A method and system for checking thermoelectric properties of a cable branch box

Abstract

The application discloses a kind of thermoelectric characteristics of cable branch box and system, the steps of the checking method are as follows: acquisition branch box in each branch circuit operating current value, preset temperature measuring point real-time temperature value and environmental temperature and humidity value, obtain reference resistance value and determine the topological correlation parameter between temperature measuring point and target checking contact point and path effective degree factor, construct the thermoelectric coupling response degree of the product coupling of load deviation, resistance drift ratio and hygrothermal stress factor three, based on thermoelectric coupling response degree, the normalized difference of each temperature measuring point is weighted and summed to obtain equivalent thermal offset, using the adaptive correction step driven by sliding window volatility to carry out iterative incremental correction to equivalent resistance correction value, and output convergent state equivalent resistance after convergence.The application can directly output the equivalent resistance of target contact point without disassembling branch box cabinet, and accurately quantifies the degree of contact point deterioration.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment condition monitoring and evaluation technology, and in particular to a method and system for verifying the thermoelectric characteristics of a cable branch box. Background Technology

[0002] With the continuous expansion of urban power distribution networks and the advancement of underground construction, cable branch boxes, as intermediate power distribution nodes connecting multiple cable lines, have been deployed on a large scale in medium and low voltage power distribution networks due to their advantages of compact structure, small footprint, and ease of maintenance, undertaking the key function of collecting and distributing electrical energy.

[0003] The internal structure of a cable branch box involves numerous conductive contact surfaces, including busbar connections for multiple branch circuits, circuit breaker contacts, and cable joints. During long-term operation, the resistance of these contact surfaces gradually deteriorates due to factors such as contact pressure relaxation, oxide film thickening, and environmental humidity corrosion. Because branch boxes typically employ a fully or semi-enclosed cabinet structure with limited internal space and ventilation, the localized heating caused by increased contact resistance has a significant cumulative effect. Under high-load conditions, this can easily lead to a vicious cycle of thermoelectric coupling—temperature rise further increases resistance, which in turn exacerbates heating, potentially causing insulation degradation or even thermal failure.

[0004] Currently, the main methods for assessing the thermal state of internal contacts in cable distribution boxes include external infrared thermal imaging and temperature field inversion based on finite element models. Infrared thermal imaging is limited by the thermal insulation of the cabinet shell, making it difficult to accurately obtain the true temperature of deep internal contacts. While finite element inversion can reconstruct the internal temperature distribution, it requires high model accuracy and computational resources, and cannot directly output the equivalent resistance information of the contacts, making it difficult to quantitatively assess the degree of contact degradation from an electrical perspective. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for verifying the thermoelectric characteristics of a cable branch box, which can directly output the convergent equivalent resistance of the target verification contact without disassembling the branch box cabinet, and accurately quantify the degree of contact degradation from an electrical perspective.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for verifying the thermoelectric characteristics of a cable branch box includes the following steps: S1 collects the operating current value of each branch circuit in the cable branch box and the real-time temperature value of each preset temperature measuring point, and at the same time collects the temperature and humidity values ​​of the environment where the branch box is located. S2, obtain the reference resistance value corresponding to each branch circuit, determine the topology correlation parameters between each temperature measurement point and the target verification point, and calculate the path effectiveness factor corresponding to each temperature measurement point based on the topology correlation parameters. S3, construct the load deviation degree based on the deviation between the operating current value and the rated value of each branch circuit, construct the resistance drift ratio based on the ratio of the equivalent resistance correction value output by the previous iteration to the reference resistance value, construct the damp heat stress factor based on the normalized values ​​of ambient temperature and humidity, and multiply the load deviation degree, resistance drift ratio and damp heat stress factor to obtain the thermoelectric coupling response degree of the current cycle. S4. Based on the thermoelectric coupling responsivity, the normalized difference between the real-time temperature value and the reference temperature value of each temperature measurement point is multiplied by the corresponding path validity factor and then summed to obtain the equivalent thermal offset of the current round. S5, calculate the sliding window fluctuation of the equivalent thermal offset in the most recent preset round, determine the adaptive correction step size based on the equivalent thermal offset and the sliding window fluctuation, and incrementally correct the equivalent resistance correction value of the previous iteration with the adaptive correction step size to obtain the equivalent resistance correction value of the current round. S6, determine whether the absolute value of the difference between the equivalent resistance correction value of the current round and the equivalent resistance correction value of the previous round is less than the preset convergence threshold. If not, return to S3 with the equivalent resistance correction value of the current round to execute the next iteration. If so, output the equivalent resistance correction value of the current round as the converged equivalent resistance.

