Intelligent evaluation system for running state of cable branch box based on multi-sensor fusion

Abstract

The present application belongs to the technical field of power equipment state monitoring, and discloses a cable branch box operation state intelligent evaluation system based on multi-sensor fusion, which comprises a state acquisition module for acquiring partial discharge signals, voltage fluctuation signals, terminal temperature signals and terminal contact resistance signals of the cable branch box during operation, and through time synchronization and physical quantity normalization processing, a multi-source operation state parameter set of the cable branch box is constructed; a mutual coupling analysis module based on the multi-source operation state parameter set, which performs transient correlation deduction on the partial discharge signals and corresponding voltage fluctuation signals to obtain a partial discharge-voltage coupling quantity; when the partial discharge-voltage coupling quantity exceeds a preset partial discharge-voltage coupling quantity threshold, it is determined that there is a partial discharge abnormality caused by insulation deterioration in the cable branch box; and comprehensive and accurate evaluation of the operation state of the cable branch box is realized, thereby providing reliable support for safe operation and maintenance of the equipment.

Description

Technical Field

[0001] This invention relates to the field of power equipment condition monitoring technology, and more specifically, to an intelligent assessment system for the operating status of cable branch boxes based on multi-sensor fusion. Background Technology

[0002] The existing intelligent assessment system for the operating status of cable distribution boxes has the following main problems:

[0003] As a crucial connection and distribution device in power systems, the operating status of cable distribution boxes directly affects the safety and reliability of the power supply system. With the continuous increase in power load, problems such as internal insulation aging and poor terminal contact in cable distribution boxes are becoming increasingly prominent, making accurate assessment of their operating status of great significance.

[0004] Existing methods for monitoring and evaluating the operational status of cable branch boxes mainly rely on partial discharge detection, terminal temperature rise monitoring, and contact resistance measurement. However, the assessment of the impact of partial discharge on voltage transients is insufficient: traditional partial discharge diagnostic methods rely on amplitude statistics, pulse counting, PRPD spectra, etc., which can only observe the strength, repetition rate, and phase distribution of partial discharge, but cannot quantify the actual impact of partial discharge events on voltage transient disturbances.

[0005] Existing monitoring technologies typically analyze partial discharge signals within a single frequency band or wideband window, neglecting variations in partial discharge energy across different frequency components. Furthermore, they fail to reflect the time-delay response of voltage disturbances across different frequency bands, making it difficult to identify potential partial discharge energy-voltage-sensitive coupling risk points within the frequency band. Most systems use averages or fixed thresholds as references, making them susceptible to interference from noise, load fluctuations, etc., leading to misjudgments of partial discharge events or difficulty in detecting effective disturbances under weak partial discharge conditions. The effect of partial discharge on voltage exhibits a phase delay, while existing technologies typically only perform synchronous comparisons, failing to consider the inherent response lag between partial discharge energy release and voltage transients, as well as the lag characteristics of different frequency components.

[0006] Insufficient accuracy in terminal contact status assessment: Existing methods typically only monitor changes in terminal temperature rise or contact resistance. However, terminal temperature rise is affected by factors such as load current fluctuations and ambient temperature. Using temperature rise alone can easily misjudge normal load temperature rise as abnormal. Assessment based solely on changes in contact resistance may fail to detect early contact anomalies in a timely manner, especially when the change in contact resistance is small or at a low rate, making the anomaly easy to overlook. In actual physical phenomena, poor terminal contact can cause local temperature rise, and there is a non-linear coupling relationship between temperature rise and contact resistance. Existing technologies typically do not establish a mathematical correlation between terminal temperature rise and contact resistance, resulting in limited assessment accuracy. Relying heavily on empirical thresholds or qualitative judgments, and lacking a continuous quantitative scoring mechanism, anomaly detection is prone to false alarms or missed alarms.

[0007] In view of this, the present invention proposes an intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion to solve the above problems. Summary of the Invention

[0008] To overcome the aforementioned shortcomings of the prior art and to achieve the above objectives, the present invention provides the following technical solution: an intelligent assessment system for the operating status of cable branch boxes based on multi-sensor fusion, comprising:

[0009] The status acquisition module is used to collect partial discharge signals, voltage fluctuation signals, terminal temperature signals and terminal contact resistance signals of the cable branch box during operation. Through time synchronization and physical quantity normalization processing, a multi-source operating status parameter set of the cable branch box is constructed.

[0010] The mutual coupling analysis module, based on a multi-source operating state parameter set, performs transient correlation deduction between partial discharge signals and corresponding voltage fluctuation signals to obtain the partial discharge-voltage coupling amount; when the partial discharge-voltage coupling amount exceeds the preset partial discharge-voltage coupling amount threshold, it is determined that there is a partial discharge abnormality caused by insulation degradation in the cable branch box.

[0011] The contact assessment module evaluates the trend of terminal contact status changes based on terminal temperature and terminal contact resistance signals; it constructs a temperature rise resistance coupling function based on the trend of terminal contact status changes to generate a terminal contact anomaly index; when the terminal contact anomaly index exceeds a preset terminal contact anomaly index threshold, it determines that the terminal has a contact anomaly.

[0012] The assessment and decision-making module performs hierarchical mapping and cross-validation of partial discharge-voltage coupling quantity and terminal contact anomaly index, constructs a dual assessment system covering insulation status and mechanical connection status, and generates a comprehensive assessment result and corresponding status assessment report of the cable branch box operation status.

[0013] Preferably, the method for acquiring the partial discharge signal, voltage fluctuation signal, terminal temperature signal, and terminal contact resistance signal includes:

[0014] High-frequency current sensors are installed at each outgoing and incoming terminal of the cable branch box. The high-frequency current sensors are used to capture the pulse current signal generated by partial discharge. The pulse current signal is processed by bandpass filtering and background noise suppression, and the amplitude, frequency and waveform characteristics of the pulse current signal are continuously recorded to obtain the partial discharge signal of the cable branch box during operation.

