Single-phase ground fault feeder protection method based on wide-area synchronous measurement

Abstract

The application relates to a single-phase ground fault feeder protection method based on wide-area synchronous measurement, which comprises the following steps: configuring a quick-acting timer T d and an isolation timer Tx; continuously monitoring zero sequence voltage or zero sequence current or three-phase current variation through a control node to determine whether a ground fault occurs; after determining that the fault triggering condition is met, simultaneously starting single-point fault judgment based on single-point local information and multi-point fault judgment based on section multi-point information through the control node, selecting different process treatments according to different time delay conditions of multi-fault positioning results, and finally realizing the requirements of quick action, sensitivity, accuracy and selectivity of fault protection by different combinations of single-point fault judgment positioning and multi-point fault judgment positioning under all possible time delays. Thus, the problems of accurate positioning and rapid isolation of single-phase ground faults in medium-voltage distribution networks are solved, and effective feeder protection of single-phase ground faults is realized.

Description

Technical Field

[0001] This invention relates to a fault feeder protection method, and more particularly to a single-phase ground fault feeder protection method based on wide-area synchronous measurement. Background Technology

[0002] Statistical data shows that most power grid faults occur in the distribution network, and 80% of distribution network faults are single-phase grounding faults. When a single-phase grounding fault occurs, the voltage of the healthy phase to ground increases, and arcing overvoltage can also occur, causing the accident to escalate, and even resulting in personal injury or death and forest fires. It can also easily develop into a short-circuit fault, causing line tripping and power outages, affecting the reliability of power supply.

[0003] In my country, distribution networks mostly adopt a neutral point low-current grounding method. Single-phase grounding fault characteristic currents are weak, and the network structure is complex with numerous branches, also affected by transition resistance, resulting in a lack of complete methods for feeder protection against grounding faults. Currently used feeder protection devices primarily perform line selection functions, with practical application results falling short of expectations. In recent years, integrated primary and secondary intelligent circuit breakers supporting single-phase grounding fault detection have emerged. These devices can detect single-phase grounding faults with obvious fault characteristics by using single-point information, typically the local zero-sequence voltage / zero-sequence current phase relationship. However, the detection accuracy for high-resistance faults and arcing faults remains low, and it is difficult to distinguish the upstream or downstream relationship between circuit breakers belonging to the same fault. Confirmation requires techniques such as differential grading and repeated reclosing. In practical applications, fault isolation functions are rarely used; they are only used for auxiliary fault location functions.

[0004] In view of the above-mentioned shortcomings, the designer actively researched and innovated in order to create a single-phase grounding fault feeder protection method based on wide-area synchronous measurement, so as to make it more valuable for industrial application. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to provide a single-phase grounding fault feeder protection method based on wide-area synchronous measurement.

[0006] The single-phase grounding fault feeder protection method based on wide-area synchronous measurement of the present invention includes the following steps:

[0007] Configure the speed timer T respectively d Soft-motion and fast-motion timer T s With isolation timer T x ;

[0008] By controlling the nodes, the changes in zero-sequence voltage, zero-sequence current, or three-phase current are continuously monitored to determine whether a ground fault has occurred.

[0009] The judgment criteria adopted are that the sudden change of one of the three factors, namely zero-sequence voltage, zero-sequence current, and three-phase current, exceeds a preset threshold, or the absolute amplitude of one of the three factors exceeds a preset threshold.

[0010] After determining that the fault triggering conditions are met, the slew timer T is started via the control node. d Soft-motion timer T s The remote backup sprint timer TTn simultaneously initiates single-point fault assessment bit determination based on local single-point information and multi-point fault assessment bit determination based on segment multi-point information. This is used to subsequently select between multi-point branch process execution and single-point branch process execution. Let TTn = TT0 + n*ΔTT. Different control nodes gradually increase the time difference ΔTT from downstream to upstream. The sprint timer T d Soft-motion and fast-motion timer T s The remote backup fast timer TTn automatically resets after the characteristics of a single-phase ground fault disappear and stops accumulating time.

