Copper busbar connection status detection method and system

Abstract

The present invention discloses a method and system for detecting the connection status of a copper busbar, which specifically relates to the technical field of copper busbar status detection and is used to solve the problem of poor early identification of copper busbar connection degradation. The present invention synchronously measures the resistance and temperature rise of the copper busbar connection during load changes, combines finite difference filtering to achieve signal denoising, and captures the evolution of connection characteristics. Based on real-time load change events, an analysis window is determined, a thermoelectric trajectory point set is constructed and the load rise and fall periods are divided to form a continuous dynamic thermoelectric response curve. The temperature rise and cooling trajectories are divided according to the temperature change trend, the resistance drift and the hysteresis loop area are extracted, the connection degradation trend and structural fatigue characteristics are identified, and the connection status information caused by thermal stress and thermal cycle asymmetry is obtained during the load change period. The detection strategy is adjusted according to the analysis results, thereby performing early degradation identification and intelligent risk grading of the copper busbar connection status, thereby improving the sensitivity and accuracy of copper busbar detection.

Description

Technical Field

[0001] The present invention relates to the technical field of copper busbar status detection, and more particularly, to a method and system for detecting the connection status of a copper busbar. Background Art

[0002] Copper busbars, as crucial electrical connection components in power transmission and distribution systems, are widely used in substations, distribution cabinets, power equipment, and large-scale industrial electrical systems to transmit and distribute high currents. Due to copper's excellent electrical conductivity, corrosion resistance, and machinability, copper busbars can effectively reduce energy loss and improve the overall efficiency and reliability of electrical systems. Copper busbar connections are typically achieved through bolt crimping, welding, or plug-in connections. The contact resistance, mechanical strength, and thermal stability of the connection directly impact the performance and safety of the entire electrical system. Ideally, copper busbar connections should maintain low and stable contact resistance to minimize voltage drop and heat generation during power transmission.

[0003] Deficiencies in existing technologies: In existing copper busbar connection status detection technologies, the connection status is usually evaluated mainly by the absolute change of single-point contact resistance, temperature rise monitoring or periodic visual inspection. However, static detection based solely on resistance value cannot effectively reflect the degradation evolution process of the connection under dynamic thermal stress, and cannot timely capture the cumulative trend of resistance drift and local abnormal fluctuations, resulting in early creep degradation and contact voltage drop anomalies being difficult to identify in a timely manner. Secondly, there is a lack of systematic analysis of the hysteresis characteristics and stability changes of the connection structure during the complete thermal cycle, and it is impossible to quantify the path asymmetry and structural fatigue accumulation during heating and cooling, thereby missing the early warning of potential fatigue instability risks of the connection. There is a lack of a systematic judgment mechanism for the dual characteristics of dynamic degradation behavior and structural stability degradation, resulting in insufficient accuracy and pertinence in the copper busbar connection status assessment results. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and system for detecting the connection status of a copper busbar, so as to solve the problem of poor early identification of copper busbar connection degradation in the above-mentioned background art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for detecting the connection status of a copper busbar comprises the following steps:

[0007] During load changes, the contact resistance of the copper busbar connection is measured. At the same time, a high-precision temperature sensor is placed in the connection area to synchronously collect the local temperature rise signal. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals.

[0008] Based on real-time monitoring of load change events, the analysis window is determined and synchronous data is intercepted. The synchronous data is used to construct a thermoelectric trajectory point set, and the load rise and fall period is determined to form a continuous thermoelectric dynamic trajectory;

[0009] The temperature change trend is divided into heating and cooling segments. The resistance drift during the load increase in the heating segment is extracted to determine the degradation trend of the copper busbar connection. The hysteresis loop area is extracted from the complete thermal cycle trajectory to determine the status during the load change.

[0010] During load changes, the connection status information generated during thermal stress and thermal cycling is obtained and analyzed, and the detection strategy is adjusted based on the connection status analysis results.

[0011] In a preferred embodiment, the contact resistance of the copper busbar connection is measured during the load change process, and a high-precision temperature sensor is deployed in the connection area to synchronously collect the local temperature rise signal. The noise is eliminated by finite difference filtering, and the resistance and temperature signals are aligned. The specific process is as follows:

[0012] Input a constant current to the copper busbar that does not affect the main current of the copper busbar, and collect a small voltage drop at both ends of the copper busbar to determine the contact resistance of the copper busbar;

[0013] Place high-precision thermocouples or temperature sensors in the copper busbar connection area to collect local temperature raw signals at the copper busbar connection. The collected local temperature raw signals are normalized to obtain the effective temperature.

[0014] The contact resistance and local temperature data are merged into a unified synchronous data frame, which includes the copper busbar connection contact resistance, the copper busbar connection local temperature and a unified timestamp;

[0015] Adaptive bidirectional finite difference filtering is used to filter out noise from each component in the synchronous data frame.

[0016] In a preferred embodiment, based on real-time monitoring of load change events, an analysis window is determined and synchronous data is intercepted. The synchronous data is used to construct a thermoelectric trajectory point set, and the load rise and fall period is determined to form a continuous thermoelectric dynamic trajectory. The specific process is as follows:

[0017] Detect load change events in real time, intercept the corresponding dynamic response analysis window, and monitor the main current I main (t), detect the current change rate and calculate the first-order derivative of the current change dI main / dt, when the following conditions are met, it is determined to be the starting point of load change t s : where δ I is the current change rate threshold;

[0018] Set the load change analysis window length T win , intercept the data frames collected synchronously within the interval;

[0019] From the analysis window [t s , t s +T win ], extract the smoothed synchronous data at each moment in, For a synchronized resistor sequence, is a synchronized temperature series;

[0020] The synchronized resistance series is used as the vertical axis and the synchronized temperature series is used as the horizontal axis to construct the thermoelectric trajectory point set: C is a set of resistance and temperature trajectory points, which is used to describe the continuous thermoelectric dynamic response process;

[0021] The minimum and maximum values ​​of the temperature series within the current load change window are calculated, and the minimum and maximum values ​​of the resistance series are normalized to obtain the trajectory point set of temperature and resistance.

