A method for load distribution control of a cable branch box

Abstract

The application provides a cable branch box load distribution control method, comprising the following steps: obtaining the voltage drop depth of a cut-off circuit and the bus voltage recovery time in the historical switching record of a cable branch box transfer switch, and integrating the circuits to obtain an initial sample set; classifying and grouping each circuit according to the numerical similarity of the voltage drop depth and the bus voltage recovery time in the initial sample set, and determining the load type label of each circuit according to the grouping result; obtaining the bus voltage of each phase and the active power of each circuit in the real-time operation process of the cable branch box, splicing the bus voltage of each phase, the active power of each circuit and the load type label to form a current operation data group; collecting the actual current signal of the cut-off circuit in the falling interval through a current transformer, and carrying out denoising processing on the current signal through a low-pass filter circuit to obtain a residual current falling signal of the cut-off circuit for suppressing the closing inrush current.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a load distribution control method for cable branch boxes. Background Technology

[0002] In the refined management of power distribution networks, cable branch boxes, as key nodes for multi-circuit load distribution and power supply path switching, directly affect the power supply continuity and power quality stability of downstream users. With the continuous improvement of power quality requirements from industrial loads, the switching operation of transfer switches within branch boxes is no longer a simple on / off action, but a complex control process that needs to strike a balance between ensuring continuous load supply and suppressing grid impacts. Currently, most switching control strategies tend to use fixed-duration transition intervals to reduce closing impacts, believing that extending the dwell time in the intermediate disconnect position allows the current in the disconnected circuit to fully recede, thereby reducing the disturbance of the inrush current amplitude to the bus voltage during reclosing. However, this fixed-interval approach ignores the differences in load characteristics of different circuits and fails to consider the tolerance limits of downstream sensitive equipment to power outage duration. When the switching pause exceeds the power outage tolerance limit of certain loads, these devices will enter a power-off restart process, generating a larger inrush current at the moment of power restoration. This turns the pause duration originally designed to suppress impacts into a trigger for secondary current surges. Different types of circuits exhibit varying current recovery rates due to differences in load composition and line parameters. Downstream loads include resistive devices insensitive to momentary power loss, as well as sensitive devices that trigger protection shutdowns after only a few hundred milliseconds of power loss. When the circuit current recovers slowly, premature restoration of power can result in a combined impact of residual and newly generated currents, causing a deep voltage drop on the bus. However, excessively prolonged pauses to allow the current to fully stabilize may exceed the power loss tolerance threshold of sensitive loads, triggering concentrated inrush currents due to the restarting of a batch of equipment. For example, in a circuit switching involving a mixed load of precision machining equipment and variable frequency air conditioners, the machining equipment may only be able to withstand a 200-millisecond power loss, while the circuit current, due to the large proportion of inductive loads, requires 300 milliseconds to recover to a safe level. In this case, choosing any fixed pause duration will inevitably lead to a trade-off between the two. Therefore, in the absence of real-time current change information and load power failure tolerance data, accurately determining the optimal dwell time of the intermediate transition section, so as to avoid the superimposed impact caused by residual current and prevent the load restart cascading inrush current caused by excessive pause, has become the key issue for achieving smooth load switching of the branch box. Summary of the Invention

[0003] This invention provides a load distribution control method for a cable branch box, the method comprising: Obtain the voltage drop depth and bus voltage recovery time of the cut circuit in the historical switching records of the cable branch box changeover switch, and integrate them into an initial sample set by circuit; The circuits were grouped according to the similarity between the voltage drop depth and the bus voltage recovery time in the initial sample set, and the load type label of each circuit was determined based on the grouping results. Obtain the real-time bus phase voltage and active power of each circuit in the cable branch box, and concatenate the bus phase voltage, active power of each circuit with the load type label to form the current operation data group; Obtain the nameplate parameters of the motor load connected to the cut circuit and the mechanical tripping time of the circuit breaker. Combine the current operating data set to determine the duration of the residual induced electromotive force generated by the rotor's inertial rotation after the motor load is de-energized. Determine the current drop range of the cut circuit based on the duration of the residual induced electromotive force. The actual current signal of the cut circuit in the fallback interval is collected by a current transformer, and the actual current signal is processed by a low-pass filter circuit to obtain the residual current fallback signal of the cut circuit. Obtain the power failure tolerance window set by the factory for the sensitive load, compare the overlapping section of the power failure tolerance window and the residual current fall-off signal on the time axis, and extract the overlapping section as a candidate dwell time interval. Extract the common overlapping segment of each candidate dwell time interval, determine the target dwell time based on the dwell time of the common overlapping segment, generate an action execution command for the middle disconnect position of the switch based on the target dwell time, and send the action execution command to the underlying hardware control unit to complete the switching operation.

[0004] Preferably, the step of acquiring the voltage drop depth and bus voltage recovery time of the cut circuit in the historical switching records of the cable branch box transfer switch, and integrating them into an initial sample set by circuit, includes: Obtain the circuit identifier, tripping time stamp, cut circuit voltage sequence, and bus phase voltage sequence from the historical switching record, and merge them according to the circuit identifier and tripping time stamp to obtain historical switching data units; The average voltage of the circuit being cut before the circuit is opened is taken as the reference voltage, and the voltage drop depth is determined by subtracting the lowest voltage after the circuit is opened from the reference voltage. The voltage fluctuation range of each phase of the bus before the circuit breaker is tripped is taken as the corresponding phase recovery interval. The bus voltage recovery time is determined by the time difference between the tripping time and the re-entry of the voltage of each phase of the bus into the corresponding phase recovery interval, thus obtaining the initial sample set.

[0005] Preferably, the step of classifying and grouping each circuit according to the similarity between the initial sample set voltage drop depth and the bus voltage recovery time, and determining the load type label of each circuit based on the grouping results, includes: The voltage drop depth and bus voltage recovery time are extracted according to the loop identifier. The minimum and maximum values ​​of the corresponding data in all loops are converted to a unified scale to obtain the dual characterization values ​​of each loop. The median difference between voltage drop depths between loops and the median difference between bus voltage recovery time are taken as the grouping threshold. Loops whose differences are not greater than the grouping threshold are included in the candidate group, and candidate groups with common loops are merged. The load type label is determined based on the median of the two data points for each circuit group: deep drop slow recovery, deep drop fast recovery, shallow drop slow recovery, or shallow drop fast recovery.

[0006] Preferably, the step of acquiring the real-time bus phase voltage and active power of each circuit in the cable branch box, and splicing the bus phase voltage, active power of each circuit, and the load type label to form a current operating data group includes: Add phase identifiers and sampling timestamps to the voltage of each phase of the busbar, and add circuit identifiers and sampling timestamps to the active power of each circuit to obtain real-time acquisition records; Based on the bus voltage sampling time scale, the active power of each circuit with the smallest time difference is selected within the preset alignment period, and the sampling time scale data of any phase voltage or any circuit active power that is missing is discarded. Read the corresponding load type label according to the circuit identifier, and concatenate them according to the preset order of phase identifier and circuit identifier to obtain the current operating data group.

