Digital current detection and protection method and rail transit direct current switch cabinet system

Abstract

The invention relates to the technical field of power system fault detection, in particular to a digital current detection and protection method and a rail transit direct current switch cabinet system, and the method comprises the steps: synchronously collecting a current signal, and calculating a current instantaneous value and a unit time variation in real time; when the current instantaneous value exceeds the amplitude reference value and the unit time variation exceeds the change rate reference value at the same time, generating a local fault marking signal; sending a local fault marking signal to an adjacent detection node based on a dual-channel GOOSE communication network, and receiving a feedback current state signal; performing locking logic operation on the local fault marking signal and the current state signal to generate a fault position identifier; and continuously monitoring the state of the main channel of the dual-channel GOOSE communication network, and when the main channel is continuously lost, switching to the standby channel to transmit data. According to the invention, the core problems of fault positioning deviation and protection action lag caused by communication link breakage, transmission delay and fault diffusion of the rail transit DC power supply system are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of power system fault detection technology, and in particular to a digital current detection and protection method and a DC switchgear system for rail transit. Background Technology

[0002] As the core protection unit of the traction power supply network, the DC switchgear system for rail transit plays a crucial role in rapid fault isolation and ensuring power supply continuity. Its technological foundation relies on the collaborative control among distributed current detection nodes. Each node generates a fault marker by collecting line current signals and transmits the signal to adjacent nodes via a high-speed communication network. Finally, a blocking logic algorithm determines the faulty section.

[0003] However, existing technologies suffer from three significant drawbacks. Firstly, regarding communication reliability, traditional GOOSE networks employ a fixed-period retransmission mechanism. While low-frequency retransmission reduces bandwidth load during the steady-state phase of switching quantities, it fails to detect link breaks in real time, leading to the loss of fault change signals when transmission paths become abnormal. Secondly, regarding fault location accuracy, multi-node signal transmission experiences delay fluctuations due to path differences, and existing interlocking logic lacks dynamic delay compensation capabilities, causing timestamp comparisons between local and adjacent node signals to fail, resulting in misjudgments of fault sections. Thirdly, regarding protection response mechanisms, fixed protection zone settings cannot adapt to the diffusion characteristics of fault currents. When the fault point is located at the zone boundary or cascading propagation occurs, delayed protection actions will lead to an expansion of the fault range. These drawbacks collectively cause the system to face risks of inaccurate location, protection delays, and cascading trips, severely restricting the safety and reliability of rail transit power supply.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a digital current detection and protection method and a DC switchgear system for rail transit, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A digital current detection method, the method comprising: Multiple detection nodes are deployed on the power line. The detection nodes synchronously collect current signals and calculate the instantaneous value of the current and the change per unit time in real time. When the detection node simultaneously satisfies the conditions that the instantaneous current value exceeds the amplitude reference value and the change per unit time exceeds the change rate reference value, a local fault marker signal with precise time recording is generated, wherein the amplitude reference value is based on the rated current and the change rate reference value is based on the maximum allowable current change rate. Based on the dual-channel GOOSE communication network, the local fault marker signal of the current detection node is sent to the adjacent detection node, and the current status signal with time record is received from the adjacent detection node according to the dual-channel GOOSE communication network. A latching logic operation is performed on the local fault marker signal and the current status signal. When the instantaneous current value in the current status signal is lower than the latching ratio value of the amplitude reference value and the time record difference between the local fault marker signal and the current status signal is within the transmission delay tolerance, a fault location identifier is generated. The status of the main channel of the dual-channel GOOSE communication network is continuously monitored. When the main channel loses a set number of message retransmission cycles in a row, the data is switched to the backup channel. The message retransmission cycle includes a steady-state retransmission cycle and a change-state retransmission cycle.

[0007] Furthermore, the setting of the amplitude reference value, the rate of change reference value, and the lockout ratio value includes: The amplitude reference value is dynamically adjusted based on the real-time monitoring value of the rated current, so that the amplitude reference value is maintained as a fixed proportion of the rated current. The maximum allowable rate of change of current is determined based on the load type of the power line, and the reference value of the rate of change is set as a fixed proportion of the maximum allowable rate of change of current. During the execution of the latching logic operation, the latching ratio value is updated synchronously according to the current adjustment value of the amplitude reference value; When comparing the time record difference between the local fault marker signal and the current state signal, the time window constraint mechanism in the latching logic operation is used to verify the compliance of the transmission delay tolerance.

[0008] Further, after generating the fault location identifier, the process includes: The system sends a verification request signal, including the location coordinates, to the adjacent detection node based on the fault location identifier, and receives a verification response from the adjacent detection node based on the current state signal. When the instantaneous current value in the verification response conflicts with the judgment result of the latching logic operation, the latching logic operation is retried and the value of the transmission delay tolerance is updated. Based on the current channel status of the dual-channel GOOSE communication network, the main channel or the backup channel is selected, and the time record of the finally confirmed fault location identifier and the associated local fault marker signal is sent to the central monitoring server. The central monitoring server generates a positioning log including the location coordinates, the time record, and the locking ratio value, and synchronously updates the set reference value of the amplitude reference value.

[0009] Furthermore, when switching to the backup channel for data transmission, the following steps are included: Generate a channel switching record that includes the activation time of the backup channel and the number of consecutive losses of the primary channel, and append the channel switching record to the header of the data packet of the local fault marker signal subsequently transmitted through the backup channel; When the backup channel transmits the current status signal, the compensation coefficient of the transmission delay tolerance is adjusted according to the channel switching record in the header of the data packet; During the execution of the latching logic operation, the time record difference between the local fault marker signal and the current state signal is recalculated based on the compensation coefficient of the adjusted transmission delay tolerance; If the backup channel continues to transmit for a stable period, a channel status recovery request carrying the channel switching record is sent to the central monitoring server, and the status monitoring of the main channel is resumed after receiving the switching confirmation instruction issued by the central monitoring server.

[0010] Further, determining the message retransmission period after a set number of consecutive lost messages on the main channel includes: The status of the main channel of the dual-channel GOOSE communication network is monitored in real time. When a change in the switch quantity is detected, the current message retransmission cycle is interrupted and the change message is immediately retransmitted with the first short cycle. In a steady state without any change in the switching quantity, the message is retransmitted with a second long period, wherein the second long period is longer than the first short period; If multiple messages of the second long period are lost consecutively, the main channel is determined to be disconnected and a channel fault identifier is generated.

