A power distribution network fault detection method and device based on current transient characteristics

Abstract

The application discloses a power distribution network fault detection method and device based on current transient characteristics, and belongs to the technical field of power distribution network fault detection. The method is as follows: collecting zero sequence voltage of a neutral point port of a power distribution network and three-phase current data of each measurement port; traversing the three-phase current data through a preset sliding window; in the traversal process, forming a plurality of sliding window data blocks and storing them in a cache area in chronological order; calculating a target difference value between three-phase current data in a currently latest sliding window data block in the cache area and three-phase current data in a historically earliest sliding window data block; determining a fault condition of the power distribution network according to an effective value of the zero sequence voltage and all target difference values, and determining a fault section according to all single-phase ground fault measurement points. Through implementation of the application, the problem that the prior art cannot accurately detect the fault condition of the power distribution network can be solved.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault detection technology, and in particular to a power distribution network fault detection method and device based on current transient characteristics. Background Technology

[0002] Distribution network relay protection is crucial for ensuring safe and stable power supply. Traditional longitudinal differential protection is mostly based on comparing the amplitude and phase of power frequency current, which has significant limitations in low-current grounding distribution networks. In low-current grounding systems, the single-phase ground fault current is weak, and traditional protection methods lack sufficient sensitivity, making it difficult to reliably identify the fault.

[0003] In terms of fault detection, existing methods mostly compare and judge directly with the raw three-phase current data, which is easily affected by factors such as load fluctuations and distributed power supply access. The fault characteristics are not obvious, and misjudgment and failure to operate are easy to occur. Moreover, most of them rely on the magnitude of the fault current to judge, without making full use of the transient characteristics of the fault, and cannot effectively distinguish between single-phase grounding and phase-to-phase short circuit. Summary of the Invention

[0004] This invention provides a method and apparatus for detecting distribution network faults based on transient current characteristics. The method can solve the problem that existing technologies are unable to accurately detect distribution network faults.

[0005] To address the aforementioned technical problems, one embodiment of the present invention provides a distribution network fault detection method based on current transient characteristics, comprising: Collect zero-sequence voltage at the neutral point port of the distribution network and three-phase current data at each measurement port; The three-phase current data is traversed through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. Calculate the target difference between the three-phase current data in the latest sliding window data block in the buffer and the three-phase current data in the earliest historical sliding window data block. When the effective value of the zero-sequence voltage exceeds the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is a single-phase grounding fault in the distribution network. The transient change amplitude of each measurement port at the time of the single-phase grounding fault is calculated. The measurement port whose transient change amplitude exceeds the preset third threshold is taken as the single-phase grounding fault measurement point. Based on all the single-phase grounding fault measurement points, the fault section is determined. When any target difference is detected to exceed the preset second threshold, it is determined that there is a phase-to-phase short-circuit fault in the distribution network. The measurement port where the target difference exceeds the preset second threshold is taken as the single-phase grounding fault measurement point, and the fault section is determined based on all the single-phase grounding fault measurement points. When the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is no fault in the distribution network.

[0006] Furthermore, the process of traversing the three-phase current data through a preset sliding window generates several sliding window data blocks during the traversal process, which are then stored in a buffer in chronological order, including: Park transformation is performed on all the collected three-phase current data to obtain the DC component corresponding to each three-phase current data. The DC component includes the d-axis DC component and the q-axis DC component. A preset sliding window is invoked to traverse each DC component, and N sliding window data blocks are updated and stored in the buffer in real time according to the chronological order; wherein, each sliding window data block includes the maximum and minimum values ​​of each DC component; N is a positive integer.

[0007] Furthermore, the target difference between the three-phase current data in the latest sliding window data block and the three-phase current data in the earliest historical sliding window data block in the calculation cache includes: Based on the maximum and minimum values ​​of each DC component in the latest sliding window data block in the buffer, the first mean value of each DC component in the latest sliding window data block is calculated. The second mean of each DC component in the earliest historical sliding window data block is calculated based on the maximum and minimum values ​​of each DC component in the earliest historical sliding window data block. Calculate the first difference between the first mean of each DC component and the second mean of each DC component, and take the first difference with the largest value as the target difference.

