A pole-mounted circuit breaker overcurrent protection control method and system

Abstract

The present application belongs to the technical field of power electronic component manufacturing, and particularly relates to a pole-mounted circuit breaker overcurrent protection control method and system. The method comprises: collecting line current instantaneous value and constructing an analysis window; calculating waveform polarity index based on positive and negative half-wave current integration and duration difference to identify the asymmetric characteristics of magnetizing inrush current; combining current decay intensity and second-order difference value to calculate transient fluctuation reliability to distinguish cold load start-up and fault arc characteristics; using waveform polarity index and transient fluctuation reliability to construct comprehensive confidence weight, and then calculating fault degree; and only when the average value of fault degree in the analysis window exceeds the preset threshold, overcurrent protection is executed. The present application solves the problem that traditional protection cannot distinguish between non-fault transient impact and real fault, and realizes reliable locking under large current interference and precise action under real fault.

Description

Technical Field

[0001] This invention relates to the field of power electronic component manufacturing technology. More specifically, this invention relates to an overcurrent protection control method and system for pole-mounted circuit breakers. Background Technology

[0002] Pole-mounted circuit breakers are core protection devices in overhead lines of urban and rural power distribution networks. Their operating environment is complex. The ends of the lines are often connected to large-capacity transformers and motor groups. They frequently face inrush currents generated by transformers closing under no-load conditions, or cold load starting impacts caused by concentrated starting of air conditioning groups and industrial motors in summer. These non-faulty transient impact currents often reach or even exceed the set value of short-circuit fault currents in amplitude. Their electrical characteristics are easily confused with real faults, posing a severe challenge to the accurate operation of the circuit breaker.

[0003] Currently, the overcurrent protection of pole-mounted circuit breakers mainly adopts the traditional three-stage current protection logic, which mainly relies on the instantaneous amplitude of the power frequency current collected by the current transformer as the action criterion. During the detection process, once the detected current amplitude exceeds the preset setting value and reaches the set time limit, the protection device determines that there is a fault and issues a trip command.

[0004] However, in the complex actual operation scenarios of the power grid, due to the randomness of inrush current and the decay characteristics of motor starting current, traditional methods that rely solely on amplitude are difficult to effectively distinguish between non-fault transient impacts and real short-circuit faults. If the action setting is increased in order to avoid impacts, it will lead to failure to operate during small current faults such as high-resistance grounding, burning out line equipment. If the setting is reduced to ensure sensitivity, it is very easy to trip the circuit breaker falsely when closing or starting the load, causing unplanned power outages. Therefore, the need for protection and control methods that can identify transient impacts and permanent faults is a key requirement in the field of distribution automation. Summary of the Invention

[0005] To address the technical problem that traditional amplitude-based protection criteria cannot accurately distinguish between non-fault transient impacts and actual short-circuit faults when pole-mounted circuit breakers in the aforementioned distribution network face inrush currents and cold load starting impact currents, thus leading to false tripping or failure to operate, this invention provides solutions in the following aspects.

[0006] In a first aspect, the present invention provides an overcurrent protection control method for a pole-mounted circuit breaker, comprising: acquiring the instantaneous current value of the line of the pole-mounted circuit breaker and constructing an analysis window for each moment; dividing the instantaneous current value within the analysis window at any moment into several positive and negative half-waves; calculating the waveform polarity index based on the difference between the ratio of the current integral and duration of the positive and negative half-waves; calculating the attenuation intensity of the recent instantaneous current value at the stated moment; determining the transient fluctuation confidence level based on the instantaneous current value at each sampling moment within the analysis window at the stated moment, the second-order difference value of the instantaneous current value, and the attenuation intensity of the recent instantaneous current value; constructing a comprehensive confidence weight using the waveform polarity index and the transient fluctuation confidence level; calculating the fault degree based on the comprehensive confidence weight and the instantaneous current value at the stated moment; and controlling the pole-mounted circuit breaker to trip and complete the overcurrent protection when the mean of the fault degree at all sampling moments within the analysis window at the stated moment is greater than a preset action threshold.

