Circuit breaker terminal block temperature imbalance alarm self-checking method and system and circuit breaker

Abstract

This invention relates to the field of intelligent control technology for power systems, specifically to a self-testing method, system, and circuit breaker for alarming temperature imbalance at circuit breaker terminal blocks. The invention identifies load current step events from the real-time three-phase current using a preset current step criterion while the intelligent circuit breaker is in energized operation. Current characteristic parameters within a preset time window before and after the event are input into the terminal block thermal response model to obtain the expected response trend of each phase terminal block temperature during the evaluation period. Based on a self-testing reference alarm criterion, the expected alarm state that the temperature imbalance alarm module should exhibit during the evaluation period is determined. This state is then compared with the actual output state of the temperature imbalance alarm module during the evaluation period to obtain the self-testing result of the step event. This achieves online closed-loop self-testing without requiring power outage tests or additional testing equipment, solving the problem of difficulty in verifying the long-term reliability of the alarm function.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology for power systems, specifically to a self-testing method, system, and circuit breaker for alarming temperature imbalance at circuit breaker terminal blocks. Background Technology

[0002] With the continuous improvement of power distribution network load levels and automation, intelligent circuit breakers are gradually replacing traditional mechanical circuit breakers, undertaking multiple functions such as line connection and disconnection, protection tripping, and remote monitoring. As a crucial connection point in the primary circuit, the contact resistance, conductive cross-section, and fastening condition of the circuit breaker's incoming and outgoing terminal blocks directly affect the heat generation level during operation. Poor contact, insufficient fastening force, or severe oxidation of the conductor surface can all lead to abnormal local temperature rise, potentially causing serious accidents such as insulation aging, terminal erosion, or even equipment fire. Therefore, installing terminal block temperature sensors and setting up temperature imbalance alarm functions in intelligent circuit breakers has become a common measure to improve the operational safety of power distribution equipment.

[0003] In existing technologies, terminal block temperature imbalance alarm functions typically involve placing temperature detection units near each phase terminal block to collect the temperature of each phase terminal block in real time, and triggering an alarm or alarm record based on whether the inter-phase temperature difference exceeds a preset threshold. This type of solution is relatively mature in engineering applications, but it generally suffers from two shortcomings: First, the alarm function itself lacks online self-testing capabilities. Temperature sensors may experience zero-point drift, decreased sensitivity, or installation position deviations during long-term operation. The sampling and processing link may also introduce additional errors due to factors such as component aging and loose connectors. These changes directly affect the reliability of the alarm action, but are often difficult to detect in a timely manner. Second, on-site verification of the terminal block temperature imbalance alarm function usually relies on manual testing during power outage maintenance or temporary heating / loading devices. This operation is complex, has a significant impact on power supply, and makes it difficult to maintain a high frequency of functional verification throughout the equipment's entire lifespan.

[0004] Meanwhile, the role of smart circuit breakers in distribution network automation and condition-based maintenance is constantly increasing. Maintenance departments are increasingly relying on temperature imbalance alarm information reported by the devices to identify potential contact overheating hazards and schedule maintenance. If the health status of the terminal block temperature imbalance alarm function itself is lacking for a long period, on the one hand, there is a risk of missed alarms where there is serious imbalance overheating in the terminal block but the alarm function has "malfunctioned" without anyone knowing; on the other hand, improper alarm threshold settings or abnormal measurement links may lead to frequent false alarms, interfering with operational decisions and reducing the trust of maintenance personnel in alarm information. How to provide a self-checking method for the terminal block temperature imbalance alarm function that can be performed during operation without affecting the normal protection and control functions of the circuit breaker, and with minimal additional hardware and power outage operations, and to assess its long-term health status accordingly, remains a problem that needs further resolution in the current technology. Summary of the Invention

[0005] (I) The technical problem to be solved by the present invention is that although existing intelligent circuit breakers are equipped with terminal block temperature detection units and temperature imbalance alarm functions, they lack a method to verify and quantify the correctness of the alarm function from load current and terminal block temperature response to alarm output under the condition of long-term energized operation of the circuit breaker. It is difficult to detect the performance degradation of the temperature measurement link or alarm criteria in a timely manner and the resulting false alarms and missed alarms.

[0006] (II) Technical Solution To address the aforementioned technical problems, this invention provides a self-test method for alarming temperature imbalance at circuit breaker terminal blocks, applicable to intelligent circuit breakers equipped with a terminal block temperature detection unit, a three-phase current detection unit, and a temperature imbalance alarm module. The method includes the following steps: S1: When the intelligent circuit breaker is in a energized operating state, monitor the three-phase current data in real time and identify load current step events based on a preset current step criterion. S2: In response to the identification of the load current step event, obtain the current characteristic parameters within a preset time window before and after the event, and input the current characteristic parameters into a preset terminal block thermal response model to obtain the expected response trend of the terminal block temperature of each phase during the evaluation period after the load current step event. S3: Based on the expected response trend, the expected alarm state that the temperature imbalance alarm module should present during the evaluation period is determined using the preset self-test reference alarm criteria; S4: Obtain the actual output status of the temperature imbalance alarm module during the evaluation period, and generate a single self-test result for the load current step event based on the consistency between the actual output status and the expected alarm status.