[0007] Furthermore, the load deviation is the weighted root mean square of the current deviation of each branch circuit, and the weighting coefficient is determined according to the rated capacity ratio of each branch circuit; the damp heat stress factor is constructed in the form of logarithmically compressed temperature and humidity normalized product; the thermoelectric coupling responsivity is the product of the load deviation, the resistance drift ratio and the damp heat stress factor.

[0008] Furthermore, the path effectiveness factor adopts a saturated function form, with the topological correlation parameter as the numerator and the sum of the topological correlation parameter and the preset saturation adjustment constant as the denominator.

[0009] Furthermore, the sliding window volatility is the standard deviation of the equivalent thermal offset within the most recent preset window length; the numerator of the adaptive correction step size is the product of the equivalent thermal offset and the reference resistance value, and the denominator includes a volatility damping term.

[0010] Furthermore, each temperature measuring point is arranged at intervals along the heat conduction path of each branch circuit in the branch box. The topology correlation parameter is determined based on the equivalent thermal resistance length of the heat conduction path traversed between the temperature measuring point and the target verification point in the electrical topology.

[0011] Furthermore, the preset convergence threshold is determined based on the product of the reference resistance value of the target verification point and the preset accuracy ratio, and the method also sets a maximum iteration cycle limit.

[0012] This invention also proposes a thermoelectric characteristic verification system for cable branch boxes, including a data acquisition module, a topology parameter configuration module, a coupling response construction module, a thermal offset calculation module, an adaptive iterative correction module, and a convergence determination output module.

[0013] The beneficial effects of this invention are as follows: By employing a three-factor coupling scheme—load deviation, resistance drift ratio, and damp heat stress factor—to construct the thermoelectric coupling response, the combined influence of load fluctuations, resistance degradation trends, and environmental damp heat conditions on the junction thermal state can be incorporated into the same quantitative framework, avoiding the one-sidedness of single-factor evaluation. Furthermore, the introduction of a saturated weighting mechanism based on the path validity factor of topological correlation parameters ensures that temperature measurement points with closer topological distances contribute more weight, while the contribution of distant temperature measurement points naturally decreases, eliminating the need for prior manual screening of temperature measurement points. Finally, the adoption of an adaptive correction step-size iteration strategy driven by sliding window volatility automatically suppresses the correction amplitude to avoid oscillation divergence when fluctuations are large in the early stages of iteration, and automatically increases the correction step-size to accelerate convergence when fluctuations tend to stabilize in the later stages of iteration. This ensures that the final output convergent equivalent resistance accurately reflects the true equivalent resistance value of the target verification junction under thermoelectric coupling equilibrium. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall process of the thermoelectric characteristic verification method for cable branch boxes described in this invention; Figure 2 This is a schematic diagram of the thermoelectric characteristic verification system for the cable branch box described in this invention; Figure 3 This is a schematic diagram of the sub-processes for constructing the thermoelectric coupling responsivity and calculating the equivalent thermal offset as described in this invention. Detailed Implementation

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] This invention proposes a method for verifying the thermoelectric characteristics of a cable branch box. The overall idea is as follows: using the operating current of each branch circuit within the branch box, the real-time temperature of a preset temperature measurement point, and the ambient temperature and humidity as multi-source inputs, it constructs three interrelated variables: thermoelectric coupling responsivity, equivalent thermal offset, and equivalent resistance correction value. Through an adaptive iterative convergence process, it ultimately outputs the convergent equivalent resistance of the target verification point in thermoelectric coupling equilibrium. For example... Figure 1 As shown, the method includes steps S1 to S6, where S3 to S6 constitute an iterative loop.

[0017] S1. Collect the operating current value of each branch circuit in the cable branch box, the real-time temperature value of each preset temperature measuring point, and the ambient temperature and humidity value. The core purpose of this step is to obtain all the original physical quantities required for subsequent thermoelectric coupling iterative calculations, thus forming the data foundation layer of the method.