[0015] Voltage monitoring units are connected to the busbar and each branch circuit of the cable branch box to monitor the instantaneous changes in the voltage of each phase in real time; the peak value, amplitude and frequency of voltage fluctuations are continuously recorded, and the occurrence time of voltage drop and surge events is marked, thereby obtaining voltage fluctuation signals.

[0016] Temperature sensors are arranged on and around the surface of each connection terminal in the cable branch box to continuously record the terminal temperature value, temperature rise rate and temperature rise amplitude, thereby obtaining the terminal temperature signal;

[0017] By applying a test current across the terminals, the voltage drop at the terminal connection is measured, and the terminal contact resistance value is calculated according to Ohm's law. The changing trend and abrupt change characteristics of the contact resistance value are continuously recorded to obtain the terminal contact resistance signal.

[0018] Preferably, the method for obtaining the multi-source operating state parameter set includes:

[0019] The collected partial discharge signal, voltage fluctuation signal, terminal temperature signal, and terminal contact resistance signal are time-marked according to a unified clock reference. Signals with inconsistent acquisition periods are synchronized and aligned using linear interpolation or sliding window averaging methods, so that various signals form corresponding data points at the same time node.

[0020] Signals of different dimensions are normalized so that their amplitudes can be directly compared and fused on a unified numerical scale. Various signals that have undergone time synchronization and normalization are combined into multi-dimensional parameter vectors at each time node, and the multi-dimensional parameter vectors at different time nodes are integrated to form a complete set of multi-source operating state parameters.

[0021] Preferably, the method for obtaining the partial discharge-voltage coupling amount includes:

[0022] Bandpass filtering is applied to the partial discharge signal from the multi-source operating state parameter set, and low-pass filtering is applied to the corresponding voltage fluctuation signal. A partial discharge-voltage disturbance analysis function is constructed, and transient correlation deduction is performed on the filtered partial discharge signal and voltage fluctuation signal to obtain the partial discharge-voltage coupling quantity.

[0023] Preferably, the method for determining the presence of partial discharge abnormalities caused by insulation deterioration within the cable branch box includes:

[0024] A preset partial discharge-voltage coupling threshold is set, and the partial discharge-voltage coupling amount is compared with the preset partial discharge-voltage coupling threshold in real time. When the partial discharge-voltage coupling amount is greater than the preset partial discharge-voltage coupling threshold, it is determined that there is a partial discharge abnormality caused by insulation deterioration in the insulation medium inside the cable branch box.

[0025] Preferably, the method for evaluating the trend of terminal contact state changes includes:

[0026] The temporal changes of the terminal temperature signal and the terminal contact resistance signal are analyzed, and the terminal temperature features and terminal contact resistance features are extracted respectively. The terminal temperature features include instantaneous temperature value, temperature rise rate, temperature rise amplitude, and temperature steady-state offset. The terminal contact resistance features include instantaneous contact resistance value, contact resistance change rate, contact resistance abrupt change features, and resistance steady-state offset.

[0027] The system sets a preset temperature rise threshold and a resistance change rate threshold. It combines the terminal temperature characteristics with the contact resistance characteristics to analyze the trend of terminal contact state changes. When the temperature rise rate is greater than the preset temperature rise threshold and the contact resistance change rate is greater than the preset resistance change rate threshold, it is determined that the terminal contact state is in a deterioration trend.

[0028] When the temperature rise rate is greater than the preset temperature rise threshold and the contact resistance change rate is less than or equal to the preset resistance change rate threshold, the terminal contact state is determined to be in a potential degradation trend.

[0029] When the temperature rise rate is less than or equal to the preset temperature rise threshold and the contact resistance change rate is greater than the preset resistance change rate threshold, the terminal contact state is determined to be in a state of resistance degradation.

[0030] When the temperature rise rate is less than or equal to the preset temperature rise rate threshold and the contact resistance change rate is less than or equal to the preset resistance change rate threshold, the terminal contact state is determined to be in a stable state.

[0031] Preferably, the method for generating the terminal contact anomaly index includes:

[0032] Based on the trend of terminal contact state changes, a temperature rise resistance coupling function is constructed for each terminal at each time point to quantify terminal contact abnormalities and calculate the terminal contact abnormality index.

[0033] Preferably, the method for determining that there is a contact abnormality at the terminal includes:

[0034] The terminal contact abnormality index is compared with a preset terminal contact abnormality index threshold to determine whether there is a contact abnormality in the terminal.

[0035] When the terminal contact abnormality index is less than or equal to the preset terminal contact abnormality index threshold, it is determined that there is no contact abnormality in the terminal;

[0036] When the terminal contact abnormality index is greater than the preset terminal contact abnormality index threshold, it is determined that there is a contact abnormality in the terminal.

[0037] Preferably, the method for constructing a dual evaluation system covering both insulation condition and mechanical connection condition includes:

[0038] Based on partial discharge-voltage coupling and terminal contact anomaly index, a hierarchical system for insulation risk level range and mechanical connection risk level range is constructed. The real-time acquired partial discharge-voltage coupling is mapped to the corresponding insulation risk level, and the real-time calculated terminal contact anomaly index is mapped to the corresponding mechanical connection risk level.

[0039] According to the preset insulation-connection cross-verification matrix, the mapped insulation risk level and mechanical connection risk level are cross-compared to make the final risk output, forming a dual assessment system covering insulation status and mechanical connection status.

