A method for evaluating the state of a metering device of an electric energy metering box

Abstract

This application provides a method for assessing the status of metering devices in an electricity metering box, including: extracting the metering device ledger and cover opening operation record inside the electricity meter box; identifying the installation positions of the meter terminal blocks and terminal covers; and labeling the circuit names of the phase wire terminals and neutral wire terminals; installing current and temperature acquisition units and sheath position acquisition units inside the meter box to acquire the load current and terminal infrared temperature rise, and simultaneously recording the sheath retraction position; filtering out the cover opening operation period from the cover opening operation record, and removing the cover opening operation period, retaining the stable power consumption period, and identifying the conductor sheath boundary within the stable power consumption period; extracting the sheath retraction trace from the inside edge of the terminal cover towards the crimping screw side based on the sheath retraction position recorded by the sheath position acquisition unit; and combining the conductor sheath boundary and sheath retraction trace to analyze the heat conduction path and convection channel after the exposed conductor is close to the terminal cover, forming a record of the heat dissipation cause of the lag in infrared measurement point temperature rise.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for assessing the status of an electricity metering box. Background Technology

[0002] The safe and stable operation of electricity metering boxes is a crucial link in ensuring reliable power supply from the power system, and the accurate assessment of the terminal contact status of the metering device is of paramount importance. The terminal connection points within the metering box bear the dual functions of power transmission and metering data acquisition; deterioration of any contact point can lead to metering errors or even equipment burnout. Conventional infrared thermography assessments primarily rely on the positive correlation between temperature values ​​and load current, assuming that increased current and poor contact will inevitably lead to a rise in the temperature at the measuring point.

[0003] In the prior art, an invention entitled "Energy Metering Box and Monitoring Method with Temperature Monitoring Function" (publication number CN119023099A) discloses a technology for monitoring abnormal temperatures in energy metering boxes. This technology comprehensively determines the temperature monitoring delay weight based on terminal temperature data, internal and external temperatures of the box, and real-time power of the radiator. However, this disclosed technology has the problem of not dynamically correcting the infrared surface temperature evaluation benchmark for situations where the exposed conductor is exposed due to wire sheath retraction, which enhances heat dissipation and masks internal terminal heating. When the contact resistance of the terminal crimping part increases due to oxidation corrosion or mechanical loosening, additional Joule heat is generated at that point. This heat is transferred outward through the conductor and insulation material, ultimately forming a temperature rise on the terminal shell surface that can be detected by infrared equipment. For example, in a metering box where the load current is continuously increasing, severe contact degradation has occurred inside a certain terminal. Normally, the temperature of its external infrared measuring point should rise significantly. If the power maintenance personnel set a temperature threshold, the exposed metal conductor acts like an additional heat sink, quickly dissipating the internal heat to the surrounding air.

[0004] This results in the infrared thermometer capturing a terminal surface temperature that not only fails to rise but also appears to be lagging or even low. More complexly, different conductor materials, wire cross-sectional areas, degrees of sheath retraction, and internal terminal structures all lead to significant differences in the degree of heat dissipation enhancement. This heat dissipation effect caused by sheath retraction directly masks the actual contact degradation and heat generation inside the terminal, rendering conventional judgments based on fixed temperature thresholds completely ineffective.

[0005] Therefore, given the complex contradiction between increased load current and decreased surface temperature, how to accurately quantify the heat dissipation interference caused by sheath retraction and dynamically adjust the temperature assessment criteria accordingly to reveal hidden terminal contact hazards has become a critical issue that urgently needs to be addressed in the condition assessment of power metering boxes. Summary of the Invention

[0006] This invention provides a method for assessing the status of an electricity metering box, the method comprising: Extract the meter device ledger and cover opening operation record from the electricity meter box, identify the installation position of the meter terminal block and terminal cover, and label the circuit name of the phase line terminal and neutral line terminal; A current and temperature acquisition unit and a sheath position acquisition unit are installed in the meter box to acquire the load current and terminal infrared temperature rise, and the sheath retraction position is recorded simultaneously. Screen out the opening operation period from the opening operation record, remove the opening operation period, retain the stable power consumption period, and identify the boundary of the conductor sheath within the stable power consumption period; Based on the sheath retraction position recorded by the sheath position acquisition unit, extract the sheath retraction trace from the inner edge of the terminal cover towards the crimping screw side; By combining the boundary of the conductor sheath and the sheath retraction marks, the heat conduction path and convection channel after the exposed conductor is close to the terminal cover are analyzed, and the heat dissipation cause of the lag in the temperature rise of the infrared measuring point is recorded. By comparing and analyzing the load current and terminal infrared temperature rise during stable power consumption periods, and combining the records of heat dissipation causes such as conductor sheath boundary, sheath retraction marks and infrared measurement point temperature rise lag, abnormal deviation of terminal temperature rise relative to load current is identified, and the deteriorated area of ​​crimped contact that is covered by heat dissipation is determined. Assess the operating status of phase and neutral terminals according to circuit name, and generate a list of potential terminal hazards including terminal installation location, sheath retraction location, heat dissipation and shielding status, and the deterioration area of ​​the crimped contact.

[0007] Furthermore, the extraction of the meter device ledger and cover opening operation record inside the electricity meter box, identification of the installation position of the meter terminal block and terminal cover, and labeling of the circuit names of the phase wire terminal and neutral wire terminal include: Retrieve the register of metering devices inside the meter box from the electricity meter box archive, and extract the terminal cover installation and removal positions and corresponding circuit numbers from the cover opening operation record to obtain the distribution relationship of the metering devices inside the meter box. Distinguish the phase wire terminals and neutral wire terminals according to the wire connection direction, and mark the corresponding circuit name at the installation position.

[0008] Furthermore, the step of installing current and temperature acquisition units and sheath position acquisition units within the meter box to acquire load current and terminal infrared temperature rise, and simultaneously recording the sheath retraction position, includes: The current and temperature acquisition unit consists of a through-core current transformer and an infrared temperature probe. The through-core current transformer is fitted onto the incoming conductor to acquire the load current. The infrared temperature probe faces the outer surface of the terminal cover and directly opposite the crimping screw to acquire the temperature of the outer surface of the terminal cover and subtracts the ambient reference temperature to obtain the infrared temperature rise of the terminal. The sheath position acquisition unit consists of a miniature camera and a scale attached to the conductor. It captures the scale readings of the sheath end relative to the root of the crimping screw along the conductor axis and records the sheath retraction position simultaneously.

[0009] Furthermore, the step of filtering out the cap-opening operation periods from the cap-opening operation records, removing cap-opening operation periods, retaining stable power consumption periods, and identifying the conductor sheath boundary within stable power consumption periods includes: The start and end timestamps of the opening operations are filtered by the operation type field and merged to form a set of opening operation time periods. Synchronous record entries falling into any of the opening operation time periods are removed, and records of stable power consumption periods are retained. The outer surface of the sheath and the reflective area of ​​the exposed conductor are separated according to the image grayscale difference and the boundary pixels are connected along the conductor axis to form the boundary of the conductor sheath.

[0010] Furthermore, the step of extracting the sheath retraction mark from the inside of the terminal cover towards the crimping screw side based on the sheath retraction position recorded by the sheath position acquisition unit includes: Using the reference position of the end of the sheath corresponding to the inner edge of the terminal cover in the sheath position acquisition unit as the zero point, and the position of the wire sheath boundary at each moment as the current position, a displacement sequence is obtained. The time period that monotonically increases along the root direction of the crimping screw is marked as the active segment of sheath retraction. The displacement values ​​in the active segment of sheath retraction are connected in series with the corresponding scale coordinate points according to the timestamp to form a displacement trajectory line as the sheath retraction trace.

[0011] Furthermore, by combining the conductor sheath boundary and sheath retraction marks, the heat conduction path and convection channel after the exposed conductor is close to the terminal cover are analyzed, forming a record of the heat dissipation cause of the lag in temperature rise at the infrared measuring point, including: The endpoints of the wire sheath boundary and the sheath retraction mark are superimposed along the wire axis to determine the wire segment from the root of the crimping screw to the end of the sheath as the exposed conductor segment. The exposed conductor segment is divided into wall-mounted exposed segment and suspended exposed segment according to the shortest distance between the exposed conductor segment and the inner wall of the terminal cover. The contact surface length of the wall-mounted exposed segment and the distance between the suspended exposed segment and the inner wall of the terminal cover are marked. A first type of heat conduction path, dominated by metal conduction, is established along the contact surface between the exposed section attached to the wall and the inner wall of the terminal cover. A second type of heat conduction path, dominated by natural convection, is established along the air gap between the suspended exposed section and the inner wall of the terminal cover. Delineate the convection channel range along the direction from the terminal cover vent to the surface of the suspended exposed section. For terminals adjacent to the convection channel of the suspended exposed section in the area corresponding to the infrared measuring point, mark that the temperature rise of the infrared measuring point lags behind the internal heating.