[0007] This invention constructs a waveform polarity index and utilizes the difference in energy density between the positive and negative half-waves to accurately identify and block inrush currents with asymmetric characteristics. By calculating the reliability of transient fluctuations and combining amplitude attenuation and second-order differential characteristics, it effectively distinguishes between motor starting currents with attenuation characteristics and high-frequency fault currents accompanied by arcs. Finally, it constructs a fault severity index, realizing a soft control logic that does not necessarily trip the circuit breaker when the large current is large, but only trips when the fault characteristics are obvious, significantly improving the reliability and safety of power distribution networks.

[0008] Preferably, the current integral and duration of the positive and negative half-waves are obtained as follows: the sum of the absolute values ​​of the instantaneous current values ​​at all sampling times within each positive or negative half-wave in the analysis window is calculated and multiplied by the sampling time interval to obtain the current integral of each positive or negative half-wave; the product of the number of all sampling points within each positive or negative half-wave period and the sampling time interval is calculated to obtain the duration of each positive or negative half-wave.

[0009] This invention provides microscopic quantitative data for the waveform polarity index by calculating the integral of the absolute value of the current within a half-wave and the corresponding time span. It can capture the energy distribution differences of the current waveform on the time axis, ensuring the calculation accuracy of subsequent identification of the inrush current discontinuity angle and asymmetric features, thereby improving the accuracy of the basic data for protection logic judgment.

[0010] Preferably, the waveform polarity index satisfies the expression: In the formula, For the first Waveform polarity index at each moment; For the first The sum of the durations of all positive half-waves and the sum of the current integrals within the analysis window at each moment; For the first The sum of the durations of all negative half-waves and the sum of the current integrals of all negative half-waves within the analysis window at each time point; For the first The mean of the absolute values ​​of all instantaneous current values ​​within the analysis window at each moment; This is the adjustment coefficient; To take the absolute value; It is a natural exponential function; These are the preset hyperparameters.

[0011] This invention uses an exponential function to normalize the energy density difference, eliminating the influence of the magnitude of the current amplitude itself, ensuring the universality of the criterion, and enabling the model to sensitively respond to the asymmetry of the waveform. This provides a benchmark for the nonlinear suppression of the subsequent fault degree and effectively prevents misjudgment caused by inrush current.

[0012] Preferably, the attenuation intensity is obtained by: obtaining the maximum value of the instantaneous current within a series of consecutive adjacent analysis windows at any given time, forming a peak sequence of instantaneous current values, and the attenuation intensity of the recent instantaneous current value at any given time is equal to the ratio of the minimum to the maximum instantaneous current value in the peak sequence.

[0013] Preferably, the reliability of the transient fluctuation satisfies the expression: In the formula, For the first The reliability of transient fluctuations at any given moment; For the first The attenuation intensity of the recent instantaneous current value at a given moment; , For the first Within the analysis window at time 1, the 1st The instantaneous current value and the second-order difference of the instantaneous current value at each sampling time; To analyze the index value and total number of sampling times within the analysis window; This is the gain coefficient.

[0014] This invention introduces attenuation intensity to distinguish the attenuation characteristics of motor starting from the steady-state characteristics of faults; it introduces a gain coefficient to amplify the high-frequency second-order differential characteristics caused by fault arcs. Through gain amplification, it overcomes conventional background interference, significantly increasing stability when faults are accompanied by arcs, while maintaining a low level under smooth starting current, thus improving the sensitivity to identify high-resistance faults or weak fault characteristics.

[0015] Preferably, the comprehensive confidence weight satisfies the expression: In the formula, For the first The overall confidence weight at each moment; For the first Waveform polarity index at each moment; For the first The reliability of transient fluctuations at any given moment; To correct the strength coefficient.

[0016] This invention deeply integrates waveform symmetry and stability characteristics, generating strong suppression during inrush current to achieve reliable blocking, and generating gain during faults. This multi-dimensional feature coupling mechanism dynamically adjusts the influence weight of current amplitude, resolving the contradiction between the sensitivity and safety of the protection device.