[0018] Specifically, for the cable branch box Each branch circuit has a current transformer installed at the busbar connection section to collect the operating current value of each circuit. Simultaneously, the heat conduction paths along each branch circuit are pre-set inside the branch box. There are 1 temperature measurement point, and a contact temperature sensor is installed at each temperature measurement point to collect the real-time temperature value of each point. An ambient temperature and humidity sensor is installed outside the branch box to collect ambient temperature values. and ambient humidity value The sampling times of all sensors are kept synchronized to ensure the time correspondence between physical quantities within the same sampling period.

[0019] In practical engineering, the accuracy class of current transformers should preferably be 0.5 or higher, and temperature sensors should preferably be platinum resistance or thermocouple type, with a temperature measurement accuracy of not less than [a certain value]. The density of temperature measurement points is determined based on the number of circuits and spatial structure inside the branch box. Generally, 2 to 3 temperature measurement points are set up on each main circuit, with at least one temperature measurement point located on the heat conduction path near the target verification point.

[0020] S2. Obtain the reference resistance value and determine the topological correlation parameters and path validity factor between each temperature measurement point and the target verification point. The core purpose of this step is to establish a spatial mapping relationship between the temperature measurement points and the target verification point, so that the temperature contribution of each temperature measurement point in subsequent calculations can be differentiated and weighted according to its topological distance from the target point.

[0021] Specifically, the reference resistance value corresponding to each branch circuit. The following method is used to determine the DC resistance of the target verification contact: Before the branch box is put into operation or after the most recent maintenance, use a micro-ohmmeter or a four-wire resistance meter to perform offline measurement, and convert the measurement results to the standard temperature (usually 100°C). The resistance value below the reference resistance value is used as the reference resistance value. For scenarios where there are multiple contacts to be calibrated within the same branch box, each contact corresponds to an independent reference resistance value.

[0022] Topology correlation parameters ( ) reflects the The tightness of the heat conduction path between the temperature measuring point and the target verification point in the electrical topology. In engineering practice, this parameter is determined based on the equivalent thermal resistance length of the heat conduction path traversed between the temperature measuring point and the target verification point: firstly, along the solid heat-conducting media such as busbars, connecting conductors, and cable joints inside the branch box, the length from the first... The shortest thermal path from each temperature measurement point to the target verification point is then used to calculate the equivalent thermal resistance length based on the thermal conductivity, cross-sectional area, and length of each conductor material along the path. Finally, the reciprocal of the equivalent thermal resistance length is taken as the topology correlation parameter. That is, the shorter the thermal path and the lower the thermal resistance of the temperature measurement point, the larger the topology correlation parameter, reflecting the stronger the correlation between its temperature information and the actual temperature of the target connection point.

[0023] Based on this, the path effectiveness factor corresponding to each temperature measurement point is calculated. To avoid the path validity factor tending to infinity when the topological association parameter is too large, a saturated function form is adopted: In the formula, This is a preset saturation adjustment constant, and its value range is generally [value range missing]. to The specific value is determined based on the order of magnitude of the total length of the heat conduction path inside the branch box. This saturated function ensures that the path effectiveness factor always falls within a certain range. Within the interval, the path effectiveness factor of temperature measurement points with larger topological correlation parameters (i.e., closer distances) tends to be... The path validity factor for temperature measurement points with smaller topological correlation parameters (i.e., farther distances) tends to be close to... This allows for the natural decay of the contribution weight of the temperature measurement point.

[0024] Temperature measuring points are spaced along the heat conduction path of each branch circuit within the branch box. The spacing between adjacent measuring points is evenly distributed based on the circuit length or densified according to the location of critical connections. For a typical 10kV cable branch box, the length of each branch circuit is usually... to Between, the spacing between temperature measuring points is generally controlled at to Within the range.

[0025] S3. Construct the load deviation, resistivity drift ratio, and damp heat stress factor, and calculate the thermoelectric coupling response. The core objective of this step is to quantify the three key factors affecting the thermal state of the junction—the degree of load fluctuation, the trend of resistance degradation, and the ambient humid and hot conditions—into three dimensionless constructed quantities, and then form a thermoelectric coupling responsivity that comprehensively reflects the current thermoelectric state through product coupling, which serves as the driving coefficient for subsequent calculation of the equivalent thermal offset.