[0007] Further, in step S1, the identification of load current step events based on a preset current step criterion includes: The continuously sampled three-phase current data is processed by a sliding time window, and the second effective value of each phase current in the current time window and the first effective value of each phase current in the immediately preceding time window are calculated respectively. When the absolute value of the difference between the second effective value and the corresponding first effective value of any phase current exceeds a preset step threshold, and the duration of the second effective value is not less than a preset stabilization time, it is determined that the load current step event has been detected. By using the difference between the first and second effective values ​​within the preceding and following time windows, and superimposing the constraints of "amplitude exceeding the limit + duration not shorter than the preset stable duration", short-term fluctuations caused by sampling noise and instantaneous disturbances can be effectively filtered out. This ensures that a load current step event is identified only when the load current undergoes a significant and relatively stable change in amplitude over a period of time, thereby guaranteeing that the self-test excitation condition has a clear physical meaning and good repeatability.

[0008] Calculate the change in three-phase current during the load current step event, where the change in each phase current is the difference between the corresponding second effective value and the first effective value. When the absolute value of the difference between any two of the changes in the three-phase current does not exceed the preset balance deviation threshold, the load current step event is marked as a three-phase balanced step event; otherwise, the load current step event is marked as an unbalanced load event.

[0009] After detecting a step event, the event is automatically marked as a three-phase balanced step event or an unbalanced off-center load event based on the relative deviation of the three-phase current changes. This allows for a differentiated approach when making judgments based on the expected temperature response and self-test reference alarm criteria. Balanced events are used to identify false alarm tendencies, while unbalanced events are used to identify missed alarms or insufficient sensitivity. This provides physically directional event labels for the self-test results from the source, improving the accuracy and interpretability of the online self-test of the terminal block temperature imbalance alarm function.

[0010] Further, in step S3, determining the expected alarm state based on the expected response trend using a preset self-test reference alarm criterion includes: When the load current step event is marked as a three-phase balance step event, it is determined that the expected temperature difference between the terminal blocks of each phase is always lower than the alarm action threshold in the self-test reference alarm criterion during the evaluation period, and the expected alarm state is determined to be a no-alarm state. When the load current step event is marked as an unbalanced off-center load event, it is determined whether the maximum value of the expected temperature difference obtained based on the expected response trend during the evaluation period exceeds the alarm action threshold: if it exceeds, the expected alarm state is determined as an alarm triggered state; if it does not exceed, the expected alarm state is determined as a non-alarm state.

[0011] Through the above processing, the determination of the expected alarm state is directly based on the classification of current step types and the evolution of the expected temperature difference of the terminal block. The criteria for "should not alarm" and "should alarm" are quantified and distinguished using a unified alarm action threshold, so that the expected behavior no longer relies on experience judgment. In this way, on the one hand, a clear reference scenario of "temperature imbalance alarm should not be triggered" is formed under three-phase balanced step events; on the other hand, under unbalanced load events, the standard for whether or not an alarm should be triggered is given by judging whether the limit is exceeded. This provides a clear and implementable physical basis for subsequent consistency comparison between the expected alarm state and the actual output state, which is conducive to distinguishing between false alarm tendency and false alarm tendency in self-test results.

[0012] Further, in step S4, generating a single self-test result based on the consistency between the actual output state and the expected alarm state includes: When the expected alarm state is a no-alarm state, but the actual output state is an alarm signal output, a self-check result for false alarm tendency is generated. When the expected alarm state is the alarm triggered state, and the actual output state does not output an alarm signal within the allowable delay range, a self-test result of missed alarm tendency is generated. When the actual output state matches the expected alarm state, and the alarm action time falls within the preset allowable error range, a self-test result indicating normal function is generated.

[0013] Through the above consistency comparison, the actual behavior of the temperature imbalance alarm module under each load current step event is clearly categorized into three types: false alarm tendency, false alarm tendency, or normal function. This ensures that the self-test results are no longer limited to a coarse-grained judgment of "whether an alarm has occurred," but rather use the expected alarm state as a benchmark to refine the sensitivity and reliability of the alarm logic. Based on the cumulative statistics of these single self-test results, the false alarm and false alarm risks of the terminal block temperature imbalance alarm function in long-term operation can be quantified, and objective evidence can be provided for subsequent operation and maintenance decisions, threshold setting verification, and functional degradation or repair recommendations.

[0014] Furthermore, the intelligent circuit breaker is configured with an operating criterion set and a self-test criterion set when executing the self-test method; The temperature imbalance alarm module monitors the real-time collected terminal block temperature data based on the operating criterion set in order to control the alarm or tripping of the circuit breaker. The self-test reference alarm criterion used in step S3 belongs to the self-test criterion set; The temperature difference threshold and / or action delay parameter in the self-test criterion set are configured to be different from the corresponding parameters in the running criterion set, so as to form a more sensitive or more conservative evaluation boundary relative to the running criterion set during the self-test process.

[0015] By simultaneously configuring both the operational criterion set and the self-test criterion set within the intelligent circuit breaker, and by consistently binding the field alarm / trip control of the temperature imbalance alarm module to the operational criterion set, the self-test process utilizes only reference alarm criteria from the self-test criterion set for the derivation and consistency comparison of the expected alarm state. This decouples the self-test evaluation logic from the actual protection action logic at the criterion level, preventing interference with field alarm and trip behavior during the self-test process. Furthermore, by setting the temperature difference threshold and / or action delay parameters in the self-test criterion set to configurations distinct from those in the operational criterion set, the self-test evaluation can employ more sensitive or conservative evaluation boundaries while maintaining the original protection sensitivity and reliability. This allows for a more rigorous internal assessment of the terminal block temperature imbalance alarm function's operational margin, false alarm risk, and missed alarm risk, thereby improving the accuracy of the self-test conclusions in determining the functional health status.