[0011] A digital current protection method, the method comprising: The corresponding protection area is determined based on the fault location identifier. The protection area includes the power line section indicated by the fault location identifier and the associated section within an adjacent preset distance. Send a protection action request to the circuit breaker control node within the protection area. The protection action request carries the fault location identifier and the corresponding time record. The circuit breaker control node receives the action response signal fed back. When the instantaneous current value in the action response signal continuously exceeds the amplitude reference value for a preset duration, a protection execution command is generated. The circuit breaker control node is triggered to perform a line disconnection operation according to the protection execution command, and at the same time, the interlocking protection warning including the fault location identifier is sent to the adjacent protection area according to the dual-channel GOOSE communication network. After the line disconnection operation is performed, the current status signal of the protection area is reacquired. When the current status signal indicates that the fault current has not been eliminated, the protection area is iteratively expanded and the protection action request is retried.

[0012] Further, iteratively expanding the protected area and re-triggering the protection action request includes: When iteratively expanding the protection area, a fault propagation trend analysis result is generated based on the reacquired current state signal and the fault location identifier. The fault propagation trend analysis result is used to quantify the propagation direction and speed of the fault in the power line section. Based on the fault propagation trend analysis results, the coverage of the associated section is adjusted, and an updated protection action request is sent to the circuit breaker control node within the adjusted associated section. After receiving the updated action response signal from the circuit breaker control node, the effectiveness of the protection execution command is verified in conjunction with the interlocking protection early warning. When the instantaneous current value in the updated action response signal still exceeds the amplitude reference value, a protection upgrade command is generated. Based on the protection upgrade command, the dual-channel GOOSE communication network is triggered to send a protection status anomaly report to the central monitoring server and receive protection strategy optimization parameters issued by the central monitoring server. The protection strategy optimization parameters are applied to redetermine the protection area range, and the sending and verification process of the protection action request is iteratively executed until the current status signal indicates that the fault current has been eliminated.

[0013] Furthermore, the results of the fault propagation trend analysis include: The instantaneous current value sequence of the current state signal at at least three detection nodes within the associated section is obtained, and the gradient of the rate of change of current between adjacent nodes is calculated. Based on the consistency of direction and the difference in amplitude of the current change rate gradient, the propagation direction of the fault along the power line section is determined; The fault propagation speed is calculated based on the time difference of current change and physical distance between two consecutive detection nodes in the propagation direction; The product vector of the propagation direction and the fault propagation speed is defined as the result of the fault propagation trend analysis.

[0014] Furthermore, protection execution instructions are generated, including: The waveform distortion rate of the instantaneous current value in the action response signal is verified. When the waveform distortion rate exceeds the preset distortion threshold and continues to reach the preset duration, a first-level protection execution command is generated. According to the first-level protection execution command, the circuit breaker control node is triggered to perform a primary line disconnection operation, and at the same time, the interlocking protection warning, including the primary action intensity, is sent to the adjacent protection area based on the dual-channel GOOSE communication network. After the primary line disconnection operation is performed, if the reacquired current status signal indicates that the fault current has not been eliminated, harmonic component analysis is performed on the action response signal. When the proportion of a specific harmonic amplitude exceeding the amplitude reference value continues to increase, a second-level protection execution command is generated based on the protection upgrade command. Based on the second-level protection execution command, the circuit breaker control node is triggered to perform a complete line disconnection operation, and the action intensity level of the interlocking protection warning and the urgency level of the fault location identifier are updated.

[0015] A DC switchgear system for rail transit, characterized in that the system comprises: The distributed detection module is deployed at each node of the power line to collect current signals in real time and generate fault marker signals with precise timestamps. The dual-channel communication management module transmits the fault marking signal according to the primary and backup redundant GOOSE network and executes a dynamic retransmission cycle mechanism to monitor the channel health status. The fault location decision module performs interlocking logic operations on the fault marking signals of the local node and adjacent nodes to generate the fault location identifier of the power line. The channel switching control module automatically switches between primary and backup transmission paths based on the channel health status and adjusts the delay compensation parameters during switching. The protection execution linkage module triggers the circuit breaker's graded protection action based on the fault location identifier and sends a cascading protection warning to the area where the adjacent node is located. The central monitoring and analysis module receives and stores fault location data, and dynamically optimizes protection strategy parameters and channel management thresholds.

[0016] The technical solution of this invention can achieve the following technical effects: By eliminating transmission delay errors through a multi-node dynamic time window collaborative detection mechanism, and preventing signal loss by combining a dual-channel hot-switching communication protection system, and dynamically expanding the protection area based on fault propagation prediction, the core problems of signal loss, positioning deviation caused by transmission delay, and protection lag caused by fault propagation in the DC power supply system of rail transit are fundamentally solved. This achieves millisecond-level accurate positioning of fault sections and effective suppression of cascading tripping risks, thereby improving the safety and reliability of the power supply system.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a digital current detection method. Figure 2 This is a schematic diagram of the response process after generating the fault location identifier; Figure 3 This is a flowchart illustrating a digital current protection method. Figure 4 A flowchart illustrating the process of re-triggering a protection action request. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Example 1; like Figure 1As shown, this application provides a digital current detection method, the method comprising: Multiple detection nodes are deployed on the power line. The detection nodes synchronously collect current signals and calculate the instantaneous value of the current and the change per unit time in real time. When the detection node simultaneously meets the conditions that the instantaneous current value exceeds the amplitude reference value and the change per unit time exceeds the change rate reference value, a local fault marker signal with precise time recording is generated, wherein the amplitude reference value is based on the rated current and the change rate reference value is based on the maximum allowable current change rate. Based on the dual-channel GOOSE communication network, the local fault marking signal of the current detection node is sent to the adjacent detection nodes, and the current status signal with time record is received from the adjacent detection nodes according to the dual-channel GOOSE communication network. A blocking logic operation is performed on the local fault marker signal and the current status signal. When the instantaneous current value in the current status signal is lower than the blocking ratio value of the amplitude reference value and the time record difference between the local fault marker signal and the current status signal is within the transmission delay tolerance, a fault location identifier is generated. The status of the main channel of the dual-channel GOOSE communication network is continuously monitored. When the main channel loses a set number of message retransmission cycles in a row, the data is switched to the backup channel. The message retransmission cycle includes the steady-state retransmission cycle and the change retransmission cycle.

