Cable branch box environment data acquisition method and acquisition system

Abstract

This invention provides a method and system for acquiring environmental data of a cable branch box, relating to the field of power distribution equipment status monitoring technology. The method includes: acquiring the operating current of the branch cable and the temperature inside the box; monitoring the operating current, and determining that the branch cable is in a thermal inertia cooling period when its decrease exceeds a set load drop threshold; activating the exhaust fan during the cooling period for a set pulse disturbance duration and then shutting it off to induce airflow disturbance inside the box; acquiring the transient temperature drop value inside the box during this period; comparing the transient temperature drop value with a set drying reference temperature drop value; when the transient temperature drop value is greater than the drying reference temperature drop value, and the difference between the two exceeds a set latent heat of vaporization threshold, determining that a latent condensation film exists inside and outputting an alarm signal; if the difference does not exceed the threshold, determining that the box is in a physically dry state. This invention utilizes pulsed airflow to induce a phase change in moisture, achieving objective capture of latent early condensation on the insulation surface.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment condition monitoring technology, and in particular to a method and system for acquiring environmental data from cable branch boxes. Background Technology

[0002] Cable distribution boxes are fundamental node devices in power distribution networks, enabling power distribution and physical connection. Under normal operating conditions, the branch cables carry electrical loads and generate Joule heat, causing the air temperature inside the box to rise and increasing the air's capacity to hold water vapor. When the electrical load is low or drops sharply, the cable's transmission current decreases rapidly, reducing the conductor's heating power. Due to the different physical heat capacities and thermal resistances of the insulation material and the metal cabinet, there is a physical delay in the dissipation of internal heat to the outside, thus initiating a thermodynamic cooling phase within the equipment.

[0003] During this cooling process, the local air temperature near the insulation layer surface gradually decreases, while the relative humidity continues to rise. Gaseous moisture readily undergoes a phase change at the solid-state interface, precipitating and forming an extremely thin, invisible condensation film. Due to the viscous resistance of fluid dynamics, a relatively stable laminar boundary air layer naturally adheres to the outer side of the cable insulation layer. This boundary layer objectively hinders the natural evaporation and diffusion of trace amounts of moisture into the surrounding gas phase space, causing the initial, minor thermodynamic changes of the localized invisible water film under natural conditions to be masked by the thermal capacity parameters of the larger space.

[0004] Currently, environmental data acquisition for cable distribution boxes primarily relies on deploying temperature and humidity sensors inside the box. The environmental condition is assessed by periodically reading the absolute temperature and humidity values ​​of macroscopic air masses. This acquisition mechanism objectively reflects the overall water vapor saturation evolution trend within the box, providing a basic reference for routine operation and maintenance. However, when facing early-stage microscopic moisture adhesion, the monitoring mode, which relies on passively receiving steady-state environmental parameters, focuses on acquiring spatial homogeneous characteristics. Because the evolution of macroscopic environmental parameters is relatively smooth, there is a dimensional difference between them and the precipitation nodes of hidden water films on local insulation surfaces. Therefore, it is difficult to directly capture the thermodynamic characteristic signals caused by microscopic phase transitions, resulting in certain limitations in data extraction for in-depth perception of hidden condensation states. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for acquiring environmental data of cable branch boxes, which aims to solve the technical problem that existing conventional monitoring methods mainly rely on passively extracting macroscopic static temperature and humidity parameters, making it difficult to break the laminar air boundary at the equipment interface and thus failing to effectively capture the phase change characteristics of the initial thin and hidden condensation film.

[0006] On one hand, the present invention provides a method for acquiring environmental data of a cable branch box, applied to a cable branch box environmental data acquisition system. The system includes a cable branch box, inside which an exhaust fan and a temperature sensor are installed, and branch cables are arranged through the inside of the cable branch box. The method includes the following steps: The operating current of the branch cable and the internal temperature of the box output by the temperature sensor are collected. Monitor the changes in the operating current, and when the decrease in the operating current exceeds the set load drop threshold, determine that the branch cable is in the thermal inertia cooling period; During the thermal inertia cooling period, the exhaust fan is started and operated for a set pulse disturbance duration, then turned off, thereby generating airflow disturbance inside the cable branch box; Obtain the transient temperature drop value of the chamber temperature during the airflow disturbance; Compare the transient temperature drop value with the preset drying reference temperature drop value; When the transient temperature drop value is greater than the drying reference temperature drop value, and the difference between the two exceeds the set latent heat of vaporization determination threshold, it is determined that there is a hidden condensation film inside the cable branch box, and a high-risk condensation alarm signal is output. When the transient temperature drop is less than or equal to the drying reference temperature drop, or when the difference between the two does not exceed the latent heat of vaporization determination threshold, the inside of the cable branch box is determined to be in a physically dry state.

[0007] Optionally, before comparing the transient temperature drop value with a preset drying reference temperature drop value, the method further includes the step of obtaining the drying reference temperature drop value: The relative humidity inside the cable branch box is obtained by a humidity sensor arranged inside the box. When the branch cable is not energized and the relative humidity inside the box is lower than the set deep drying threshold, the exhaust fan is started to run for the pulse disturbance duration. The difference in baseline temperature drop output by the temperature sensor during the operation of the exhaust fan is collected, and the difference in baseline temperature drop is calibrated as the drying reference temperature drop value.

[0008] Optionally, obtaining the transient temperature drop value of the chamber temperature during the airflow disturbance includes: Record the temperature before disturbance output by the temperature sensor at the moment the exhaust fan starts; From the moment the exhaust fan starts until the end of the set follow-up observation period after the exhaust fan is turned off, the temperature sequence output by the temperature sensor is continuously collected, and the lowest temperature in the temperature sequence is recorded as the temperature after disturbance. Subtracting the temperature after the disturbance from the temperature before the disturbance yields the initial temperature difference; Obtain the natural heat dissipation temperature drop slope during the thermal inertia cooling period that is not affected by the airflow disturbance, and use the natural heat dissipation temperature drop slope to multiply by the actual elapsed time from the start time of the exhaust fan to the sampling time corresponding to the lowest temperature to obtain the natural cooling compensation value. Add the initial temperature difference to the natural cooling compensation value to obtain the transient temperature drop value after deducting the natural heat dissipation factor.

[0009] Optionally, after outputting the high-risk condensation alarm signal, it also includes: The heating and dehumidifying unit configured inside the cable branch box is activated to perform a baking operation; During the baking process, the steps of starting the exhaust fan and comparing the transient temperature drop value are performed cyclically at set intervals. When the latest acquired transient temperature drop value drops to within the dry reference temperature drop value, it is determined that the hidden condensation film has been completely evaporated and discharged, and the heating dehumidifier is turned off.

[0010] Optionally, the following steps may also be included: When the increase in the operating current exceeds the set load surge threshold, the branch cable is determined to be in the Joule heat release period; During the Joule heat release period, the temperature inside the chamber is continuously monitored; When the temperature inside the box reaches the set heat dissipation start threshold, the exhaust fan is kept continuously running to expel the heat emitted by the branch cable from outside the cable branch box.

[0011] Optionally, when the branch cable includes at least one target branch cable and at least one adjacent branch cable, if the target branch cable is in the thermal inertia cooling period and the operating current of the adjacent branch cable is increasing, the operating current of the adjacent branch cable is extracted to estimate the thermal radiation power. The latent heat of vaporization determination threshold near the target branch cable is reduced by using the thermal radiation power to offset the evaporation hysteresis interference caused by the heating of adjacent cables.

