A method for monitoring and heating adjustment of temperature and humidity inside a distribution box

Abstract

The application provides a power distribution box internal temperature and humidity monitoring and heating regulation method, comprising the following steps: according to the spatial position in the cold bridge node characteristic data set, a temperature measuring probe is attached to the surface of a corresponding outgoing terminal, and a temperature and humidity probe is arranged inside the power distribution box away from the circuit breaker heating area, filtered wall surface temperature sequence, box air temperature and relative humidity time series data are synchronously acquired, and a dew point temperature trajectory is generated; the residual amount of the filtered wall surface temperature sequence and the dew point temperature trajectory is calculated, when the residual amount in a continuous sampling period is lower than a preset threshold, it is determined that the power distribution box cold bridge node has a dewing risk and a heating trigger instruction is generated; according to the target input heat energy and the target heating unit rated power, time slices are divided according to a fixed modulation period, a digital pulse width modulation signal is generated and output to the target heating unit through a driving circuit, and dewing prevention heating is implemented on the power distribution box cold bridge node.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for monitoring and regulating the temperature and humidity inside a distribution box and adjusting its heating. Background Technology

[0002] Distribution boxes are responsible for low-voltage power distribution, branch control, and fault protection. They typically contain DIN rail circuit breakers, busbars, terminal blocks, and incoming / outgoing conductors. Condensation inside the box can degrade insulation performance and may cause terminal creepage or short circuits. Therefore, anti-condensation heating is crucial for ensuring the stable operation of the distribution box. Current anti-condensation methods often use fixed-position continuous heating, failing to fully consider the differentiated heat transfer paths between the conductive components of the distribution box and the external wiring. In outdoor or semi-outdoor environments, the branch outgoing terminals installed on the circuit breakers or terminal blocks are continuously connected to the external load lines via copper or aluminum conductors. When the external temperature drops or the humidity inside the box increases due to the opening and closing of the box door, the outgoing conductors form internal and external heat conduction channels through the distribution box's outgoing holes, causing the outgoing terminal temperature to be lower than other areas inside the box and approaching the dew point first, forming cold bridge nodes. Conventionally, the closer the heating element is to the cold bridge node, the faster the node surface heats up. However, the thermal conductivity of the conductor is much higher than that of the outer insulation material; when the heating element is too close to the outlet terminal, the heat will not be effectively accumulated on the terminal surface before it will continue to be transmitted to the outside of the box along the branch outlet conductor and dissipated on the low-temperature load line side. Summary of the Invention

[0003] This invention provides a method for monitoring and regulating the temperature and humidity inside a distribution box and adjusting its heating, mainly including: Obtain surface temperature images of branch line terminals in the distribution box, mark the parts with temperatures lower than the surrounding preset temperature difference as cold bridge nodes, determine spatial coordinates based on circuit number, read the core material code and nominal cross-sectional area specification of the circuit conductor, and generate a cold bridge node feature dataset. Based on the spatial location in the cold bridge node feature dataset, temperature probes are attached to the surface of the corresponding outgoing terminals, and temperature and humidity probes are deployed in areas away from the circuit breaker heating zone. The filtered wall temperature sequence, the air temperature inside the box, and the relative humidity data are acquired simultaneously to generate a dew point temperature trajectory. The residual between the filtered wall temperature sequence and the dew point temperature trajectory is calculated. If the residual is lower than the preset threshold within a continuous sampling period, it is determined that there is a risk of condensation at the cold bridge node and a heating trigger command is generated. In response to the heating trigger command, the thermal conductivity is obtained from the physical property parameter library by parsing the core material code and looking up the relationship table between the thermal resistance of the conductor and the distance by combining the nominal cross-sectional area specification. The target heating distance is obtained based on the trajectory of the steady-state temperature of the terminal surface being higher than the dew point temperature and the axial heat loss being controlled. Obtain the three-dimensional installation coordinate set of each heating element on the back panel of the distribution box, calculate the Euclidean distance between the coordinates of each element and the cold bridge node to determine the target heating unit, read the rated power of the target heating unit, and obtain the initial input heat energy in combination with the target heating distance. Evaluate the amount of heat loss along the conductor to the outside of the box based on the thermal conductivity of the conductor core, and obtain the target input heat energy after compensating for the heat loss. Based on the target input thermal energy and the rated power of the target heating unit, time slices are divided according to a fixed modulation period to generate a digital pulse width modulation signal, which is then output to the target heating unit via a drive circuit to implement anti-condensation heating for the cold bridge node.

[0004] Furthermore, acquiring the surface temperature image of the branch line outgoing terminals inside the distribution box includes: Infrared thermal imagers are used to scan the branch outlet terminals. After grayscale normalization and median filtering, the temperature distribution map of the terminal surface is obtained. The temperature pixel values ​​of the outlet terminals and the adjacent busbars and guide rail back plate areas are extracted and the difference is obtained to obtain the local temperature difference. The outlet terminals whose local temperature difference exceeds the preset temperature difference threshold are marked as cold bridge nodes. According to the circuit wiring ledger, the spatial coordinates are determined by mapping to the three-dimensional coordinate system inside the box according to the circuit number.

[0005] Furthermore, the step of attaching a temperature probe to the surface of the corresponding outgoing terminal based on the spatial location in the cold bridge node feature dataset includes: The temperature sensing surface of the temperature probe is covered with thermally conductive silicone grease and attached to the terminal surface. Temperature and humidity probes are deployed on the wall surface, avoiding the heating area of ​​the circuit breaker. A sliding window mean filter is used to remove high-frequency noise to obtain the filtered wall temperature sequence and air temperature and relative humidity sequence. The dew point temperature value is calculated and connected in ascending order of timestamps to obtain the dew point temperature trajectory.

[0006] Furthermore, the calculation of the margin between the filtered wall temperature sequence and the dew point temperature trajectory includes: The temperature margin sequence at each time point is obtained by subtracting the values ​​at the same timestamp. The values ​​within a continuous sampling period are read from the temperature margin sequence and compared with a preset threshold. When the temperature margin values ​​within a continuous sampling period are all lower than the preset threshold, it is determined that the cold bridge node has a risk of condensation, and a heating trigger command is output to the heating control port of the monitoring main control unit.

[0007] Furthermore, in response to the heating trigger command, the thermal conductivity is obtained from the physical property parameter library by parsing the core material code, and the relationship between conductor thermal resistance and distance is looked up in the nominal cross-sectional area specification table. Based on the terminal surface steady-state temperature being higher than the dew point temperature trajectory and axial heat loss being controlled, the target heating distance is obtained, including: The thermal conductivity and equivalent thermal conductivity of the insulation sheath are retrieved from the physical property parameter library according to the core material code. The thermal resistance value corresponding to the thermal resistance and distance relationship table is read according to the nominal cross-sectional area specification to obtain the thermal resistance profile along the conductor axis. The temperature margin constraint is set with the steady-state temperature of the terminal surface being higher than the dew point temperature trajectory. The axial heat loss constraint is set with the axial heat loss being lower than the heat loss upper limit set according to the preset ratio of the rated power of the heating unit. A binary search is used to traverse the axial distance value along the thermal resistance profile and substitute it into the steady-state heat conduction equation to calculate the steady-state temperature value of the terminal surface and the axial heat loss value. The axial distance value that satisfies both constraints is determined as the target heating distance.

[0008] Furthermore, obtaining the target heating distance includes: A one-dimensional heat transfer path is established along the outgoing conductor towards the outlet hole of the distribution box, starting from the spatial location of the cold bridge node. The heat transfer path is divided into continuous thermal resistance segments according to the distance nodes. The steady-state temperature and axial heat loss of the terminal surface at the end of each segment are calculated. The end of the segment with a steady-state temperature higher than the dew point temperature trajectory and an axial heat loss lower than the preset heat loss upper limit is included in the heat transfer range. The axial position of the next segment with an axial heat loss higher than the preset heat loss upper limit is marked as the target heating distance.

[0009] Furthermore, reading the rated power of the target heating unit includes: The Euclidean distance between the three-dimensional coordinates of each heating element and the spatial position of the cold bridge node is traversed, and the heating element with the smallest Euclidean distance value is determined as the target heating unit. The rated power of the target heating unit is then read from the heating element ledger.

[0010] Furthermore, after reading the rated power of the target heating unit from the heating element ledger, the process includes: The initial input heat energy value is obtained by multiplying the temperature rise required for the terminal surface to rise to the target steady-state temperature above the dew point temperature trajectory with the specific heat capacity and mass of the conductor segment within the target heating distance range. The shunt coefficient is read, and the heat loss along the outgoing conductor to the outside of the distribution box is obtained by multiplying the shunt coefficient with the rated power value. The heat loss value is added to the initial input heat energy value to obtain the target input heat energy.

[0011] Furthermore, the step of dividing time slices according to a fixed modulation period based on the target input thermal energy and the rated power of the target heating unit includes: The total conduction time is obtained by the ratio of the target input heat energy to the rated power. The total conduction time is divided into continuous time slices according to the fixed modulation period. The duty cycle of each time slice is determined by the ratio of the target input heat energy component of the current time slice to the product of the fixed modulation period and the rated power. The digital pulse width modulation signal is generated according to the duty cycle of each time slice and output to the target heating unit through the drive circuit to implement anti-condensation heating for the cold bridge node.

[0012] Furthermore, the step of generating the digital pulse width modulation signal and outputting it to the target heating unit via a driving circuit includes: The terminal surface temperature of the target heating unit after it is put into operation is collected and the dew point temperature trajectory is read synchronously at the same timestamp. The terminal surface temperature value is subtracted from the dew point temperature value point by point to obtain the operating temperature margin sequence. The deviation time slices where the temperature margin is lower than the preset threshold and the return time slices where it rises back to above the preset threshold are calibrated. Periodic adjustment segments are generated and connected to the end of the digital pulse width modulation signal according to the timestamp and output by the driving circuit.