[0022] In a preferred embodiment, the temperature rise and temperature fall trajectories are divided according to the temperature change trend. The specific steps are as follows:

[0023] The trajectory point set is divided into temperature rising section and temperature falling section according to the load thermal response cycle;

[0024] If the temperature difference between the current moment and the next moment is greater than zero, the temperature is increasing positively, and the time period is determined to be a heating period. If the temperature difference is less than zero, that is, the temperature is decreasing, it is determined to be a cooling period.

[0025] In a preferred embodiment, the resistance drift during the load increase period is extracted in the temperature rise stage to determine the degradation trend of the copper busbar connection. The hysteresis loop area is extracted from the complete thermal cycle trajectory to determine the state during the load change period. The specific process is as follows:

[0026] According to the normalized temperature signal T norm (t i )Calculate the temperature change rate ΔT(t i ):ΔT(t i )=T norm (t i+1 )-T norm (t i ), where T norm (t i+1 ) represents t i+1 time;

[0027] Define the segmentation rule: If ΔT(t i )>0, it is determined to be the load rising section; if ΔT(ti )<0, it is determined to be a load reduction section;

[0028] Divide the trajectory point set according to the segmentation rule to obtain the load increase segment set and the load decrease segment set;

[0029] The load rise and load fall trajectories will be extracted and analyzed in sections to determine the response characteristics of the copper busbar connection at different stages of thermal stress changes.

[0030] In the load rising section, extract the normalized resistance signal R norm (t i ), and defines resistance drift as an integral measure of resistance change during load increase;

[0031] The resistance drift is defined as: Among them, T up is the load rise time, which is obtained by the difference between the start and end time of the load rise segment; t s , t e are the starting and ending time of the load rising section respectively;

[0032] The hysteresis loop contour is constructed with the load rising section and the load falling section where the trajectory points are concentrated as the boundaries, and the hysteresis area A enclosed by the hysteresis loop is calculated using the discrete curve integration method. H ;

[0033] The point set of the trajectory loop arranged in ascending order of temperature is used as the hysteresis area: Where N is the total number of trajectory points.

[0034] In a preferred embodiment, the connection status information generated during the thermal stress and thermal cycle is obtained and analyzed. The specific process is as follows:

[0035] Acquiring connection status information generated during thermal stress and thermal cycling, the connection status information including resistance drift information and hysteresis response information, the resistance drift information including a thermal stress degradation dynamic index, and the hysteresis response information including a thermal cycling asymmetric stability index;

[0036] The thermal stress degradation dynamic index indicates the resistance change of the copper busbar connection caused by thermal stress during load increase;

[0037] The thermal cycle asymmetric stability index indicates the asymmetry and stability of the copper busbar connection after it undergoes a complete load heating and cooling cycle.

[0038] The thermal stress degradation dynamic index is compared with the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is compared with the thermal cycle asymmetric stability threshold.

[0039] In a preferred embodiment, the detection strategy is adjusted according to the connection status analysis result. The specific process is as follows:

[0040] The thermal stress degradation dynamic index is compared with the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is compared with the thermal cycle asymmetric stability threshold. Based on the comparison results, four situations are divided and different strategy adjustments are made;

[0041] In the first scenario, if the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is also less than or equal to the thermal cycle asymmetric stability threshold, then the regular inspection cycle is maintained and monitoring is performed according to the normal inspection plan. There is no need to increase the maintenance frequency or take additional intervention measures.

[0042] In the second case, if the thermal stress degradation dynamic index is greater than the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is still less than or equal to the thermal cycle asymmetric stability threshold, the subsequent detection period is shortened, drift trend tracking is increased, and local connection inspections are arranged;

[0043] In the third case, if the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is greater than the thermal cycle asymmetric stability threshold, accelerated inspection measures are taken to check the connection crimping status, bolt tightening condition, and physical condition of the contact interface;

[0044] In the fourth case, if the thermal stress degradation dynamic index is greater than the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is greater than the thermal cycle asymmetric stability, then the machine should be shut down for maintenance immediately, and the severely degraded connection parts should be checked and replaced, and the surrounding copper busbar connection units should be checked simultaneously.

[0045] A copper busbar connection status detection method system, used to implement the above copper busbar connection status detection method, comprising:

[0046] The copper busbar connection data acquisition module is used to measure the contact resistance of the copper busbar connection during load changes. At the same time, high-precision temperature sensors are deployed in the connection area to synchronously collect local temperature rise signals. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals.

[0047] Thermoelectric trajectory determination module is used to determine the analysis window and intercept the synchronous data based on the real-time monitoring of load change events, construct the thermoelectric trajectory point set from the synchronous data, and determine the load rise and fall period to form a continuous thermoelectric dynamic trajectory;

[0048] The load trend determination module is used to divide the temperature change trend into the heating and cooling segments. In the heating segment, the resistance drift during the load increase is extracted to determine the degradation trend of the copper busbar connection. In the complete thermal cycle trajectory, the hysteresis loop area is extracted to determine the status during the load change.

[0049] The strategy adjustment module is used to obtain and analyze the connection status information generated during the thermal stress and thermal cycle process during the load change period, and adjust the detection strategy according to the connection status analysis results.