[0007] Preferably, the step of obtaining the nameplate parameters of the motor load connected to the cut-off circuit and the mechanical tripping time of the circuit breaker, determining the duration of the residual induced electromotive force generated by the rotor's inertial rotation after the motor load is de-energized, and determining the current drop-off range of the cut-off circuit based on the duration of the residual induced electromotive force, includes: Obtain the rated power, rated speed, rated voltage, moment of inertia and mechanical tripping time of each motor in the cut circuit; read the current active power according to the circuit identifier; read the bus voltage according to the phase of the motor; and obtain the circuit load ratio and the operating voltage ratio of each motor. The contact separation time is determined based on the tripping command time and the mechanical tripping time. Based on the rated speed, moment of inertia, circuit load ratio and operating voltage ratio, the time when the residual induced electromotive force is lower than the preset residual voltage threshold is read from the pre-established power failure attenuation correspondence table. The maximum value of the corresponding time for each motor is taken as the duration of the residual induced electromotive force.

[0008] Preferably, the step of acquiring the actual current signal of the cut circuit within the fallback interval through a current transformer, and processing the actual current signal through a low-pass filter circuit to obtain the residual current fallback signal of the cut circuit includes: The current acquisition terminal connected to the secondary side of the current transformer is controlled to read the secondary current of each phase at a fixed sampling period within the current drop-off interval. The current is then converted into the primary current of each phase according to the current transformer ratio. The phase identifier and sampling time stamp are added to obtain the original current sequence. The cutoff frequency of the low-pass filter circuit is set according to the sampling frequency and the rated frequency of the original current sequence. The cutoff frequency is higher than the rated frequency and lower than half of the sampling frequency, and the filtered current sequence is obtained. The absolute value of the denoised current sequence is taken according to the phase identifier, and the maximum value is extracted within the continuous sampling window to obtain the residual current fall-off signal.

[0009] Preferably, the step of obtaining the power failure tolerance window set at the factory for the sensitive load, comparing the overlapping segment of the power failure tolerance window and the residual current fallback signal on the time axis, and extracting the overlapping segment as a candidate dwell time interval includes: Obtain the load identifier, circuit to which it belongs, and power failure withstand time from the factory data of the sensitive load. Match the circuit to be cut according to the circuit to which it belongs. Take the contact separation time as the starting point and the time after the power failure withstand time as the ending point to obtain the power failure withstand window of each sensitive load. Based on the moment when the amplitude envelope of the residual current fall-off signal first falls below the preset residual current threshold and remains below the residual current threshold within a continuous sampling window, the residual current allowable interval is obtained with this moment as the starting point and the end point of the current fall-off interval as the ending point.

[0010] Preferably, the step of extracting the common overlapping segment of each candidate dwell time interval, determining the target dwell time based on the dwell time of the common overlapping segment, generating an action execution command for the intermediate disconnect position of the switch based on the target dwell time, and sending the action execution command to the underlying hardware control unit to complete the switching operation includes: Take the latest start time of each candidate dwell time interval as the common start point and the earliest end time as the common end point. If the common start point is earlier than the common end point, then a common overlapping segment is obtained. The target dwell time is determined by the time difference between the contact separation moment and the common starting point, and the circuit identifier and the target closing position are read to form an action execution command; The underlying hardware control unit keeps the changeover switch in the middle open position from the moment the contacts separate, and drives the changeover switch to enter the target closed position when the target dwell time is reached.

[0011] Preferably, taking the maximum value of the corresponding time for each motor as the duration of the residual induced electromotive force includes: Starting from the moment the contacts separate, and ending at the moment after the duration of the residual induced electromotive force, the current drop-off interval of the cut circuit is determined.

[0012] Preferably, the step of extracting the amplitude envelope from the residual current fall-off signal when it first falls below a preset residual current threshold and remains below the residual current threshold within a continuous sampling window, taking this moment as the starting point and the end point of the current fall-off interval as the ending point, to obtain the residual current allowable interval, includes: Extract the overlapping sections of the power failure tolerance window and the residual current allowable interval on the same time axis, and record the start and end times of the overlapping sections according to the load identifier to obtain the candidate dwell time interval.

[0013] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a load distribution control method for cable branch boxes. Addressing the issue of decreased power supply reliability during switchover due to inrush current and power failure restarts of sensitive loads, the method analyzes historical switching records for voltage dip depth and bus voltage recovery time of the switched circuits. Based on numerical similarity, circuits are categorized and grouped, generating load type labels. These labels are then combined with real-time collected bus phase voltages and active power of each circuit to form the current operating data set, providing load characteristic data for subsequent control decisions. Furthermore, by combining the nameplate parameters of the motors connected to the switched circuits with the circuit breaker's mechanical tripping time, the residual induced current generated by the rotor's inertial rotation is calculated. The duration of the momentum is used to determine the current drop range of the cut-off circuit. The actual current signal within this range is collected by a current transformer and filtered with a low-pass filter to obtain the residual current drop signal that suppresses inrush current. The power failure tolerance window set by the factory for the sensitive load is then compared with the residual current drop signal on the time axis. The common overlapping section of the candidate dwell time interval is extracted to determine the target dwell time. Based on this, the action execution command of the intermediate disconnect position of the transfer switch is generated and sent to the underlying hardware control unit. This achieves precise switching that balances inrush current suppression and uninterrupted operation of sensitive loads, significantly improving the stability of load distribution and power supply continuity in cable branch boxes. Attached Figure Description

[0014] Figure 1 This is a flowchart of a cable branch box load distribution control method according to the present invention.

[0015] Figure 2 This is a schematic diagram of a load distribution control method for a cable branch box according to the present invention.

[0016] Figure 3 This is another schematic diagram of a cable branch box load distribution control method according to the present invention. Detailed Implementation

[0017] To further understand the content of this invention, a detailed description of the invention is provided in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0018] like Figures 1-3 This embodiment of a cable branch box load distribution control method may specifically include: S101. Obtain the voltage drop depth and bus voltage recovery time of the cut circuit in the historical switching record of the cable branch box changeover switch, and integrate them into an initial sample set by circuit.

[0019] Obtain the loop identifier, tripping time stamp, cut-off loop voltage sequence, and bus phase voltage sequence from the historical switching records. Merge these data according to the loop identifier and tripping time stamp to obtain historical switching data units. For each historical switching data unit, take the average voltage of the cut-off loop within a preset sampling period before tripping as the reference voltage. Subtract the lowest voltage after tripping from the reference voltage to determine the voltage drop depth. Take the voltage fluctuation range of each bus phase before tripping as the corresponding phase recovery interval. Determine the bus voltage recovery time by the time difference between the tripping time stamp and the time difference between all bus phase voltages re-entering the corresponding phase recovery interval. Collect these data according to the loop identifier to obtain an initial sample set.