[0016] Furthermore, the circuit breaker terminal block temperature imbalance alarm self-test method also includes: When the load current step event is identified, the current environmental parameters and circuit breaker operating parameters are obtained; If the current ambient temperature fluctuation rate exceeds the environmental threshold, or the load current after the event change is lower than the minimum assessed current, then steps S2 to S4 are prohibited from being executed, or the single self-test result corresponding to this load current step event is marked as invalid.

[0017] By introducing the acquisition of environmental and operational parameters after identifying a load current step event, and by actively prohibiting the execution of steps S2 to S4 or marking the self-test result of this event as invalid when the current ambient temperature fluctuation rate exceeds the environmental threshold or the load current after the step is lower than the minimum evaluation current, this invention can remove unrepresentative operating conditions such as severe environmental disturbances and extremely low loads from the self-test sample. This avoids incorrect evaluation of the temperature imbalance alarm function under conditions where the temperature difference response itself is not typical or the signal-to-noise ratio is poor. Therefore, on the one hand, it prevents abnormal environmental fluctuations and light load conditions from misjudging alarm functions as "false alarms" or "missed alarms." On the other hand, the self-test event set used for statistical health level assessment is more concentrated on load step processes that are representative of engineering, thereby improving the stability and reliability of long-term functional health assessment results and reducing the risk of maintenance decisions being interfered with by occasional operating conditions.

[0018] Furthermore, the circuit breaker terminal block temperature imbalance alarm self-test method also includes: S5: Within a preset statistical period, accumulate the single self-test results corresponding to multiple load current step events; S6: Statistically analyze the frequency or percentage of normal function, false alarm tendency, and false alarm tendency in the single self-test results; S7: Determine the health level of the temperature imbalance alarm function based on the statistical results. When the proportion of false alarm tendency or missed alarm tendency exceeds the preset warning threshold, the health level is determined as a warning level or a fault level.

[0019] By accumulating the single self-test results of multiple load current step events within a preset statistical period, and separately statistically analyzing the frequency or proportion of normal function, false alarm tendency, and missed alarm tendency, and then combining this with a preset warning threshold to classify the health level, this invention elevates the consistency comparison results based on a single event to a long-term statistical evaluation of the terminal block temperature imbalance alarm function. This transforms the status of the alarm function from "whether it operates correctly in a single instance" to "whether its overall performance is reliable over a period of time." By setting a warning threshold for the proportion of false alarms / missed alarms and providing a warning level or fault level accordingly, on the one hand, it avoids the excessive influence of individual sporadic anomalies on the functional evaluation results, making the health determination smoother and more robust. On the other hand, it provides a quantitative basis for maintenance personnel to decide whether to adjust the alarm criteria, repair sensors, or disable related functions, thereby facilitating continuous monitoring and management of the operational reliability of the circuit breaker terminal block temperature imbalance alarm function without power interruption.

[0020] Furthermore, the terminal block thermal response model is a first-order thermal resistance and thermal capacity network model. The parameters of the first-order thermal resistance and thermal capacity network model are adaptively identified and updated based on the phase current data and phase terminal block temperature data collected during the historical steady-state operation of the circuit breaker.

[0021] By limiting the terminal block thermal response model to a simple first-order thermal resistance-capacitance network model, and adaptively updating the model parameters based on phase current data and phase terminal block temperature data during the circuit breaker's historical steady-state operation, the model can dynamically converge to a state matching the actual operating conditions of the equipment, taking into account the actual thermal inertia and heat dissipation conditions. Therefore, the expected response trend of each phase terminal block temperature obtained based on this model in step S2 can more closely approximate the actual temperature rise process, reducing the influence of fixed empirical parameters or factory calibration errors on the expected temperature difference calculation, improving the reliability of the expected alarm state judgment, and making it suitable for long-term online self-testing applications of different circuit breaker models and different installation environments.

[0022] This invention also provides a self-testing system for alarm function of circuit breaker terminal block temperature imbalance, integrated into the control unit of a smart circuit breaker, comprising: The event detection module is configured to monitor three-phase current data and identify load current step events based on a preset current step criterion. The expected prediction module is configured to respond to the identification of the load current step event by using a preset terminal block thermal response model combined with the current characteristic parameters within a preset time window before and after the occurrence of the load current step event to calculate the expected response trend of the terminal block temperature of each phase during the evaluation period, and to use a preset self-test reference alarm criterion to determine the expected alarm state that the temperature imbalance alarm module should present. The verification module is configured to acquire the actual output state of the temperature imbalance alarm module during the evaluation period, and output a single self-test result based on its consistency with the expected alarm state.

[0023] By implementing the detection of load current step events, the deduction of terminal block temperature expected response, and the alarm output consistency verification as an event detection module, an expected deduction module, and a verification module, respectively, and establishing a clear signal transmission and calling relationship within the intelligent circuit breaker control unit, the processing steps in the self-testing method of this invention can be completed sequentially as program modules on a unified hardware platform. This system structure facilitates the integration of the self-testing function of this invention into existing intelligent circuit breaker platforms through software or firmware upgrades. Furthermore, by configuring step criteria, thermal response model parameters, and self-test reference alarm criteria, it can adapt to circuit breakers of different models, voltage levels, and operating scenarios, thereby providing a clear device implementation carrier for the implementation of the method of this invention and ensuring the feasibility of the overall technical solution.