[0050] Technical effects and advantages of the present invention:

[0051] The present invention synchronously measures the contact resistance and local temperature rise signal at the copper busbar connection during the load change process, and combines finite difference filtering to achieve signal denoising and time alignment. It can accurately capture the evolution of the microscopic characteristics of the connection interface, determine the analysis window based on real-time load change events, construct a thermoelectric trajectory point set and divide the load rise and fall periods to form a continuous dynamic thermo-electric response curve, and realize continuous tracking of the entire process of thermal disturbance of the connection. The temperature change trend is divided into heating and cooling trajectories, and the resistance drift and hysteresis loop area are extracted. It can systematically identify the connection degradation trend and structural fatigue characteristics, and further obtain the connection status information caused by thermal stress and thermal cycle asymmetry during the load change period. The detection strategy is dynamically adjusted according to the analysis results to realize early degradation identification and intelligent risk grading of the copper busbar connection status, improve the detection sensitivity and accuracy, and enhance the dynamic perception capability of the healthy evolution process of the connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The present invention is a flow chart of a copper busbar connection status detection method.

[0053] Figure 2 The figure is a structural diagram of a copper busbar connection status detection method system of the present invention. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] Example 1: Figure 1 As shown, a method for detecting the connection status of a copper busbar includes the following steps:

[0056] During load changes, the contact resistance of the copper busbar connection is measured. At the same time, a high-precision temperature sensor is placed in the connection area to synchronously collect the local temperature rise signal. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals.

[0057] Based on real-time monitoring of load change events, the analysis window is determined and synchronous data is intercepted. The synchronous data is used to construct a thermoelectric trajectory point set, and the load rise and fall period is determined to form a continuous thermoelectric dynamic trajectory;

[0058] The temperature change trend is divided into heating and cooling segments. The resistance drift during the load increase in the heating segment is extracted to determine the degradation trend of the copper busbar connection. The hysteresis loop area is extracted from the complete thermal cycle trajectory to determine the status during the load change.

[0059] During load changes, the connection status information generated during thermal stress and thermal cycling is obtained and analyzed, and the detection strategy is adjusted based on the connection status analysis results.

[0060] During copper busbar connection status inspection, changes in electrical performance at the connection are affected by a variety of factors. Among these, changes in microscopic contact characteristics caused by thermal stress are a significant and often overlooked evolutionary process. When the copper busbar is operating under high load, the current flowing through it causes the body temperature to rise. Thermal expansion and stress changes occur at the copper busbar itself and its connection points, leading to dynamic drift in contact resistance. Therefore, it is necessary to synchronously and continuously collect resistance changes and local temperature changes at the copper busbar connection, establish a dynamic thermal-electrical correlation, and accurately identify early signs of connection degradation.

[0061] Step 1: Synchronously collect the copper busbar contact resistance and local temperature data. The specific steps are as follows:

[0062] The contact resistance at the copper busbar terminal is the most direct electrical parameter for evaluating the health of the connection. Deterioration of the connection (such as looseness or oxidation) usually first manifests as a slight increase in contact resistance.

[0063] Using a perturbation excitation injection mechanism, a small constant current is injected without affecting the main current transmission of the copper busbar, and a small voltage drop is collected at both ends of the copper busbar connection to infer the contact resistance;

[0064] The excitation current must be much smaller than the copper busbar main current to avoid disturbances. The differential voltage acquisition unit uses a high common-mode rejection ratio amplifier design to suppress the noise introduced by the large current main circuit. At the same time, the sampling frequency is set to be greater than 10 times the main frequency component of the load change frequency, usually 10Hz to 50Hz.

[0065] The real-time contact resistance calculation uses the modified Ohm's law expression: Among them, R c(t) is the instantaneous copper busbar contact resistance at time t; V c (t) is the voltage difference collected at both ends of the copper busbar at time t; I c is the constant small excitation current applied.

[0066] Normalize the synchronously collected data of the copper busbar's local temperature. Place a high-precision thermocouple or PT100 temperature sensor at the copper busbar joint area. Select a surface area within 5-10mm from the center of the connecting bolt as the temperature measurement base point. After the sensor output signal is processed by the preamplifier and temperature drift compensation module, the local temperature signal is collected.

[0067] The collected local temperature original signal is normalized by temperature drift to calculate the effective temperature: T s (t) = T raw (t)-T env (t)+T ref , where T s (t) is the standardized local temperature of the copper busbar connection at time t, T raw (t) is the original collected temperature value T at time t env (t) is the ambient background temperature, T ref Setting reference temperature for detection system;

[0068] After normalization, the local temperature signal eliminates environmental interference and can reflect the temperature evolution of the copper busbar connection under the action of current-carrying thermal stress.

[0069] A unified system clock is set, using the IEEE 1588 high-precision time synchronization protocol to ensure that all acquisition units operate with the same time base. At each time point t, the contact resistance and local temperature data are merged into a unified synchronized data frame. The synchronized data frame includes the copper busbar contact resistance, the copper busbar local temperature, and a unified timestamp.

[0070] Adaptive bidirectional finite difference filtering is used to process each component in the synchronization data frame separately to suppress high-frequency noise components while avoiding excessive signal filtering that causes loss of dynamic response. The filtering formula is: Where X(t) represents any component of contact resistance or local effective temperature rise; is the smoothed signal, X(t) is the original signal, and Δt is the sampling interval.

[0071] It should be noted that the finite difference form needs to maintain the first-order perturbation characteristics, not erase short-term mutations, and the smoothing window is fixed to the current sampling point and one point before and after it to ensure low latency.

[0072] During actual load operation, the copper busbar connection experiences dynamic local temperature fluctuations due to Joule heating induced by current fluctuations, resulting in slight drift in contact resistance. This change is not only directly related to the load level but is also modulated by microscopic contact surface changes caused by thermal stress. Therefore, it is necessary to capture the dynamic response trajectory of the copper busbar's resistance and temperature during load fluctuations within the test cycle and establish a characteristic curve.