[0020] In one embodiment, a transfer switch controller, a voltage acquisition device, and an event recording device are installed inside the cable branch box. The event recording device records the transfer switch's circuit identifier, the time of the tripping command, the time of mechanical contact disconnection, and the switching status. The voltage acquisition device includes a voltage acquisition terminal for the cut-off circuit located on the load side of the transfer switch, after the cut-off contact, and bus voltage acquisition terminals for each phase of the busbar. The cut-off circuit voltage acquisition terminal continues to acquire the load-side voltage after the transfer switch contacts separate, while the bus voltage acquisition terminals synchronously acquire the voltage of each phase of the busbar. Each acquisition terminal writes a sampling time stamp according to a unified sampling clock, ensuring that the load-side voltage decay process, the busbar voltage change process, and the switching event correspond to each other. For each switching event, the corresponding cut-off circuit voltage sequence is read based on the circuit identifier, and the busbar phase voltage sequence covering the period before and after the tripping is also read. The cut-off circuit voltage sequence includes at least the stable operating section before tripping, the voltage drop section after tripping, and the sampling data before the end of the switching event; the busbar phase voltage sequences cover the same time range and retain the original phase identifier. Furthermore, an event time window is established centered on the tripping time marker. The starting point of the event time window is located in the stable operation section before tripping, and the ending point is located after the voltage of each phase of the busbar has recovered to a stable state. If there are repeated time markers or missing sampling points in the voltage sequence, the recording section that is continuous in time and covers the tripping time marker is retained; if the recording section does not cover the stable operation section before tripping, it is not included in the initial sample set.

[0021] In one possible implementation, the absolute value of the difference between adjacent sampled values ​​within the preset sampling period is first calculated, and the median of all adjacent absolute differences is taken as the benchmark difference. For any sampling point within the sampling period, if the absolute value of the difference between this sampling point and the previous sampling point, as well as the absolute value of the difference between this sampling point and the next sampling point, both exceed a preset abnormal difference threshold, while the absolute value of the difference between the previous sampling point and the next sampling point does not exceed the preset abnormal difference threshold, this sampling point is identified as an isolated abnormal point. The preset abnormal difference threshold is determined based on the measurement error of the voltage acquisition device and the voltage fluctuation during stable operation before the circuit breaker trips, and real voltage changes occurring simultaneously at multiple consecutive sampling points are not excluded as isolated abnormal points. Different switching events use the same preset drop observation period, which is determined based on the voltage sampling period and the initial attenuation process in the historical switching records, to avoid changing the voltage drop depth due to different event time window lengths. For the bus voltage recovery time, the corresponding phase recovery interval is determined based on the bus phase voltage within the preset sampling period before the circuit breaker trips. Take the sliding window standard deviation of all sampled values ​​within the sampling period. The segment whose standard deviation consistently does not exceed 1% of the rated voltage and has at least 5 consecutive sampling points is defined as the stable segment. The minimum value within this stable segment is the lowest stable value, and the maximum value is the highest stable value. These two values ​​serve as the boundaries of the corresponding phase recovery intervals. Let S be the set of sampled values ​​for a certain phase stable segment, then the lowest stable value V... min =min(S), highest stable value V max =max(S). Starting from the tripping time marker, the voltage of each phase of the bus is checked sequentially over time. When the voltage of each phase enters its corresponding recovery interval and remains within that interval for a period of no less than 5 consecutive sampling points, the starting time of that continuous sampling period is determined as the bus voltage recovery time. The time difference between the bus voltage recovery time and the tripping time marker is determined as the bus voltage recovery time of the switching event. Finally, the tripping time marker, voltage drop depth, and bus voltage recovery time corresponding to each switching event are collected according to the loop identifier, and the event time window and phase information are retained to form a historical switching data unit. For multiple historical switching data units of the same loop, they are arranged in chronological order according to the tripping time marker; for different loops, they are stored separately according to the loop identifier to obtain an initial sample set organized by loop.

[0022] S102. Classify and group each circuit according to the similarity between the voltage drop depth and the bus voltage recovery time in the initial sample set, and determine the load type label for each circuit based on the grouping results.

[0023] The initial sample set is obtained, and voltage dip depth and bus voltage recovery time are extracted according to the loop identifier. These values ​​are then converted to a unified scale based on the minimum and maximum values ​​of the corresponding data across all loops. If the maximum and minimum values ​​are the same, the corresponding conversion results are recorded as identical values, resulting in a dual-characteristic value for each loop. Based on these dual-characteristic values, the median difference in voltage dip depth between loops and the median difference in bus voltage recovery time are taken as grouping thresholds. Loops whose differences are not greater than the corresponding grouping thresholds are included in candidate groups, and candidate groups with shared loops are merged. Based on the median of the two data points for each loop group, load type labels are determined as deep dip slow recovery, deep dip fast recovery, shallow dip slow recovery, or shallow dip fast recovery.

[0024] In one implementation, historical switching data units are read from the initial sample set, and voltage dip depths and bus voltage recovery times belonging to the same circuit are aggregated according to the circuit identifier. For cases where multiple historical switching records exist for the same circuit, the median of all voltage dip depths and the median of all bus voltage recovery times for that circuit are taken to form the corresponding circuit's dual original data, preventing a single abnormal switching record from altering the circuit classification results.

[0025] Specifically, for any loop, let the voltage sag depth of the j-th loop be D. j The minimum and maximum voltage drop depths of all circuits are D, respectively. min and D max When D max Not equal to D min At that time, according to d j =(D j -D min ) / (D max -D min Calculate the drop characteristic value of the j-th loop. When D max equals D min At that time, the voltage drop characteristic value of all circuits is uniformly recorded as 0.5, and the voltage drop dimension is marked as having no distinguishing ability. Let the bus voltage recovery time of the j-th circuit be R. j The minimum and maximum recovery times for all circuits are R0 and R1, respectively. min and R max When R max Not equal to R min At that time, according to r j =(R j -R min ) / (R max -R min ) Calculate the recovered characterization value, when R max Equal to R minAt that time, the recovery characterization value of all loops is uniformly recorded as 0.5, and the recovery time dimension is marked as having no distinguishing ability. (From d) j and r j The j-th loop is represented by two bivariate characteristic values. Further, for any two loops, the absolute difference between their voltage drop characteristic values ​​and the absolute difference between their recovery characteristic values ​​are calculated. The absolute differences in voltage drop corresponding to all loop combinations are collected, and the median is taken as the voltage drop grouping threshold; the absolute differences in recovery corresponding to all loop combinations are collected, and the median is taken as the recovery grouping threshold. This forms two comparison boundaries corresponding to the voltage drop degree and the bus recovery speed, respectively.

[0026] In one possible implementation, if the absolute difference in voltage drop between two circuits is not greater than the voltage drop grouping threshold, and the absolute difference in recovery is not greater than the recovery grouping threshold, then the two circuits are grouped into the same candidate group. If only one absolute difference between two circuits satisfies the corresponding grouping threshold, they remain in different candidate groups, ensuring that circuits in the same group have similar values ​​in both voltage drop depth and bus voltage recovery time. For the formed candidate groups, it is checked whether any two candidate groups contain a common circuit. When two candidate groups contain a common circuit, a group to be merged containing all circuits from both candidate groups is first formed, and the absolute difference in voltage drop and absolute difference in recovery between any two circuits in the group to be merged are checked one by one. The two candidate groups are merged only when the absolute difference in voltage drop between any two circuits is not greater than the voltage drop grouping threshold, and the absolute difference in recovery is not greater than the recovery grouping threshold; if any circuit combination does not meet the above conditions, the current merge is not performed. The check is repeated until there are no candidate groups that can be merged further, resulting in a circuit group. For circuits that do not meet the dual grouping conditions with other circuits, a separate circuit group is formed, and their corresponding historical handover response information is not deleted.