[0012] Furthermore, the comparative analysis of load current and terminal infrared temperature rise during stable power consumption periods, combined with records of heat dissipation causes such as conductor sheath boundaries, sheath retraction marks, and lag in infrared measurement point temperature rise, identifies abnormal deviations in terminal temperature rise relative to load current, and determines deteriorated areas of crimped contact that are obscured by heat dissipation, including: For terminals without temperature rise lag in the heat dissipation cause record, the terminal temperature rise reference curve is obtained by fitting the square of the load current value and the corresponding infrared temperature rise value of the terminal using the least squares method. The proportion of the length of the suspended exposed section to the total length of the exposed conductor section is used as the degree of heat dissipation shielding. The vertical axis of the terminal temperature rise reference curve is magnified and corrected according to the degree of heat dissipation shielding to obtain the corrected terminal temperature rise reference curve. For terminals with lagging temperature rise, extract the measured load current value and the measured infrared temperature rise value of the terminals during the stable power consumption period. When the measured infrared temperature rise value of the terminals is continuously lower than the expected temperature rise of the corrected terminal temperature rise reference curve under the same measured load current value and the measured load current value continues to increase, mark the crimping area of ​​the corresponding terminals as the crimping contact deterioration area that is shielded by heat dissipation.

[0013] Furthermore, the process of evaluating the operating status of the phase and neutral terminals by circuit name generates a list of potential terminal hazards, including terminal installation location, sheath retraction location, heat dissipation shielding status, and the area of ​​deteriorated crimped contact. The deteriorated areas of the crimped contact are categorized according to the circuit name. For each circuit, the phase wire terminal and neutral wire terminal are summarized according to the corresponding terminal installation position, sheath retraction position and heat dissipation shielding condition to obtain the sub-circuit evaluation results. The terminal installation position, sheath retraction position and heat dissipation shielding condition and the deteriorated area of ​​the crimped contact are compiled one by one by terminal item to obtain the terminal hidden danger list.

[0014] Furthermore, the through-core current transformer is fitted onto the incoming conductor to collect the load current, including: The through-core current transformer outputs the instantaneous value of the load current according to a preset sampling period, forming a load current sequence aligned with the infrared temperature rise of the terminal and the retraction position of the sheath according to a unified timestamp.

[0015] Furthermore, the division into wall-mounted exposed sections and suspended exposed sections based on the shortest distance between the exposed conductor section and the inner wall of the terminal cover, and the marking of the contact surface length of the wall-mounted exposed section and the distance between the suspended exposed section and the inner wall of the terminal cover, includes: An axial coordinate system is established along the exposed conductor segment. The exposed conductor segment is divided into continuous wall-mounted exposed segments and suspended exposed segments according to whether the shortest distance is greater than zero. The contact length between the wall-mounted exposed segment and the inner wall of the terminal cover is accumulated along the conductor axis as the contact surface length. The normal distance between the suspended exposed segment and the inner wall of the terminal cover is marked at the shortest distance.

[0016] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a method for assessing the condition of an electricity metering box. Addressing the problem of difficulty in accurately identifying terminal crimp contact degradation due to heat dissipation obscuring the data, this method deploys current and temperature acquisition units and sheath position acquisition units within the meter box to simultaneously acquire load current, terminal infrared temperature rise, and conductor sheath retraction position data. After excluding periods of open-cover operation, stable power consumption periods are retained for analysis. This invention identifies conductor sheath boundaries and sheath retraction marks, analyzes the heat conduction path and convection channel formed by exposed conductors close to the terminal cover, reveals the heat dissipation cause of delayed temperature rise at infrared measurement points, and accurately identifies the degraded crimp contact area obscured by heat dissipation by comparing the abnormal deviation between load current and terminal temperature rise. Finally, a terminal hazard list is generated according to circuit name, including terminal installation location, sheath retraction position, heat dissipation obscuration status, and degraded crimp contact area, achieving accurate identification and assessment of terminal crimp contact degradation. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for assessing the status of an electricity metering box according to the present invention.

[0018] Figure 2 This is a schematic diagram of a method for assessing the status of an electricity metering box according to the present invention.

[0019] Figure 3 This is another schematic diagram of a method for assessing the status of an electricity metering box according to the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1-3 The method for assessing the status of an electricity metering box in this embodiment may specifically include: S101. Extract the meter device ledger and cover opening operation record from the electricity meter box, identify the installation position of the meter terminal block and terminal cover, and label the circuit name of the phase line terminal and the neutral line terminal.

[0022] Retrieve the meter device register from the electricity meter box archive. Based on the register, extract the meter installation location and terminal block layout diagram. Combined with the cover opening operation record, extract the terminal cover installation and removal location and corresponding circuit number to obtain the distribution relationship of the meter devices within the meter box. Locate the installation position of the meter terminal block and terminal cover according to the distribution relationship. For the wiring terminals on the terminal block, distinguish between phase wire terminals and neutral wire terminals according to the wire connection direction. Based on the circuit number, mark the circuit name to which the phase wire terminal and neutral wire terminal belong at the installation position.

[0023] Specifically, an electricity meter box typically houses one or more single-phase or three-phase electricity meters, each with a terminal block and terminal cover underneath. The meter system ledger records the meter box number, meter model, transformer ratio, installation date, and corresponding power supply circuit number. After retrieving the ledger from the electricity meter box archive, the installation locations and terminal block layouts of all meters within the box are retrieved based on the meter box number. The terminal block layout diagram is obtained from the ledger according to the meter model and manufacturer specifications, indicating the terminal arrangement order and wiring rules. Different terminal block models may use different arrangement methods. In one implementation, under a three-phase four-wire system, the terminals from left to right correspond to phase A incoming line, phase A outgoing line, phase B incoming line, phase B outgoing line, phase C incoming line, phase C outgoing line, neutral incoming line, and neutral outgoing line. However, in actual applications, the layout diagram corresponding to the meter model should prevail. The metering automation system includes a seal management module. This module records the sealing status and opening operations of all terminal covers within the meter box. When maintenance personnel disassemble or assemble a terminal cover, the change in seal status triggers the system to automatically generate an opening operation record. This opening operation record is exported from the seal management module, and its fields include the start and end times of the opening, the operator, the operation type, and the corresponding terminal cover number. There is a one-to-one correspondence between the terminal cover number and the terminal block location in the meter device ledger; each terminal cover number is associated with a set of terminal block coordinate information. By querying the coordinate information corresponding to the terminal cover number in the ledger, and combining this with the terminal type and phase label at that coordinate location in the terminal block layout diagram, the disassembly / assembly position and the corresponding circuit number of the terminal cover can be extracted, thus obtaining the distribution relationship of the meter devices within the meter box. Furthermore, the installation positions of the meter terminal blocks and terminal covers are located based on this distribution relationship. For the terminals on the terminal block, phase terminals and neutral terminals are distinguished according to the direction of wire connection: the crimping point of the wire introduced from the power supply side is classified as the incoming terminal, and the crimping point of the wire led out from the load side is classified as the outgoing terminal; among them, the terminals connected to phases A, B, and C are marked as phase terminals, and the terminals connected to the N line are marked as neutral terminals.

[0024] For example, the circuit number is used to mark the installation location. For instance, the A-phase incoming terminal of lighting circuit L1 is marked as "L1-A-IN", and the neutral terminal of common power circuit L2 is marked as "L2-N". The marking results are archived in the form of a mapping between location coordinates and circuit names, providing a basic location reference for evaluating the terminal contact status within the meter box.

[0025] S102. Install current and temperature acquisition units and sheath position acquisition units in the meter box to acquire load current and terminal infrared temperature rise, and simultaneously record the sheath retraction position.

[0026] Based on the terminal installation locations and circuit names, current and temperature acquisition units are deployed on the incoming conductor sides corresponding to the phase and neutral terminals within the meter box. These units consist of a through-type current transformer and an infrared temperature probe. The through-type current transformer is fitted onto the incoming conductor to collect the load current. The infrared temperature probe, facing the area directly opposite the crimping screw on the outer surface of the terminal cover, collects the temperature of the terminal cover's outer surface. This temperature reflects the temperature of the terminal surface after the heat generated inside the terminal is transmitted through the terminal cover, thus obtaining the load current sequence and the terminal surface temperature sequence. A sheath position acquisition unit is installed next to the terminal crimping screw. This unit consists of a miniature camera and a scale attached to the conductor. For each conductor sheath connected to the terminal, the scale readings relative to the root of the crimping screw at the end of the sheath are photographed along the conductor's axis. Combined with timestamps, the continuous recording of the sheath end position is completed, obtaining the sheath retraction position sequence. For the terminal surface temperature sequence, the ambient reference temperature is read from the background temperature measurement point set in the non-terminal area inside the meter box. The terminal surface temperature sequence is subtracted from the ambient reference temperature to obtain the terminal infrared temperature rise sequence. The load current sequence, the terminal infrared temperature rise sequence and the sheath retraction position sequence are sampled with a unified timestamp and synchronously stored on the same time axis to obtain a synchronous record of the load current, terminal infrared temperature rise and sheath retraction position inside the meter box.