[0024] The present invention also provides an intelligent circuit breaker, comprising: The circuit breaker body includes contacts and terminal blocks connected in series in the main circuit; Terminal block temperature detection unit is used to collect the temperature of each phase terminal block; A current detection unit is used to acquire the main circuit current; and The intelligent control unit is signal-connected to the terminal block temperature detection unit and the current detection unit; The intelligent control unit is configured to run the above-mentioned circuit breaker terminal block temperature imbalance alarm self-test system, and / or execute a computer program stored in its memory to implement the circuit breaker terminal block temperature imbalance alarm self-test method described above.

[0025] Through the above structural configuration, the current acquisition, terminal block temperature acquisition, expected temperature response deduction, and alarm output consistency verification required for self-testing are all completed in a closed loop within the circuit breaker body. This eliminates the need for an external host computer or additional testing devices, enabling online self-testing and health assessment of the terminal block temperature imbalance alarm function under actual operating conditions. The intelligent control unit, based on the existing protection and control hardware platform, can expand the functionality of existing intelligent circuit breakers by integrating a self-testing system or loading corresponding computer programs. This facilitates the deployment of the present invention on existing equipment via software or firmware upgrades, and provides newly manufactured equipment with integrated alarm self-testing capabilities that combine protection and measurement functions.

[0026] (III) Beneficial Effects of the Invention: This invention identifies load current step events from real-time three-phase current using a preset current step criterion while the intelligent circuit breaker is in energized operation. Current characteristic parameters within a preset time window before and after the event are input into the terminal block thermal response model to obtain the expected response trend of each phase terminal block temperature during the evaluation period. Based on a self-test reference alarm criterion, the expected alarm state that the temperature imbalance alarm module should exhibit during the evaluation period is determined. This is then compared with the actual output state of the temperature imbalance alarm module during the evaluation period to obtain the self-test result for a single step event. Therefore, without requiring power outage tests or additional testing equipment, online closed-loop self-testing of the terminal block temperature imbalance alarm function under real operating conditions is achieved. This allows for a quantitative assessment of whether the function operates as expected and whether there are risks of false alarms or missed alarms, thus solving the problem of difficulty in verifying the long-term operational reliability of the alarm function in the prior art. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the structure of an intelligent circuit breaker and a circuit breaker terminal block temperature imbalance alarm self-test system provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating a self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to an embodiment of the present invention. Detailed Implementation

[0029] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation

[0030] The intelligent circuit breaker in this embodiment is installed in the poles, ring main units, or switching stations of the distribution network feeder. It is used to electrically connect the upstream power supply side with the downstream distribution lines and their load sides. During normal operation, it performs line switching and power transmission functions. In the event of overload, short circuit, grounding, or other faults, it cooperates with protection logic to perform tripping and reclosing control. Figure 1 As shown, the intelligent circuit breaker includes a circuit breaker body connected in series with the main circuit of the power system. The circuit breaker body is equipped with a vacuum interrupter, moving and stationary contact assemblies, and incoming and outgoing terminal blocks that are connected to external conductors. Each phase incoming and outgoing terminal block is the object of terminal block temperature detection.

[0031] Terminal block temperature detection units, such as resistance temperature sensors, thermocouples, or semiconductor temperature sensors, are arranged near each phase terminal block. These units are connected to the analog sampling channel of the intelligent control unit via wires or flexible circuit boards to collect the temperature signals of each phase terminal block in real time and convert them into corresponding digital data. Current detection units may include current transformers or Hall effect current sensors installed in series with the conductors of each phase main circuit. Their secondary side or output is connected to the current sampling interface of the intelligent control unit via analog front-end circuitry to obtain continuous sampling data of the three-phase current in the main circuit, providing electrical input for load current step event identification and terminal block thermal response simulation.

[0032] The intelligent control unit is located in the secondary control compartment of the circuit breaker body, and integrates hardware resources such as a microprocessor or digital signal processor, memory, power supply module, analog sampling and A / D conversion circuit, digital input / output interface, and communication interface. The temperature imbalance alarm module runs in the form of software logic in the intelligent control unit. Based on the temperature data of each phase terminal block collected by the terminal block temperature detection unit and the preset temperature difference threshold and action delay parameters, it monitors the temperature imbalance state of the terminal block in real time and issues alarm or trip control signals. Based on this, the intelligent control unit also operates a self-testing system for the circuit breaker terminal block temperature imbalance alarm function. This self-testing system is divided into an event detection module, a predictive deduction module, and a verification module at the software level: the event detection module extracts load current step events from the three-phase current data provided by the current detection unit; the predictive deduction module calls a preset terminal block thermal response model and combines it with current characteristic parameters within a preset time window before and after the step event to calculate the expected response trend of each phase terminal block temperature during the evaluation period, and generates the corresponding expected alarm state based on the self-test reference alarm criteria stored in memory; the verification module reads the actual output state of the temperature imbalance alarm module during the self-test evaluation period and compares it with the expected alarm state, outputting a data marker representing the self-test result of the alarm function under this load current step event. These modules interact through the data bus within the intelligent control unit. Combined with the configuration of the circuit breaker body, terminal block temperature detection unit, and current detection unit, online self-testing and health status assessment of the terminal block temperature imbalance alarm function can be achieved on the existing intelligent circuit breaker hardware platform.