[0011] Furthermore, in the aforementioned feeder protection method for single-phase ground faults based on wide-area synchronous measurement, a fast-acting timer T is activated via a control node. d , in T d The fault status can be determined by monitoring changes in zero-sequence voltage, zero-sequence current, or three-phase current within a given timeframe.

[0012] If the fault has disappeared, the judgment process will be terminated, indicating that this was a transient disturbance that can be located. The fault will be reported as monitoring information or recorded locally, and no controller operation will be initiated.

[0013] If the speed timer T d If a timeout occurs, it means that the fault continues. The control node will determine whether there are multi-point fault location results. If there are multi-point fault location results, the subsequent execution will follow the multi-point branch process based on multi-point location.

[0014] If there are no multi-point location results, but the single-point location result based on local fault characteristics meets the confidence requirement, then the single-point branch process of single-point location will be executed.

[0015] If the single-point location result based on local fault characteristics is not output or cannot meet the confidence requirement, continue waiting for the multi-point location result until the easing timer T. s Returned after timeout.

[0016] Furthermore, in the aforementioned feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, the multi-point branching process is executed as follows: In T... d At any given time, the control node obtains the multi-point fault location results, and after using the fixed-point location algorithm, determines whether the fault result is outside the section or inside the section;

[0017] If the fault is within the section, the control node is located upstream of the fault point, and the ground fault is still ongoing, and the line switch controlled by the control node is in the closed state, then a tripping operation will be performed.

[0018] If the tripping operation fails, it returns. If the tripping operation succeeds and the ground fault characteristics disappear, it means that the fault has been isolated. If the automatic reclosing function is not supported, the information of permanent tripping success is sent to the downstream adjacent control node in the same section to complete the nearby isolation of the fault point upstream.

[0019] If the control node supports the automatic reclosing function for ground faults, the automatic reclosing procedure for ground faults is executed. If the ground fault does not disappear after reclosing, and the fault disappears after the circuit is opened again, a permanent opening success message is sent to the downstream adjacent control node in the same section to complete the nearest isolation of the fault point upstream.

[0020] If the fault disappears after reclosing, it can be considered a transient fault, and the fault handling is completed.

[0021] If it falls within the same section and the control node is downstream of the fault point, then the isolation timer T is started. x If the isolation timer T x If the timeout occurs and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, the switch controlled by that control node will be tripped, thereby completing the nearest isolation downstream of the fault point.

[0022] Furthermore, in the aforementioned feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, the single-point branch process is executed as follows:

[0023] If the speed timer T d If a timeout occurs, and a single-point positioning result is output but a multi-point positioning result has not yet been obtained, the control node starts two timers, namely the protection differential timer Tn.

[0024] Let Tn = T0 + n*ΔT, and the time difference ΔT increases progressively from downstream to upstream for different control nodes;

[0025] The appropriate action is taken based on the timeout of the protection level difference timer Tn.

[0026] Furthermore, in the aforementioned feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, wherein,

[0027] If the single-point fault location result is upstream of the fault, and the protection differential timer Tn timer expires, then the circuit breaker will be tripped;

[0028] If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker should be quickly closed and the tripped circuit breaker should be locked for a period of time.

[0029] If the ground fault disappears after the circuit breaker is tripped and reclosing is not supported, a permanent tripping success message is sent to the downstream control node in the same section. If reclosing is supported, the reclosing process is executed again. If the reclosing is successful, it is considered a transient fault, and the switch is eventually closed. If the reclosing is unsuccessful and the switch is eventually in the tripped state, a permanent tripping success message is sent to the downstream control node in the same section to complete the nearest isolation of the fault upstream.

[0030] If the single-point fault location result is upstream of the fault, and the remote backup differential timer TTn times out and the ground fault continues, then the circuit breaker will be tripped.

[0031] If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker should be quickly closed and the tripped circuit breaker should be locked for a period of time.