[0027] Specifically, the median of all loop drop characteristics and the median of all loop recovery characteristics are calculated and used as the drop type boundary and recovery type boundary, respectively. For each loop group, the median of the drop characteristics and the median of the recovery characteristics of each loop within the group are calculated and used as the drop center value and recovery center value of the loop group, respectively, and compared with the corresponding type boundary.

[0028] For example, when the drop center value is higher than the drop type boundary and the recovery center value is higher than the recovery type boundary, it is determined to be a deep drop slow recovery type; when the drop center value is higher than the corresponding type boundary and the recovery center value is not higher than the corresponding type boundary, it is determined to be a deep drop fast recovery type; when the drop center value is not higher than the corresponding type boundary and the recovery center value is higher than the corresponding type boundary, it is determined to be a shallow drop slow recovery type; the remaining loop groups are determined to be shallow drop fast recovery type, and the corresponding load type label is assigned to each loop in the loop group.

[0029] S103. Obtain the phase voltage of the busbar and the active power of each circuit during the real-time operation of the cable branch box, and splice the phase voltage of the busbar, the active power of each circuit and the load type label to form the current operation data group.

[0030] The system acquires the real-time bus phase voltage and active power of each circuit in the cable branch box. Phase identifiers and sampling timestamps are added to each bus phase voltage, and circuit identifiers and sampling timestamps are added to each circuit active power to obtain a real-time acquisition record. For this real-time acquisition record, using the bus voltage sampling timestamp as a reference, the active power of each circuit with the smallest time difference is selected within a preset alignment period. If any phase voltage or any circuit active power is missing, the data with the corresponding sampling timestamp is discarded. The corresponding load type label is read according to the circuit identifier and concatenated according to a preset order of phase and circuit identifiers to obtain the current operating data set.

[0031] In one embodiment, each phase of the busbar in the cable branch box is equipped with a voltage acquisition terminal, and each outgoing circuit is equipped with a power acquisition terminal. The voltage acquisition terminal records the instantaneous voltage of the corresponding phase and forms the voltage of each phase of the busbar according to the sampling period; the power acquisition terminal synchronously samples the instantaneous voltage and instantaneous current of the same circuit, and calculates the average value of the product of the instantaneous voltage and instantaneous current at each sampling time within a calculation window containing one or more complete power frequency cycles to obtain the active power of the corresponding circuit; the instantaneous power of each phase of the three-phase circuit is calculated separately and then summed, and each active power record retains the circuit identifier, the start and end timestamps of the calculation window, and the power sampling timestamp.

[0032] Specifically, the voltage of each phase of the busbar should include at least a phase identifier, a voltage sample value, and a sampling time stamp; the active power of each circuit should include at least a circuit identifier, a power sample value, and a sampling time stamp. The phase identifier is used to distinguish different phases of the busbar, and the circuit identifier uses the same numbering as the historical switching records, so that the real-time operating data maintains the same circuit correspondence with the assigned load type labels.

[0033] Preferably, each acquisition terminal receives timing information from the same clock source and writes a sampling timestamp during each sampling. For cases where the power acquisition period is longer than the voltage acquisition period, the bus voltage sampling timestamp is used as the alignment reference. The active power record with the smallest time difference is selected from the preset alignment period before and after the bus voltage timestamp to form a real-time acquisition record corresponding to the same operating moment.

[0034] It should be noted that the preset alignment period is determined based on the sampling periods of the voltage and power acquisition terminals, and its time range covers the allowable acquisition deviation between adjacent sampling times. If two active power records with the same time difference exist within the same alignment period, the record with a sampling timescale earlier than the bus voltage sampling timescale is selected, and the same rules are used for each alignment process. Furthermore, for each bus voltage sampling timescale, it is checked whether the real-time acquisition record simultaneously contains the bus voltage of all phases and the active power of all loops in operation. If any bus phase has not generated a voltage sampling value, or any operating loop lacks corresponding active power, the entire set of records under that sampling timescale is discarded, and data from other times is not used to supplement the entire set of records.

[0035] In one possible implementation, the loop operating status is taken from the contact status stored by the transfer switch controller. Loops in the open state are not included in the power integrity check under this sampling timescale, but their loop identifier and open state are retained; loops in the closed state must have active power records. This distinguishes between normal zero-power records and missing acquisition records, avoiding misclassifying open loops as power acquisition anomalies. For real-time acquisition records that pass the integrity check, the corresponding load type tag is read according to each loop identifier. The load type tags include deep drop slow recovery, deep drop fast recovery, shallow drop slow recovery, and shallow drop fast recovery. If multiple tag records exist for the same loop, the valid tag with the latest update time corresponding to the current loop identifier is selected; loops without a matching tag are not included in this splicing record.

[0036] For example, the phase voltages of the bus are arranged according to a pre-established phase identifier order, and the active power of each circuit is arranged according to the circuit identifier order. A corresponding load type label is added after the active power of each circuit. The spliced ​​record retains the reference sampling time scale, phase voltages, active power of each circuit, circuit operating status, and load type label. All fields under the same sampling time scale constitute the current operating data group. The load type label is not only retained as a label field along with the record, but also serves as a routing key when entering the residual induced electromotive force attenuation assessment in S104, used to select the attenuation time constant range and current fallback slope range associated with it.

[0037] Specifically, S104 reads the load response tags determined in S102 for the relatively deep drop-relative slow recovery, relatively deep drop-relative fast recovery, relatively shallow drop-relative slow recovery, or relatively shallow drop-relative fast recovery types according to the circuit identifier, and filters the historical record range that matches the load response tag from the power failure attenuation correspondence table. Based on this, and combining the current active power, operating voltage, and motor nameplate parameters of the cut circuit, it reads the duration required for the residual induced electromotive force to decrease to a preset residual voltage threshold. The contact separation time is recorded as t1, and the duration is recorded as T. r The predicted fallback interval of the cut-off loop is denoted as [t1, t1+T]. r The mechanical tripping time, which is already included in the calculation process for the contact separation moment, will no longer be added separately.

[0038] S104. Obtain the nameplate parameters of the motor load connected to the cut circuit and the mechanical tripping time of the circuit breaker. Combine the current operating data set to determine the duration of the residual induced electromotive force generated by the rotor's inertial rotation after the motor load is de-energized. Determine the current drop range of the cut circuit based on the duration of the residual induced electromotive force.

[0039] Obtain the rated power, rated speed, rated voltage, moment of inertia, and mechanical tripping time of each motor in the cut-off circuit. Read the current active power according to the circuit identifier and the bus voltage according to the phase of each motor to obtain the circuit load ratio and the operating voltage ratio of each motor. Determine the contact separation time based on the tripping command time and the mechanical tripping time. Based on the rated speed, moment of inertia, circuit load ratio, and operating voltage ratio, read the time when the residual induced electromotive force (EMF) is lower than a preset residual voltage threshold from a pre-established power-off attenuation correspondence table. Take the maximum value of the corresponding time for each motor as the duration of the residual induced EMF. Determine the current drop range of the cut-off circuit using the contact separation time as the starting point and the time after the duration of the residual induced EMF as the ending point.