[0033] Based on the hardware architecture of the aforementioned intelligent circuit breaker, the circuit breaker terminal block temperature imbalance alarm self-test method provided in this embodiment is automatically executed by the intelligent control unit during long-term energized operation of the device. The intelligent control unit pre-stores an operating criterion set and a self-test criterion set, and maintains data such as terminal block thermal response model parameters, environmental and operating parameters, and historical self-test results in its memory.

[0034] like Figure 2 As shown, the method generally uses a load current step event as the self-test excitation condition, and completes event identification, environmental screening, temperature expected response deduction, expected alarm status determination, actual alarm output comparison, and health status statistical evaluation in sequence according to steps S1 to S7, as follows: First, step S1 is executed to sample the three-phase current in real time and identify load current step events. The intelligent control unit acquires the digital quantities of the three-phase current from the current detection unit at a fixed sampling period, such as several sampling points at 10ms or one power frequency cycle, forming a continuous three-phase current sequence. To identify step changes in current over a certain time scale, the control unit uses a sliding time window to segment the three-phase current data. The current time window can be set to several to dozens of sampling cycles, such as 0.2 to 1s. The effective value of each phase current within each time window is calculated as the second effective value; the effective value of each phase current in the immediately preceding time window on the time axis is also calculated as the first effective value. For each phase current, the control unit calculates the absolute value of the difference between the second effective value and the corresponding first effective value. If the difference exceeds a preset step threshold, and the second effective value continues to meet the change level for at least a preset stable duration in the subsequent several time windows, then it is determined that a load current step event has occurred near the current time position. The step threshold can be set according to a certain proportion of the rated current of the circuit breaker, for example, 10% to 30% of the rated current. The stabilization time can be set to 3 to 10 current time windows to ensure that only load changes with significant and continuous amplitude changes are marked, and to avoid instantaneous spikes or sampling noise being misidentified as step events.

[0035] Upon detecting a load current step event, the intelligent control unit further calculates the change in current for each phase during the event, specifically by determining the difference between the second and first effective values ​​for each phase current. Subsequently, the control unit compares the changes in the three-phase current pairwise, calculating the absolute value of the difference between each pair and comparing it to a preset balance deviation threshold. If the absolute value of the difference between any pairwise changes in the three-phase current does not exceed the balance deviation threshold, the load current step event is marked as a three-phase balance step event; otherwise, if at least one phase current change significantly deviates from the other phases, the event is marked as an unbalanced load event. The balance deviation threshold can be set as a certain percentage of the average change in each phase or according to the expected allowable unbalance, for example, it can be set as a percentage of the average change. Through the above processing, the intelligent control unit can not only automatically capture significant step changes in load current during normal operation of the circuit breaker, but also assign a balanced / unbalanced type label to each step event, so that subsequent expected temperature response deduction and alarm behavior judgment can be evaluated separately for two types of operating conditions: "multi-phase near-equilibrium heating" and "single-phase or a few-phase off-center heating", making the self-test results more physically oriented.

[0036] After identifying a load current step event, this embodiment preferably performs environmental and operating condition judgments to filter out events suitable as self-test samples. Specifically, near the time of the step event, the intelligent control unit reads current environmental parameters, such as the ambient temperature obtained by environmental temperature sensors placed inside the switchgear or around the circuit breaker, or the environmental status inside the switchgear obtained by the monitoring system, and calculates the rate of change of ambient temperature over a period of time, for example, the temperature difference within a several-minute time window divided by the length of the time window, as the ambient temperature fluctuation rate; at the same time, the control unit obtains the circuit breaker operating parameters corresponding to the event, such as the effective value of the load current of each phase before and after the step, the load rate, or the power factor. If the current ambient temperature fluctuation rate exceeds a preset environmental threshold, such as a drastic change in ambient temperature in a short period of time, or the load current after the event change is lower than the minimum evaluation current, such as being lower than a certain percentage of the rated current, then the terminal block temperature response of this step event is considered unrepresentative or has a low signal-to-noise ratio. In this case, the control unit prohibits the execution of the subsequent S2 to S4 self-test process for this event, or marks the single self-test result corresponding to the event as invalid and not included in the subsequent health statistics. By screening the above environmental and operating conditions, atypical temperature changes under severe environmental disturbances or light load conditions can be eliminated, so that the events participating in the self-inspection statistics are concentrated in the operating range with moderate load levels and relatively stable environment.

[0037] For load current step events that are selected as suitable self-test samples based on environmental and operating conditions, the control unit executes step S2 to acquire the current characteristic parameters before and after the event, and deduce the expected response trend of each phase terminal block temperature based on the terminal block thermal response model. Specifically, the control unit extracts the effective value and related statistics of each phase current within a preset time window before and after the step event, and uses the steady-state effective value of the current before the event, the new steady-state effective value of the current after the event, and the moment of the step event as input features. The terminal block thermal response model preferably adopts a first-order thermal resistance-capacity network model, based on the response of the terminal block temperature rise to the square of the current, which can be expressed as: the temperature difference between the terminal block temperature and the ambient temperature changes with time according to a first-order inertial process. In discrete-time implementation, a recursive form can be used. For example, for the i-th phase terminal block, the expected temperature difference ΔT_i(k) at discrete time k can be calculated according to the following relationship: ΔT_i(k+1)=ΔT_i(k)+[−(ΔT_i(k) / τ_i)+k_i·I_i²(k)]·Δt, Where Δt is the discrete time step, τ_i is the equivalent thermal time constant of the phase terminal block, k_i is the proportionality coefficient of the temperature rise caused by the current, and I_i(k) is the effective value of the current at that moment.