[0073] Step 2: Establish the dynamic trajectory of resistance and temperature during load changes. The specific steps are as follows:

[0074] Detect load change events in real time, intercept the corresponding dynamic response analysis window, and monitor the main current I main (t), detect the current change rate and calculate the first-order derivative of the current change dI main / dt, when the following conditions are met, it is determined to be the starting point of load change t s : where δ I is the current change rate threshold;

[0075] Set the load change analysis window length T win , intercept the data frames collected synchronously within the interval;

[0076] During load changes, the resistance of the copper busbar connection changes with temperature in a certain pattern. Under normal connection conditions, the resistance change trend is highly consistent with the temperature rise change trend. However, when the connection deteriorates, the resistance change trajectory with temperature will show abnormal phenomena such as nonlinear drift and hysteresis.

[0077] From the analysis window [t s , t s +T win ], extract the smoothed synchronous data at each moment

[0078] The resistor sequence that will be synchronized As the vertical axis, the synchronized temperature series As the horizontal axis, construct the thermoelectric trajectory point set: C is the set of resistance and temperature trajectory points, describing the continuous thermoelectric dynamic response process;

[0079] Calculate the minimum and maximum values ​​of the temperature sequence within the current load change window, and normalize the minimum and maximum values ​​of the resistance sequence to obtain the trajectory point set of temperature and resistance;

[0080] The trajectory point set is divided into a heating section and a cooling section according to the load thermal response cycle. If the temperature difference between the current moment and the next moment is greater than zero, that is, the temperature is increasing positively, then the time period is judged to be a heating section. If the temperature difference is less than zero, that is, the temperature is decreasing, then it is judged to be a cooling section.

[0081] In the copper busbar connection status detection, load changes (i.e., current changes) directly lead to copper busbar temperature changes. The operating current in the copper busbar main circuit is monitored in real time to construct a time series of the main current. The first-order difference or derivative signal of this sequence is calculated to obtain a current change rate curve. When the absolute value of this rate curve at a certain moment exceeds the preset current change rate threshold for the first time, it is considered that a significant load mutation has occurred in the system. This time point is determined to be the starting moment of the load change, that is, the starting point of the thermal response window.

[0082] The temperature rising stage (heating period) and the temperature falling stage (cooling period) correspond to the stress response of the copper busbar connection interface under different thermodynamic environments.

[0083] As the copper busbar temperature gradually rises, the connection is affected by the combined effects of thermal expansion, creep, and material softening, resulting in the most significant change in voltage drop at the contact interface. If there is slight degradation, the resistance will rise significantly, and as the copper busbar temperature drops, the connection stress will gradually release. However, if fatigue or surface degradation occurs at the connection interface, the resistance drop will lag significantly. Therefore, the trajectory data is segmented into heating and cooling periods to capture the response characteristics of these different degradation mechanisms, thereby accurately extracting drift and hysteresis characteristics.

[0084] Step 3: Extract resistance drift and hysteresis characteristic indicators. The specific steps are as follows:

[0085] According to the normalized temperature signal T norm (t i )Calculate the temperature change rate at each moment: ΔT(t i )=T norm (t i+1 )-T norm (t i ), where T norm (t i+1 ) represents t i+1 time;

[0086] Define the segmentation rule: If ΔT(t i )>0, it is determined to be the load rising section; if ΔT(t i )<0, it is determined to be a load decreasing segment; the trajectory point set is divided according to the above rules to obtain an ascending segment set and a descending segment set;

[0087] By extracting the load rising and load falling trajectories in sections, the response characteristics of the connection performance at different stages of thermal stress changes can be clearly analyzed.

[0088] During connection degradation, the resistance of the copper busbar connection will typically show an abnormal increase during load increases. Even if the temperature change amplitude is controlled, the drift reflects the degree of contact degradation or the decrease in clamping force on the connection surface. Similarly, the resistance drift during load increases is calculated as an important quantitative characteristic of the change in connection status.

[0089] In the load rising section, extract the normalized resistance signal R norm (t i ), and defines resistance drift as an integral measure of resistance change during load increase;

[0090] Assume t s , t e are the starting and ending moments of the load rising section, respectively. The resistance drift is defined as: Among them, T up is the load rise time, which is obtained by the difference between the start and end time of the load rise segment;

[0091] The resistance drift is integrated to measure the resistance change trend during the entire load increase period, which can effectively amplify small degradation signals, avoid the accidental influence of single-point measurement, and improve detection robustness.

[0092] If a significant hysteresis loop appears in the resistance and temperature traces of the copper busbar connection during the heating and cooling process, it indicates that the connection surface has plastic deformation, surface aging, or unstable compression. The size of the hysteresis area directly reflects the energy dissipation and degradation degree of the connection under thermal cycling stress.

[0093] The hysteresis loop outline is constructed with the rising and falling segments in the trajectory as the boundaries, and the hysteresis area A enclosed by the hysteresis loop is calculated using the discrete curve integration method. H ;

[0094] Assume that the point set after the trajectory loop is sorted in ascending order of temperature is used as the hysteresis area: The hysteresis area can be approximately calculated using the discrete Green's formula, where N is the total number of trajectory points. The larger the hysteresis area, the worse the connection state stability.

[0095] Step 4: Determine the connection status and output the risk classification. This involves obtaining the dynamic trajectory of the copper busbar connection resistance and temperature during load changes, analyzing the resistance drift behavior under thermal stress and the hysteresis response characteristics during thermal cycling. The specific steps are as follows:

[0096] During the connection status determination process, the resistance drift behavior under thermal stress and the hysteresis response characteristics during thermal cycling are analyzed, that is, the connection status information generated during thermal stress and thermal cycling is obtained. The connection status information includes resistance drift information and hysteresis response information. The resistance drift information includes a thermal stress degradation dynamic index, and the hysteresis response information includes a thermal cycling asymmetric stability index.