[0027] In one embodiment, the current and temperature acquisition unit is located on the front side of the terminal block inside the meter box. The through-core current transformer is a low-power open-type transformer, with its iron core ring fitted onto the incoming conductors of the phase and neutral terminals. The secondary side lead is connected to the current sampling channel of the acquisition board. When the load current flows through the conductor, a small current signal proportional to the primary current is induced on the secondary side of the transformer. This signal is converted into a voltage signal by the sampling resistor and recorded by the acquisition board at a fixed sampling period to form the load current sequence.

[0028] Specifically, the optical axis is aligned with the projection area of ​​the outer surface of the terminal cover directly above the crimping screw, and the light spot covers the outer surface of the terminal cover corresponding to the crimping screw. The infrared temperature probe outputs the terminal surface temperature reading at the same sampling period as the load current, and archives the data point by point according to the timestamp to form the terminal surface temperature sequence.

[0029] It is understandable that for a three-phase four-wire metering circuit, each phase terminal and neutral terminal corresponds to a set of through-core current transformers and infrared temperature probes, forming a data acquisition channel that is mapped one-to-one with the circuit name.

[0030] Preferably, the sampling period is 1 to 5 seconds to balance data granularity and storage overhead.

[0031] In one possible implementation, the sheath position acquisition unit consists of a miniature camera and a scale attached to the conductor. The scale is a heat-resistant insulating film, attached to the outer surface of the conductor sheath along the conductor axis, with the zero mark aligned with the root of the crimping screw. The scale lines are perpendicular to the conductor axis, and the minimum division is 1 millimeter. The optical axis of the miniature camera lens is perpendicular to the conductor axis, and the fixed focal length ensures clear imaging of the scale area. The miniature camera triggers shooting according to a preset sampling period of 1 to 5 seconds. The relative position of the edge of the sheath end and the scale line in each image represents the distance between the sheath end and the root of the crimping screw. The image processing flow is as follows: After grayscale conversion of the acquired image, binarization segmentation is performed using a grayscale value of 128 as the threshold. The grayscale value of the outer surface of the sheath is usually below 80, appearing dark, while the grayscale value of the exposed copper core is usually above 180, appearing bright. The boundary between the two is the end position of the sheath. The scale line features are extracted using an edge detection algorithm, and the pixel distance between the sheath end boundary and the nearest scale line is calculated. Combined with a pre-calibrated conversion coefficient between pixels and actual distances, the distance from the end of the sheath to the root of the crimping screw is calculated. The conversion coefficient is obtained by photographing a standard scale with known spacing, typically ranging from 0.05 mm per pixel to 0.1 mm per pixel. When the sheath retracts from the inner edge of the terminal cover towards the crimping screw side, this distance value increases accordingly; when the conductor sheath remains intact without retraction, this distance value remains near the initial installation value. The distance values ​​are archived one by one with the shooting timestamp to form the sequence of sheath retraction positions. Furthermore, while monitoring the sheath retraction, the terminal surface temperature is collected by an infrared temperature sensor at the same sampling period to form a terminal surface temperature sequence. For this terminal surface temperature sequence, background temperature measurement points are set in non-terminal areas within the meter box. These background temperature measurement points are selected on the inner surface of the meter box side wall or at an empty mounting plate location within the meter, with a distance of no less than 200 mm from the terminal blocks and transformers, and a distance of no less than 150 mm from the ventilation openings, avoiding direct influence from airflow disturbances and heat source radiation. An independent environmental temperature probe collects background temperature readings at the same sampling period, i.e., 1 to 5 seconds, as the environmental reference temperature. This environmental reference temperature is used to eliminate interference from environmental temperature fluctuations on terminal temperature monitoring. The outer surface temperature data of the terminal cover is collected by an infrared temperature probe to form a terminal surface temperature sequence Tterminal. This is collected by the aforementioned independent environmental temperature probe and serves as the environmental reference temperature Tambient. The temperature value at each moment in the terminal surface temperature sequence is subtracted from the corresponding environmental reference temperature, calculated using the formula ΔT = Tterminal - Tambient, to obtain the terminal infrared temperature rise sequence. This temperature rise sequence reflects the temperature rise of the terminal crimping area relative to the environment inside the meter box, and is used to assess the degree of localized heating caused by abnormal crimping contact resistance.

[0032] For example, the system collects three types of sequence data: the load current sequence from real-time measurements of the through-core current transformer, the terminal infrared temperature rise sequence from temperature detection data of the infrared temperature probe, and the sheath retraction position sequence from image measurement data from a miniature camera with a scale. The sampling pulses for all three sequences are triggered by the same crystal oscillator clock source, and the sampling period is uniformly set to 1 second. During data alignment, a time window is created by tracing back 5 sampling periods from the current sampling time. All data points for each sequence within the time window are extracted, and the average load current (I), average temperature rise (T), and average retraction displacement (D) are calculated respectively. The three values ​​of I, T, and D are combined with the current timestamp to form a four-element data record stored in the database. For example, at time 10 seconds, the system extracts the current measurement values ​​from the time window of 9.5 seconds to 10 seconds, calculates an average current of 52 amperes, an average temperature rise of 38 degrees Celsius, and an average retraction displacement of 1.2 millimeters, generating a record of 10 seconds, 52 amperes, 38 degrees Celsius, and 1.2 millimeters.

[0033] In one embodiment, the data acquisition module reads the circuit name from the power distribution circuit identification plate and the terminal number from the terminal sequence number. It then combines this information with the timestamp collected by the sensor, the load current value, the terminal infrared temperature rise value, and the distance to the sheath end to form an aligned record field. This multi-dimensional record is stored in a non-volatile flash memory chip within the meter box, forming a synchronous record of the load current, terminal infrared temperature rise, and sheath retraction position within the meter box. Heat dissipation masking refers to the phenomenon where, after the sheath retracts, the suspended section of the exposed conductor dissipates heat through the air gap inside the terminal cover to the ventilation opening, bypassing the terminal cover shell. This causes the temperature rise read by the infrared temperature probe from the outer surface of the terminal cover to be lower than the actual temperature rise inside the terminal. This phenomenon leads to an underestimation and distortion in the heat assessment based on the terminal surface temperature. The aforementioned synchronous record provides a time-consistent data basis for subsequent identification of the heat dissipation masking effect of sheath retraction on the terminal surface temperature rise.

[0034] S103. Select the opening operation period from the opening operation record, remove the opening operation period, retain the stable power consumption period, and identify the conductor sheath boundary within the stable power consumption period.

[0035] The start and end timestamps of the opening operations are filtered from the opening operation record by the operation type field. The start and end timestamps consist of the opening time and closing time of the terminal cover. A corresponding opening operation period is formed for each opening operation's start and end timestamp. All opening operation periods within the time range covered by the synchronous record are merged to obtain an opening operation period set. For the time axis of the synchronous record, entries falling within any opening operation period are removed from the synchronous record according to the opening operation period set. The remaining synchronous record entries are retained as stable power consumption period records. The stable power consumption period records correspond to the time period when the terminal cover is closed and the load current is continuously supplied. For the sheath image frames captured by the miniature camera in the stable power consumption period records, the outer surface of the sheath and the reflective area of ​​the exposed conductor are separated according to the image grayscale difference. The boundary pixels between the outer surface of the sheath and the exposed conductor are extracted along the conductor axis. The boundary pixels are connected to form the sheath end contour line as the conductor sheath boundary, thus obtaining the position record of the conductor sheath boundary along the direction of the crimping screw root within the stable power consumption period.

[0036] Specifically, the terminal cover opening operation records are archived in a structured field by the sealing management module of the metering automation system. Each record includes an operation type field, terminal cover opening time, terminal cover closing time, operator number, and meter box number. The operation type field can contain values ​​such as opening for inspection, replacing current transformers, secondary circuit wiring, and meter replacement. From the operation records, all records with non-empty values ​​and paired opening and closing timestamps are selected based on the operation type field, and the start and end timestamps are extracted as the filtering results. In one embodiment, for each filtering result, the terminal cover opening time is used as the start point of the operation period, and the terminal cover closing time is used as the end point, forming a closed interval as the corresponding operation period. If multiple terminal cover opening operation records exist for the same meter box within the synchronous recording coverage time range, they are arranged chronologically, and overlapping or adjacent operation periods are merged to obtain a set of operation periods.