[0023] Specifically, to ensure the overall performance and reliability of current detection, the deployed detection nodes will be distributed across key nodes of the power line according to a predetermined topology. Each detection node should be equipped with a high-precision current sensor and an embedded signal processing module, enabling it to synchronously acquire current signals and calculate instantaneous current values ​​and changes per unit time in real time. In the optimized design, the amplitude reference value is set with the system's rated current as a reference, such as a rated current of 100A, while the rate of change reference value is set based on the maximum allowable current change rate, such as a change rate of 10A / ms. Specifically, if the instantaneous current value of a detection node exceeds the set amplitude reference of 100A, and the rate of change per unit time is greater than 10A / ms, a local fault marker signal containing precise time records will be generated. The local fault signal will be transmitted to adjacent detection nodes through a constructed dual-channel GOOSE communication network. To ensure communication stability and data real-time performance, the dual-channel system adopts an Ethernet protocol configuration, with the main channel undertaking the normal transmission of current status signals. In practical implementation, if the main channel loses packets within a specified continuous message retransmission period, such as 3 shifts and 5 steady-state cycles, it will automatically switch to the backup channel to avoid data loss. Simultaneously, adjacent detection nodes receive and analyze the fault marker signal and the time-recorded current status signal from the current node. In the fault identification mechanism, the blocking logic is designed as follows: when the received instantaneous current value from the adjacent node is lower than the amplitude reference value, the blocking ratio is set to 80% of 100A (i.e., 80A), and the time difference between the local fault marker signal and the current status signal is within a preset transmission delay, such as 100ms, a fault location identifier is generated. If the fault marker signal of node A is timed at 12:10:01.50, and the current status signal fed back by node B shows a current value below 80A at 12:10:01.55, then through logical operations, the fault location is determined to be near node A. In addition, the detection node should have monitoring capabilities to continuously track the operating status of the dual-channel GOOSE network. To ensure seamless communication switching and stable data transmission, if any packet loss exceeds a certain number of times, the backup channel will intervene in the transmission to ensure the timely delivery of the current fault signal. In the preferred embodiment, the backup channel, similar to the main channel, needs to have high fault tolerance and a good data transmission mechanism.

[0024] The technical solution of this invention effectively solves the core problems of fault location deviation and protection action lag caused by communication disconnection, transmission delay and fault propagation in the DC power supply system of rail transit.

[0025] Furthermore, the setting of the amplitude reference value, the rate of change reference value, and the lockout ratio value includes: The amplitude reference value is dynamically adjusted based on the real-time monitoring value of the rated current to keep the amplitude reference value a fixed proportion of the rated current. The maximum allowable rate of change of current is determined based on the load type of the power line, and the benchmark value of the rate of change is set as a fixed proportion of the maximum allowable rate of change of current. During the execution of the latching logic operation, the latching ratio value is updated synchronously based on the current adjustment value of the amplitude reference value; When comparing the time difference between the local fault marker signal and the current status signal, the time window constraint mechanism in the latching logic operation is used to verify the compliance of the transmission delay tolerance.

[0026] As a preferred embodiment of the above, firstly, regarding the setting of the amplitude reference value, the detection node integrates a real-time monitoring function of the rated current. Each detection node continuously adjusts the amplitude reference value by evaluating the current operating status of the power system and dynamically analyzing the monitoring data, so that it can be maintained as a fixed proportion of the rated current. For example, in a power system, the rated current is determined by the operating environment or equipment power. Assuming the rated current is 100A, the amplitude reference value can be initially set to 90% of the rated current, i.e., 90A. When certain external conditions, such as a sudden increase in ambient temperature or grid load, cause the rated current to gradually rise to 110A, The system automatically and dynamically adjusts the amplitude reference value to 99A through real-time monitoring, maintaining it at a fixed percentage of 90% of the rated current. This setting mode avoids misjudgments caused by changes in operating conditions due to static reference values, and improves the adaptability and accuracy of the detection method. Secondly, for the setting of the rate of change reference value, the maximum allowable current change rate is determined based on the load type of the power line, and the reference value is set as a fixed percentage of this rate of change. For example, for motor loads, since the starting current usually has a high instantaneous peak value, the maximum allowable current change rate can be set to 20A / ms, and the rate of change reference value is selected as... 80% of this is 16A / ms. However, for electronic loads, the current change is relatively slow, and the maximum allowable current change rate can be set to 5A / ms. The reference value for the change rate is chosen to be its fixed proportion value of 4A / ms. By setting the reference value for the change rate according to different load types, the adaptability of the current detection method to diverse load scenarios is enhanced. Furthermore, the latching logic operation requires ratio calculation centered on the amplitude reference value. Therefore, a synchronous update mechanism is designed, that is, when the amplitude reference value is dynamically adjusted, the latching proportion value can be adjusted in real time. For example, if the amplitude reference value changes from the initial 90A to 99A, the set latching... When the latching ratio is 80% of the amplitude reference value, the latching ratio will automatically adjust to 80% of 79.2A (i.e., 99A). This real-time update function ensures that the latching ratio always matches the current operating conditions, avoiding inaccurate fault identification due to static values. Furthermore, during the latching logic operation, a time-window-constrained delay verification mechanism is constructed for the time record difference to verify the compliance of the transmission delay tolerance. To implement this mechanism, each detection node is equipped with a high-precision time synchronization device to ensure high consistency between the generated fault marker signal and the received current state signal. For example, if the fault marker signal time record of node A is 12:10:01.50 and the current state signal time record of node B is 12:10:01.55, the time difference between the two will be detected as 50ms based on the set time window constraint, such as 100ms, to determine if it is within the transmission delay tolerance range, thus verifying that the recorded time difference meets the requirements. If the time difference exceeds the preset tolerance, a signal abnormality or communication abnormality is automatically determined, and the corresponding abnormality handling mechanism is activated.

[0027] Furthermore, such as Figure 2 As shown, after generating the fault location identifier, it includes: Based on the fault location identifier, a verification request signal including the location coordinates is sent to the adjacent detection nodes, and a verification response based on the current state signal is received from the adjacent detection nodes. When the instantaneous current value in the verification response conflicts with the judgment result of the latching logic operation, the latching logic operation is retried and the value of the transmission delay tolerance is updated. Based on the current channel status of the dual-channel GOOSE communication network, the primary or backup channel is selected, and the time record of the finally confirmed fault location identifier and the associated local fault marker signal is sent to the central monitoring server. The central monitoring server generates a positioning log that includes location coordinates, time records, and locking ratio values, and synchronously updates the set reference value of the amplitude reference value.