[0038] In practical implementation, the above heat dissipation model can be reorganized into a linear regression form Y=X·θ, where the regression vector X is composed of the temperature difference at the previous moment and the square of the current at the current moment, and the parameter vector θ is composed of coefficients related to τ_i ​​and k_i. Using current and terminal block temperature samples collected during historical steady-state operation, the optimal value of θ is estimated using a least squares or recursive least squares algorithm, thus obtaining the parameters of a first-order thermal resistance-capacity network model that matches the field operating conditions. Based on the above thermal response model, the intelligent control unit progresses from the moment the step event occurs until the end of the preset evaluation period, calculating the expected change curve of the terminal block temperature for each phase at each discrete time step, and thereby obtaining the expected temperature difference between the three-phase terminal blocks at any moment within the evaluation period. In other embodiments, for devices with more complex thermal inertia changes, a second-order or higher-order thermal network model can also be used to describe the terminal block temperature response under the same modeling approach. The modeling and self-testing process is similar to the first-order model, and it can also realize the deduction of the expected temperature response based on the current step event.

[0039] For example, in a certain unbalanced load step event, assuming the current in phase A jumps from 200A to 400A, while the currents in phases B and C remain approximately 200A, the control unit marks this event as an unbalanced load event. Based on the aforementioned thermal response model and the identified τ_A and k_A parameters, it can be estimated that the expected temperature difference between the phase A terminal block and phases B and C should reach approximately 45K 10 minutes after the step event. The evaluation period can be set to 15 minutes after the step event. In this scenario, the temperature difference threshold in the self-test reference alarm criterion can be set to 40K, and the expected alarm state is that a temperature imbalance alarm should be triggered at a certain point within the evaluation period. Subsequent self-test processes use this expected temperature difference and expected alarm state as a reference to perform a consistency comparison of the actual alarm behavior.

[0040] After obtaining the expected response trend of the terminal block temperature for each phase, the control unit executes step S3, using a preset self-test reference alarm criterion to determine the expected alarm state corresponding to the step event. To this end, the intelligent control unit internally maintains both a running criterion set and a self-test criterion set. The temperature difference threshold and action delay parameters in the running criterion set are used to control the alarm or tripping of the temperature imbalance alarm module during actual operation, while the self-test reference alarm criterion in the self-test criterion set is specifically used for determining the expected alarm state in this embodiment. For cases marked as three-phase balance step events, the control unit calculates the expected temperature response based on the thermal response model, iterates through the three-phase temperature differences at each discrete moment within the evaluation period, and determines whether the expected temperature difference remains below the alarm action threshold in the self-test reference alarm criterion throughout the entire evaluation period. If the expected temperature difference does not exceed the limit during the evaluation period, the expected alarm state of the terminal block temperature imbalance alarm function under this event is determined to be a non-alarm state. For cases marked as unbalanced load events, the control unit calculates the maximum expected temperature difference within the evaluation period based on the expected temperature response curve and compares this maximum expected temperature difference with the alarm action threshold in the self-test reference alarm criterion: if the maximum expected temperature difference exceeds the alarm action threshold and the duration meets the self-test evaluation requirements, the expected alarm state is determined to be an alarm triggered state; if it does not exceed the threshold or the exceedance time is insufficient to meet the delay requirements in the self-test criterion, the expected alarm state is determined to be a non-alarm state. The temperature difference threshold and action delay parameters in the self-test reference alarm criterion can be appropriately adjusted according to the corresponding parameters in the operating criterion set. For example, the temperature difference threshold in the operating criterion can be 30K and the action delay can be 5s, while the temperature difference threshold in the self-test criterion can be 28K and the action delay can be 3s. This makes the self-test evaluation more sensitive to alarm action margin and response speed without changing the on-site alarm and tripping strategies.

[0041] To facilitate timeline management, the intelligent control unit can record the time point at which the load current step event is detected as t0, and define the evaluation period after the step event for extrapolating the expected temperature response and observing alarm behavior as [t0, t0+T_eval], where T_eval is a pre-set evaluation duration. In the case of unbalanced load events, one or more expected alarm trigger time points can be determined within the evaluation period, and the actual alarm action time can be compared in subsequent steps.

[0042] Subsequently, step S4 is executed. The control unit acquires the actual output status of the temperature imbalance alarm module during the evaluation period and compares the actual output status with the expected alarm status to generate a single self-test result for the load current step event. Specifically, during normal operation, the temperature imbalance alarm module monitors the real-time terminal block temperature data according to the operating criterion set. When the phase-to-phase temperature difference exceeds the operating threshold and persists for a certain period of time, it outputs a temperature imbalance alarm signal and may trigger a trip if necessary. The intelligent control unit records the timestamp and duration of each alarm trigger in its memory. When executing the self-test method, it searches for an alarm signal issued by the temperature imbalance alarm module during the evaluation period and obtains the actual alarm status and its action time. Based on the combination of expected and actual alarm states, the control unit generates a single self-test result according to preset rules: when the expected alarm state is no alarm, but the actual output state during the evaluation period is an alarm signal, the self-test result is marked as prone to false alarms, indicating a risk that the temperature imbalance alarm function is overly sensitive or has overly strict criteria; when the expected alarm state is an alarm triggered state, but no actual alarm output is detected within the allowable delay range, the self-test result is marked as prone to missed alarms, indicating a risk that the alarm function is not sensitive enough or that the measurement link is abnormal; when the actual output state is consistent with the expected alarm state, and for the case where the expected alarm state is an alarm triggered state, the alarm action time falls within the preset allowable error range, the self-test result is marked as functionally normal. The allowable delay range and allowable error range can be adjusted according to the sampling period, processing delay, and engineering-acceptable time deviation of the circuit breaker control unit, for example, allowing the alarm trigger time to fluctuate within several sampling periods or several seconds relative to the expected time. Each step event corresponds to a single self-test result, along with the event time, event type (balanced / unbalanced), environmental and operating parameters, which are then stored in the memory as an event entry to provide a data basis for subsequent statistical evaluation.