[0026] 1. Construction of load deviation Load deviation This reflects the overall deviation of the current operating current of each branch circuit from its rated value. In cable branch boxes with multiple circuits operating in parallel, the load rates of each circuit may differ significantly. Therefore, a weighted root mean square (RMS) form is used to account for the differentiated contributions of each circuit. In the formula, The total number of branch loops, For the first The operating current value of each branch circuit. For the first The rated current value of each branch circuit. For the first The weighting coefficient for each branch circuit. The weighting coefficient is determined based on the percentage of the rated capacity of each branch circuit, i.e. This allows circuits with larger rated capacities to have a greater weight in the overall deviation. This weighted root mean square form can effectively distinguish between two operating states that have drastically different thermal effects in engineering practice: "all circuits are slightly deviated" and "a few circuits are severely overloaded".

[0027] 2. Construction of the resistance drift ratio Resistance drift ratio This reflects the deviation of the equivalent resistance correction value from the initial reference state during the iteration process: In the formula, This is the equivalent resistance correction value output from the previous iteration. This is the reference resistance value. In the initial stage of the iteration, The initial value is set to ,at this time As the iteration progresses, if the contact does indeed deteriorate, the equivalent resistance correction value will gradually increase, and the resistance drift ratio will increase accordingly. This will amplify the correction strength of subsequent cycles in the thermoelectric coupling responsivity, forming a positive feedback mechanism to accelerate the approximation of the true resistance value.

[0028] 3. Construction of damp-heat stress factors Moist heat stress factor The combined effects of ambient temperature and humidity on the docking point thermal state are quantified into a single dimensionless index. Considering that the combined effect of temperature and humidity exhibits diminishing marginal returns in high-value regions (i.e., the incremental impact on the docking point thermal state gradually weakens as temperature and humidity continue to rise), a logarithmic compression method is adopted: In the formula, This is the ambient temperature value. The preset reference temperature value (generally taken as...) corresponding absolute temperature ), This represents the ambient humidity value (in percentage form). The preset reference humidity value (generally taken as...) The introduction of the logarithmic function ensures that the stress factor does not increase indefinitely under extreme high temperature and humidity conditions, while its value is close to that under normal temperature and humidity conditions. .

[0029] 4. Synthesis of thermoelectric coupling responsivity The thermoelectric coupling responsivity of the current round is obtained by multiplying and coupling the above three constructed quantities: Thermoelectric Coupling Responsivity The physical meaning of this is that it comprehensively characterizes the degree to which the thermal state of the junction deviates from normal operating conditions under current load conditions, current resistance degradation level, and current ambient humid and hot conditions. The product structure of the three factors ensures that the thermoelectric coupling responsivity will only achieve a large value when all three types of influencing factors are at a significant level. If any factor approaches zero (such as when the load is close to the rated value, the resistance is not degraded, or the environmental conditions are mild), it will suppress the overall amplitude of the responsivity.

[0030] It should be noted that in the first iteration ( Before starting, the initial states of three structural quantities need to be set: load deviation. The current data from the current sampling period is used for direct calculation, without relying on historical iteration data; the initial value of the resistance drift ratio is... That is, assuming that the equivalent resistance has not deteriorated or shifted initially; damp heat stress factor The thermoelectric coupling responsivity is calculated directly based on the current ambient temperature and humidity values. Therefore, the thermoelectric coupling responsivity in the first iteration... It only reflects the effects of load and environmental factors, and the feedback effect of resistance degradation takes effect from the second iteration onwards. This gradual start-up mechanism avoids the overshoot of the first-round correction due to improper resistance drift ratio values ​​when prior information is lacking.

[0031] S4. Calculate the equivalent thermal offset of each temperature measurement point by weighted summation based on thermoelectric coupling responsivity. The core objective of this step is to aggregate the temperature deviation information of each temperature measurement point into a scalar by weighting it with the path validity factor, and use it as an intermediate quantity to characterize the degree of thermal state deviation of the target verification point. At the same time, the scalar is dynamically modulated by the thermoelectric coupling responsivity so that it can be adaptively updated as the resistance correction value changes during the iteration process.

[0032] Specifically, the normalized difference between the real-time temperature value and the reference temperature value at each temperature measurement point is multiplied by the corresponding path validity factor and summed. Then, the thermoelectric coupling responsivity is used as the modulation coefficient to obtain the equivalent thermal offset for the current round. In the formula, For the current iteration round, The thermoelectric coupling responsivity for the current round (output from step S3). This represents the total number of temperature measurement points. For the first Real-time temperature values ​​at each temperature measurement point For reference temperature value, For the first The path validity factor corresponding to each temperature measurement point (determined by step S2).