[0028] As a preferred embodiment of the above, after the fault location identifier is generated, to ensure the accuracy of fault location, the current detection node sends a verification request signal to adjacent detection nodes based on the identifier information. The verification request signal includes the fault location coordinate information, and the signal is generated along with the current node's time record and related parameters, such as the blocking ratio value. Specifically, for example, when a fault location identifier is determined to be "a fault has occurred at node A", node A will send a verification request signal to adjacent nodes B and C, along with the coordinates of node A. The adjacent nodes receiving the verification request need to verify based on their own real-time current status signal and fault context, and generate a verification response signal to return to the original initiating node, thereby completing bidirectional confirmation. When the verification response conflicts with the original determination result, for example, if the instantaneous current value detected by the adjacent node is lower than the fluctuation amplitude determined by the blocking logic, or the time record difference is not within the acceptable transmission delay range, the fault location is re-verified by re-triggering the blocking logic operation and adjusting the value of the transmission delay tolerance. In specific implementation, the range of transmission delay can be dynamically expanded or shortened according to the field conditions. To ensure the accuracy of the verification process, for example, the default transmission delay tolerance is set to 100ms. However, when network load increases and communication performance deteriorates, the delay tolerance can be adjusted to 150ms to cope with transmission delay. After triggering the interlocking logic operation, if the recalculation verifies that the fault location identifier is consistent with the feedback response, the fault location determination is considered valid; otherwise, it will continue to wait for more feedback information or conduct a series of in-depth operational status analyses to finally complete the fault location. After the fault location identifier is verified, based on the current channel status of the dual-channel GOOSE communication network, the main channel or the backup channel is selected for data transmission. If the main channel is found to be operating well and the data transmission is stable, the verified fault location identifier, the local fault marker signal time record containing the fault location coordinates, and other relevant parameters, such as the adjusted amplitude reference value and the interlocking ratio value, are sent to the central monitoring server through the main channel first. If an anomaly is detected in the main channel, such as the number of consecutive packet losses exceeding the set upper limit or the communication quality index deteriorating, the system automatically switches to the backup channel and completes the data transmission to ensure the real-time performance and reliability of data transmission.After the data reaches the central monitoring server, the server creates a location log based on the received fault location identifier and stores detailed information. The location log includes: the coordinates of the fault location, the time record of the fault trigger, the amplitude reference value, and the blocking ratio value. This information can be archived according to time sequence and spatial location for subsequent querying and fault tracing. Simultaneously, the central monitoring server also synchronously updates the amplitude reference value setting based on the location log content. If there is a significant deviation between the central server's calculation result and the current detection node's reference value, the server will send the new setting reference value to all relevant detection nodes to complete parameter synchronization. For example, if the server detects that the rated current has increased from 100A to 120A due to a sudden increase in system load, the amplitude reference value setting will be updated to 108A by a fixed ratio of 90%, and all detection nodes will be notified to implement dynamic adjustments.

[0029] Furthermore, when switching to the backup channel for data transmission, the following includes: Generate a channel switching record that includes the activation time of the backup channel and the number of consecutive losses of the primary channel, and append the channel switching record to the header of the data packet of the local fault marker signal subsequently transmitted through the backup channel; When the backup channel transmits the current status signal, the compensation coefficient for the transmission delay tolerance is adjusted according to the channel switching record in the data packet header. During the execution of the latching logic operation, the time record difference between the local fault marker signal and the current status signal is recalculated based on the compensation coefficient of the adjusted transmission delay tolerance. If the backup channel continues to transmit for a stable period, a channel status recovery request carrying the channel switching record is sent to the central monitoring server, and the status monitoring of the main channel is resumed after receiving the switching confirmation instruction issued by the central monitoring server.

[0030] As a preferred embodiment of the above, when the number of consecutive data losses in the main channel reaches a set threshold, such as 3-5 times, the backup channel is immediately activated to transmit data. Simultaneously with activating the backup channel, a channel switching record is generated. This record includes key information such as the activation time of the backup channel and the number of consecutive data losses in the main channel. By appending this information to the header of the data packets transmitted by the backup channel, it is carried in each local fault marker signal, thus providing support for subsequent data processing. Specifically, for example, if instability in the main channel is detected at 12:11:00, the backup channel is activated at this time, and the generated channel switching record is appended to the header of the fault signal data packet. The channel switching record in the data packet header is not only used for historical transmission but also serves as an important basis for adjusting the transmission delay tolerance when the backup channel transmits current status signals. Based on this record, the associated compensation coefficient is updated in real time. Specifically, if the overall network latency of the backup channel is higher than that of the main channel, the transmission delay tolerance compensation coefficient will be adjusted by historical records for each channel switch. For example, ... If an overall delay increase of 20ms is detected during backup channel testing, the default transmission delay tolerance can be adjusted to 120ms based on the transmission delay tolerance compensation coefficient to ensure data timeliness. When performing interlocking logic operations, the time record difference between the local fault marker signal and the current status signal is recalculated based on these adjusted transmission delay tolerances and compensation coefficients to ensure more accurate timeliness analysis, especially in situations where real-time signal detection requirements are high. In addition, after the backup channel has stabilized for a certain period, such as 12 hours without interruption of data transmission within the error range, a channel status recovery request carrying the channel switching record is sent to the central monitoring server to notify the current channel status and stability. Upon receiving the request, the central monitoring server can analyze the possibility of channel recovery and issue a switching confirmation command. Upon receiving the command, the detection node will resume monitoring the status of the main channel and re-establish the maintenance priority of the main channel. This method ensures stable transmission of the backup channel and also provides a dynamic management method for the reset and optimization of the main channel.

[0031] Furthermore, determining the retransmission period for a set number of consecutively lost messages on the main channel includes: Real-time monitoring of the main channel status of the dual-channel GOOSE communication network; when a change in switch quantity is detected, interrupt the current message retransmission cycle and immediately retransmit the change message with the first short cycle. In a steady state without any change in the switching quantity, the message is retransmitted with the second longer period, which is longer than the first shorter period; If multiple second-long-cycle messages are lost consecutively, the main channel is determined to be disconnected and a channel fault identifier is generated.