[0017] Preferably, the calculation of the fault degree includes: calculating the ratio of the instantaneous current value at the time to a preset protection value, and using the product of the ratio and the comprehensive confidence weight as the fault degree at the time.

[0018] Preferably, the division into several positive and negative half-waves is achieved through a zero-crossing detection method.

[0019] Preferably, the method further includes: if the instantaneous current value at the time is greater than a preset protection value, and the average fault degree of all sampling times within the analysis window at the time is less than or equal to the action trigger threshold, the circuit breaker is kept in the closed state, and an inrush current alarm is reported to the main station.

[0020] Secondly, the present invention provides an overcurrent protection control system for a pole-mounted circuit breaker, comprising a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned overcurrent protection control method for a pole-mounted circuit breaker is implemented.

[0021] By adopting the above technical solution, a computer program for the above-mentioned overcurrent protection control method of pole-mounted circuit breaker is generated and stored in a memory so that it can be loaded and executed by a processor. A terminal device can then be made based on the memory and the processor for convenient use.

[0022] The beneficial effects of this invention are as follows: This invention introduces a micro-waveform feature dimension, transforming the traditional single amplitude into soft control based on multi-dimensional feature coupling. By utilizing the nonlinear suppression mechanism of waveform asymmetry, it solves the problem that high-amplitude inrush currents cannot be eliminated by traditional amplitude criteria. By utilizing the gain mechanism of fault arc roughness, it solves the problem of failure to operate due to weak current in high-resistance faults. This logic, which states that large currents do not necessarily trip and only operate when characteristics match, significantly improves the edge computing intelligence level of distribution automation terminals. Attached Figure Description

[0023] Figure 1 This is a schematic flowchart illustrating an overcurrent protection control method for a pole-mounted circuit breaker according to the present invention; Figure 2It schematically shows the waveform of the instantaneous current value; Figure 3 It is a schematic diagram illustrating the degree of failure and the resulting effect. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0025] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] This invention discloses an overcurrent protection control method for pole-mounted circuit breakers, referring to... Figure 1 This includes steps S1-S4: S1. Collect the instantaneous current value of the circuit breaker on the pole within the analysis window at each moment.

[0027] It should be noted that as a protection execution unit, the pole-mounted circuit breaker needs to sense changes in line current in real time. When a fault or operation occurs in the distribution network, the current waveform contains rich physical characteristic information. For example, short-circuit faults are usually accompanied by a sharp rise in current amplitude and the waveform maintains sinusoidal characteristics, while inrush current is characterized by spikes, discontinuous waveforms, and severe asymmetry between positive and negative half-waves. In order to capture these microsecond-level waveform details, it is necessary to collect the instantaneous current value at high frequency, rather than just collecting the calculated effective value.

[0028] Specifically, the primary current of the line is sensed by a current transformer installed at the bushing of the pole-mounted circuit breaker, and then converted from analog to digital by a signal conditioning circuit and an A / D converter. In this embodiment, the preset sampling frequency is 4kHz, and the instantaneous current value of the line where the pole-mounted circuit breaker is located is collected in real time to construct an analysis window for each moment, and the data in the analysis window at each moment is stored in a circular buffer.

[0029] The duration of the analysis window is the length of the time series segment used for waveform feature extraction and calculation. A larger analysis window duration includes more waveform periods, resulting in more stable calculation results, but it also increases the protection action delay. If the analysis window duration is too small, insufficient data will prevent the complete coverage of the positive and negative half-wave characteristics of the waveform, leading to distortion in the asymmetric exponent calculation. Therefore, the analysis window duration ranges from 30ms to 60ms, corresponding to 1.5 to 3 fundamental frequency periods. In this embodiment, the analysis window duration is 40ms, corresponding to 2 fundamental frequency periods, ensuring that both complete waveform distortion features can be captured and the timeliness requirements of distribution network instantaneous overcurrent protection are met. Implementers can adjust the duration based on the grid's rated frequency and specific indicators for protection action speed.