[0097] The Thermal Stress Degradation Dynamic Index (TSDI) quantifies the dynamic characteristics of resistance changes in copper busbar connections caused by thermal stress during load increases. It not only measures the cumulative resistance drift of the connection during the overall load increase, but also comprehensively reflects the instability of local resistance changes and the asymmetric evolution of drift rates between the previous and next stages. Specifically, the TSD describes the dynamic evolution of the connection interface degradation process under continuous thermal conditions by incorporating multi-dimensional information such as the cumulative resistance drift, the magnitude of the local drift change rate, and the deviation of the drift rates between the previous and next stages.

[0098] The dynamic index of thermal stress degradation directly affects the quantitative accuracy of the thermal evolution characteristics of the copper busbar connection during load increase. The higher the dynamic index of thermal stress degradation, the greater the resistance drift amplitude of the connection interface under thermal conditions, the more significant the local instability, and the more uneven the drift evolution. This indicates that there are problems such as abnormal increase in voltage drop, local contact degradation, or accumulation of creep damage at the connection interface.

[0099] The logic for obtaining the thermal stress degradation dynamic index is as follows:

[0100] Get the overall resistance drift during load ramp: in is the local drift of the temperature sampling point interval j, and the time sampling point t during the load increase period is obtained. i Normalized contact resistance value R corresponding to the moment norm (t i ) and normalized temperature value T norm (t i+1 ) and time sampling point t i+1 Normalized contact resistance R corresponding to the moment norm (t i+1 ) and normalized temperature value T norm (t i+1 ), calculate the local drift change rate, the calculation expression is: Get the maximum local drift change rate FD max (t i ) and the minimum local drift change rate FD min (t i );

[0101] Get the midpoint of load heating time t mNormalized contact resistance value R norm (t m ), obtain the normalized contact resistance value R at the load rising start time t0 norm (t0), obtain the temperature normalized to the midpoint time t during the load increase process m Normalized temperature value T norm (t m ), obtain the normalized temperature value T at the start time t0 of the load increase norm (t0), calculate the drift rate in the first half: Get the load increase end time t N Normalized contact resistance value R at norm (t N ), obtain the load increase end time t N Normalized temperature value T norm (t N ), calculate the drift rate in the second half: Calculate the thermal stress degradation dynamic index:

[0102] It should be noted that the overall resistance drift is processed during the load increase period (temperature normalization interval [0, 1]), and the resistance change trajectory is calculated. The cumulative integral of the normalized resistance change from the start to the end is calculated, and the result is obtained based on the accumulation of the hierarchical integration in the small interval. The normalized contact resistance is a standardized value obtained by normalizing the actual contact resistance of the copper busbar connection after synchronously collecting the actual contact resistance of the copper busbar connection during the load change period. It is used to eliminate the influence of different load conditions and changes in the absolute resistance magnitude on feature extraction. The normalized temperature is also the same. The drift rate in the first half represents the average growth rate of the copper busbar connection contact resistance with temperature change from the start of the load to the moment when the temperature rises to the midpoint (0.5), which measures the degradation evolution rate in the initial stage of heating. The drift rate in the second half represents the average growth rate of the contact resistance with temperature change from the temperature midpoint (0.5) to the completion of the load heating (1.0), which measures the degradation evolution rate in the later stage of heating.

[0103] The Thermal Cycling Asymmetric Stability Index (TCASI) is used to indicate the asymmetry and stability changes in the thermoelectric behavior of a copper busbar connection after undergoing a complete load heating and cooling cycle. The TCASI comprehensively measures the area of ​​the heating-cooling hysteresis loop, the path resistance range, and the offset of the hysteresis loop's center of gravity, reflecting the degree of energy loss, fatigue degradation, and geometric stability degradation of the connection interface under thermal cycling stress. Specifically, the TCASI accurately describes the irreversible degradation characteristics and the trend of increasing structural asymmetry during thermal cycling.

[0104] The thermal cycle asymmetric stability index can quantify the instability risk of connection structures under dynamic thermal environments, assist in determining early failure modes such as interface fatigue, loosening, or microcrack propagation, and improve the ability to dynamically track and classify connection reliability degradation, thus facilitating the formulation of intelligent maintenance strategies.

[0105] The thermal cycling asymmetric stability index directly affects the ability to detect structural degradation and fatigue evolution of copper busbar connections during multiple load cycles. The higher the thermal cycling asymmetric stability index, the greater the energy loss at the connection interface during heating and cooling, the more asymmetric the path resistance change, and the more obvious the geometric stability offset of the hysteresis loop, reflecting the presence of irreversible fatigue damage, loosening, or microcrack propagation within the connection interface. When the thermal cycling asymmetric stability index continues to rise and exceeds the preset safety range, it usually means that the connection has experienced serious structural stability degradation. Risk intervention or local structural reinforcement should be carried out in a timely manner in combination with the operation strategy to avoid cascading failures of the electrical system or the expansion of safety hazards due to connection fatigue damage.