[0040] In one implementation, for the circuit to be switched, the rated power, rated speed, rated voltage, and moment of inertia of each motor in the equipment register are read, and the mechanical tripping time of the corresponding circuit breaker is also read. The moment of inertia is the total inertia of the motor rotor and its mechanical load converted to the motor shaft side.

[0041] Specifically, the active power of the cut-off circuit is read from the current operating data group based on the circuit identifier, and the bus voltage corresponding to the phase of each motor is read. For three-phase motors, the average value of the phase voltages of each bus at the same sampling time is taken as the operating voltage; for single-phase motors, the bus voltage of the phase to which it is connected is taken as the operating voltage. Further, the current active power P of the cut-off circuit is compared with the sum of the rated power Pn of all motors in the circuit, and the ratio k = P / Pn is the circuit load ratio. When the cut-off circuit is also connected to non-motor loads, the measured operating power Pe of the registered non-motor loads is retrieved from the ledger, deducted from the current active power, and then the motor load ratio km is obtained according to km = (P-Pe) / Pn, where P is the current active power of the cut-off circuit, Pe is the sum of the operating power of non-motor loads at the same sampling time, and Pn is the sum of the rated power of all motors in the circuit. Example: When P=85 kW, Pe=10 kW, Pn=100 kW, km=0.75, it is determined that the motor is in an underload operation state, and km is used as the input parameter for subsequent load shedding response characteristic evaluation.

[0042] In one possible implementation, the load proportion of each motor is allocated according to the ratio of its rated power to the total rated power of the circuit, thus obtaining the load share of each motor. If the equipment ledger records independent power acquisition values ​​for each motor, the ratio of independent power to the corresponding rated power is directly used. For the operating voltage of each motor, the ratio of the operating voltage to the corresponding rated voltage is taken as the operating voltage proportion. The operating voltage proportion, load share, rated speed, and moment of inertia are merged according to the motor identification to form a power outage state record. The power outage attenuation correspondence table is compiled from the factory power outage test records or on-site tripping records of motors of the same type and is pre-built during the system configuration phase. This table uses the rated speed range, moment of inertia range, load proportion range, and operating voltage proportion range as a four-dimensional index. Each index item records the duration for which the residual induced electromotive force drops to the residual voltage threshold (5% of the rated voltage) under the corresponding operating condition. This duration is taken from the measured value of the corresponding range in the historical records of motors of the same type. When performing a lookup, the range in which the rated speed, moment of inertia, load share, and operating voltage proportion of each motor are located are determined, and the corresponding index item is read. If the data is located at the boundary of an adjacent interval, the index item with the longer duration is selected; if multiple matching records exist, the larger value is taken as the duration of the motor. Regarding the circuit breaker operating timing, the moment the transfer switch controller issues the tripping command is taken as the tripping command moment, and the mechanical tripping time of the circuit breaker is added to obtain the contact separation calculation moment. If contact status feedback is configured, the feedback moment when the contact status changes from closed to open is used, and the feedback record is verified using the contact separation calculation moment.

[0043] For example, when multiple motors are connected to the cut-off circuit, the duration of the residual induced electromotive force (EMF) of each motor is obtained, and the maximum value is selected as the duration of the residual induced EMF of the cut-off circuit. The circuit duration and the contact separation time use the same time reference. Finally, the contact separation time is used as the starting point of the current fallback interval of the cut-off circuit, and the time after the contact separation time has passed the duration of the residual induced EMF is used as the ending point, forming the current fallback interval of the cut-off circuit corresponding to the current load state and motor inertial characteristics.

[0044] S105. The actual current signal of the cut circuit in the fallback interval is collected by the current transformer, and the current signal is processed by the low-pass filter circuit to obtain the residual current fallback signal of the cut circuit used to suppress the closing inrush current.

[0045] The start and end timestamps of the current fallback interval of the cut-off circuit are obtained. The current acquisition terminal connected to the secondary side of the current transformer is controlled to read the secondary current of each phase within the current fallback interval according to a fixed sampling period. This current is converted into the primary current of each phase based on the current transformer ratio, and phase identifiers and sampling timestamps are added to obtain the original current sequence. The cutoff frequency of the low-pass filter circuit is set according to the sampling frequency of the original current sequence and the rated frequency of the cut-off circuit. This cutoff frequency is higher than the rated frequency but lower than half the sampling frequency. After filtering, a denoised current sequence is obtained. The absolute value of the denoised current sequence is taken according to the phase identifier, and the maximum value is extracted within a continuous sampling window. These values ​​are then arranged according to the sampling timestamps to obtain the residual current fallback signal.

[0046] In one embodiment, current transformers are installed on each phase conductor of the circuit being cut off. The rated primary current of each current transformer covers the normal operating current of the circuit being cut off and the transient current at the moment of tripping. The secondary side is connected to a current acquisition terminal. Each current transformer is configured with a phase identifier, and a fixed correspondence is established between it and the circuit identifier of the circuit being cut off.

[0047] Specifically, the start and end timestamps of the current fallback interval of the cut-off circuit are read. When the sampling clock reaches the start timestamp, the current acquisition terminal begins reading the secondary current of each phase; when the sampling clock reaches the end timestamp, the reading stops. Current sampling values ​​outside the fallback interval are not included in this record. Further, the current acquisition terminal acquires the secondary current of each phase according to a fixed sampling period, and adds a phase identifier and sampling timestamp to each sampling value. The fixed sampling period is less than the rated period of the cut-off circuit, so that each rated period contains multiple sampling points to preserve the gradual decrease in current amplitude after the circuit is opened. For each phase secondary current, the transformation ratio is determined according to the ratio of the primary rated current to the secondary rated current recorded on the nameplate of the corresponding current transformer, and the secondary current sampling value is multiplied by the transformation ratio to obtain the primary current of each phase. The converted primary currents of each phase are arranged according to the sampling timestamp to form the original current sequence.

[0048] In one possible implementation, the low-pass filter circuit is composed of resistors, capacitors, and operational amplifiers. The cutoff frequency of the low-pass filter circuit is set to be higher than the rated frequency of the circuit being cut but lower than half of the sampling frequency, so that current changes near the rated frequency are preserved and high-frequency components formed by circuit breaker contact separation, electromagnetic interference, and coupling of the acquisition line are attenuated.

[0049] It should be noted that the original current sequences of each phase enter their respective low-pass filter channels, and the filter channels use the same cutoff frequency and gain. The preset sampling period traces backward from the start time of the fallback interval, and takes an integer number of cycles of the rated frequency of the cut circuit as the period length. Let the sampling frequency be f. s Given a rated frequency of f0 and a selected number of integer cycles of m, the preset sampling period length is m / f0, and the number of sampling points follows the formula N=round(mf0 / m). s / f0) Determine. When performing zero-point judgment on the original current sequence that has been converted to primary current, the zero-point judgment threshold is set relative to the rated primary current; when performing zero-point judgment on the secondary current sequence that has not yet undergone transformation ratio conversion, the zero-point judgment threshold is set relative to the rated secondary current. The primary and secondary current calibers must not be mixed in the same judgment. After determining the zero-point mean, zero-point correction of I′=IM is performed under the same current caliber. The low-pass filter circuit processes the original current sequence after the above judgment and correction according to the sampling time scale, and outputs the denoised current value corresponding to each sampling time scale to form a denoised current sequence. The filtered record continues to retain the loop identifier and phase identifier, so that the current decrease process of different phases remains independent, and the three-phase currents are not mixed or averaged.