[0030] At this point, the instantaneous current value within the analysis window at each moment has been obtained.

[0031] S2. Divide the instantaneous current value within the analysis window at any given time into several positive and negative half-waves; calculate the waveform polarity index based on the difference in the ratio of the current integral and duration of the positive and negative half-waves.

[0032] It should be noted that when the transformer is closed under no-load conditions, the core magnetic flux saturation leads to a sharp increase in the excitation current, generating inrush current. A significant characteristic of inrush current is that its waveform is severely asymmetrical on the time axis, often exhibiting large and small half-waves, and even a clear discontinuity angle on one side. In contrast, although the current waveform of a metallic short-circuit fault has a large amplitude, it is controlled by the system impedance and usually presents a symmetrical sine wave shape with positive and negative half-waves. Therefore, we can consider using the ratio of the current integral of the half-wave to the time width it occupies to measure this polarity difference.

[0033] Specifically, for any given moment in the analysis window, the instantaneous current value is divided into several positive and negative half-waves by zero-crossing detection.

[0034] Calculate the sum of the absolute values ​​of the instantaneous current at all sampling times within each positive half-wave, and multiply it by the sampling time interval to obtain the current integral of each positive half-wave; calculate the product of the number of all sampling points and the sampling time interval within each positive half-wave period to obtain the duration of each positive half-wave; perform the same process for the negative half-wave to obtain the current integral and duration of each negative half-wave.

[0035] The waveform polarity index at any given moment is calculated based on the difference between the ratio of the current integrals and the durations of the positive and negative half-waves within the analysis window. The specific calculation formula is as follows:

[0036] In the formula, For the first Waveform polarity index at each moment; For the first The sum of the current integrals of all positive half-waves within the analysis window at each moment; For the first The sum of the durations of all positive half-waves within the analysis window at each moment; For the first The sum of the current integrals of all negative half-waves within the analysis window at each moment; For the first The sum of the durations of all negative half-waves within the analysis window at each moment; For the first The mean of the absolute values ​​of all instantaneous current values ​​within the analysis window at each moment; This is the adjustment coefficient; To take the absolute value; It is a natural exponential function; The default hyperparameter is set to 0.01 to avoid a denominator of 0.

[0037] in, Reflecting the The average energy density of the positive half-wave per unit time within the analysis window at each moment. Reflecting the The average energy density of the negative half-wave per unit time within the analysis window at each moment is such that, during a short-circuit fault, the positive and negative half-waves are symmetrical, and the waveform is full and basically consistent on both sides. Approaching 0, The amplitude approaches zero; however, during inrush current, one side exhibits a sharp waveform with a large amplitude, while the other side displays a flat waveform or has a dead zone. The larger, It approaches 1; therefore, the larger the waveform polarity exponent, the stronger the polarity of the first wave. The more uneven the energy distribution of the current waveform in terms of polarity within the analysis window at time point 1, the more... The greater the probability that a given moment is a non-fault impact such as inrush current, the more likely it is to be a fault. In the distribution network, the amplitudes of short-circuit current and inrush current differ greatly. Dividing by the mean of the instantaneous current values ​​is to eliminate the influence of the magnitude of the current amplitude itself, achieve normalization, and ensure the universality of the criterion under different fault current levels.

[0038] It should be added that the adjustment coefficient is used to control the sensitivity of the waveform polarity asymmetry exponent to the energy density difference between the positive and negative half-waves. If the adjustment coefficient is larger, the convergence speed of the exponential function will be faster, meaning that even a small density difference will cause the asymmetry exponent to approach 1, which may easily misjudge the asymmetry fault as inrush current and lead to failure to operate. If the adjustment coefficient is too small, it will reduce the ability to identify inrush current characteristics, resulting in an insufficient asymmetry exponent in the event of severe inrush current, which will not be able to effectively block the protection. Therefore, the adjustment coefficient is set to a value of 0.5 to 2, and in this embodiment, it is set to 1.2 to ensure that the discontinuity angle characteristic of the excitation inrush current can be sensitively identified, while tolerating slight transient asymmetry in the early stage of the fault. The implementer can adjust the value based on the transmission characteristics of the current transformer and the type of line load.

