One and two times fusion column circuit breaker with electronic pt self-power supply

Abstract

This invention relates to the field of power system protection technology, and particularly to a primary and secondary integrated pole-mounted circuit breaker that enables autonomous power supply from electronic PTs. The circuit breaker includes a processor for: acquiring the original discrete sampling sequence of the three-phase current during circuit breaker closing operations; preprocessing this sequence to obtain the instantaneous DC current sampling sequence, fundamental current amplitude, and second harmonic current amplitude for each phase; extracting the maximum peak current, maximum instantaneous current rise rate, and second harmonic content ratio; calculating the inrush current confidence index using a nonlinear mapping function; calculating a delay adjustment coefficient based on the nominal rated operating current; correcting the basic inrush current delay with the maximum allowable inrush current delay as the upper limit; obtaining the preliminary inrush current delay; and outputting a zero-delay triggered instantaneous tripping circuit breaker if the short-circuit judgment condition is met; otherwise, obtaining the final actual inrush current delay through smoothing verification and shielding overcurrent protection actions during this period. This invention improves the reliability of power supply in distribution networks and the operational safety of circuit breakers.

Description

Technical Field

[0001] This invention relates to the field of power system protection technology, and in particular to a primary and secondary integrated pole-mounted circuit breaker that enables electronic PTs to autonomously draw power for supply. Background Technology

[0002] Against the backdrop of the large-scale application of primary and secondary integrated pole-mounted circuit breakers in distribution network construction, electronic PTs, or electronic voltage transformers, have gradually replaced traditional electromagnetic PTs and become the core component for panoramic acquisition of line voltage and fault detection. Electronic PTs require a continuous and stable power supply to the measurement circuit for normal operation. In engineering projects, autonomous power supply schemes based on line current transformer induction or high-voltage bus voltage division are commonly adopted.

[0003] To avoid the inrush current generated by the unloaded transformer at the moment of closing, traditional pole-mounted circuit breakers typically employ a control method that sets a fixed inrush current delay in the controller. When the circuit breaker closes, the timing begins, and the overcurrent protection action is shielded within the set delay period. After the fixed delay ends, the standard three-stage overcurrent protection is restored.

[0004] In actual electronic PT autonomous power supply process, due to the high electrical coupling between the autonomous power supply circuit and the measurement circuit, high-frequency oscillations and overvoltages during the closing transient process are easily conducted to the measurement circuit along the power supply link, causing voltage waveform distortion and being misjudged as fault characteristic quantities. At the same time, the fixed delay mechanism cannot adaptively distinguish between inrush current and short-circuit current. When the setting time is too short, the inrush current transient distortion can easily lead to false tripping of the protection. When there is a metallic short-circuit fault in the line at the moment of closing, the fixed delay will delay the fault clearing time, causing the power supply module to be damaged due to the impact of the large short-circuit current for a long time, and even causing circuit breaker equipment failure. Summary of the Invention

[0005] To address the technical problems of existing electronic PT autonomous power supply circuits being susceptible to waveform distortion and misjudgment due to transient inrush current interference during closing, and the inability of fixed delays to simultaneously accommodate inrush current avoidance and rapid short-circuit clearing, this invention provides a primary and secondary integrated pole-mounted circuit breaker for autonomous power supply of electronic PTs. This circuit breaker includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it performs the following steps: acquiring the original discrete sampling sequence of the three-phase current for each circuit breaker closing operation; preprocessing to obtain the DC-DC instantaneous current sampling sequence, fundamental current amplitude, and second harmonic current amplitude for each phase; extracting the maximum peak current based on the DC-DC instantaneous current sampling sequence of each phase; and extracting the maximum peak current based on the maximum ratio of the current difference between two adjacent discrete sampling points in the original discrete sampling sequence of each phase to the sampling interval. The system calculates the maximum instantaneous current rise rate; obtains the second harmonic content ratio based on the ratio of the second harmonic current amplitude to the fundamental current amplitude; calculates the inrush current confidence index using a nonlinear mapping function based on the maximum instantaneous current rise rate, the second harmonic content ratio, and the maximum peak current; calculates the delay adjustment coefficient based on the ratio of the maximum peak current to the nominal rated operating current and the inrush current confidence index; corrects the inherent basic inrush current delay of the circuit breaker operating mechanism based on the delay adjustment coefficient, and obtains the preliminary inrush current delay with the maximum allowable inrush current delay as the upper limit; determines whether the maximum instantaneous current rise rate and the second harmonic content ratio meet the preset short-circuit judgment conditions. If they do, it outputs zero-delay triggered instantaneous tripping; if not, it performs smoothing verification on the preliminary inrush current delay to obtain the final actual inrush current delay, and shields the overcurrent protection action during the final actual inrush current delay.

[0006] Preferably, the step of extracting the maximum peak current based on the DC instantaneous current sampling sequence of each phase includes: extracting the maximum value in the DC instantaneous current sampling sequence of each phase as the peak current of each phase, and obtaining the maximum value among the peak currents of the three phases as the maximum peak current.

[0007] Preferably, the step of extracting the maximum instantaneous current rise rate includes: obtaining the maximum value of the current change rate between two adjacent discrete sampling points in the original discrete sampling sequence of each phase current, as the maximum value of each phase; and extracting the maximum value among the three phase values ​​as the maximum instantaneous current rise rate.