[0032] As a preferred embodiment of the above embodiments, in order to monitor the main channel status of the dual-channel GOOSE communication network in real time, a communication status monitoring module is integrated into the detection node. This module continuously tracks the communication parameters of the main channel, including message transmission frequency, reception integrity, and the triggering status of change events. During the detection process, when the switch status of the main channel changes, to ensure the rapid transmission of change event-related messages to the target node, the current steady-state message retransmission cycle is automatically interrupted, and the change message is retransmitted with a first short cycle. For example, in a specific scenario, when a switch action occurs, the retransmission cycle is immediately adjusted from the originally set steady-state retransmission interval of 200ms to a change retransmission interval of 20ms. To quickly transmit change information messages, this short-cycle retransmission mechanism ensures that important state transition information reaches the target node in the shortest possible time, improving location and fault handling efficiency. When detecting a steady-state condition without switch-signal changes, to avoid excessive communication resource consumption and meet the requirements of long-term continuous monitoring, a second long cycle is used to retransmit steady-state messages. Compared to the first short cycle, the second long cycle allows for a larger message transmission interval, thereby reducing the load on the communication link. For example, the steady-state retransmission cycle can be set to the range of 200ms to 500ms. This longer time interval maintains the information transmission of the current detection state while reducing network resource occupancy. If the network load is low, it can... A longer cycle is chosen to optimize network performance. In the fault determination mechanism of the main channel, if multiple consecutive loss of second-long-cycle packets is detected on the main channel (e.g., three consecutive losses), the main channel is determined to be disconnected and a channel fault identifier is generated. Specifically, once three consecutive loss of packet cycles on the main channel is detected, not only will the backup channel be activated, but a channel fault identifier will also be generated. For example, if three long-cycle packet losses are detected at 12:15:00, the main channel communication link is determined to be faulty, and a main channel disconnection identifier is generated. The time of the fault is also recorded. This fault identifier can be used for subsequent fault tracing and network performance analysis. Based on the channel switching mechanism, in the main channel... After a channel fault identifier is generated, the backup channel will be automatically activated in the next transmission cycle. At the same time, the stability of the backup channel will be monitored. During the implementation process, the backup channel maintains the same message retransmission mechanism and cycle adjustment logic as the main channel to ensure that normal communication can be maintained when the backup channel is running. If the backup channel is running stably, for example, if no data loss occurs after at least dozens of steady-state long cycles, a channel status recovery request will be sent to the central monitoring server. This request includes the record content and timestamp of the main channel fault. The sending time and message content of this recovery request can be dynamically adjusted according to the network conditions, but it is usually performed after the backup channel has been running stably to ensure the reliability of the fault recovery operation.After receiving a recovery request, the central monitoring server will conduct a comprehensive network analysis and assessment. Once it confirms that the main channel has returned to normal, it will issue a switchover confirmation command. Upon receiving the command, it will resume real-time monitoring of the main channel's status while simultaneously keeping the backup channel in a ready-to-start state to handle potential future communication failures.

[0033] Example 2; like Figure 3 As shown, this application provides a digital current protection method, the method comprising: The corresponding protection area is determined based on the fault location identifier. The protection area includes the power line section indicated by the fault location identifier and the associated section within the adjacent preset distance. Send a protection action request to the circuit breaker control node within the protection area. The protection action request carries the fault location identifier and the corresponding time record. Receive the action response signal fed back by the circuit breaker control node. When the instantaneous current value in the action response signal continuously exceeds the amplitude reference value for a preset duration, generate a protection execution command. The circuit breaker control node is triggered to perform line disconnection operation according to the protection execution command, and at the same time, the interlocking protection warning including the fault location identifier is sent to the adjacent protection area according to the dual-channel GOOSE communication network. After the line disconnection operation is performed, the current status signal of the protection area is reacquired. When the current status signal indicates that the fault current has not been eliminated, the protection area is iteratively expanded and the protection action request is retried.

[0034] Specifically, during power line operation, after a fault location marker is generated, the protection zone is first determined based on the fault location marker. Specifically, the protection zone includes the power line segment indicated by the fault marker and related segments within a preset distance. For example, if the fault location marker indicates that the fault occurred in power line segment A, which is 200m long, the protection zone can be extended to segment A and its adjacent segments B and C within a 500m radius. The delineation of the protection zone not only considers the direct impact of the fault location but also fully assesses the potential range of the fault current to ensure that the protection action covers a sufficient area to avoid secondary faults. After delineating the protection zone, the protection is then extended to the outages within the protection zone. The circuit breaker control node sends a protection action request, which carries the current fault location identifier, relevant time records, and the command priority of the protection action. For example, if the fault location is section A, the protection action request will indicate the geographical coordinates of section A and the time record of the fault occurrence, such as "location coordinates 150m, fault identification time 12:15:21.10", and mark the priority as "high" to ensure that the circuit breaker control node can respond to the request quickly. After receiving the protection action request, the circuit breaker control node will send back an action response signal, which includes the instantaneous current value of the current power line. For example, if the circuit breaker detection node finds that the instantaneous current value of the fault section continuously reaches 120A and exceeds the amplitude reference value, the response signal will be sent. For example, if the fault reaches a preset duration of 10ms (e.g., 100A), a protection execution command is generated to trigger the protection action. This step uses continuous monitoring and time constraints to determine whether the fault has met the triggering conditions for the protection action, effectively avoiding false trips caused by short-term fluctuations. After generating the protection execution command, the circuit breaker control node is triggered to perform a line disconnection operation, cutting off the power supply to the faulty section to isolate the fault current. Simultaneously, based on the dual-channel GOOSE communication network, an interlocking protection warning, including the fault location identifier, is sent to adjacent protection areas. The function of the interlocking protection warning is to notify adjacent sections that they may be affected by the fault expansion and prompt them to enter the protection preparation state. For example, when the line in section A is disconnected, the warning is sent through the communication network. In real time, protection warning signals are transmitted to sections B and C, including fault location identification and time records. After receiving the cascading warning, the detection nodes of adjacent sections can activate the active monitoring mechanism to prevent the fault from escalating. After the circuit breaker completes the line disconnection operation, the current status signal of the protected area is reacquired to further evaluate the effectiveness of the protection action. When the reacquired current status signal still indicates that the fault current has not been eliminated, the protection area is iteratively expanded and the protection action request is retried. For example, if the initial protection area is section A and adjacent sections B and C, and the reacquired signal finds that section D may be affected, the protection area is expanded to section D, and a protection action request is sent to the circuit breaker in section D to achieve further fault control.