[0008] Furthermore, the extreme values ​​include both the maximum and minimum values; The calculation of the transient amplitude of each measurement port at the moment of occurrence of a single-phase ground fault, and the determination of the measurement port whose transient amplitude exceeds a preset third threshold as the single-phase ground fault measurement point, includes: All time window data blocks at the moment a single-phase ground fault occurs are used as reference sliding window data blocks; each reference sliding window data block corresponds to a measurement port; Extract the mean value of each DC component in the preceding sliding window data block of the reference sliding window data block, and extract the maximum value of each DC component in the following reference sliding window data block. Calculate the difference between the maximum value and the corresponding mean value of each DC component, and use it as the second difference value; For each measurement port, the second largest difference is taken as the transient change amplitude of the current measurement port; Measurement ports whose transient amplitude exceeds the preset third threshold are identified as single-phase grounding fault measurement points.

[0009] Furthermore, determining the fault section based on all single-phase ground fault measurement points includes: When it is determined that there is only one single-phase ground fault measurement point, the section located downstream of the single-phase ground fault measurement point is taken as the fault section; When two or more single-phase ground fault measurement points are identified, the section downstream of the downstreamst single-phase ground fault measurement point is taken as the fault section.

[0010] Furthermore, after determining that a phase-to-phase short-circuit fault exists in the distribution network and identifying the fault section based on all single-phase grounding fault measurement points, the process also includes: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network.

[0011] Furthermore, the aforementioned distribution network fault detection method based on current transient characteristics also includes: When the effective value of the zero-sequence voltage exceeds the preset first threshold, a first fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. When any mean value is detected to exceed a preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port.

[0012] An embodiment of the present invention also provides a distribution network fault detection device based on current transient characteristics, comprising: a data acquisition module, a data identification module, a calculation module, a first detection module, a second detection module, and a third detection module; The data acquisition module is used to acquire the zero-sequence voltage at the neutral point port of the distribution network and the three-phase current data at each measurement port. The data recognition module is used to traverse the three-phase current data through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. The calculation module is used to calculate the target difference between the three-phase current data in the latest sliding window data block in the buffer and the three-phase current data in the earliest historical sliding window data block. The first detection module is used to determine that there is a single-phase grounding fault in the distribution network when the effective value of the zero-sequence voltage exceeds a preset first threshold and all target differences do not exceed a preset second threshold, calculate the transient change amplitude of each measurement port at the time of the single-phase grounding fault, take the measurement port whose transient change amplitude exceeds a preset third threshold as the single-phase grounding fault measurement point, and determine the fault section based on all the single-phase grounding fault measurement points. The second detection module is used to determine that there is a phase-to-phase short circuit fault in the distribution network when any target difference exceeds a preset second threshold, to take the measurement port where the target difference exceeds the preset second threshold as a single-phase ground fault measurement point, and to determine the fault section based on all single-phase ground fault measurement points; The third detection module is used to determine that there is no fault in the distribution network when the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold.

[0013] Furthermore, the second detection module is also used for: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network.

[0014] Furthermore, the power distribution network fault detection device based on current transient characteristics also includes: a signal transmission module; The signal transmitting module is used to send a first fault characteristic signal to the neutral point port and each measurement port of the distribution network when it is detected that the effective value of the zero-sequence voltage exceeds a preset first threshold. When any mean value is detected to exceed a preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port.

