An intelligent control box power distribution system supporting automatic reclosing

Abstract

This invention relates to the field of power supply or distribution, specifically to an intelligent control box power distribution system supporting automatic reclosing. At the instant the fault current is interrupted, the transient recovery voltage waveform and the residual current waveform across the circuit breaker contacts are acquired, and the transient recovery voltage rise rate characteristic and dielectric recovery strength change characteristic are extracted. A dynamic impedance recovery model for the downstream load is established, and the expected recovery value of the load impedance at the moment of reclosing is calculated based on the load type and power outage time. Using the above characteristics and the expected recovery value as input, the target phase angle is calculated through a closing phase angle decision function, and the reclosing delay time is dynamically adjusted so that the circuit breaker performs closing when the dielectric recovery strength is greater than the transient recovery voltage and the load impedance is in a stable range. This invention suppresses secondary overcurrent and system oscillations caused by reclosing and reduces the probability of arc reignition at the circuit breaker contacts.

Description

Technical Field

[0001] This invention relates to the field of power supply or distribution, specifically to an intelligent control box power distribution system that supports automatic reclosing. Background Technology

[0002] Currently, after a power distribution system trips due to a fault, automatic reclosing devices typically employ a fixed delay mechanism or rely solely on a line voltage de-energization signal to attempt to restore power. When the circuit breaker interrupts the fault current, the control system starts an internal timer, waiting for a preset fixed time to elapse, or issuing a closing command to the circuit breaker operating mechanism once the line voltage is detected to be below a set threshold. This reclosing logic treats the line state after the fault is cleared as static, failing to consider the physical state changes of the circuit breaker contacts at the moment of contact breaking, or the dynamic evolution of downstream loads during the power outage.

[0003] The existing automatic reclosing control logic does not correlate the dielectric recovery process between contacts after fault disconnection with the dynamic evolution of downstream load impedance. This results in the circuit breaker facing a situation where the dielectric has not been fully restored or the load impedance is in an extremely low state at the moment of reclosing, which causes secondary current surges and arc reignition between contacts during reclosing operation. This constitutes the core technical problem of automatic reclosing failure and system electrical surges in the existing technology due to the mismatch between the reclosing timing and the actual physical state of the system. Summary of the Invention

[0004] The purpose of this invention is to provide an intelligent control box power distribution system that supports automatic reclosing, which can effectively solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A smart control box power distribution system that supports automatic reclosing includes: a disconnection status monitoring circuit, used to acquire the transient recovery voltage waveform and the residual current waveform of the line at the moment when the power distribution system disconnects the fault current; A feature extraction circuit is used to extract the transient recovery voltage rise rate feature and the dielectric recovery strength change feature from the transient recovery voltage waveform and the residual current waveform of the line; Impedance modeling circuit is used to establish a dynamic impedance recovery model for the downstream load of the distribution box, and calculate the expected recovery value of the load impedance at the moment of re-coincidence based on the load type identification results and power failure time. The timing decision circuit is used to take the transient recovery voltage rise rate characteristic, the dielectric recovery strength change characteristic and the expected recovery value as inputs, calculate the target phase angle for the circuit breaker moving contact closure through the constructed closing phase angle decision function, and dynamically adjust the reclosing delay time according to the target phase angle. The execution drive circuit is used to output a closing operation signal to the circuit breaker operating mechanism when the reclosing delay time expires, the dielectric recovery strength is greater than the transient recovery voltage, and the load impedance is in the stable range.

[0006] The circuit breaker status monitoring circuit includes a high-frequency broadband voltage sensor and a Rogowski coil current sensor. The high-frequency broadband voltage sensor and the Rogowski coil current sensor are respectively disposed on both sides of the moving and stationary contacts of the circuit breaker and on the outgoing line side, and are connected to the feature extraction circuit through a synchronous clock trigger circuit. After receiving the interruption trigger signal, the feature extraction circuit performs variational mode decomposition on the transient recovery voltage waveform and the residual line current waveform, filters out the power frequency component and high-frequency white noise, obtains the residual intrinsic mode function, and performs differential operation on the residual intrinsic mode function to obtain the transient recovery voltage rise rate feature. At the same time, it performs exponential fitting on the attenuation envelope of the residual line current waveform to obtain the dielectric recovery strength change feature.

[0007] The impedance modeling circuit includes a load characteristic identification register and an impedance calculation logic array. The load characteristic identification register stores the voltage and current phasor trajectories within a predetermined time window before the fault, and classifies the load type into rotating motor type, constant impedance type and power electronic conversion type according to the harmonic distortion rate and phase difference of the voltage and current phasor trajectories. The impedance calculation logic array matches the corresponding impedance recovery time-varying function according to the load type, substitutes the power loss time into the impedance recovery time-varying function, and superimposes the ambient temperature correction coefficient to calculate the expected recovery value of the load impedance at the moment of re-coincidence. The impedance recovery time-varying function corresponding to the rotating motor type includes a transient reactance term that decays exponentially with the power loss time.

[0008] The timing decision circuit includes a phase mapping memory and a delay compensation counter. The phase mapping memory pre-stores a multidimensional envelope surface of the dielectric recovery strength and the transient recovery voltage rise rate. The timing decision circuit projects the expected recovery value onto the multidimensional envelope surface to determine the safe closing phase interval, and searches for the power supply voltage zero crossing point within the safe closing phase interval as the target phase angle. The delay compensation counter calculates the phase advance compensation amount based on the inherent closing time of the circuit breaker operating mechanism and the control command transmission delay. It subtracts the delay difference corresponding to the phase advance compensation amount from the target phase angle to generate the actual trigger delay, and outputs the actual trigger delay as the reclosing delay time.

[0009] The execution drive circuit includes a state verification logic gate and a closing coil drive switch. The state verification logic gate obtains the latest measured value of dielectric recovery strength and the updated value of expected recovery value in real time before the reclosing delay time expires, and performs a logical AND operation to determine whether the measured value of dielectric recovery strength is continuously greater than the transient recovery voltage and whether the updated value of expected recovery value falls within the preset safe impedance range. When the logical AND operation outputs a high level, the closing coil drives the switching transistor to conduct, and outputs the closing operation signal to the circuit breaker operating mechanism; When the output of the logical AND operation is low, the closing coil drive switch remains off and triggers the reclosing lockout state.

[0010] The timing decision circuit also includes an accelerated reclosing judgment comparator. The disconnection state monitoring circuit transmits the decay time constant of the residual current waveform of the line to the accelerated reclosing judgment comparator in real time. When the decay time constant is less than the preset non-inductive load threshold and the transient recovery voltage rise rate characteristic is less than the preset low stress threshold, the accelerated reclosing judgment comparator bypasses the conventional calculation process of the closing phase angle decision function, directly generates a zero-delay closing command and outputs it to the execution drive circuit. After receiving the zero-delay closing command, the execution drive circuit forcibly performs the closing operation at the first zero-crossing point of the power supply voltage after the fault arc is extinguished.

[0011] The feature extraction circuit further includes a mode number adaptive regulator and a polarity checker. The mode number adaptive regulator dynamically calculates the number of intrinsic mode function layers of the variational mode decomposition based on the spectral entropy of the transient recovery voltage waveform, and performs decomposition based on the number of intrinsic mode function layers to eliminate mode aliasing. The polarity checker monitors the voltage polarity reversal state of the residual intrinsic mode function at the current zero-crossing point. When the voltage polarity reversal state does not meet the expected arc-extinguishing characteristics, it determines that there is a secondary reignition between the contacts and triggers the disconnection state monitoring circuit to re-execute the waveform acquisition and feature extraction operation.