[0012] Optionally, after determining that the branch cable is in the thermal inertia cooling period and before starting the exhaust fan, an external temperature immunity judgment step is also included: The ambient temperature outside the cable branch box is collected synchronously. Calculate the slope of the external temperature decrease; When the absolute value of the slope of the external ambient temperature drop is greater than the absolute value of the slope of the natural heat dissipation temperature drop inside the box, it is determined that the cable branch box is suffering from a sudden cold attack by external weather, the step of starting the exhaust fan is suspended, and an external condensation warning is output.

[0013] Optionally, during the step of shutting down the exhaust fan after a set pulse disturbance duration, the real-time operating current of the exhaust fan is simultaneously collected. When the real-time operating current deviates from the set rated no-load current of the exhaust fan and exceeds the tolerance range, it is determined that there is a physical blockage in the fan blades or exhaust channel of the exhaust fan. The step of acquiring the transient temperature drop value is terminated, and a fault code for the anti-condensation equipment is output.

[0014] Optionally, the temperature sensor includes a contact probe attached to the surface of the insulation layer of the branch cable, and a convection probe suspended near the inner wall of the cable branch box. The steps of obtaining transient temperature drop values ​​are performed independently based on the data collected by the contact probe and the convection probe, respectively. Determine whether the hidden condensation film exists on the surface of the branch cable and the inner wall of the cable branch box.

[0015] On the other hand, the present invention provides an environmental data acquisition system for cable branch boxes, including a memory and a processor; The memory contains computer programs; When the processor executes the computer program, it implements the steps in the cable branch box environmental data acquisition method as described in any of the preceding claims.

[0016] The present invention has achieved the following beneficial effects: This invention, through the linkage monitoring of branch cable operating current and box temperature, utilizes the thermal inertia cooling period induced by load drop as a dedicated data observation window to actively control the exhaust fan to output pulsed airflow of a specific duration, establishing a forced convection field within the sealed box. This forced convection breaks the laminar viscous adhesion limitations on the surface of the insulating medium, causing the hidden trace amounts of liquid moisture to vaporize and absorb the surrounding latent heat. The system analyzes and extracts the transient temperature drop value generated during the forced vaporization of moisture, and combines it with a natural heat dissipation calculation program to remove the inherent basic heat transfer attenuation component of the equipment, transforming the difficult-to-detect early microscopic condensation phenomenon into a thermodynamic cooling parameter that is easily read by the temperature sensor. This acquisition mechanism achieves proactive acquisition of the physical state of the microscopic water film precipitation process on the surface of insulating components, overcoming the limitations of relying solely on macroscopic spatial relative humidity for environmental assessment, and providing objective and direct underlying data support for the condition assessment of power distribution equipment and subsequent dehumidification intervention.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a structural diagram of the module composition of the cable branch box environmental data acquisition system in an embodiment of the present invention; Figure 2 This is the main flowchart of the cable branch box environmental data acquisition method in this embodiment of the invention; Figure 3 This is a flowchart of the external temperature immunity judgment step in an embodiment of the present invention; Figure 4 This is a flowchart of the steps for preventing blockage and obtaining transient temperature drop values ​​in an embodiment of the present invention. Detailed Implementation

[0020] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] This invention provides a method for acquiring environmental data from cable branch boxes, applicable to a cable branch box environmental data acquisition system. For example... Figure 1As shown, the cable branch box environmental data acquisition system includes a cable branch box 10, the outer shell of which encloses an internal space. Branch cables 20 are arranged inside the cable branch box 10, connecting to an external power distribution network as physical carriers for power transmission. An exhaust fan 30 is installed inside the cable branch box 10, its outlet connected to the external atmosphere via a protective structure. The exhaust fan 30 is configured to receive electrical drive signals from a control terminal and generate fluid mechanical work within the cable branch box 10 to stimulate convective airflow. Temperature sensors 40 and humidity sensors 50 are arranged at preset positions inside the cable branch box 10, configured to output electrical signals characterizing the environmental state parameters at their probe locations. The main control hardware of the cable branch box environmental data acquisition system includes a processor 60, an analog-to-digital converter circuit 70, and a memory 80. The processor 60 is electrically connected to the peripheral circuits and memory 80 via a data bus and an address bus, executing data sampling control, digital signal processing, state comparison and judgment, and electromechanical equipment action control commands. The ambient temperature is collected by the ambient temperature sensor 90. The system also includes a drive circuit 100, a current sensor 110, a heating and dehumidifying unit 120, and a current transformer 130.

[0022] like Figure 2 As shown, the environmental data acquisition method for the cable branch box includes the following steps: acquiring the operating current of the branch cable 20 and the box temperature output by the temperature sensor 40.

[0023] Specifically, for acquiring the electrical load parameters carried by the branch cable 20, the system is equipped with a current transformer 130 sleeved on the outside of the insulation sheath of the branch cable 20. The secondary winding of the current transformer 130 outputs an analog AC current signal representing the actual current transmitted by the branch cable. This analog AC current signal is low-pass filtered, converted to current and voltage, and scaled by a configured signal conditioning circuit before being input to the analog-to-digital converter circuit 70. The analog-to-digital converter circuit 70 quantizes the continuous analog voltage signal into a digital operating current sequence according to the discrete sampling period set internally by the processor 60. Simultaneously, the temperature sensor 40 senses environmental parameters in real time and outputs the corresponding analog electrical signal. This electrical signal is input to the analog-to-digital converter circuit 70 via an independent signal conditioning channel, and is converted into a digital temperature sequence inside the box. The processor 60 reads instructions to acquire the digital operating current data and digital temperature data inside the box at the same sampling clock node, and, in conjunction with the real-time clock module inside the system, adds the same timestamp to the two sets of data. The data frame with the timestamp is written into a circular data buffer queue defined inside the memory 80. Through the above data acquisition steps, the system constructs a branch cable load sequence and an internal ambient temperature evolution sequence with a time axis correspondence in the memory 80.

[0024] The changes in the operating current are monitored, and when the decrease in the operating current exceeds the set load drop threshold, it is determined that the branch cable is in the thermal inertia cooling period.

[0025] Further, the processor 60 reads the operating current sequence data from the circular data buffer queue according to the set operation cycle. The processor 60 sets a first time observation window and a second time observation window that do not overlap on the operating current sequence, with the time node of the first time observation window being earlier than that of the second time observation window. The processor 60 calculates the time average of each operating current sample value within the first time observation window and the time average of each operating current sample value within the second time observation window. The processor 60 uses a subtraction instruction to subtract the time average of the second time observation window from the time average of the first time observation window to obtain the operating current drop amplitude reflecting the current grid load fluctuation. The memory 80 pre-stores a load sag threshold, which has a corresponding mapping relationship with the rated transmission specifications and DC resistance parameters of the branch cable 20. This mapping relationship is established with the constraint of the minimum Joule heat drop required to induce a macroscopic cooling gradient on the insulation surface. The rated operating current of the branch cable is set to... The DC resistance per unit length at the reference temperature is To ensure that the heat dissipation exceeds the inherent heat capacity of the solid-phase insulating material and establishes an effective cooling source, the system is calibrated to have a minimum power drop limit. This represents 25% to 35% of the full-load heat dissipation power. Based on the equation for the difference in heat power under constant impedance, the load descent threshold mapped by the underlying processor 60 is calibrated as follows: ,in, This is the load drop threshold. This physical checkpoint cuts off the ineffective observation mechanism caused by normal load spikes in the power grid at the source of control, ensuring that the sampling window is activated only when there is real thermodynamic cooling kinetic energy.