[0037] It should be noted that the load current, terminal infrared temperature rise, and sheath retraction position data during the cover-opening operation period are all subject to external interference: after the terminal cover is opened, the convection conditions inside the box change abruptly, and the terminal surface temperature drops abnormally due to accelerated airflow; maintenance personnel touching the wires may cause temporary displacement of the sheath end position; the current loop may be briefly interrupted when replacing the current transformer. These interferences prevent the synchronous record entries during this period from reflecting the terminal contact characteristics under stable operating conditions. Furthermore, for the time axis of the synchronous records, the timestamps of the synchronous record entries are compared one by one according to each closed interval in the cover-opening operation period set. If the timestamp of a synchronous record entry falls into any cover-opening operation period, the entry is marked as an entry to be removed; if the timestamp of a synchronous record entry does not fall into any cover-opening operation period, the entry is retained as a record for stable power consumption periods.

[0038] Specifically, the stable power consumption period records the time period during which the corresponding terminal cover is in a closed state and the load current is continuously supplied. During this period, the convection conditions inside the meter box are stable and the terminal cover is well sealed. The collected load current sequence, terminal infrared temperature rise sequence, and sheath retraction position sequence all reflect the actual operating status of the terminal.

[0039] In one possible implementation, the identification of the conductor sheath boundary is based on image frames of the sheath captured by the miniature camera. The outer surface of the sheath is typically made of a black or gray insulating material, which presents a low grayscale value in the image; the exposed conductor is made of copper or aluminum, whose surface produces a high grayscale reflective area under illumination. Each pixel row of the sheath image frame is scanned along the conductor axis, and the grayscale jump amplitude between adjacent pixels is counted.

[0040] Understandably, the grayscale jump values ​​obtained from the scan are filtered according to a preset grayscale jump threshold. Pixels with grayscale jump values ​​exceeding the grayscale jump threshold are the boundary pixels between the outer surface of the sheath and the reflective area of ​​the exposed conductor. The grayscale jump threshold ranges from 30 to 60, with the specific value determined based on the ambient lighting conditions. The boundary pixels obtained from scanning along different pixel rows in a single frame image are sorted according to the conductor axial coordinates, and adjacent boundary pixels are connected to form a continuous broken line, which is the outline of the sheath's end.

[0041] For example, a scale is set in the image, with the zero mark aligned with the pixel column containing the root of the crimping screw, and the graduation value corresponding to an actual distance of 0.05 mm per pixel. Using the pixel column containing the root of the crimping screw as the reference coordinate origin, the average pixel coordinates of the sheath end contour line along the conductor axis are converted into actual distances according to the scale graduation value, serving as the position value of the conductor sheath boundary along the direction of the crimping screw root. This position value corresponds one-to-one with the timestamp of each synchronous record entry in the stable power consumption period record, forming a position record of the conductor sheath boundary within the stable power consumption period.

[0042] Preferably, median filtering is applied to the sheath end contour lines identified in multiple consecutive frames of images to eliminate abnormal jump points caused by instantaneous reflections or dust adhesion, ensuring that the sheath boundary position remains smooth over time. The median filtering window size is set to 5 to 9 consecutive frames, with a preferred window size of 7 frames when the sampling period is 1 second, corresponding to a time span of approximately 7 seconds. This effectively suppresses abrupt noise without introducing excessive hysteresis. This implementation covers the requirements for identifying conductor sheath boundaries in both single-phase and three-phase four-wire meter boxes. To address the difference in reflective properties between copper and aluminum core conductors, the system adaptively adjusts the grayscale jump threshold T based on the local grayscale variance σ before identification. When σ is greater than or equal to 25, it is identified as a highly reflective material, and the T value is increased by 20% to 30% to suppress metallic luster interference. When σ is less than or equal to 15, it is identified as a low-reflective material, and the T value is decreased by 15% to 25% to enhance boundary sensitivity. When σ is between 15 and 25, it is identified as a conventionally reflective material, and the T value is taken from the calibration baseline without adjustment.

[0043] S104. Extract the sheath retraction mark from the inner edge of the terminal cover toward the crimping screw side based on the sheath retraction position recorded by the sheath position acquisition unit.

[0044] Based on the position record of the conductor sheath boundary along the root direction of the crimping screw during the stable power consumption period, the reference position of the sheath end corresponding to the inner edge of the terminal cover is read from the initial installation file of the sheath position acquisition unit. The reference position is the alignment scale position of the sheath end and the inner edge of the terminal cover when the sheath position acquisition unit is deployed. Taking the reference position as the zero point and the position of the conductor sheath boundary at each moment as the current position, the displacement sequence of the sheath end relative to the inner edge of the terminal cover is obtained. For the displacement sequence, the displacement change of adjacent moments is determined in chronological order: if the displacement value of adjacent moments in the displacement sequence shows a monotonically increasing trend along the root direction of the crimping screw, then the period is marked as the active segment of sheath retraction; if the fluctuation amplitude of the displacement value is lower than the displacement threshold set according to the minimum division value of the scale, then the period is marked as the static segment of the sheath, thus obtaining the sheath displacement direction marking sequence. For the active segment of sheath retraction in the sheath displacement direction marking sequence, the displacement values ​​and corresponding scale coordinate points in the active segment are connected in sequence according to the timestamp. Along the conductor axis, starting from the inner edge of the terminal cover and pointing towards the root of the crimping screw, a displacement trajectory line at the end of the sheath is formed. The displacement trajectory line serves as the sheath retraction mark from the inner edge of the terminal cover to the side of the crimping screw.

[0045] Specifically, the establishment of the reference position at the end of the sheath relies on the installation file during the deployment phase of the sheath position acquisition unit. When deploying the miniature camera and scale, the end of the wire sheath is flush against the inner edge of the terminal cover, and the zero mark of the scale is aligned with the root of the crimping screw. The reading on the scale corresponding to the inner edge of the terminal cover is the reference position at the end of the sheath. This reference position, in millimeters, is stored in the initial installation file of the sheath position acquisition unit, corresponding one-to-one with the terminal number and circuit name.

[0046] It should be noted that during long-term operation of the meter box, the conductor sheath is affected by factors such as thermal expansion and contraction, mechanical vibration, and loosening of the crimping screws. The end of the sheath will gradually move from inside the terminal cover towards the root of the crimping screw. This movement is reflected in the position record as a change in the numerical value of the sheath end's position. In one embodiment, using the reference position as zero, the displacement value of the sheath end is obtained by subtracting the reference position from the current position of the conductor sheath boundary. A positive displacement value indicates that the sheath end has moved towards the root of the crimping screw; a larger displacement value indicates a more severe degree of retraction. The displacement value corresponding to each stable power consumption period record is calculated sequentially according to the timestamp, forming the displacement sequence. Considering that the sheath retraction is a gradual process caused by thermal expansion and contraction, mechanical vibration, and loosening of the crimping screws, the net displacement change of a sub-interval is calculated by taking the difference between the last displacement and the first displacement of the sub-interval in a fixed sub-interval, such as 10 minutes. If the net displacement change of several consecutive sub-intervals is positive along the root direction of the crimping screw and the cumulative change exceeds a preset displacement threshold, then this period is marked as an active sheath retraction segment. If the absolute value of the net displacement change of each sub-interval does not exceed the displacement threshold, then it is marked as a static sheath position segment.

[0047] It is understood that for time periods when the sheath end is in a steady state or only experiences slight vibration, the absolute value of the displacement difference between adjacent moments typically does not exceed the minimum division value of the scale. The displacement threshold is determined based on the position repeatability of the image measurement system and the calibration of the ambient vibration amplitude, taking three times the standard deviation of the sheath end position measurement under static calibration, generally 0.2 mm to 0.5 mm for common field conditions. The threshold is increased when significant field vibration causes a stationary segment to be misjudged as an active segment, and decreased when the environment is stable but active segments are insufficiently identified. This recommended value comprehensively considers the resolution of the measurement system and the typical amplitude of ambient vibration. If significant field vibration causes a stationary segment to be misjudged as an active segment, the threshold can be increased to 0.9 mm or 1 mm. If the environment is stable but stationary segments are insufficiently identified, the threshold can be decreased to 0.6 mm or 0.5 mm. When the displacement value fluctuation amplitude is lower than the displacement threshold, this time period is marked as a stationary segment of the sheath.