[0012] The impedance calculation logic array also includes a residual voltage frequency tracker, which collects the residual voltage signal of the rotating motor-type load port in real time during power failure and extracts the attenuation frequency and initial phase of the residual voltage signal through a phase-locked loop. The impedance calculation logic array introduces the attenuation frequency and the initial phase into the impedance recovery time-varying function corresponding to the rotating motor type, corrects the phase angle offset of the transient reactance term, and calculates the expected peak value of the back-feeding current of the rotating motor type load at the moment of overlap based on the corrected phase angle offset. The expected peak value of the back-feeding current is superimposed on the expected recovery value to correct the impedance drop depth.

[0013] The phase mapping memory is connected to a surface correction calculator. The surface correction calculator obtains the cumulative breaking current value of the circuit breaker and the current ambient temperature value, calculates the contact wear correction coefficient based on the cumulative breaking current value, and calculates the gas medium density correction coefficient based on the current ambient temperature value. The contact wear correction coefficient is multiplied by the gas medium density correction coefficient to obtain the comprehensive derating coefficient. The boundary of the multidimensional envelope surface is shrunk and scaled inward using the comprehensive derating coefficient. The scaled multidimensional envelope surface replaces the original pre-stored surface as the calculation benchmark for the current safe closing phase interval, so as to eliminate the safety margin reduction interval caused by contact aging and medium deterioration.

[0014] The execution drive circuit also includes a closing process interceptor. During the process of the closing coil driving the switch tube to conduct and the circuit breaker moving contact moving towards the stationary contact, the closing process interceptor continuously monitors the rate of change of the transient current of the line and the slope of the voltage drop between the contacts. When the transient current change rate is greater than the preset inrush current threshold and the voltage drop slope is greater than the preset abnormal conduction slope, it is determined that the circuit breaker is closing without eliminating the fault. The interceptor immediately generates a forced disconnect pulse during the closing process. The forced disconnect pulse covers the closing operation signal and turns off the closing coil drive switch. At the same time, it triggers the shunt trip coil to stop the closing movement of the moving contact and causes it to disconnect in the reverse direction.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention collects transient recovery voltage waveforms and residual line current waveforms, extracts transient recovery voltage rise rate characteristics and dielectric recovery strength change characteristics, establishes a dynamic impedance recovery model for downstream loads to calculate expected recovery values, inputs the above characteristics and values ​​into the closing phase angle decision function to calculate the target phase angle, and dynamically adjusts the reclosing delay time, so that the circuit breaker performs closing when the dielectric recovery strength is greater than the transient recovery voltage and the load impedance is in a stable range, thereby suppressing secondary overcurrent and system oscillations caused by reclosing operations and reducing the probability of arc reignition of circuit breaker contacts during reclosing.

[0016] 2. Variational mode decomposition is performed on the transient recovery voltage waveform and the residual line current waveform to obtain the residual intrinsic mode function, filtering out interference from power frequency components and high-frequency white noise, thus improving the accuracy of feature extraction. Load types are classified according to the harmonic distortion rate and phase difference of the voltage and current phasor trajectories, and corresponding impedance recovery time-varying functions are matched to avoid homogenizing the impedance recovery process of different loads. The multidimensional envelope surface is scaled and corrected using the contact wear correction coefficient and the gas medium density correction coefficient, eliminating the safety margin reduction range caused by contact aging and medium deterioration, ensuring the operational reliability under long-term operation. During the closing process, the transient current change rate and voltage drop slope are monitored and a forced disconnection pulse is generated, realizing the immediate interception of faults that have not been eliminated. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall workflow of the intelligent control box power distribution system supporting automatic reclosing according to the present invention. Figure 2 This is a flowchart of the discontinuity state monitoring and variational mode decomposition feature extraction of the present invention; Figure 3 This is a flowchart of the load type identification and dynamic impedance recovery value calculation of the present invention; Figure 4 This is a flowchart of the closing phase angle decision and delay compensation calculation of the present invention; Figure 5 This is a flowchart of the accelerated overlap determination and secondary reignition detection process of the present invention; Figure 6 This is a flowchart of the multidimensional envelope surface correction and fault interception process during the closing process of the present invention. Detailed Implementation

[0018] Please refer to Figure 1This embodiment provides an intelligent control box power distribution system supporting automatic reclosing, integrated within a low-voltage distribution box and electrically connected to the circuit breaker operating mechanism, enabling intelligent reclosing control after a power line fault disconnection. The system adopts a modular circuit design, with each functional circuit interacting via an internal parallel bus. All data processing is completed within the hardware circuit, without relying on external processors or software programs. The system has an independent power supply module that draws power from the power distribution line, providing a stable DC power supply to each functional circuit after rectification, filtering, and linear voltage regulation. The power supply module also includes a backup supercapacitor bank. When the power distribution line loses power, the backup supercapacitor bank automatically activates, ensuring the system can continue to perform waveform acquisition, feature extraction, impedance calculation, and timing decision-making during power outages. The capacity of the backup supercapacitor bank can support continuous system operation for a preset time. The system connects to the circuit breaker operating mechanism via a dedicated interface circuit, which includes a closing signal output port, a opening signal output port, an auxiliary contact input port, and a status feedback input port. The closing signal output port outputs a closing operation signal to the closing coil of the circuit breaker operating mechanism, while the opening signal output port outputs an opening operation signal to the shunt trip coil of the circuit breaker operating mechanism. The auxiliary contact input port receives status signals from the circuit breaker's auxiliary contacts, and the status feedback input port receives operating status feedback signals from the circuit breaker operating mechanism. The interface circuit employs opto-isolation design to achieve electrical isolation between the system and the circuit breaker operating mechanism, preventing electromagnetic interference generated by the circuit breaker operating mechanism from affecting the normal operation of the system.

[0019] The circuit breaker tripping status monitoring circuit monitors the tripping status of the circuit breaker in real time. When the circuit breaker trips due to a fault current, it immediately triggers waveform acquisition, acquiring the transient recovery voltage waveform and the residual current waveform across the circuit breaker contacts at the instant the fault current is tripped. The circuit breaker tripping status monitoring circuit is connected to the incoming and outgoing sides of the circuit breaker via voltage and current sampling channels, respectively, to acquire line voltage and current signals in real time. The circuit breaker tripping status monitoring circuit contains a fault tripping detection comparator that compares the acquired line current signal with a preset fault current threshold. When the line current exceeds the fault current threshold and the duration exceeds the preset fault determination time, a fault is determined to have occurred in the power distribution system. Simultaneously, the circuit breaker's auxiliary contact status is monitored; when the auxiliary contact switches from closed to open, it is confirmed that the circuit breaker has completed the fault current tripping operation. At the instant the circuit breaker trips, the tripping status monitoring circuit triggers a high-speed sample-and-hold circuit to synchronously acquire the transient recovery voltage waveform and the residual current waveform across the circuit breaker contacts. The sampling frequency is set to capture the transient process completely, and the sampling duration covers the entire process from contact separation to the basic recovery of the dielectric. The acquired waveform data is converted from analog to digital and then transmitted via an internal parallel bus to the feature extraction circuit for further processing.