[0032] If the ground fault disappears after the circuit breaker is tripped, a permanent tripping success message is sent to the control node downstream in the same section to complete the isolation of the upstream of the fault point.

[0033] Furthermore, in the aforementioned feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, if the single-point fault location result is not upstream of the fault point, the system continues to wait for the reception of multi-point fault location results corresponding to the fault time until the remote backup timer TTn times out. If multi-point fault location results are obtained, and they are located within the section and determined to be downstream nodes of the fault point, then the isolation timer T is started. x If the isolation timer T x If the timeout occurs and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, the switch controlled by that control node will be tripped to complete the nearest isolation downstream of the fault point.

[0034] Furthermore, in the above-mentioned single-phase ground fault feeder protection method based on wide-area synchronous measurement, if the remote backup timer TTn times out, the circuit breaker is tripped.

[0035] If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker will be quickly closed and the tripped circuit breaker will be locked for a preset time, which is 30 seconds to 30 minutes.

[0036] If the ground fault disappears after the circuit breaker is tripped, a permanent tripping success message is sent to the control node downstream in the same section to complete the nearest isolation upstream of the fault point.

[0037] By means of the above-described solution, the present invention has at least the following advantages:

[0038] By combining the results of single-point fault location algorithms based on local fault characteristics and multi-point fault location algorithms based on wide-area measurement, the problem of accurate location and rapid isolation of single-phase grounding faults in medium-voltage distribution networks is solved, and effective feeder protection for single-phase grounding faults is achieved.

[0039] Furthermore, in the aforementioned feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, each control node uses different single-phase grounding fault location algorithms based on local fault characteristics, depending on the amount of sampling it can obtain, to determine whether it is upstream or downstream of the fault point. For control nodes with three-phase current and zero-sequence current signals, fault location is performed based on a zero-sequence overcurrent algorithm or on the asymmetry of three-phase changes. If a control node can directly or indirectly measure a zero-sequence voltage signal, a corresponding algorithm based on the phase relationship between zero-sequence current and zero-sequence voltage is used to determine whether the node is upstream of the fault point.

[0040] If, within a segment, both control nodes can obtain the synchronized three-phase current waveforms and zero-sequence voltage waveforms of the control node and the confidence node of that segment at the time of the fault, then multi-point comparison of the zero-sequence current waveforms of different nodes, or multi-point comparison of the zero-sequence current / zero-sequence voltage phases, or multi-point comparison of the three-phase change asymmetry, or the differences in different fault characteristics between the upstream and downstream of the fault point and other non-faulty lines, can be used to achieve single-phase grounding fault determination based on multiple points. When the data fault characteristics within the segment are highly consistent, the output is always an external fault. When the data fault characteristics within the segment are inconsistent, the output is an internal fault. The control node can then further determine whether it is located upstream or downstream of the fault point.

[0041] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the implementation process of a single-phase grounding fault feeder protection method based on wide-area synchronous measurement.

[0043] Figure 2 This is a schematic diagram of the execution of a multi-branch process.

[0044] Figure 3 This is a schematic diagram of the execution of a single-point branch process.

[0045] Figure 4 This is a schematic diagram of the reclosing process. Detailed Implementation