[0106] The logic for obtaining the thermal cycling asymmetric stability index is as follows:

[0107] Obtain the heating and cooling paths during the thermal cycle, obtain the average value of all temperature sampling points in the heating path, and calculate the temperature center of the heating path: in, For the temperature of the i-th sampling point of the heating path, calculate the resistance center: in, is the normalized contact resistance value corresponding to the temperature of the i-th sampling point in the heating path;

[0108] Similarly, obtain the average value of all temperature sampling points in the cooling path and calculate the temperature center of the cooling path: in, For the temperature of the i-th sampling point in the cooling path, calculate the resistance center: in, is the normalized contact resistance value corresponding to the temperature of the i-th sampling point in the cooling path; the center of gravity offset of the hysteresis loop is calculated:

[0109] Obtain the resistance and temperature data trace of the copper busbar connection in a complete thermal cycle, and process all the resistance values ​​of the cooling path to obtain the trace resistance value: Among them, R min 、R max is the minimum resistance value and the maximum resistance value in the entire thermal cycle window; the thermal cycle asymmetric stability index is calculated, and the calculation expression is:

[0110] It should be noted that the heating path refers to the temperature trajectory of the resistor connected to the copper busbar during temperature rise, and is recorded as the upward trajectory. The cooling path is the temperature trajectory of the resistor connected to the copper busbar during temperature drop, and is recorded as the downward trajectory. The geometric center of gravity of each segment of the trajectory is the center position of the segment in the temperature resistor thermoelectric plane. For the heating path, the coordinates of this center position are the temperature center of the horizontal axis and the resistance center of the vertical axis.

[0111] A dynamic threshold for thermal stress degradation is set to quantitatively assess and classify the dynamic evolution of resistance drift in copper busbar connections under thermal stress during load increase. Because the changing trend of contact resistance under thermal stress can sensitively reflect early degradation phenomena such as abnormal voltage drop at the connection interface, material creep, and microscopic contact interface degradation, a scientifically sound dynamic threshold for thermal stress degradation is required to categorize the connection status into healthy and abnormal.

[0112] Setting a thermal cycle asymmetric stability threshold quantitatively assesses and identifies risks related to the hysteresis characteristics of the thermoelectric response and structural stability of the copper busbar connection during a complete load heating and cooling cycle. Copper busbar connections are susceptible to the cumulative effects of fatigue, residual creep, and local loosening in long-term thermal cycling environments, leading to asymmetric changes in the thermal cycle path, such as an increase in hysteresis loop area, increased path resistance differences, and overall geometric structure shifts. By setting a thermal cycle asymmetric stability threshold, potential risk connection units can be identified in advance before macroscopic slip or fatigue damage occurs in the connection structure, guiding targeted maintenance decisions.

[0113] Based on the relative levels of the thermal stress degradation dynamic index and the thermal cycle asymmetric stability index relative to these two thresholds, four typical scenarios are classified. Each scenario corresponds to different judgments and strategy adjustments:

[0114] In the first scenario, the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, and the thermal cycling asymmetric stability index is also less than or equal to the thermal cycling asymmetric stability threshold. In this case, the overall resistance drift of the copper busbar connection under thermal stress is small, and no obvious hysteresis asymmetry is exhibited after thermal cycling, indicating that the connection interface is in a relatively stable operating state. In terms of degradation characteristics, the overall resistance changes steadily with temperature rise, with no local sudden drift or rate anomalies. The heating and cooling paths basically overlap on the resistance temperature plane, the hysteresis loop area is small, and the loop center of gravity offset is not obvious. In this case, the project risk assessment is low risk, the connection reliability is high, and there is no current failure risk. It is recommended to maintain regular inspection cycles and monitor according to the normal inspection plan. There is no need to increase maintenance frequency or take additional intervention measures.

[0115] In the second case, the thermal stress degradation dynamic index is greater than the thermal stress degradation dynamic threshold, while the thermal cycle asymmetric stability index is still less than or equal to the thermal cycle asymmetric stability threshold. This situation indicates that the resistance drift of the copper busbar connection is large under the action of thermal stress, and the overall degradation trend has initially appeared, but the path is still basically symmetrical during the heating and cooling process, and the hysteresis phenomenon has not significantly expanded. This state shows that the connection interface is affected by thermal stress, resulting in material expansion and changes in the microscopic contact interface, forming an overall abnormal voltage drop trend, but structural fatigue has not yet occurred. The degradation characteristics are manifested as a continuous upward trend in overall resistance with rising temperature, and there is a phenomenon of accelerated drift rate changes in some areas, but the hysteresis loop is still regular as a whole. The engineering risk assessment belongs to the medium risk level. If it continues to operate without intervention, it may enter the accelerated degradation stage. It is recommended to appropriately shorten the subsequent detection cycle, increase drift trend tracking, and arrange local connection inspections at appropriate times. If necessary, restore the connection crimping force or clean the contact surface to prevent further deterioration;

[0116] In the third case, the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, while the thermal cycle asymmetric stability index is greater than the thermal cycle asymmetric stability threshold. This indicates that the overall resistance change trend of the copper busbar connection has not drifted significantly, but the hysteresis path area expands and the loop asymmetry intensifies under the action of thermal cycling, reflecting the accumulation of thermal fatigue or local slip at the connection interface. The degradation characteristics are that the overall resistance change amplitude is small, but the resistance response at the same temperature in the heating and cooling stages shows obvious separation, the hysteresis area increases significantly, and the center of gravity of the loop shifts significantly. The engineering risk assessment shows that there are medium to high risks at the connection interface. The main hidden danger is local structural loosening caused by fatigue. Long-term operation may cause mechanical instability or local failure. It is recommended to take accelerated inspection measures to check the connection crimping status, bolt tightening status and physical state of the contact interface. If necessary, local re-crimping or protective treatment should be taken to curb the fatigue expansion trend.