[0035] Furthermore, such as Figure 4 As shown, iteratively expanding the protection area and re-triggering the protection action request includes: When iteratively expanding the protection area, fault propagation trend analysis results are generated based on the reacquired current state signal and fault location identifier. The fault propagation trend analysis results are used to quantify the direction and speed of fault propagation in the power line section. Based on the fault propagation trend analysis results, the coverage of the associated sections is adjusted, and updated protection action requests are sent to the circuit breaker control nodes in the adjusted associated sections. After receiving the updated action response signal from the circuit breaker control node, the effectiveness of the protection execution command is verified by combining the interlocking protection early warning. When the instantaneous current value in the updated action response signal still exceeds the amplitude reference value, a protection upgrade command is generated. Based on the protection upgrade command, the dual-channel GOOSE communication network is triggered to send a protection status anomaly report to the central monitoring server and receive protection strategy optimization parameters issued by the central monitoring server. The protection strategy is applied to optimize parameters to redefine the protection area range, and the process of sending and verifying protection action requests is iteratively executed until the current status signal indicates that the fault current has been eliminated.

[0036] As a preferred embodiment of the above, after the fault location marker is generated, and after the protection action is executed and the line disconnection operation is completed, the real-time current status signal within the protection area is acquired to evaluate the fault handling effect. If the real-time signal still shows that the fault current has not been eliminated, the iterative process of expanding the protection area is entered. During the iteration process, fault propagation trend analysis is performed based on the reacquired current status signal and fault location marker. The fault propagation trend analysis includes quantifying the direction and speed of fault propagation on the power line section, and the analysis results are fed back to the protection system. For example, if the fault location marker is initially located in section A, and the propagation trend analysis finds that the fault current is propagating downstream to section B at a speed of 100m per second, then the analysis yields the fault propagation trend. The main direction of the fault propagation is from section A to section B, and the distance and range that the fault coverage may reach to section C are calculated. Based on the fault propagation trend analysis results, the protection area is dynamically adjusted and iteratively expanded. Specifically, according to the direction and speed of fault propagation, the coverage of the associated sections is expanded from section A to the merged section between sections A, B, and C. At the same time, updated protection action requests are sent to the circuit breaker control nodes within the adjusted associated sections. The updated request content includes the new protection section range, the expanded fault location identifier, and the latest time record of the fault occurrence. For example, when the expanded protection range includes sections B and C, the sent protection request will explicitly indicate that the circuit breaker action request nodes are sections B and C. The control terminal of C provides updated coverage information to ensure rapid response. After receiving the updated action response signal from the circuit breaker control node, to verify the effectiveness of the protection execution command, the reliability of the response signal is further analyzed by combining it with the interlocking protection early warning. If the instantaneous current value in the response signal still exceeds the current amplitude reference value (e.g., the reference value is 100A, the response signal current value shows 120A), and the fault propagation trend analysis still indicates that the power system may suffer further extended faults, then the protection upgrade mechanism is entered, and a protection upgrade command is automatically generated. The generation of this command signifies that the protection action is upgraded from conventional fault protection to enhanced protection status to handle complex and propagating faults. Based on the protection upgrade command, the dual-channel GO... The OSE communication network sends a protection status anomaly report to the central monitoring server. This report details the current dynamic status of the protection area, including key information such as fault location identification, protection area expansion range, current status signals, and protection execution status. After receiving the report, the central monitoring server will conduct a comprehensive analysis of the overall power grid status and issue optimized protection strategy parameters. These parameters include rules for expanding protection strategies, settings for further shrinking or expanding the protection area, and other updated fault handling priorities. For example, if the central monitoring server detects abnormal current trends in multiple adjacent sections D and E, its optimized parameters may suggest further expanding the protection area to sections D and E to cover the potential diffusion area.The protection strategy optimization parameters issued by the central monitoring server are used to redefine the protection area range and iteratively execute the sending and verification process of protection action requests. Each iteration is based on the real-time current status signal and the optimized protection area range to ensure that the fault source can be gradually controlled to a state of elimination. Finally, when the current status signal indicates that the fault current has been completely eliminated, the iterative expansion process ends. At the same time, log information of the entire protection process is recorded, including the initial location of the fault, the expanded protection range, the response status of each node, and the protection strategy adjustment record, for subsequent query and performance analysis.

[0037] Furthermore, the results of the fault propagation trend analysis include: Acquire the instantaneous current value sequence of at least three detection nodes in the associated section of the current state signal, and calculate the current change rate gradient between adjacent nodes; Based on the consistency of direction and the difference in amplitude of the current rate of change gradient, the propagation direction of the fault along the power line section is determined; The fault propagation speed is calculated based on the time difference of current change and physical distance between two consecutive detection nodes in the propagation direction; The product vector of the propagation direction and the fault propagation speed is defined as the result of the fault propagation trend analysis.

[0038] As a preferred embodiment of the above, firstly, in the associated section of the power line, it is necessary to obtain the instantaneous current value sequence of at least three detection nodes. Each detection node records the instantaneous current value in real time. These data constitute the time series of the current state signal. To achieve better fault dynamic analysis, three or more detection nodes are selected in the area where the fault is most likely to spread, ensuring that these nodes can fully cover different sections of the line. Next, the fault propagation direction is determined by calculating the current change rate gradient between adjacent nodes. The change rate gradient refers to the comparison of the current change rate between two adjacent nodes, which can quantitatively analyze the slope direction and magnitude of current increase or decrease. The consistency of the gradient, that is, the consistency of multiple gradient directions, usually points to a potential fault propagation path. For example, if the gradient from section A to section B is positive and the magnitude increases, and the gradient from section B to C is also positive and the magnitude is even greater, then it can be determined that the fault may propagate along the direction from A to C. The consistency of gradient direction and the difference in magnitude provide reliable data support for determining the direction. After determining the initial propagation direction, the calculation of the fault propagation speed becomes a key step, requiring analysis of the connections in the propagation direction. The fault propagation trend analysis uses the time difference of current changes between two detection nodes and their corresponding physical distance. The time difference of current changes represents the time interval of signal propagation, while the physical distance is the actual distance between the nodes. By combining the two, the propagation speed of the fault in that section can be calculated. For example, assuming the physical distance between nodes B and C is 200 meters, and the time difference of current change between nodes B and C is recorded as 0.5 seconds, the calculated propagation speed is 400 meters per second. In this way, the propagation speed of the fault in actual operation can be determined to optimize the protection response. Finally, the fault propagation trend analysis defines the product vector of the fault propagation direction and propagation speed as the core indicator of the result, namely the so-called fault propagation vector. This vector not only indicates the specific path and rate of the fault in the power grid, but also provides an important reference for subsequent protection area expansion and interlocking control. Through the practical application of the vector, the protection section can be adjusted in real time and a precise and rapid response can be made. In specific applications, the fault propagation trend analysis is combined with a graphical interface to display the fault location, propagation direction, and speed in the control center, providing intuitive data information for operators' decision-making and execution.

