A high voltage cable branch box joint monitoring device and method

Abstract

The application discloses a kind of high-voltage cable branch box joint monitoring device and method, belong to cable branch box technical field.The device includes support subassembly, detection subassembly, support component and control unit.Support component includes base, first clamping seat and second clamping seat;Base is fixed on the inner wall of branch box, for the rigid fixation of cable root;Detection subassembly includes support seat, first angle sensor, second angle sensor, first positioning sleeve and second positioning sleeve;For obtaining cable swing angle deviation by angle sensor;Support subassembly includes support seat and telescopic component, support seat is fixed on support seat by telescopic component, and it is provided with the support groove matched with joint on it;Control unit is connected with first angle sensor, second angle sensor signal respectively.The application can accurately distinguish joint loosening heating and aging heating, avoid blind power-off, and improve power supply reliability.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable branch box technology, and specifically to a monitoring device and method for high-voltage cable branch box joints. Background Technology

[0002] High-voltage cable distribution boxes, as important connection equipment in power distribution networks, are widely used in urban power supply and industrial power distribution scenarios. European-style high-voltage cable distribution boxes utilize pluggable connectors conforming to European standards. A common wiring configuration is one inlet and two outlets, meaning one incoming cable is branched into two outgoing cables through the internal connectors of the distribution box. In actual structures, the incoming side typically has only one European-style pluggable sleeve, while the outgoing side requires two European-style pluggable sleeves, and the two sleeves and their connected cables are often arranged side-by-side in space.

[0003] Due to the significant weight of the two plug sleeves and cables on the outgoing side, and the limited installation space within the branch box, the supporting structure for these two connectors and cables is typically weak, resulting in a noticeable imbalance in weight distribution on the outgoing side. During long-term operation, the combined effects of cable weight, thermal expansion and contraction, electromagnetic forces, and external environmental vibrations can easily cause relative displacement or overall tilting of the two European-style plug sleeves on the outgoing side, leading to poor contact and loosening of the connectors. Loosening of the connectors directly increases contact resistance, causing localized overheating, and in severe cases, insulation aging, breakdown, or even burnout. Because the two connectors on the outgoing side are close to each other and influence each other, loosening of one connector can also exacerbate the misalignment of the other connector through cable tension.

[0004] For monitoring the condition of high-voltage cable branch box joints, conventional technologies mainly rely on manual inspections or simple online temperature monitoring. However, manual inspections are time-consuming and inefficient, making it difficult to detect sudden potential problems. Some branch boxes equipped with temperature sensors can only issue an alarm when the ambient or surface temperature exceeds a set threshold due to joint heating, making them highly susceptible to false alarms caused by high summer temperatures or high-load operation.

[0005] In the prior art, such as the invention patent with patent number 202411941260.9, a cable joint loosening detection system and method are disclosed. The method includes: acquiring electrical parameter data, joint temperature parameter data, and environmental parameter data at the cable joint under test at preset intervals. The electrical parameter data includes monitoring values ​​of various types of electrical parameters. Pre-stored initial record data is acquired. The influence change value of each electrical parameter is determined based on the joint temperature parameter data, environmental parameter data, and initial record data. The initial record value corresponding to each electrical parameter in the initial record data is determined. A comparison threshold for each electrical parameter is determined based on the initial record value and influence change value. A comparison processing is performed based on each comparison threshold and each monitoring value to obtain the loosening detection result of the cable joint under test. However, the increase in joint temperature and the change in electrical parameters are not entirely caused by physical loosening of the joint. Material aging, natural oxidation of internal contacts, and accumulation of local environmental changes can all cause very similar changes in electrical and temperature characteristics. Furthermore, in the early stages of mechanical loosening of the joint, since the contact surfaces have not yet completely separated, a significant increase in electrical parameters and joint temperature is often not immediately observed. This means that there is a weak correlation between simple changes in temperature and electrical characteristics and early loosening of the joint. Existing technology cannot accurately distinguish whether the current abnormal state is due to joint aging or joint loosening.