[0046] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] like Figures 1 to 4A single-phase ground fault feeder protection method based on wide-area synchronous measurement is characterized by the following steps: configuring a fast-acting timer T respectively. d Soft-motion and fast-motion timer T s With isolation timer T x During implementation, the changes in zero-sequence voltage, zero-sequence current, or three-phase current are continuously monitored through control nodes. Furthermore, the method of continuously monitoring changes in zero-sequence current or three-phase current is applicable to nodes where zero-sequence voltage cannot be monitored. This is used to determine whether a ground fault has occurred. The judgment criterion adopted in this invention is that the sudden change in one of the three changes—zero-sequence voltage, zero-sequence current, or three-phase current—exceeds a preset threshold, or the absolute amplitude of one of the three exceeds a preset threshold. For certain special situations, both conditions can be met simultaneously. After determining that the fault triggering condition is met, a fast-acting timer T is started through the control node. d Soft-motion timer T s A backup slew timer TTn is used. Simultaneously, single-point fault assessment bits based on local single-point information and multi-point fault assessment bits based on segment multi-point information are initiated to subsequently select between multi-point branch process execution and single-point branch process execution. During implementation, TTn = TT0 + n*ΔTT, and the time difference ΔTT is increased progressively from downstream to upstream for different control nodes, utilizing the slew timer T. d Soft-motion and fast-motion timer T s The remote backup fast timer TTn automatically resets after the characteristics of a single-phase ground fault disappear and stops accumulating time.

[0048] In a preferred embodiment of the present invention, the speed timer T is started via the control node. d , in T d The system can determine whether the fault continues by monitoring changes in zero-sequence voltage, zero-sequence current, or three-phase current within a given timeframe, and then make corresponding judgments and take appropriate actions.

[0049] Specifically, if the fault has disappeared, the judgment process exits, indicating that this was a transient disturbance, and the fault location can be completed. This information is then reported as monitoring information or recorded locally, without initiating any controller operation. If the slew rate timer T... d If a timeout occurs, it indicates that the fault continues. The control node checks whether multi-point fault location results have been obtained. If multi-point fault location results are available, the subsequent execution follows the multi-point branching process based on multi-point location. If no multi-point location results are available, but the single-point location result based on local fault characteristics meets the confidence requirement, the execution follows the single-point branching process combining single-point location and multi-point location. Simultaneously, if the single-point location result based on local fault characteristics is not output or does not meet the confidence requirement, the system continues to wait for multi-point location results until the easing timer T. s Returns after timeout. During implementation, timer T...d The settings can be adapted to specific on-site requirements, such as the need for wildfire prevention and rapid isolation of grounding faults, and timer T. d The timer should be set to less than 1 second, such as 0.4 seconds. To minimize tripping and avoid instantaneous grounding, timer T should be used. d It can also be set to tens of seconds, or even minutes. Regardless of the timer T... d With the size set, this method combines multi-point and single-point methods to achieve fast and accurate single-phase grounding feeder protection without requiring the use of fiber optic communication or 5G communication.

[0050] Furthermore, the multi-point branching process employed in this invention is executed as follows: At T d At any given time, the control node obtains the multi-point fault location results, and after using the fixed-point location algorithm, determines whether the fault result is outside the section or inside the section.

[0051] If the fault is within the section, the control node is located upstream of the fault point, and the ground fault is still ongoing, and the line switch controlled by the control node is in the closed state, then the tripping operation will be performed.

[0052] If the tripping operation fails, it returns. If the tripping operation succeeds and the ground fault characteristics disappear, it indicates that the fault has been isolated. If the automatic reclosing function is not supported, a message indicating that the permanent tripping has been successfully sent to the downstream adjacent control node in the same section is also sent to complete the nearest isolation upstream of the fault point.

[0053] During implementation, if the control node supports automatic reclosing for ground faults, the automatic reclosing procedure for ground faults will be executed. If the ground fault does not disappear after reclosing, and the fault disappears upon reclosing, a permanent reclosing success message will be sent to the downstream adjacent control node in the same section, completing the nearest isolation upstream of the fault point. If the fault disappears after reclosing, it can be considered a momentary fault, and the fault handling ends.

[0054] If it falls within the same section and the control node is downstream of the fault point, then the isolation timer T is started. x If the isolation timer T x Timeout (T) x If the time exceeds the maximum delay for automatic reclosing, and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, then the switch controlled by that control node will be tripped, thus completing the nearest isolation downstream of the fault point. The isolation timer Tx needs to be set to be greater than the delay of the upstream reclosing completion (if reclosing is supported) plus the delay typically required to receive the permanent tripping success message from the upstream control node, for example, T... x The delay is set to 30 seconds.