[0013] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a method for monitoring temperature and humidity and regulating heating inside a distribution box. Addressing the problem that cold bridges can easily cause localized low temperatures at the branch terminals of DIN rail circuit breakers and terminal blocks within the distribution box, leading to condensation and threatening electrical safety, the method identifies cold bridge nodes with temperatures below a preset temperature difference from the surrounding area by collecting terminal surface temperature images. A feature dataset of cold bridge nodes is constructed by combining circuit number, wire core material code, and nominal cross-sectional area. Temperature probes are attached to the cold bridge nodes, and temperature and humidity probes are deployed away from the circuit breaker's heating zone to simultaneously acquire wall temperature and dew point temperature trajectories. Heating is triggered when the margin is continuously below a threshold. Furthermore, based on the relationship between conductor thermal resistance and distance, and thermal conductivity, the method traces the target heating distance along the outgoing conductor to ensure the terminal steady-state temperature is above the dew point and axial heat loss is controlled. The target heating unit is determined by traversing the coordinates of the backplate heating elements. Based on the initial thermal energy input, the method compensates for heat loss along the conductor, generates a digital pulse width modulation signal, and dynamically extends the conduction or cutoff state according to the temperature margin. This invention achieves precise positioning of cold bridge nodes and dynamic anti-condensation heating under thermal balance constraints, effectively suppressing axial heat loss and significantly improving the operational safety and energy efficiency of the distribution box. Attached Figure Description

[0014] Figure 1 This is a flowchart of a method for monitoring and regulating the internal temperature and humidity of a power distribution box according to the present invention.

[0015] Figure 2 This is a schematic diagram of a method for monitoring and regulating the internal temperature and humidity of a power distribution box according to the present invention.

[0016] Figure 3 This is another schematic diagram of a method for monitoring and regulating the internal temperature and humidity of a distribution box according to the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0018] like Figures 1-3 This embodiment of a method for monitoring and regulating the temperature and humidity inside a distribution box and adjusting heating may specifically include: S101. Obtain the surface temperature image of the branch outgoing terminals installed on the rail-mounted circuit breaker or terminal block in the distribution box, identify local low-temperature areas where the surface temperature is lower than the preset temperature difference of the surrounding area and mark them as cold bridge nodes, determine their spatial coordinates according to the circuit number and installation location, read the conductor core material code and nominal cross-sectional area specification of the circuit conductor, and generate a cold bridge node feature dataset containing spatial location, material properties and geometric dimensions.

[0019] An infrared thermal imager is used to scan the branch outgoing terminals of the DIN rail circuit breakers and terminal blocks inside the distribution box to obtain surface temperature images covering the areas of each outgoing terminal. The surface temperature images are then subjected to grayscale normalization and median filtering to remove reflective spots and noise interference, resulting in a terminal surface temperature distribution map. From this temperature distribution map, the surface temperature pixel values ​​of each outgoing terminal and the temperature pixel values ​​of adjacent busbars and the DIN rail backplate area are extracted, and the difference between the two is used to obtain the local temperature difference. For each outgoing terminal location, a preset temperature difference threshold is read. If the surface temperature of a certain outgoing terminal is lower than the temperature of the adjacent area and the local temperature difference exceeds the preset temperature difference threshold, the outgoing terminal is determined to be a cold bridge node and the area is marked. The corresponding circuit number is retrieved from the marked cold bridge nodes, and the circuit number is mapped to the three-dimensional coordinate system inside the box according to the distribution box circuit wiring ledger to determine the spatial coordinates of each cold bridge node. Based on the circuit number, the conductor core material code and nominal cross-sectional area specification of the outgoing conductor of the branch circuit are read from the circuit list of the distribution box. The conductor core material code is used to identify the copper or aluminum core type, and the nominal cross-sectional area specification is used to identify the cross-sectional size of the conductor. The spatial coordinates, conductor core material code and nominal cross-sectional area specification are sequentially filled into the structured fields according to the cold bridge node identifier, and the cold bridge node feature dataset is obtained by serializing and encapsulating it in the form of key-value pairs.

[0020] In one embodiment, the infrared thermal imager is installed on the upper part of the inner wall of the distribution box or on the inside of the box door, with the lens facing the area where the guide rail circuit breaker and terminal block are located, and the scanning angle covering the exposed metal surface of each branch outgoing terminal. The temperature pixel resolution acquired by the infrared thermal imager is not less than one pixel per millimeter, and the sampling frame rate is set to acquire one frame every 10 to 30 seconds according to the slow change characteristics of the temperature change inside the distribution box.

[0021] For example, for a distribution box with 12 branch outgoing lines, a single frame surface temperature image covers all 12 outgoing terminals and their adjacent busbar areas, thereby forming a contrast reference between the terminals and the background in the same image.

[0022] Specifically, grayscale normalization is used to map surface temperature images acquired in different batches to a numerical range of 0 to 255, in order to eliminate baseline deviations introduced by detector response inhomogeneities, ambient temperature drift, and lens cold reflections. Normalization involves reading the lowest temperature of the current frame. With the highest temperature ,Will The corresponding pixel is set to 0. The corresponding pixel is set to 255, and the intermediate temperature is obtained by linear interpolation. The mapping relationship is as follows: Where T is the original temperature and g is the normalized gray value; at the same time, , The metadata for this frame is saved along with the image. The median filtering uses... or A sliding window is used to replace the original value of each pixel with the median value within the window, thereby filtering out isolated bright spots formed by high reflectivity areas on the terminal metal surface, as well as salt-and-pepper noise introduced by circuit self-heating and electromagnetic interference. After the above processing, a grayscale distribution map of the terminal surface is obtained, and then... The inverse transformation is performed to obtain the terminal surface temperature distribution map corresponding to the actual temperature of each pixel. Its typical temperature resolution is 0.1 degrees Celsius, which can be directly used for subsequent local temperature difference calculation in degrees Celsius and comparison and judgment of threshold 3 to 5 degrees Celsius.

[0023] It should be noted that each pixel in the terminal surface temperature distribution map corresponds to an actual temperature value. When extracting the pixel value corresponding to the temperature, a terminal contour mask is pre-calibrated in the image coordinate system according to the actual geometric contour of each outgoing terminal during the distribution box commissioning phase. This terminal contour mask is a binary region map covering the metal surface area of ​​the terminal, used to lock the pixel range of the terminal surface in each subsequent frame image. Simultaneously, adjacent busbar and guide rail backplate areas are locked according to the busbar orientation and the geometric position of the guide rail backplate. The average value of pixels in both types of areas is taken to obtain the average terminal surface temperature and the average temperature of adjacent areas. The difference between the two is used to obtain the local temperature difference at the outgoing terminal. The above operation is repeated for all outgoing terminals to form a local temperature difference field covering all branch outgoing terminals within the box.

[0024] In one possible implementation, the preset temperature difference threshold is set according to the environmental category of the distribution box.

[0025] For example, the outdoor distribution box is set to 3 to 5 degrees Celsius, and the semi-outdoor distribution box is set to 2 to 4 degrees Celsius. The specific values ​​within this range are adjusted according to the historical condensation frequency of the distribution box. This historical condensation frequency is collected jointly by the humidity sensor and infrared temperature measurement module built into the distribution box, using the most recent 12 calendar months as the statistical period. Values ​​indicating the presence of condensation droplets or a surface relative humidity greater than [value missing] are considered. Events where the surface temperature is lower than the dew point temperature are counted as one occurrence, and archived monthly by the operation and maintenance system to form a ledger. If the cumulative number of occurrences in a year is no more than 2, it is considered low frequency, and the upper limit of the interval is used: 5 degrees Celsius for outdoor distribution boxes and 4 degrees Celsius for semi-outdoor distribution boxes. If the number of occurrences is between 3 and 6, it is considered medium frequency, and the median of the interval is used: 4 degrees Celsius for outdoor distribution boxes and 3 degrees Celsius for semi-outdoor distribution boxes. If the number of occurrences is no less than 7, it is considered high frequency, and the lower limit of the interval is used: 3 degrees Celsius for outdoor distribution boxes and 2 degrees Celsius for semi-outdoor distribution boxes. For distribution boxes that have been in operation for less than 12 months, a temporary value is taken based on the average value of similar distribution boxes in the same substation, and will be corrected after the data accumulation period is complete. When the temperature difference value of a certain outgoing terminal in the local temperature difference field exceeds the preset temperature difference threshold, the surface temperature of that outgoing terminal is significantly lower than that of the adjacent busbar and guide rail backplate, and it is determined to be a cold bridge node.

[0026] Preferably, identified cold bridge nodes are marked with rectangular bounding boxes in the image, and the corresponding branch circuit number is written into the image metadata. The branch circuit number is derived from the circuit list at the time of manufacture of the distribution box and corresponds one-to-one with the circuit breaker installation slot.

[0027] Specifically, the wiring logbook for the distribution box records the circuit breaker installation slot number, guide rail number, terminal block connection number, and corresponding branch name for each circuit. Using the view of the box after removing the door and looking directly at the box, the lower left corner of the box is taken as the origin of the coordinate system. The horizontal axis (x) points to the right along the length of the guide rail, the vertical axis (y) points upwards along the spacing between guide rails, and the vertical axis (z) points from the mounting backplate to the observer along the depth of the box. When only a single row of guide rails is arranged inside the box, the vertical axis direction is still determined according to the direction perpendicular to the length of the guide rail in the plane of the backplate. The longitudinal offset of the guide rail centerline is taken as the measured distance from that row of guide rails to the bottom edge of the box. After finding the guide rail number (r), slot number (n), and terminal block connection number (t) in the logbook using the circuit number, the coordinates are converted according to the following process. Horizontal axis coordinates... Where x0 is the distance from the center of the first slot of the guide rail to the left inner wall of the box, which is 20 mm; p is the standard module step distance, which is 18 for a single-pole circuit breaker with a width of 18 mm, and for multi-pole circuit breakers, the actual module is accumulated; the vertical axis coordinate y is the longitudinal offset of the center line of the installation row corresponding to the guide rail number r in the ledger, and the values ​​for each row are given by the box structure table, for example, the first row is 85 mm and the second row is 160 mm; the vertical axis coordinate z is the value according to the layer where the node is located, which is 60 mm for the circuit breaker inlet and outlet terminal layer, and 40 mm for the terminal block wiring position layer according to the center height of the position number t on the terminal block, plus the position difference between t and the first and second positions of the terminal block multiplied by 8 mm. Taking slot number N07 as an example, it falls in the 7th 18mm module position of the first row of guide rails. The horizontal axis of 420mm is calculated by multiplying 20 + 7 by 18 to obtain 146mm, and also includes the offset of the reserved section of the front busbar to the starting point of this slot. The specific value is subject to the enclosure structure table. The vertical axis of 85mm comes from the offset of the center line of the first row of guide rails. The vertical axis of 60mm corresponds to the height of the circuit breaker terminal layer. Based on this, the spatial coordinates of each cold bridge node in the enclosure are obtained.