[0026] The processor 60 compares the calculated decrease in operating current with the load drop threshold. When the comparison shows that the decrease in operating current is greater than or equal to the load drop threshold, and this data status remains valid for multiple consecutive calculation cycles, the processor 60 updates the status flag, determining that the branch cable load has decreased. Under the condition of load drop in branch cable transmission, the Joule heating power generated by the metal conductor of branch cable 20 decreases synchronously. Since the conductor material, insulation layer, and inner layer air of the cable branch box have physical heat capacity and thermal resistance, the attenuation of internal heat generation will not cause a synchronous drop in the surface temperature of the equipment and the ambient temperature inside the box. There is a physical delay in the dissipation of heat to the external environment. During this cooling process, the air temperature near the surface of the insulation layer gradually decreases, and its local relative humidity increases, forming the prerequisite for the precipitation and condensation of water molecules on the solid surface. Based on the characteristics of the operating current, the system determines that branch cable 20 is in the thermal inertia cooling period, thereby defining the data observation interval for extracting the cooling characteristics of water condensation in the time dimension, avoiding the masking of the thermodynamic signal of condensation phase change by high load heating power.

[0027] like Figure 3 As shown, after determining that the branch cable is in the thermal inertia cooling period and before starting the exhaust fan, the method includes an external temperature disturbance judgment step: synchronously collecting the external ambient temperature outside the cable branch box through the external ambient temperature sensor 90; calculating the external ambient temperature drop slope; when the absolute value of the external ambient temperature drop slope is greater than the absolute value of the natural heat dissipation temperature drop slope inside the box, it is determined that the cable branch box is suffering from an external meteorological cold attack, the step of starting the exhaust fan is suspended, and an external condensation warning is output.

[0028] Specifically, the cable distribution box 10 is installed in a naturally exposed environment, and its metal casing, acting as a heat exchange boundary, is affected by external meteorological conditions. The processor 60 acquires external ambient temperature sequence data using the same discrete sampling mechanism via an external ambient temperature sensor 90 located on the outer casing of the cable distribution box. The processor 60 uses differential calculation to obtain the slope of the external ambient temperature sequence over time. Simultaneously, based on the aforementioned internal temperature sequence, the processor 60 calculates the natural heat dissipation temperature drop slope, characterizing the rate of heat transfer from the box's interior to the exterior. The processor 60 extracts these two slope parameters and performs a comparison calculation.

[0029] Under normal heat transfer conditions, the rate of heat dissipation from inside the cable distribution box is limited by the thermal conductivity of the metal casing and the medium itself. When the absolute value of the external temperature drop slope is greater than the absolute value of the natural heat dissipation temperature drop slope, it indicates that the external environment's cooling rate exceeds the physical equilibrium heat conduction boundary of the cable distribution box 10. The surface temperature of the metal casing of the cable distribution box 10 drops rapidly, transforming into an active cold source interface for the internal environment. Considering the transient high-frequency thermal fluctuations caused by gusts of wind shear or cloud cover in the outdoor natural environment, directly differentiating the discrete sampling points can easily lead to severe fluctuations in the slope signal, thus causing misjudgments in the state machine.

[0030] Processor 60 introduces a disturbance-resistant multiplier with thermal resistance isolation in the front-end link of the slope cross-matching logic. The actual underlying triggering logic is established as follows: the absolute value of the slope of the external temperature decrease must be greater than... Multiply by the algebraic product of the absolute value of the slope of the natural heat dissipation temperature drop. This isolation multiplier. The steady-state thermal resistance parameter of the double-layer sheet metal shell of the branch box 10 is preset between 0.15 and 0.25. Simultaneously, the processor 60 requires that this inequality Boolean state must remain effectively locked for three consecutive discrete sampling clock cycles. This digital filtering and hysteresis judgment mechanism with physical delay effectively filters out false interception of the anti-condensation diagnostic program by high-frequency meteorological noise. If the exhaust fan 30 is started under this condition, the impeller of the exhaust fan 30 will introduce low-temperature external air into the box, causing a temperature rise at the location of the internal temperature sensor 40 due to a non-phase change mechanism. This temperature rise caused by the introduction of external cold source will cover the temperature difference parameter caused by the heat absorption of moisture phase change, leading to data analysis failure. When the slope comparison condition is met, the processor 60 triggers a control interception command, invalidating the control terminal level signal of the exhaust fan 30 and suspending the execution of the step to start the exhaust fan 30. The processor 60 simultaneously assembles communication data frames and outputs external condensation warning data characterizing extreme meteorological fluctuations through the communication interface.

[0031] In the absence of a control interception command, during the thermal inertia cooling period, the exhaust fan 30 is started and then shut off after a set pulse disturbance duration, thereby generating airflow disturbance inside the cable branch box 10.

[0032] Understandably, processor 60 outputs a conduction control level signal to drive circuit 100 via a pin. Drive circuit 100 connects to the power supply of exhaust fan 30, causing the rotor of exhaust fan 30 to rotate under electrical power. Simultaneously with outputting the conduction control level signal, processor 60 starts a timer module. The counting time of the timer module is set to the pulse disturbance duration pre-stored in memory 80. When the timer accumulates to the pulse disturbance duration, processor 60 performs a level toggle operation, outputting a cutoff control level signal to cut off the power supply to the exhaust fan. The exhaust fan motor decelerates and stops after losing power. (Pulse disturbance duration) The selection of the appropriate method must simultaneously satisfy the lower limit of mechanical work required to overcome the viscous resistance of the fluid in the boundary layer of the insulation layer, and avoid the upper limit of large-scale evacuation and loss of background heat within the chamber. The system is based on a space-permutation reduced-order equation. Perform calculations, among which This refers to the net internal gas phase volume of the cable branch box. The rated volumetric flow rate of the exhaust fan. The spatial permutation coefficient is determined based on the failure condition of the Reynolds number at the laminar boundary of the flow field. It is strictly locked within the range of 0.10 to 0.15. This time parameter precisely constrains the intervention boundary of forced convection, preventing the microscopic phase change cooling signal caused by prolonged exhaust ventilation from being forcibly aliased by the heat dissipation of the macroscopic environment.

[0033] Before the exhaust fan is started, the air velocity on the surface of the insulation layer of the branch cable 20 is slow, and a laminar boundary air layer with a humidity gradient exists due to the influence of fluid viscosity. If there is a hidden condensation film on the surface, this laminar boundary air layer hinders the diffusion of liquid water into the surrounding environment, limiting the natural evaporation rate of water and preventing macroscopic temperature changes. By setting the duration of the pulse disturbance of the exhaust fan 30 within this specific time interval, the exhaust fan 30 performs work on the air trapped inside the sealed box, inputting kinetic energy and establishing a forced convection flow field inside the cable branch box 10. This forced convection acts on the surface of the branch cable, replacing the original laminar boundary air layer and reducing the local water vapor partial pressure above the liquid-gas interface. The forced convection condition breaks the original gas-liquid two-phase equilibrium state, causing liquid water molecules attached to the solid phase surface to detach from the liquid phase and diffuse into the gas phase space, thereby triggering a phase change physical process of forced vaporization of water. The pulsed operation limits the total amount of airflow replacement, providing the conditions for phase change excitation while suppressing the large-scale heat loss from the inside of the chamber to the outside.