[0033] In the structure of this formula, the inner layer summation Essentially, the path validity factor is used as the weight to weight and aggregate the normalized temperature deviations of each temperature measurement point. The result reflects the overall thermal shift trend in the area near the target verification point—temperature measurement points with closer topological distances have similar path validity factors. Temperature measurement points that contribute significantly to the overall weight and are geographically distant are closer in path effectiveness factor. The contribution naturally decays, thus achieving the effect of automatically focusing on temperature information near the target junction without manual screening. The outer layer is multiplied by the thermoelectric coupling responsivity. This allows the thermal offset to be dynamically adjusted as the load state, resistance degradation level, and environmental conditions change during the iteration process, avoiding over-correction or under-correction problems caused by using a fixed correction range under different operating conditions.

[0034] Equivalent thermal offset The sign of the value carries directional information: a positive value indicates that the overall temperature of the temperature measurement area is higher than the reference temperature (implying that there may be additional heat generation caused by increased resistance at the contact point), while a negative value indicates that the overall temperature is lower than the reference temperature. In the subsequent step S5, this value will directly participate in the incremental update of the equivalent resistance correction value. A positive offset drives the resistance correction value to increase, and a negative offset drives it to decrease, forming a closed-loop correction logic that conforms to physical causality.

[0035] S5. Calculate the sliding window volatility and determine the adaptive correction step size to update the equivalent resistance correction value. The core objective of this step is to introduce sliding window volatility as a measure of the stability of the iterative process, and to construct an adaptive step size mechanism that can automatically adjust the correction magnitude according to the convergence trend of the iteration, thereby suppressing oscillation divergence in the early stage of iteration and accelerating convergence in the later stage of iteration.

[0036] 1. Calculation of sliding window volatility Sliding window volatility Defined as recent The standard deviation of the equivalent thermal offset sequence is used to measure the severity of fluctuations in thermal offset during the iteration process. In the formula, The preset window length is where , For the most recent The arithmetic mean of the wheel's equivalent thermal offset. Window length. The value of is generally to Specifically, based on the maximum number of iterations preset by the method... to The proportion is determined.

[0037] In the early stages of iteration, when the number of completed iteration rounds... Not long enough for the window At that time, there was insufficient data in the window. One, at this point, based on the actual number of completed... The standard deviation of the equivalent thermal offset is calculated, that is, the equation above... by The subscripts for summation in the formula should be adjusted accordingly. to This approach ensures that the sliding window volatility can be calculated correctly in any iteration and will not be interrupted due to insufficient data.

[0038] 2. Determining the adaptive correction step size Adaptive correction step size The design follows these principles: when the absolute value of the equivalent thermal offset is large, a larger correction step size should be given to accelerate convergence; however, when the volatility is high, the correction step size should be suppressed to prevent oscillation. Based on this principle, the formula for calculating the adaptive correction step size is: In the formula, The reference resistance value, The preset fluctuation damping coefficient typically ranges from [value range missing]. to In molecules, Mapping the dimensionless equivalent thermal offset to a resistance-dimensional space (unit: This ensures that the correction step size has the same physical dimensions as the target output. In the denominator, Constitutes the volatility damping term—when volatility When the volatility is large, the denominator increases significantly, and the correction step size is compressed; when the volatility approaches zero, the denominator approaches zero. The correction step size is basically equal to This mechanism enables full-speed correction. It allows the iterative process to automatically adopt a conservative strategy in the early stages when oscillations are more intense, and automatically switch to an aggressive strategy in the later stages when the process is more stable, without the need to manually set fixed step sizes or segmented adjustment rules.

[0039] 3. Incremental update of equivalent resistance correction value The equivalent resistance correction value from the previous iteration is incrementally corrected using an adaptive correction step size: In the formula, This is the equivalent resistance correction value for the current round. This is the equivalent resistance correction value output from the previous iteration. In the first iteration ( )hour, The initial value is set to the reference resistance value. .