[0028] In one embodiment, the conductor material code is represented by two characters, where Cu represents copper and Al represents aluminum. The nominal cross-sectional area specification is represented by a national standard value, taking a value from 1.5, 2.5, 4, 6, 10, 16, 25, 35, or 50 square millimeters. Both the conductor material code and the nominal cross-sectional area specification are read from the distribution box circuit register by circuit number index.

[0029] For example, if the loop number corresponding to a cold bridge node is N07, and the loop register shows that the conductor core material code for this loop branch is Cu, and the nominal cross-sectional area is 10 square millimeters, and the loop wiring ledger shows that the spatial coordinates corresponding to this loop slot number are 420 mm horizontally, 85 mm vertically, and 60 mm vertically, then these values ​​are entered into a structured field according to the cold bridge node identifier N07, with the keys being node identifier, horizontal axis coordinate, vertical axis coordinate, material code, and cross-sectional area specification, respectively.

[0030] It is understood that the structured fields are encapsulated in key-value pair format, with each cold bridge node forming an independent record. Multiple records are arranged in ascending order according to the cold bridge node identifier, constituting a cold bridge node feature dataset. The cold bridge node feature dataset is stored in text format in the storage area of ​​the distribution box monitoring main control unit, for subsequent use in the temperature and humidity monitoring and heating control of the cold bridge nodes by identifier index.

[0031] S102. Based on the spatial location of the cold bridge node feature dataset, attach temperature probes to the surface of the corresponding outgoing terminals, and deploy temperature and humidity probes inside the distribution box that avoids the heating zone of the circuit breaker. Simultaneously acquire the filtered wall temperature sequence, the air temperature inside the box, and the relative humidity time series data to generate the dew point temperature trajectory.

[0032] The spatial locations of each cold bridge node are read from the cold bridge node feature dataset. Contact temperature probes are attached to the metal surface of the branch outgoing terminals corresponding to these spatial locations. The sensing surface of the temperature probes is covered with thermally conductive silicone grease and tightly adheres to the terminal surface. A wall mounting location is selected, avoiding the heat-generating areas above and to the sides of the DIN rail circuit breaker inside the distribution box. Temperature and humidity probes are deployed at these wall mounting locations, and the initial wall temperature sequence and the box air temperature and relative humidity sequences output by the temperature probes are simultaneously collected. For the initial wall temperature sequence, the box air temperature sequence, and the relative humidity sequence, a sliding window mean filter is used to remove high-frequency noise interference. The sampling window is divided into integer multiples of the sampling period and slides periodically to obtain the filtered wall temperature sequence, the filtered air temperature sequence, and the filtered relative humidity sequence. Based on the filtered air temperature sequence and the filtered relative humidity sequence, the dew point temperature is calculated point-by-point using the Magnus formula. In the Magnus formula, the intermediate variable is obtained by multiplying a by T, dividing by b, and adding T, then adding the natural logarithm of the relative humidity percentage. The dew point temperature is then obtained by multiplying b by the intermediate variable, dividing by a, and subtracting the difference between the intermediate variables. Here, T is the filtered air temperature, a is 17.27, and b is 237.7. The dew point temperature trajectory is obtained by connecting the dew point temperature values ​​in ascending order of timestamps.

[0033] The fundamental condition for condensation to occur is that "the temperature of the metal surface is lower than the dew point temperature of the surrounding air." To determine whether this condition is met, two independent sets of data must be obtained simultaneously: the actual temperature of the metal terminal surface (collected by a contact temperature probe) and the temperature and relative humidity of the air inside the enclosure (collected by a temperature and humidity probe). The dew point temperature of the air is not a directly measured value, but needs to be calculated using the Magnus formula based on the air temperature and relative humidity. The contact temperature probe is directly attached to the metal surface of the branch line terminal and the microscopic gaps are filled with thermally conductive silicone grease. The purpose is to accurately capture the true temperature change of the metal at the cold bridge node with minimal thermal resistance. The temperature and humidity probe is deliberately installed on the inner wall of the distribution box, avoiding the heat-generating areas above and to the sides of the DIN rail circuit breaker. This is because the circuit breaker generates localized thermal convection during operation. If the temperature and humidity probe is installed close to it, the measured air temperature will be too high and the relative humidity will be too low, resulting in an inflated dew point temperature and causing misjudgment or missed condensation detection. By deploying temperature and humidity probes in wall mounting locations away from heat sources, air parameters that represent the overall environmental conditions inside the enclosure can be collected.

[0034] In one embodiment, the contact temperature probe is a platinum resistance temperature sensor. The probe's sensing surface is a circular metal sheet with a diameter of 5 mm to 8 mm, covered with thermally conductive silicone grease of approximately 0.3 mm thickness, and then tightly attached to the exposed metal surface of the branch line terminal. It is secured with high-temperature resistant tape or elastic clips to prevent the sensing surface from detaching due to terminal heating or enclosure vibration during operation. The probe's lead wires run along the back plate of the guide rail, through a pre-drilled wire hole, and are led to the main control unit of the distribution box. They are then connected to the analog acquisition port of the main control unit, converted into digital temperature values, and stored in the data buffer of the main control unit according to a timestamp.

[0035] Specifically, avoiding the heating zones above and to the sides of the DIN rail circuit breaker inside the distribution box refers to the fact that under rated operating conditions, the circuit breaker's casing temperature can rise above 45 degrees Celsius, forming upward heat dissipation plumes and lateral convective hot air masses. If temperature and humidity probes are placed in this area, the collected air temperature will be significantly higher, leading to inaccurate dew point temperature readings. Referring to the characteristic that the heat dissipation plume has a significant impact within 150 mm of the circuit breaker casing and its impact diminishes beyond 150 mm, the temperature and humidity probes should be deployed in the lower part of the distribution box or on the side wall away from the circuit breaker, maintaining a horizontal distance of at least 150 mm from the circuit breaker casing.

[0036] It should be noted that the temperature and humidity probe integrates a temperature-sensitive element and a capacitive humidity-sensitive element, outputting two signals: the air temperature sequence and the relative humidity sequence inside the chamber. The sampling frequency is consistent with that of the temperature probe, both being synchronously triggered every 30 seconds. The acquired data points have a unified timestamp, and the three time-series data correspond one-to-one on the time axis.

[0037] In one possible implementation, the initial wall temperature sequence reflects the actual temperature change of the terminal metal surface at the cold bridge node, the box air temperature sequence reflects the ambient air temperature inside the distribution box, and the relative humidity sequence reflects the water vapor content level inside the box. During the acquisition process, the three time-series data are susceptible to interference from airflow disturbances caused by fan start-stop, electromagnetic pulses caused by circuit breaker opening and closing, and voltage jumps caused by poor contact of the probe leads, resulting in glitch jump points.

[0038] Preferably, a sliding window mean filter is used to process the above three time-series data.

[0039] For example, the sampling period is 30 seconds, and the sliding window is 10 times the sampling period, i.e., 300 seconds, corresponding to 10 sampling data points within the window. Each filtering operation takes the average of the data from the current time point and the previous 9 time points as the filtered output for that time point. The sliding window moves forward successively by one sampling period to obtain the filtered wall temperature sequence, the filtered air temperature sequence, and the filtered relative humidity sequence, thereby eliminating high-frequency glitches and instantaneous jumps.

[0040] Specifically, the Magnus formula is an empirical formula widely used in meteorology to calculate dew point temperature based on air temperature and relative humidity. Dew point temperature is the temperature value corresponding to air cooling to saturation under constant water vapor partial pressure. In anti-condensation systems for electrical distribution boxes, when the terminal surface temperature is lower than the dew point temperature, water vapor in the air will condense on the terminal metal surface to form a liquid water film.

[0041] In one embodiment, the dew point temperature calculation process based on the Magnus empirical formula is implemented as follows: First, the temperature value T corresponding to each time stamp is extracted point by point from the filtered air temperature sequence, and then substituted into the expression. In the formula, constants a and b are taken as 17.27 and 237.7 respectively, both of which are empirical constants in the Magnus formula corresponding to the saturated water vapor pressure curve at the water surface. Secondly, the relative humidity values ​​RH (RH for Relative Humidity, representing the ratio of the actual partial pressure of water vapor in the air to the saturated water vapor pressure at the same temperature, usually expressed as a percentage, intuitively reflecting the degree to which the air is far from water vapor saturation) are extracted from the filtered relative humidity sequence. Take the natural logarithm as The term. Then, the two terms above are added together to obtain the intermediate variable α, i.e. Through algebraic transformations The dew point temperature Td at that time point is calculated. The above calculation is performed synchronously point by point according to the timestamp, traversing all time points of the filtered air temperature sequence and the filtered relative humidity sequence, generating a dew point temperature time sequence of the same length as the input sequence. The basic physical principle of this implementation logic is that the dew point temperature is the critical temperature at which air is cooled to saturation (i.e., relative humidity reaches 100%) under the condition of constant air pressure and water vapor content.

[0042] For example, if the filtered air temperature is 20 degrees Celsius and the filtered relative humidity is 65%, substituting these values ​​into the Magnus formula, the dew point temperature at that time is approximately 13.2 degrees Celsius.

[0043] Understandably, the dew point temperature values ​​at each time point are connected in ascending order of timestamps to form a dew point temperature trajectory that changes over time. This dew point temperature trajectory and the filtered wall temperature sequence are presented on the same time axis, providing a benchmark for subsequently determining the temperature margin between the filtered wall temperature sequence and the dew point temperature trajectory.