[0008] Preferably, the surge confidence index satisfies the expression: In the formula, Indicates the first Inrush current confidence index corresponding to the secondary circuit breaker closing operation; , , They represent the first The maximum instantaneous current rise rate, maximum peak current, and second harmonic content ratio of the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; , , , respectively, represent the nonlinear mapping sensitivity coefficients corresponding to each item; 0.3, 0.4, and 0.3 represent the decision weights corresponding to each item; This represents the hyperbolic tangent function.

[0009] Preferably, the delay adjustment coefficient satisfies the expression: In the formula, , , They represent the first The delay adjustment coefficient, inrush current confidence index and maximum peak current corresponding to the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; This indicates the preset first multiplier coefficient; This indicates the preset first growth rate coefficient; This indicates the preset second multiplier coefficient; This indicates a preset second growth rate coefficient; Represents the natural constant.

[0010] Preferably, obtaining the preliminary inrush current delay includes: multiplying the inherent basic inrush current delay of the circuit breaker operating mechanism by the delay adjustment coefficient to obtain the theoretical blocking time; and taking the minimum value between the theoretical blocking time and the maximum allowable inrush current delay of the circuit breaker as the preliminary inrush current delay.

[0011] Preferably, the step of determining whether the maximum instantaneous current rise rate and the second harmonic content ratio meet the preset short-circuit determination conditions includes: if the ratio of the maximum instantaneous current rise rate to the nominal rated operating current of the circuit breaker is greater than a preset short-circuit fault rise rate threshold, and the second harmonic content ratio is less than a preset upper limit of the second harmonic content in a short-circuit fault, then the preset short-circuit determination conditions are met; otherwise, the preset short-circuit determination conditions are not met.

[0012] Preferably, the step of smoothing and verifying the preliminary inrush current delay to obtain the final actual inrush current delay includes: extracting two consecutive preliminary inrush current delays calculated within the same circuit breaker closing event, determining the smaller of the two, and calculating the absolute value of the difference between the two; when the absolute value of the difference is greater than 30% of the smaller value, selecting the larger of the two as the final actual inrush current delay; when the absolute value of the difference is less than or equal to 30% of the smaller value, selecting the arithmetic mean of the two as the final actual inrush current delay.

[0013] Preferably, the preprocessing to obtain the instantaneous DC de-current sampling sequence, fundamental current amplitude, and second harmonic current amplitude for each phase includes: using a least squares attenuation DC fitting algorithm to calculate the discrete sequence of the non-periodic attenuated DC component contained in the original discrete sampling sequence of the three-phase current; performing point-by-point subtraction between the original discrete sampling sequence of the three-phase current and the discrete sequence of the non-periodic attenuated DC component to obtain the instantaneous DC de-current sampling sequence for each phase; applying a second-order digital low-pass filter to the instantaneous DC de-current sampling sequence for each phase to obtain the filtered sequence, and multiplying the filtered sequence by a Hanning window function to obtain a smoothed windowed sequence; performing a fast Fourier transform on the smoothed windowed sequence to generate a discrete spectrum sequence, reading the magnitude of the fundamental component in the discrete spectrum sequence as the fundamental current amplitude, and reading the magnitude of the second harmonic component as the second harmonic current amplitude.

[0014] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows: This invention relates to inrush current delay based on adaptive calculation of multidimensional electrical characteristics of the closing transient. When the closing waveform is determined to be a transformer excitation inrush current, the system adaptively extends or retracts the overcurrent blocking time, avoiding false tripping of protection caused by waveform distortion due to transient overvoltage and high-frequency oscillations propagating along the power supply link to the measurement circuit. When a metallic short-circuit fault exists in the line at the moment of closing, the system forcibly clears the delay to zero and bypasses the shielding counter through the short-circuit rapid bypass branch, directly driving the instantaneous trip to achieve rapid fault clearing. This control method solves the technical problems in the prior art where the electronic PT autonomous power supply circuit is easily affected by transient inrush current interference, leading to waveform distortion and misjudgment, and the fixed delay cannot simultaneously take into account inrush current avoidance and rapid short-circuit clearing. Under the premise of ensuring timely protection tripping, it improves the reliability of power supply in the distribution network and the operational safety of circuit breaker switching equipment. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating the working steps of a pole-mounted circuit breaker that integrates primary and secondary power supply for autonomous power generation by electronic PT.

[0017] Figure 2 This is a schematic diagram of the computational link from electrical characteristics to adaptive inrush delay.

[0018] Figure 3 This is a schematic diagram of the circuit breaker closing operation judgment process. Detailed Implementation

[0019] Embodiments of this disclosure are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting it.

[0020] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0021] This invention provides a primary and secondary integrated pole-mounted circuit breaker for autonomous power supply of electronic PTs. The circuit breaker includes a processor and a memory. The memory stores a computer program, and the processor executes the computer program to implement steps, such as... Figure 1 As shown, it specifically includes: Step S101: Sample three-phase current data and perform frequency domain preprocessing.