[0040] From an engineering perspective, the fluctuation damping coefficient The value of directly affects the balance between the conservatism of the iterative behavior and the convergence speed: When the value is large, even slight fluctuations will significantly suppress the correction step size, making the iteration process more robust but the convergence speed slower. It is suitable for scenarios where temperature measurement points are sparsely distributed and temperature data has high noise. When the value is small, the suppression effect of fluctuation on the step size is weakened, and the iteration convergence speed is faster. However, there is a risk of oscillation when the data quality is poor. It is suitable for scenarios with densely distributed temperature measurement points and high-quality temperature data. In a typical 10kV cable branch box, with 4 to 8 circuits and 8 to 20 temperature measurement points... Pick to A good balance can be achieved between convergence speed and stability.

[0041] S6. Determine the iterative convergence of the equivalent resistance correction value and output the convergent equivalent resistance. The core purpose of this step is to terminate the iterative loop through the convergence criterion and use the equivalent resistance correction value that meets the accuracy requirements as the equivalent resistance output of the converged state. This output value is the estimated value of the true equivalent resistance of the target verification point in the thermoelectric coupling equilibrium state.

[0042] Specifically, calculate the equivalent resistance correction value for the current round. The equivalent resistance correction value from the previous round The absolute value of the difference between them: The absolute value of the difference is compared with the preset convergence threshold. Compare. Convergence threshold. The accuracy is determined by multiplying the reference resistance value of the target verification contact with the preset accuracy ratio. In the formula The preset precision ratio typically has a range of values. to The specific value depends on the accuracy requirements of the verification purpose. For routine condition assessments, Desirable For high-precision verification scenarios, Desirable .

[0043] like If the iteration has converged, the equivalent resistance value for the current round is adjusted. As the equivalent resistance of the convergent state Output. The equivalent resistance of this convergent state. The true equivalent resistance of the target verification contact in the cable branch box under thermoelectric coupling equilibrium state can be directly used to quantitatively determine the degree of contact degradation. With reference resistance value The ratio of the two values ​​reflects the change in contact resistance relative to the initial state.

[0044] like If the iteration has not yet converged, the equivalent resistance correction value of the current round is used. Return to step S3 to execute the next iteration, utilizing the updated... Recalculate the resistance drift ratio This updates the thermoelectric coupling responsivity, driving the equivalent thermal offset and resistance correction values ​​in subsequent rounds to continue evolving until the convergence condition is met.

[0045] To prevent the iteration process from failing to converge under extreme conditions and resulting in an infinite computational loop, a maximum number of iterations is set. As a safety boundary. When the iteration round reaches... The convergence condition has not yet been met. Then the equivalent resistance correction value of the current round is used. As an approximate output, a non-converged flag is appended to indicate to the user that the result may not have achieved the expected accuracy. The value of is generally to The number of wheels is determined based on the complexity of the branch box loop and the required convergence accuracy.

[0046] This invention also proposes a thermoelectric characteristic verification system for cable branch boxes, such as... Figure 2 As shown, the system includes a data acquisition module, a topology parameter configuration module, a coupling response construction module, a thermal offset calculation module, an adaptive iterative correction module, and a convergence determination output module.

[0047] The data acquisition module is used to collect the operating current values ​​of each branch circuit within the cable branch box and the real-time temperature values ​​of each preset temperature measuring point, while also collecting the temperature and humidity values ​​of the environment surrounding the branch box. This module includes a current acquisition unit and a temperature and humidity acquisition unit. The current acquisition unit obtains the operating current value through current transformers installed on the busbars of each branch circuit. The temperature and humidity acquisition unit includes temperature sensors installed at each preset temperature measuring point inside the branch box and an ambient temperature and humidity sensor installed outside the branch box.

[0048] The topology parameter configuration module is used to obtain the reference resistance value corresponding to each branch circuit, determine the topology association parameters between each temperature measurement point and the target verification contact, and calculate the path effectiveness factor corresponding to each temperature measurement point based on the topology association parameters. This module internally stores the electrical topology information of the branch box and the historical test data of each contact, and completes the calculation of the topology association parameters and the generation of the path effectiveness factor based on the above information.

[0049] The coupling response construction module is used to construct the load deviation based on the operating current values ​​of each branch circuit, the resistance drift ratio based on the equivalent resistance correction value, and the damp heat stress factor based on the ambient temperature and humidity values. The three are then multiplied to obtain the thermoelectric coupling responsivity. This module receives the current value and ambient temperature and humidity values ​​output from the data acquisition module as input, and simultaneously receives the equivalent resistance correction value from the adaptive iterative correction module for updating the resistance drift ratio.