[0006] In actual power grid operation and maintenance, the response strategies for different types of hidden dangers are drastically different. If the temperature rise is simply caused by joint aging, the deterioration process is relatively slow, and the system has a time margin for compatible operation, allowing the dispatching department to calmly arrange planned power outages for maintenance. However, if the temperature rise is caused by severe physical loosening due to external force or uneven weight distribution, the contact state is extremely unstable, and arcing and breakdown may occur at any time, requiring extremely high urgency. Current technologies, unable to accurately identify the true cause of electrical and temperature increases, often resort to a one-size-fits-all emergency alarm or direct power outage protection strategy when parameters exceed limits. Blindly taking emergency power outages can cause huge economic losses and seriously affect the reliability of regional power supply. Therefore, it is necessary to research a monitoring device and method for high-voltage cable branch box joints. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide a monitoring device and method for high-voltage cable branch box joints, which effectively solves the problem that existing high-voltage cable branch boxes lack protective measures for plug-in joints on the outgoing side, which easily leads to abnormal alarms.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a high-voltage cable branch box joint monitoring device, comprising a support assembly, a detection assembly, a support assembly, and a control unit; The support assembly includes a base, a first bracket, and a second bracket; the base is fixed to the inner wall of the branch box, and the first and second brackets are disposed on both sides of the base and are used to clamp and fix the first cable and the second cable respectively. The detection assembly includes a support base, a first angle sensor, a second angle sensor, a first positioning sleeve, and a second positioning sleeve; the first angle sensor and the second angle sensor are provided on both sides of the support base, the outer sides of the first positioning sleeve and the second positioning sleeve are respectively fitted onto the first cable and the second cable, and the inner sides of the first positioning sleeve and the second positioning sleeve are respectively connected to the first angle sensor and the second angle sensor. The support assembly includes a support base and a telescopic assembly. The support base is fixed to the support base via the telescopic assembly and has a groove thereon that is adapted to the connector. The control unit is connected to the first angle sensor and the second angle sensor respectively.

[0009] Furthermore, the first angle sensor detects the current swing angle of the first cable in real time, and the second angle sensor detects the current swing angle of the second cable in real time; based on the absolute value of the deviation between the current swing angle and the corresponding initial angle, the first real-time angle deviation and the second real-time angle deviation are obtained. When the angle deviation is greater than the preset angle, it is determined that the connector is loose and an abnormality is detected, and a corresponding connector maintenance reminder is issued.

[0010] Furthermore, the first cable and the second cable are connected in the first plug sleeve and the second plug sleeve, and temperature sensors for obtaining the real-time temperature of the first plug sleeve and the second plug sleeve are respectively provided on both sides of the support.

[0011] Furthermore, the deviation between the measured temperature of the connector output by the temperature sensor and the reference temperature is calculated to obtain the temperature deviation. When the temperature deviation is greater than the temperature deviation threshold, an abnormal connector temperature is detected.

[0012] Furthermore, when an alarm for abnormal joint looseness or abnormal joint temperature is issued, temperature deviation and angle deviation data are collected within a continuous time sliding window before and after the alarm time. The Pearson correlation coefficient between the temperature deviation and the angle deviation is calculated. When the Pearson correlation coefficient is greater than the first correlation threshold, it is determined that the joint is loose, thus causing abnormal temperature, and a danger alarm is issued to trigger the circuit breaker protection.

[0013] Furthermore, the real-time ambient temperature inside the branch box is obtained as the base temperature value; the real-time load current of the cable is obtained through a current transformer mounted on the cable; based on the real-time load current, the theoretical temperature rise of the cable under the current load condition is calculated; the base temperature value and the theoretical temperature rise value are superimposed to generate the current reference temperature.

[0014] Furthermore, the support includes a first support and a second support, which are respectively supported on the bottom of the first and second plug sleeves. Temperature sensors for detecting the temperature of the first and second plug sleeves are respectively provided on the first and second supports.

[0015] Furthermore, the base is provided with a support rod, and the support seat is set at the end of the support rod via a telescopic component. The support seat is slidably fitted onto the support rod and can be locked in place by side screws.

[0016] Furthermore, the telescopic assembly includes a telescopic rod, a pressure plate, a spring, and an end cap. The upper part of the support rod is provided with a telescopic cavity, the spring is disposed in the telescopic cavity, the pressure plate is fixed on the telescopic rod and presses against the spring, the end cap is disposed at the end of the telescopic cavity, and the support seat is fixed on the telescopic rod.

[0017] A method for monitoring high-voltage cable branch box joints, applied to the aforementioned device, includes the following steps: Step S1: Real-time acquisition of the cable swing angle and the measured temperature of the plug sleeve surface; use a filtering algorithm to smooth and denoise the acquired swing angle sequence, filter out high-frequency angle interference caused by environmental resonance, and obtain the effective angle deviation. Step S2: Based on the real-time load current obtained by the current transformer, combined with the ambient temperature value collected by the ambient temperature sensor, calculate the reference temperature, and compare the measured temperature with the reference temperature to obtain the temperature deviation. Step S3: When the effective angle deviation or temperature deviation exceeds the preset threshold, extract the data within the time sliding window; shift the temperature deviation time series forward relative to the effective angle deviation time series by a preset lag time constant, and then calculate the Pearson correlation coefficient between the two. Step S4: If the Pearson correlation coefficient is lower than the threshold, if the effective angle deviation exceeds the preset threshold, and it is determined to be an offset fault, an abnormal looseness maintenance command is issued; if the temperature deviation exceeds the limit and the Pearson correlation coefficient is lower than the threshold, it is determined to be electrical aging, and an aging maintenance command is issued; when the Pearson correlation coefficient is higher than the threshold, it is determined to be a loose and hot joint, and the circuit breaker protection is triggered.