[0039] Furthermore, generating protection execution instructions includes: The waveform distortion rate of the instantaneous current value in the action response signal is verified. When the waveform distortion rate exceeds the preset distortion threshold and continues to reach the preset duration, the first-level protection execution command is generated. According to the first-level protection execution command, the circuit breaker control node is triggered to perform the primary line disconnection operation, and at the same time, based on the dual-channel GOOSE communication network, the interlocking protection warning including the primary action intensity is sent to the adjacent protection area. After the primary line disconnection operation is performed, if the reacquired current status signal indicates that the fault current has not been eliminated, harmonic component analysis is performed on the action response signal. When the proportion of a specific harmonic amplitude exceeding the amplitude reference value continues to increase, a second-level protection execution command is generated based on the protection upgrade command. Based on the second-level protection execution command, the circuit breaker control node is triggered to perform a complete line disconnection operation, and the action intensity level of the interlocking protection warning and the urgency level of the fault location indicator are updated.

[0040] As a preferred embodiment of the above, the generation of protection execution commands aims to achieve precise control of the fault impact range. First, the received action response signal is subjected to waveform distortion rate verification. When the current signal is distorted, its waveform distortion rate characterizes the degree of signal deviation. A distortion threshold is set to define the limit range of waveform tolerance. If the current waveform distortion rate of a certain node exceeds the preset distortion threshold, and this state persists for a preset duration, a first-level protection execution command is generated to activate primary protection measures. For example, in a power distribution line, if the waveform distortion rate exceeds the set threshold by 10% and remains there for 30ms, the first-level command is triggered. The first-level protection execution command aims for rapid response by triggering the primary line disconnection operation of the circuit breaker control node, reducing the possibility of cascading reactions. When executing primary protection, a cascading protection warning signal is sent to adjacent protection areas through a dual-channel GOOSE communication network. This signal includes a description of the primary action strength. For example, if node A executes a primary disconnection operation, it simultaneously notifies adjacent nodes B and C. The warning signal will clearly state that "the primary disconnection operation has been executed, and the operation is a low-intensity protection." "Protective measures, and preparations to upgrade the monitoring level within the area"; After the primary line disconnection is completed, the current status signal needs to be reacquired to determine whether the fault current has been eliminated. If the signal indicates that the fault current is still maintained or increasing, further fault depth analysis is required. On this basis, harmonic component analysis is carried out on the action response signal, focusing on checking the continuous growth trend of the amplitude of a specific harmonic. When it is detected that the amplitude of a specific harmonic continuously exceeds a certain proportion of the amplitude reference value and shows an increasing trend, it proves that the fault has the potential to expand. The second-level protection execution command can then be generated based on the protection upgrade strategy. For example, if the third harmonic component is found to increase by more than 20% and dynamically increase, this phenomenon will trigger the second-level command. The role of the second-level protection execution command is to execute a deeper and more comprehensive protection response. By triggering the circuit breaker control node to perform a complete line disconnection operation, it ensures the complete isolation of the fault section and effectively prevents the further propagation of the fault. At the same time, the action intensity level of the interlocking protection warning signal is updated, for example, upgraded to "high" and the urgency status of the relevant fault location identifier is modified to "urgent" so that other related areas can enter a high alert state in advance.

[0041] Example 3; Based on the same inventive concept as the digital current detection and protection method in the foregoing embodiments, the present invention also provides a DC switchgear system for rail transit, the system comprising: The distributed detection module is deployed at each node of the power line to collect current signals in real time and generate fault marker signals with precise timestamps. The dual-channel communication management module, based on the GOOSE network transmission fault marking signal with primary and backup redundancy, executes a dynamic retransmission cycle mechanism to monitor the channel health status. The fault location decision module performs interlocking logic operations on the fault marking signals of the local node and adjacent nodes to generate fault location identifiers for the power line. The channel switching control module automatically switches between primary and backup transmission paths based on the channel health status and adjusts the delay compensation parameters during switching. The protection execution linkage module triggers the circuit breaker's graded protection actions based on the fault location identifier and sends interlocking protection warnings to the areas where adjacent nodes are located. The central monitoring and analysis module receives and stores fault location data, and dynamically optimizes protection strategy parameters and channel management thresholds.

[0042] The adjustment system described above in this invention can effectively realize a digital current detection and protection method, and the technical effects it can achieve are as described in the above embodiments, which will not be repeated here.

[0043] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A digital current detection method, characterized in that, The method includes: Multiple detection nodes are deployed on the power line. The detection nodes synchronously collect current signals and calculate the instantaneous value of the current and the change per unit time in real time. When the detection node simultaneously satisfies the conditions that the instantaneous current value exceeds the amplitude reference value and the change per unit time exceeds the change rate reference value, a local fault marker signal with precise time recording is generated, wherein the amplitude reference value is based on the rated current and the change rate reference value is based on the maximum allowable current change rate. Based on the dual-channel GOOSE communication network, the local fault marker signal of the current detection node is sent to the adjacent detection node, and the current status signal with time record is received from the adjacent detection node according to the dual-channel GOOSE communication network. A latching logic operation is performed on the local fault marker signal and the current status signal. When the instantaneous current value in the current status signal is lower than the latching ratio value of the amplitude reference value and the time record difference between the local fault marker signal and the current status signal is within the transmission delay tolerance, a fault location identifier is generated. The status of the main channel of the dual-channel GOOSE communication network is continuously monitored. When the main channel loses a set number of message retransmission cycles in a row, the data is switched to the backup channel. The message retransmission cycle includes a steady-state retransmission cycle and a change-state retransmission cycle.

2. The digital current detection method according to claim 1, characterized in that, The setting of the amplitude reference value, the rate of change reference value, and the lockout ratio value includes: The amplitude reference value is dynamically adjusted based on the real-time monitoring value of the rated current, so that the amplitude reference value is maintained as a fixed proportion of the rated current. The maximum allowable rate of change of current is determined based on the load type of the power line, and the reference value of the rate of change is set as a fixed proportion of the maximum allowable rate of change of current. During the execution of the latching logic operation, the latching ratio value is updated synchronously according to the current adjustment value of the amplitude reference value; When comparing the time record difference between the local fault marker signal and the current state signal, the time window constraint mechanism in the latching logic operation is used to verify the compliance of the transmission delay tolerance.