[0020] The feature extraction circuit receives waveform data output from the interruption state monitoring circuit, performs preprocessing and feature extraction operations on the waveform, and obtains the transient recovery voltage rise rate feature and the dielectric recovery strength change feature, respectively. The feature extraction circuit internally includes a waveform buffer and a feature calculation logic unit. The waveform buffer adopts a dual-port random access memory structure to store the transient recovery voltage waveform and residual line current waveform data transmitted by the interruption state monitoring circuit. The dual-port design allows both the interruption state monitoring circuit and the feature calculation logic unit to access the memory simultaneously, improving data transmission efficiency. The feature calculation logic unit first preprocesses the transient recovery voltage waveform, eliminating DC offset in the waveform using a DC component removal algorithm and correcting baseline drift using a baseline correction algorithm. Then, it calculates the rising edge slope of the waveform to obtain the transient recovery voltage rise rate feature. For the residual line current waveform, the feature calculation logic unit extracts the attenuation envelope of the waveform, analyzes the changing trend of the envelope, and obtains the dielectric recovery strength change feature. The transient recovery voltage rise rate characteristic reflects the speed at which the voltage across the contact gap recovers, while the dielectric recovery strength change characteristic reflects the recovery process of the dielectric insulation strength of the contact gap. These two characteristics together characterize the physical state of the circuit breaker contacts after they are disconnected.

[0021] The impedance modeling circuit continuously monitors the operating status of downstream loads before a fault occurs, storing load operating data within a predetermined time window before the fault. When a fault occurs, it identifies the load type based on the stored load operating data and calculates the expected recovery value of the load impedance at the moment of reconnection, taking into account the power loss time. The impedance modeling circuit internally includes a load data storage unit and an impedance calculation unit. During normal system operation, the load data storage unit collects and stores voltage and current phasor data of downstream loads at a fixed sampling frequency, with the storage time window covering a period that accurately reflects the load characteristics. When a fault occurs, the impedance calculation unit reads the voltage and current phasor data within the predetermined time window before the fault from the load data storage unit, calculates the load's average power factor and harmonic content, and identifies the type of downstream load based on the calculation results. The impedance calculation unit internally stores impedance recovery characteristic curves corresponding to different types of loads. These characteristic curves are obtained through extensive experimental testing and simulation calculations and can accurately reflect the impedance change patterns of different types of loads after power loss. The impedance calculation unit calls the corresponding characteristic curve based on the identified load type, substitutes the power loss time calculated from the circuit breaker tripping moment into the characteristic curve, and obtains the expected recovery value of the load impedance at the moment of reclosing. The expected recovery value of the load impedance reflects the electrical state of the downstream load at the moment of reclosing and directly affects the magnitude of the current surge during reclosing operation.

[0022] The timing decision circuit receives the transient recovery voltage rise rate characteristic, dielectric recovery strength change characteristic, and expected recovery value output by the feature extraction circuit, as well as the expected recovery value output by the impedance modeling circuit. Using these three parameters as input, it calculates the target phase angle for the circuit breaker moving contact closure through a constructed closing phase angle decision function, and dynamically adjusts the reclosing delay time based on the target phase angle. The timing decision circuit internally includes a decision function calculation unit and a delay generation unit. The decision function calculation unit uses hardware logic circuits to implement the calculation of the closing phase angle decision function, employing a pipelined structure to complete the calculation in a very short time. The closing phase angle decision function is constructed based on the matching relationship between dielectric recovery strength and transient recovery voltage, as well as the influence of load impedance on the closing current. The goal is to find an optimal closing phase angle that ensures the dielectric recovery strength during reclosing is greater than the transient recovery voltage, while the load impedance remains within a stable range that limits the closing current. The delay generation unit calculates the required reclosing delay time based on the calculated target phase angle and the phase information of the current power supply voltage, and outputs this delay time to the execution drive circuit.

[0023] The execution drive circuit receives the reclosing delay time output by the timing decision circuit and starts an internal timer. Before the reclosing delay time expires, it verifies the current dielectric recovery strength and load impedance status in real time. When the dielectric recovery strength is greater than the transient recovery voltage and the load impedance is within the stable range, it outputs a closing operation signal to the circuit breaker operating mechanism, driving the circuit breaker to complete the closing operation. The execution drive circuit internally includes a timer and a status verification unit. The timer uses a high-precision crystal oscillator as its clock source, and the timing error does not exceed a preset value. During the countdown, the status verification unit obtains the latest measured value of dielectric recovery strength from the feature extraction circuit and the latest updated value of expected recovery value from the impedance modeling circuit. When the timer counts down to the moment before the reclosing delay time expires, the status verification unit compares the current measured value of dielectric recovery strength with the transient recovery voltage, and simultaneously compares the updated value of expected recovery value with the preset safe impedance range. When both conditions are met simultaneously, the status verification unit outputs a closing permission signal, drives the closing coil to turn on the switching transistor, and outputs a closing operation signal to the circuit breaker operating mechanism. If either of the above two conditions is not met, the status verification unit outputs a prohibition signal for closing, the closing coil drives the switch to remain in the off state, and the closing operation is not performed. The relationship between the transient recovery voltage rise rate and the dielectric recovery strength under different fault types is shown in Table 1.

[0024] Table 1. Relationship between transient recovery voltage rise rate and dielectric recovery strength under different fault types. Fault type Transient recovery voltage rise rate range Initial value of medium recovery strength Time for the medium to recover its strength to reach a stable value Single-phase ground fault Low-medium middle short Two-phase short circuit fault Medium-high Low middle Three-phase short circuit fault high Extremely low long Intermittent faults Medium-high Low middle Arc fault high Low long Table 1 lists the range of transient recovery voltage rise rate and dielectric recovery strength variation parameters corresponding to several common fault types in power distribution systems. Under different fault types, the magnitude and nature of the fault current differ, leading to significant differences in the transient recovery voltage rise rate and dielectric recovery process after circuit breaker disconnection. Single-phase ground faults have smaller fault currents, lower transient recovery voltage rise rates, and faster dielectric recovery speeds; three-phase short-circuit faults have the largest fault currents, the highest transient recovery voltage rise rates, and the slowest dielectric recovery speeds. Arc faults, due to the unstable combustion of the arc, cause high-frequency oscillations in the transient recovery voltage waveform, making the dielectric recovery process more complex. Statistical analysis of the characteristic parameters under different fault types can provide basic data support for constructing the closing phase angle decision function, enabling the decision function to adapt to different fault scenarios.

[0025] This embodiment acquires the transient recovery voltage waveform and residual current waveform of the line at the moment of circuit breaker disconnection through the disconnection state monitoring circuit, extracts feature parameters that reflect the physical state of the contacts through the feature extraction circuit, calculates the expected impedance recovery value of the downstream load at the moment of reclosing through the impedance modeling circuit, dynamically calculates the optimal closing phase angle and reclosing delay time through the timing decision circuit, and executes the closing operation when the safety conditions are met through the execution drive circuit, thereby achieving the matching of automatic reclosing timing with the actual physical state of the system.