[0018] The beneficial effects of the above technical solution are as follows: In response to the problem of loose joints on the outgoing side of high-voltage cable branch boxes due to double plug-in sleeves and cable weight imbalance, and the shortcomings of existing monitoring methods that cannot distinguish between mechanical loosening and electrical aging, which can easily lead to false alarms or blind power outages, the solution achieves accurate identification and differentiated early warning of the branch box joint status through the coordinated cooperation of support components, detection components and support components, combined with the correlation analysis of angle sensors and temperature sensors.

[0019] In this invention, the first and second retainers in the support assembly rigidly fix the cable root, providing a stable reference for angle measurement. The detection assembly, through a positioning sleeve fitted on the cable, works in conjunction with the angle sensor to acquire the cable angle deviation caused by connector loosening, achieving early detection of mechanical loosening. Compared to manual inspection or simple temperature monitoring, this provides higher sensitivity and real-time performance. The support assembly supports the plug-in sleeve from below, reducing the adverse effects of gravity on the connector and providing a reliable installation position for the temperature sensor.

[0020] This invention further introduces a dynamic reference temperature model based on real-time ambient temperature and load current, enabling temperature deviation judgment to adaptively eliminate interference from seasonal changes and load fluctuations, significantly reducing the false alarm rate. Most importantly, by collecting the angle deviation and temperature deviation sequences within a sliding time window, introducing a hysteresis time constant to compensate for heat conduction delay, and calculating the Pearson correlation coefficient between the two, it successfully distinguishes abnormal joint conditions into a strong positive correlation of mechanical loosening and heating, and a weak or no correlation of electrical / aging heating, thereby implementing differentiated operation and maintenance strategies.

[0021] In summary, this invention effectively solves the problems of weak correlation in joint status monitoring, false alarms, inability to distinguish fault root causes, and inappropriate operation and maintenance strategies in the prior art. It significantly improves the operational safety, power supply reliability, and equipment integrity of high-voltage cable branch boxes, and provides strong technical support for the intelligent operation and maintenance of power distribution networks. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of the main structure of the present invention; Figure 3 This is an internal side view of the monitoring device of the present invention; Figure 4 A schematic diagram of the implementation structure supporting the components; Figure 5 This is a schematic diagram illustrating the implementation logic of Embodiment 1 of the present invention; Figure 6 This is a schematic diagram illustrating the implementation logic of Embodiment 2 of the present invention.

[0023] Reference numerals: 1. Branch box; 2. Outlet chamber; 3. Connector; 4. First plug-in sleeve; 5. Second plug-in sleeve; 6. First cable; 7. Second cable; 8. Crossbeam; 9. Base; 10. First card holder; 11. Second card holder; 12. Support base; 13. First positioning sleeve; 131. First angle sensor; 14. Second positioning sleeve; 141. Second angle sensor; 15. Support rod; 151. Sleeve; 152. Sleeve rod; 16. Support base; 17. Telescopic rod; 18. Pressure plate; 19. Spring; 20. End cap. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1

[0025] This embodiment aims to provide a monitoring device and method for the joints of a high-voltage cable branch box 1, specifically for a European-style high-voltage cable branch box 1 with one inlet and two outlets. For this type of branch box 1, a mounting plate is provided in the middle of the branch box 1, and the two sides of the mounting plate are the inlet chamber and the outlet chamber 2, respectively. In this embodiment, the outlet chamber 2 has two plug-in sleeves acting on the connector 3, resulting in a larger overall weight of the cable on this side, which is prone to imbalance. Under the vibration of the branch box 1, the connector is prone to loosening. At the same time, the existing connector status monitoring structure is difficult to effectively detect whether the connector is loose, leading to problems such as improper operation and maintenance strategies, blind emergency power outages, or delayed maintenance.

[0026] like Figures 1 to 2 As shown, a monitoring device for a high-voltage cable branch box joint 1 includes a support assembly, a detection assembly, a support assembly, and a control unit. It utilizes an angle sensor to monitor the angular deviation of the outgoing cables on both sides in real time, thereby accurately identifying the root cause of the anomaly and guiding maintenance personnel to adopt differentiated handling strategies, achieving status awareness and precise early warning for the branch box joint 1.