[0034] In the step of shutting down the exhaust fan 30 after the set pulse disturbance duration is started, the real-time operating current of the exhaust fan is collected synchronously through the current sensor 110; when the real-time operating current deviates from the set rated no-load current of the exhaust fan and exceeds the tolerance range, it is determined that there is physical blockage in the fan blades or exhaust channel of the exhaust fan 30; the step of obtaining the transient temperature drop value is stopped, and the anti-condensation equipment fault code is output.

[0035] Specifically, a current sensor 110 is connected in series in the power supply branch of the exhaust fan. During the exhaust fan's on-state operation, the processor 60 acquires the real-time operating current of the exhaust fan motor through the acquisition channel of the analog-to-digital converter circuit 70. The non-volatile area of ​​the memory 80 stores the exhaust fan's rated no-load current and its upper and lower tolerance range parameters corresponding to the exhaust fan motor's operating state. The processor 60 performs a subtraction operation between the acquired real-time operating current and the exhaust fan's rated no-load current, and verifies whether the difference falls within the tolerance range. Considering the electrical drive characteristics of the exhaust fan's induction motor, the processor 60 forcibly activates the underlying software mask timer within the first time observation window after control on-state, actively bypassing and discarding the first 200 to 300 milliseconds of current sampling frames. This aims to filter out the stator inrush current, which is as high as 3 to 5 times the steady-state value, generated when the motor overcomes rotor static friction and mechanical rotational inertia, and to prevent false fault interception caused by the hard characteristics of inductive loads.

[0036] Upon entering the steady-state aerodynamic slip zone, the tolerance range invoked in memory 80 is structured as an asymmetric bidirectional amplitude discrimination dead zone: the upper tolerance is widened to +25% to +35% of the rated no-load current, specifically for bridging the natural steady-state voltage fluctuations of the distribution network and accurately capturing the aerodynamic stall excitation inrush current caused by heavy dust accumulation in the dust filter; the lower tolerance converges to -15% to -20%, used to cross-identify sudden drops in air resistance and periodic rotor fluctuations caused by physical brittle fracture of the fan blades. When the measured operating current value exceeds the upper limit of the tolerance range, it indicates that the power consumption of the motor stator windings increases, and the rotor experiences additional mechanical resistance torque exceeding aerodynamic forces. The processor 60 determines that the fan blades of the exhaust fan 30 are jammed by foreign objects or that there is a physical blockage inside the exhaust channel. After determining that the exhaust fan hardware has failed, the expected airflow disturbance model is not established within the enclosure. The processor 60 responds to the abnormal state branch, triggers an instruction to stop the execution of the subsequent temperature difference calculation and phase change characteristic comparison program, packages the hardware operating status information, outputs the anti-condensation equipment fault code through the communication bus, and locks the subsequent program flow.

[0037] like Figure 4As shown, the transient temperature drop value of the chamber temperature during the airflow disturbance is obtained. Since the chamber temperature itself decreases along with the ground state temperature, this acquisition step specifically includes: recording the pre-disturbance temperature output by the temperature sensor at the moment the exhaust fan 30 starts; continuously collecting the temperature sequence output by the temperature sensor from the moment the exhaust fan 30 starts until the end of the set follow-up observation period after the exhaust fan 30 is turned off, and recording the lowest temperature in the temperature sequence as the post-disturbance temperature; subtracting the post-disturbance temperature from the pre-disturbance temperature to obtain the preliminary temperature difference; obtaining the natural heat dissipation temperature drop slope during the thermal inertia cooling period that is not affected by the airflow disturbance, and multiplying the natural heat dissipation temperature drop slope by the actual elapsed time from the moment the exhaust fan starts to the sampling time corresponding to the lowest temperature to obtain the natural cooling compensation value; adding the natural cooling compensation value to the preliminary temperature difference to obtain the transient temperature drop value after deducting the natural heat dissipation factor.

[0038] Furthermore, during the clock cycle corresponding to the output of the exhaust fan start command, the processor 60 extracts the latest internal temperature data with a synchronization timestamp and temporarily stores it as the pre-disturbance temperature in the variable area of ​​the memory 80. From the issuance of the exhaust fan start command, the processor 60 continuously extracts internal temperature data at a set sampling interval until the exhaust fan stop command is issued and a set follow-up observation period has elapsed; the processor 60 then temporarily stores the lowest temperature in this continuous temperature sequence as the post-disturbance temperature in the memory. The processor 60 executes a subtraction operation instruction to calculate the algebraic difference between the pre-disturbance temperature and the post-disturbance temperature to obtain the preliminary temperature difference.

[0039] The time constant of the temperature sensor is obtained through step response calibration after installation. The observation period is set to be no less than 3 times the time constant, and the sampling interval is no more than 1 / 10 of the time constant, so that continuous sampling covers the flow field attenuation after the exhaust fan stops, the interface evaporation continuation process, and the probe's own thermal response.

[0040] It should be noted that the 3-time constant is used to ensure that the probe's first-order thermal response is fully developed, and is not preset as the time for water film evaporation to complete. If, before the end of the set follow-up observation period, the current lowest temperature appears near the end of the observation period, and the continuous temperature sequence continues to decrease by an amplitude exceeding the noise band of the repeated drying test in this channel, the processor extends the follow-up observation period in units of the time constant and continues sampling until the lowest temperature no longer decreases beyond the noise band within the continuous observation interval. Then, the temperature after the disturbance is determined by the stable lowest temperature. Thus, the sensor response time and the duration of interface evaporation are controlled separately, avoiding the erroneous equating of the two.

[0041] To isolate the impact of continuous system cooling, processor 60 retrospectively extracts continuous historical temperature data points within the chamber during the undisturbed time window before the exhaust fan starts. Processor 60 performs a first-order linear regression equation on this historical data array, extracting the slope of the time derivative of the first-order linear equation, which is used as the slope of the natural cooling temperature drop. Processor 60's arithmetic logic unit calls least-squares regression instructions to extract the temperature data within the undisturbed observation window before the exhaust fan starts. Equally spaced historical discrete sampling pairs Based on the environmental thermal inertia filtering requirements, the sampling depth Locked between 15 and 25. The processor for solving the algebraic expression of the linear time derivative slope is configured as follows: .in, The slope of the linear time derivative. The first one within the undisturbed observation window The time for each discrete sampling point For the corresponding number The temperature inside the chamber collected at each sampling point, This represents the total number of equally spaced historical discrete sampling pairs. Due to the physical constraint of the device's large thermal capacity hysteresis, the natural cooling trajectory within the extremely short observation window exhibits extremely high linearity, and the calculated slope... Numerically, this is consistently negative, thus accurately separating the baseline heat dissipation scalar, which is purely dominated by the static heat transfer of the metal casing, at the software layer. Processor 60 executes a multiplication instruction, multiplying the natural heat dissipation temperature drop slope by the actual elapsed time from the exhaust fan startup to the sampling time corresponding to the lowest temperature, to obtain the natural cooling compensation value that occurs independently of airflow disturbances during this period. Since the cooling slope is negative, processor 60 performs an addition operation, adding the natural cooling compensation value to the initial temperature difference, and outputting the transient temperature drop value after deducting the natural heat dissipation attenuation. This step filters out the base steady-state heat conduction attenuation caused by the ambient temperature difference, allowing the obtained transient temperature drop value to separately quantify the net cooling parameter resulting from the superposition of exhaust fan flow field mixing and the latent heat absorption of moisture vaporization.