[0040] Preferably, the method for generating a comprehensive evaluation result of the cable branch box's operating status and a corresponding status evaluation report includes:

[0041] The final risk output is used as a comprehensive assessment result of the cable branch box's operating status, and based on the comprehensive assessment result, a status assessment report containing the anomaly type, degree of deterioration, and maintenance recommendations is automatically generated.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention constructs a transient correlation deduction mechanism between partial discharge (PD) and voltage fluctuations based on a multi-source operating state parameter set, realizing a quantitative expression of the nonlinear coupling between PD events and voltage disturbances. It can characterize the actual impact of PD energy on voltage transients from multiple frequency band dimensions, and on this basis, form a physically meaningful and calculable coupling index, thereby improving the ability to identify weak and latent PD. The obtained coupling quantity between PD and voltage disturbances can be directly integrated into the intelligent operating state assessment system, improving the effectiveness and reliability of multi-sensor fusion assessment, and making the judgment of the operating state of cable branch boxes more comprehensive, detailed, and accurate.

[0044] By leveraging the nonlinear coupling relationship between temperature rise and contact resistance, and combining it with terminal normalization via the square of the current, a continuously quantified contact anomaly index is generated, which can accurately characterize the degree of terminal degradation and anomaly risk. Even in the early stages of terminal contact anomalies, when the temperature rise or contact resistance changes are small, the coupling index can still reflect potential anomalies, thus enabling early identification and warning. It effectively eliminates the interference of normal load current and ambient temperature on terminal temperature rise, making the anomaly index more reliably reflect contact degradation. The terminal contact anomaly index calculated at continuous time points can be used to dynamically monitor terminal status change trends, enabling early warning and maintenance decision support. By comprehensively considering the nonlinear relationship between the three key physical quantities—temperature rise, resistance, and current—it more realistically reflects the physical mechanism of terminal contact degradation, with higher accuracy than single-index methods, reducing false alarms and missed alarms. Attached Figure Description

[0045] Figure 1 A schematic diagram of the intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the intelligent evaluation method for the operating status of cable branch boxes based on multi-sensor fusion provided by the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0048] Example 1

[0049] Please see Figure 1 As shown, this embodiment provides an intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion, specifically including the following steps:

[0050] The status acquisition module is used to collect partial discharge signals, voltage fluctuation signals, terminal temperature signals and terminal contact resistance signals of the cable branch box during operation. Through time synchronization and physical quantity normalization processing, a multi-source operating status parameter set of the cable branch box is constructed.

[0051] The mutual coupling analysis module, based on a multi-source operating state parameter set, performs transient correlation deduction between partial discharge signals and corresponding voltage fluctuation signals to obtain the partial discharge-voltage coupling amount; when the partial discharge-voltage coupling amount exceeds the preset partial discharge-voltage coupling amount threshold, it is determined that there is a partial discharge abnormality caused by insulation degradation in the cable branch box.

[0052] The contact assessment module evaluates the trend of terminal contact status changes based on terminal temperature and terminal contact resistance signals; it constructs a temperature rise resistance coupling function based on the trend of terminal contact status changes to generate a terminal contact anomaly index; when the terminal contact anomaly index exceeds a preset terminal contact anomaly index threshold, it determines that the terminal has a contact anomaly.

[0053] The assessment and decision-making module performs hierarchical mapping and cross-validation of partial discharge-voltage coupling quantity and terminal contact anomaly index, constructs a dual assessment system covering insulation status and mechanical connection status, and generates a comprehensive assessment result and corresponding status assessment report of the cable branch box operation status.

[0054] Methods for acquiring partial discharge signals, voltage fluctuation signals, terminal temperature signals, and terminal contact resistance signals include:

[0055] High-frequency current sensors are installed at each outgoing and incoming terminal of the cable branch box. The high-frequency current sensors are used to capture the pulse current signal generated by partial discharge. The sampling frequency of the high-frequency current sensor is preset to be no less than 1MHz. The pulse current signal is processed by bandpass filtering and background noise suppression, and the amplitude, frequency and waveform characteristics of the pulse current signal are continuously recorded to obtain the partial discharge signal of the cable branch box during operation.

[0056] Voltage monitoring units are connected to the busbar and each branch circuit of the cable branch box to monitor the instantaneous changes in the voltage of each phase in real time. The sampling frequency of the voltage monitoring unit is preset to be no less than 10kHz, continuously recording the peak value, amplitude and frequency of voltage fluctuations, and marking the occurrence time of voltage drop and surge events, thereby obtaining voltage fluctuation signals.

[0057] Temperature sensors, including infrared temperature sensors and contact temperature sensors, are arranged on and around the surface of each connection terminal in the cable branch box. The infrared temperature sensors are used to monitor the temperature distribution on the terminal surface, and the contact temperature sensors are used to monitor the temperature rise of the terminal core. The preset acquisition cycle of the temperature sensors is 1 to 5 minutes, and the terminal temperature value, temperature rise rate and temperature rise amplitude are continuously recorded to obtain the terminal temperature signal.

[0058] By applying a test current across the terminals, the voltage drop at the terminal connection is measured, and the terminal contact resistance value is calculated according to Ohm's law. It should be noted that the test current is a small-amplitude DC test current not exceeding 0.5% of the rated operating current, so as to avoid affecting the normal operation of the cable branch box. The measurement cycle of the preset terminal contact resistance value is synchronized with the acquisition cycle of the temperature sensor, continuously recording the changing trend and abrupt change characteristics of the contact resistance value, thereby obtaining the terminal contact resistance signal.

[0059] Methods for obtaining multi-source operating status parameter sets include:

[0060] The acquired partial discharge signal, voltage fluctuation signal, terminal temperature signal, and terminal contact resistance signal are time-marked according to a unified clock reference, which can be provided by a network time protocol; and the signals with inconsistent acquisition periods are synchronized and aligned by linear interpolation or sliding window averaging methods, so that various signals form corresponding data points at the same time node;

[0061] Signals of different dimensions are normalized to enable direct comparison and fusion of amplitudes on a unified numerical scale. The normalization process includes converting the amplitude of partial discharge signals, voltage fluctuation amplitudes, terminal temperature values, and terminal contact resistance values ​​into percentage representations of preset reference values. Various signals that have undergone time synchronization and normalization are combined into multi-dimensional parameter vectors at each time node, and the multi-dimensional parameter vectors at different time nodes are integrated to form a complete set of multi-source operating status parameters.