[0044] S103. Calculate the margin between the filtered wall temperature sequence and the dew point temperature trajectory. If the margin is lower than the preset threshold within a continuous sampling period, determine that there is a risk of condensation at the cold bridge node of the distribution box and generate a heating trigger command.

[0045] The filtered wall temperature sequence and the dew point temperature trajectory are obtained, and the difference is calculated point by point at the same timestamp to obtain a temperature margin sequence between the filtered wall temperature value and the dew point temperature value at each time point. The temperature margin sequence reflects the margin level of the surface temperature of the cold bridge node above the dew point temperature trajectory. The temperature margin value within a continuous sampling period is read from the temperature margin sequence and compared point by point with a preset threshold. If the temperature margin value within a continuous sampling period is lower than the preset threshold, it is determined that the cold bridge node has a risk of condensation, and a heating trigger command is output to the heating control port of the main control unit of the distribution box.

[0046] In one embodiment, the temperature margin sequence is formed by subtracting the dew point temperature value at the same time point from the temperature value at each time point in the filtered wall temperature sequence; the difference is the temperature margin value at that time point. The temperature margin value reflects the margin level between the surface temperature of the cold bridge node and the dew point temperature. A larger value indicates that the cold bridge node is further from the condensation state; a smaller value indicates that the cold bridge node is closer to the critical condensation state and closer to the preset threshold. The temperature margin values ​​at each time point are connected in ascending order of timestamp to form the temperature margin sequence.

[0047] Specifically, the preset threshold is set according to the safety margin of the anti-condensation service of the distribution box.

[0048] An example value of 2 degrees Celsius is used. This value is chosen because when the temperature margin is less than 2 degrees Celsius, slight fluctuations in the air temperature or relative humidity inside the chamber can cause the terminal surface temperature to reach the dew point, creating a risk of condensation.

[0049] Preferably, the determination length of the continuous sampling period is set to 5 sampling periods, corresponding to the aforementioned 30-second sampling period, forming a 150-second time window. The temperature margin values ​​within the latest 5 sampling periods of the temperature margin sequence are compared point-by-point with the preset threshold. If all 5 values ​​are lower than the preset threshold, the cold bridge node is determined to have a condensation risk; if any value is higher than or equal to the preset threshold, the cold bridge node is determined not to have a condensation risk, and heating is not triggered. This determination method will not cause false triggering in situations where instantaneous air disturbances or electromagnetic interference cause short-term fluctuations in the temperature margin.

[0050] It is understandable that once it is determined that there is a risk of condensation at the cold bridge node, a heating trigger command is output to the heating control port of the main control unit of the distribution box. The heating trigger command carries the corresponding cold bridge node identifier and trigger timestamp, which can be used by the calling link of the corresponding target heating unit according to the identifier index.

[0051] S104. Responding to the heating trigger command, the core material code in the cold bridge node feature dataset is parsed and the thermal conductivity is obtained from the physical property parameter library. Combined with the nominal cross-sectional area specification, the preset relationship table between the thermal resistance of the conductor and the distance is queried. The target heating distance that meets the thermal balance constraint is obtained with the terminal surface steady-state temperature being higher than the dew point temperature trajectory and the axial heat loss being controlled as constraints.

[0052] In response to the heating trigger command, the core material code and nominal cross-sectional area specification of the corresponding cold bridge node are parsed from the cold bridge node feature dataset. Using the core material code as an index key, the corresponding thermal conductivity parameter value is retrieved from a preset physical property parameter library. This library records the thermal conductivity values ​​of copper and aluminum cores, as well as the equivalent thermal conductivity values ​​of the insulation sheath. This yields the core thermal conductivity and equivalent insulation thermal conductivity of the branch conductor corresponding to the cold bridge node. Based on the nominal cross-sectional area specification, a preset conductor thermal resistance and distance relationship table is queried. This table uses the nominal cross-sectional area specification as the row index and the distance along the conductor axial direction as the column index. Each table cell stores the equivalent thermal resistance value of the corresponding cross-sectional area specification at the corresponding axial distance. All thermal resistance values ​​for the row corresponding to the current nominal cross-sectional area specification are read to obtain the thermal resistance profile distributed along the axial direction of the branch conductor. The temperature margin constraint is set by taking the steady-state temperature of the terminal surface as higher than the dew point temperature trajectory, and the axial heat loss constraint is set by taking the axial heat loss transmitted along the branch line to the outside of the distribution box as lower than the preset heat loss upper limit. The preset heat loss upper limit is set according to the preset ratio of the rated power of the heating unit. The axial distance value is obtained by traversing the thermal resistance profile using a binary search algorithm. Combined with the thermal conductivity of the wire core and the equivalent thermal conductivity of the outer sheath, the steady-state temperature value of the terminal surface and the axial heat loss value are calculated by substituting each axial distance value into the steady-state heat conduction equation. If both the temperature margin constraint and the axial heat loss constraint are satisfied, the corresponding axial distance value is determined as the target heating distance that satisfies the thermal balance constraint.

[0053] In one embodiment, after receiving the heating trigger command, the main control unit of the distribution box monitors retrieves the corresponding record from the cold bridge node feature dataset according to the cold bridge node identifier carried in the command, and reads the core material code field and nominal cross-sectional area specification field in the record as the index basis for subsequent physical property parameter query and thermal resistance profile query.

[0054] Specifically, the physical property parameter library is a pre-established key-value pair storage structure, where the key is the core material code and the value is the thermal conductivity parameter value.

[0055] For example, the thermal conductivity of the conductor corresponding to material code Cu is 398 W / m / Kelvin, and the thermal conductivity of the conductor corresponding to material code Al is 237 W / m / Kelvin. The physical property parameter library also independently records the equivalent thermal conductivity of the PVC insulation sheath as 0.17 W / m / Kelvin, for subsequent calculation of radial heat dissipation of the conductor. Substituting the obtained conductor material code into the physical property parameter library yields the conductor core thermal conductivity and the equivalent thermal conductivity of the sheath of the branch conductor corresponding to the cold bridge node.

[0056] It should be noted that the thermal conductivity of the wire core reflects the ability of the wire core metal to conduct heat along the axial direction, while the equivalent thermal conductivity of the outer sheath reflects the ability of the insulation outer sheath to prevent heat from diffusing outward along the radial direction. Together, they determine the path of the heating heat from the heating unit to the terminal surface and then dissipates outward from the distribution box.

[0057] In one possible implementation, the table showing the relationship between conductor thermal resistance and distance establishes a row index for each standard cross-sectional area specification appearing in the distribution box circuit list, including ranges of 1.5, 2.5, 4, 6, 10, 16, 25, 35, and 50 square millimeters; a column index is established along the axial distance nodes of the conductor with a step size of 5 millimeters, covering the range from 0 millimeters to 300 millimeters. Each table cell stores the equivalent thermal resistance value of the corresponding cross-sectional area specification at the corresponding axial distance node. The equivalent thermal resistance value is calculated in advance based on the geometric dimensions of the conductor cross-section, the thickness of the outer sheath, and the thermal conductivity of the conductor and the outer sheath according to a series thermal resistance network, reflecting the cumulative amount of thermal resistance experienced from the heating point along the conductor to the node at that axial distance.

[0058] Specifically, based on the nominal cross-sectional area specification, the corresponding row is located from the table of thermal resistance and distance relationship of the conductor. The equivalent thermal resistance values ​​at all axial distance nodes are read sequentially from 0 mm according to the column index, forming a thermal resistance profile along the axial direction of the branch conductor. The thermal resistance profile is a one-dimensional array, with array elements arranged in ascending order of axial distance. Each element records the cumulative thermal resistance value at that axial distance.

[0059] Preferably, the difference between adjacent elements in the thermal resistance profile reflects the unit thermal resistance over that small distance segment, and is used for segmented heat flow estimation when calculating axial heat flow in the subsequent calculation.

[0060] In one embodiment, the steady-state heat conduction equation is written in a one-dimensional axial model of the branch outlet conductor as follows: Where Ts represents the steady-state temperature of the terminal surface in degrees Celsius, Th represents the heating temperature at the heating point in degrees Celsius, q represents the heat flow along the conductor axis from the heating point to the terminal surface in watts, and R represents the cumulative thermal resistance from the heating point to the terminal surface in Kelvin per watt. R is read from the table of conductor thermal resistance and distance relationship according to the axial distance between the heating point and the terminal. This table is the thermal resistance profile mentioned above; the two are different names for the same data. The heat flow q is determined by the rated power P of the target heating unit and the current splitting coefficient. Multiplying them together yields the result, i.e. The same η value is used synchronously to measure the axial heat loss transmitted along the branch line conductors to the outside of the distribution box. The calculation, where The axial heat loss value is represented by P, the rated power value of the target heating unit is represented by η, and the current splitting coefficient is represented by η. The value is obtained by looking up a preset current splitting table according to the axial distance L from the heating point to the cold bridge node. The preset current splitting table is arranged in ascending order of L and descending order of η. When L is 0 mm, η is 0.9, when L is 300 mm, η is 0.1, and intermediate values ​​are linearly interpolated. Optionally, the current splitting table can be determined by first constructing an accurate conductor thermal model based on the actual geometric dimensions of the conductor, the cross-sectional area of ​​the copper core, the thickness of the insulation layer, and the thermal conductivity of the outer sheath material, and setting the heating point as a constant power heat source and the terminal surface and the external environment of the distribution box as convective heat transfer boundary conditions in the model. Subsequently, using the axial distance L from the heating point to the cold bridge node as the scanning variable, heating positions were set point by point within a preset step size (e.g., 10 mm) within a range of 0 to 300 mm. Steady-state thermal field solutions were performed for each L value, and the ratio of the heat flow along the conductor axis to the outside of the distribution box under this condition to the rated power P of the heating unit was extracted; this is the shunt coefficient η for the corresponding L value. All simulation results were summarized and arranged in ascending order of L and descending order of η to form a discrete data table. Since the heat conduction process has spatial continuity in a homogeneous medium, the change in η value between adjacent discrete points is smooth and approximately linear. Therefore, intermediate L values ​​not covered in the table can be obtained through linear interpolation, ensuring engineering accuracy while avoiding storage redundancy. It is worth noting that when L is 0 mm, the heating point is adjacent to the cold bridge node, and most of the heat is directly dissipated to the outside of the box through a low thermal resistance path. The value is as high as 0.9; however, when L increases to 300 mm, the heat needs to overcome a longer axial heat conduction path and a larger radial heat dissipation area, and the proportion flowing to the outside of the box decreases significantly, with η dropping to 0.1.