[0039] At this point, the waveform polarity index at each moment has been obtained.

[0040] S3. Determine the reliability of transient fluctuations based on the instantaneous current value at each sampling time within the analysis window at any given time, the second-order difference value of the instantaneous current value, and the attenuation intensity of the recent instantaneous current value at any given time.

[0041] It should be noted that, in addition to inrush current, cold load starting of the line, such as the starting of a high-power motor, will also generate overcurrent. Although the waveform of the motor starting current is relatively symmetrical, its amplitude will show obvious periodic decay as the speed increases and the waveform is relatively smooth. However, the current amplitude of a permanent short circuit fault is usually constant, and due to the instability of the arc at the fault point, the waveform is often superimposed with high-frequency noise, resulting in a less smooth waveform. Therefore, it is necessary to combine the time-varying trend of the amplitude and the microscopic smoothness of the waveform to distinguish between the starting current and the fault current, so as to ensure that the subtle distortions caused by the fault arc can be captured.

[0042] Specifically, the attenuation intensity of the recent instantaneous current value at any given moment is calculated as follows: obtain the maximum value of the instantaneous current value within a series of consecutive adjacent analysis windows at any given moment, and form a peak sequence of the instantaneous current value. The attenuation intensity of the recent instantaneous current value at any given moment is equal to the ratio of the minimum value to the maximum value of the instantaneous current value in the peak sequence.

[0043] It should be added that, in actual circuits, current will exist as long as the circuit is energized, that is, the instantaneous current value is a number greater than 0; the value of the analysis window is used to determine the time span for evaluating the attenuation trend, and the value range is 3 to 10. In this embodiment of the invention, it is set to 5 to ensure that the significant attenuation process in the early stage of motor startup can be covered; the implementer can adjust it according to the startup characteristics of the motor load in the actual circuit.

[0044] The reliability of transient fluctuations at any given time is determined based on the instantaneous current value, the second-order difference of the instantaneous current value, and the attenuation intensity of the recent instantaneous current value at each sampling time within the analysis window at any given time; the reliability of transient fluctuations satisfies the expression:

[0045] In the formula, For the first The reliability of transient fluctuations at any given moment; For the first The attenuation intensity of the recent instantaneous current value at a given moment; , For the first Within the analysis window at time 1, the 1st The instantaneous current value and the second-order difference of the instantaneous current value at each sampling time; To analyze the index value and total number of sampling times within the analysis window; This is the gain coefficient.

[0046] in, Reflecting the The stability of the current amplitude at a recent moment. The larger the value, the more it indicates that the current amplitude has remained constant over a period of time without a significant decay trend. This means that the current overcurrent is more consistent with the steady-state characteristics of a permanent short-circuit fault than the decay characteristics of motor starting. Reflecting the The degree of high-frequency abrupt changes in the current waveform within the analysis window at time t is considered; the larger this value, the stronger the abrupt change. The higher the proportion of second-order differential energy in the current waveform within the analysis window at each moment, that is, the more high-frequency noise abrupt changes in the waveform caused by unstable arcing at the fault point, the greater the likelihood that the current overcurrent exhibits fault arc characteristics; using As a positive gain factor, when a permanent short-circuit fault occurs, the current amplitude is stable and accompanied by arc noise, the positive gain factor will be significantly greater than 1, making... A significant increase in current amplitude accelerates fault diagnosis; conversely, when the motor starts, the current amplitude decreases and the waveform becomes smoother, with the positive gain factor approaching 1, making... Maintaining it at a low level effectively prevents misjudgment.

