candidate monitoring points are obtained along the directed topology, and the residual propagation direction is determined according to the time sequence of the local trend residuals of each associated monitoring point crossing the corresponding residual threshold. The residual amplitudes of adjacent monitoring points are compared along the residual propagation direction, and the topological nodes whose residual amplitudes increase for the first time or do not continue to decay, along with their adjacent topological edges, are identified as local anomaly candidate regions.

7. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 6, characterized in that, The process of determining the electro-thermal response time delay includes: Based on historical operating status data segments with the same operating status and confirmed to be without abnormalities, the thresholds for current residual change rate and temperature residual change rate are determined respectively. The first sampling moment in which the local trend residual of the current or its rate of change continuously exceeds the corresponding threshold and maintains the same direction of change is determined as the effective starting point of change. Starting from the effective change point, the first sampling moment in which the local temperature trend residual or its rate of change continuously exceeds the corresponding threshold and maintains the same direction of change is determined as the response starting point; Obtain the electro-thermal response time delay for no less than 5 operating cycles. When the deviation of each electro-thermal response time delay from its median does not exceed 20%, and the local trend residual of current and the local trend residual of temperature change in the same direction within each operating cycle, the stable electro-thermal response relationship is determined to exist.

8. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 7, characterized in that, The process of constructing the electro-thermal time-delay evolution trajectory includes: The local temperature trend residual is shifted forward along the time axis by the electro-thermal response time delay, so that the response start point is aligned with the effective change start point. Using the local current trend residual at each sampling time as the abscissa and the local temperature trend residual after translation at the same sampling time as the ordinate, the trajectory coordinate points are connected according to the sampling time sequence. The trajectory rising segment is determined by the process of the local trend residual of the current increasing from the initial value to the peak value, and the trajectory falling segment is determined by the process of the local trend residual of the current falling back from the peak value. Calculate the temperature local trend residual interval between the rising and falling segments within the same current local trend residual interval, and use the interval to characterize the degree of trajectory hysteresis.

9. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 8, characterized in that, The process of determining the anomaly type, anomaly location, and anomaly development stage includes: When the local trend residual of current changes before the local trend residual of temperature, there is a stable electro-thermal response relationship, and the trajectory envelope of the continuous operating cycle expands sequentially, the anomaly type is determined to be current-induced heating type progressive anomaly. When the local current trend residual continues to increase and a stable electro-thermal response relationship is not formed, the anomaly type is determined to be a current path anomaly based on the neutral line, ground line, or N600 branch to which the local anomaly candidate area belongs. When the local temperature trend residual continues to increase and there is no prior change in the local current trend residual, the anomaly type is determined to be a local heat accumulation anomaly. The topological node whose local trend residual crosses the corresponding residual threshold earliest and whose residual amplitude first increases along the propagation direction is identified as an anomaly location. Based on the number of trajectory envelope expansions, changes in trajectory hysteresis, and continuous exceeding of limits in local trend residuals during continuous operation cycles, the abnormal development stage is determined as the abnormal initiation stage, abnormal development stage, or abnormal aggravation stage.

10. The method for analyzing abnormal trends in secondary circuit monitoring data according to claim 9, characterized in that, The process of outputting the analysis results includes: Write the anomaly type, anomaly location, anomaly development stage, electro-thermal response time delay, and local anomaly candidate region into the attribute fields of the corresponding topology node or topology edge. The target loop, topological mirror loop, current common trend baseline, temperature common trend baseline, current local trend residual, temperature local trend residual, and electro-thermal time delay evolution trajectory are displayed according to the associated data segments of the operating status. Generate an anomaly trend analysis record that includes target loop identifier, operating status code, anomaly type, anomaly location, anomaly development stage, residual limit exceedance start and end times, and electro-thermal response time delay.

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