[0022] It should be noted that in standard power system operation specifications, the nominal fundamental frequency of the power supply network is constant at 50Hz, and the alternating period of a complete power frequency sine wave is constant at 20ms. According to the classical transformer electromagnetic induction and core magnetization theory, when an unloaded transformer is closed and the core enters a state of magnetic saturation, the generated inrush current naturally contains a very high second harmonic component, whose physical frequency is strictly equal to twice 50Hz, i.e., 100Hz. However, during the transient process of circuit breaker closing and energizing, the current measured on the line is an asymmetrical waveform composed of a standard 50Hz sinusoidal AC component, a non-periodic decaying DC component, and high-frequency oscillations caused by the charging and discharging of the energy storage capacitor in the electronic PT power extraction circuit. If a Fast Fourier Transform (FFT) is directly applied to the extracted 20ms raw waveform, the discontinuous steps of the non-periodic decaying DC component at the beginning and end of the 20ms time window will violate the mathematical premise of the FFT regarding the infinite periodic repetition of the signal in the time domain. This will cause severe spectral leakage in the frequency domain, resulting in the DC energy dissipating into higher frequency bands and directly raising the calculation baseline at 100Hz, thus distorting the extracted second harmonic amplitude. Therefore, before frequency domain calculation, attenuated DC stripping, high-frequency hardware ripple filtering, and time-domain windowing smoothing need to be performed sequentially in the underlying link.

[0023] Specifically, after the circuit breaker is installed, commissioned, and put into normal operation, the three-phase current is sampled at a high-speed synchronous frequency using a built-in current transformer. When the underlying layer captures the pulse trigger moment of the circuit breaker closing command, it continuously records the original discrete sampling sequence of the three-phase current within the power frequency cycle starting from the closing moment. In the formula, the phase sequence index include Mutually, Harmony Phase, discrete sampling point number The range is to The power frequency period refers to the alternation period of a complete power frequency sine wave, which is 20ms.

[0024] It should be added that the preset sampling frequency is used to limit the time-domain density when discretizing the continuous current analog signal. In this embodiment, 10kHz is used, which ensures that exactly 200 consecutive instantaneous current discrete sampling points are extracted within each 20ms power frequency cycle, that is, the total number of sampling point sequences at this time. It is always equal to 200; this sampling density is higher than the lower limit of the Nyquist sampling theorem for the restoration of power frequency and low harmonics, and avoids the overflow of computing power of the underlying microprocessor due to excessive expansion of data volume, so as to ensure the accurate capture of the steep rising edge of the closing transient waveform.

[0025] After obtaining the original discrete sampling sequence, the preprocessing is performed in the following three steps in sequence: The first step is to independently isolate the aperiodic DC component phase by phase: Because the three-phase AC currents differ by 120 electrical degrees in space, the initial flux angles corresponding to the closing moments of the three-phase contacts of the circuit breaker are completely different, resulting in the initial amplitudes of the attenuated DC components in the three-phase currents being independent of each other. Therefore, the calculation is carried out independently phase by phase, using a single phase as the basic unit, according to the phase sequence. The process involves iteratively processing the original discrete sampling sequence of any phase. A well-known least-squares attenuation DC fitting algorithm is applied to calculate the discrete sequence of the non-periodic attenuation DC component contained in the waveform. Subsequently, the original discrete sampling sequence of any phase is subtracted point-by-point from the fitted discrete sequence of the DC component to obtain the instantaneous DC current sampling sequence of any phase. After this subtraction, the data baseline is restored to the AC sequence with 0A as the axis of symmetry.

[0026] The second step is digital low-pass filtering and windowing smoothing: the DC-to-DC instantaneous current sampling sequence... A second-order digital low-pass filter with a cutoff frequency of 2kHz is applied to obtain the filtered sequence. The filtered sequence is then multiplied point by point by a well-known Hanning window function. Utilizing the mathematical convergence property that the weights at the beginning and end of the Hanning window function approach zero, the sampled values ​​of the waveform at the beginning and end of the 20ms time window are smoothly attenuated to zero, resulting in a smoothed windowed sequence that reduces truncation jump errors. The reason for setting the cutoff frequency to 2kHz is that the micropower switching power supply module inside the electronic PT's autonomous power supply circuit will backfeed high-frequency switching ripple, typically above several kilohertz, into the measurement circuit during charging and discharging. 2kHz can intercept the hardware ripple conducted through the power supply link while fully preserving the core power frequency and low-order harmonic groups of 50Hz to 500Hz required for waveform recognition.

[0027] The third step is frequency domain feature spectral line calculation: A Fast Fourier Transform (FFT) is performed on the smoothed windowed sequence to generate a discrete spectrum sequence. According to the known formula for calculating the frequency resolution of the Discrete Fourier Transform, the frequency interval between two adjacent spectral lines in the discrete spectrum sequence is equal to the ratio of the preset sampling frequency to the total number of sampling points in the sequence. Therefore, directly from the generated spectral sequence data, the magnitude of the first frequency spectral line, i.e., the 50Hz fundamental component, is read and recorded as the fundamental current amplitude; the magnitude of the second frequency spectral line, i.e., the 100Hz second harmonic component, is read and recorded as the second harmonic current amplitude.

[0028] Thus, the sampling sequence of DC instantaneous current, fundamental current amplitude, and second harmonic current amplitude of any phase are obtained for each circuit breaker closing operation.

[0029] Step S102: Extract the multi-dimensional electrical characteristics of the circuit breaker closing operation.

[0030] It should be noted that, in the amplitude domain, the peak current provides an analytical benchmark for the energy base of transient events. A higher peak current indicates a slower demagnetization of the iron core, and the required overcurrent blocking window should be extended accordingly. In the time domain, the maximum rate of rise is the most direct morphological criterion for distinguishing between inrush current and short circuit. A metallic short circuit is an instantaneous breakdown of the insulating medium, and the driving current rises sharply with a near-vertical slope within hundreds of microseconds. In contrast, the excitation inrush current is constrained by the gradual saturation process of the iron core's magnetic domains, and its waveform exhibits a smooth, slowly rising leading edge characteristic, with a significantly lower instantaneous derivative. In the frequency domain, the second harmonic content is a unique frequency domain indicator of iron core saturation. Inrush current accumulates a large amount of second harmonic current amplitude energy, while the harmonic content of short-circuit current is extremely low. In the field of electrical evaluation, the above three characteristics are mutually redundant and supportive. Therefore, this step provides data for subsequent decision-making by solving the above characteristics.