[0043] To avoid distorted evaluations of the temperature imbalance alarm function under unrepresentative operating conditions, the environmental and operating condition screening in this embodiment serves as the entry condition for steps S2 to S4 throughout the entire self-test process. After each identified load current step event, the intelligent control unit prioritizes checking the ambient temperature fluctuation rate and the magnitude of the load current following the step. If the ambient temperature changes significantly within a short period, possibly due to changes in the ventilation status of the switchgear, air conditioning startup / shutdown, or sudden changes in external weather, or if the load current following the step is significantly lower than normal and the terminal block's own heating level is insufficient to reflect the change in contact state, this embodiment does not perform temperature prediction and alarm consistency comparison for this event. Instead, it marks the event as an invalid self-test event or skips the self-test process altogether. This ensures that the events included in the self-test statistics are mainly concentrated in the operating range with moderate load levels and relatively stable environments, allowing the self-test results to more accurately reflect the performance of the terminal block temperature imbalance alarm function under typical operating conditions.

[0044] Based on the results of a single self-test, this embodiment further performs a statistical evaluation of the long-term health status of the temperature imbalance alarm function through steps S5 to S7. Specifically, in step S5, the intelligent control unit sets a preset statistical period, which can be set according to the time dimension as the most recent several days or weeks, or according to the event quantity dimension as the most recent N valid step events. Within this statistical period, the control unit reads the single self-test results corresponding to all the load current step events marked as valid from the memory, forming a self-test result sequence. In step S6, the control unit counts the occurrence frequency of the three types of results in the sequence: normal function, false alarm tendency, and missed alarm tendency, and calculates the occurrence ratio of each type of result based on the total number of valid events within the statistical period, such as the percentage of normal function, the percentage of false alarm tendency, and the percentage of missed alarm tendency. In step S7, the control unit compares the statistically obtained percentages of false alarm tendency and missed alarm tendency with a preset warning threshold. When the percentage of false alarm tendency or missed alarm tendency exceeds the corresponding warning threshold, the health level of the temperature imbalance alarm function is adjusted from the normal level to the warning level or the fault level. The warning threshold can be adjusted based on maintenance requirements and equipment importance. For example, a warning can be issued when the percentage of false alarms or missed alarms exceeds a certain percentage, and a fault can be identified when the percentage rises further to an even higher percentage. Health levels can be displayed as status variables on the local HMI or transmitted to the upper-level monitoring system via a communication interface, reminding maintenance personnel to pay attention to the calibration status of the alarm function or to schedule maintenance. Through the aforementioned long-term statistical evaluation, the operating status of the terminal block temperature imbalance alarm function no longer depends solely on the correctness or incorrectness of a single action, but is quantitatively described by the comprehensive performance of multiple self-test results within a certain time window. This facilitates the identification of functional degradation trends and the implementation of targeted maintenance measures.

[0045] To support the aforementioned temperature-based expected response derivation process, this embodiment employs a first-order thermal resistance-capacitance network model for the terminal block thermal response. Its parameters are adaptively identified and updated based on the phase current data and terminal block temperature data collected during the circuit breaker's historical steady-state operation. During the steady-state period of long-term closed operation of the circuit breaker and relatively slow load changes, the intelligent control unit periodically selects several time periods. The three-phase current and terminal block temperature data within these time periods are used as samples. The proportionality coefficient k_i is determined by fitting the relationship between the temperature difference and the square of the current, and the thermal time constant τ_i is determined by fitting the rate of change of the temperature difference. For example, the least squares method can be used to treat the terminal block temperature difference as the response of a first-order inertial system to the square of the current excitation, obtaining the optimal parameter combination; alternatively, online identification algorithms such as recursive least squares can be used to gradually update the model parameters as new data arrives. Through this adaptive parameter update mechanism, the terminal block thermal response model can automatically adapt to different circuit breaker models, different installation environments, and changes in terminal contact conditions over time. Thus, when assessing the expected temperature response after a load current step event, it always maintains an accuracy that matches the actual equipment's thermal inertia and heat dissipation capacity, providing a physically reasonable basis for the reliable determination of expected alarm states.

[0046] The above are preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A self-test method for alarming temperature imbalance at circuit breaker terminal blocks, applied to an intelligent circuit breaker equipped with a terminal block temperature detection unit, a three-phase current detection unit, and a temperature imbalance alarm module, characterized in that, The method includes the following steps: S1: When the intelligent circuit breaker is in a energized operating state, monitor the three-phase current data in real time and identify load current step events based on a preset current step criterion. S2: In response to the identification of the load current step event, obtain the current characteristic parameters within a preset time window before and after the event, and input the current characteristic parameters into a preset terminal block thermal response model to obtain the expected response trend of the terminal block temperature of each phase during the evaluation period after the load current step event. S3: Based on the expected response trend, the expected alarm state that the temperature imbalance alarm module should present during the evaluation period is determined using the preset self-test reference alarm criteria; S4: Obtain the actual output status of the temperature imbalance alarm module during the evaluation period, and generate a single self-test result for the load current step event based on the consistency between the actual output status and the expected alarm status.

2. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, In step S1, the identification of load current step events based on a preset current step criterion includes: The continuously sampled three-phase current data is processed by a sliding time window, and the second effective value of each phase current in the current time window and the first effective value of each phase current in the immediately preceding time window are calculated respectively. When the absolute value of the difference between the second effective value and the corresponding first effective value of any phase current exceeds a preset step threshold, and the duration of the second effective value is not less than a preset stabilization time, it is determined that the load current step event has been detected. Calculate the change in three-phase current during the load current step event, where the change in each phase current is the difference between the corresponding second effective value and the first effective value. When the absolute value of the difference between any two of the changes in the three-phase current does not exceed the preset balance deviation threshold, the load current step event is marked as a three-phase balanced step event; otherwise, the load current step event is marked as an unbalanced load event.

3. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 2, characterized in that, In step S3, determining the expected alarm state based on the expected response trend using a preset self-test reference alarm criterion includes: When the load current step event is marked as a three-phase balance step event, it is determined that the expected temperature difference between the terminal blocks of each phase is always lower than the alarm action threshold in the self-test reference alarm criterion during the evaluation period, and the expected alarm state is determined to be a no-alarm state. When the load current step event is marked as an unbalanced off-center load event, it is determined whether the maximum value of the expected temperature difference obtained based on the expected response trend during the evaluation period exceeds the alarm action threshold: if it exceeds, the expected alarm state is determined as an alarm triggered state; if it does not exceed, the expected alarm state is determined as a non-alarm state.

4. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, In step S4, generating a single self-test result based on the consistency between the actual output state and the expected alarm state includes: When the expected alarm state is a no-alarm state, but the actual output state is an alarm signal output, a self-check result for false alarm tendency is generated. When the expected alarm state is the alarm triggered state, and the actual output state does not output an alarm signal within the allowable delay range, a self-test result of missed alarm tendency is generated. When the actual output state matches the expected alarm state, and the alarm action time falls within the preset allowable error range, a self-test result indicating normal function is generated.

5. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, The intelligent circuit breaker is configured with an operating criterion set and a self-test criterion set when executing the self-test method; The temperature imbalance alarm module monitors the real-time collected terminal block temperature data based on the operating criterion set in order to control the alarm or tripping of the circuit breaker. The self-test reference alarm criterion used in step S3 belongs to the self-test criterion set; The temperature difference threshold and / or action delay parameter in the self-test criterion set are configured to be different from the corresponding parameters in the running criterion set, so as to form a more sensitive or more conservative evaluation boundary relative to the running criterion set during the self-test process.

6. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, The method further includes: When the load current step event is identified, the current environmental parameters and circuit breaker operating parameters are obtained; If the current ambient temperature fluctuation rate exceeds the environmental threshold, or the load current after the event change is lower than the minimum assessed current, then steps S2 to S4 are prohibited from being executed, or the single self-test result corresponding to this load current step event is marked as invalid.

7. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, The method further includes: S5: Within a preset statistical period, accumulate the single self-test results corresponding to multiple load current step events; S6: Statistically analyze the frequency or percentage of normal function, false alarm tendency, and false alarm tendency in the single self-test results; S7: Determine the health level of the temperature imbalance alarm function based on the statistical results. When the proportion of false alarm tendency or missed alarm tendency exceeds the preset warning threshold, the health level is determined as a warning level or a fault level.

8. The self-test method for alarming temperature imbalance of circuit breaker terminal blocks according to claim 1, characterized in that, The terminal block thermal response model is a first-order thermal resistance and thermal capacity network model. The parameters of the first-order thermal resistance and thermal capacity network model are adaptively identified and updated based on the phase current data and phase terminal block temperature data collected during the historical steady-state operation of the circuit breaker.

9. A self-testing system for alarm function of circuit breaker terminal block temperature imbalance, integrated into the control unit of a smart circuit breaker, characterized in that, include: The event detection module is configured to monitor three-phase current data and identify load current step events based on a preset current step criterion. The expected prediction module is configured to respond to the identification of the load current step event by using a preset terminal block thermal response model combined with the current characteristic parameters within a preset time window before and after the occurrence of the load current step event to calculate the expected response trend of the terminal block temperature of each phase during the evaluation period, and to use a preset self-test reference alarm criterion to determine the expected alarm state that the temperature imbalance alarm module should present. The verification module is configured to acquire the actual output state of the temperature imbalance alarm module during the evaluation period, and output a single self-test result based on its consistency with the expected alarm state.

10. An intelligent circuit breaker, characterized in that, include: The circuit breaker body includes contacts and terminal blocks connected in series in the main circuit; Terminal block temperature detection unit is used to collect the temperature of each phase terminal block; Current detection unit, used to collect the main circuit current; as well as The intelligent control unit is signal-connected to the terminal block temperature detection unit and the current detection unit; The intelligent control unit is configured to run the self-testing system as described in claim 9, and / or execute a computer program stored in its memory to implement the self-testing method as described in any one of claims 1 to 8.

Images