[0027] During implementation, the support assembly is used to fix the entire device inside the branch box 1 and provide root constraint for the cables, preventing the impact of external factors pulling the cables from the bottom. The support assembly includes a base 9, a first bracket 10, and a second bracket 11. The base 9 is fixed to the rear or side wall of the branch box 1 by a crossbeam 8, providing rigid support for the entire device. At the same time, to avoid assembly trouble, brackets are set on both sides of the branch box 1, and the crossbeam 8 is placed in the brackets on both sides and fixed by through bolts. The base 9 sits on the crossbeam 8 and is fastened with bolts to fix the base 9.

[0028] like Figure 3 As shown, the first clamping seat 10 and the second clamping seat 11 are disposed on both sides of the base 9 and are used to clamp and fix the first cable 6 and the second cable 7 respectively. The distance between them matches the preset spacing of the two outgoing cables. Each clamping seat includes a lower clamp and an upper clamp, which are locked together by bolts to clamp and fix the main body of the first cable 6 and the second cable 7. The purpose of this arrangement is to provide a clear rigid constraint point for the cables, so that the cable swing angle detected later mainly reflects the loose displacement at the plug-in connection, rather than the elastic bending of the cable itself.

[0029] The detection component is used to sense the angular displacement of the cable relative to its initial installation position. The detection component includes a support base 12, a first angle sensor 131, a second angle sensor 141, a first positioning sleeve 13, and a second positioning sleeve 14. The support base 12 is slidably mounted on a vertically mounted support rod 15 on the base 9 and can be locked to the support rod 15 by a lateral set screw, thus allowing the vertical position of the support base 12 to be adjusted according to the height of different sizes of plug-in sleeves. The first angle sensor 131 and the second angle sensor 141 are fixedly mounted on both sides of the support base 12, respectively. The angle sensor is a single-axis rotary potentiometer, its housing is fixed on the support base 12, and the rotating shaft is hinged to the end of the positioning sleeve via a rigid insulating connecting rod. When the cable swings, the positioning sleeve drives the connecting rod to move, driving the potentiometer shaft to rotate. The resistance value output by the potentiometer is linearly mapped to the current swing angle after analog-to-digital conversion. As another implementation, the angle sensor can also be a MEMS gyroscope, which is directly fixed inside the positioning sleeve. The absolute swing angle is obtained by integrating the swing angular velocity of the positioning sleeve.

[0030] The first positioning sleeve 13 and the second positioning sleeve 14 each adopt a split clamp structure with rubber pads on the inside. They are fixedly fitted onto the outer insulation layers of the first cable 6 and the second cable 7, respectively, and are positioned close to the bottom of the plug-in sleeve. The inner sides of the first positioning sleeve 13 and the second positioning sleeve 14 (the side closest to the support base 12) are connected to the rotating shaft or sensing surface of the first angle sensor 131 and the second angle sensor 141, respectively. When the plug-in sleeve becomes loose, it generates a small-amplitude swing under the operating vibration frequency of the branch box 1, causing the cable to swing around the position of the positioning sleeve. In turn, the positioning sleeve drives the rotating shaft of the angle sensor to rotate synchronously, thereby outputting the current swing angle value in real time.

[0031] like Figure 4As shown, the support assembly is used to support the plug-in sleeve from below, providing auxiliary support and reducing the downward pull of the cable's weight on the connector 3. In implementation, the support assembly includes a support base 16 and a telescopic component. The support base 16 is fixed to the support base 12 via the telescopic component, and it has a groove adapted to the connector. In specific implementation, a support rod 15 is provided on the base 9, the support base 16 is fixed to the end of the support rod 15, the support base 12 is slidably fitted onto the support rod 15, and its installation height can be adjusted by using side screws to change the installation position of the detection component. The telescopic component includes a telescopic rod 17, a pressure plate 18, and a spring 19; the upper part of the support rod 15 has a telescopic cavity, and the spring 19 is installed in the telescopic cavity, forming an elastic buffer structure. The pressure plate 18 is fixed to the telescopic rod 17 and presses against the spring 19. The spring 19 always maintains a certain preload, actively providing upward support to the support base 16, so that the groove can continuously fit against the bottom of the plug-in sleeve. An end cap 20 is provided at the end of the telescopic cavity to limit the stroke of the telescopic rod 17. When the plug sleeve shakes or shifts due to loosening, the telescopic assembly can extend and retract accordingly. The compression and rebound of the spring 19 adaptively adjust the position of the bracket, which not only buffers the impact force transmitted by the plug sleeve, but also ensures that the bracket always maintains stable contact with the connector.