[0048] For example, for a 24-hour period of stable power consumption, the data is divided into 10-minute intervals. This time interval is determined based on the temperature rise response time of the cable sheath under load current, effectively capturing the sheath displacement fluctuation characteristics caused by temperature changes. The direction of displacement change within each sub-interval is determined. If six consecutive sub-intervals are determined to be positive changes, this 60-minute period is merged into a single active sheath retraction segment. This determination criterion is based on the thermal expansion coefficient of the sheath material and the temperature change pattern of the cable. A continuous 60-minute positive change eliminates measurement errors and short-term random disturbances, ensuring the identification of the actual retraction process caused by temperature changes. If an intermediate sub-interval is determined to be a negative change, the current active segment is interrupted at that sub-interval, and the active segment ends at the position preceding that sub-interval.

[0049] In one possible implementation, all stable power consumption periods are recorded and marked period by period according to the above determination method to obtain a sheath displacement direction marking sequence. The displacement direction marking sequence includes several active sheath retraction segments and sheath stationary segments interspersed therein. Each active segment is accompanied by a start and end timestamp, a start displacement value, and an end displacement value.

[0050] Preferably, for the active segment of sheath retraction in the sheath displacement direction marking sequence, the displacement value sequence within the active segment is extracted in time stamp order. Let S0 be the scale coordinate point corresponding to the reference position on the scale. For each moment of displacement value Δi within the active segment, its corresponding scale coordinate point Si is calculated using Si = S0 + Δi, thus establishing the correspondence between the displacement value and the scale coordinate point. Taking the scale coordinate point S0 corresponding to the reference position as the starting point of the trajectory line, and with the direction along the root of the crimping screw as the positive direction, the displacement value Δi at each moment of the active segment is mapped to a trajectory increment. These increments are then connected end-to-end to form a displacement trajectory line extending from the reference position along the conductor axis to the current sheath end position. This trajectory line visually reflects the positional change of the sheath end on the scale during the sheath retraction process.

[0051] For example, for the A-phase incoming terminal in a three-phase four-wire metering circuit, if the total length of the displacement trajectory line is more than half the distance from the root of the crimping screw to the inner edge of the terminal cover, it indicates that the sheath of the terminal has significantly retracted, and the exposed conductor length is considerable. This half-threshold is determined with reference to the limit requirements for the length of exposed conductor inside the terminal cavity in electrical installation and acceptance, and combined with statistical analysis of on-site fault samples, it is found that: when the ratio r = L / D of the total length of the displacement trajectory line L to the distance D from the inner edge of the terminal cover to the root of the crimping screw is greater than or equal to 0.5, the probability of poor contact or short circuit faults at this terminal reaches 78%, which is a high-risk state; when 0.3 is less than or equal to r and less than 0.5, the fault probability is 32%, which is a medium-risk state; when r is less than 0.3, the fault probability is less than 5%, which is a low-risk state. For the neutral terminal in a single-phase meter box, if the total length of the displacement trajectory line accounts for only a very small proportion of this distance, i.e., r is less than 0.1, it indicates that the sheath basically remains in place. The displacement trajectory line serves as the sheath retraction mark from the inside of the terminal cover towards the crimping screw side, and is archived together with the corresponding circuit name, terminal number, calculated ratio r, and risk level determination result.

[0052] S105. Combining the boundary of the conductor sheath and the sheath retraction marks, analyze the heat conduction path and convection channel after the exposed conductor is close to the terminal cover, and form a record of the heat dissipation cause of the lag in the temperature rise of the infrared measuring point.

[0053] Based on the boundary of the conductor sheath and the sheath retraction mark, the current position of the sheath boundary and the endpoint of the displacement trajectory line are superimposed along the conductor axis to determine the conductor segment from the root of the crimping screw to the end of the sheath as the exposed conductor segment; for the exposed conductor segment, it is divided into wall-mounted exposed segment and suspended exposed segment according to the shortest distance between the exposed conductor segment and the inner wall of the terminal cover. The contact surface length of the wall-mounted exposed segment is marked, and the distance between the suspended exposed segment and the inner wall of the terminal cover is marked to obtain the geometric distribution record of the exposed conductor. For the exposed section attached to the wall in the geometric distribution record of the exposed conductor, a first type of heat conduction path is established along the contact surface between the conductor surface and the inner wall of the terminal cover. The first type of heat conduction path uses the copper core conductor as the heat source end and the terminal cover shell as the heat dissipation end, with heat flow dominated by metal conduction. For the suspended exposed section, a second type of heat conduction path is established along the air gap between the conductor surface and the inner wall of the terminal cover. The second type of heat conduction path uses the copper core conductor surface as the heat source end and the air gap inside the terminal cover as the heat transfer medium, with heat flow dominated by natural convection. This results in a heat conduction path division record from the inside of the terminal to the outer shell of the terminal cover. For the suspended exposed section in the heat conduction path division record, the convection channel range is delineated along the direction from the terminal cover vent to the surface of the suspended exposed section. The positional relationship between the terminal surface area corresponding to the infrared measuring point and the wall-mounted exposed section and the suspended exposed section is compared. For the terminal adjacent to the convection channel of the suspended exposed section in the area corresponding to the infrared measuring point, the infrared measuring point temperature rise of the terminal is marked as lagging behind the internal heat generation, and the heat dissipation cause record of the lag in infrared measuring point temperature rise is obtained.

[0054] Specifically, when the boundary of the conductor sheath and the sheath retraction mark are superimposed on the conductor axis, they correspond to a conductor region extending from the root of the crimping screw to the end of the sheath on a scale. The conductor within this region is neither covered by the metal clamping portion of the crimping screw nor is it exposed to the insulation of the sheath, directly within the space inside the terminal cover. This region is named the exposed conductor segment, and its length is equal to the distance the displacement trajectory line in the sheath retraction mark extends along the direction of the crimping screw root.

[0055] It should be noted that the exposed conductor segments are not uniformly distributed within the terminal cover. When the sheath retraction is small, the exposed conductor segments are short, mainly concentrated near the root of the crimping screw, and are pressed tightly against the inner surface of the terminal cover by the inner wall of the terminal cover. When the sheath retraction is large, the exposed conductor segments are long, and the conductor segments far from the root of the crimping screw may detach from the inner wall of the terminal cover and be suspended in the internal cavity of the terminal cover due to the natural bending of the wire and gravity. In one embodiment, a fixed miniature camera deployed in S102 is used, with its optical axis perpendicular to the wire axis for lateral imaging. In the same image, the outer contour of the exposed conductor and the inner wall contour of the terminal cover are simultaneously identified. The shortest pixel distance between the two contours is calculated millimeter by millimeter along the wire axis, and then converted into the actual shortest distance d according to the calibrated conversion factor, where each pixel corresponds to 0.05 mm to 0.1 mm. In each frame of the image, the outer contour of the conductor and the inner wall contour of the terminal cover are identified by an edge detection algorithm, the shortest pixel distance between the two contours is calculated, and then multiplied by the conversion factor to obtain the actual shortest distance d. If d is less than or equal to 5% of the conductor's nominal diameter, typically 0.1 mm to 0.3 mm, the conductor at that millimeter position is classified as a wall-mounted exposed section; if d is greater than this threshold, the conductor at that millimeter position is classified as a suspended exposed section. Further, for the wall-mounted exposed section, the lengths of all adjacent contact positions are accumulated along its axial direction to obtain the contact surface length Lwall-mounted of the wall-mounted exposed section; for the suspended exposed section, the average distance dsuspended between the suspended exposed section and the inner wall of the terminal cover is obtained by averaging the shortest distances at each millimeter position. The contact surface length Lwall-mounted serves as the basis for calculating the heat conduction area from the conductor to the terminal cover, and the average distance dsuspended is used to correct the convective heat transfer coefficient of the suspended section. These two parameters together constitute a record of the geometric distribution of the exposed conductor, which is archived along with the corresponding circuit name, terminal number, and sampling timestamp.

[0056] In one possible implementation, a first type of heat conduction path is established for the exposed section attached to the wall. The first type of heat conduction path starts inside the copper core conductor at the root of the crimp screw. Heat is conducted along the wire axis through the metal of the copper core conductor to the exposed section attached to the wall, then crosses the air gap through the contact surface between the exposed section attached to the wall and the inner wall of the terminal cover, enters the plastic shell of the terminal cover, and is finally dissipated on the outer surface of the terminal cover in the form of surface convection and surface radiation.