[0042] The temperature sensor 40 includes a contact probe 41 attached to the surface of the insulation layer of the branch cable 20, and a convection probe 42 suspended near the inner wall of the cable branch box; based on the data collected by the contact probe 41 and the convection probe 42 respectively, the step of obtaining the transient temperature drop value is independently performed; and the presence of the hidden condensation film on the surface of the branch cable 20 and the inner wall of the cable branch box is determined respectively.

[0043] Specifically, branch cable 20, as the main heating device of the system, has its boundary as the internal heat source interface, while the inner wall of the cable branch box, constrained by external weather conditions, has its boundary as the heat dissipation interface. The two exhibit heterogeneous characteristics in terms of temperature and humidity gradient evolution. The system hardware data link connects contact probe 41 and convection probe 42 to independent acquisition channels. During the airflow disturbance excitation and subsequent data extraction cycle, processor 60 allocates parallel computing branches to perform fitting calculations of the natural heat dissipation temperature drop slope and multiplication of the natural cooling compensation value for the time series acquired by the two probes, respectively, and outputs the transient temperature drop value after deducting compensation in parallel. Based on the independently output transient temperature drop value, the system separately completes the data state separation and comparison of the branch cable heating insulation surface and the metal cold source interface.

[0044] In one optional hardware implementation, the contact probe 41 employs a low-heat-capacity thin-film platinum resistance thermometer with a sensing area thickness not exceeding 0.3 mm, conforming to the surface to be measured and attached to the insulation layer of the branch cable 20. The probe leads are fixedly led out along the surface of the insulation layer in the downstream direction of the pulsed airflow. The convection probe 42 is spaced apart from the solid surface and suspended downstream of the airflow in the corresponding area to be measured. The two probes are connected to independent acquisition channels using a four-wire system. The thin-film low-heat-capacity, the downstream leads, and the separate arrangement are used to reduce probe heat sink and shading of the boundary layer; the contact probe directly follows the temperature of the surface to be measured, while the convection probe independently characterizes the temperature of the airflow itself.

[0045] The step response calibration after installation is performed on the actual thermal response chain formed by the contact probe 41, the attached medium, the probe leads, and the local insulating surface, rather than using only the nominal time constant of the bare sensor. The low heat capacity sensing area and the downstream leads of the contact probe 41 are used to first reduce heat sink and wind shielding; the remaining stable thermal coupling effects are simultaneously included in the dry reference and real-time detection under the same installation geometry, and random disturbances are included in the field noise statistics. Therefore, this embodiment does not assume that the probe heat sink is zero, but limits its influence on the judgment result through a three-layer approach of structural suppression, post-installation dynamic calibration, and homomorphic reference.

[0046] Before comparing the transient temperature drop value with the preset drying reference temperature drop value, the process includes the following steps: obtaining the drying reference temperature drop value by using a humidity sensor 50 arranged inside the cable branch box 10 to obtain the relative humidity inside the box; when the branch cable is not energized and the relative humidity inside the box is lower than the set deep drying threshold, starting the exhaust fan 30 to run the pulse disturbance duration; collecting the baseline temperature drop difference output by the temperature sensor during the operation of the exhaust fan, and calibrating the baseline temperature drop difference as the drying reference temperature drop value.

[0047] Understandably, processor 60 monitors the characteristics of digital operating current sequence data. When the operating current sequence value remains at zero continuously within a set time window, processor 60 determines that the branch cable is not carrying current and is in a non-energized state. At this time, Joule heating of the conductor stops, and the internal thermodynamic field tends to be in a steady state. Processor 60 synchronously reads the relative humidity parameter sequence obtained through the conversion channel of humidity sensor 50. When the relative humidity sequence value is below the deep drying threshold set in the memory, it indicates that the current air moisture content is insufficient to produce a precipitation phase change at the solid interface. The establishment of the deep drying threshold is controlled by the critical physical boundary of capillary condensation in the micropores of the polymer insulation surface. Processor 60 has a reduced-order calculation logic of the Magnus empirical equation embedded in its underlying layer, which solves the theoretical dew point in real time based on the real-time acquired box temperature. The threshold for determining the deep drying state is doubly locked: the ambient relative humidity parameter must be below 30%RH, and the algebraic difference between the insulation surface detection temperature and the real-time calculated dew point must be greater than the set anti-condensation safety margin (calibrated to 15℃). This thermodynamic defense effectively avoids the possibility of molecular-level water films remaining on the micro-roughness of the insulation layer from a physical mechanism perspective, ensuring high data reliability for the base temperature drop difference extracted during adaptive exhaust disturbances, and effectively avoiding the latent heat artifacts consumed by any hidden liquid phase forced phase transitions.

[0048] When the conditions of no heat generation and no liquid phase precipitation during shutdown are simultaneously met, the processor 60 enters the adaptive calibration program, controlling the exhaust fan 30 to perform airflow disturbance operation according to the set pulse disturbance duration. During this cycle, the processor 60 calls the natural heat dissipation compensation calculation program code to calculate the temperature drop caused by the forced mixing of dry air masses in a dry environment, and records it as the base temperature drop difference. The processor 60 saves the base temperature drop difference to a non-volatile memory area and calibrates it as the dry reference temperature drop value of the hardware system. This adaptive measurement and acquisition process internalizes and compensates for the basic data offset caused by differences in the physical volume of different equipment cabinets and the structural location distribution of the exhaust fan.

[0049] In one optional acquisition circuit implementation, two thin-film platinum resistance thermometers are excited by a four-wire constant current system and connected to a 24-bit ΔΣ analog-to-digital converter channel respectively. Zero-point, gain, and two-point temperature scale calibrations are performed before installation, and each temperature sample is formed by the average of at least 30 consecutive analog-to-digital conversion results. After installation, at least 30 sets of repetitive drying pulse tests are performed under the same exhaust fan parameters and sampling sequence. The inherent noise of each channel is determined by the standard deviation of the repetitive measurement sequence, and the drying reference temperature drop and the upper limit of the pure aerodynamic temperature fluctuation are written to memory 80 for each unit.

[0050] Post-installation drying repetition testing is also used to perform a self-test for the detectability of the acquisition link. If the inherent noise and the upper limit of pure aerodynamic temperature fluctuation of a certain acquisition channel exceed the preset allowable detection limit after statistical analysis, or if the repetitive pulse test cannot form a stable drying reference distribution, the processor 60 marks the channel as calibration abnormal, suspends the use of that channel to output the binary judgment of latent condensation or physical drying, and outputs a prompt message for recalibrating or checking the probe. Only after the drying reference and judgment dead zone meet the detectability conditions will the real-time condensation judgment process begin.

[0051] After acquiring the transient temperature drop value under real-time operating conditions and establishing a comparison baseline, the processor 60 executes the following logical instruction: compare the transient temperature drop value with the preset drying reference temperature drop value.

[0052] When the transient temperature drop is greater than the drying reference temperature drop, and the difference between the two exceeds the set latent heat of vaporization threshold, it is determined that there is a hidden condensation film inside the cable branch box, and a high-risk condensation alarm signal is output; when the transient temperature drop is less than or equal to the drying reference temperature drop, or the difference between the two does not exceed the latent heat of vaporization threshold, it is determined that the inside of the cable branch box is in a physically dry state.