[0061] Specifically, the preset heat loss limit is based on the rated power of the target heating unit. Setting, i.e. The value shall not exceed the rated power. If a node corresponds to a certain axial distance... If the value is higher than the preset heat loss upper limit, then the node does not meet the axial heat loss constraint; if the Ts value corresponding to a certain axial distance node is lower than the current dew point temperature value in the dew point temperature trajectory, then the node does not meet the temperature margin constraint.

[0062] In one possible implementation, based on Ts and Given the monotonically increasing characteristic of axial heating distance d, a binary search is employed to locate the target heating distance on the discrete set of axial distance nodes in the thermal resistance profile. The minimum axial distance node in the thermal resistance profile is set as the lower search bound dL, and the maximum axial distance node is set as the upper search bound dU. The axial distance node corresponding to the midpoint dM of these two nodes is then substituted into the steady-state heat conduction equation to calculate Ts and... The decision function executes according to the following single branch, ensuring that the criterion is monotonic on d: If Ts is lower than the current dew point temperature, it indicates that the heating length is insufficient, let The temperature contracts towards the side with the larger d; if Ts is not lower than the current dew point temperature, then record dM as the candidate target heating distance, and let... The contraction proceeds towards the smaller d to approximate the minimum d that satisfies the temperature constraint, for example, with a temperature margin of 2 to 5 degrees Celsius. The process terminates when dU and dL converge to adjacent nodes, and the candidate value from the last recorded value is read. Then check the result separately. place Whether it does not exceed the preset heat loss limit, for example, taking 1.1 to 1.2 times the heat dissipation per unit length of the pipe section as the limit; if it passes, then This is the target heating distance. If the target is not reached, it is determined that there is no feasible solution under the current operating conditions and the process is reverted to the process parameter adjustment process.

[0063] For example, if the core material code corresponding to a certain cold bridge node is Cu, the nominal cross-sectional area is 10 square millimeters, and the rated power of the heating unit is 25 watts, the initial lower bound of the binary search is 0 mm, and the upper bound is 300 mm. When the midpoint of 150 mm is selected for the first time, the linear interpolation η according to the current shunt table is approximately 0.5. The power is approximately 12.5 watts, exceeding the 7.5 watt threshold. Therefore, the search range is narrowed to the side with a larger distance, and the midpoint is taken at 225 mm. Here, η drops to approximately 0.3. While approaching 7.5 watts, the steady-state temperature of the terminal surface is still lower than the current dew point temperature. Following the rules, the distance is further reduced towards the larger distance side, taking the midpoint of 262.5 mm. After Ts satisfies the temperature margin, the distance is shifted towards the smaller distance side to approach the feasible boundary. After several iterations, the target heating distance is converged to 245 mm. At this point, the linear interpolation η according to the shunt table is approximately 0.25. It is approximately 6.2 watts, and is stably controlled within 7.5 watts. At the same time, the steady-state temperature of the terminal surface is higher than the current dew point temperature.

[0064] It is understood that the target heating distance is the axial offset distance of the heating point on the branch outgoing conductor relative to the cold bridge node, reflecting the position where heat is effectively accumulated on the terminal surface and dissipated to the outside of the distribution box.

[0065] Another way to determine the target heating distance is to anchor the spatial location of the cold bridge node and establish a heat transfer path along the direction of the outgoing conductor extending outward from the distribution box. The heat transfer path is divided into continuous thermal resistance sections. The heat transfer range is tracked when the steady-state temperature of the terminal surface is higher than the dew point temperature. The boundary of the section before the axial heat loss begins to fail to meet the control requirements is marked as the target heating distance.

[0066] Starting from the spatial location of the cold bridge node, a one-dimensional heat transfer path is established along the branch line conductor extending outwards towards the outlet hole of the distribution box. The direction of the heat transfer path is determined according to the actual routing direction of the outgoing conductor. The starting end of the path is anchored on the surface of the cold bridge node, and the ending end of the path points towards the load line outside the outlet hole of the distribution box, thus obtaining a heat transfer path with a clear starting point and extension direction. According to the distance nodes preset along the axial distance in the table of conductor thermal resistance and distance, the heat transfer path is sequentially divided into multiple consecutive thermal resistance segments according to the distance nodes. Each thermal resistance segment corresponds to a conductor segment between the distance nodes and is bound with a corresponding equivalent thermal resistance value, resulting in a continuous sequence of thermal resistance segments arranged along the heat transfer path. Starting from the initial thermal resistance section, calculate the steady-state temperature of the terminal surface at the end of the current section and the axial heat loss of the section. If the steady-state temperature of the terminal surface at the end of the current section is higher than the current dew point temperature in the dew point temperature trajectory and the axial heat loss of the current section is lower than the preset heat loss upper limit, then the end of the current section is included in the heat transfer range and tracked to the next section. If the axial heat loss of the next section is higher than the preset heat loss upper limit, then the axial position of the end of the current section is marked as the target heating distance.

[0067] In one embodiment, the spatial location of the cold bridge node is derived from the spatial coordinate field in the cold bridge node feature dataset, which includes three components: horizontal axis coordinate, vertical axis coordinate, and vertical axis coordinate. The anchoring operation uses the center of the surface wiring hole of the cold bridge node as the starting point of the heat transfer path in the three-dimensional coordinate system of the distribution box. The extension direction of the heat transfer path is determined according to the actual routing direction of the branch line conductor starting from the circuit breaker terminal, passing through the side wall or bottom wiring hole of the distribution box, and extending to the load line outside the distribution box.

[0068] Specifically, branch line conductors typically have three routing configurations within the distribution box: First, they run straight down the back of the guide rail, extending outwards through the bottom outlet hole; second, they run laterally along the cable tray, extending outwards through the side wall outlet hole; and third, they extend outwards through the top outlet hole after being protected by a flexible conduit. While the heat transfer paths corresponding to these three routing configurations differ, they can all be unfolded into a one-dimensional path along the conductor's centerline. The heat transfer path can be denoted as the distance parameter axis that passes sequentially along the conductor's centerline from the starting point, where the distance parameter is 0, increasing towards the outlet hole of the distribution box.

[0069] It should be noted that the physical meaning of a one-dimensional heat transfer path lies in treating the conductor along the axial direction as a one-dimensional heat conduction medium, ignoring the non-uniform temperature distribution within the radial cross-section of the conductor, and focusing only on temperature attenuation and heat flow transfer along the axial direction. This heat transfer path provides a spatial reference for subsequent segmentation of thermal resistance zones based on distance nodes and for segment-by-segment tracking of steady-state temperature and axial heat loss.

[0070] In one possible implementation, the distance nodes in the wire thermal resistance and distance relationship table are preset along the axial distance in 5 mm increments, covering a distance range from 0 mm to 300 mm, forming a total of 61 distance nodes. The heat transfer path is then divided into 60 thermal resistance segments according to the distance nodes, with each thermal resistance segment having two adjacent distance nodes at its two ends.

[0071] For example, the first thermal resistance segment corresponds to a distance of 0 mm to 5 mm on the parameter axis, the second thermal resistance segment corresponds to a distance of 5 mm to 10 mm on the parameter axis, and so on up to the 60th thermal resistance segment, which corresponds to a distance of 295 mm to 300 mm on the parameter axis.

[0072] Specifically, the equivalent thermal resistance value bound to each thermal resistance segment is directly derived from the equivalent thermal resistance difference between adjacent distance nodes in the row corresponding to the current nominal cross-sectional area specification in the table of conductor thermal resistance and distance, reflecting the cumulative increase in thermal resistance along the axial series on this 5 mm segment. All thermal resistance segments are arranged in ascending order of distance parameters to form a continuous thermal resistance segment sequence, with the sequence elements corresponding sequentially to each conductor segment extending from the cold bridge node towards the outlet hole of the distribution box.

[0073] Preferably, if the heat transfer path length is shorter than 300 mm in actual application, the thermal resistance segment sequence within the corresponding length range is selected for subsequent tracking; if it is longer than 300 mm, the thermal resistance segment sequence is extended backward, and the extended part uses the unit thermal resistance value corresponding to the last distance node as the equivalent thermal resistance value for each 5 mm segment.

[0074] In one embodiment, the segment-by-segment tracking process proceeds sequentially forward along a continuous sequence of thermal resistance segments, starting from the initial thermal resistance segment. The thermal resistance profile is assembled from the aforementioned thermal resistance segment sequence during the offline phase. Using the axial distance L corresponding to the end node as an index, the thermal resistance of each segment is accumulated segment by segment, forming a cumulative thermal resistance curve Rk in Kelvin per watt, starting from the cold bridge node, corresponding one-to-one with the thermal resistance segment sequence. Taking the k-th thermal resistance segment as an example, first, the cumulative thermal resistance value Rk from the cold bridge node to the end node of the k-th thermal resistance segment is read from the thermal resistance profile, and then... Calculate the steady-state temperature Tsk of the terminal surface corresponding to the end node. Where Th is obtained from the measured temperature of the heating point of the target heating unit; qk is the heat flow transferred axially to the end node, in watts, calculated by multiplying the rated power P by the axial distribution coefficient. get, This is a dimensionless proportion, reflecting the portion of P that flows out along the core axis and is not lost radially. It is obtained from a pre-calculated steady-state heat transfer simulation and decreases monotonically with L. Then, the flow splitting coefficient ηk is read from the preset flow splitting table according to the axial distance Lk corresponding to the end node, and multiplied by the rated power P of the target heating unit to obtain the axial heat loss value at the end of the k-th thermal resistance section. Compare Tsk with the current dew point temperature value Tdp in the dew point temperature trajectory, and then... Compare with the preset upper limit of heat loss. If and When the upper limit of heat loss is preset, if it is determined that the end of the kth thermal resistance segment is still within the heat transfer range that satisfies the thermal balance constraint, the tracking index is advanced to the (k+1)th thermal resistance segment and the above comparison is repeated. and When the preset heat loss limit is reached, it is determined that the end is close to the condensation risk boundary, tracking is stopped and the end is marked as a boundary node constrained by dew point; and When the value is greater than or equal to the preset heat loss limit, the axial heat loss is determined to be exceeded, tracking is stopped, and the end is marked as a boundary node constrained by heat loss; when both conditions are not met, tracking is stopped and two types of limit exceedance marks are output simultaneously.