[0031] Specifically, obtain the DC instantaneous current sampling sequence of any phase during any circuit breaker closing operation, extract the maximum value of the DC instantaneous current sampling sequence of each phase during any circuit breaker closing operation as the peak current of each phase, and obtain the maximum value of the three-phase peak current as the maximum peak current of any circuit breaker closing operation.

[0032] Obtain the original discrete sampling sequence of the current in each phase during any circuit breaker closing operation, and calculate the maximum instantaneous current rise rate during any circuit breaker closing operation based on the current difference between two adjacent discrete sampling points and the sampling interval; the specific calculation formula is as follows:

[0033] In the formula, Indicates the first Maximum instantaneous current rise rate during the secondary circuit breaker closing operation; Indicates the first Secondary circuit breaker closing operation The maximum rate of change of current between adjacent sampling points in the original discrete sampling sequence of phase current; Indicates the first Secondary circuit breaker closing operation The maximum rate of change of current between adjacent sampling points in the original discrete sampling sequence of phase current; Indicates the first Secondary circuit breaker closing operation The maximum rate of change of current between adjacent sampling points in the original discrete sampling sequence of phase current; This indicates taking the maximum value.

[0034] in, Reflects the first The transient burst force at the steepest moment of the upward climb of the waveform in the original discrete sampling sequence of the three-phase current during the second circuit breaker closing operation is used to pinpoint the current derivative of the phase that first experiences arc breakdown or magnetic circuit excitation within the 20ms closing oscillation of the three-phase contacts at the steepest instant; the larger this value, the stronger the current derivative of the first phase. A significant change in current during the closing operation of the second circuit breaker indicates a possible metallic short circuit; conversely, a smaller value suggests a more significant short circuit. The current change is gradual during the closing operation of the secondary circuit breaker, which means that the waveform rise is slow due to the drag of the iron core magnetic resistance, suggesting that there may be inrush current.

[0035] Considering that the core frequency domain characteristic of transformer inrush current lies in its accumulation of second harmonic energy, we further analyze the second harmonic content ratio of any circuit breaker closing operation.

[0036] The ratio of the second harmonic current amplitude to the fundamental current amplitude during any circuit breaker closing operation is taken as the second harmonic content ratio during any circuit breaker closing operation.

[0037] Thus, the multi-dimensional electrical characteristics of each circuit breaker closing operation are obtained, including: maximum peak current, maximum instantaneous current rise rate, and second harmonic content ratio.

[0038] Step S103: Calculate the inrush current confidence index based on the nonlinear mapping multidimensional electrical characteristic quantity.

[0039] It should be noted that in actual operation of the distribution network, when a circuit breaker closes to energize, the measured current waveform is easily distorted by severe residual magnetism in the transformer core or the starting of a large-capacity nonlinear load at the end. If the evaluation system relies solely on a single-dimensional electrical characteristic, it is highly prone to evaluation errors. For example, when deep core saturation causes clipping distortion in the current waveform, the calculated second harmonic content ratio will abnormally drop to a low level. In this case, relying solely on frequency domain characteristics will misjudge the inrush current as a short-circuit fault. Therefore, it is necessary to integrate multi-dimensional features to construct an inrush current confidence index, comprehensively assess the true probability that the current closing current belongs to an inrush current, thereby ensuring reliable shielding protection when an inrush current occurs and rapid tripping when a short-circuit fault occurs. Since the discrete values ​​of various nonlinear disturbance characteristics in actual power grids tend to diverge, simple linear combinations cannot normalize and calibrate them. Therefore, this step introduces the hyperbolic tangent mapping function and uses its natural upper and lower bound convergence characteristics to compress the divergent three-dimensional characteristic values ​​into a scale domain of zero to one. At the same time, a logic inversion mechanism is introduced for the time-domain rise rate characteristic to establish a multi-dimensional feature complementary evaluation relationship, ensuring that when a certain dimension of the feature is distorted due to transformer saturation, the other healthy feature dimensions can still maintain a robust probability evaluation.

[0040] Specifically, based on the maximum instantaneous current rise rate, second harmonic content ratio, and maximum peak current of any circuit breaker closing operation, the hyperbolic tangent function is used to perform nonlinear saturation mapping on each characteristic index and then superimposed according to preset weights to calculate the inrush current confidence index corresponding to any circuit breaker closing operation; the specific calculation formula is as follows:

[0041] In the formula, Indicates the first Inrush current confidence index corresponding to the secondary circuit breaker closing operation; Indicates the first Maximum instantaneous current rise rate during the secondary circuit breaker closing operation; Indicates the first The maximum peak current during the closing operation of the secondary circuit breaker; Indicates the first The second harmonic content ratio of the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; , , , respectively, represent the nonlinear mapping sensitivity coefficients corresponding to each item; 0.3, 0.4, and 0.3 represent the decision weights corresponding to each item; This represents the hyperbolic tangent function.