[0062] Methods for obtaining partial discharge-voltage coupling include:

[0063] Bandpass filtering is applied to the partial discharge signal from the multi-source operating state parameter set, and low-pass filtering is applied to the corresponding voltage fluctuation signal. A partial discharge-voltage disturbance analysis function is constructed, and transient correlation deduction is performed on the filtered partial discharge signal and voltage fluctuation signal to obtain the partial discharge-voltage coupling quantity.

[0064] The partial discharge-voltage disturbance analysis function is: ;in, This indicates the partial discharge signal and voltage fluctuation signal at a specific time point. The nonlinear coupling quantity is used to characterize the degree of disturbance of voltage transients by partial discharge events; Index representing a point in time; This indicates the partial discharge signal and voltage fluctuation signal after filtering. Frequency band index; This represents the total number of frequency bands after filtering of the partial discharge signal and voltage fluctuation signal. This indicates that the partial discharge signal is at the first... The instantaneous energy in each frequency band is obtained by calculating the square energy of the partial discharge signal in that frequency band. Indicates the voltage fluctuation signal at the first Instantaneous amplitude in each frequency band; Indicates the first The reference value of the voltage fluctuation signal in each frequency band is obtained by performing median statistics on the steady-state range of the voltage fluctuation signal in that frequency band. This represents the nonlinear response amplification factor, used to enhance the effect of voltage deviation on coupling quantity; Indicates the first The lag factor for each frequency band is preset based on the phase delay of voltage fluctuations and is used to characterize the time lag of the partial discharge energy response to voltage transients.

[0065] This solution addresses the following technical problems in existing technologies: Traditional partial discharge diagnostic methods rely heavily on amplitude statistics, pulse counting, and PRPD maps, which can only observe the strength, repetition rate, and phase distribution of the partial discharge itself, but cannot characterize the true impact of partial discharge events on voltage transient disturbances; existing monitoring technologies typically analyze partial discharge signals only in a single frequency band or wide bandwidth, leading to the neglect of partial discharge energy variations in different frequency components and the inability to express the time delay response of voltage disturbances in different frequency bands; it is difficult to identify potential risk points of implicit partial discharge energy-voltage sensitive coupling in certain frequency bands. Most systems use the mean or fixed threshold as a reference, which is affected by noise, load fluctuations, etc., leading to misjudgments of partial discharge events and an inability to objectively quantify the degree of voltage anomaly deviation, making it difficult to detect effective disturbances under weak partial discharge conditions. The impact of partial discharge on voltage has a certain phase delay, and existing technologies usually only perform synchronous comparisons without considering the inherent response delay between partial discharge energy release and voltage transients. The different hysteresis characteristics of different frequency components weaken or omit key transient disturbance relationships.

[0066] The advantages over existing technologies are as follows: By constructing a transient correlation deduction mechanism between partial discharge and voltage fluctuations based on a multi-source operating state parameter set, a nonlinear coupling quantitative expression between partial discharge events and voltage disturbances is achieved. This enables the characterization of the actual impact of partial discharge energy on voltage transients from multiple frequency band dimensions, and on this basis, forms a physically meaningful and calculable coupling index, thereby improving the ability to identify weak and latent partial discharges. The obtained coupling quantity between partial discharge and voltage disturbances can be directly integrated into the intelligent operating state assessment system, enhancing the effectiveness and reliability of multi-sensor fusion assessment, and making the judgment of the operating state of cable branch boxes more comprehensive, detailed, and accurate.

[0067] Methods for determining the presence of partial discharge anomalies caused by insulation degradation within cable branch boxes include:

[0068] A preset partial discharge-voltage coupling threshold is set, and the partial discharge-voltage coupling amount is compared with the preset partial discharge-voltage coupling threshold in real time. When the partial discharge-voltage coupling amount is greater than the preset partial discharge-voltage coupling threshold, it is determined that there is a partial discharge abnormality caused by insulation deterioration in the insulation medium inside the cable branch box.

[0069] Methods for assessing the trend of terminal contact status changes include:

[0070] The temporal changes of the terminal temperature signal and the terminal contact resistance signal are analyzed, and the terminal temperature features and terminal contact resistance features are extracted respectively. The terminal temperature features include instantaneous temperature value, temperature rise rate, temperature rise amplitude, and temperature steady-state offset. The terminal contact resistance features include instantaneous contact resistance value, contact resistance change rate, contact resistance abrupt change features, and resistance steady-state offset.

[0071] It should be noted that the instantaneous temperature value is obtained by recording the actual temperature value of the terminal at each sampling time point, reflecting the temperature level of the terminal under real-time operating conditions. The temperature rise rate is obtained by calculating the ratio of the temperature change at adjacent time points to the time interval, i.e., the rate at which the terminal temperature rises over time, reflecting the heating trend of the terminal under load changes or abnormal contact conditions. The temperature rise amplitude is obtained by statistically analyzing the total increase in terminal temperature within a specific time window, used to assess the temperature fluctuation amplitude of the terminal during short-term or long-term operation. The steady-state temperature deviation is obtained by analyzing the deviation of the terminal temperature from the ambient temperature during the stable operating phase, reflecting the thermal equilibrium state and potential overheating of the terminal under continuous load.

[0072] Instantaneous contact resistance is obtained by recording the current contact resistance value of the terminal at each sampling time point, directly reflecting the terminal's conductivity and connection tightness. The contact resistance change rate is obtained by calculating the ratio of the resistance change at adjacent time points to the time interval, used to characterize the trend of terminal contact status changes over time and the rate of abnormal development. Contact resistance abrupt change characteristics are obtained by identifying abrupt increases or decreases in the terminal resistance signal, reflecting potential sudden faults or loosening of the terminal contact status. The steady-state resistance offset is obtained by analyzing the deviation of the terminal contact resistance from the normal reference value during the stable phase, used to reveal long-term poor contact or aging problems.