[0032] The support 16 is provided with an arc-shaped groove that matches the bottom shape of the plug-in sleeve, and the surface of the groove can be lined with a high-temperature resistant insulating pad. In a further embodiment, the support 16 includes a first support and a second support, which are independently fixed to the top ends of the support rod 15, respectively supporting the bottom of the first plug-in sleeve 4 and the second plug-in sleeve 5.

[0033] In a further implementation, the support rod 15 includes a sleeve rod 152 and a sleeve 151. The sleeve 151 is fixed on the base 9, the sleeve rod 152 is slidably fitted and can be fixed inside the sleeve 151 by side threads, and the support seat 16 is set at the end of the sleeve rod 152 via a telescopic component. This structure is used to change the height of the support seat 16 to ensure the support effect of the support seat 16.

[0034] The control unit is connected to the first angle sensor 131 and the second angle sensor 141 respectively, and can optionally be connected to the main control circuit breaker or alarm device on the incoming side of branch box 1. The control unit adopts a programmable logic controller or an embedded microprocessor, and has a built-in analog-to-digital conversion module and data storage unit.

[0035] like Figure 5As shown, the first angle sensor 131 detects the current swing angle of the first cable 6 in real time, and the second angle sensor 141 detects the current swing angle of the second cable 7 in real time. Based on the absolute value of the deviation between the current swing angle and the corresponding initial angle, the first real-time angle deviation and the second real-time angle deviation are obtained. When the angle deviation is greater than the preset angle, it is determined that the connector is loose and an abnormality is detected, and a corresponding connector maintenance reminder is issued. The maintenance reminder can be manifested as alarm information on the remote monitoring platform, audible and visual alarm signals, or SMS notifications sent to the mobile phones of maintenance personnel.

[0036] During installation, the crossbeam 8, i.e., the base 9 and its upper support structure, is fixed to the inner wall of the branch box 1 by hoisting or manual assistance. The height of the support base 12 is adjusted so that the first positioning sleeve 13 and the second positioning sleeve 14 are aligned with the corresponding positions of the first cable 6 and the second cable 7, respectively, and locked. At this time, the control unit records the output values ​​of the first angle sensor 131 and the second angle sensor 141 as the initial angle. The initial angle represents the natural suspension posture of the cable in a non-loose state.

[0037] Simultaneously monitor the changing trends of the two angular deviations. If the angular deviation on one side increases continuously within a short period of time, such as 10 minutes, and exceeds the rate threshold, the control unit determines that the loosening is gradually worsening, raises the alarm level, and prompts for immediate maintenance. If the angular deviations on both sides occur simultaneously and exceed the threshold, the control unit determines that the two connectors are loose simultaneously, which may be caused by overall vibration of branch box 1 or external impact, and issues a comprehensive inspection reminder.

[0038] If the angle deviation exceeds the preset safety limit threshold, the control unit determines that the joint is in a semi-disconnected state and may be subject to arc breakdown at any time. It immediately issues an emergency alarm signal and can automatically trigger the upstream circuit breaker to trip according to the site configuration, cut off the fault circuit, and prevent the accident from escalating.

[0039] In this embodiment, the upper part of the cable is fixedly connected in the plug-in sleeve. The support component rigidly fixes the roots of the two outgoing cables through the base 9 and the card slot to avoid interference caused by external dragging of the cable. The support component supports the plug-in sleeve from below through the bracket to reduce the influence of gravity and keep the cable in a straight state. When the connector is loose, the cable can swing with the plug-in sleeve and generate a swing angle as the branch box 1 vibrates. The swing amplitude that the plug-in sleeve can swing is determined according to the swing angle.

[0040] This embodiment records the initial angles of the angle sensors on both sides during installation, continuously monitors the current swing angle during operation and calculates the absolute value of the deviation. When the deviation exceeds a preset threshold, it determines that the corresponding side connector has become mechanically loose and issues a maintenance reminder. At the same time, it monitors the rate of change of the deviation, increases the alarm level for progressive loosening, and automatically triggers the circuit breaker to disconnect the fault circuit when the deviation reaches the safety limit threshold. This achieves direct, quantitative, and early detection of mechanical loosening of the connector in branch box 1. Through a graded alarm strategy, including general loosening reminders, progressive loosening expedited alerts, and extreme loosening power cut-off, it provides clear operation guidance for maintenance personnel, avoiding serious accidents such as a sharp increase in contact resistance and arcing burnout caused by the continuous deterioration of loosening. This significantly improves the safety of branch box 1 operation and the timeliness of maintenance.