[0057] It should be noted that copper has a thermal conductivity of 380 W / m / K, which is much greater than that of plastic (0.2 to 0.5 W / m / K). The first type of heat conduction path consists of three parts connected in series: the copper core conductor segment, the contact interface between the exposed section attached to the wall and the inner wall of the terminal cover, and the terminal cover shell itself. The thermal resistance Rc of the copper conductor segment is typically less than 0.01 K / W. The thermal resistance Ri of the contact interface is affected by contact pressure and surface roughness, with a typical value of 0.5 to 2 K / W. The thermal resistance Rs of the plastic shell of the terminal cover is 1 to 3 K / W. The total thermal resistance Rt = Rc + Ri + Rs, where Rc accounts for less than 1% and is negligible, but Ri accounts for 20% to 40% and cannot be ignored. The thermal resistance of the entire path is mainly determined by the contact interface and the terminal cover shell. Compared with other paths, the first type of heat conduction path still has the characteristics of a shorter path and lower thermal resistance. The heat generated inside the terminal can be quickly transferred to the outer surface of the terminal cover, and the terminal surface temperature collected by the infrared temperature probe responds quickly to the internal heat generation.

[0058] It is understood that a second type of heat conduction path is established for the suspended exposed section. This second type of heat conduction path begins on the surface of the copper core conductor in the suspended exposed section, and heat is transferred through the air gap between the copper core conductor surface and the inner wall of the terminal cover. Heat transfer in the air gap is primarily driven by natural convection: the reduced air density after heating creates an upward airflow that flows upward along the inner wall of the terminal cover, exchanging air with the air inside the casing via the terminal cover vents. The entire path uses the air gap as the heat transfer medium; the terminal cover outer shell is not the primary heat dissipation interface.

[0059] Specifically, the convective heat transfer resistance of the air jacket is much greater than the conductive heat transfer resistance of the metal-plastic interface. The typical convective heat transfer resistance of the air jacket is 0.05 to 0.1 K / W, while the typical conductive heat transfer resistance of the metal-plastic interface is 0.001 to 0.005 K / W. However, the heat transfer resistance when air directly convects and dissipates heat through the terminal cover vent is 0.01 to 0.02 K / W, lower than the total thermal resistance of 0.03 to 0.06 K / W when heat is conducted outwards through the plastic shell of the terminal cover and then convected. As a result, the second type of heat conduction path bypasses the terminal cover shell, and heat is directly dissipated into the ambient air inside the meter box via airflow. The internal heating of the terminal does not sufficiently heat the plastic shell of the terminal cover under this path, thus the terminal surface temperature collected by the infrared temperature probe is sluggish in responding to internal heating. The division results of the two types of heat conduction paths are recorded using path type, starting point, ending point, and dominant heat transfer mechanism as fields, forming a record of the heat conduction path division from the inside of the terminal to the terminal cover shell.

[0060] In one embodiment, for the suspended exposed section in the heat conduction path division record, the convection channel range is delineated along the direction from the geometric center of the terminal cover vent to the surface of the suspended exposed section. The convection channel range has the surface of the suspended exposed section as its lower boundary, the terminal cover vent as its upper boundary, and the inner wall of the terminal cover as its side boundary, covering the entire flow path of hot air rising from the surface of the suspended exposed section to the vent. The characteristic dimension Lc of the convection channel is calculated, which is equal to the ratio of the volume V of the convection channel range to its internal surface area S, i.e., Lc = V / S. Based on the characteristic dimension Lc of the convection channel and the difference ΔT between the surface temperature of the suspended exposed section and the ambient temperature, the convective heat transfer coefficient h is calculated using the natural convection criterion correlation formula, where the Grashof number Gr includes a cube term of Lc, and the Nusselt number Nu is determined by Gr and the Prandtl number Pr, finally obtaining h = Nu × λ / Lc, where λ is the thermal conductivity of air. The convective heat transfer coefficient h is used to evaluate the heat dissipation capacity of the suspended exposed section, and is combined with the length ratio η of the suspended exposed section for comprehensive thermal resistance correction.

[0061] For example, the terminal surface area corresponding to the infrared measuring point is compared with the location of the exposed section against the wall and the location of the suspended exposed section in the geometric distribution record of the exposed conductor using two-dimensional projection. The ratio η_heat dissipation of the length of the suspended exposed section L_suspended to the total length of the exposed section L_total is calculated, where η_heat dissipation = L_suspended / L_total. At the same time, the ratio β_channel of the cross-sectional area S_channel of the convection channel to the thermally conductive area S_shell of the terminal cover is extracted, where β_channel = S_channel / S_shell. The judgment thresholds for η_heat dissipation and β_channel are determined by taking the boundary quantiles of the sample distribution of the same type of terminal under two working conditions: one where convection heat dissipation in the suspended section is dominant and the other where it is not. For example, 0.4 and 0.6 are taken respectively. When η_heat dissipation is greater than or equal to 0.4 or β_channel is greater than or equal to 0.6, the terminal is judged to be a terminal with lag in temperature rise, indicating that convection heat dissipation in the suspended exposed section is dominant. At this time, the terminal surface temperature collected by the infrared measuring point mainly reflects part of the heat transferred from the exposed section attached to the wall through the terminal cover shell, while most of the heat lost by the suspended exposed section through the convection channel is not captured by the infrared temperature measuring probe. The determination result of the temperature rise lag terminal, together with fields such as the contact surface length of the exposed section attached to the wall, the spacing of the suspended exposed sections, the range of the convection channel, the position of the infrared measuring point, the η heat dissipation value, and the β channel value, forms a record of the heat dissipation cause of the temperature rise lag at the infrared measuring point.

[0062] Preferably, heat dissipation cause records are established for different types of terminal covers in single-phase meter boxes, three-phase three-wire meter boxes, and three-phase four-wire meter boxes in the manner described above. This applies to copper core wires and aluminum core wires, as well as incoming lines with different cross-sectional areas. The heat dissipation cause records are archived in the energy meter box status assessment database, corresponding one-to-one with the circuit names.

[0063] S106. Compare and analyze the load current and terminal infrared temperature rise during stable power consumption periods. Combine the records of heat dissipation causes such as conductor sheath boundary, sheath retraction marks, and infrared measurement point temperature rise lag to identify abnormal deviations in terminal temperature rise relative to load current and determine the deteriorated area of ​​crimped contact that is obscured by heat dissipation.

[0064] For the synchronous records during the stable power consumption period, multiple sets of load current values ​​and corresponding terminal infrared temperature rise values ​​are extracted from the load current sequence and terminal infrared temperature rise sequence according to time windows. For terminals that are not marked as temperature rise lag terminals in the heat dissipation cause records of temperature rise lag at the infrared measuring points, the correspondence between the squares of the multiple sets of load current values ​​and the corresponding terminal infrared temperature rise values ​​is fitted using the least squares method to obtain the terminal temperature rise reference curve. The terminal temperature rise reference curve reflects the terminal infrared temperature rise level that a terminal with intact sheath should exhibit under different load currents. For terminals marked as lag terminals in the heat dissipation cause record of the infrared measurement point temperature rise lag, the degree of heat dissipation shielding is determined according to the spacing of the suspended exposed section and the range of the convection channel in the heat dissipation cause record. The degree of heat dissipation shielding is characterized by the proportion of the length of the suspended exposed section to the total length of the exposed conductor section. The degree of heat dissipation shielding is used as the lifting ratio to amplify and correct the vertical axis of the terminal temperature rise reference curve to obtain the corrected terminal temperature rise reference curve. The corrected terminal temperature rise reference curve serves as the expected temperature rise reference for the lag terminal after removing the heat dissipation shielding. For the terminal with lagging temperature rise, the measured load current value and the measured infrared temperature rise value of the terminal during the stable power consumption period are extracted from the synchronous record. The measured infrared temperature rise value of the terminal is compared with the expected temperature rise of the corrected terminal temperature rise reference curve under the same measured load current value. If the measured infrared temperature rise value of the terminal is continuously lower than the expected temperature rise and the measured load current value shows a continuous increasing trend, then the crimping area of ​​the terminal is marked as a crimping contact deterioration area that is blocked by heat dissipation.

[0065] Specifically, the heating at the terminal crimping point originates from the Joule heating effect. When the load current flows through the crimping contact surface, the contact resistance and the load current together generate heat power, which is proportional to the product of the square of the load current and the contact resistance. For terminals in good crimping condition, the contact resistance is at a stable low value, and there is a stable correlation between the terminal's infrared temperature rise and the square of the load current. For terminals in deteriorated crimping condition, the contact resistance increases significantly, the heat generated inside the terminal increases under the same load current, and the terminal's infrared temperature rise increases accordingly.