[0026] In a preferred embodiment, reference Figure 2The circuit breaker's fault condition monitoring circuit includes a high-frequency broadband voltage sensor and a Rogowski coil current sensor. These sensors are respectively positioned on both sides of the moving and stationary contacts and on the outgoing line side of the circuit breaker, and are connected to the feature extraction circuit via a synchronous clock trigger circuit. The high-frequency broadband voltage sensor employs a capacitive voltage divider structure, exhibiting wide-bandwidth response characteristics. It can accurately acquire voltage signals from DC to several megahertz frequencies, ensuring that high-frequency components in the transient recovery voltage waveform are not attenuated or distorted. The voltage division ratio of the high-frequency broadband voltage sensor is precisely calibrated and remains constant throughout the entire operating frequency range, guaranteeing the accuracy of voltage measurement. The Rogowski coil current sensor uses a hollow coil structure, offering advantages such as good linearity, fast response speed, and no magnetic saturation. It can accurately acquire the weak current signal remaining in the line after fault disconnection. The output signal of the Rogowski coil current sensor is processed by an integrator and converted into a voltage signal proportional to the line current, which is then transmitted to subsequent circuits. The synchronous clock trigger circuit incorporates a high-precision temperature-compensated crystal oscillator to generate a unified synchronous clock signal, which is output to the high-frequency broadband voltage sensor, the Rogowski coil current sensor, and the feature extraction circuit. This ensures strict synchronization between the voltage and current waveform acquisition processes, with the sampling time error not exceeding a preset value. When the circuit breaker interrupts the fault current, the synchronous clock trigger circuit simultaneously sends sampling trigger signals to the high-frequency broadband voltage sensor and the Rogowski coil current sensor at the instant the auxiliary contact state switches, initiating synchronous sampling. The acquired voltage and current waveform data, after being marked by the synchronous clock, are transmitted to the feature extraction circuit via the internal parallel bus.

[0027] After receiving the interruption trigger signal, the feature extraction circuit performs variational mode decomposition on the transient recovery voltage waveform and the residual line current waveform to filter out power frequency components and high-frequency white noise, obtain the residual intrinsic mode functions (EMFs), and perform differential operations on the residual EMFs to obtain the transient recovery voltage rise rate characteristics. Simultaneously, it performs exponential fitting on the attenuation envelope of the residual line current waveform to obtain the dielectric recovery strength variation characteristics. Variational mode decomposition is an adaptive signal decomposition method that can decompose complex non-stationary signals into several EMFs with different center frequencies, each with a finite bandwidth. The goal of variational mode decomposition is to find a set of EMFs such that the sum of the estimated bandwidths of each EMF is minimized, while the sum of all EMFs equals the original signal. The mathematical model of variational mode decomposition can be expressed as: ; in, The number of layers for the intrinsic mode functions. For the first One eigenmode function For the first The center frequencies of the eigenmode functions For the Dirac function, This represents the convolution operation. The original signal, Indicates time The partial derivatives, j The imaginary unit, st It means that the conditions are met.

[0028] The variational mode decomposition (VMD) solution employs the alternating direction multiplier method, iteratively updating the eigenmode functions, center frequencies, and Lagrange multipliers until the error between two adjacent iterations is less than a preset convergence threshold. During the iteration process, the step size parameter is adaptively adjusted based on the signal characteristics to balance decomposition accuracy and convergence speed. In this embodiment, the original signal... These are the transient recovery voltage waveforms. Residual current waveform of the line The feature extraction circuit first performs variational mode decomposition on the transient recovery voltage waveform to obtain... eigenmode functions The intrinsic mode functions (EMFs) containing power frequency components and those containing high-frequency white noise are filtered out, and the remaining EMFs are the residual EMFs. The residual intrinsic mode functions (IEMs) contain the main transient components of the transient recovery voltage waveform and can accurately reflect the recovery process of the contact gap voltage. Performing a first-order difference operation on the IEMs yields the transient recovery voltage rise rate characteristics. The calculation formula is as follows: ; in, The moment when the circuit breaker contacts separate. This refers to the duration of the transient recovery voltage rise process.

[0029] For the residual current waveform of the line The feature extraction circuit also performs variational mode decomposition to filter out power frequency components and high-frequency white noise, obtaining the residual intrinsic mode functions. Then, the upper envelope of the residual eigenmode functions is extracted using the Hilbert transform. An exponential fit is performed on the envelope to obtain the characteristics of the medium's regenerative strength variation. The exponential fit is solved using the least squares method, and the fitting formula is: ; in, The initial amplitude of the residual current. The decay time constant, This represents the steady-state value of the residual current. Dielectric recovery strength. It is inversely proportional to the decay envelope of the residual current, and its calculation formula is: ; in, This represents the maximum insulation strength of the dielectric medium between the contacts. The decay time constant. It reflects the recovery rate of the medium's recovery strength. The larger the value, the faster the recovery strength of the medium.

[0030] refer to Figure 3 The impedance modeling circuit includes a load characteristic identification register and an impedance calculation logic array. The load characteristic identification register stores the voltage and current phasor trajectories within a predetermined time window before the fault and classifies the load type into rotating motors, constant impedance, and power electronic converters based on the harmonic distortion rate and phase difference of the voltage and current phasor trajectories. The load characteristic identification register uses a ring buffer structure to store voltage and current phasor data, and the size of the buffer can accommodate all phasor data within the predetermined time window before the fault. When the buffer is full, new phasor data overwrites the oldest phasor data, ensuring that the buffer always stores the latest load operating data. When a fault occurs, the load characteristic identification register locks the data in the buffer to prevent new data from overwriting the phasor data before the fault, until the impedance calculation is completed. During normal system operation, the load characteristic identification register collects the voltage phasors of downstream loads at a fixed sampling frequency. With current phasor The acquired phasor data is stored in a register array. When a fault occurs, the load characteristic identification register reads the data from the register array before the fault. Calculate the phase difference between voltage and current phasors based on all voltage and current phasor data within a given time period. Total harmonic distortion of voltage waveform Phase difference The calculation formula is: ; Total Harmonic Distortion The calculation formula is: ; in, This represents the effective value of the fundamental voltage component. For voltage number Effective value of the second harmonic component The highest harmonic order is considered.

[0031] The load characteristic identification register is based on the calculated average phase difference With total harmonic distortion Load type classification: when the average phase difference Greater than the preset inductive phase difference threshold and total harmonic distortion rate When the average phase difference is less than the preset low harmonic threshold, the load type is determined to be a rotating motor; when the average phase difference is less than the preset low harmonic threshold, the load type is determined to be a rotating motor. Approaching zero and total harmonic distortion rate When the total harmonic distortion (THD) is less than the preset low harmonic threshold, the load type is determined to be constant impedance; when the total harmonic distortion (THD) is less than the preset low harmonic threshold, the load type is determined to be constant impedance. When the load exceeds the preset high harmonic threshold, the load type is determined to be power electronic conversion type.

[0032] The impedance calculation logic array matches the corresponding impedance recovery time-varying function according to the load type, substitutes the power loss time into the impedance recovery time-varying function, and adds an ambient temperature correction factor to calculate the expected recovery value of the load impedance at the moment of reconnection. Different types of loads have different forms of impedance recovery time-varying functions: the impedance of constant impedance loads remains basically unchanged after power loss, and its impedance recovery time-varying function is a constant function; the impedance of power electronic conversion loads experiences a brief decrease after power loss and then gradually recovers to its rated value; the impedance of rotating motor loads gradually increases as the rotor speed decreases after power loss, and its impedance recovery time-varying function includes a transient reactance term that decays exponentially with the power loss time. The impedance recovery time-varying function corresponding to rotating motor loads is: ; in, For stator resistance, For stator synchronization reactance, For stator transient reactance, For stator subtransient reactance, For the magnetizing reactance, The time constant is the subtransient time constant. The transient time constant is This represents the duration of power outage.