[0055] In practical implementation, the single-point branch process adopted in this invention is executed as follows:

[0056] If the speed timer T d If a timeout occurs, and a single-point positioning result is output but a multi-point positioning result has not yet been obtained, the control node starts two timers: a protection differential timer Tn. Let Tn = T0 + n*ΔT. Different control nodes increase the time difference ΔT progressively from downstream to upstream. Appropriate handling is performed based on the timeout of the protection differential timer Tn. In implementation, different control nodes increase the time differences ΔT and ΔT progressively from downstream to upstream. For example, T0 = 1 second, ΔT = 2 seconds; TT0 = 60 seconds. Therefore, separate handling is performed based on the timeouts of the protection differential timer Tn and the remote backup differential timer TTn.

[0057] Furthermore, if the single-point fault location result indicates the fault is upstream, and the protection differential timer Tn times out, indicating a persistent ground fault, then the circuit breaker will be tripped. Specifically, if the ground fault persists after tripping, the circuit breaker will be quickly closed and the tripped circuit breaker will be blocked for a period of time. Simultaneously, if the ground fault disappears after tripping and reclosing is not supported, a permanent tripping success message will be sent to the downstream control node in the same section, completing the nearest isolation of the upstream fault. During implementation, if reclosing is supported, the reclosing procedure will be executed again. If reclosing is successful, it is considered a transient fault, and the switch will eventually be in the closed state. If reclosing fails, and the switch is ultimately in the open state, a permanent tripping success message will be sent to the downstream control node in the same section.

[0058] Furthermore, if the single-point fault location result indicates the fault is upstream, and the ground fault persists despite the remote backup differential timer TTn expiring, the circuit breaker will be tripped. If the ground fault persists after tripping, the circuit breaker will be quickly closed and the tripped fault will be blocked for a period of time. Simultaneously, if the ground fault disappears after tripping, a permanent tripping success message will be sent to the downstream control node in the same section. During implementation, if the single-point fault location result is not upstream of the fault point, the system will continuously wait for the multi-point fault location result corresponding to the fault time to be received until the remote backup timer TTn expires. If a multi-point fault location result is obtained, and it is located within the section and determined to be a downstream node of the fault point, the isolation timer T will be started. x If the isolation timer T x If the timeout occurs and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, the switch controlled by that control node will be tripped to complete the nearest isolation downstream of the fault point.

[0059] If the remote backup timer TTn times out, the circuit breaker will trip. If the ground fault persists after tripping, the circuit breaker will be quickly closed and the tripped circuit breaker will be locked for a preset time. For ease of implementation, the preset time is 30 seconds to 30 minutes. If the ground fault disappears after tripping, a permanent tripping success message will be sent to the downstream control node in the same section, completing the nearest isolation upstream of the fault point.

[0060] The working principle of this invention is as follows:

[0061] To better implement this invention, the power grid can be composed of several nodes comprising a feeder. These nodes are divided into two categories: one category is called "control nodes," which includes all pole-mounted switches (and their controllers) on the feeder that can perform opening and closing and support communication with other nodes. The other category is called "information nodes," which includes all types of measurement terminals on the feeder that can provide wide-area synchronous three-phase current / voltage measurement data and can also communicate with other nodes.

[0062] Furthermore, following the direction of current flow from the substation out of the busbar, two adjacent upstream and downstream control nodes constitute a "segment." "Adjacent" means there are no other control nodes between the two control nodes; there may be several information nodes (or none). During implementation, the most special "segments" are the beginning and end of the line. If the first set of upstream control nodes is not located at the first pole of the line, in order to accurately locate faults within the range from the first set of control nodes to the first pole, a set of information nodes can be installed at the first pole. In this case, this set of information nodes and the first set of control nodes also form a special "head section." Similarly, the control node located at the very downstream of the line can form a special "tail section" with its downstream information nodes.