[0050] For example, the absolute value of each phase denoised current sequence is taken point by point, and then the absolute value sequence is divided according to a continuous sampling window. The window length is determined based on the power frequency period and the sampling frequency, and the value ranges from 1 / 4 to 1 / 2 of the power frequency half-cycle. That is, when the sampling frequency is 10kHz and the power frequency is 50Hz, each window contains 25 to 50 sampling points. In this example, 40 sampling points are taken, corresponding to a window duration of 4ms. Adjacent windows are connected end to end and do not overlap. The process is initiated segment by segment from the beginning time of the residual current waveform recording. If the last segment is less than one window length, it is processed according to the actual number of points. The lower limit of the continuous sampling window is the number of sampling points corresponding to one-quarter of the power frequency half-cycle, and the upper limit is the number of sampling points corresponding to one-half of the power frequency half-cycle. When the difference in amplitude envelope values ​​between adjacent windows does not exceed a preset stability threshold, the number of window sampling points is increased within the range not exceeding the upper limit; when the difference in amplitude envelope values ​​exceeds the stability threshold, the number of window sampling points is decreased within the range not lower than the lower limit. When filtering and windowing introduce a fixed time delay, the residual current determination timescale is compensated based on the filter calibration delay and the window end timescale. The current acquisition terminal and the underlying hardware control unit use the same time base counting information to record the sampling timescale; if they cannot directly share a time base, the timescale offset between them is obtained before each switching task begins, and the current sampling timescale is converted to the internal time base of the underlying hardware control unit. If the timescale conversion error exceeds the preset synchronization tolerance, the residual state record for that task is not used to generate the action execution command.

[0051] S106. Obtain the power failure tolerance window set by the factory for the sensitive load, compare the overlapping section of the power failure tolerance window and the residual current fall-off signal on the time axis, and extract the time period that triggers the restart of the sensitive load as the candidate dwell time interval.

[0052] Obtain the load identifier, associated circuit, and power failure withstand duration from the sensitive load's factory data. Match the cut circuit according to the associated circuit, using the contact separation moment as the starting point and the time after the power failure withstand duration as the ending point, to obtain the power failure withstand window for each sensitive load. Based on the residual current drop signal, extract the moment when the amplitude envelope first falls below a preset residual current threshold and remains below the residual current threshold within a preset number of consecutive sampling windows. Using this moment as the starting point and the end point of the current drop interval as the ending point, obtain the residual current allowable interval. Extract the overlapping segment between the power failure withstand window and the residual current allowable interval on the same time axis, and record the start and end times of the overlapping segment according to the load identifier to obtain the candidate dwell time interval.

[0053] In one implementation, the load identifier, circuit, equipment category, and factory power failure tolerance time are read from the load equipment ledger of the disconnected circuit. The power failure tolerance time represents the allowable duration from the start of power outage until the internal controller enters a reset, shutdown, or restart state after the equipment power supply is interrupted, and is provided by the equipment factory test data or controller setting record.

[0054] Specifically, based on a pre-established circuit wiring list, sensitive loads connected to the circuit to be cut are selected according to their respective circuits, and the load identification is verified against the equipment number in the list. The circuit wiring list is entered into the system during the engineering commissioning phase, recording the equipment number, rated voltage level, and wiring method of each circuit, serving as the basic ledger for load identification. In cases where multiple withstand records exist for the same equipment, the record consistent with the current power supply voltage level, controller configuration, and operating mode is read to form the power outage withstand time corresponding to each sensitive load. Further, the contact separation time recorded by the transfer switch controller is used as the power outage starting point for all sensitive loads. For each sensitive load, starting from the contact separation time, the corresponding power outage withstand time is extended sequentially along the time axis, and the extended time is taken as the withstand end point. The power outage start point and the withstand end point constitute the power outage withstand window for that sensitive load.

[0055] It should be noted that if the cut-off circuit connects to multiple sensitive loads, a power failure withstand window should be established for each, and the shortest duration should not be directly used to replace the window of other equipment. Each window retains the load identification, so that precision machining equipment, frequency converter drive equipment, and auxiliary equipment with control power supply can be distinguished according to their respective factory settings. For the residual current fall-off signal, the amplitude envelope value corresponding to the continuous sampling window is read according to the phase identification. The preset residual current threshold is determined one by one as follows: First, read the rated current Ie of the cut-off circuit and the allowable closing residual current Ir of the transfer switch, and take the candidate value Ic=k×Ie, where k is the residual magnetic flux conversion factor, which is generally selected between 0.05 and 0.15. The upper limit is taken for inductive circuits with iron cores, and the lower limit is taken for purely resistive or capacitor-compensated circuits; then compare it with Ir, and the final threshold Ith=min{Ic,0.8×Ir}, that is, it does not exceed 80% of the allowable closing residual current of the transfer switch to avoid critical closing. Taking a transfer switch with a rated current of 630 amps and an allowable residual current of 25% of the rated value as an example, when the inductive circuit has k=0.12, Ic=75.6 amps, 0.8×Ir=126 amps, and Ith=75.6 amps; when the resistive circuit has k=0.06, Ith=37.8 amps. The obtained threshold values ​​are stored in the threshold record table using the circuit identifier as the key, and are called by circuit in the transfer judgment process. Different circuits use their own threshold values, and the same value is not set for all circuits.

[0056] Specifically, starting from the beginning of the current fallback interval, the amplitude envelope values ​​of each phase are sequentially compared with a preset residual current threshold. When the amplitude envelope values ​​of each phase are all lower than the preset residual current threshold and remain below the preset number of sampling windows for a set number of consecutive periods, the end of the last confirmation window is marked as the residual current allowable start point. If the amplitude envelope value of any phase rises above the preset residual current threshold again during the continuous confirmation period, the current continuous confirmation process is canceled, and the counting restarts from the sampling window where the amplitude envelope values ​​of all phases again fall below the threshold. The residual current allowable interval is formed from the residual current allowable start point to the end of the current fallback interval.

[0057] In one possible implementation, if the amplitude envelope value of any phase exceeds a preset residual current threshold again during continuous determination, the current residual current allowable start point is cancelled, and determination is restarted from the sampling window that falls below the threshold again. The end point of the current drop-off interval is taken as the residual current allowable end point, and the residual current allowable start point and the residual current allowable end point constitute the residual current allowable interval. Based on the same time reference, the power failure tolerance window of each sensitive load is compared with the residual current allowable interval. The later start time of the two intervals is taken as the coincidence start point, and the earlier end time of the two intervals is taken as the coincidence end point. When the coincidence start point is earlier than the coincidence end point, the corresponding coincidence segment is recorded.

[0058] For example, when the cut-off circuit connects precision machining equipment and a variable frequency air conditioner, power failure tolerance windows are formed according to the factory settings of the two types of equipment, and then compared with the same residual current allowable range. This yields multiple overlapping sections with corresponding load identifiers, preventing the tolerance boundaries of different equipment from being mixed into a single record. For each overlapping section, the load identifier, the circuit to which it belongs, the overlapping start point, the overlapping end point, and the duration are recorded to obtain a candidate dwell time range. If the power failure tolerance window of a sensitive load does not overlap with the residual current allowable range, a candidate dwell time range corresponding to that load is not formed, and the non-overlapping identifier is retained.