[0033] Ambient temperature correction factor The formula used to correct for the effect of temperature on load impedance is as follows: ; in, The temperature coefficient of resistance of the load material. The current ambient temperature. This is a reference temperature.

[0034] Expected recovery value of load impedance at the moment of reclosing For the impedance recovery time-varying function at the coincidence time The value multiplied by the ambient temperature correction factor ,Right now: ; The parameters of the impedance recovery time-varying function for different load types are shown in Table 2.

[0035] Table 2. Parameters of Impedance Recovery Time-Varying Function for Different Load Types

[0036] Table 2 lists the impedance recovery time-varying function forms and main parameters for the three main load types. The impedance recovery process of different load types exhibits significantly different characteristics: the impedance of constant impedance loads remains constant after power loss; the impedance of power electronic conversion loads first decreases and then increases after power loss; and the impedance of rotating machine loads gradually increases after power loss. By matching the corresponding impedance recovery time-varying function, the expected impedance recovery value of the load at the moment of reclosing can be accurately calculated, providing a reliable basis for the decision on the closing phase angle.

[0037] refer to Figure 4 The timing decision circuit includes a phase-mapped memory and a delay compensation counter. The phase-mapped memory pre-stores a multidimensional envelope surface containing the dielectric recovery strength and the transient recovery voltage rise rate. The timing decision circuit projects the expected recovery value onto the multidimensional envelope surface to determine the safe closing phase interval and searches for the zero-crossing point of the power supply voltage within the safe closing phase interval as the target phase angle. The multidimensional envelope surface is obtained through extensive experimental data and simulation calculations. The three coordinate axes of the surface represent the dielectric recovery strength. Transient recovery voltage rise rate Phase angle with supply voltage The multidimensional envelope surface divides the entire parameter space into a safe closing region and an unsafe closing region. The phase angle located inside the surface is the safe closing phase, and the phase angle located outside the surface is the unsafe closing phase. The phase mapping memory uses non-volatile memory to store the multidimensional envelope surface data, ensuring that the data is not lost after the system is powered off.

[0038] The timing decision circuit first calculates the dielectric recovery strength. With the rate of rise of transient recovery voltage Substituting the multidimensional envelope surface, we obtain the corresponding safe closing phase interval. Then the expected recovery value. Projecting this onto the safe closing phase interval further narrows the safe closing phase range. A smaller expected recovery value results in a narrower allowable closing phase interval, limiting the closing current; a larger expected recovery value results in a wider allowable closing phase interval. Within the narrowed safe closing phase interval, the timing decision circuit searches for the nearest zero-crossing point of the power supply voltage as the target phase angle. Choosing the zero-crossing point of the power supply voltage as the target phase angle can minimize transient overvoltages and inrush currents during closing operations.

[0039] The delay compensation counter calculates the phase advance compensation amount based on the inherent closing time of the circuit breaker operating mechanism and the control command transmission delay. It then subtracts the delay difference corresponding to the phase advance compensation amount from the target phase angle to generate the actual trigger delay, which is output as the reclosing delay time. (Inherent closing time of the circuit breaker operating mechanism) This refers to the time required from the energization of the closing coil to the contact between the moving and stationary contacts, the control command transmission delay. This refers to the time required from the output of the closing operation signal by the drive circuit to the energization of the closing coil. Total closing delay time. It is the sum of the inherent closing time and the control command transmission delay, i.e.: ; Phase angle offset corresponding to total closing delay time for: ; in, The frequency of the power supply voltage.

[0040] The phase lead compensation amount is the phase angle offset amount. Actual trigger delay The calculation formula is: ; in, This represents the current power supply voltage phase angle. When the calculated actual trigger delay is negative, the timing decision circuit selects the next power supply voltage zero-crossing point as the target phase angle and recalculates the actual trigger delay.

[0041] The execution drive circuit includes a state verification logic gate and a closing coil drive switch. The state verification logic gate acquires the latest measured value and the updated expected recovery value of the dielectric recovery strength in real time just before the reclosing delay expires, and performs a logical AND operation to determine whether the measured value of the dielectric recovery strength is continuously greater than the transient recovery voltage and whether the updated expected recovery value falls within the preset safe impedance range. The two inputs of the state verification logic gate are the outputs of the dielectric recovery strength comparator and the load impedance comparator. The dielectric recovery strength comparator displays the latest measured value of the dielectric recovery strength. With the current transient recovery voltage When comparing, When the expected recovery value is met, the output is high; otherwise, the output is low. The load impedance comparator updates the value with the latest expected recovery value. With respect to the preset safe impedance range When comparing, When the signal is high, the output is high; otherwise, the output is low.

[0042] The status verification logic gate performs a logical AND operation on the outputs of the two comparators. When both comparators output a high level, the logical AND operation outputs a high level, the closing coil drive switch is turned on, and a closing operation signal is output to the circuit breaker operating mechanism. When the logical AND operation outputs a low level, the closing coil drive switch remains off, no closing operation signal is output, and a reclosing lockout state is triggered, preventing further reclosing attempts within a preset lockout time. The closing coil drive switch uses an insulated-gate bipolar transistor (IGBT), which has advantages such as fast switching speed and low on-resistance, and can reliably drive the circuit breaker's closing coil.

[0043] This embodiment details the sensor configuration and synchronous sampling mechanism of the disconnection state monitoring circuit, the variational mode decomposition algorithm and feature calculation method of the feature extraction circuit, the load type identification and impedance recovery time-varying function of the impedance modeling circuit, the multidimensional envelope surface and delay compensation logic of the timing decision circuit, and the state verification and closing drive mechanism of the execution drive circuit. It further refines the technical implementation details of the system and ensures the reliable implementation of the system functions.

[0044] In another preferred embodiment, reference Figure 5 The timing decision circuit also includes an accelerated reclosing judgment comparator. The disconnection status monitoring circuit transmits the decay time constant of the residual current waveform in real time to the accelerated reclosing judgment comparator. When the decay time constant is less than the preset non-inductive load threshold and the transient recovery voltage rise rate characteristic is less than the preset low stress threshold, the accelerated reclosing judgment comparator bypasses the conventional calculation process of the closing phase angle decision function, directly generates a zero-delay closing command, and outputs it to the execution drive circuit. (Worth decay time constant) This reflects the decay rate of the residual current in the line. When the decay time constant is less than the preset non-inductive load threshold, it indicates that the residual current in the line is mainly generated by the non-inductive load, and the dielectric recovery speed is fast. When the transient recovery voltage rise rate characteristic is less than the preset low stress threshold, it indicates that the voltage recovery speed of the contact gap is slow, and the risk of dielectric breakdown is low. In this case, the safety margin of the reclosing operation is high, and zero-delay closing can be used to restore power supply as quickly as possible. The accelerated reclosing judgment comparator is implemented using a hardware comparator, which can complete parameter comparison and command generation in a very short time, ensuring the speed of zero-delay closing.

[0045] Upon receiving a zero-delay closing command, the execution drive circuit immediately initiates the closing preparation process, monitoring the phase of the power supply voltage in real time. It then forcibly executes the closing operation at the first zero-crossing point of the power supply voltage after the fault arc has extinguished. The execution drive circuit contains an arc extinguishing detection unit, which determines whether the fault arc has extinguished by monitoring whether the residual current in the line drops to zero. The arc extinguishing detection unit compares the residual current signal in the line with a preset zero-current threshold. When the residual current in the line is less than the zero-current threshold for multiple consecutive sampling periods, the fault arc is determined to be extinguished. After detecting the extinguishment of the fault arc, the execution drive circuit immediately waits for the next zero-crossing point of the power supply voltage and outputs a closing operation signal to the circuit breaker operating mechanism at the zero-crossing point.