[0063] Each control node, based on its available sampling data, employs different single-phase ground fault location algorithms based on local fault characteristics to determine whether it is upstream or downstream of the fault point (being located on a non-faulty line and downstream of the fault point have the same characteristics and are equivalent, so there is no need to distinguish between these two cases). Control nodes with only three-phase current and zero-sequence current signals primarily rely on commonly used zero-sequence overcurrent algorithms (setting a threshold for zero-sequence current and determining whether it is upstream of the fault based on whether the actual zero-sequence current exceeds the threshold), or commonly used fault location based on the asymmetry of three-phase changes, or a combination of two algorithms. If the control node can also directly or indirectly measure the zero-sequence voltage signal, it can also use various algorithms based on the phase relationship between zero-sequence current and zero-sequence voltage (e.g., zero-sequence active power, zero-sequence reactive power, etc.) to determine whether the node is upstream of the fault point.

[0064] Multi-point based single-phase grounding fault location refers to a situation where, within a certain section, two control nodes can obtain the synchronized three-phase current waveforms and zero-sequence voltage waveforms of the control node and the confidence node at the time of the fault. Multi-point comparisons of zero-sequence current waveforms, zero-sequence current / voltage phases, and three-phase asymmetry are achieved through multi-point comparisons of these waveforms. This leverages the differences (inconsistencies) in fault characteristics between upstream and downstream of the fault point, or between the upstream of the fault line and other non-faulty lines, as well as the high consistency of fault characteristics between lines located upstream or downstream of the fault point. This improves location accuracy, especially overcoming the limitation of single-point feature-based fault location relying on a certain absolute threshold setting, ensuring that fault location can cover more scenarios and is more accurate. Furthermore, the introduction of a more reliable multi-point based fault location algorithm improves the confidence of single-point fault feature-based fault location algorithms, resulting in higher accuracy when output is available. This allows for the rapid isolation of grounding faults with obvious fault characteristics and greater relative harm using single-point fault location algorithms.

[0065] Meanwhile, the segmented fault location results based on multiple points are mainly obtained by two control nodes. When the data fault characteristics within a segment are highly consistent, the output is always an external fault (regardless of whether the node is upstream or downstream of the fault point). When the data fault characteristics within a segment are inconsistent, the output is an internal fault, and the control node will further determine whether it is upstream or downstream of the fault point. This applies to the special head and tail nodes mentioned above.

[0066] It should be noted that the segment division during implementation is not limited to the upstream and downstream adjacent method. For example, the method of this control node + adjacent upstream control node + adjacent downstream control node can also be used. It is just a specific variation. The principle and method are the same, and will not be elaborated on again.

[0067] Multi-point segmented fault location is more reliable and accurate, and does not rely on absolute thresholds. However, because it requires communication between multiple nodes (at least two nodes), it increases communication latency compared to decisions based on local fault characteristics, and different communication methods will have different communication latency. For example, using wired fiber optic communication or 5G wireless communication, the latency may be within 100 milliseconds, while using 4G wireless communication, the latency may be within 10 seconds. This invention addresses this by setting a waiting delay T. d Through T d Whether the segmented fault location results based on multiple points can be received within a certain time frame is determined by different branching processes, thereby ensuring that both millisecond-level and second-level communication delays can be handled and are not limited by the actual communication method used.

[0068] As can be seen from the above description and the accompanying drawings, the present invention has the following advantages: it combines the results of a single-point fault location algorithm based on local fault characteristics and a multi-point fault location algorithm based on wide-area measurement, thus solving the problem of accurate location and rapid isolation of single-phase grounding faults in medium-voltage distribution networks and realizing effective feeder protection for single-phase grounding faults.