[0075] Specifically, after stopping tracking, the axial distance value corresponding to the last node of the thermal resistance section that still satisfies the temperature margin constraint and the axial heat loss constraint is read, and this axial distance value is marked as the target heating distance.

[0076] For example, if the core material code corresponding to a certain cold bridge node is Cu, the nominal cross-sectional area is 10 square millimeters, and the rated power of the heating unit is 25 watts, when the axial distance corresponding to the end node of the 9th thermal resistance section is 45 millimeters, the steady-state temperature of the terminal surface is still higher than the current dew point temperature, and the axial heat loss is still lower than the preset heat loss limit of 7.5 watts; when the tracking progresses to the 10th thermal resistance section, the axial heat loss rises to 7.8 watts, exceeding the preset heat loss limit, the tracking stops, and the 45 millimeters corresponding to the end of the 9th thermal resistance section is marked as the target heating distance.

[0077] It is understood that the target heating distance reflects both the farthest position where the steady-state temperature of the terminal surface can still be higher than the dew point temperature trajectory when the heat flow along the conductor is transferred to the terminal surface, and the position boundary where the axial heat loss along the conductor towards the outside of the distribution box is still within the controlled range.

[0078] S105. Obtain the three-dimensional installation coordinate set of each heating element on the back panel of the distribution box, traverse and calculate the Euclidean distance between the coordinates of each element and the spatial position of the cold bridge node to determine the target heating unit, read its rated power, analyze its initial input heat energy in combination with the target heating distance, evaluate the heat loss along the outgoing conductor to the outside of the box based on the thermal conductivity of the wire core, compensate for the heat loss on the initial input heat energy, and determine the target input heat energy.

[0079] The three-dimensional installation coordinate set of each heating element is read from the heating element register deployed on the back panel of the distribution box. The three-dimensional installation coordinate set includes the horizontal, vertical, and longitudinal axis components of each heating element in the three-dimensional coordinate system within the distribution box. The Euclidean distance values ​​between the three-dimensional coordinates of each heating element and the spatial position of the cold bridge node are traversed in the three-dimensional installation coordinate set. The heating element with the smallest Euclidean distance value is determined as the target heating unit. The rated power value of the target heating unit is read from the heating element register. Based on the rated power value of the target heating unit and the target heating distance, the initial input heat energy value is obtained by multiplying the temperature rise required for the terminal surface to rise from the current wall temperature to the target steady-state temperature above the dew point temperature trajectory, the specific heat capacity and mass of the conductor segment within the target heating distance range, and the product of these three factors. The initial input heat energy value reflects the heat required for the terminal surface to rise to meet the temperature margin constraint, ignoring the heat loss along the conductor to the outside of the distribution box. Based on the thermal conductivity of the wire core and the target heating distance, the corresponding shunt coefficient value is read from the preset shunt table according to the target heating distance index. The heat loss along the branch line conductor to the outside of the distribution box is obtained by multiplying the shunt coefficient value and the rated power value. The heat loss value is added to the initial input heat energy value as a compensation amount to obtain the target input heat energy value.

[0080] In one embodiment, the heating elements deployed on the back panel of the distribution box are PTC ceramic heating elements or silicone heating strips, all fixed to the surface of the back panel at pre-planned positions, covering the key anti-condensation areas below the DIN rail circuit breaker and on both sides of the terminal block. A heating element register is established during the distribution box commissioning phase, recording the element number, rated power value, and the horizontal, vertical, and axial components of each heating element in the three-dimensional coordinate system within the distribution box, forming a three-dimensional installation coordinate set.

[0081] Specifically, the three-dimensional coordinate system inside the distribution box is consistent with the coordinate system of the aforementioned cold bridge node spatial coordinates, both with the lower left corner of the distribution box as the origin, the horizontal axis along the length of the guide rail, the vertical axis along the spacing between the guide rail rows, and the vertical axis along the depth of the box. Each record in the heating element ledger is in the form of element number H01, rated power 25 watts, horizontal axis coordinate 400 mm, vertical axis coordinate 80 mm, and vertical axis coordinate 50 mm. Multiple records are arranged in ascending order by element number.

[0082] It should be noted that the Euclidean distance value is obtained in the form of standard three-dimensional spatial distance, that is, the difference between the corresponding components of the three-dimensional coordinates of the target cold bridge node and the three-dimensional coordinates of the current heating element, the square, the sum, and the square root are taken to obtain the value of the straight-line spatial distance between the current heating element and the cold bridge node.

[0083] In one possible implementation, all heating element records in the heating element ledger are traversed, and the Euclidean distance between each record and the spatial location of the cold bridge node is calculated, forming a sequence of Euclidean distance values ​​arranged by element number. The element record with the smallest Euclidean distance value is selected from the sequence, and the heating element corresponding to this element record is determined as the target heating unit. At the same time, the rated power value in this element record is read for later use.

[0084] Preferably, if there are two or more heating elements with the same and smallest Euclidean distance values ​​in the Euclidean distance value sequence, the element with the earlier number is selected as the target heating unit in ascending order of element number to avoid ambiguity in selection.

[0085] Specifically, the initial input heat energy is calculated based on the heating heat of the conductor segment within the target heating distance range. Here, the heat required to heat the terminal surface is approximately equal to the heating heat of that conductor segment, reflecting the approximate thermal balance relationship between the terminal and the metal core of that conductor segment. The conductor segment within the target heating distance range refers to the section of conductor extending from the cold bridge node along the branch line outgoing conductor towards the outlet hole of the distribution box to the target heating distance, with its length equal to the target heating distance. The specific heat capacity and mass of this conductor segment are taken. The specific heat capacity is read from the specific heat capacity field independently recorded in the physical property parameter library according to the core material code. The specific heat capacity corresponding to copper core is 385 joules per kilogram per Kelvin, and the specific heat capacity corresponding to aluminum core is 900 joules per kilogram per Kelvin. The mass is obtained by multiplying the volume of the conductor segment by the core density, and the volume is obtained by multiplying the nominal cross-sectional area by the target heating distance. Take the temperature rise required for the terminal surface to rise from the current filtered wall surface temperature to the target steady-state temperature above the dew point temperature trajectory. , will increase temperature value The initial input thermal energy is obtained by multiplying the specific heat capacity (c) and the mass (m). This reflects the approximate value of the heat required for the terminal surface to heat up to meet the temperature margin constraint, assuming that heat loss along the conductor to the outside of the distribution box is ignored.

[0086] In one embodiment, the heat loss value reflects that while heating heat accumulates on the terminal surface, a portion of the heat is continuously conducted along the branch line conductor core towards the outlet hole of the distribution box and dissipated at the low-temperature load line side. The corresponding shunt coefficient value is read from a preset shunt table using the target heating distance as an index. Multiply the value of the rated power P of the target heating unit by the value of the heat loss, and then calculate the value of the heat loss based on the expected duration t of the target heating unit's operation. The value of t is determined by the trigger timestamp carried in the heating trigger command and the preset default heating duration. The preset default heating duration is set as an integer multiple of the continuous sampling period determination length.

[0087] For example, take 60 seconds.

[0088] Specifically, the heat loss value Qloss is superimposed on the initial input heat energy value Q0 as a compensation amount to obtain the target input heat energy value. This reflects the total heat required to raise the terminal surface temperature to meet the temperature margin constraint under the actual condition of continuous heat loss along the conductor axis.

[0089] For example, the rated power of the target heating unit corresponding to a certain cold bridge node is 25 watts, the target heating distance is 45 mm, the core material code is Cu, and the nominal cross-sectional area is 10 square millimeters. The calculated mass of this conductor segment is approximately 4 grams, the temperature rise is 3 degrees Celsius, and the initial input heat energy is approximately 4.6 joules. Multiplying the current shunting coefficient of 0.3 by the preset default heating time of 60 seconds, the heat loss is approximately 450 joules. Adding the two together, the target input heat energy is approximately 454.6 joules.

[0090] It is understandable that the target input thermal energy value is the energy benchmark for determining the duty cycle and input duration when the target heating unit is driven by the digital pulse width modulation signal. It directly reflects the total heat required by the current cold bridge node after compensation under the premise of satisfying the thermal balance constraint.

[0091] S106. Based on the target input thermal energy and the rated power of the target heating unit, divide the time slices according to a fixed modulation period, generate a digital pulse width modulation signal, and output it to the target heating unit through the drive circuit to implement anti-condensation heating for the cold bridge node of the distribution box.

[0092] The total on-time of the target heating unit is determined based on the ratio of the target input heat energy to the rated power of the target heating unit. A pre-set fixed modulation period is used as the time slice division unit. The total on-time is divided into several continuous time slices according to the fixed modulation period. The duty cycle of each time slice is determined by the ratio of the target input heat energy component corresponding to the current time slice to the product of the fixed modulation period and the rated power, thereby determining the on-off allocation ratio and forming a time slice sequence. Based on the duty cycle of each time slice in the time slice sequence, the product of the fixed modulation period and the duty cycle is used as the high-level duration of that time slice, and the difference between the fixed modulation period and the high-level duration is used as the low-level duration of that time slice. The high and low levels in each time slice are sequentially spliced ​​to form a digital pulse width modulation signal, which is then sent to the signal input terminal of the drive circuit. The driving circuit controls the on / off state of the internal power switching device according to the high and low level states of the digital pulse width modulation signal, and loads the DC bus power supply of the distribution box to the power terminal of the target heating unit according to the on / off rhythm of the digital pulse width modulation signal. The target heating unit continuously releases heating heat in the vicinity of the cold bridge node according to the received on / off current, and implements dynamic anti-condensation heating of the cold bridge node of the distribution box based on thermal balance constraints.