[0066] It should be noted that terminals with intact sheaths do not have the problem of exposed conductors obstructing heat dissipation. The heat generated inside the terminal is transmitted through the plastic shell of the terminal cover and is completely captured by the infrared temperature probe. Terminals not marked as lag terminals in the heat dissipation cause record of the lag in temperature rise at the infrared measurement point are terminals with intact sheaths. In one embodiment, the synchronous record during the stable power consumption period is divided into several sub-intervals according to a preset time window. Within each time window, the load current value I and the corresponding terminal infrared temperature rise value ΔT are extracted, where I represents the average load current within the time window, and ΔT represents the average terminal infrared temperature rise value after subtracting the ambient reference temperature from the terminal surface temperature within the time window.

[0067] Specifically, for multiple sample pairs of terminals with intact sheaths, the correspondence between ΔT and I² is fitted using the least squares method. The correspondence is in the form of ΔT = k × I², where k represents the terminal temperature rise coefficient, reflecting the magnitude of the infrared temperature rise of the terminal under the square of a unit load current. The fitted relationship is archived according to the terminal number and circuit name to form the terminal temperature rise reference curve.

[0068] Understandably, the value of the terminal temperature rise coefficient k is related to the terminal specifications, the initial value of the crimp contact resistance, and the material of the terminal cover. k = ΔT / I², with units of ℃ / A², characterizing the temperature rise generated per square unit current. For terminals of the same model and specifications, the k value is obtained through experimental calibration, and the typical value range is relatively concentrated. For example, the typical range of k value for a certain type of terminal is 0.08 to 0.12 ℃ / A². When the measured k value is less than 0.05 ℃ / A² or greater than 0.15 ℃ / A², it is considered a significant deviation, indicating that the crimp contact resistance or heat dissipation conditions of the terminal are abnormal. This terminal should be marked as a suspected defective terminal and reviewed. Furthermore, for the terminals marked as lag terminals in the heat dissipation cause record of the lag in infrared measurement point temperature rise, the length L1 of the suspended exposed section and the total length L2 of the exposed conductor section corresponding to the terminal are read from the heat dissipation cause record. The degree of heat dissipation shading η = L1 / L2 is calculated, where η ranges from 0 to 1. The closer η is to 1, the higher the proportion of the suspended exposed section in the exposed conductor section, the more heat is carried away by the convection channel, and the more severe the shading of the terminal's infrared temperature rise. When η is greater than 0.7, it is judged as severe shading, and the reliability of the infrared temperature rise data of the terminal is reduced. The terminal status needs to be comprehensively judged in conjunction with the deviation of the k value.

[0069] In one possible implementation, the correction for heat dissipation masking applies uniformly to the measured temperature rise side rather than the baseline curve: ΔT mc =ΔT m / (1 η) The measured temperature rise of the hysteresis terminal is restored to the true temperature rise level after removing the influence of heat dissipation and shielding. The reference curve itself is not enlarged or reduced, and is still taken from the I²-temperature rise fitting result of the intact sheath terminal.

[0070] For example, if the length of the suspended exposed section of a terminal with a lag in temperature rise accounts for 60% of the total length of the exposed conductor section, then the heat dissipation shielding degree η is taken as 0.6; if the measured infrared temperature rise of the terminal under a certain load current is 3 degrees Celsius, then the measured temperature rise is corrected to 3 / (1 The measured temperature rise of the terminal with intact sheath (0.6) is 7.5 degrees Celsius, while the reference temperature rise of the terminal with intact sheath under the same load current is 3 degrees Celsius. The difference of 4.5 degrees Celsius indicates that the internal heat generation of this terminal is significantly higher than that of the terminal with intact sheath, indicating that there is crimping degradation due to heat dissipation obstruction. The correction is based on the physical fact that the more severe the sheath retraction, the stronger the suspended heat dissipation, and the lower the measured temperature rise by infrared capture. Therefore, the measured temperature rise is restored according to the degree of heat dissipation obstruction before being compared with the reference. Furthermore, for each terminal with a lagging temperature rise, the measured load current value I of that terminal during the stable power consumption period is extracted from the synchronous record in the order of the time window. m Compared with the measured infrared temperature rise value ΔT of the terminal m , where I m With ΔT m These represent the average measured load current and the average terminal infrared temperature rise within the time window, respectively. Let I... m As input, the corresponding reference terminal infrared temperature rise ΔT is found on the terminal temperature rise reference curve. b The measured temperature rise will be calculated according to ΔT. m The corrected measured temperature rise ΔT is obtained by reducing / (1-η). mc , will ΔT mc With ΔT b Time window comparison. When the measured temperature is 3 degrees Celsius and η is 0.6, the measured temperature rise is corrected to 3 / (1-0.6) equals 7.5 degrees Celsius. If the reference temperature rise is 3 degrees Celsius, the terminal is judged to be abnormally heated.

[0071] Specifically, the temperature rise deviation is defined as δ = ΔT mc ΔT b , where ΔT mc To correct for the measured temperature rise, ΔT b The reference temperature rise is used under the same load current. If, under the premise that the load current is in a stable range comparable to the reference curve, the temperature rise deviation δ continuously exceeds the preset deviation judgment threshold, then the temperature rise lagging terminal is judged to have an abnormal deviation. The deviation judgment threshold is set according to the typical temperature rise fluctuation range of the terminal specification, and is set to 0.8 degrees Celsius. The time window length is set to 5 minutes, and the continuous judgment requires that the above conditions be met for 3 consecutive time windows, that is, if the temperature rise deviation continuously exceeds 0.8 degrees Celsius and the load current shows a slow increasing trend within a 15-minute observation period, it is judged as abnormal.

[0072] It is understandable that for terminals with abnormally high temperature rise lag, the crimping area of ​​the terminal is marked as a deteriorated crimping contact area due to heat dissipation shielding. The deteriorated crimping contact area is archived with the following fields: terminal number, circuit name, crimping screw position, temperature rise deviation, corresponding measured load current value, and corresponding heat dissipation shielding degree η.

[0073] Preferably, the phase and neutral terminals in single-phase meter boxes, three-phase three-wire meter boxes, and three-phase four-wire meter boxes are independently determined in the manner described above. Separate temperature rise reference curves are established for copper core conductor inlet terminals and aluminum core conductor inlet terminals to avoid the influence of temperature rise coefficient differences between different conductor materials on the determination results. The identification results of the deteriorated crimped contact areas obscured by heat dissipation are summarized according to the meter box number, serving as the core basis for subsequent terminal hazard assessment.

[0074] S107. Assess the operating status of phase and neutral terminals by circuit name, and generate a list of potential terminal hazards including terminal installation location, sheath retraction location, heat dissipation and shielding conditions, and areas of deteriorated crimping contact.

[0075] The deteriorated crimping contact areas obscured by heat dissipation are categorized according to circuit name. For the phase and neutral terminals under each circuit, the terminal installation position, sheath retraction position, and degree of heat dissipation obstruction are summarized to obtain the terminal operating status assessment results for each circuit. Based on the terminal operating status assessment results for each circuit, for terminals with deteriorated crimping contact areas obscured by heat dissipation, the terminal installation position, sheath retraction position, degree of heat dissipation obstruction, and deteriorated crimping contact area are compiled item by item to obtain the terminal hazard list for the phase and neutral terminals under that circuit.

[0076] Specifically, the previously identified areas of deteriorated crimped contact due to heat dissipation are grouped and categorized according to circuit name. Phase and neutral terminals within the same meter box can belong to different circuits, such as lighting circuits, power circuits, and metering utility circuits. The phase terminals under each circuit are further subdivided into phases A, B, and C, with neutral terminals grouped separately. For each subgroup, the corresponding terminal installation position, sheath retraction position value, and heat dissipation shielding degree value are retrieved from previous records and arranged in order of terminal number to form the terminal operating status evaluation results for the sub-circuit. In one embodiment, the terminal operating status evaluation results are stored in a table format in the energy metering box status evaluation database. The table fields include circuit name, phase identifier, terminal number, terminal installation position coordinates, sheath retraction position value, heat dissipation shielding degree value, and an identifier indicating whether there is a deteriorated crimped contact area due to heat dissipation shielding. Furthermore, terminals with deteriorated crimped contact areas due to heat dissipation shielding are compiled item by item. Each hazard entry records the terminal installation location, the sheath retraction location, the degree of heat dissipation shielding, and the marking information of the deteriorated area of ​​the crimped contact, including the location of the crimping screw, the temperature rise deviation, and the corresponding measured load current value. All hazard entries are grouped by circuit name to obtain a terminal hazard list for the phase and neutral terminals of the circuit.

[0077] For example, the list of potential terminal hazards in single-phase meter boxes and three-phase four-wire meter boxes is archived uniformly according to the meter box number, serving as the output basis for assessing the terminal contact status of the power meter box, and the power operation and maintenance side arranges targeted terminal tightening and conductor sheath repair work accordingly.