[0059] S107. Extract the common overlapping segment of each candidate dwell time interval, determine the target dwell time based on the dwell time of the common overlapping segment, generate the action execution instruction of the middle disconnect position of the changeover switch based on the target dwell time, and send it to the underlying hardware control unit to complete the switching operation.

[0060] Obtain the start and end timestamps of each candidate dwell time interval, taking the latest start timetamp as the common starting point and the earliest end timetamp as the common ending point. If the common starting point is earlier than the common ending point, a common overlapping segment is obtained; otherwise, no switching instruction is generated. Based on the common overlapping segment, determine the target dwell time using the time difference between the contact separation moment and the common starting point. Read the circuit identifier and target closing position from the pre-stored switching task to generate an action execution instruction containing the target dwell time, circuit identifier, and target closing position. Send the action execution instruction to the underlying hardware control unit. The underlying hardware control unit keeps the transfer switch in the intermediate open position from the contact separation moment, and drives the transfer switch to the target closing position when the target dwell time is reached, completing the switching operation.

[0061] In one implementation, candidate dwell time intervals corresponding to each sensitive load within the cut-off circuit are obtained. Each candidate dwell time interval includes at least a load identifier, the circuit it belongs to, a start time marker, and an end time marker. The start time marker indicates the moment when the residual current enters the allowable range, where the allowable range refers to the residual current I in the circuit. r Satisfy I r ≤I th The state where I th The preset reclosing allowable threshold is typically set to 5% of the rated current. That is, for a rated 100A circuit, I... th Take 5A; when I is detected r Maintaining I for more than 50ms th Within a certain timeframe, record that moment as the starting timescale. The ending timescale indicates the moment when the corresponding sensitive load reaches the power outage tolerance boundary, which is based on the maximum allowable power outage duration T for each sensitive load. max Confirmed, T max The withstand duration parameter is derived from the pre-stored parameters in the load equipment file. For medical loads, the typical value is no more than 0.5 seconds, and for industrial process control loads, the typical value is no more than 2 seconds. The termination time stamp is the start time stamp plus T. max The calculation shows that the termination timescale = the start timescale + T. max The two time scales together determine the time window for the candidate dwell time interval, and the common overlapping segment of each sensitive load is then calculated based on this window.

[0062] Specifically, candidate dwell time intervals corresponding to the current handover task are selected according to the circuit they belong to, and the start and end times of each interval are read one by one. The latest time among all start times is taken as the common starting point, and the earliest time among all end times is taken as the common ending point. The intersection of the intervals is determined by the common starting point and the common ending point. When the common starting point is earlier than the common ending point, the time period between the common starting point and the common ending point is determined as the common overlapping segment. If the common starting point is not earlier than the common ending point, it means that there is no common segment among the candidate dwell time intervals of each sensitive load, and no action execution instruction corresponding to this handover is formed. The circuit identifier and the state of no common segment are recorded. Furthermore, the underlying hardware control unit reads the auxiliary contact feedback signal of the main contact of the changeover switch, and uses the feedback moment when the main contact changes from a closed state to an open state as the contact separation moment t1. If the changeover switch model is not configured with main contact auxiliary contact feedback, the contact separation moment is the sum of the time t0 when the tripping drive command is issued and the mechanical tripping delay td of the changeover switch, i.e., t1 = t0 + td, where td is taken from the changeover switch's factory parameter table, with a typical value of 20ms to 40ms. To avoid errors introduced by cross-device clock drift, the above t0, t1, as well as the common start and common end points, are all sampled and recorded using the same time base counter inside the underlying hardware control unit, with a counting resolution of 1ms. This time base remains consistent regardless of whether the main contact feedback is available, and does not switch to an external clock source.

[0063] In one possible implementation, the common starting point is denoted as t. s Let the common endpoint be t. e Record the moment of contact separation as t1, and read the mechanical closing action duration t corresponding to the target closing position. c The later of the arrival time of the action execution instruction at the underlying hardware control unit and the common starting point is taken as the drive instruction time t. cmd The expected closing time of the target contact is t_m = t cmd +t c When t_m is not later than the common endpoint t e At that time, according to T hold =t cmd -t1 calculates the target dwell time, and the timing duration reaches T from the moment of contact separation. hold The target closing position drive signal is output in real time. If t_m is later than the common endpoint, no action execution command is generated. When the target dwell time is rounded up according to the control unit's timing resolution, the rounded expected contact closing time should be rechecked to ensure it is still within the common overlap section.

[0064] Specifically, the loop identifier, current switch position, and target closing position of the circuit to be switched are read from the pre-stored switching task. The target closing position is the position corresponding to the target power supply path specified by the switching task. The loop identifier, contact separation time, target dwell time, target closing position, and instruction verification identifier are sequentially written into the instruction field to form an action execution instruction. The instruction verification identifier is generated by concatenating the codes of the loop identifier, contact separation time, and target closing position and calculating them using the CRC16 check algorithm. It is used by the underlying hardware side to verify the integrity and legality of the instruction. After the action execution instruction is sent to the underlying hardware control unit, the underlying hardware control unit sequentially checks the loop identifier, current switch position, and instruction verification identifier. If the instruction verification identifier fails to verify, the instruction is discarded and an exception is reported, and subsequent actions are not executed. When all checks pass and the current switch position is in the middle open position, the timer starts from the contact separation time. When the timer reaches the target dwell time, an action signal is output to the drive coil corresponding to the target closing position, and the drive output corresponding to the original power supply position is stopped.

[0065] For example, after the underlying hardware control unit drives the changeover switch into the target closed position, it reads the target position contact feedback. If the target position contact feedback indicates that the changeover switch has entered the target closed position, the switching completion time stamp is recorded; if no target position contact feedback is read within the preset action feedback period, the drive output is stopped and the intermediate open position is maintained, and the state of incomplete switching is recorded.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A load distribution control method for a cable branch box, characterized in that, The method includes: Obtain the voltage drop depth and bus voltage recovery time of the cut circuit in the historical switching records of the cable branch box changeover switch, and integrate them into an initial sample set by circuit; The circuits were grouped according to the similarity between the voltage drop depth and the bus voltage recovery time in the initial sample set, and the load type label of each circuit was determined based on the grouping results. Obtain the real-time bus phase voltage and active power of each circuit in the cable branch box, and concatenate the bus phase voltage, active power of each circuit with the load type label to form the current operation data group; Obtain the nameplate parameters of the motor load connected to the cut circuit and the mechanical tripping time of the circuit breaker. Combine the current operating data set to determine the duration of the residual induced electromotive force generated by the rotor's inertial rotation after the motor load is de-energized. Determine the current drop range of the cut circuit based on the duration of the residual induced electromotive force. The actual current signal of the cut circuit in the fallback interval is collected by a current transformer, and the actual current signal is processed by a low-pass filter circuit to obtain the residual current fallback signal of the cut circuit. Obtain the power failure tolerance window set by the factory for the sensitive load, compare the overlapping section of the power failure tolerance window and the residual current fall-off signal on the time axis, and extract the overlapping section as a candidate dwell time interval. Extract the common overlapping segment of each candidate dwell time interval, determine the target dwell time based on the dwell time of the common overlapping segment, generate an action execution command for the middle disconnect position of the switch based on the target dwell time, and send the action execution command to the underlying hardware control unit to complete the switching operation.