[0053] Specifically, processor 60 compares the transient temperature drop value with the drying reference temperature drop value retrieved from memory 80. If the transient temperature drop value is greater than the drying reference temperature drop value, it indicates that the temperature drop at the temperature sensor measurement location caused by airflow disturbance exceeds the temperature drop generated by single sensible heat convection exchange under physical drying conditions. Processor 60 performs a subtraction calculation on the two to obtain a positive difference. Processor 60 reads the latent heat of vaporization determination threshold, which includes the sensor measurement inherent noise and the aerodynamic variance of the flow field. This determination threshold... Based on the mathematical convergence of static hardware noise floor and dynamic convection disturbance variance, the algebraic formula is as follows: In the formula The mapping is based on the Gaussian standard deviation obtained by joint calibration of the thermal noise of the analog-to-digital conversion circuit and the background drift of the sensor's sensitive element in a constant-temperature dark chamber. The extreme values ​​of non-phase change thermal fluctuations caused by purely mechanical air-cooled friction at the probe stagnation point when the exhaust fan establishes a forced convection field are characterized and calibrated by repeated testing on a dry reference after installation. In an embodiment using a four-wire thin-film platinum resistance thermometer and a 24-bit analog-to-digital converter circuit, the extreme values ​​are taken as 0.03℃ to 0.05℃. The absolute error decision dead zone constructed by the superposition of the two ensures that the positive temperature difference exceeding this threshold has strict physical exclusivity, mainly due to the latent heat of vaporization absorbed by the forced detachment of the thin liquid water from the interface into the gas phase.

[0054] The aforementioned 0.03℃ to 0.05℃ range is used to characterize the upper limit of short-term pure aerodynamic temperature fluctuations in the same acquisition channel under the same installation location, the same exhaust fan parameters, and the same sampling sequence. It is not an absolute accuracy indicator of the temperature sensor across its full range. When the probe, installation location, or exhaust fan parameters change, the processor 60 re-executes the drying baseline repeat test and updates this upper limit. By performing differential and repeated averaging within a short time window using the same probe and the same channel, fixed deviations can be canceled out in the differential calculation, and the dead zone can be controlled and determined using the noise statistics obtained from repeated field measurements.

[0055] Therefore, the aforementioned 0.03℃ to 0.05℃ is not the pre-assumed amplitude of the condensation signal in this method, nor is it a uniform fixed detection limit that all devices must reach. Rather, it is merely an example magnitude used in the optional high-resolution acquisition implementation to describe the upper limit of pure aerodynamic temperature fluctuations. Actual positive condensation determination is always based on the on-site drying baseline and latent heat of vaporization determination dead zone obtained under the same pulse conditions for the device, the probe, and the installation location.

[0056] The processor 60 compares the positive difference with the latent heat of vaporization threshold. When the calculated positive difference exceeds the latent heat of vaporization threshold, the processor 60 determines, based on physical relationships, that the additional temperature drop is caused by the phase change evaporation of liquid water adhering to the sensor detection interface under forced airflow, absorbing latent heat of vaporization from the local ambient air. Based on this correlation, the processor 60 establishes a state where a hidden condensation film adheres to the solid surface inside the cable branch box, triggers the data encapsulation program to package communication information, and outputs a high-risk condensation alarm signal to the outside through the communication interface. If the processor 60's comparison result indicates that the transient temperature drop is not greater than the drying reference temperature drop, or the calculated positive difference is within the latent heat of vaporization threshold range, it indicates that forced convection has not triggered a vaporization phase change process that consumes surrounding heat. The processor 60 determines that no liquid water adheres to the area, the inside of the cable branch box is physically dry, and the system returns to the normal time window data monitoring stage.

[0057] This implementation does not pre-assume a water film thickness or an average temperature drop across the entire chamber as a prerequisite for determining condensation. For the interface to be measured where the contact probe 41 is located, the vaporization energy required for forced evaporation of liquid water is primarily manifested as local heat loss at the interface and in the adjacent medium. The system uses the drying response under the same location, probe, and pulse conditions as a reference without phase change, and subtracts the natural heat dissipation component to directly obtain the residual additional temperature drop under real-time operating conditions relative to the reference without phase change. Therefore, the measurement is obtained from the actual on-site differential measurement, rather than being pre-calculated from an unknown water film mass.

[0058] The term "physically dry state" as used in this paper refers to the status label under the current calibrated resolution and latent heat of vaporization threshold of this acquisition method. It indicates that no latent condensation signal exceeding the detection dead zone was detected in this pulse detection, and does not presume that the surface under test is absolutely free of any trace moisture below the current detection limit at a microscopic level. This status label will not be output when the acquisition link fails the aforementioned detectability self-test.

[0059] When the branch cable 20 includes at least one target branch cable 21 and at least one adjacent branch cable 22, if the target branch cable 21 is in the thermal inertia cooling period and the operating current of the adjacent branch cable 22 is increasing, the operating current of the adjacent branch cable 22 is extracted to calculate the thermal radiation power; the thermal radiation power is used to make equivalent compensation and lower the latent heat of vaporization determination threshold near the target branch cable to counteract the evaporation hysteresis interference caused by the heating of the adjacent cable.

[0060] Furthermore, in the case of a physical distribution with multiple branches connected in parallel, the analog-to-digital converter circuit 70 acquires the digital operating current sequences corresponding to the target branch cable 21 and each adjacent branch cable 22 through multi-channel reading. When the processor 60 determines that the target branch cable 21 has entered the thermal inertia cooling period, it extracts the operating current data of the adjacent branch cables 22 and performs first-order differential calculation. If the calculation result is a continuous positive increment, the processor 60 determines that the operating current of the adjacent branch cables is on the rise. The increase in the operating current of the adjacent branch cables causes an increase in the Joule heating power of the conductor, and the generated heat is conducted outward through the insulation material, forming a local radiative heat source. This radiative heat source projects thermal radiation directionally onto the insulation surface of the target branch cable in a cooling state. When the liquid moisture on the surface of the target branch cable enters the forced vaporization stage due to the disturbance of the exhaust fan, the heat energy projected by the adjacent branch cables provides environmental compensatory heat for this vaporization process. The compensatory heat alleviates the local air temperature drop caused by moisture vaporization, resulting in a numerical contraction of the calculated transient temperature drop value, causing evaporation hysteresis interference.