[0042] in, Indicates the first The peak normalized rise rate of the second circuit breaker closing operation reflects the first During the closing operation of the secondary circuit breaker, the current waveform exhibits a slow rise in the leading edge phase. Due to the monotonically increasing hyperbolic tangent function, when the closing waveform rises extremely slowly, causing this ratio to approach zero... Approaching zero Approaching zero When the value approaches 1, it contributes the full weight score to the system; conversely, when a short circuit occurs, at this time... great, Approaching 1, It then approaches zero; Reflects the first The degree of second harmonic distortion excited by the transformer core magnetic saturation during the secondary circuit breaker closing operation, after being positively mapped by the hyperbolic tangent function, when When the value is significantly higher, the mapped function value converges rapidly and approaches 1; when a short circuit occurs... At extremely low values, the mapped function value approaches zero; Reflects the first The transient large current during the closing operation of the secondary circuit breaker causes an overload amplitude to the line's conductive circuit. Since inrush current is usually accompanied by a large current amplitude, therefore... The larger, The closer it is to 1; combining the above comprehensive characteristics of inrush current in three dimensions—time domain waveform steepness, frequency domain second harmonic content, and amplitude overload multiple—the following is obtained: The larger the value, the higher the probability that the current closing current belongs to the transformer inrush current; conversely, the higher the probability that the current closing current belongs to the line short circuit fault.

[0043] It should be added that, in this embodiment, the decision weights for each item are 0.3, 0.4, and 0.3. This is based on the following: the fundamental physical characteristic of transformer inrush current is the second harmonic generated by core saturation; the second harmonic content ratio is the most crucial frequency domain indicator for determining inrush current, hence it is assigned the highest weight of 0.4. Furthermore, the current rise rate and peak overload multiple in the time domain are easily affected by the magnitude of the grid load, thus the remaining weights are evenly distributed as auxiliary evaluation dimensions. , , Used to standardize the nonlinear mapping interval of discrete numerical values ​​in each dimension in the hyperbolic tangent function, with the following value ranges: In this embodiment, we take The basis for setting the above parameter value range is: for the sensitivity coefficient Since the peak normalized rate of rise of normal inrush current is usually less than 200, while the peak normalized rate of rise of short-circuit fault is usually greater than 2000, setting its value range to 0.01 to 0.05 ensures that the low-slope value of the inrush current, after multiplication and amplification, falls exactly into the approximately linear range of the hyperbolic tangent function, while the high-slope value of the short circuit, after amplification, quickly enters the saturation region of the hyperbolic tangent function; for the sensitivity coefficient... Since the second harmonic content of the inrush current typically ranges from 0.15 to 0.35, setting its value range to 10 to 15 ensures that the independent variable of the typical lower limit of the inrush current (0.15) reaches over 1.8 after multiplication, and the corresponding hyperbolic tangent function value reaches over 0.94, ensuring that the real inrush current can stably output a full weighted score in the frequency domain; for the sensitivity coefficient... Setting its value range to 0.2 to 0.5 ensures that when the instantaneous peak current during closing reaches the nominal rated operating current... When the value is 8 to 10 times the value, the mapping independent variable crosses 2 and enters the saturation region, allowing severe inrush to be fully characterized in the amplitude dimension. Implementers can fine-tune within the above range based on the actual confidence level to assess the effect.

[0044] At this point, the inrush current confidence index corresponding to each circuit breaker closing operation is obtained.

[0045] Step S104: Calculate the delay adjustment coefficient to obtain the initial inrush delay.

[0046] It should be noted that if a mapping mechanism with a linear correlation between the confidence index and the delay ratio is adopted, the shielding window extended at a medium confidence level will be excessively expanded. In this case, if a metallic short circuit occurs in the later part of the line, the main control unit will blindly block it. Furthermore, a single confidence index only characterizes the waveform morphology and cannot objectively reflect the actual physical alternating period corresponding to the depletion of the transformer core's residual magnetism. For example, the magnetic field decay period of a very large peak inrush current is significantly longer than that of a slight inrush current. Therefore, a nonlinear adjustment mechanism with dual-channel independent drive is established by combining the confidence index and the maximum peak current excess amplitude.

[0047] Specifically, based on the ratio of the maximum peak current to the nominal rated operating current of any circuit breaker closing operation, and the corresponding inrush current confidence index, and based on the dual-channel independent drive relationship of confidence probability asymptotic saturation and amplitude over-compensation, the delay adjustment coefficient corresponding to any circuit breaker closing operation is calculated; the specific calculation formula is as follows:

[0048] In the formula, Indicates the first The delay adjustment coefficient corresponding to the secondary circuit breaker closing operation; Indicates the first Inrush current confidence index corresponding to the secondary circuit breaker closing operation; Indicates the first The maximum peak current during the closing operation of the secondary circuit breaker; This indicates the nominal rated operating current of the circuit breaker; This indicates the preset first multiplier coefficient; This indicates the preset first growth rate coefficient; This indicates the preset second multiplier coefficient; This indicates a preset second growth rate coefficient; Represents the natural constant.