[0050] The thermal offset calculation module is used to calculate the equivalent thermal offset by multiplying the normalized temperature difference of each temperature measurement point by the corresponding path validity factor and summing the results based on the thermoelectric coupling responsivity. This module receives the thermoelectric coupling responsivity output by the coupling response construction module, the temperature values ​​of each temperature measurement point output by the data acquisition module, and the path validity factor output by the topology parameter configuration module, and performs a weighted summation operation.

[0051] The adaptive iterative correction module calculates the sliding window fluctuation of the equivalent thermal offset, determines the adaptive correction step size based on the equivalent thermal offset and the sliding window fluctuation, and incrementally corrects the equivalent resistance correction value using the adaptive correction step size. Internally, this module maintains a length of... A sliding window buffer is used to store the equivalent hot offset sequence of the most recent round, and the volatility and correction step size are updated in each round of iteration.

[0052] The convergence determination output module determines whether the absolute value of the difference between the equivalent resistance correction values ​​of adjacent iterations is less than a preset convergence threshold. If convergence fails, the current equivalent resistance correction value is fed back to the coupled response construction module to execute the next iteration. If convergence occurs, the converged equivalent resistance is output. This module also monitors whether the number of iterations exceeds the maximum iteration limit. If the limit is exceeded, an approximate result is output along with additional marking information.

[0053] The data flow relationship between the above six modules is as follows: the data acquisition module transmits the original current value, temperature value, and ambient temperature and humidity value to the coupled response construction module and the thermal offset calculation module, respectively; the topology parameter configuration module transmits the reference resistance value and path validity factor to the thermal offset calculation module and the adaptive iterative correction module; the coupled response construction module transmits the thermoelectric coupling responsivity to the thermal offset calculation module; the thermal offset calculation module transmits the equivalent thermal offset to the adaptive iterative correction module; the adaptive iterative correction module transmits the equivalent resistance correction value to the convergence determination output module, and when convergence fails, feeds back the equivalent resistance correction value to the coupled response construction module through the convergence determination output module, forming a complete iterative closed-loop data path.

Claims

1. A method for verifying the thermoelectric characteristics of a cable branch box, characterized in that: Includes the following steps: S1 collects the operating current value of each branch circuit in the cable branch box and the real-time temperature value of each preset temperature measuring point, and at the same time collects the temperature and humidity values ​​of the environment where the branch box is located. S2, obtain the reference resistance value corresponding to each branch circuit, determine the topology correlation parameters between each temperature measurement point and the target verification point, and calculate the path effectiveness factor corresponding to each temperature measurement point based on the topology correlation parameters. S3, construct the load deviation degree based on the deviation between the operating current value and the rated value of each branch circuit, construct the resistance drift ratio based on the ratio of the equivalent resistance correction value output by the previous iteration to the reference resistance value, construct the damp heat stress factor based on the normalized values ​​of ambient temperature and humidity, and multiply the load deviation degree, resistance drift ratio and damp heat stress factor to obtain the thermoelectric coupling response degree of the current cycle. S4. Based on the thermoelectric coupling responsivity, the normalized difference between the real-time temperature value and the reference temperature value of each temperature measurement point is multiplied by the corresponding path validity factor and then summed to obtain the equivalent thermal offset of the current round. S5, calculate the sliding window fluctuation of the equivalent thermal offset in the most recent preset round, determine the adaptive correction step size based on the equivalent thermal offset and the sliding window fluctuation, and incrementally correct the equivalent resistance correction value of the previous iteration with the adaptive correction step size to obtain the equivalent resistance correction value of the current round. S6, determine whether the absolute value of the difference between the equivalent resistance correction value of the current round and the equivalent resistance correction value of the previous round is less than the preset convergence threshold. If not, return to S3 with the equivalent resistance correction value of the current round to execute the next iteration. If yes, output the equivalent resistance correction value of the current round as the converged equivalent resistance. The converged equivalent resistance characterizes the true equivalent resistance of the target verification contact of the cable branch box in the thermoelectric coupling equilibrium state.

2. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 1, characterized in that: In S3, the formula for calculating the load deviation is: In the formula, The total number of branch loops, For the first The operating current value of each branch circuit. For the first The rated current value of each branch circuit. For the first The weighting coefficient of each branch circuit is determined based on the rated capacity ratio of each branch circuit.

3. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 2, characterized in that: In S3, the formula for calculating the damp heat stress factor is: In the formula, This is the ambient temperature value. The preset reference temperature value, This represents the ambient humidity value. The thermoelectric coupling responsivity is set to a preset reference humidity value. The calculation formula is: In the formula, This is the resistance drift ratio. , This is the equivalent resistance correction value output from the previous iteration. This is the reference resistance value.

4. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 1, characterized in that: In S4, the formula for calculating the equivalent thermal offset is: In the formula, For the current iteration round, The thermoelectric coupling responsivity for the current round, This represents the total number of temperature measurement points. For the first Real-time temperature values ​​at each temperature measurement point For reference temperature value, For the first The path effectiveness factor corresponding to each temperature measurement point is in the form of a saturated function: In the formula, For the first Topological association parameters between each temperature measurement point and the target verification point This is the preset saturation adjustment constant.

5. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 1, characterized in that: In S5, the formula for calculating the sliding window volatility is: In the formula, The preset window length, For the most recent The arithmetic mean of the wheel's equivalent thermal offset; the formula for calculating the adaptive correction step size is: In the formula, The reference resistance value, The preset volatility damping coefficient; the equivalent resistance correction value for the current round is:

6. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 5, characterized in that: In S5, when the iteration round Less than window length At that time, the sliding window fluctuation is based on the actual completed... The equivalent thermal offset is calculated using the window length as... Alternative .

7. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 1, characterized in that: In S2, each temperature measuring point is arranged at intervals along the heat conduction path of each branch circuit in the branch box. The topology correlation parameter is determined based on the equivalent thermal resistance length of the heat conduction path traversed between each temperature measuring point and the target verification point in the electrical topology. The shorter the heat conduction path, the larger the topology correlation parameter.

8. The method for verifying the thermoelectric characteristics of a cable branch box according to claim 1, characterized in that: In S6, the preset convergence threshold is determined by the product of the reference resistance value of the target verification contact and the preset accuracy ratio; the method also sets a maximum number of iterations. If the convergence condition is not met when the maximum number of iterations is reached, the equivalent resistance correction value of the current iteration is used as an approximate output and the non-converged state is marked.

9. A thermoelectric characteristic verification system for a cable branch box, characterized in that: include: The data acquisition module is used to collect the operating current value of each branch circuit in the cable branch box and the real-time temperature value of each preset temperature measuring point, as well as the temperature and humidity value of the environment where the branch box is located. The topology parameter configuration module is used to obtain the reference resistance value corresponding to each branch circuit, determine the topology association parameters between each temperature measurement point and the target verification point, and calculate the path effectiveness factor corresponding to each temperature measurement point based on the topology association parameters. The coupling response construction module is used to construct the load deviation degree based on the operating current value of each branch circuit, the resistance drift ratio based on the equivalent resistance correction value, and the damp heat stress factor based on the ambient temperature and humidity values. The three are then multiplied together to obtain the thermoelectric coupling response degree. The thermal offset calculation module is used to sum the normalized temperature difference of each temperature measurement point by multiplying it by the corresponding path validity factor based on the thermoelectric coupling responsivity, and then obtain the equivalent thermal offset. The adaptive iterative correction module is used to calculate the sliding window fluctuation of the equivalent thermal offset, determine the adaptive correction step size based on the equivalent thermal offset and the sliding window fluctuation, and perform incremental correction on the equivalent resistance correction value with the adaptive correction step size. The convergence determination output module is used to determine whether the absolute value of the difference between the equivalent resistance correction values ​​of adjacent rounds is less than the preset convergence threshold. If convergence is not achieved, the current equivalent resistance correction value is fed back to the coupling response construction module to execute the next round of iteration. If convergence is achieved, the converged equivalent resistance is output.

10. The thermoelectric characteristic verification system for cable branch boxes according to claim 9, characterized in that: The data acquisition module includes a current acquisition unit and a temperature and humidity acquisition unit. The current acquisition unit obtains the operating current value through the current transformer installed on the busbar of each branch circuit. The temperature and humidity acquisition unit includes temperature sensors respectively set at each preset temperature measurement point inside the branch box and an ambient temperature and humidity sensor set outside the branch box.

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