[0047] It should be added that, in actual calculations, the proportion of the second-order differential energy of the current waveform relative to the fundamental amplitude energy is usually small, often on the order of 0.001 to 0.05. The value will always be close to 1, causing the waveform roughness characteristics to be submerged, and the final calculation results will not reflect the significant difference between fault arc and normal start-up. By introducing a gain coefficient, it is ensured that while ignoring conventional background noise, the roughness characteristics caused by the fault arc can be amplified to a degree sufficient to affect the judgment result. If the gain coefficient is too large, it will over-amplify the influence of high-frequency noise, resulting in an excessively low stability coefficient and failure to start in the case of faults containing harmonics. If the gain coefficient is too small, it will not be able to effectively use the waveform smoothness characteristics to eliminate noise interference. Therefore, the value of the gain coefficient is in the range of 5 to 15. In this embodiment of the invention, it is set to 10, so that the gain factor during faults reaches 1.2 to 1.5 times, thereby significantly distinguishing between fault and non-fault states. The implementer can adjust it according to the power quality background noise level of the actual power grid.

[0048] At this point, the reliability of transient fluctuations at each moment is obtained.

[0049] S4. Calculate the fault degree based on the instantaneous current value, waveform polarity index, and transient fluctuation reliability at any given moment; when the average fault degree of all sampling moments within the analysis window at any given moment is greater than the preset action threshold, the control column circuit breaker trips to complete overcurrent protection.

[0050] It should be noted that traditional overcurrent protection only considers whether the current exceeds the preset value. However, in complex distribution networks, the current exceeding the set value does not necessarily mean that the circuit breaker must trip. Therefore, by constructing a fault severity index, if the waveform shows extreme asymmetry, that is, strong inrush current characteristics, the score should be significantly reduced; if the waveform shows high stability and symmetry, that is, strong short circuit characteristics, the score should be maintained or increased, thereby achieving efficient protection.

[0051] Specifically, a comprehensive confidence weight is constructed using the waveform polarity index and transient fluctuation confidence at any given time. This comprehensive confidence weight satisfies the following expression:

[0052] In the formula, For the first The overall confidence weight at each moment; For the first Waveform polarity index at each moment; For the first The reliability of transient fluctuations at any given moment; To correct the strength coefficient.

[0053] in, Reflecting the The confidence level of the symmetry of the current waveform at each moment, when inrush current occurs, the waveform polarity index approaches 1, making Approaching 0, thus affecting the degree of failure. It produces a strong suppression effect, preventing misjudgment due to large inrush current amplitude; when a short-circuit fault occurs, the waveform is symmetrical. Approaching 0, making Approaching 1, the influence weight of the original current amplitude is preserved; Reflecting the The comprehensive confidence weight for fault determination at time step i, which couples the waveform symmetry and transient fluctuation confidence, indicates that the higher the confidence weight is at time step i. The current waveform at the nth moment exhibits both high symmetry and stable amplitude, along with characteristics of arc roughness, meaning that the nth moment... The probability that the overcurrent at that moment was caused by a real, permanent fault is extremely high.

[0054] It should be added that the correction strength coefficient is used to adjust the nonlinear correction strength of the waveform feature confidence level to the fault degree. If the correction strength coefficient is larger, the requirement for feature confidence level will be more stringent. That is, a high score will only be obtained when the waveform feature extremely matches the fault model, which improves safety but may sacrifice sensitivity. If the correction strength coefficient is too small, it will weaken the suppression effect of waveform features, making it easy to be dominated by current amplitude and malfunction when the feature is ambiguous. Therefore, the value range of the correction strength coefficient is 1.5 to 2.5. In this embodiment, it is 2 to ensure that the fault criterion achieves the best balance between amplitude exceeding the limit and waveform features, and realizes accurate protection against interference. Implementers can adjust it according to the distribution network's emphasis on power supply reliability and safety.