[0015] The following benefits can be obtained by implementing the present invention: This invention provides a method and apparatus for fault detection in distribution networks based on transient current characteristics. The method collects zero-sequence voltage data from the neutral point port of the distribution network and three-phase current data from each measurement port. It then iterates through the three-phase current data using a preset sliding window. During this process, several sliding window data blocks are formed and stored in a buffer in chronological order. The method then calculates the target difference between the three-phase current data in the latest sliding window data block and the three-phase current data in the earliest historical sliding window data block. This avoids the influence of single-point sampling errors and transient disturbances on fault identification, significantly improving the reliability of fault initiation identification. When the effective value of the zero-sequence voltage exceeds a preset first threshold and all target differences do not exceed a preset second threshold, it is determined that a single-phase fault exists in the distribution network. For ground faults, the transient amplitude of each measurement port at the moment of occurrence of a single-phase ground fault is calculated. Measurement ports whose transient amplitude exceeds a preset third threshold are designated as single-phase ground fault measurement points. When any target difference is detected to exceed a preset second threshold, a phase-to-phase short-circuit fault is determined to exist in the distribution network, and measurement ports whose target difference exceeds the preset second threshold are designated as single-phase ground fault measurement points. Based on all single-phase ground fault measurement points, the fault section is determined. When the effective value of the zero-sequence voltage does not exceed a preset first threshold and all target differences do not exceed a preset second threshold, it is determined that there is no fault in the distribution network. This achieves the discrimination and section location of ground faults and phase-to-phase short-circuit faults, significantly improving the operating speed and location accuracy of longitudinal differential protection, while simplifying the protection logic and improving the overall operational stability of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a distribution network fault detection method based on current transient characteristics provided in a certain embodiment of this application. Figure 2 This is a system topology diagram of a single radial 10kV low-current grounding system provided in a certain embodiment of this application; Figure 3 This is a waveform diagram of the d-axis current component of a faulty circuit provided in a certain embodiment of this application; Figure 4 This is a timing diagram of the first protection action logic under a three-phase short-circuit fault provided in a certain embodiment of this application; Figure 5 This is a timing diagram of the second protection action logic under a three-phase short-circuit fault provided in a certain embodiment of this application; Figure 6 This is a timing diagram of the third protection action logic under a three-phase short-circuit fault provided in a certain embodiment of this application; Figure 7 This is a schematic diagram of the structure of a power distribution network fault detection device based on current transient characteristics provided in a certain embodiment of this application; Figure 8 This is a schematic diagram of the structure of a power distribution network fault detection device based on current transient characteristics provided in another embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] 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 application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0024] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0025] See Figure 1 To address the problem that existing technologies struggle to accurately detect distribution network faults, an embodiment of this invention provides a distribution network fault detection method based on current transient characteristics, comprising: S1. Collect the zero-sequence voltage at the neutral point port of the distribution network and the three-phase current data at each measurement port; Specifically, in order to achieve rapid initiation and type differentiation of distribution network faults, and because the transient characteristics and zero-sequence voltage characteristics of faults can directly reflect whether a grounding or phase-to-phase fault has occurred in the system, it is necessary to collect the zero-sequence voltage at the neutral point and the three-phase current data of each line measurement port in real time, so as to provide data support for subsequent sliding window calculation, mean difference comparison and fault determination.

[0026] S2. Traverse the three-phase current data through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. As an illustration, since the instantaneous current change during a fault cannot be effectively identified by single-point data, it is necessary to construct a stable criterion based on the electrical characteristics of continuous multi-window systems in order to eliminate transient interference, accurately extract the transient features of the fault, and achieve reliable fault initiation discrimination.

[0027] In a preferred embodiment, the step of traversing the three-phase current data through a preset sliding window, during which several sliding window data blocks are formed and stored in a buffer in chronological order, includes: Park transformation is performed on all the collected three-phase current data to obtain the DC component corresponding to each three-phase current data. The DC component includes the d-axis DC component and the q-axis DC component. A preset sliding window is invoked to traverse each DC component, and N sliding window data blocks are updated and stored in the buffer in real time according to the chronological order; wherein, each sliding window data block includes the maximum and minimum values ​​of each DC component; N is a positive integer; Specifically, firstly, Park transformation is performed on all the collected three-phase current data to obtain the DC component corresponding to each three-phase current data. The DC component includes the d-axis DC component and the q-axis DC component. That is, the microprocessor at each measurement port independently processes the instantaneous values ​​of the corresponding three-phase current data. , , Perform the Park transformation using a fixed angular frequency ω = 100π rad / s, obtained through a pre-stored trigonometric function lookup table. and The specific formula for calculating the value of the three-phase current data using the Park transformation is as follows: ; in, , Indicates a time variable (unit: seconds); Represents the DC component of the d-axis; This represents the DC component along the q-axis.

[0028] After the coordinate transformation described above, the fundamental positive-sequence component of the three-phase current can be converted into a stable DC current under steady-state conditions, while the negative-sequence component exhibits a 100Hz alternating component, providing a basis for subsequent fault feature extraction and identification. Three-phase short circuits are symmetrical faults, with the fault current dominated by the positive-sequence component and essentially containing no negative-sequence or zero-sequence components. After the fixed angular velocity dq transformation, the d-axis and q-axis currents mainly exhibit step changes in steady-state quantities, with the following core characteristics: (1) The mean values ​​of d-axis and q-axis currents before and after the fault are significantly different, but due to the lack of negative sequence components, the peak-to-peak values ​​of d-axis and q-axis currents are relatively small.