[0049] Among them, the confidence index The larger the index, the more clearly the closing waveform exhibits the characteristics of inrush current. The corresponding delay increment gradually slows down and approaches the upper limit of saturation as the index increases, thus expanding the protection window while preventing excessive delay growth. Furthermore, the portion of the peak current exceeding the nominal rated operating current independently contributes to the additional delay increment, ensuring that even in cases of extremely large inrush currents causing transformer magnetic saturation and severe second harmonic distortion, the confidence index remains stable. Even under extreme operating conditions with moderate levels, extremely high peak values ​​can still drive the delay to the necessary length. Each of the two incremental channels has an upper limit, and the accumulated delay adjustment coefficient is constrained within a reasonable range, allowing the base delay to adaptively expand and contract between the minimum and maximum allowable values ​​according to the severity of the inrush. The two channels form a progressive and collaborative relationship: the former is responsible for qualitatively determining whether it is an inrush, and the latter assesses the severity of the inrush based on this. Together, they complete the complete mapping from feature recognition to delay decision-making.

[0050] It should be added that, This represents the maximum additional coefficient for the confidence level component, which determines the maximum factor by which the confidence level term can amplify the delay. In this embodiment, it is preferably set to 1.5, meaning that under severe inrush conditions, this term contributes 1.5 times. Adding the base value of 1, we get 2.5 times, and then superimposing... The value can be up to 3 times. This parameter can be set on-site according to the maximum allowable inrush current delay of the circuit breaker, and the range is usually 0.5~2, which can cover most inrush current decay times. This represents the growth rate coefficient of the confidence term, controlling... When the exponent changes from 0 to 1, the exponent term growth rate The larger the value, the lower the confidence index and the faster the time delay increases. In this embodiment, a value of 5 is preferred, so that... When the value approaches 1, the exponential factor partially converges to approximately 0.99, nearing saturation, and a significant increase in delay occurs even with slight inrush. To achieve a more gradual increase in delay due to slight inrush, the value can be reduced. For example, take 2; This represents the maximum additional coefficient for the peak term, which determines the maximum delay multiple contributed by the peak term. In this embodiment, it is preferably set to 0.5 to prevent excessive delay due to pure amplitude drive. For example, an additional 0.5 times delay is added when the current is 20 times the rated current. If the upper limit of the inrush current delay is strictly required on site, it can be reduced to 0.2. This represents the growth rate coefficient of the peak term, i.e., the sensitivity of the portion exceeding the peak value to delay. In this embodiment, it is preferably set to 0.2, so that when the peak current reaches 10 times the nominal rated operating current, exponent term Approaching saturation, this ensures the peak contribution curve is differentiated within the common inrush range, with no significant increase beyond that range. To achieve a smoother peak effect, the peak contribution can be reduced... For example, take 0.1.

[0051] Specifically, at the underlying level, the inherent basic inrush current delay of the circuit breaker operating mechanism and the maximum permissible inrush current delay of the circuit breaker are obtained by directly reading the hardware configuration register of the circuit breaker operating mechanism control board. The basic inrush current delay is corrected using the delay adjustment coefficient corresponding to any circuit breaker closing operation, and combined with the maximum permissible inrush current delay, the preliminary inrush current delay corresponding to any circuit breaker closing operation is obtained. The specific calculation formula is as follows:

[0052] In the formula, Indicates the first Preliminary inrush current delay corresponding to the secondary circuit breaker closing operation; Indicates the basic inrush delay; Indicates the first The delay adjustment coefficient corresponding to the secondary circuit breaker closing operation; Indicates the maximum permissible inrush current delay of the circuit breaker; This represents a function that takes the minimum value. Indicates the first The theoretical interlocking time corresponding to the circuit breaker closing operation.

[0053] in, This reflects the theoretically required overcurrent blocking time under the current closing waveform characteristics. The larger the product value, the longer the alternating cycle required for the residual magnetism of the transformer core to be exhausted. Substituting this value together with the maximum allowable inrush current delay into the minimum value function to take the minimum value limits the disorderly extension of the blocking window, prevents the short-circuit high current from continuously heating and burning out the switchgear due to excessive overcurrent shielding time, and ensures the timeliness of the protection tripping action.

[0054] For example, Figure 2This diagram illustrates the computational link from electrical characteristics to adaptive inrush current delay. The left input terminal aggregates the three-dimensional electrical characteristics extracted in real time: the maximum instantaneous current rise rate, the second harmonic content ratio, and the maximum peak current. These three-dimensional characteristics are first fed into a nonlinear mapping evaluation unit, which uses a multi-dimensional complementary mechanism with a high second harmonic weight to calculate the inrush current confidence index. Subsequently, the confidence index and the maximum peak current index jointly drive the intermediate-stage dual-channel saturation adjustment module. Based on the dual-drive logic that a higher confidence index means a more sufficient delay and a higher peak current means a greater delay, the module outputs a delay adjustment coefficient to adaptively calculate the inrush current delay, i.e., the initial inrush current delay.

[0055] At this point, the initial inrush current delay corresponding to each circuit breaker closing operation is obtained.

[0056] Step S105: Perform short-circuit bypass processing and blocking delay verification.

[0057] It should be noted that if a metallic short-circuit fault occurs at the exact moment the circuit breaker closes and energizes, the initial delay will forcibly lock the circuit breaker's overcurrent trip circuit for hundreds of milliseconds. During this lockout period, the large short-circuit current will continuously impact the measurement circuit, instantly burning out the autonomous power-taking coil of the electronic PT and the circuit breaker contacts. Therefore, a bypass branch is installed in parallel at the bottom layer. When a short-circuit characteristic is detected, the delay is forcibly reset to zero and bypassed by the shield counter. Considering the occasional nature of the sampling data of a single power frequency cycle being affected by instantaneous spike interference, which may lead to delay miscalculation, a dual-cycle time-domain smoothing verification mechanism for simultaneous closing is introduced, and the residual magnetism accumulation trend is sensed, thereby eliminating the impact of inrush current false triggering on the reliability of the electronic PT's autonomous power supply.