3. The digital current detection method according to claim 1, characterized in that, After generating the fault location identifier, the following is included: Based on the fault location identifier, a verification request signal including the location coordinates is sent to the adjacent detection node, and a verification response based on the current state signal is received from the adjacent detection node. When the instantaneous current value in the verification response conflicts with the judgment result of the latching logic operation, the latching logic operation is retried and the value of the transmission delay tolerance is updated. Based on the current channel status of the dual-channel GOOSE communication network, the main channel or the backup channel is selected, and the time record of the finally confirmed fault location identifier and the associated local fault marker signal is sent to the central monitoring server. The central monitoring server generates a positioning log including the location coordinates, the time record, and the locking ratio value, and synchronously updates the set reference value of the amplitude reference value.

4. The digital current detection method according to claim 1, characterized in that, When switching to the backup channel for data transmission, the following is included: Generate a channel switching record that includes the activation time of the backup channel and the number of consecutive losses of the primary channel, and append the channel switching record to the header of the data packet of the local fault marker signal subsequently transmitted through the backup channel; When the backup channel transmits the current status signal, the compensation coefficient of the transmission delay tolerance is adjusted according to the channel switching record in the header of the data packet; During the execution of the latching logic operation, the time record difference between the local fault marker signal and the current state signal is recalculated based on the compensation coefficient of the adjusted transmission delay tolerance; If the backup channel continues to transmit for a stable period, a channel status recovery request carrying the channel switching record is sent to the central monitoring server, and the status monitoring of the main channel is resumed after receiving the switching confirmation instruction issued by the central monitoring server.

5. The digital current detection method according to claim 1, characterized in that, Determining the message retransmission period after a set number of consecutive lost messages on the main channel includes: The status of the main channel of the dual-channel GOOSE communication network is monitored in real time. When a change in the switch quantity is detected, the current message retransmission cycle is interrupted and the change message is immediately retransmitted with the first short cycle. In a steady state without any change in the switching quantity, the message is retransmitted with a second long period, wherein the second long period is longer than the first short period; If multiple messages of the second long period are lost consecutively, the main channel is determined to be disconnected and a channel fault identifier is generated.

6. A digital current protection method, characterized in that, The method includes: The corresponding protection area is determined based on the fault location identifier. The protection area includes the power line section indicated by the fault location identifier and the associated section within an adjacent preset distance. Send a protection action request to the circuit breaker control node within the protection area. The protection action request carries the fault location identifier and the corresponding time record. The circuit breaker control node receives the action response signal fed back. When the instantaneous current value in the action response signal continuously exceeds the amplitude reference value for a preset duration, a protection execution command is generated. The circuit breaker control node is triggered to perform a line disconnection operation according to the protection execution command, and at the same time, the interlocking protection warning including the fault location identifier is sent to the adjacent protection area according to the dual-channel GOOSE communication network. After the line disconnection operation is performed, the current status signal of the protection area is reacquired. When the current status signal indicates that the fault current has not been eliminated, the protection area is iteratively expanded and the protection action request is retried.

7. The digital current protection method according to claim 6, characterized in that, Iteratively expanding the protected area and re-triggering the protection action request includes: When iteratively expanding the protection area, a fault propagation trend analysis result is generated based on the reacquired current state signal and the fault location identifier. The fault propagation trend analysis result is used to quantify the propagation direction and speed of the fault in the power line section. Based on the fault propagation trend analysis results, the coverage of the associated section is adjusted, and an updated protection action request is sent to the circuit breaker control node within the adjusted associated section. After receiving the updated action response signal from the circuit breaker control node, the effectiveness of the protection execution command is verified in conjunction with the interlocking protection early warning. When the instantaneous current value in the updated action response signal still exceeds the amplitude reference value, a protection upgrade command is generated. Based on the protection upgrade command, the dual-channel GOOSE communication network is triggered to send a protection status anomaly report to the central monitoring server and receive protection strategy optimization parameters issued by the central monitoring server. The protection strategy optimization parameters are applied to redetermine the protection area range, and the sending and verification process of the protection action request is iteratively executed until the current status signal indicates that the fault current has been eliminated.

8. The digital current protection method according to claim 7, characterized in that, The results of the fault propagation trend analysis include: The instantaneous current value sequence of the current state signal at at least three detection nodes within the associated section is obtained, and the gradient of the rate of change of current between adjacent nodes is calculated. Based on the consistency of direction and the difference in amplitude of the current change rate gradient, the propagation direction of the fault along the power line section is determined; The fault propagation speed is calculated based on the time difference of current change and physical distance between two consecutive detection nodes in the propagation direction; The product vector of the propagation direction and the fault propagation speed is defined as the result of the fault propagation trend analysis.

9. The digital current protection method according to claim 6, characterized in that, Generate protection execution instructions, including: The waveform distortion rate of the instantaneous current value in the action response signal is verified. When the waveform distortion rate exceeds the preset distortion threshold and continues to reach the preset duration, a first-level protection execution command is generated. According to the first-level protection execution command, the circuit breaker control node is triggered to perform a primary line disconnection operation, and at the same time, the interlocking protection warning, including the primary action intensity, is sent to the adjacent protection area based on the dual-channel GOOSE communication network. After the primary line disconnection operation is performed, if the reacquired current status signal indicates that the fault current has not been eliminated, harmonic component analysis is performed on the action response signal. When the proportion of a specific harmonic amplitude exceeding the amplitude reference value continues to increase, a second-level protection execution command is generated based on the protection upgrade command. Based on the second-level protection execution command, the circuit breaker control node is triggered to perform a complete line disconnection operation, and the action intensity level of the interlocking protection warning and the urgency level of the fault location identifier are updated.

10. A DC switchgear system for rail transit, characterized in that, The system includes: The distributed detection module is deployed at each node of the power line to collect current signals in real time and generate fault marker signals with precise timestamps. The dual-channel communication management module transmits the fault marking signal according to the primary and backup redundant GOOSE network and executes a dynamic retransmission cycle mechanism to monitor the channel health status. The fault location decision module performs interlocking logic operations on the fault marking signals of the local node and adjacent nodes to generate the fault location identifier of the power line. The channel switching control module automatically switches between primary and backup transmission paths based on the channel health status and adjusts the delay compensation parameters during switching. The protection execution linkage module triggers the circuit breaker's graded protection action based on the fault location identifier and sends a cascading protection warning to the area where the adjacent node is located. The central monitoring and analysis module receives and stores fault location data, and dynamically optimizes protection strategy parameters and channel management thresholds.

Images