[0029] (2) Two-phase short circuit and two-phase short circuit to ground are asymmetrical faults, and there is a significant negative sequence component in the fault current.

[0030] (3) In the dq coordinate system rotating at the positive sequence frequency, the negative sequence component will exhibit a periodic fluctuation of 100Hz and be superimposed on the DC component, causing the d and q axis currents to oscillate significantly.

[0031] Therefore, the typical characteristics of this type of fault are: the difference in mean and peak-to-peak values ​​of the d-axis and q-axis currents are both quite prominent.

[0032] Among them, the zero-sequence current is the in-phase current generated when the three-phase current vector sum is not zero. The three phases have equal amplitudes and consistent phases, and have no rotational characteristics. The negative-sequence current is the component with equal amplitudes, phases that are 120° apart in succession, and whose rotational direction is opposite to that of the positive-sequence component when the system is unbalanced.

[0033] Then, a preset sliding window is invoked to traverse each DC component. The length of the sliding window is preferably 10ms, and the step size of the sliding window is selected between 1 and 5ms.

[0034] After traversing each DC component, several sliding window data blocks are formed. For each sliding window data block, the microprocessor of each measurement port independently maintains a buffer. This buffer is a circular queue structure, storing the data from the N most recent consecutive sliding window data blocks (each window has a fixed length of 10ms). and The extreme value data, That is: the maximum value of the DC component of the d-axis. Minimum value of the DC component of the d-axis The maximum value of the DC component on the q-axis Minimum value of the DC component along the q-axis And the corresponding time tag.

[0035] In the cache, The oldest sliding window data block; each time a newest sliding window data block is passed... Update the cache once: use the latest sliding window data block. Cover the original ,Original cover ,...,Original Recorded as the earliest sliding window data block in history It is discarded after calculation.

[0036] S3. Calculate the target difference between the three-phase current data in the latest sliding window data block and the three-phase current data in the earliest historical sliding window data block in the buffer. In a preferred embodiment, the target difference between the three-phase current data in the latest sliding window data block and the three-phase current data in the oldest historical sliding window data block in the calculation cache includes: Based on the maximum and minimum values ​​of each DC component in the latest sliding window data block in the buffer, the first mean value of each DC component in the latest sliding window data block is calculated. The second mean of each DC component in the earliest historical sliding window data block is calculated based on the maximum and minimum values ​​of each DC component in the earliest historical sliding window data block. Calculate the first difference between the first mean of each DC component and the second mean of each DC component, and take the first difference with the largest value as the target difference.

[0037] Specifically, based on the maximum and minimum values ​​of each DC component within the latest sliding window data block in the buffer, the first mean value of each DC component within the latest sliding window data block is calculated. The specific calculation formula is as follows: ; ; In the formula, This represents the first mean of the DC component along the d-axis within the latest sliding window data block; This represents the maximum value of the DC component of the d-axis within the latest sliding window data block; This represents the minimum value of the DC component of the d-axis within the latest sliding window data block; This represents the first mean of the q-axis DC component within the latest sliding window data block; This represents the maximum value of the q-axis DC component within the latest sliding window data block; This represents the maximum value of the q-axis DC component within the latest sliding window data block; Specifically, based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer, the second mean value of each DC component within the earliest historical sliding window data block is calculated. The specific calculation formula is as follows: ; ; In the formula, This represents the second mean of the DC component along the d-axis within the earliest historical sliding window data block. This represents the maximum value of the DC component of the d-axis within the earliest historical sliding window data block; This represents the minimum value of the DC component of the d-axis within the earliest historical sliding window data block; This represents the second mean of the DC component of the q-axis within the earliest historical sliding window data block; This represents the maximum value of the DC component of the q-axis within the earliest historical sliding window data block; This represents the maximum value of the DC component of the q-axis within the earliest historical sliding window data block; Then, the first difference between the first mean of each DC component and the second mean of each DC component is calculated, and the first difference with the largest value is taken as the target difference. The specific calculation formula is as follows: .