[0058] Specifically, a dual-condition hardware bypass process is executed, ensuring that the actual inrush current delay corresponding to any circuit breaker closing operation satisfies the piecewise function expression:

[0059] In the formula, Indicates the first The actual inrush current delay corresponding to the secondary circuit breaker closing operation; Indicates the first Maximum instantaneous current rise rate during the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; Indicates the first The second harmonic content ratio of the secondary circuit breaker closing operation; This represents the preset short-circuit fault rise rate threshold. This indicates the preset upper limit of the second harmonic of a short-circuit fault; Indicates the first Preliminary inrush current delay corresponding to the circuit breaker closing operation.

[0060] The piecewise function utilizes the orthogonal difference between inrush current and short circuit in the time and frequency domains: when both criteria of extremely high rated normalized rise rate and extremely low second harmonic are met simultaneously, the waveform is directly identified as a metallic short circuit fault; at this time, the piecewise function immediately triggers the uplink branch to output a zero value, and the main control unit completely skips the inrush current delay and immediately drives the instantaneous trip, rigidly controlling the fault clearing time to within forty milliseconds; when any condition is not met, the piecewise function triggers the downlink branch to output a preliminary inrush current delay and sends it to the next module for smoothing verification.

[0061] It should be added that, in this embodiment, the short-circuit fault rise rate threshold and the upper limit of the second harmonic of the short-circuit fault are respectively taken as... and For the rate of rise threshold, in a 50Hz AC system, the intrinsic derivative extremum benchmark of a standard sine wave is: When the short-circuit current reaches the nominal rated operating current When it is 20 times, its standardized derivative theoretical value is The standardized rise rate of typical short-circuit faults in distribution networks is usually in At levels above [amount missing]; simultaneously, even for the largest inrush current with the most severe saturation distortion, its normalized rate of rise is suppressed by the physical inductance. Therefore, it is therefore adjusted to The value is much higher than the 314 for normal energization and the 2000 for the most severe inrush current, which defines the threshold for the short-circuit current surge slope. For the upper limit of the second harmonic, the current waveform when a metallic short circuit occurs in the distribution network is close to a pure sine wave, and its second harmonic content is usually less than 5%. The second harmonic of the inrush current excited by the saturation of the transformer core is typically distributed between 15% and 30%. Setting it to 8%, or 0.08, leaves a 3% measurement noise absorption margin above the short-circuit background of 5%, and is 7% lower than the lower limit of the inrush current of 15%, forming an orthogonal judgment boundary without overlapping areas.

[0062] If the piecewise function outputs the initial inrush current delay, the system initiates a routine verification process: extracting the initial inrush current delays calculated from two consecutive circuit breaker closing events within the same event, determining the smaller of the two, and calculating the absolute value of the difference between them; when the absolute value of the difference is greater than 30% of the smaller value, it is determined that the single power frequency sampling is distorted due to high-frequency spike interference from contact bounce, and the system selects the larger of the two as the final actual inrush current delay; when the absolute value of the difference is less than or equal to 30% of the smaller value, it is determined that the power frequency measurements before and after are within the normal attenuation measurement fluctuation range, and the system selects the average of the two as the final actual inrush current delay; and writes the final actual inrush current delay into the protection logic module and starts a timer. During this delay period, the overcurrent protection is completely disabled, and the standard three-stage overcurrent protection is instantly enabled after the timer expires.

[0063] The mathematical basis for the smaller value of 30% is that the natural attenuation rate of the inrush current of the distribution transformer during two adjacent power frequency cycles is typically between 10% and 20%, while the distortion deviation rate of a single spectrum measurement caused by the contact bounce arcing of the circuit breaker is usually as high as 50% or more. That is, using the smaller value of 30% as the judgment boundary leaves sufficient measurement tolerance margin above the normal attenuation rate of the inrush current, and is below the lower limit of the contact interference distortion, thus forming an orthogonal isolation boundary that takes into account both inclusiveness and sensitivity.

[0064] Furthermore, the main control unit retrieves data records of each circuit breaker closing operation and its two consecutive preceding circuit breaker closing operations in real time. If the final actual inrush current delay is equal to the maximum allowable inrush current delay, it is determined that the line section exhibits an abnormal accumulation trend of DC residual magnetism. The controller immediately issues an abnormal residual magnetism warning through the local display screen or remote communication interface, prompting maintenance personnel to check the distribution transformer or line parameters. At the same time, all protection action events are accompanied by a snapshot of the characteristic quantity of this closing operation, which is synchronously uploaded to the cloud platform main station to support the fault tracing and equipment health management of the distribution network.