[0078] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for assessing the condition of an electricity metering box, characterized in that, The method includes: Extract the meter device ledger and cover opening operation record from the electricity meter box, identify the installation position of the meter terminal block and terminal cover, and label the circuit name of the phase line terminal and neutral line terminal; A current and temperature acquisition unit and a sheath position acquisition unit are installed in the meter box to acquire the load current and terminal infrared temperature rise, and the sheath retraction position is recorded simultaneously. Screen out the opening operation period from the opening operation record, remove the opening operation period, retain the stable power consumption period, and identify the boundary of the conductor sheath within the stable power consumption period; Based on the sheath retraction position recorded by the sheath position acquisition unit, extract the sheath retraction trace from the inner edge of the terminal cover towards the crimping screw side; By combining the boundary of the conductor sheath and the sheath retraction marks, the heat conduction path and convection channel after the exposed conductor is close to the terminal cover are analyzed, and the heat dissipation cause of the lag in the temperature rise of the infrared measuring point is recorded. By comparing and analyzing the load current and terminal infrared temperature rise during stable power consumption periods, and combining the records of heat dissipation causes such as conductor sheath boundary, sheath retraction marks and infrared measurement point temperature rise lag, abnormal deviation of terminal temperature rise relative to load current is identified, and the deteriorated area of ​​crimped contact that is covered by heat dissipation is determined. Assess the operating status of phase and neutral terminals according to circuit name, and generate a list of potential terminal hazards including terminal installation location, sheath retraction location, heat dissipation and shielding status, and the deterioration area of ​​the crimped contact.

2. The method for assessing the condition of an electricity metering box according to claim 1, characterized in that, The process of extracting the meter device ledger and cover opening operation record from the electricity meter box, identifying the installation position of the meter terminal block and terminal cover, and labeling the circuit names of the phase wire terminal and neutral wire terminal includes: Retrieve the register of metering devices inside the meter box from the electricity meter box archive, and extract the terminal cover installation and removal positions and corresponding circuit numbers from the cover opening operation record to obtain the distribution relationship of the metering devices inside the meter box. Distinguish the phase wire terminals and neutral wire terminals according to the wire connection direction, and mark the corresponding circuit name at the installation position.

3. The method for assessing the condition of an electricity metering box according to claim 1, characterized in that, The method of installing current and temperature acquisition units and sheath position acquisition units inside the meter box to acquire load current and terminal infrared temperature rise, and simultaneously recording the sheath retraction position includes: The current and temperature acquisition unit consists of a through-core current transformer and an infrared temperature probe. The through-core current transformer is fitted onto the incoming conductor to acquire the load current. The infrared temperature probe faces the outer surface of the terminal cover and directly opposite the crimping screw to acquire the temperature of the outer surface of the terminal cover and subtracts the ambient reference temperature to obtain the infrared temperature rise of the terminal. The sheath position acquisition unit consists of a miniature camera and a scale attached to the conductor. It captures the scale readings of the sheath end relative to the root of the crimping screw along the conductor axis and records the sheath retraction position simultaneously.

4. The method for assessing the condition of an electricity metering box according to claim 1, characterized in that, The process of filtering out opening operation periods from the opening operation records, removing opening operation periods, retaining stable power consumption periods, and identifying conductor sheath boundaries within stable power consumption periods includes: The start and end timestamps of the opening operations are filtered by the operation type field and merged to form a set of opening operation time periods. Synchronous record entries falling into any of the opening operation time periods are removed, and records of stable power consumption periods are retained. The outer surface of the sheath and the reflective area of ​​the exposed conductor are separated according to the image grayscale difference and the boundary pixels are connected along the conductor axis to form the boundary of the conductor sheath.

5. The method for assessing the status of an electricity metering box according to claim 1, characterized in that, The step of extracting the sheath retraction mark from the inside of the terminal cover towards the crimping screw side based on the sheath retraction position recorded by the sheath position acquisition unit includes: Using the reference position of the end of the sheath corresponding to the inner edge of the terminal cover in the sheath position acquisition unit as the zero point, and the position of the wire sheath boundary at each moment as the current position, a displacement sequence is obtained. The time period that monotonically increases along the root direction of the crimping screw is marked as the active segment of sheath retraction. The displacement values ​​in the active segment of sheath retraction are connected in series with the corresponding scale coordinate points according to the timestamp to form a displacement trajectory line as the sheath retraction trace.

6. The method for assessing the status of an electricity metering box according to claim 1, characterized in that, The analysis, combining the conductor sheath boundary and sheath retraction marks, examines the heat conduction path and convection channel of the exposed conductor near the terminal cover, forming a record of the heat dissipation causes of the lag in temperature rise at the infrared measurement point, including: The endpoints of the wire sheath boundary and the sheath retraction mark are superimposed along the wire axis to determine the wire segment from the root of the crimping screw to the end of the sheath as the exposed conductor segment. The exposed conductor segment is divided into wall-mounted exposed segment and suspended exposed segment according to the shortest distance between the exposed conductor segment and the inner wall of the terminal cover. The contact surface length of the wall-mounted exposed segment and the distance between the suspended exposed segment and the inner wall of the terminal cover are marked. A first type of heat conduction path, dominated by metal conduction, is established along the contact surface between the exposed section attached to the wall and the inner wall of the terminal cover. A second type of heat conduction path, dominated by natural convection, is established along the air gap between the suspended exposed section and the inner wall of the terminal cover. Delineate the convection channel range along the direction from the terminal cover vent to the surface of the suspended exposed section. For terminals adjacent to the convection channel of the suspended exposed section in the area corresponding to the infrared measuring point, mark that the temperature rise of the infrared measuring point lags behind the internal heating.

7. The method for assessing the condition of an electricity metering box according to claim 1, characterized in that, The method involves comparing and analyzing the load current and terminal infrared temperature rise during stable power consumption periods. Combined with records of heat dissipation causes such as conductor sheath boundaries, sheath retraction marks, and lag in infrared measurement point temperature rise, it identifies abnormal deviations in terminal temperature rise relative to load current and determines deteriorated areas of crimped contact that are obscured by heat dissipation, including: For terminals without temperature rise lag in the heat dissipation cause record, the terminal temperature rise reference curve is obtained by fitting the square of the load current value and the corresponding infrared temperature rise value of the terminal using the least squares method. The proportion of the length of the suspended exposed section to the total length of the exposed conductor section is used as the degree of heat dissipation shielding. The vertical axis of the terminal temperature rise reference curve is magnified and corrected according to the degree of heat dissipation shielding to obtain the corrected terminal temperature rise reference curve. For terminals with lagging temperature rise, extract the measured load current value and the measured infrared temperature rise value of the terminals during the stable power consumption period. When the measured infrared temperature rise value of the terminals is continuously lower than the expected temperature rise of the corrected terminal temperature rise reference curve under the same measured load current value and the measured load current value continues to increase, mark the crimping area of ​​the corresponding terminals as the crimping contact deterioration area that is shielded by heat dissipation.

8. The method for assessing the condition of an electricity metering box according to claim 1, characterized in that, The process of assessing the operating status of phase and neutral terminals by circuit name generates a list of potential terminal hazards, including terminal installation location, sheath retraction location, heat dissipation shielding status, and areas of deteriorated crimped contact. The deteriorated areas of the crimped contact are categorized according to the circuit name. For each circuit, the phase wire terminal and neutral wire terminal are summarized according to the corresponding terminal installation position, sheath retraction position and heat dissipation shielding condition to obtain the sub-circuit evaluation results. The terminal installation position, sheath retraction position and heat dissipation shielding condition and the deteriorated area of ​​the crimped contact are compiled one by one by terminal item to obtain the terminal hidden danger list.

9. The method for assessing the status of an electricity metering box according to claim 3, characterized in that, The through-core current transformer is fitted onto the incoming conductor to collect the load current, including: The through-core current transformer outputs the instantaneous value of the load current according to a preset sampling period, forming a load current sequence aligned with the infrared temperature rise of the terminal and the retraction position of the sheath according to a unified timestamp.

10. The method for assessing the condition of an electricity metering box according to claim 6, characterized in that, The exposed conductor section is divided into wall-mounted exposed sections and suspended exposed sections based on the shortest distance between the exposed conductor section and the inner wall of the terminal cover. The contact surface length of the wall-mounted exposed section and the distance between the suspended exposed section and the inner wall of the terminal cover are marked, including: An axial coordinate system is established along the exposed conductor segment. The exposed conductor segment is divided into continuous wall-mounted exposed segments and suspended exposed segments according to whether the shortest distance is greater than zero. The contact length between the wall-mounted exposed segment and the inner wall of the terminal cover is accumulated along the conductor axis as the contact surface length. The normal distance between the suspended exposed segment and the inner wall of the terminal cover is marked at the shortest distance.

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