[0038] S4. When the effective value of the zero-sequence voltage exceeds the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is a single-phase grounding fault in the distribution network. The transient change amplitude of each measurement port at the time of the single-phase grounding fault is calculated. The measurement port whose transient change amplitude exceeds the preset third threshold is taken as the single-phase grounding fault measurement point. Based on all the single-phase grounding fault measurement points, the fault section is determined. To illustrate, the collected zero-sequence voltage is a sequence of instantaneous zero-sequence voltage values. Therefore, the sliding window root mean square algorithm is used to calculate its effective value. The specific calculation formula is as follows: ; In the formula, The effective value of the zero-sequence voltage at the current moment, each Intervals are one sliding step; The zero-sequence voltage (instantaneous value) was collected. This represents the number of sampling points within one power frequency cycle.

[0039] Specifically, when the effective value of the zero-sequence voltage exceeds a preset first threshold and all target differences are detected... Not exceeding the preset second threshold When a single-phase ground fault is detected in the distribution network, the specific formula is as follows: ; In the formula, This indicates the sliding step size, which can represent the moment of failure; This represents the first threshold, which is generally taken as 5% to 10% of the phase voltage for low-current grounding systems.

[0040] In a preferred embodiment, the extreme values ​​include a maximum value and a minimum value; The calculation of the transient amplitude of each measurement port at the moment of occurrence of a single-phase ground fault, and the determination of the measurement port whose transient amplitude exceeds a preset third threshold as the single-phase ground fault measurement point, includes: All time window data blocks at the moment a single-phase ground fault occurs are used as reference sliding window data blocks; each reference sliding window data block corresponds to a measurement port; Extract the mean value of each DC component in the preceding sliding window data block of the reference sliding window data block, and extract the maximum value of each DC component in the following reference sliding window data block. Calculate the difference between the maximum value and the corresponding mean value of each DC component, and use it as the second difference value; For each measurement port, the second largest difference is taken as the transient change amplitude of the current measurement port; Measurement ports whose transient amplitude exceeds the preset third threshold are identified as single-phase grounding fault measurement points; Specifically, all time window data blocks at the moment a single-phase ground fault occurs are used as reference sliding window data blocks. It should be noted that each reference sliding window data block corresponds to a measurement port. Then, the mean value of each DC component in the previous sliding window data block is extracted, that is, the mean value of the d-axis DC component in the previous sliding window data block. and the mean of the DC component along the q-axis The specific calculation formula is as follows: ; ; In the formula, This indicates the maximum value of the d-axis DC component within the previous sliding window data block of the reference sliding window data block; This represents the minimum value of the d-axis DC component within the previous sliding window data block of the reference sliding window data block; This indicates the maximum value of the q-axis DC component within the previous sliding window data block of the reference sliding window data block; This indicates the maximum value of the q-axis DC component within the previous sliding window data block of the reference sliding window data block.

[0041] Then, the maximum value of the d-axis DC component is extracted from the next reference sliding window data block of the reference sliding window data block. and the maximum value of the DC component on the q-axis ; Calculate the difference between the maximum value and the corresponding mean value of each DC component, and use this difference as the second difference. The second difference with the largest value is taken as the transient amplitude of the current measurement port. The specific calculation formula is as follows: ; Transient mutation amplitude Exceeding the preset third threshold The measurement port was determined to be a single-phase grounding fault measurement point.

[0042] S5. When any target difference is detected to exceed the preset second threshold, it is determined that there is a phase-to-phase short circuit fault in the distribution network. The measurement port where the target difference exceeds the preset second threshold is taken as the single-phase grounding fault measurement point, and the fault section is determined based on all the single-phase grounding fault measurement points. Specifically, upon identifying any target difference Exceeding the preset second threshold When a phase-to-phase short-circuit fault is detected in the distribution network, the measurement port whose target difference exceeds the preset second threshold is designated as the single-phase grounding fault measurement point. This allows for the rapid location of the measurement port that responds first to the short-circuit disturbance, providing crucial location information for subsequent section location and type differentiation of phase-to-phase short-circuit faults.