[0041] Example 2

[0042] This embodiment further introduces a temperature sensor based on embodiment 1, and combines the correlation analysis between angle deviation and temperature deviation to solve the pain point in the prior art where the rise in joint temperature cannot distinguish between mechanical loosening and electrical aging. This enables a differentiated operation and maintenance strategy, taking emergency power-off protection for highly dangerous loosening and heating, and only arranging planned maintenance for relatively mild aging and heating, thus avoiding power loss caused by blind power outages.

[0043] The difference between this embodiment and Embodiment 1 is that a temperature sensor is added to the support 16, and a reference temperature and Pearson correlation coefficient analysis module are introduced into the control unit.

[0044] In this embodiment, the first cable 6 and the second cable 7 are connected to the first plug sleeve 4 and the second plug sleeve 5. Temperature sensors for acquiring the real-time temperature of the first plug sleeve 4 and the second plug sleeve 5 are respectively provided on both sides of the support 16. The support 16 includes a first bracket and a second bracket, which are respectively supported on the bottom of the first plug sleeve 4 and the second plug sleeve 5. Temperature sensors for detecting the temperature of the first plug sleeve 4 and the second plug sleeve 5 are respectively provided on the first bracket and the second bracket. The temperature sensors are preferably PT100 platinum resistance thermometers or thermocouples, and their sensing surfaces maintain good contact with the plug sleeve housing and are coated with thermally conductive silicone grease to reduce thermal resistance.

[0045] like Figure 6 As shown, the control unit is connected to the first and second temperature sensors respectively. Instead of directly comparing the measured temperature with a fixed threshold, the control unit calculates the deviation between the measured temperature of the connector and the dynamic reference temperature to obtain the temperature deviation. The reference temperature is determined based on the real-time ambient temperature inside branch box 1 and the real-time load current of the cable, and its calculation logic is as follows: The real-time ambient temperature inside branch box 1 is obtained as the base temperature value; the real-time load current of the cable is obtained through the current transformer installed on the cable; based on the real-time load current, the theoretical temperature rise value of the cable under the current load condition is calculated; the base temperature value and the theoretical temperature rise value are superimposed to generate the current reference temperature.

[0046] In practice, an ambient temperature sensor is installed inside branch box 1, away from the heat source, such as near base 9, to acquire the real-time ambient temperature inside branch box 1 as the baseline temperature value. The control unit incorporates a thermodynamic model and, based on real-time load current and cable parameters such as cross-sectional area and insulation thermal resistance, calculates the theoretical temperature rise of the cable under the current load condition according to Joule's law. This theoretical temperature rise reflects the temperature rise level that the joint should reach under normal load conditions. The baseline temperature value is superimposed with the theoretical temperature rise value to generate the current reference temperature. The reference temperature is updated in real-time as the ambient temperature and load current change, allowing temperature deviation judgment to adaptively eliminate the influence of seasonal changes and load fluctuations, greatly reducing the false alarm rate.

[0047] When the deviation between the measured temperature and the reference temperature exceeds a preset temperature deviation threshold, the control unit issues a connector temperature abnormality alarm. However, the abnormal temperature alone cannot determine whether the cause is mechanical loosening or electrical aging. Therefore, this embodiment designs a correlation analysis mechanism.

[0048] When an alarm for loose joint or abnormal joint temperature is issued, temperature and angle deviation data are collected within a continuous time sliding window before and after the alarm time. The Pearson correlation coefficient between the temperature deviation and the angle deviation is calculated. When the Pearson correlation coefficient is greater than the first correlation threshold, it is determined that the joint is loose, which causes abnormal temperature, and a danger alarm is issued to trigger the circuit breaker protection.

[0049] In specific implementation, when the control unit issues a connection looseness alarm based on the angle deviation judgment in Example 1, or an abnormal connection temperature alarm, this embodiment further collects temperature deviation data and angle deviation data within a continuous sliding window before and after the alarm time, for example, from 60 seconds before the alarm time to 60 seconds after the alarm time, forming two time series. Considering the physical delay in heat conduction from the contact point to the surface of the plug sleeve, typically tens of seconds, the control unit shifts the temperature deviation time series forward relative to the angle deviation time series by a preset lag time constant. This constant can be calibrated through prior experiments, for example, 30 seconds. Then, the Pearson correlation coefficient between the two shifted series is calculated. The Pearson correlation coefficient is chosen instead of other correlation indicators because field tests have shown that the temperature and angle signals caused by loosening approximately follow a normal distribution, and the Pearson coefficient has the best sensitivity and noise immunity under these conditions.