[0093] In one embodiment, the total conduction time is obtained by dividing the target input thermal energy value Qtarget by the rated power value P of the target heating unit, reflecting the equivalent duration required to release the entire target input thermal energy value under full load conditions at rated power. For example, for a cold bridge node with a target input thermal energy value of 454.6 joules and a rated power value of 25 watt-hours, the total conduction time is approximately 18.2 seconds.

[0094] Specifically, the fixed modulation period is a pre-set time slice division unit.

[0095] For example, a value of 1 second is used, meaning that each time slice is 1 second long. The total conduction duration is expanded on the time axis according to a fixed modulation period, covering a modulation segment of approximately 18.2 seconds on the time axis. This is divided into 18 complete time slices and 1 residual time slice. Each complete time slice is 1 second long, and the residual time slice is 0.2 seconds long. The segmentation result reflects the division of the modulation segment on the time axis rather than the conduction duration within each time slice.

[0096] It should be noted that the duty cycle value reflects the proportion of the time that the target heating unit is in the conducting state within each time slice to the total length of that time slice.

[0097] In one possible implementation, the total conduction duration is distributed uniformly across the time-slot sequence. The target input thermal energy component in each time-slot is equal to the target input thermal energy value divided by the total number of time-slots. The duty cycle value is obtained by dividing the target input thermal energy component corresponding to the current time-slot by the product of the fixed modulation period and the rated power, and the value ranges from 0 to 1.

[0098] Preferably, if the duty cycle of a time slice exceeds 1, the excess portion (d-1) is sequentially added to the adjacent subsequent time slices, where d is the duty cycle of the current time slice. If the accumulated capacity in the next time slice still exceeds 1, the process continues, forming a chain-like backfill. When there is still remaining capacity in the last time slice, the process rewinds to the previous unsaturated time slices and distributes the remaining capacity according to the ratio of 1-d. If all time slices reach the saturation limit of 1, the current modulation cycle is considered overloaded, triggering a limiting alarm and truncating and discarding the remaining capacity to avoid infinite recursion. The maximum cascading depth is set to 5 adjacent time slices; exceeding this limit results in direct truncation. If the duty cycle of a time slice is less than 0.05, the time slice is merged into the adjacent next time slice. The duration of the merged new time slice is the sum of the durations of the two time slices, and the duty cycle is weighted according to the duration, i.e., the duration of the new time slice. Where d1 and t1 are the duty cycle and duration of the short pulse time slice, and d2 and t2 are the corresponding values ​​of the next time slice, to ensure the conservation of driving energy before and after merging; if the time slice to be merged is the last slice, it is changed to be merged into the previous time slice, and the recalculation method is the same, to avoid switching jitter caused by excessively short pulses.

[0099] Specifically, the formation process of the digital pulse width modulation signal is as follows: for the current time slice, its duty cycle is multiplied by a fixed modulation period to obtain the duration of the high level in the time slice; the duration of the high level is subtracted from the fixed modulation period to obtain the duration of the low level in the time slice; first, the high-level signal within the duration of the high level is output, and then the low-level signal within the duration of the low level is output; the high and low level segments of each time slice are sequentially spliced ​​together according to the time slice number to form a digital pulse width modulation signal that is continuously output over time.

[0100] For example, when the duty cycle of a certain time slice is 0.6, a high-level signal for 0.6 seconds is output first, followed by a low-level signal for 0.4 seconds, forming a complete modulation pulse within that time slice.

[0101] In one embodiment, the driving circuit comprises a two-stage structure: an optocoupler isolation stage and a power switching stage. The optocoupler isolation stage is used to electrically isolate the low-voltage digital pulse width modulation signal output by the monitoring main control unit from the DC bus power supply of the downstream distribution box, preventing transient interference from switching back to the monitoring main control unit. The power switching stage uses a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor as the power switching device, and its gate is driven by the output signal of the optocoupler isolation stage.

[0102] Specifically, when the digital pulse width modulation signal is in a high-level state, the optocoupler isolation stage is turned on and drives the gate of the power switching device, causing the power switching device to switch from off to on, connecting the DC bus power supply of the distribution box to the power terminal of the target heating unit; when the digital pulse width modulation signal is in a low-level state, the optocoupler isolation stage is turned off, the gate of the power switching device is de-energized and switches from on to off, cutting off the path between the power terminal of the target heating unit and the DC bus power supply.

[0103] In one possible implementation, the target heating unit uses a PTC ceramic heating element or a silicone heating strip. Its internal resistive elements cyclically generate and dissipate heat according to the received on / off current, continuously releasing heat in the area adjacent to the cold bridge node. The heat reaches the surface of the cold bridge node via air convection between the backplate and the cold bridge node, and through the heat conduction path of the backplate, raising the surface temperature of the corresponding branch terminal of the cold bridge node. The heat transfer path does not pass through the heating area of ​​the DIN rail circuit breaker, avoiding conflict with the aforementioned temperature and humidity probe deployment area.

[0104] It is understandable that as each time slice in the time slice sequence is output sequentially according to the time slice number, the surface temperature of the cold bridge node is continuously increased after compensation according to the target input heat energy value, until the steady state value of the terminal surface temperature is higher than the dew point temperature trajectory and the temperature margin constraint is maintained, thereby realizing dynamic anti-condensation heating based on thermal balance constraint.

[0105] The terminal surface temperature after the target heating unit is put into operation is collected and the dew point temperature trajectory is read simultaneously. The time slice when the temperature margin is lower than the preset threshold and when it reaches the preset threshold again is calibrated. Based on the target heat energy, the corresponding time slice is written with an extended on state or a cut-off state to limit axial heat loss. The formed periodic adjustment segment is connected to the digital pulse width modulation signal to make the terminal surface temperature higher than the dew point temperature trajectory and meet the thermal balance constraint.

[0106] The terminal surface temperature after the target heating unit is put into operation is collected, and the dew point temperature trajectory is read synchronously at the same timestamp. The dew point temperature value is subtracted from the terminal surface temperature value point by point to obtain the operating temperature margin sequence. From the operating temperature margin sequence, time slots where the temperature margin value is lower than a preset threshold and time slots where the temperature margin value rises back above the preset threshold are marked, forming a temperature margin deviation time slot set and a temperature margin return time slot set. According to the target input heat energy, the time slots in the temperature margin deviation time slot set are written with an extended conduction state. The high-level duration of the time slot is extended according to the duration corresponding to the remaining component after subtracting the released heat energy from the target input heat energy. The value of the remaining component is equal to the target input heat energy value minus the actual released heat during the accumulated high-level output period up to the current time slot. The time slots in the temperature margin return time slot set are written with an extended cutoff state. The low-level duration of the time slot is extended according to the dissipation duration obtained by looking up the shunt coefficient value corresponding to the current target heating distance in the preset shunt table, forming a periodic adjustment segment with alternating extended conduction and extended cutoff. The periodic adjustment segments are sequentially appended to the end of the aforementioned digital pulse width modulation signal according to the timestamp sequence to form an updated digital pulse width modulation signal containing the periodic adjustment segments. This updated signal is then output to the target heating unit via a driving circuit. The target heating unit is continuously driven according to the on / off rhythm of the updated digital pulse width modulation signal so that the terminal surface temperature is higher than the dew point temperature trajectory and the thermal balance constraint is satisfied.

[0107] In one embodiment, after the target heating unit is put into operation, the terminal surface temperature is continuously collected using the aforementioned contact temperature probe at a sampling period of 30 seconds. The collected terminal surface temperature data points are stamped with a uniform timestamp. Simultaneously, the dew point temperature value at the corresponding time point is read from the dew point temperature trajectory at the same timestamp. The difference between the two values ​​is calculated point by point to obtain the operating period temperature margin sequence, which reflects the level of the terminal surface temperature being higher than the dew point temperature margin during the heating execution phase.

[0108] Specifically, each element in the operating temperature margin sequence corresponds to a time slice of a sampling period, and the element value is equal to the difference between the terminal surface temperature value and the dew point temperature value at the same timestamp within that time slice. The preset threshold is set to 2 degrees Celsius, consistent with the aforementioned preset threshold value.

[0109] It should be noted that the temperature margin deviation time slice refers to the time slice in which the element value in the temperature margin sequence during operation is lower than the preset threshold, and the temperature margin return time slice refers to the time slice in which the element value in the previous time slice was lower than the preset threshold and the element value in the current time slice rises back to above the preset threshold.

[0110] For example, if the terminal surface temperature is only 1.5 degrees Celsius higher than the dew point temperature when heating reaches the 30th second, then this time slice is marked as a temperature margin deviation time slice; if the terminal surface temperature is again 2.3 degrees Celsius higher than the dew point temperature when heating continues to the 45th second, then this time slice is marked as a temperature margin return time slice.

[0111] In one possible implementation, for each time slot in the set of time slots where the temperature margin deviates, an extended conduction state is written. The value of the remaining component is obtained by subtracting the actual released heat Qreleased during the accumulated high-level output period up to the current time slot from the target input heat energy value Qtarget, where Qreleased is obtained by multiplying the total high-level output duration by the rated power of the target heating unit. The extended high-level duration for this time slot is equal to the remaining component value divided by the rated power value, resulting in the extended conduction duration.

[0112] Specifically, if the temperature margin deviates from the remaining component corresponding to the time slice by 10 joules and the rated power of the target heating unit is 25 watts, then the conduction duration is extended by 0.4 seconds, and the original high-level duration of the time slice is extended by 0.4 seconds to the end, forming an extended high-level segment.

[0113] Preferably, for each time slice in the set of temperature margin return time slices, an extended cutoff state is written. The extended cutoff duration is set according to the dissipation duration obtained by looking up the shunt coefficient value corresponding to the current target heating distance in the preset shunt table. The dissipation duration is obtained by linear mapping according to the shunt coefficient value, and the dissipation duration value is obtained by multiplying the shunt coefficient value by a fixed dissipation coefficient.