[0069] Furthermore, the orientations or positional relationships described in this invention are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the purpose of facilitating the description of this invention and simplifying the description, and are not intended to indicate or imply that the device or structure referred to must have a specific orientation, or to operate in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A feeder protection method for single-phase grounding faults based on wide-area synchronous measurement, characterized in that... Includes the following steps: Configure the sprint timer Td and the slow sprint timer Ts respectively; By controlling the nodes, the changes in zero-sequence voltage, zero-sequence current, or three-phase current are continuously monitored to determine whether a ground fault has occurred. The judgment criteria adopted are that the sudden change of one of the three factors, namely zero-sequence voltage, zero-sequence current, and three-phase current, exceeds a preset threshold, or the absolute amplitude of one of the three factors exceeds a preset threshold. After determining that the fault triggering conditions are met, the slew timer T is started via the control node. d Soft-motion timer T s The remote backup sprint timer TTn simultaneously activates single-point fault assessment bits based on local single-point information and multi-point fault assessment bits based on segment multi-point information. This is used to subsequently select between multi-point branch process execution and single-point branch process execution. Let TTn = TT0 + n * ΔTT, where TT0 is the value of the remote backup sprint timer for the first-level control node from downstream to upstream according to the topology. The k-th level control node from downstream to upstream corresponds to node n = k-1. The time difference ΔTT increases progressively from downstream to upstream for different control nodes. The sprint timer T... d Soft-motion and fast-motion timer T s The remote backup fast timer TTn automatically resets after the characteristics of a single-phase ground fault disappear and stops accumulating time.

2. The method for single-phase ground fault feeder protection based on wide-area synchronous measurement according to claim 1, characterized in that: Start the speed timer T via the control node. d , in T d The fault status can be determined by monitoring changes in zero-sequence voltage, zero-sequence current, or three-phase current within a given timeframe. If the fault has disappeared, the judgment process will be terminated, indicating that this was a transient disturbance that can be located. The fault will be reported as monitoring information or recorded locally, and no controller operation will be initiated. If the speed timer T d If a timeout occurs, it means that the fault continues. The control node will determine whether there are multi-point fault location results. If there are multi-point fault location results, the subsequent execution will follow the multi-point branch process based on multi-point location. If there are no multi-point location results, but the single-point location result based on local fault characteristics meets the confidence requirement, then the single-point branch process of single-point location will be executed. If the single-point location result based on local fault characteristics is not output or cannot meet the confidence requirement, continue to wait for the multi-point location result until the easing-speed timer T. s Returned after timeout.

3. The single-phase grounding fault feeder protection method based on wide-area synchronous measurement according to claim 1, characterized in that: Configure isolation timer T x ; The multi-point branching process is executed as follows: during the sprint timer T... d Before the timeout, the control node obtains the multi-point fault location results. After using the multi-point location algorithm, it determines whether the fault result is outside the segment or inside the segment. If the fault is within the section, the control node is located upstream of the fault point, and the ground fault is still ongoing, and the line switch controlled by the control node is in the closed state, then a tripping operation will be performed. If the tripping operation fails, it returns. If the tripping operation succeeds and the ground fault characteristics disappear, it means that the fault has been isolated. If the automatic reclosing function is not supported, the information of permanent tripping success is sent to the downstream adjacent control node in the same section to complete the nearby isolation of the fault point upstream. If the control node supports the automatic reclosing function for ground faults, the automatic reclosing procedure for ground faults is executed. If the ground fault does not disappear after reclosing, and the fault disappears after the circuit is opened again, a permanent opening success message is sent to the downstream adjacent control node in the same section to complete the nearest isolation of the fault point upstream. If the fault disappears after reclosing, it can be considered a transient fault, and the fault handling is completed. If it falls within the same section and the control node is downstream of the fault point, then the isolation timer T is started. x If the isolation timer T x If the timeout occurs and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, the switch controlled by that control node will be tripped, thereby completing the nearest isolation downstream of the fault point.