[0050] The Pearson correlation coefficient ranges from -1 to 1. When the Pearson correlation coefficient is greater than the first correlation threshold (e.g., 0.7), a strong positive correlation is determined between the temperature rise and the angular oscillation, meaning the temperature anomaly is caused by increased contact resistance due to mechanical loosening. This situation is extremely dangerous because the loosening may further deteriorate and trigger arcing. The control unit immediately issues a danger alarm and triggers the circuit breaker on the outgoing or incoming side to trip, disconnecting the faulty circuit.

[0051] When the Pearson correlation coefficient is below the first correlation threshold but the temperature deviation exceeds the limit, it is determined that the temperature rise is weakly or unrelated to the angle swing, meaning the heating is not caused by mechanical loosening but rather by electrical aging, such as contact oxidation, plating wear, spring 19 pressure decay, or long-term overload operation. In this case, the control unit only issues an aging maintenance command or overload warning, without triggering an emergency power cut, allowing the equipment to continue operating, with maintenance personnel arranging a power outage for maintenance according to the production plan.

[0052] If the Pearson correlation coefficient is negative and has a large absolute value, such as less than -0.5, it is considered an abnormal state. This may be due to a malfunction of the temperature sensor or angle sensor, or the presence of external interference, such as strong vibration causing the two signals to change in opposite directions. The control unit will then issue a sensor self-check reminder.

[0053] Through the aforementioned hierarchical diagnostic strategy based on correlation analysis, this embodiment accurately classifies abnormal joint conditions into dangerous loosening and overheating and general aging and overheating. The former triggers emergency protection, while the latter only prompts planned maintenance, effectively solving the problems of false alarms and blind power outages, and significantly improving power supply reliability and equipment safety.

[0054] Based on this, this embodiment further provides a method for monitoring the joints of a high-voltage cable branch box 1, including the following steps: Step S1: Real-time acquisition of the cable swing angle and the measured temperature of the plug sleeve surface; use a filtering algorithm to smooth and denoise the acquired swing angle sequence, filter out high-frequency angle interference caused by environmental resonance, and obtain the effective angle deviation. Step S2: Based on the real-time load current obtained by the current transformer, combined with the ambient temperature value collected by the ambient temperature sensor, calculate the reference temperature, and compare the measured temperature with the reference temperature to obtain the temperature deviation. Step S3: When the effective angle deviation or temperature deviation exceeds the preset threshold, extract the data within the time sliding window; shift the temperature deviation time series forward relative to the effective angle deviation time series by a preset lag time constant, and then calculate the Pearson correlation coefficient between the two. Step S4: If the Pearson correlation coefficient is lower than the threshold, if the effective angle deviation exceeds the preset threshold, and it is determined to be an offset fault, an abnormal looseness maintenance command is issued; if the temperature deviation exceeds the limit and the Pearson correlation coefficient is lower than the threshold, it is determined to be electrical aging, and an aging maintenance command is issued; when the Pearson correlation coefficient is higher than the threshold, it is determined to be a loose and hot joint, and the circuit breaker protection is triggered.

[0055] This embodiment further introduces a temperature sensor and a dynamic reference temperature model. The temperature deviation is obtained by calculating the deviation between the measured temperature of the connector and the reference temperature determined by the real-time ambient temperature and load current. When an angle deviation or temperature deviation triggers an alarm, the control unit collects two sets of data within a sliding time window. The temperature deviation sequence is shifted forward relative to the angle deviation sequence by a preset lag time constant to characterize the heat conduction delay. The Pearson correlation coefficient between the two is calculated, thereby accurately distinguishing abnormal states into those with a strong positive correlation to mechanical loosening and heating, and those with a weak or no correlation to electrical / aging heating. This effectively overcomes the shortcomings of existing technologies that cannot distinguish the root cause of heating based solely on temperature exceeding limits. For highly dangerous loosening and heating, the circuit breaker protection is immediately triggered to prevent arcing and burnout. For relatively mild aging heating, only planned maintenance is prompted, eliminating power loss caused by blind emergency power outages. Simultaneously, by using a dynamic reference temperature to adapt to the current load and ambient temperature, the false alarm rate is greatly reduced, significantly improving the intelligence, power supply reliability, and equipment safety of the branch box 1 connector monitoring.