2. The cable branch box load distribution control method according to claim 1, characterized in that, The voltage drop depth and bus voltage recovery time of the cut circuits in the historical switching records of the cable branch box transfer switch are obtained and integrated into an initial sample set by circuit, including: Obtain the circuit identifier, tripping time stamp, cut circuit voltage sequence, and bus phase voltage sequence from the historical switching record, and merge them according to the circuit identifier and tripping time stamp to obtain historical switching data units; The average voltage of the circuit being cut before the circuit is opened is taken as the reference voltage, and the voltage drop depth is determined by subtracting the lowest voltage after the circuit is opened from the reference voltage. The voltage fluctuation range of each phase of the bus before the circuit breaker is tripped is taken as the corresponding phase recovery interval. The bus voltage recovery time is determined by the time difference between the tripping time and the re-entry of the voltage of each phase of the bus into the corresponding phase recovery interval, thus obtaining the initial sample set.

3. The cable branch box load distribution control method according to claim 1, characterized in that, The circuits are grouped according to the similarity between the initial sample set voltage drop depth and the bus voltage recovery time. Based on the grouping results, the load type label for each circuit is determined, including: The voltage drop depth and bus voltage recovery time are extracted according to the loop identifier. The minimum and maximum values ​​of the corresponding data in all loops are converted to a unified scale to obtain the dual characterization values ​​of each loop. The median difference between voltage drop depths between loops and the median difference between bus voltage recovery time are taken as the grouping threshold. Loops whose differences are not greater than the grouping threshold are included in the candidate group, and candidate groups with common loops are merged. The load type label is determined based on the median of the two data points for each circuit group: deep drop slow recovery, deep drop fast recovery, shallow drop slow recovery, or shallow drop fast recovery.

4. The cable branch box load distribution control method according to claim 1, characterized in that, The process involves acquiring the real-time bus phase voltage and active power of each circuit in the cable branch box, concatenating the bus phase voltage and active power with the load type label to form a current operating data group, including: Add phase identifiers and sampling timestamps to the voltage of each phase of the busbar, and add circuit identifiers and sampling timestamps to the active power of each circuit to obtain real-time acquisition records; Based on the bus voltage sampling time scale, the active power of each circuit with the smallest time difference is selected within the preset alignment period, and the sampling time scale data of any phase voltage or any circuit active power that is missing is discarded. Read the corresponding load type label according to the circuit identifier, and concatenate them according to the preset order of phase identifier and circuit identifier to obtain the current operating data group.

5. The cable branch box load distribution control method according to claim 1, characterized in that, The process of acquiring the nameplate parameters of the motor load connected to the cut-off circuit and the mechanical tripping time of the circuit breaker, combined with the current operating data set, to determine the duration of the residual induced electromotive force generated by the rotor's inertial rotation after the motor load is de-energized, and determining the current drop-off range of the cut-off circuit based on the duration of the residual induced electromotive force, includes: Obtain the rated power, rated speed, rated voltage, moment of inertia and mechanical tripping time of each motor in the cut circuit; read the current active power according to the circuit identifier; read the bus voltage according to the phase of the motor; and obtain the circuit load ratio and the operating voltage ratio of each motor. The contact separation time is determined based on the tripping command time and the mechanical tripping time. Based on the rated speed, moment of inertia, circuit load ratio and operating voltage ratio, the time when the residual induced electromotive force is lower than the preset residual voltage threshold is read from the pre-established power failure attenuation correspondence table. The maximum value of the corresponding time for each motor is taken as the duration of the residual induced electromotive force.

6. The cable branch box load distribution control method according to claim 1, characterized in that, The process of acquiring the actual current signal of the cut circuit within the fallback interval through a current transformer, and then denoising the actual current signal through a low-pass filter circuit to obtain the residual current fallback signal of the cut circuit includes: The current acquisition terminal connected to the secondary side of the current transformer is controlled to read the secondary current of each phase at a fixed sampling period within the current drop-off interval. The current is then converted into the primary current of each phase according to the current transformer ratio. The phase identifier and sampling time stamp are added to obtain the original current sequence. The cutoff frequency of the low-pass filter circuit is set according to the sampling frequency and the rated frequency of the original current sequence. The cutoff frequency is higher than the rated frequency and lower than half of the sampling frequency, and the filtered current sequence is obtained. The absolute value of the denoised current sequence is taken according to the phase identifier, and the maximum value is extracted within the continuous sampling window to obtain the residual current fall-off signal.

7. The cable branch box load distribution control method according to claim 1, characterized in that, The process involves obtaining the factory-set power failure tolerance window for the sensitive load, comparing the overlapping sections of the power failure tolerance window and the residual current fallback signal on the time axis, and extracting the overlapping sections as candidate dwell time intervals, including: Obtain the load identifier, circuit to which it belongs, and power failure withstand time from the factory data of the sensitive load. Match the circuit to be cut according to the circuit to which it belongs. Take the contact separation time as the starting point and the time after the power failure withstand time as the ending point to obtain the power failure withstand window of each sensitive load. Based on the moment when the amplitude envelope of the residual current fall-off signal first falls below the preset residual current threshold and remains below the residual current threshold within a continuous sampling window, the residual current allowable interval is obtained with this moment as the starting point and the end point of the current fall-off interval as the ending point.

8. The cable branch box load distribution control method according to claim 1, characterized in that, The process of extracting the common overlapping segments of each candidate dwell time interval, determining the target dwell time based on the dwell time of the common overlapping segments, generating an action execution command for the middle disconnect position of the switch based on the target dwell time, and sending the action execution command to the underlying hardware control unit to complete the switching operation includes: Take the latest start time of each candidate dwell time interval as the common start point and the earliest end time as the common end point. If the common start point is earlier than the common end point, then a common overlapping segment is obtained. The target dwell time is determined by the time difference between the contact separation moment and the common starting point, and the circuit identifier and the target closing position are read to form an action execution command; The underlying hardware control unit keeps the changeover switch in the middle open position from the moment the contacts separate, and drives the changeover switch to enter the target closed position when the target dwell time is reached.

9. The load distribution control method for cable branch boxes according to claim 5, characterized in that, The step of taking the maximum value of each motor's corresponding time as the duration of the residual induced electromotive force includes: Starting from the moment the contacts separate, and ending at the moment after the duration of the residual induced electromotive force, the current drop-off interval of the cut circuit is determined.

10. The cable branch box load distribution control method according to claim 7, characterized in that, The moment when the amplitude envelope extracted from the residual current fall-off signal first falls below a preset residual current threshold and remains below the residual current threshold within a continuous sampling window, the residual current allowable interval is obtained, starting from this moment and ending at the end of the current fall-off interval, including: Extract the overlapping sections of the power failure tolerance window and the residual current allowable interval on the same time axis, and record the start and end times of the overlapping sections according to the load identifier to obtain the candidate dwell time interval.

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