[0073] The system presets temperature rise thresholds and resistance change rate thresholds, combining terminal temperature characteristics with contact resistance characteristics to analyze the trend of terminal contact status changes. When the temperature rise rate exceeds the preset temperature rise threshold and the contact resistance change rate exceeds the preset resistance change rate threshold, the terminal contact status is determined to be in a degradation trend. Possible causes include: For example, loose or corroded contact points: Loose or oxidized terminal bolts lead to increased contact resistance, and localized heating is exacerbated under current. High load operation: Cable branch boxes continuously bear high currents, increasing contact point temperature rise, and further increasing the resistance of terminals with poor contact. Combined environmental factors: High ambient temperature or poor heat dissipation conditions accelerate the terminal temperature rise rate, speeding up the degradation process.

[0074] When the rate of temperature rise exceeds a preset temperature rise threshold, and the rate of change of contact resistance is less than or equal to a preset rate of change of resistance threshold, the terminal contact condition is determined to be in a potential degradation trend. Possible causes include: For example, abnormal load or ambient temperature: a large current or increased ambient temperature causes a temperature rise, but the contact resistance has not yet changed significantly. Concentrated heat but still good contact: a small terminal structure or conductor cross-section leads to concentrated heat, resulting in localized temperature rise, while the contact point maintains low resistance. Early material degradation: slight degradation of the insulation or metal surface initially manifests as increased sensitivity to temperature rise, while the resistance change is not yet obvious.

[0075] When the rate of temperature rise is less than or equal to a preset temperature rise threshold, and the rate of change of contact resistance is greater than a preset rate of change of resistance threshold, the terminal contact is determined to be in a state of resistance-first degradation. Possible causes include: for example, micro-cracks or oxidation at the contact point: micro-oxidation or cracks on the terminal surface increase contact resistance, but due to the low current, the temperature rise is not yet significant. Low load or good heat dissipation: the terminal carries a small current, and the heat is insufficient to increase the temperature rise, but the change in contact resistance occurs first. Material aging: aging of the metal surface or conductor contact interface increases the rate of change of resistance, but the temperature rise has not yet manifested.

[0076] When the temperature rise rate is less than or equal to a preset temperature rise rate threshold and the contact resistance change rate is less than or equal to a preset resistance change rate threshold, the terminal contact state is considered to be stable. Possible reasons include: For example, a secure and reliable terminal connection results in good contact, low and stable resistance. A moderate load and normal heat dissipation mean that the current and ambient temperature are within normal ranges, resulting in a small terminal temperature rise. Good material properties indicate that there is no oxidation or aging on the terminal metal and conductor surfaces, ensuring stable contact.

[0077] Methods for generating terminal contact anomaly index include:

[0078] Based on the trend of terminal contact state changes, a temperature rise resistance coupling function is constructed for each terminal at each time point to quantify terminal contact abnormalities and calculate the terminal contact abnormality index.

[0079] The temperature rise resistance coupling function is: ;in, Indicator terminals At the point of time Contact abnormality index; Indicator terminals At the point of time The contact resistance value; Indicator terminals At the point of time The actual temperature; Indicates the ambient temperature of the environment where the terminal is located; Indicator terminals At the point of time The square of the current flowing through it;

[0080] It should be noted that the temperature rise resistance coupling function is used to quantify the risk of terminal contact anomalies. It combines three factors: terminal temperature rise, contact resistance, and current flowing through the terminal. The numerator is composed of the difference between the terminal contact resistance and the terminal temperature rise relative to the ambient temperature, used to characterize the local temperature rise effect caused by poor contact. The denominator is the square of the current plus one, used to normalize the actual operating current of the terminal to eliminate the contribution of the normal operating current to the temperature rise, thereby ensuring that the anomaly index mainly reflects the degradation of the terminal contact condition. The calculated terminal contact anomaly index increases with the increase of terminal temperature rise or contact resistance. This method is reasonably based on Joule's law and the physical principle that poor electrical contact leads to local heating. At the same time, the current normalization process improves the sensitivity to early contact degradation, enabling real-time quantitative monitoring and early warning of terminal contact conditions.

[0081] This solution addresses the following technical problems in existing technologies: Traditional methods typically rely solely on monitoring changes in terminal temperature rise or contact resistance to determine terminal status. However, terminal temperature rise is affected by factors such as load current fluctuations and ambient temperature, and using temperature rise alone can easily misjudge normal load temperature increases as abnormalities. Evaluating solely based on changes in contact resistance may fail to detect early contact anomalies in a timely manner, especially when the change in contact resistance is small or at a low rate, making the anomaly easily overlooked. In actual physical phenomena, poor terminal contact can cause localized temperature rises, and there is a non-linear coupling relationship between temperature rise and contact resistance. Existing technologies typically do not establish a mathematical correlation between terminal temperature rise and contact resistance, resulting in limited evaluation accuracy. Furthermore, existing methods often rely on empirical thresholds or qualitative judgments, failing to provide continuous quantitative scoring of terminal status. Both terminal temperature rise and contact resistance can be affected by factors such as operating current and ambient temperature fluctuations, and traditional methods fail to effectively eliminate these interferences, potentially leading to false alarms or missed alarms in anomaly detection.