[0114] For example, the diversion coefficient is a dimensionless ratio, ranging from 0 to 1, reflecting the diversion intensity of the branch; the dissipation time t and the diversion coefficient k satisfy the following relationship. The coefficient 1.6 is in seconds, and the intercept 'a' is 0.02 seconds, used to match the minimum setting delay under no-load conditions. Therefore, k=0.3 corresponds to approximately t of 0.5 seconds, k=0.5 corresponds to approximately t of 0.8 seconds, and other values ​​are calculated according to the same linear relationship. The cumulative level is the surface temperature rise of the branch line conductor 50 mm from the outer wall of the distribution box. For quantitative characterization, real-time sampling is performed using a patch-type temperature sensing element; the upper threshold of the controlled range is set as follows. The temperature should not exceed 8 degrees Celsius, and the temperature rise rate between two consecutive samples should not exceed 0.5 degrees Celsius per second. The dissipation time is the waiting time required for the temperature to decay from the current ΔT back to within the upper threshold and remain stable. 1.6 is selected under rated operating conditions. The measured axial heat dissipation time constant, which decays from a peak temperature of 12 degrees Celsius to 8 degrees Celsius, is used as a reference for regression. Before commissioning, no less than three no-load and full-load heat dissipation measurements should be performed on each branch. If the deviation of the fitted slope from 1.6 exceeds 10%, the measured slope should be used to replace and the correspondence table of shunt coefficient and dissipation time should be updated synchronously.

[0115] In one embodiment, the extended on-time is appended to the end of the high-level segment of the temperature margin deviation time slice, and the extended off-time is appended to the end of the low-level segment of the temperature margin return time slice. These two appending operations are performed sequentially on the time axis according to the actual timestamp order of each time slice in the temperature margin deviation and return time slice sets, forming a periodic adjustment segment containing extended on-time and extended off-time segments. Essentially, this periodic adjustment segment embeds additional high and low level extension segments within each relevant time slice of the original digital pulse width modulation signal, resulting in a partial rewrite of the original modulation waveform.

[0116] Specifically, the periodic adjustment segments are sequentially appended to the end of the aforementioned digital pulse width modulation signal according to timestamps, forming an updated digital pulse width modulation signal containing the periodic adjustment segments. The updated digital pulse width modulation signal is then sent to the signal input terminal of the aforementioned drive circuit. The drive circuit controls the on / off state of its internal power switching devices according to the high and low levels of the updated waveform, thus applying the DC bus power supply of the distribution box to the power supply terminal of the target heating unit according to the on / off rhythm of the updated waveform.

[0117] Understandably, as the updated digital pulse width modulation signal is continuously output on the time axis, the actual heat energy input of the target heating unit is extended by adding to the conduction time according to the temperature margin deviation state during operation, and extended by adding to the cutoff time according to the temperature margin return state during operation. The terminal surface temperature value is continuously higher than the dew point temperature trajectory and the axial heat loss is kept within the controlled range, realizing dynamic anti-condensation heating closed-loop regulation based on thermal balance constraints.

[0118] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating, characterized in that, include: Obtain surface temperature images of branch line terminals in the distribution box, mark the parts with temperatures lower than the surrounding preset temperature difference as cold bridge nodes, determine spatial coordinates based on circuit number, read the core material code and nominal cross-sectional area specification of the circuit conductor, and generate a cold bridge node feature dataset. Based on the spatial location in the cold bridge node feature dataset, temperature probes are attached to the surface of the corresponding outgoing terminals, and temperature and humidity probes are deployed in areas away from the circuit breaker heating zone. The filtered wall temperature sequence, the air temperature inside the box, and the relative humidity data are acquired simultaneously to generate a dew point temperature trajectory. The residual between the filtered wall temperature sequence and the dew point temperature trajectory is calculated. If the residual is lower than the preset threshold within a continuous sampling period, it is determined that there is a risk of condensation at the cold bridge node and a heating trigger command is generated. In response to the heating trigger command, the thermal conductivity is obtained from the physical property parameter library by parsing the core material code and looking up the relationship table between the thermal resistance of the conductor and the distance by combining the nominal cross-sectional area specification. The target heating distance is obtained based on the trajectory of the steady-state temperature of the terminal surface being higher than the dew point temperature and the axial heat loss being controlled. Obtain the three-dimensional installation coordinate set of each heating element on the back panel of the distribution box, calculate the Euclidean distance between the coordinates of each element and the cold bridge node to determine the target heating unit, read the rated power of the target heating unit, and obtain the initial input heat energy in combination with the target heating distance. Evaluate the amount of heat loss along the conductor to the outside of the box based on the thermal conductivity of the conductor core, and obtain the target input heat energy after compensating for the heat loss. Based on the target input thermal energy and the rated power of the target heating unit, time slices are divided according to a fixed modulation period to generate a digital pulse width modulation signal, which is then output to the target heating unit via a drive circuit to implement anti-condensation heating for the cold bridge node.

2. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The acquisition of surface temperature images of branch line outgoing terminals within the distribution box includes: Infrared thermal imagers are used to scan the branch outlet terminals. After grayscale normalization and median filtering, the temperature distribution map of the terminal surface is obtained. The temperature pixel values ​​of the outlet terminals and the adjacent busbars and guide rail back plate areas are extracted and the difference is obtained to obtain the local temperature difference. The outlet terminals whose local temperature difference exceeds the preset temperature difference threshold are marked as cold bridge nodes. According to the circuit wiring ledger, the spatial coordinates are determined by mapping to the three-dimensional coordinate system inside the box according to the circuit number.

3. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The step of attaching a temperature probe to the surface of the corresponding outgoing terminal based on the spatial location in the cold bridge node feature dataset includes: The temperature sensing surface of the temperature probe is covered with thermally conductive silicone grease and attached to the terminal surface. Temperature and humidity probes are deployed on the wall surface, avoiding the heating area of ​​the circuit breaker. A sliding window mean filter is used to remove high-frequency noise to obtain the filtered wall temperature sequence and air temperature and relative humidity sequence. The dew point temperature value is calculated and connected in ascending order of timestamps to obtain the dew point temperature trajectory.

4. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The margin between the filtered wall temperature sequence and the dew point temperature trajectory includes: The temperature margin sequence at each time point is obtained by subtracting the values ​​at the same timestamp. The values ​​within a continuous sampling period are read from the temperature margin sequence and compared with a preset threshold. When the temperature margin values ​​within a continuous sampling period are all lower than the preset threshold, it is determined that the cold bridge node has a risk of condensation, and a heating trigger command is output to the heating control port of the monitoring main control unit.

5. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The response to the heating trigger command parses the core material code, obtains the thermal conductivity from the physical property parameter library, and consults the relationship table between conductor thermal resistance and distance based on the nominal cross-sectional area specification. The target heating distance is obtained based on the terminal surface steady-state temperature being higher than the dew point temperature trajectory and axial heat loss being controlled, including: The thermal conductivity and equivalent thermal conductivity of the insulation sheath are retrieved from the physical property parameter library according to the core material code. The thermal resistance value corresponding to the thermal resistance and distance relationship table is read according to the nominal cross-sectional area specification to obtain the thermal resistance profile along the conductor axis. The temperature margin constraint is set with the steady-state temperature of the terminal surface being higher than the dew point temperature trajectory. The axial heat loss constraint is set with the axial heat loss being lower than the heat loss upper limit set according to the preset ratio of the rated power of the heating unit. A binary search is used to traverse the axial distance value along the thermal resistance profile and substitute it into the steady-state heat conduction equation to calculate the steady-state temperature value of the terminal surface and the axial heat loss value. The axial distance value that satisfies both constraints is determined as the target heating distance.

6. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, To obtain the target heating distance, including: A one-dimensional heat transfer path is established along the outgoing conductor towards the outlet hole of the distribution box, starting from the spatial location of the cold bridge node. The heat transfer path is divided into continuous thermal resistance segments according to the distance nodes. The steady-state temperature and axial heat loss of the terminal surface at the end of each segment are calculated. The end of the segment with a steady-state temperature higher than the dew point temperature trajectory and an axial heat loss lower than the preset heat loss upper limit is included in the heat transfer range. The axial position of the next segment with an axial heat loss higher than the preset heat loss upper limit is marked as the target heating distance.

7. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The reading of the rated power of the target heating unit includes: The Euclidean distance between the three-dimensional coordinates of each heating element and the spatial position of the cold bridge node is traversed, and the heating element with the smallest Euclidean distance value is determined as the target heating unit. The rated power of the target heating unit is then read from the heating element ledger.

8. The method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 7, characterized in that, After reading the rated power of the target heating unit from the heating element register, the process includes: The initial input heat energy value is obtained by multiplying the temperature rise required for the terminal surface to rise to the target steady-state temperature above the dew point temperature trajectory with the specific heat capacity and mass of the conductor segment within the target heating distance range. The shunt coefficient is read, and the heat loss along the outgoing conductor to the outside of the distribution box is obtained by multiplying the shunt coefficient with the rated power value. The heat loss value is added to the initial input heat energy value to obtain the target input heat energy.

9. A method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The step of dividing time slices according to a fixed modulation period based on the target input thermal energy and the rated power of the target heating unit includes: The total conduction time is obtained by the ratio of the target input heat energy to the rated power. The total conduction time is divided into continuous time slices according to the fixed modulation period. The duty cycle of each time slice is determined by the ratio of the target input heat energy component of the current time slice to the product of the fixed modulation period and the rated power. The digital pulse width modulation signal is generated according to the duty cycle of each time slice and output to the target heating unit through the drive circuit to implement anti-condensation heating for the cold bridge node.

10. A method for monitoring and regulating temperature and humidity inside a distribution box and adjusting heating according to claim 1, characterized in that, The process of generating the digital pulse width modulation signal and outputting it to the target heating unit via a driving circuit includes: The terminal surface temperature of the target heating unit after it is put into operation is collected and the dew point temperature trajectory is read synchronously at the same timestamp. The terminal surface temperature value is subtracted from the dew point temperature value point by point to obtain the operating temperature margin sequence. The deviation time slices where the temperature margin is lower than the preset threshold and the return time slices where it rises back to above the preset threshold are calibrated. Periodic adjustment segments are generated and connected to the end of the digital pulse width modulation signal according to the timestamp and output by the driving circuit.

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