[0046] The feature extraction circuit also includes a mode number adaptive regulator and a polarity checker. The mode number adaptive regulator dynamically calculates the number of intrinsic mode function (IMF) layers in the variational mode decomposition based on the spectral entropy of the transient recovery voltage waveform, and performs decomposition based on the number of IMF layers to eliminate mode aliasing. Spectral entropy is an indicator used to measure the uniformity of a signal's spectral distribution. A larger spectral entropy indicates a more uniform spectral distribution and more frequency components; a smaller spectral entropy indicates a more concentrated spectral distribution and fewer frequency components. The spectral entropy of the transient recovery voltage waveform... The calculation formula is: ; in, The number of frequency points in the spectrum. For the first The proportion of the power spectral density at each frequency point to the total power spectral density.

[0047] The modality number adaptive regulator has a pre-stored table of the correspondence between spectral entropy and the number of intrinsic mode function layers. Based on the calculated spectral entropy of the transient recovery voltage waveform... The optimal number of intrinsic mode function layers is obtained by querying the corresponding relationship table. When the spectral entropy is large, it indicates that the transient recovery voltage waveform contains more frequency components, requiring an increase in the number of intrinsic mode function (IMF) layers to ensure that each IMF has a single center frequency and avoid mode aliasing. When the spectral entropy is small, it indicates that the transient recovery voltage waveform contains fewer frequency components, allowing for a reduction in the number of IMF layers to decrease computational complexity.

[0048] The polarity checker monitors the voltage polarity reversal state of the residual intrinsic mode function at the current zero-crossing point. When the voltage polarity reversal state does not conform to the expected arc-extinguishing characteristics, it determines that secondary reignition exists between the contacts and triggers the disconnection state monitoring circuit to re-execute waveform acquisition and feature extraction operations. During normal arc-extinguishing, when the residual current of the line crosses zero, the fault arc is extinguished, and the voltage polarity of the contact gap will reverse. The polarity checker monitors the voltage polarity of the residual intrinsic mode function at the current zero-crossing point in real time. When it detects that the voltage polarity has not reversed or the reversal direction is not as expected, it determines that secondary reignition exists between the contacts. Secondary reignition will cause the dielectric recovery process to be interrupted, requiring re-acquisition of waveforms and feature extraction to ensure the accuracy of the closing phase angle decision. When the polarity checker determines that secondary reignition exists between the contacts, it immediately sends a re-sampling trigger signal to the disconnection state monitoring circuit. After receiving the re-sampling trigger signal, the disconnection state monitoring circuit restarts the high-speed sample-and-hold circuit and acquires the transient recovery voltage waveform and the residual current waveform after secondary reignition. The feature extraction circuit performs variational mode decomposition and feature extraction operations on the reacquired waveform data to obtain updated transient recovery voltage rise rate characteristics and dielectric recovery strength change characteristics. The timing decision circuit recalculates the target phase angle and reclosing delay time based on the updated feature parameters to ensure the safety of the closing operation.

[0049] The impedance calculation logic array also includes a residual voltage frequency tracker. During power outages, the residual voltage frequency tracker acquires the residual voltage signal at the port of a rotating electric motor-type load in real time, and extracts the decay frequency and initial phase of the residual voltage signal through a phase-locked loop (PLL). After power loss, rotating electric motor-type loads continue to rotate due to the inertia of the rotor, generating an induced voltage, i.e., residual voltage, in the stator windings. The frequency of the residual voltage signal is proportional to the rotor speed; as the rotor speed decreases, the frequency of the residual voltage signal gradually decays. The residual voltage frequency tracker internally incorporates a PLL circuit, which includes a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The phase detector compares the phase of the input residual voltage signal with the reference signal output by the VCO, outputting an error signal proportional to the phase difference. The loop filter filters the error signal, removing high-frequency noise, and outputs a control voltage to the VCO. The VCO adjusts the frequency of the output signal according to the control voltage, ensuring that the frequency and phase of the output signal track the frequency and phase of the input residual voltage signal. Once the phase-locked loop is locked, the frequency and phase of the voltage-controlled oscillator output signal are consistent with the frequency and phase of the residual voltage signal, thereby achieving real-time tracking of the residual voltage frequency and phase.

[0050] The impedance calculation logic array incorporates the decay frequency and initial phase into the impedance recovery time-varying function corresponding to the rotating electrical machine type, correcting the phase angle offset of the transient reactance term. Based on the corrected phase angle offset, it calculates the expected peak value of the backflow current of the rotating electrical machine type load at the moment of reclosing, and adds the expected peak value of the backflow current to the expected recovery value to correct the impedance drop depth. When the circuit breaker recloses, if the residual voltage phase of the rotating electrical machine is inconsistent with the power supply voltage phase, a large backflow current will be generated, causing a momentary drop in load impedance. The corrected impedance recovery time-varying function for the rotating electrical machine type is as follows: ; in, The difference between the residual voltage phase and the power supply voltage phase is calculated using the following formula: ; in, For the power supply voltage at time The phase angle.

[0051] Expected peak reverse current of rotating electrical machine type loads at the moment of overlap The calculation formula is: ; in, This represents the peak value of the power supply voltage. This represents the peak value of the residual voltage signal at the moment of overlap.

[0052] Impedance calculation logic array based on the expected peak value of the reverse current Corrected expected recovery value of load impedance, corrected expected recovery value for: ; in, This is the correction factor for the reverse current. The rated current of the load is given. Table 3 shows the corresponding residual voltage frequency and impedance recovery value for rotating motor loads under different power outage times.

[0053] Table 3. Correspondence between residual voltage frequency and impedance recovery value for rotating electrical loads under different power outage times. Power outage time (s) Residual voltage frequency (Hz) Residual phase (°) Uncorrected impedance recovery value (Ω) Corrected impedance recovery value (Ω) 0.1 48.5 15 2.1 2.3 0.2 45.2 32 2.5 2.9 0.3 40.8 58 3.0 3.7 0.4 35.1 89 3.6 4.6 0.5 28.3 125 4.2 5.5 Table 3 lists the residual voltage frequency, residual voltage phase, and impedance recovery values ​​before and after correction for a certain type of asynchronous motor under different power outage times. As the power outage time increases, the residual voltage frequency gradually decreases, while the difference between the residual voltage phase and the power supply voltage phase gradually increases. The corrected impedance recovery value differs significantly from the uncorrected value. When the power outage time is 0.5s, the corrected impedance recovery value is 31% higher than the uncorrected value. By introducing the residual voltage frequency and phase to correct the time-varying impedance recovery function, the accuracy of calculating the expected impedance recovery value for rotating motor loads can be improved, avoiding excessive closing current caused by backfeeding current.

[0054] This embodiment describes the working logic of the accelerated reclosing judgment comparator and the zero-delay closing mechanism, the spectral entropy calculation and variational mode decomposition layer adjustment method of the mode number adaptive regulator, the secondary reignition judgment process of the polarity checker, and the phase-locked loop implementation of the residual voltage frequency tracker and the impedance correction method for rotating motor type loads. It further optimizes the reclosing performance of the system and improves the system's adaptability to different load types and fault scenarios.