[0082] Compared to existing technologies, the advantages are as follows: Utilizing the nonlinear coupling relationship between temperature rise and contact resistance, combined with terminal normalization via the square of the current, a continuously quantified contact anomaly index is generated, which can accurately characterize the degree of terminal degradation and anomaly risk. Even in the early stages of terminal contact anomalies, when the temperature rise or contact resistance changes are small, the coupling index can still reflect potential anomalies, thus enabling early identification and warning. It effectively eliminates the interference of normal load current and ambient temperature on terminal temperature rise, making the anomaly index more reliably reflect contact degradation. The terminal contact anomaly index calculated at continuous time points can be used to dynamically monitor terminal status change trends, enabling early warning and maintenance decision support; comprehensively considering the nonlinear relationship between the three key physical quantities of temperature rise, resistance, and current, it more realistically reflects the physical mechanism of terminal contact degradation, with higher accuracy than single-index methods, reducing false alarms and missed alarms.

[0083] Methods for determining whether there is a contact abnormality in the terminals include:

[0084] The terminal contact anomaly index is compared with a preset terminal contact anomaly index threshold to determine whether there is a contact anomaly at the terminal.

[0085] When the terminal contact abnormality index is less than or equal to the preset terminal contact abnormality index threshold, it is determined that there is no contact abnormality in the terminal;

[0086] When the terminal contact abnormality index is greater than the preset terminal contact abnormality index threshold, it is determined that there is a contact abnormality in the terminal.

[0087] Methods for constructing a dual assessment system covering both insulation and mechanical connection conditions include:

[0088] Based on partial discharge-voltage coupling and terminal contact anomaly index, a hierarchical system for insulation risk level range and mechanical connection risk level range is constructed. The real-time acquired partial discharge-voltage coupling is mapped to the corresponding insulation risk level, and the real-time calculated terminal contact anomaly index is mapped to the corresponding mechanical connection risk level.

[0089] According to the preset insulation-connection cross-verification matrix, the mapped insulation risk level and mechanical connection risk level are cross-compared to make the final risk output, forming a dual assessment system covering insulation status and mechanical connection status.

[0090] Based on historical operating samples, engineering experience, or expert experience, a pre-defined insulation degradation grading standard is established. The real-time acquired partial discharge-voltage coupling quantity is mapped to the corresponding insulation risk level according to the pre-defined insulation degradation grading standard. Based on the pre-defined terminal contact anomaly index threshold, the real-time calculated terminal contact anomaly index is mapped to the corresponding mechanical connection risk level.

[0091] Taking the three-level classification as an example, the insulation risk level includes "normal", "warning" and "danger", and the mechanical connection risk level includes "normal", "slight abnormality" and "severe abnormality". The number of levels for insulation risk level and mechanical connection risk level can be expanded according to actual needs to adapt to different accuracy requirements.

[0092] After obtaining the insulation risk level and the mechanical connection risk level, cross-comparison is performed according to the preset insulation-connection cross-verification matrix. The preset insulation-connection cross-verification matrix is ​​used to specify the final risk output rules under different combinations of risk levels, so as to realize the joint judgment of the insulation status and mechanical connection status of the cable branch box.

[0093] The method for setting up the preset insulation-connection cross-validation matrix is ​​as follows: the insulation risk level and the mechanical connection risk level are classified separately; the insulation risk level is used as the row of the insulation-connection cross-validation matrix and the mechanical connection risk level is used as the column of the insulation-connection cross-validation matrix to form a two-dimensional matrix structure for cross-comparison.

[0094] Finally, a pre-set insulation-connection cross-verification matrix is ​​formed and solidified in a preset table format for direct use during operation. The corresponding final risk output can be obtained by querying, thereby determining whether the cable branch box is in normal operation, single-item deterioration risk, or compound deterioration risk.

[0095] For example, if the "insulation risk level is dangerous" and the "mechanical connection risk level is severe abnormality", then the output will be "compound deterioration risk", indicating that there are dual problems with insulation and mechanical connection, and immediate repair is required.

[0096] If the "insulation risk level is dangerous" but the "mechanical connection risk level is normal", then the output will be "single-item deterioration risk (insulation risk)", and an inspection should be arranged with a focus on the aging condition of the cable, and the aging cable section should be replaced or insulation restoration treatment should be implemented.

[0097] If the "insulation risk level is normal" but the "mechanical connection risk level is slightly abnormal", then the output will be "single-item deterioration risk (mechanical connection risk)", and an inspection should be arranged with a focus on the terminal connection status; if both the "insulation risk level and mechanical connection risk level are normal", then the output will be "no risk".

[0098] Methods for generating comprehensive assessment results and corresponding status assessment reports of the operating status of cable branch boxes include:

[0099] The final risk output is used as a comprehensive assessment result of the cable branch box's operating status, and based on the comprehensive assessment result, a status assessment report containing the anomaly type, degree of deterioration, and maintenance recommendations is automatically generated.

[0100] It should be noted that the anomaly type is automatically determined based on the comprehensive assessment results, including "no anomaly", "insulation deterioration", "terminal connection anomaly" and "combined deterioration of insulation and terminal connection". The degree of deterioration is determined based on the comprehensive assessment results and the corresponding insulation risk level and mechanical connection risk level, including "none", "slight" and "severe". For combined deterioration, the degree of deterioration of both insulation and mechanical connection is indicated.

[0101] The system calls upon a pre-defined maintenance rule library to map different anomaly types and deterioration levels to corresponding maintenance suggestions, including checking partial discharge points in aging sections, retesting insulation resistance, checking terminal fastening and contact resistance, re-crimping or replacing terminals, replacing aging cable sections, or implementing insulation restoration. It automatically generates a status assessment report containing anomaly type, deterioration level, and maintenance suggestions, which can be used for display, archiving, or triggering maintenance alarms.

[0102] The preset partial discharge-voltage coupling threshold is set by the staff. By collecting different partial discharge-voltage coupling values, the average value of multiple partial discharge-voltage coupling values ​​is taken as the preset partial discharge-voltage coupling threshold. Similarly, preset terminal contact abnormality index threshold, preset temperature rise threshold, and preset resistance change rate threshold are set.