[0117] In the fourth scenario, both the thermal stress degradation dynamic index and the thermal cycle asymmetric stability index are greater than their respective set thresholds, indicating the most severe comprehensive instability state. In this case, the copper busbar connection exhibits drastic resistance drift under thermal stress. At the same time, the hysteresis area increases significantly during thermal cycling, the loop asymmetry is significant, the center of gravity shifts severely, and the overall structural response is abnormal. Degradation characteristics include drastic resistance changes, unstable drift rates, significant hysteresis path shifts, and overall loop position migration, indicating that the connection interface has lost its thermal stability. The engineering risk assessment identifies it as a high-risk or even extremely high-risk state, which may cause serious accidents such as functional failure, local overheating, melting, or electrical disconnection at any time. In such cases, immediate shutdown and maintenance should be arranged, with priority given to inspecting and replacing severely degraded connection parts. At the same time, surrounding connection units should be checked simultaneously, and a more stringent follow-up maintenance and monitoring plan should be formulated to prevent the spread of similar faults.

[0118] The present invention synchronously measures the contact resistance and local temperature rise signal at the copper busbar connection during the load change process, and combines finite difference filtering to achieve signal denoising and time alignment. It can accurately capture the evolution of the microscopic characteristics of the connection interface, determine the analysis window based on real-time load change events, construct a thermoelectric trajectory point set and divide the load rise and fall periods to form a continuous dynamic thermo-electric response curve, and realize continuous tracking of the entire process of thermal disturbance of the connection. The temperature change trend is divided into heating and cooling trajectories, and the resistance drift and hysteresis loop area are extracted. It can systematically identify the connection degradation trend and structural fatigue characteristics, and further obtain the connection status information caused by thermal stress and thermal cycle asymmetry during the load change period. The detection strategy is dynamically adjusted according to the analysis results to realize early degradation identification and intelligent risk grading of the copper busbar connection status, improve the detection sensitivity and accuracy, and enhance the dynamic perception capability of the healthy evolution process of the connection.

[0119] Example 2: A copper busbar connection status detection method system, such as Figure 2 As shown, specifically including:

[0120] The copper busbar connection data acquisition module is used to measure the contact resistance of the copper busbar connection during load changes. At the same time, high-precision temperature sensors are deployed in the connection area to synchronously collect local temperature rise signals. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals.

[0121] Thermoelectric trajectory determination module is used to determine the analysis window and intercept the synchronous data based on the real-time monitoring of load change events, construct the thermoelectric trajectory point set from the synchronous data, and determine the load rise and fall period to form a continuous thermoelectric dynamic trajectory;

[0122] The load trend determination module is used to divide the temperature change trend into the heating and cooling segments. In the heating segment, the resistance drift during the load increase is extracted to determine the degradation trend of the copper busbar connection. In the complete thermal cycle trajectory, the hysteresis loop area is extracted to determine the status during the load change.

[0123] The strategy adjustment module is used to obtain and analyze the connection status information generated during the thermal stress and thermal cycle process during the load change period, and adjust the detection strategy according to the connection status analysis results.

[0124] The above formulas are all dimensionless and calculated numerically. Specific dimension removal can be achieved by various means such as standardization, which will not be elaborated here. The formula is a formula obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0125] The above embodiments can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center by wired or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (e.g., a floppy disk, an ATA hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state ATA hard disk.

[0126] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0127] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0128] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0129] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment as needed.

[0130] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0131] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for detecting the connection status of a copper busbar, characterized in that: The steps include: During load changes, the contact resistance of the copper busbar connection is measured. At the same time, a high-precision temperature sensor is placed in the connection area to synchronously collect the local temperature rise signal. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals. Based on real-time monitoring of load change events, the analysis window is determined and synchronous data is intercepted. The synchronous data is used to construct a thermoelectric trajectory point set, and the load rise and fall period is determined to form a continuous thermoelectric dynamic trajectory; The temperature change trend is divided into heating and cooling segments. The resistance drift during the load increase in the heating segment is extracted to determine the degradation trend of the copper busbar connection. The hysteresis loop area is extracted from the complete thermal cycle trajectory to determine the status during the load change. During load changes, the connection status information generated during thermal stress and thermal cycling is obtained and analyzed, and the detection strategy is adjusted based on the connection status analysis results.

2. A copper busbar connection status detection method according to claim 1, characterized in that: During load changes, the contact resistance of the copper busbar connection is measured. At the same time, a high-precision temperature sensor is placed in the connection area to synchronously collect the local temperature rise signal. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals. The specific process is as follows: Input a constant current to the copper busbar that does not affect the main current of the copper busbar, and collect a small voltage drop at both ends of the copper busbar to determine the contact resistance of the copper busbar; Place high-precision thermocouples or temperature sensors in the copper busbar connection area to collect local temperature raw signals at the copper busbar connection. The collected local temperature raw signals are normalized to obtain the effective temperature. The contact resistance and local temperature data are merged into a unified synchronous data frame, which includes the copper busbar connection contact resistance, the copper busbar connection local temperature and a unified timestamp; Adaptive bidirectional finite difference filtering is used to filter out noise from each component in the synchronous data frame.

3. A copper busbar connection status detection method according to claim 2, characterized in that: Based on real-time monitoring of load change events, the analysis window is determined and synchronous data is intercepted. The synchronous data is used to construct a thermoelectric trajectory point set, and the load rise and fall period is determined to form a continuous thermoelectric dynamic trajectory. The specific process is as follows: Detect load change events in real time, intercept the corresponding dynamic response analysis window, and monitor the main current I main (t), detect the current change rate and calculate the first-order derivative of the current change dI main / dt, when the following conditions are met, it is determined to be the starting point of load change t s : Among them, δ I is the current change rate threshold; Set the load change analysis window length T win , intercept the data frames collected synchronously within the interval; From the analysis window [t s , t s +T win ], extract the smoothed synchronous data at each moment in, For a synchronized resistance sequence, is a synchronized temperature series; The synchronized resistance series is used as the vertical axis and the synchronized temperature series is used as the horizontal axis to construct the thermoelectric trajectory point set: C is a set of resistance and temperature trajectory points, which is used to describe the continuous thermoelectric dynamic response process; The minimum and maximum values ​​of the temperature series within the current load change window are calculated, and the minimum and maximum values ​​of the resistance series are normalized to obtain the trajectory point set of temperature and resistance.