[0056] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. The basic concept of the present invention lies in using an angle sensor to monitor the angular deviation of the cables on both sides in real time to identify mechanical loosening, and combining this with the correlation analysis of the signals from the temperature sensor and the angle sensor to distinguish between heat generated by loosening and heat generated by aging, thereby achieving adaptive and differentiated monitoring of the connector in branch box 1. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A monitoring device for high-voltage cable branch box joints, characterized in that: Includes support components, detection components, support components, and control units; The support assembly includes a base, a first bracket, and a second bracket; the base is fixed to the inner wall of the branch box, and the first and second brackets are disposed on both sides of the base and are used to clamp and fix the first cable and the second cable respectively. The detection assembly includes a support base, a first angle sensor, a second angle sensor, a first positioning sleeve, and a second positioning sleeve; the first angle sensor and the second angle sensor are provided on both sides of the support base, the outer sides of the first positioning sleeve and the second positioning sleeve are respectively fitted onto the first cable and the second cable, and the inner sides of the first positioning sleeve and the second positioning sleeve are respectively connected to the first angle sensor and the second angle sensor. The support assembly includes a support base and a telescopic assembly. The support base is fixed to the support base via the telescopic assembly and has a groove thereon that is adapted to the connector. The control unit is connected to the first angle sensor and the second angle sensor respectively; The first angle sensor detects the current swing angle of the first cable in real time, and the second angle sensor detects the current swing angle of the second cable in real time; the angle deviation is obtained based on the current swing angle and the corresponding initial angle. When the angle deviation is greater than the preset angle, it is determined that the connector is loose and an abnormality is detected, and a corresponding connector maintenance reminder is issued. The first cable and the second cable are connected in the first plug sleeve and the second plug sleeve, and temperature sensors for obtaining the real-time temperature of the first plug sleeve and the second plug sleeve are respectively provided on both sides of the support. The deviation between the measured temperature of the connector output by the temperature sensor and the reference temperature is calculated to obtain the temperature deviation. When the temperature deviation is greater than the temperature deviation threshold, an abnormal connector temperature is detected. When an alarm for loose joint or abnormal joint temperature is issued, temperature and angle deviation data are collected within a continuous time sliding window before and after the alarm time. The Pearson correlation coefficient between the temperature deviation and the angle deviation is calculated. When the Pearson correlation coefficient is greater than the first correlation threshold, it is determined that the joint is loose, which causes abnormal temperature, and a danger alarm is issued to trigger the circuit breaker protection.

2. The high-voltage cable branch box joint monitoring device according to claim 1, characterized in that: The real-time ambient temperature inside the branch box is obtained as the base temperature value; The real-time load current of the cable is obtained by using a current transformer mounted on the cable. Based on the real-time load current, the theoretical temperature rise of the cable under the current load condition is calculated. The base temperature value and the theoretical temperature rise value are superimposed to calculate the current reference temperature.

3. The high-voltage cable branch box joint monitoring device according to claim 2, characterized in that: The support includes a first support and a second support, which are respectively supported on the bottom of the first and second plug sleeves. Temperature sensors for detecting the temperature of the first and second plug sleeves are respectively provided on the first and second supports.

4. The high-voltage cable branch box joint monitoring device according to claim 1, characterized in that: The base is provided with a support rod, and the support seat is set at the end of the support rod via a telescopic component. The support seat is slidably fitted onto the support rod and can be locked in place by side screws.

5. The high-voltage cable branch box joint monitoring device according to claim 4, characterized in that: The telescopic assembly includes a telescopic rod, a pressure plate, a spring, and an end cap. The upper part of the support rod is provided with a telescopic cavity, the spring is disposed in the telescopic cavity, the pressure plate is fixed on the telescopic rod and presses against the spring, the end cap is disposed at the end of the telescopic cavity, and the support seat is fixed on the telescopic rod.

6. A method for monitoring high-voltage cable branch box joints, applied to the device described in any one of claims 1-5, characterized in that, Includes the following steps, Step S1: Real-time acquisition of the cable swing angle and the measured temperature of the plug sleeve surface; use a filtering algorithm to smooth and denoise the acquired swing angle sequence, filter out high-frequency angle interference caused by environmental resonance, and obtain the effective angle deviation. Step S2: Based on the real-time load current obtained by the current transformer, combined with the ambient temperature value collected by the ambient temperature sensor, calculate the reference temperature, and compare the measured temperature with the reference temperature to obtain the temperature deviation. Step S3: When the effective angle deviation or temperature deviation exceeds the preset threshold, extract the data within the time sliding window; shift the temperature deviation time series forward relative to the effective angle deviation time series by a preset lag time constant, and then calculate the Pearson correlation coefficient between the two. Step S4: If the Pearson correlation coefficient is lower than the threshold, if the effective angle deviation exceeds the preset threshold, and it is determined to be an offset fault, an abnormal looseness maintenance command is issued; if the temperature deviation exceeds the limit and the Pearson correlation coefficient is lower than the threshold, it is determined to be electrical aging, and an aging maintenance command is issued; when the Pearson correlation coefficient is higher than the threshold, it is determined to be a loose and hot joint, and the circuit breaker protection is triggered.

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