[0103] This embodiment constructs a transient correlation deduction mechanism between partial discharge (PD) and voltage fluctuations based on a multi-source operating state parameter set, realizing a quantitative expression of the nonlinear coupling between PD events and voltage disturbances. It can characterize the actual impact of PD energy on voltage transients from multiple frequency band dimensions, and on this basis, form a physically meaningful and calculable coupling index, thereby improving the ability to identify weak and latent PD. The obtained coupling quantity between PD and voltage disturbances can be directly integrated into the intelligent operating state assessment system, enhancing the effectiveness and reliability of multi-sensor fusion assessment, and making the judgment of the operating state of cable branch boxes more comprehensive, detailed, and accurate.

[0104] By leveraging the nonlinear coupling relationship between temperature rise and contact resistance, and combining it with terminal normalization via the square of the current, a continuously quantified contact anomaly index is generated, which can accurately characterize the degree of terminal degradation and anomaly risk. Even in the early stages of terminal contact anomalies, when the temperature rise or contact resistance changes are small, the coupling index can still reflect potential anomalies, thus enabling early identification and warning. It effectively eliminates the interference of normal load current and ambient temperature on terminal temperature rise, making the anomaly index more reliably reflect contact degradation. The terminal contact anomaly index calculated at continuous time points can be used to dynamically monitor terminal status change trends, enabling early warning and maintenance decision support. By comprehensively considering the nonlinear relationship between the three key physical quantities—temperature rise, resistance, and current—it more realistically reflects the physical mechanism of terminal contact degradation, with higher accuracy than single-index methods, reducing false alarms and missed alarms.

[0105] Example 2

[0106] Please see Figure 2 As shown, the parts not described in detail in this embodiment are described in Embodiment 1. A method for intelligently assessing the operating status of cable branch boxes based on multi-sensor fusion is provided, including:

[0107] S1. Collect partial discharge signals, voltage fluctuation signals, terminal temperature signals and terminal contact resistance signals of the cable branch box during operation, and construct a multi-source operating status parameter set of the cable branch box through time synchronization and physical quantity normalization processing.

[0108] S2. Based on the multi-source operating state parameter set, perform transient correlation deduction on the partial discharge signal and the corresponding voltage fluctuation signal to obtain the partial discharge-voltage coupling amount; when the partial discharge-voltage coupling amount exceeds the preset partial discharge-voltage coupling amount threshold, it is determined that there is a partial discharge abnormality caused by insulation degradation in the cable branch box.

[0109] S3. Evaluate the trend of terminal contact status change based on terminal temperature signal and terminal contact resistance signal; construct temperature rise resistance coupling function based on terminal contact status change trend to generate terminal contact abnormality index; when terminal contact abnormality index exceeds preset terminal contact abnormality index threshold, it is determined that there is a contact abnormality in the terminal.

[0110] S4. The partial discharge-voltage coupling quantity and the terminal contact anomaly index are hierarchically mapped and cross-validated to construct a dual evaluation system covering insulation status and mechanical connection status, and generate a comprehensive evaluation result and corresponding status evaluation report of the cable branch box operation status.

[0111] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters and thresholds in the formulas are set by those skilled in the art according to the actual situation.

[0112] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for users of ordinary technical skills, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An intelligent assessment system for the operating status of cable branch boxes based on multi-sensor fusion, characterized in that, include: The status acquisition module is used to collect partial discharge signals, voltage fluctuation signals, terminal temperature signals and terminal contact resistance signals of the cable branch box during operation. Through time synchronization and physical quantity normalization processing, a multi-source operating status parameter set of the cable branch box is constructed. The mutual coupling analysis module, based on a multi-source operating state parameter set, performs transient correlation deduction between partial discharge signals and corresponding voltage fluctuation signals to obtain the partial discharge-voltage coupling amount; when the partial discharge-voltage coupling amount exceeds the preset partial discharge-voltage coupling amount threshold, it is determined that there is a partial discharge abnormality caused by insulation degradation in the cable branch box. The method for obtaining the partial discharge-voltage coupling amount includes: Bandpass filtering is applied to the partial discharge signal in the multi-source operating state parameter set, and low-pass filtering is applied to the corresponding voltage fluctuation signal. A partial discharge-voltage disturbance analysis function is constructed, and transient correlation deduction is performed on the filtered partial discharge signal and voltage fluctuation signal to obtain the partial discharge-voltage coupling quantity. The partial discharge-voltage disturbance analysis function is: ;in, This indicates the partial discharge signal and voltage fluctuation signal at a specific time point. The nonlinear coupling quantity is used to characterize the degree of disturbance of voltage transients by partial discharge events; Index representing a point in time; This indicates the partial discharge signal and voltage fluctuation signal after filtering. Frequency band index; This represents the total number of frequency bands after filtering of the partial discharge signal and voltage fluctuation signal. This indicates that the partial discharge signal is at the first... The instantaneous energy in each frequency band is obtained by calculating the square energy of the partial discharge signal in that frequency band. Indicates the voltage fluctuation signal at the first Instantaneous amplitude in each frequency band; Indicates the first The reference value of the voltage fluctuation signal in each frequency band is obtained by performing median statistics on the steady-state range of the voltage fluctuation signal in that frequency band. This represents the nonlinear response amplification factor, used to enhance the effect of voltage deviation on coupling quantity; Indicates the first The lag factor for each frequency band is preset based on the phase delay of voltage fluctuations and is used to characterize the time lag of the partial discharge energy response to voltage transients. The contact assessment module evaluates the trend of terminal contact status changes based on terminal temperature and terminal contact resistance signals; it constructs a temperature rise resistance coupling function based on the trend of terminal contact status changes to generate a terminal contact anomaly index; when the terminal contact anomaly index exceeds a preset terminal contact anomaly index threshold, it determines that the terminal has a contact anomaly. The assessment and decision-making module performs hierarchical mapping and cross-validation of partial discharge-voltage coupling quantity and terminal contact anomaly index, constructs a dual assessment system covering insulation status and mechanical connection status, and generates a comprehensive assessment result and corresponding status assessment report of the cable branch box operation status.

2. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 1, characterized in that, The methods for acquiring the partial discharge signal, voltage fluctuation signal, terminal temperature signal, and terminal contact resistance signal include: High-frequency current sensors are installed at each outgoing and incoming terminal of the cable branch box. The high-frequency current sensors are used to capture the pulse current signal generated by partial discharge. The pulse current signal is processed by bandpass filtering and background noise suppression, and the amplitude, frequency and waveform characteristics of the pulse current signal are continuously recorded to obtain the partial discharge signal of the cable branch box during operation. Voltage monitoring units are connected to the busbar and each branch circuit of the cable branch box to monitor the instantaneous changes in the voltage of each phase in real time; the peak value, amplitude and frequency of voltage fluctuations are continuously recorded, and the occurrence time of voltage drop and surge events is marked, thereby obtaining voltage fluctuation signals. Temperature sensors are arranged on and around the surface of each connection terminal in the cable branch box to continuously record the terminal temperature value, temperature rise rate and temperature rise amplitude, thereby obtaining the terminal temperature signal; By applying a test current across the terminals, the voltage drop at the terminal connection is measured, and the terminal contact resistance value is calculated according to Ohm's law. The changing trend and abrupt change characteristics of the contact resistance value are continuously recorded to obtain the terminal contact resistance signal.

3. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 2, characterized in that, The method for obtaining the multi-source operating state parameter set includes: The collected partial discharge signal, voltage fluctuation signal, terminal temperature signal, and terminal contact resistance signal are time-marked according to a unified clock reference. Signals with inconsistent acquisition periods are synchronized and aligned using linear interpolation or sliding window averaging methods, so that various signals form corresponding data points at the same time node. Signals of different dimensions are normalized so that their amplitudes can be directly compared and fused on a unified numerical scale. Various signals that have undergone time synchronization and normalization are combined into multi-dimensional parameter vectors at each time node, and the multi-dimensional parameter vectors at different time nodes are integrated to form a complete set of multi-source operating state parameters.

4. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 3, characterized in that, The method for determining the presence of partial discharge abnormalities caused by insulation deterioration within the cable branch box includes: A preset partial discharge-voltage coupling threshold is set, and the partial discharge-voltage coupling amount is compared with the preset partial discharge-voltage coupling threshold in real time. When the partial discharge-voltage coupling amount is greater than the preset partial discharge-voltage coupling threshold, it is determined that there is a partial discharge abnormality caused by insulation deterioration in the insulation medium inside the cable branch box.

5. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 4, characterized in that, The method for evaluating the trend of terminal contact state changes includes: The temporal changes of the terminal temperature signal and the terminal contact resistance signal are analyzed, and the terminal temperature features and terminal contact resistance features are extracted respectively. The terminal temperature features include instantaneous temperature value, temperature rise rate, temperature rise amplitude, and temperature steady-state offset. The terminal contact resistance features include instantaneous contact resistance value, contact resistance change rate, contact resistance abrupt change features, and resistance steady-state offset. The system sets a preset temperature rise threshold and a resistance change rate threshold. It combines the terminal temperature characteristics with the contact resistance characteristics to analyze the trend of terminal contact state changes. When the temperature rise rate is greater than the preset temperature rise threshold and the contact resistance change rate is greater than the preset resistance change rate threshold, it is determined that the terminal contact state is in a deterioration trend. When the temperature rise rate is greater than the preset temperature rise threshold and the contact resistance change rate is less than or equal to the preset resistance change rate threshold, the terminal contact state is determined to be in a potential degradation trend. When the temperature rise rate is less than or equal to the preset temperature rise threshold and the contact resistance change rate is greater than the preset resistance change rate threshold, the terminal contact state is determined to be in a state of resistance degradation. When the temperature rise rate is less than or equal to the preset temperature rise rate threshold and the contact resistance change rate is less than or equal to the preset resistance change rate threshold, the terminal contact state is determined to be in a stable state.

6. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 5, characterized in that, The method for generating the terminal contact anomaly index includes: Based on the trend of terminal contact state changes, a temperature rise resistance coupling function is constructed for each terminal at each time point to quantify terminal contact abnormalities and calculate the terminal contact abnormality index.

7. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 6, characterized in that, The method for determining whether there is a contact abnormality at the terminal includes: A preset terminal contact abnormality index threshold is established. The terminal contact abnormality index is compared with the preset threshold to determine whether there is a contact abnormality at the terminal. When the terminal contact abnormality index is less than or equal to the preset terminal contact abnormality index threshold, it is determined that there is no contact abnormality in the terminal; when the terminal contact abnormality index is greater than the preset terminal contact abnormality index threshold, it is determined that there is a contact abnormality in the terminal.

8. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 7, characterized in that, The method for constructing a dual evaluation system covering both insulation and mechanical connection conditions includes: Based on partial discharge-voltage coupling and terminal contact anomaly index, a hierarchical system for insulation risk level range and mechanical connection risk level range is constructed. The real-time acquired partial discharge-voltage coupling is mapped to the corresponding insulation risk level, and the real-time calculated terminal contact anomaly index is mapped to the corresponding mechanical connection risk level. According to the preset insulation-connection cross-verification matrix, the mapped insulation risk level and mechanical connection risk level are cross-compared to make the final risk output, forming a dual assessment system covering insulation status and mechanical connection status.

9. The intelligent evaluation system for the operating status of cable branch boxes based on multi-sensor fusion according to claim 8, characterized in that, The method for generating a comprehensive evaluation result and a corresponding status evaluation report of the cable branch box's operating status includes: The final risk output is used as a comprehensive assessment result of the cable branch box's operating status, and based on the comprehensive assessment result, a status assessment report containing the anomaly type, degree of deterioration, and maintenance recommendations is automatically generated.

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