[0065] For example, Figure 3 This is a schematic diagram of the circuit breaker closing operation judgment process. The execution link is divided into two parallel branches. The upward branch is a short-circuit bypass branch, which is connected to a logic AND gate by two orthogonal conditions: the rated standardized rise rate exceeding the limit and the second harmonic extremely low. The AND gate is turned on only when both conditions are met, and the zero-second delay triggers instantaneous tripping to achieve rapid clearing of short-circuit faults. The downward branch is a conventional inrush current adaptive blocking branch. When the above AND gate is not turned on, the signal automatically falls into this branch, and the soft shielding count is performed according to the preliminary inrush current delay calculated above. After the timing period is zeroed, the standard three-stage overcurrent protection enable is restored instantly.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PTs, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it performs the following steps: The original discrete sampling sequence of the three-phase current is collected for each circuit breaker closing operation. After preprocessing, the sampling sequence of the DC instantaneous current of each phase, the amplitude of the fundamental current, and the amplitude of the second harmonic current are obtained. The maximum peak current is extracted based on the instantaneous DC current sampling sequence of each phase; the maximum instantaneous current rise rate is extracted based on the maximum ratio of the current difference between two adjacent discrete sampling points in the original discrete sampling sequence of each phase current to the sampling interval; the second harmonic content ratio is obtained based on the ratio of the second harmonic current amplitude to the fundamental current amplitude. The inrush current confidence index is obtained by using a nonlinear mapping function based on the maximum instantaneous current rise rate, the second harmonic content ratio, and the maximum peak current. The delay adjustment factor is calculated based on the ratio of the maximum peak current to the nominal rated operating current and the inrush current confidence index. The inherent basic inrush current delay of the circuit breaker operating mechanism is corrected based on the delay adjustment coefficient, and the initial inrush current delay is obtained with the maximum allowable inrush current delay as the upper limit. Determine whether the maximum instantaneous current rise rate and the second harmonic content ratio meet the preset short-circuit judgment conditions. If they meet, output zero-delay trigger instantaneous tripping. If they do not meet, perform smoothing verification on the preliminary inrush current delay to obtain the final actual inrush current delay, and shield the overcurrent protection action during the final actual inrush current delay.

2. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The extraction of the maximum peak current based on the instantaneous DC de-current sampling sequence of each phase includes: The maximum value in the DC instantaneous current sampling sequence of each phase is extracted as the peak current of each phase, and the maximum value among the three phase peak currents is obtained as the maximum peak current.

3. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The extraction of the maximum instantaneous rate of rise of the current includes: The maximum value of the rate of change of current between two adjacent discrete sampling points in the original discrete sampling sequence of current for each phase is obtained as the maximum value of each phase; the maximum value among the three phase values ​​is extracted as the maximum instantaneous rate of rise of current.

4. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The surge confidence index satisfies the expression: ； In the formula, Indicates the first Inrush current confidence index corresponding to the secondary circuit breaker closing operation; , , They represent the first The maximum instantaneous current rise rate, maximum peak current, and second harmonic content ratio of the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; , , , respectively, represent the nonlinear mapping sensitivity coefficients corresponding to each item; 0.3, 0.4, and 0.3 represent the decision weights corresponding to each item; This represents the hyperbolic tangent function.

5. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The delay adjustment coefficient satisfies the expression: ； In the formula, , , They represent the first The delay adjustment coefficient, inrush current confidence index and maximum peak current corresponding to the secondary circuit breaker closing operation; This indicates the nominal rated operating current of the circuit breaker; This indicates the preset first multiplier coefficient; This indicates the preset first growth rate coefficient; This indicates the preset second multiplier coefficient; This indicates a preset second growth rate coefficient; Represents the natural constant.

6. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The process of obtaining the initial inrush delay includes: Multiply the inherent basic inrush current delay of the circuit breaker operating mechanism by the delay adjustment coefficient to obtain the theoretical blocking time; take the minimum value between the theoretical blocking time and the maximum allowable inrush current delay of the circuit breaker as the initial inrush current delay.

7. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The determination of whether the maximum instantaneous current rise rate and the second harmonic content ratio meet the preset short-circuit judgment conditions includes: If the ratio of the maximum instantaneous current rise rate to the nominal rated operating current of the circuit breaker is greater than the preset short-circuit fault rise rate threshold, and the second harmonic content ratio is less than the preset upper limit of the second harmonic of the short-circuit fault, then the preset short-circuit judgment condition is satisfied; otherwise, the preset short-circuit judgment condition is not satisfied.

8. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The process of smoothing and verifying the initial inrush delay to obtain the final actual inrush delay includes: Extract the preliminary inrush current delay calculated from two consecutive circuit breaker closing events within the same event, determine the smaller of the two values, and calculate the absolute value of the difference between them. When the absolute value of the difference is greater than 30% of the smaller value, select the larger of the two values ​​as the final actual inrush current delay. When the absolute value of the difference is less than or equal to 30% of the smaller value, select the arithmetic mean of the two values ​​as the final actual inrush current delay.

9. The primary and secondary integrated pole-mounted circuit breaker for realizing autonomous power supply of electronic PT as described in claim 1, characterized in that, The preprocessing process, which acquires the instantaneous DC current sampling sequence, fundamental current amplitude, and second harmonic current amplitude for each phase, includes: The discrete sequence of the non-periodic decaying DC component contained in the original discrete sampling sequence of the three-phase current is calculated using the least squares method attenuation DC fitting algorithm. The original discrete sampling sequence of the three-phase current is then subtracted point by point from the discrete sequence of the non-periodic decaying DC component to obtain the instantaneous DC de-current sampling sequence of each phase. A second-order digital low-pass filter is applied to the instantaneous DC de-current sampling sequence of each phase to obtain the filtered sequence, and the filtered sequence is multiplied by the Hanning window function to obtain the smoothed windowed sequence. The smoothed windowed sequence is then subjected to a fast Fourier transform to generate a discrete spectrum sequence. The magnitude of the fundamental component in the discrete spectrum sequence is read as the fundamental current amplitude, and the magnitude of the second harmonic component is read as the second harmonic current amplitude.

Images