[0055] In yet another preferred embodiment, reference is made to Figure 6 The phase-mapping memory is connected to a surface correction calculator. The surface correction calculator obtains the circuit breaker's cumulative breaking current value and the current ambient temperature value. It calculates a contact wear correction coefficient based on the cumulative breaking current value and a gas medium density correction coefficient based on the current ambient temperature value. The circuit breaker contacts experience wear each time they interrupt a fault current. As the cumulative breaking current value increases, the contact wear gradually increases, leading to a decrease in the dielectric recovery strength of the contact gap. The density of the gas medium is inversely proportional to the ambient temperature; the higher the ambient temperature, the lower the gas medium density and the worse the dielectric insulation strength. The surface correction calculator has an internal non-volatile memory for storing the circuit breaker's cumulative breaking current value. After each circuit breaker completes an interruption operation, the surface correction calculator adds the interrupted current value to the cumulative breaking current value and updates the data in the non-volatile memory.

[0056] Contact wear correction factor The calculation formula is: ; in, This is the contact wear rate coefficient. The cumulative breaking current value of the circuit breaker. This is the rated breaking current of the circuit breaker.

[0057] Gas medium density correction factor The calculation formula is: ; in, For standard reference temperature, This represents the current ambient temperature.

[0058] The surface correction calculator multiplies the contact wear correction factor by the gas medium density correction factor to obtain the overall derating factor. ,Right now: ; The boundary of the multidimensional envelope surface is scaled inward using a comprehensive derating factor. This scaled multidimensional envelope surface replaces the original pre-stored surface as the calculation benchmark for the current safe closing phase interval, thus eliminating the safety margin reduction range caused by contact aging and dielectric degradation. The scaling formula for the multidimensional envelope surface is: ; in, This represents the medium recovery strength value corresponding to the original multidimensional envelope surface. This represents the scaled dielectric recovery strength value. By scaling the multidimensional envelope surface inward, the safe closing phase range can be reduced, improving the safety margin of reclosing operations and compensating for the effects of contact aging and dielectric degradation. The surface correction calculator periodically corrects the multidimensional envelope surface, with the correction cycle set to a preset time interval. During each correction, the surface correction calculator obtains the latest cumulative breaking current value of the circuit breaker and the current ambient temperature value, calculates the comprehensive derating factor, and scales the multidimensional envelope surface. The corrected multidimensional envelope surface is stored in the phase mapping memory, overwriting the original surface data, and serves as the calculation basis for the next closing phase angle decision. Furthermore, after the circuit breaker completes a breaking operation, the surface correction calculator immediately updates the cumulative breaking current value and performs a temporary correction on the multidimensional envelope surface to ensure that the surface data always reflects the current state of the circuit breaker.

[0059] The execution drive circuit also includes a closing process interceptor. During the process of the closing coil driving the switch to conduct and the circuit breaker's moving contact moving towards the stationary contact, the closing process interceptor continuously monitors the rate of change of the transient current in the line and the voltage drop slope of the contact gap. The closing process interceptor is internally equipped with a high-speed current sensor and a high-speed voltage sensor, which respectively collect the transient current signal of the line and the voltage signal of the contact gap. The sampling frequencies of the high-speed current sensor and the high-speed voltage sensor are set to accurately capture the transient changes during the closing process. (Rate of change of transient current in the line) The calculation formula is: ; in, For a moment The line current value, This represents the sampling time interval.

[0060] Contact gap voltage drop slope The calculation formula is: ; in, For a moment The contact gap voltage value.

[0061] When the transient current rate of change exceeds the preset inrush current threshold and the voltage drop slope exceeds the preset abnormal conduction slope, the circuit breaker is determined to be closing due to an unresolved fault. During the closing process, the interceptor immediately generates a forced disconnect pulse. This forced disconnect pulse overrides the closing operation signal and turns off the closing coil drive switch, simultaneously triggering the shunt trip coil to interrupt the closing movement of the moving contact and reverse its direction. When closing due to an unresolved fault, the line experiences a very large short-circuit current, causing a sharp increase in the transient current rate of change, and the voltage across the contact gap drops rapidly to zero. By monitoring these two characteristic parameters, the closing process interceptor can quickly determine that the circuit breaker is closing due to an unresolved fault before the fault current reaches its peak value and immediately execute a forced disconnect operation, preventing the circuit breaker and distribution equipment from being subjected to excessive short-circuit current surges. The response time of the closing process interceptor is set to be less than a preset value to ensure that a forced disconnect pulse is generated and the shunt trip coil is triggered before the short-circuit current reaches its peak value when closing due to an unresolved fault. The tripping time of the shunt trip coil is set to be less than a preset value to ensure that the moving contact of the circuit breaker can complete the disconnection operation before the short-circuit current causes equipment damage.

[0062] The width of the forced tripping pulse is set to a value sufficient to reliably turn off the closing coil drive switch and trigger the shunt trip coil. The forced tripping pulse has a higher priority than the closing operation signal. When the forced tripping pulse is generated, regardless of whether the closing operation signal is valid, the closing coil drive switch will immediately turn off, and the shunt trip coil will immediately actuate, driving the circuit breaker moving contact to move in the opposite direction to complete the tripping operation. The correction coefficients for the circuit breaker's cumulative breaking current and contact wear are shown in Table 4.

[0063] Table 4 Correspondence between Cumulative Breaking Current of Circuit Breaker and Correction Factor for Contact Wear Amount Cumulative breaking current multiple Contact wear correction factor Overall derating factor (25℃) Overall derating factor (40℃) 0 1.00 1.00 0.95 0.2 0.98 0.98 0.93 0.4 0.96 0.96 0.91 0.6 0.94 0.94 0.89 0.8 0.92 0.92 0.87 1.0 0.90 0.90 0.85 Table 4 lists the contact wear correction coefficients for circuit breakers at different cumulative breaking current multiples and the overall derating coefficients at different ambient temperatures. It can be seen that as the cumulative breaking current multiple increases, the contact wear correction coefficient gradually decreases, and the overall derating coefficient also gradually decreases. At the same cumulative breaking current multiple, the higher the ambient temperature, the smaller the overall derating coefficient. When the cumulative breaking current multiple reaches 1.0 and the ambient temperature is 40℃, the overall derating coefficient is 0.85, indicating that the safe closing phase interval needs to be reduced by 15% to ensure the safety of reclosing operations. By using the overall derating coefficient to correct the multidimensional envelope surface, it can be ensured that the circuit breaker maintains sufficient reclosing safety margin during long-term operation.

[0064] This embodiment describes the calculation method of contact wear amount and gas medium density correction coefficient of the surface correction calculator, the scaling correction mechanism of the multidimensional envelope surface, and the transient current and voltage monitoring logic and forced disconnection pulse generation method of the interceptor during the closing process, which further improves the system's operational reliability and fault protection capability under long-term operation.

Claims

1. A smart control box power distribution system supporting automatic reclosing, characterized in that, include: The interruption status monitoring circuit is used to collect the transient recovery voltage waveform and the residual current waveform of the line at the moment when the fault current is interrupted in the power distribution system. A feature extraction circuit is used to extract the transient recovery voltage rise rate feature and the dielectric recovery strength change feature from the transient recovery voltage waveform and the residual current waveform of the line; Impedance modeling circuit is used to establish a dynamic impedance recovery model for the downstream load of the distribution box, and calculate the expected recovery value of the load impedance at the moment of re-coincidence based on the load type identification results and power failure time. The timing decision circuit is used to take the transient recovery voltage rise rate characteristic, the dielectric recovery strength change characteristic and the expected recovery value as inputs, calculate the target phase angle for the circuit breaker moving contact closure through the constructed closing phase angle decision function, and dynamically adjust the reclosing delay time according to the target phase angle. The execution drive circuit is used to output a closing operation signal to the circuit breaker operating mechanism when the reclosing delay time expires, the dielectric recovery strength is greater than the transient recovery voltage, and the load impedance is in the stable range.