[0061] To eliminate this nonlinear interference, processor 60 extracts the current RMS value of the digital operating current of adjacent branch cables, performs a square calculation, and multiplies it by the system's preset equivalent DC resistance parameter to calculate the basic heating power. Processor 60 retrieves the spatial thermal radiation attenuation matrix configured in memory 80, which integrates the geometric spacing between cable lines and the thermal radiation projection coefficient. Processor 60 multiplies the basic heating power by the corresponding projection coefficient in the matrix to derive the thermal radiation power acting on the outer surface of the target branch cable. Processor 60 applies a linear algebraic mapping relationship to convert the calculated thermal radiation power into a positive temperature equivalent compensation parameter, and performs an equivalent compensation down-adjustment operation on this parameter and the latent heat of vaporization threshold fixed in the system. The attenuation matrix is ​​structured as a two-dimensional constant lookup table in the storage area, and its mapped projection coefficients are based on the reduced-order equation of the equivalent projection coefficient of cylindrical thermal radiation. Offline conversion and input. In the equation, It is the equivalent projection coefficient of thermal radiation of a cylinder (which combines the pure geometric angle coefficient and the material radiation characteristics). The nominal outer diameter of the target cable. The Euclidean physical distance between the axis of the two associated cables. Let be the infrared emissivity constant of the polyethylene insulating medium. Obtain the radiant power. Then, processor 60 calls the first-order convection thermal resistance model. Solving for the positive temperature equivalent compensation parameters ,in The comprehensive convective heat transfer thermal resistance of the target detection interface is not a dynamic variable that needs to be calculated in real time. Instead, it is obtained through offline thermodynamic calibration experiments on specific cable branch boxes of a certain model and specification in a standard environmental test chamber during the R&D phase. Specifically, considering the steady-state heat transfer coupling relationship between the surface of the cross-linked polyethylene insulating medium cylinder and the forced flow field of the exhaust fan, based on empirical heat transfer constants, the comprehensive convective heat transfer thermal resistance is numerically defined between 0.15 K / W and 0.28 K / W. Its specific mapping value is inversely proportional to the rated no-load wind speed of the selected exhaust fan and the geometric topology inside the box, and is fixed as a static constant in the non-volatile area of ​​the memory 80. In response to the physical distortion caused by the target phase change cooling sampling value due to environmental thermal radiation compensation, the processor 60's bottom-level comparator introduces the compensation parameter into the judgment benchmark side through an algebraic negative sign for equivalent compensation downgrading (i.e., a new calculation threshold). Set as This dynamic lowering of the judgment threshold in the Boolean logic domain is essentially an equivalent adjustment of the system sensitivity at the level of the limited and reduced phase change cooling detection signal. Without increasing the overhead of the front-end sensing hardware, it accurately offsets the risk of false negatives caused by the cross-projection of the confined thermal field. By executing this operation instruction, the system uses thermal radiation power to equivalently compensate and lower the latent heat of vaporization judgment threshold, logically neutralizing the signal recognition error caused by the coupling of spatial thermal fields from multiple heat sources.

[0062] After outputting the high-risk condensation alarm signal, the process also includes: starting the heating dehumidifier 120 configured inside the cable branch box 10 to perform a baking operation; during the baking operation, the steps of starting the exhaust fan 30 and comparing the transient temperature drop value are performed cyclically at set intervals; until the latest acquired transient temperature drop value drops to within the drying reference temperature drop value, it is determined that the hidden condensation film has been completely evaporated and discharged, and the heating dehumidifier 120 is turned off.

[0063] Specifically, after generating a high-risk condensation alarm signal, the processor 60 sends a valid control level to the configured output port. The heating dehumidifier 120, connected to the power supply circuit, begins a baking operation to release heat. The increase in temperature inside the enclosed space increases the air's saturation absorption capacity for water vapor, causing moisture adhering to the physical insulation surface to evaporate more rapidly into the gaseous environment.

[0064] To track the actual dehumidification effect, processor 60 initiates a cyclic interrupt timer task. The interval of this timer loading is controlled by the physical dynamic balance between the gas phase heat capacity of the enclosed space and the heat generation power of the dehumidifier. Processor 60 uses the energy conservation equation in a reduced-order manner. Implement dynamic calibration. In the formula, For the set interval duration, The volume of clean air inside the chamber. The rated active heating power of the dehumidifier, The space electrothermal exchange efficiency coefficient is used to characterize the conversion and retention rate of heat energy transferred from the heating element of the dehumidifier to the effective gas phase space of the branch box. Its calibration comprehensively considers the background heat loss caused by the non-absolute thermal boundary of the metal sheet metal shell of the power distribution equipment and the heat reflection characteristics of the inner wall. Based on the physical structure of conventional outdoor switch cabinets and cable branch boxes, the space electrothermal exchange efficiency coefficient is a fixed empirical value in the range of 0.65 to 0.75 in the system engineering preset calibration. and For the specific heat capacity and density of dry air, It is then calibrated as the minimum effective temperature rise range (fixed at 3°C ​​to 5°C) sufficient to raise the local water vapor saturation partial pressure and force the water to activate. The forced intervention of this thermodynamic physical step ensures that before each round of exhaust fan pulse flaw detection is activated, the solid-phase insulation interface has been fully injected with the effective enthalpy value that pushes the remaining microscopic water film into the critical state of evaporation, effectively avoiding thermal fatigue of the detection relay and wasted computing power of the processor caused by blind high-frequency cycling.

[0065] When the timer accumulates to the set interval, the processor 60 stops the control level of the heating dehumidifier 120 to pause the forced heat input. During the interval of heat input pause, the processor 60 re-outputs the control level to start the exhaust fan 30 to run the pulse disturbance duration, and calls the aforementioned compensation algorithm to calculate the latest transient temperature drop value. As the heating and dehumidification process progresses, the moisture stored on the insulating surface decreases, and the phase change endothermic phenomenon that can be excited by convection weakens. The processor 60 sends the latest acquired transient temperature drop value to a comparison instruction to verify it against the drying reference temperature drop value. When the latest acquired transient temperature drop value is not greater than the drying reference temperature drop value, it indicates that the residual moisture volume is no longer sufficient to support the forced vaporization endothermic physical reaction that produces a measurable temperature drop. Based on this logic, the processor 60 determines that the implicit condensate film has been completely evaporated and drained. The processor 60 resets the control status bit of the heating dehumidifier 120, stops the baking operation, and the system control flow safely returns to normal data monitoring.

[0066] When the rise of the operating current exceeds the set load surge threshold, the branch cable 20 is determined to be in the Joule heat release period; during the Joule heat release period, the temperature inside the box is continuously monitored; when the temperature inside the box reaches the set heat dissipation start threshold, the exhaust fan 30 is kept on continuously to exhaust the heat emitted by the branch cable 20 to the outside of the cable branch box.

[0067] Understandably, when processor 60 performs differential calculations on the operating current time series, if the increase in the calculated average value of the current observation window compared to the average value of the historical observation window exceeds a preset load surge threshold, it indicates a surge in transmission line power and a rise in heat generation. This load surge threshold is specifically established based on the safe current carrying capacity and static thermal balance equation of branch cable 20. At the underlying logic level, it is defined as the minimum effective current increment sufficient to induce a positive drift in the surface temperature of the conductor and insulation layer beyond the natural heat dissipation equilibrium state, thus filtering out normal small fluctuations in the power grid.

[0068] In this embodiment, for standard power distribution conditions, the load surge threshold is numerically set to 15% to 20% of the rated full-load operating current of the branch cable. The processor 60 establishes that the branch cable 20 has entered the Joule heat release period in the status zone. The processor 60 changes the execution frequency level of the temperature sampling and reading task, continuously checking the newly collected box temperature data against the heat dissipation activation threshold set in the memory 80. The heat dissipation activation threshold is set based on a joint deduction of the accelerated aging critical temperature boundary of the insulating medium and the upper limit temperature of the normal operating environment of the power distribution equipment. To ensure the long-term thermal stability of cross-linked polyethylene and other insulating materials and avoid thermal runaway or capacity decay, the heat dissipation activation threshold is locked within the temperature range of 55°C to 65°C in conventional application scenarios to ensure that forced convection heat dissipation is initiated before the insulating material reaches its thermal stress limit. When the box temperature data rises to the heat dissipation activation threshold, the processor 60 sends a long-term conduction enable signal to the isolation drive circuit. The exhaust fan 30 receives this signal and enters continuous operation mode. The continuous operation of the exhaust fan 30 establishes a continuous forced convection heat exchange channel between the internal space of the cable branch box and the external atmospheric environment, continuously exhausting the high-temperature gas that has been heated and expanded in the internal environment outside the box and introducing cold air for convection.