[0055] The ratio of the instantaneous current value at any given moment to a preset protection value is calculated, and the product of this ratio and the comprehensive confidence weight is taken as the fault severity at that moment. The preset protection value is determined based on the current circuit requirements, and the ratio reflects the baseline overcurrent multiple at that moment. By correcting the basic overcurrent factor, soft control was achieved, which ensures that the circuit breaker does not necessarily trip when the current is high, but only trips when the fault characteristics are obvious.

[0056] At this point, the degree of failure at each moment is obtained.

[0057] Furthermore, an action trigger threshold is set. At any given moment: if the average fault severity of all sampled moments within the analysis window at that moment is greater than the action trigger threshold, then a permanent short-circuit fault is determined to have occurred on the line, and the controller immediately sends a trip command to the pole-mounted circuit breaker to cut off the fault current; conversely, if the instantaneous current value at that moment is greater than the preset protection value, and the average fault severity of all sampled moments within the analysis window at that moment is less than or equal to the action trigger threshold, it indicates that although the current exceeds the limit, the waveform characteristics conform to inrush current or motor starting characteristics. The controller executes the blocking logic, keeps the circuit breaker in the closed state, and reports an inrush current alarm to the main station, thereby avoiding unnecessary power outages.

[0058] The action trigger threshold is the critical criterion for determining whether the line should perform a tripping operation. During a metallic short circuit, the current waveform is symmetrical and smooth, and the overall confidence weight approaches 1. At this time, the fault severity degenerates into a simple overcurrent multiple. Setting the action trigger threshold to 1 means that the protection will activate as long as the current exceeds the preset protection value, which is completely consistent with the logic of traditional overcurrent protection. During non-fault impacts, the overall confidence weight is much less than 1. Even if the current multiple is large, the calculation result is still pulled down below the threshold, achieving reliable blocking. However, during high-resistance faults accompanied by arcing, the waveform roughness generates gain, making the overall confidence weight greater than 1. Even if the current is slightly lower than the preset protection value, it can still break the threshold, achieving high-sensitivity disconnection. Therefore, in this embodiment of the invention, the action trigger threshold is set to 1, which can be adjusted by the implementer according to specific requirements for protection sensitivity.

[0059] For example, Figure 2 The waveform of the instantaneous current is shown, where the horizontal axis represents the sampling time and the vertical axis represents the current value in units of pu (pu), i.e., the per-unit value of the instantaneous current. The period from 0s to 0.2s represents the normal load condition, with the current amplitude below the protection value and the waveform generally smooth. The period from 0.2s to 0.4s represents the inrush current interference stage, where the current amplitude instantly increases to 4pu, far exceeding the protection value, exhibiting a significant spiked waveform, severe asymmetry between the positive and negative half-waves, and discontinuity angle characteristics. The period from 0.4s to 0.6s represents the short-circuit fault stage, where the current amplitude stabilizes at 2.5pu. Due to the unstable arc burning at the fault point, although the waveform is symmetrical, it is superimposed with obvious high-frequency noise.

[0060] Figure 3 The graph shows the effect of fault severity assessment, where the horizontal axis represents sampling time and the vertical axis represents the fault severity value. During normal load conditions, due to the small current, the fault severity value fluctuates only in the low range, indicating that the system is in a safe state under real-time monitoring. During inrush current interference, although the input current amplitude is large, the waveform polarity index rapidly responds to the waveform asymmetry and approaches 0, exerting a strong nonlinear suppression effect on the fault severity, keeping it suppressed in the low range and always below the action trigger threshold. This achieves reliable blocking of the protection device under strong interference, avoiding false tripping. During short-circuit fault conditions, as the waveform returns to symmetry and the reliability of transient fluctuations is excited by the high-frequency characteristics of the electric arc, the fault severity value rapidly increases and exceeds the action threshold, with an amplitude reaching 3-4, achieving high-sensitivity identification of real faults and accelerated tripping.

[0061] This invention also discloses an overcurrent protection control system for a pole-mounted circuit breaker, including a processor and a memory. The memory stores computer program instructions, which, when executed by the processor, implement an overcurrent protection control method for a pole-mounted circuit breaker according to the present invention.