4. The single-phase grounding fault feeder protection method based on wide-area synchronous measurement according to claim 1, characterized in that: The execution process of the single-point branch process is as follows: If the speed timer T d If a timeout occurs, and a single-point positioning result is output but a multi-point positioning result has not yet been obtained, the control node will start the protection differential timer Tn. Let Tn = T0 + n * ΔT, where T0 is the protection level timer value of the first-level control node from downstream to upstream according to the topology relationship, and the k-th level control node from downstream to upstream according to the topology relationship, corresponding to n = k - 1 for this node. The time difference ΔT increases step by step from downstream to upstream for different control nodes. The appropriate action should be taken based on the timeout of the protection level timer Tn; If the single-point fault location result is upstream of the fault, and the protection differential timer Tn timer expires, then the circuit breaker will be tripped; If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker should be quickly closed and the tripped circuit breaker should be locked for a period of time. If the ground fault disappears after the circuit breaker is tripped and reclosing is not supported, a permanent tripping success message is sent to the downstream control node in the same section. If reclosing is supported, the reclosing process is executed again. If the reclosing is successful, it is considered a transient fault, and the switch is eventually closed. If the reclosing is unsuccessful and the switch is eventually in the tripped state, a permanent tripping success message is sent to the downstream control node in the same section to complete the nearest isolation of the fault upstream. If the single-point fault location result is upstream of the fault, and the remote backup fast-acting timer TTn times out and the ground fault continues, then the circuit breaker will be tripped. If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker should be quickly closed and the tripped circuit breaker should be locked for a period of time. If the ground fault disappears after the circuit breaker is tripped, a permanent tripping success message is sent to the control node downstream in the same section to complete the isolation of the upstream fault.

5. The single-phase grounding fault feeder protection method based on wide-area synchronous measurement according to claim 4, characterized in that: If the single-point fault location result is not upstream of the fault point, the system continues to wait for the corresponding multi-point fault location result at the time of the fault until the remote backup quick-acting timer TTn times out. During this period, if a multi-point fault location result is obtained, and it is located within the segment and determined to be a downstream node of the fault point, then the isolation timer T is started. x If the isolation timer T x If the timeout occurs and a permanent tripping success message is received from the upstream control node in the same section, or a power supply side undervoltage message is received, the switch controlled by that control node will be tripped to complete the isolation of the downstream of the fault point.

6. The single-phase grounding fault feeder protection method based on wide-area synchronous measurement according to claim 4, characterized in that: If the remote backup fast-acting timer TTn times out, the circuit breaker will be tripped. If the ground fault does not disappear after the circuit breaker is tripped, the circuit breaker will be quickly re-closed and the tripped circuit breaker will be locked for a preset time, which is 30 seconds to 30 minutes. If the ground fault disappears after the circuit breaker is tripped, a permanent tripping success message is sent to the control node downstream in the same section to complete the nearest isolation upstream of the fault point.

7. The single-phase ground fault feeder protection method based on wide-area synchronous measurement according to claim 1, characterized in that: Each control node uses different single-phase ground fault location algorithms based on local fault characteristics, depending on the amount of sampling it can obtain, to determine whether it is upstream or downstream of the fault point. For control nodes with three-phase current and zero-sequence current signals, fault location is performed based on the zero-sequence overcurrent algorithm or the asymmetry of three-phase changes. If the control node can directly or indirectly measure the zero-sequence voltage signal, it uses a corresponding algorithm based on the phase relationship between zero-sequence current and zero-sequence voltage to determine whether the node is upstream of the fault point. If, within a segment, both control nodes can obtain the synchronized three-phase current waveforms and zero-sequence voltage waveforms of the control node and the confidence node of that segment at the time of the fault, then multi-point comparison of the zero-sequence current waveforms of different nodes, or multi-point comparison of the zero-sequence current / zero-sequence voltage phases, or multi-point comparison of the three-phase change asymmetry, or the differences in different fault characteristics between the upstream and downstream of the fault point and other non-faulty lines, can be used to achieve single-phase grounding fault determination based on multiple points. When the data fault characteristics within the segment are highly consistent, the output is always an external fault. When the data fault characteristics within the segment are inconsistent, the output is an internal fault. The control node can then further determine whether it is located upstream or downstream of the fault point.

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