[0069] For this high-load heat dissipation deactivation link, if the turn-on and turn-off instructions share the same absolute temperature reference or are adjacent to the boundary, the slight thermal fluctuations in ambient temperature near the cooling critical point will drive the control pin to output a high-frequency toggling level, which can easily lead to arc sintering of the mechanical relay contacts in the exhaust fan drive circuit or thermal breakdown of the solid-state relay. Therefore, the processor's 60-level low-level code resets the upper boundary hard constraint of the safe zone to the heat dissipation start threshold minus the solidified dead zone hysteresis parameter. This constructs a nonlinear Schmitt trigger control loop. The dead-zone hysteresis parameter... It fully integrates the low-pass filtering delay characteristics of heat transfer in large-section metal core cables, with an engineering calibration range of 4℃ to 6℃. The processor 60 only triggers a state reset instruction and cancels the conduction enable signal when the latest frame's internal temperature not only falls below the heat dissipation activation threshold but also further penetrates the physical dead zone and enters the deep reset safety range. This hysteresis mechanism effectively suppresses high-frequency thermal oscillations at critical heat dissipation points, ensuring the long-term service life of high-power actuators in power distribution nodes. After the internal temperature drops to the set reset safety range, the processor 60 cancels the conduction enable signal, achieving active cooling thermal protection during high-load transmission processes.

[0070] Based on the same inventive concept, this embodiment of the invention also provides a cable branch box environmental data acquisition system, including a memory 80 and a processor 60; the memory 80 stores a computer program; when the processor 60 executes the computer program, it implements the steps in the cable branch box environmental data acquisition method described in any of the above embodiments.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for acquiring environmental data of a cable branch box, applied in a cable branch box environmental data acquisition system, the system comprising a cable branch box, wherein an exhaust fan and a temperature sensor are installed inside the cable branch box, and branch cables are arranged through the inside of the cable branch box, characterized in that, Includes the following steps: The operating current of the branch cable and the internal temperature of the box output by the temperature sensor are collected. Monitor the changes in the operating current, and when the decrease in the operating current exceeds the set load drop threshold, determine that the branch cable is in the thermal inertia cooling period; During the thermal inertia cooling period, the exhaust fan is started and operated for a set pulse disturbance duration, then shut down to generate airflow disturbance inside the cable branch box; Obtain the transient temperature drop value of the chamber temperature during the airflow disturbance; Compare the transient temperature drop value with the preset drying reference temperature drop value; When the transient temperature drop value is greater than the drying reference temperature drop value, and the difference between the two exceeds the set latent heat of vaporization determination threshold, it is determined that there is a hidden condensation film inside the cable branch box, and a high-risk condensation alarm signal is output. When the transient temperature drop is less than or equal to the drying reference temperature drop, or when the difference between the two does not exceed the latent heat of vaporization determination threshold, the inside of the cable branch box is determined to be in a physically dry state.

2. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, Before comparing the transient temperature drop value with the preset drying reference temperature drop value, the method further includes the step of obtaining the drying reference temperature drop value: The relative humidity inside the cable branch box is obtained by a humidity sensor arranged inside the box. When the branch cable is not energized and the relative humidity inside the box is lower than the set deep drying threshold, the exhaust fan is started to run for the pulse disturbance duration. The difference in baseline temperature drop output by the temperature sensor during the operation of the exhaust fan is collected, and the difference in baseline temperature drop is calibrated as the drying reference temperature drop value.

3. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, The step of obtaining the transient temperature drop value of the chamber temperature during the airflow disturbance includes: Record the temperature before disturbance output by the temperature sensor at the moment the exhaust fan starts; From the moment the exhaust fan starts until the end of the set follow-up observation period after the exhaust fan is turned off, the temperature sequence output by the temperature sensor is continuously collected, and the lowest temperature in the temperature sequence is recorded as the temperature after disturbance. Subtracting the temperature after the disturbance from the temperature before the disturbance yields the initial temperature difference; Obtain the natural heat dissipation temperature drop slope during the thermal inertia cooling period that is not affected by the airflow disturbance, and use the natural heat dissipation temperature drop slope to multiply by the actual elapsed time from the start time of the exhaust fan to the sampling time corresponding to the lowest temperature to obtain the natural cooling compensation value. Add the initial temperature difference to the natural cooling compensation value to obtain the transient temperature drop value after deducting the natural heat dissipation factor.

4. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, After outputting the high-risk condensation alarm signal, it also includes: The heating and dehumidifying unit configured inside the cable branch box is activated to perform a baking operation; During the baking process, the steps of starting the exhaust fan and comparing the transient temperature drop value are performed cyclically at set intervals. When the latest acquired transient temperature drop value drops to within the dry reference temperature drop value, it is determined that the hidden condensation film has been completely evaporated and discharged, and the heating dehumidifier is turned off.

5. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, It also includes the following steps: When the increase in the operating current exceeds the set load surge threshold, the branch cable is determined to be in the Joule heat release period; During the Joule heat release period, the temperature inside the chamber is continuously monitored; When the temperature inside the box reaches the set heat dissipation start threshold, the exhaust fan is kept continuously running to expel the heat emitted by the branch cable from outside the cable branch box.

6. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, When the branch cable includes at least one target branch cable and at least one adjacent branch cable, if the target branch cable is in the thermal inertia cooling period and the operating current of the adjacent branch cable is increasing, the operating current of the adjacent branch cable is extracted to estimate the thermal radiation power. The latent heat of vaporization determination threshold near the target branch cable is reduced by using the thermal radiation power to offset the evaporation hysteresis interference caused by the heating of adjacent cables.

7. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, After determining that the branch cable is in the thermal inertia cooling period and before starting the exhaust fan, an external temperature immunity judgment step is also included: The ambient temperature outside the cable branch box is collected synchronously. Calculate the slope of the external temperature decrease; When the absolute value of the slope of the external ambient temperature drop is greater than the absolute value of the slope of the natural heat dissipation temperature drop inside the box, it is determined that the cable branch box is suffering from a sudden cold attack by external weather, the step of starting the exhaust fan is suspended, and an external condensation warning is output.

8. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, During the step of shutting down the exhaust fan after the set pulse disturbance duration is started, the real-time operating current of the exhaust fan is collected simultaneously. When the real-time operating current deviates from the set rated no-load current of the exhaust fan and exceeds the tolerance range, it is determined that there is a physical blockage in the fan blades or exhaust channel of the exhaust fan. The step of acquiring the transient temperature drop value is terminated, and a fault code for the anti-condensation equipment is output.

9. The method for acquiring environmental data of a cable branch box according to claim 1, characterized in that, The temperature sensor includes a contact probe attached to the surface of the insulation layer of the branch cable, and a convection probe suspended near the inner wall of the cable branch box. The steps of obtaining transient temperature drop values ​​are performed independently based on the data collected by the contact probe and the convection probe, respectively. Determine whether the hidden condensation film exists on the surface of the branch cable and the inner wall of the cable branch box.

10. A cable branch box environmental data acquisition system, characterized in that, Including memory and processor; The memory contains computer programs; When the processor executes the computer program, it implements the steps in the cable branch box environmental data acquisition method as described in any one of claims 1 to 9.

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