[0062] The system also includes other components well known to those skilled in the art, such as communication buses and communication interfaces, the settings and functions of which are known in the art and will not be described in detail here.

Claims

1. A method for overcurrent protection control of a pole-mounted circuit breaker, characterized in that, include: Obtain the instantaneous current value of the line of the pole-mounted circuit breaker and construct the analysis window for each moment; Divide the instantaneous current value within the analysis window at any given time into several positive and negative half-waves; calculate the waveform polarity index based on the difference between the ratio of the current integral and the duration of the positive and negative half-waves. Calculate the attenuation intensity of the recent instantaneous current value at the given time; determine the reliability of transient fluctuations based on the instantaneous current value at each sampling time within the analysis window at the given time, the second-order difference of the instantaneous current value, and the attenuation intensity of the recent instantaneous current value. A comprehensive confidence weight is constructed using the waveform polarity index and transient fluctuation confidence. The degree of fault is calculated based on the comprehensive confidence weight and the instantaneous current value at the specified time. When the average fault severity at all sampling times within the analysis window at the specified time exceeds a preset action threshold, the control column circuit breaker trips to complete overcurrent protection.

2. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The current integrals and durations of the positive and negative half-waves are obtained as follows: Calculate the sum of the absolute values ​​of the instantaneous current at all sampling times within each positive or negative half-wave in the analysis window, and multiply it by the sampling time interval to obtain the current integral of each positive or negative half-wave; calculate the product of the number of all sampling points within each positive or negative half-wave period and the sampling time interval to obtain the duration of each positive or negative half-wave.

3. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 2, characterized in that, The waveform polarity index satisfies the expression: ； In the formula, For the first Waveform polarity index at each moment; For the first The sum of the durations of all positive half-waves and the sum of the current integrals within the analysis window at each moment; For the first The sum of the durations of all negative half-waves and the sum of the current integrals of all negative half-waves within the analysis window at each time point; For the first The mean of the absolute values ​​of all instantaneous current values ​​within the analysis window at each moment; This is the adjustment coefficient; To take the absolute value; It is a natural exponential function; These are the preset hyperparameters.

4. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The attenuation intensity is obtained as follows: The maximum value of the instantaneous current within a series of consecutive adjacent analysis windows at any given time is obtained to form a peak sequence of the instantaneous current values. The attenuation intensity of the recent instantaneous current value at any given time is equal to the ratio of the minimum to the maximum instantaneous current value in the peak sequence.

5. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The reliability of the transient fluctuation satisfies the expression: ； In the formula, For the first The reliability of transient fluctuations at any given moment; For the first The attenuation intensity of the recent instantaneous current value at a given moment; , For the first Within the analysis window at time 1, the 1st The instantaneous current value and the second-order difference of the instantaneous current value at each sampling time; To analyze the index value and total number of sampling times within the analysis window; This is the gain coefficient.

6. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The overall confidence weights satisfy the expression: ； In the formula, For the first The overall confidence weight at each moment; For the first Waveform polarity index at each moment; For the first The reliability of transient fluctuations at any given moment; To correct the strength coefficient.

7. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The calculation of the fault degree includes: Calculate the ratio of the instantaneous current value at the specified moment to the preset protection value, and multiply the ratio by the comprehensive confidence weight as the fault degree at the specified moment.

8. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The segmentation into several positive and negative half-waves is achieved through a zero-crossing detection method.

9. The overcurrent protection control method for a pole-mounted circuit breaker according to claim 1, characterized in that, The method further includes: if the instantaneous current value at the specified moment is greater than the preset protection value, and the average fault degree of all sampling moments within the analysis window at the specified moment is less than or equal to the action trigger threshold, the circuit breaker is kept in the closed state, and an inrush current alarm is reported to the main station.

10. A pole-mounted circuit breaker overcurrent protection control system, characterized in that, include: A processor and a memory, the memory storing computer program instructions that, when executed by the processor, implement an overcurrent protection control method for a pole-mounted circuit breaker according to any one of claims 1-9.

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