2. The intelligent control box power distribution system supporting automatic reclosing according to claim 1, characterized in that: The circuit breaker status monitoring circuit includes a high-frequency broadband voltage sensor and a Rogowski coil current sensor. The high-frequency broadband voltage sensor and the Rogowski coil current sensor are respectively disposed on both sides of the moving and stationary contacts of the circuit breaker and on the outgoing line side, and are connected to the feature extraction circuit through a synchronous clock trigger circuit. After receiving the interruption trigger signal, the feature extraction circuit performs variational mode decomposition on the transient recovery voltage waveform and the residual line current waveform, filters out the power frequency component and high-frequency white noise, obtains the residual intrinsic mode function, and performs differential operation on the residual intrinsic mode function to obtain the transient recovery voltage rise rate feature. At the same time, it performs exponential fitting on the attenuation envelope of the residual line current waveform to obtain the dielectric recovery strength change feature.

3. The intelligent control box power distribution system supporting automatic reclosing according to claim 1, characterized in that: The impedance modeling circuit includes a load characteristic identification register and an impedance calculation logic array. The load characteristic identification register stores the voltage and current phasor trajectories within a predetermined time window before the fault, and classifies the load type into rotating motor type, constant impedance type and power electronic conversion type according to the harmonic distortion rate and phase difference of the voltage and current phasor trajectories. The impedance calculation logic array matches the corresponding impedance recovery time-varying function according to the load type, substitutes the power loss time into the impedance recovery time-varying function, and superimposes the ambient temperature correction coefficient to calculate the expected recovery value of the load impedance at the moment of re-coincidence. The impedance recovery time-varying function corresponding to the rotating motor type includes a transient reactance term that decays exponentially with the power loss time.

4. The intelligent control box power distribution system supporting automatic reclosing according to claim 1, characterized in that: The timing decision circuit includes a phase mapping memory and a delay compensation counter. The phase mapping memory pre-stores a multidimensional envelope surface of the dielectric recovery strength and the transient recovery voltage rise rate. The timing decision circuit projects the expected recovery value onto the multidimensional envelope surface to determine the safe closing phase interval, and searches for the power supply voltage zero crossing point within the safe closing phase interval as the target phase angle. The delay compensation counter calculates the phase advance compensation amount based on the inherent closing time of the circuit breaker operating mechanism and the control command transmission delay. It subtracts the delay difference corresponding to the phase advance compensation amount from the target phase angle to generate the actual trigger delay, and outputs the actual trigger delay as the reclosing delay time.

5. A smart control box power distribution system supporting automatic reclosing according to claim 1, characterized in that: The execution drive circuit includes a state verification logic gate and a closing coil drive switch. The state verification logic gate obtains the latest measured value of dielectric recovery strength and the updated value of expected recovery value in real time before the reclosing delay time expires, and performs a logical AND operation to determine whether the measured value of dielectric recovery strength is continuously greater than the transient recovery voltage and whether the updated value of expected recovery value falls within the preset safe impedance range. When the logical AND operation outputs a high level, the closing coil drives the switching transistor to conduct, and outputs the closing operation signal to the circuit breaker operating mechanism; When the output of the logical AND operation is low, the closing coil drive switch remains off and triggers the reclosing lockout state.

6. A smart control box power distribution system supporting automatic reclosing according to claim 1, characterized in that: The timing decision circuit also includes an accelerated reclosing judgment comparator. The disconnection state monitoring circuit transmits the decay time constant of the residual current waveform of the line to the accelerated reclosing judgment comparator in real time. When the decay time constant is less than the preset non-inductive load threshold and the transient recovery voltage rise rate characteristic is less than the preset low stress threshold, the accelerated reclosing judgment comparator bypasses the conventional calculation process of the closing phase angle decision function, directly generates a zero-delay closing command and outputs it to the execution drive circuit. After receiving the zero-delay closing command, the execution drive circuit forcibly performs the closing operation at the first zero-crossing point of the power supply voltage after the fault arc is extinguished.

7. A smart control box power distribution system supporting automatic reclosing according to claim 2, characterized in that: The feature extraction circuit further includes a mode number adaptive regulator and a polarity checker. The mode number adaptive regulator dynamically calculates the number of intrinsic mode function layers of the variational mode decomposition based on the spectral entropy of the transient recovery voltage waveform, and performs decomposition based on the number of intrinsic mode function layers. The polarity checker monitors the voltage polarity reversal state of the residual intrinsic mode function at the current zero-crossing point. When the voltage polarity reversal state does not meet the expected arc-extinguishing characteristics, it determines that there is a secondary reignition between the contacts and triggers the disconnection state monitoring circuit to re-execute the waveform acquisition and feature extraction operation.

8. A smart control box power distribution system supporting automatic reclosing according to claim 3, characterized in that: The impedance calculation logic array also includes a residual voltage frequency tracker, which collects the residual voltage signal of the rotating motor-type load port in real time during power failure and extracts the attenuation frequency and initial phase of the residual voltage signal through a phase-locked loop. The impedance calculation logic array introduces the attenuation frequency and the initial phase into the impedance recovery time-varying function corresponding to the rotating motor type, corrects the phase angle offset of the transient reactance term, and calculates the expected peak value of the back-feeding current of the rotating motor type load at the moment of overlap based on the corrected phase angle offset. The expected peak value of the back-feeding current is superimposed on the expected recovery value to correct the impedance drop depth.

9. A smart control box power distribution system supporting automatic reclosing according to claim 4, characterized in that: The phase mapping memory is connected to a surface correction calculator. The surface correction calculator obtains the cumulative breaking current value of the circuit breaker and the current ambient temperature value, calculates the contact wear correction coefficient based on the cumulative breaking current value, and calculates the gas medium density correction coefficient based on the current ambient temperature value. The contact wear correction coefficient is multiplied by the gas medium density correction coefficient to obtain the comprehensive derating coefficient. The boundary of the multidimensional envelope surface is shrunk and scaled inward using the comprehensive derating coefficient. The scaled multidimensional envelope surface replaces the original pre-stored surface as the calculation benchmark for the current safe closing phase interval, so as to eliminate the safety margin reduction interval caused by contact aging and medium deterioration.

10. A smart control box power distribution system supporting automatic reclosing according to claim 5, characterized in that: The execution drive circuit also includes a closing process interceptor. During the process of the closing coil driving the switch tube to conduct and the circuit breaker moving contact moving towards the stationary contact, the closing process interceptor continuously monitors the rate of change of the transient current of the line and the slope of the voltage drop between the contacts. When the transient current change rate is greater than the preset inrush current threshold and the voltage drop slope is greater than the preset abnormal conduction slope, it is determined that the circuit breaker is closing without eliminating the fault. The interceptor immediately generates a forced disconnect pulse during the closing process. The forced disconnect pulse covers the closing operation signal and turns off the closing coil drive switch. At the same time, it triggers the shunt trip coil to stop the closing movement of the moving contact and causes it to disconnect in the reverse direction.

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