4. A copper busbar connection status detection method according to claim 3, characterized in that: The trajectories of the heating and cooling sections are divided according to the temperature change trend. The specific steps are as follows: The trajectory point set is divided into temperature rising section and temperature falling section according to the load thermal response cycle; If the temperature difference between the current moment and the next moment is greater than zero, the temperature is increasing positively, and the time period is determined to be a heating period. If the temperature difference is less than zero, that is, the temperature is decreasing, it is determined to be a cooling period.

5. A copper busbar connection status detection method according to claim 4, characterized in that: In the temperature rise stage, the resistance drift during the load increase period is extracted to determine the degradation trend of the copper busbar connection. The hysteresis loop area is extracted from the complete thermal cycle trajectory to determine the state during the load change period. The specific process is as follows: According to the normalized temperature signal T norm (t i )Calculate the temperature change rate ΔT(t i ):ΔT(t i )=T norm (t i+1 )-T norm (t i ), where T norm (t i+1 ) represents t i+1 time; Define the segmentation rule: If ΔT(t i )>0, it is determined to be the load rising section; if ΔT(t i )<0, it is determined to be a load reduction section; Divide the trajectory point set according to the segmentation rule to obtain the load increase segment set and the load decrease segment set; The load rise and load fall trajectories will be extracted and analyzed in sections to determine the response characteristics of the copper busbar connection at different stages of thermal stress changes. In the load rising section, extract the normalized resistance signal R norm (t i ), and defines resistance drift as an integral measure of resistance change during load increase; The resistance drift is defined as: Among them, T up is the load rise time, which is obtained by the difference between the start and end time of the load rise segment; t s , t e are the starting and ending time of the load rising section respectively; The hysteresis loop contour is constructed with the load rising section and the load falling section where the trajectory points are concentrated as the boundaries, and the hysteresis area A enclosed by the hysteresis loop is calculated using the discrete curve integration method. H ; The point set of the trajectory loop arranged in ascending order of temperature is used as the hysteresis area: Where N is the total number of trajectory points.

6. A copper busbar connection status detection method according to claim 5, characterized in that: During load changes, the connection status information generated by thermal stress and thermal cycling is obtained and analyzed. The specific process is as follows: Acquiring connection status information generated during thermal stress and thermal cycling, the connection status information including resistance drift information and hysteresis response information, the resistance drift information including a thermal stress degradation dynamic index, and the hysteresis response information including a thermal cycling asymmetric stability index; The thermal stress degradation dynamic index indicates the resistance change of the copper busbar connection caused by thermal stress during load increase; The thermal cycle asymmetric stability index indicates the asymmetry and stability of the copper busbar connection after it undergoes a complete load heating and cooling cycle. The thermal stress degradation dynamic index is compared with the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is compared with the thermal cycle asymmetric stability threshold.

7. A copper busbar connection status detection method according to claim 6, characterized in that: Adjust the detection strategy based on the connection status analysis results. The specific process is as follows: The thermal stress degradation dynamic index is compared with the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is compared with the thermal cycle asymmetric stability threshold. Based on the comparison results, four situations are divided and different strategy adjustments are made; In the first scenario, if the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is also less than or equal to the thermal cycle asymmetric stability threshold, then the regular inspection cycle is maintained and monitoring is performed according to the normal inspection plan. There is no need to increase the maintenance frequency or take additional intervention measures. In the second case, if the thermal stress degradation dynamic index is greater than the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is still less than or equal to the thermal cycle asymmetric stability threshold, the subsequent detection period is shortened, drift trend tracking is increased, and local connection inspections are arranged; In the third case, if the thermal stress degradation dynamic index is less than or equal to the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is greater than the thermal cycle asymmetric stability threshold, accelerated inspection measures are taken to check the connection crimping status, bolt tightening condition, and physical condition of the contact interface; In the fourth case, if the thermal stress degradation dynamic index is greater than the thermal stress degradation dynamic threshold, and the thermal cycle asymmetric stability index is greater than the thermal cycle asymmetric stability, then the machine should be shut down for maintenance immediately, and the severely degraded connection parts should be checked and replaced, and the surrounding copper busbar connection units should be checked simultaneously.

8. A copper busbar connection status detection method system, used to implement a copper busbar connection status detection method according to any one of claims 1 to 7, characterized in that: include: The copper busbar connection data acquisition module is used to measure the contact resistance of the copper busbar connection during load changes. At the same time, high-precision temperature sensors are deployed in the connection area to synchronously collect local temperature rise signals. Finite difference filtering is used to eliminate noise and align the resistance and temperature signals. Thermoelectric trajectory determination module is used to determine the analysis window and intercept the synchronous data based on the real-time monitoring of load change events, construct the thermoelectric trajectory point set from the synchronous data, and determine the load rise and fall period to form a continuous thermoelectric dynamic trajectory; The load trend determination module is used to divide the temperature change trend into the heating and cooling segments. In the heating segment, the resistance drift during the load increase is extracted to determine the degradation trend of the copper busbar connection. In the complete thermal cycle trajectory, the hysteresis loop area is extracted to determine the status during the load change. The strategy adjustment module is used to obtain and analyze the connection status information generated during the thermal stress and thermal cycle process during the load change period, and adjust the detection strategy according to the connection status analysis results.

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