[0043] As an illustration, since all single-phase ground fault measurement points have been identified, and these measurement points have the characteristics of operating sequentially along the fault current path and being closer to the fault point, it is necessary to determine the fault section in the distribution network based on the distribution of single-phase ground fault measurement points. It should be noted that distribution networks typically have a radial topology, with current flowing from the power source to the load side. Fault signals propagate unidirectionally along the lines. Therefore, the final fault section can be located based on the upstream and downstream relationships of the fault measurement point.

[0044] In a preferred embodiment, determining the fault section based on all single-phase ground fault measurement points includes: When it is determined that there is only one single-phase ground fault measurement point, the section located downstream of the single-phase ground fault measurement point is taken as the fault section; When it is determined that there are two or more single-phase ground fault measurement points, the section downstream of the downstreamst single-phase ground fault measurement point is taken as the fault section. Specifically, if there is only a single-phase ground fault measurement point M, the section downstream of the single-phase ground fault measurement point is taken as the fault section, the fault section is located, and the longitudinal differential protection is allowed to operate. When it is determined that there are two single-phase ground fault measurement points, assuming they are single-phase ground fault measurement point M and single-phase ground fault measurement point N, the section located downstream of single-phase ground fault measurement point N is taken as the fault section, indicating that the fault point is located in the downstream area of ​​port N, and the longitudinal differential protection is blocked. When it is determined that there are more than two single-phase ground fault measurement points, let's assume they are single-phase ground fault measurement point M, single-phase ground fault measurement point N1 and single-phase ground fault measurement point N2. When the longitudinal differential signal of all downstream ports is 0, the section downstream of the single-phase ground fault measurement point located at the downstreammost point is taken as the fault section and the longitudinal differential protection is blocked.

[0045] In a preferred embodiment, after determining that a phase-to-phase short-circuit fault exists in the distribution network and identifying the fault section based on all single-phase grounding fault measurement points, the method further includes: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network. Specifically, the peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. The specific calculation formula is as follows: ; Subsequently, when it is determined that the peak-to-peak value is less than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. This type of fault is a symmetrical fault, which only generates a positive-sequence component, and the zero-sequence voltage does not increase significantly and the current fluctuation amplitude is small. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. This type of fault is an asymmetrical fault, with a significant negative sequence component, and the current fluctuates violently but does not generate a significant zero-sequence voltage. When the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds the preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network. This type of fault includes both asymmetrical fault characteristics and grounding characteristics, with large current fluctuations and a significant increase in zero-sequence voltage. Finally, the corresponding fault type is output, the longitudinal differential protection is activated, and the fault isolation is completed.

[0046] In a preferred embodiment, the distribution network fault detection method based on current transient characteristics further includes: When the effective value of the zero-sequence voltage exceeds the preset first threshold, a first fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. When any mean value is detected to exceed the preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. Specifically, when the effective value of the zero-sequence voltage exceeds the preset first threshold, a first fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. This signal is a ground fault initiation signal, which is used to notify all port systems that a ground fault has occurred, and to initiate the transient change amplitude calculation, fault measurement point identification and section judgment logic of each port, providing a unified trigger command for the longitudinal differential judgment of ground faults.

[0047] Specifically, when any target difference is detected to exceed the preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. This signal is a phase-to-phase short-circuit fault initiation signal, which is used to notify all ports in the network that a short-circuit disturbance has occurred, and to initiate the dq component extreme value extraction, peak-to-peak value calculation and fault type subdivision logic of each port, so as to provide a unified triggering basis for the longitudinal differential protection action of phase-to-phase short circuit.

[0048] S6. When it is found that the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is no fault in the distribution network. Specifically, the absence of a significant increase in zero-sequence voltage indicates that no grounding fault has occurred in the system, and the fact that the differences between each target value do not exceed the preset second threshold indicates that there is no significant short-circuit disturbance in the line. Both conditions being met together can rule out the occurrence of a fault, and therefore it is determined that the current distribution network is in normal operation.

[0049] To better illustrate this application, a system as follows was constructed: Figure 2 The simulation model of the 10kV low-current grounding system distribution network shown is as follows: If the simulation analysis is of a resonant grounding system, switch S1 is kept closed, the arc suppression coil damping resistance is 10Ω, and the overcompensation degree is 10%; if the simulation analysis is of a neutral point ungrounded system, switch S1 is kept open, and all cable lines are replaced with overhead lines of equal length. Among them, L1-L2 are long overhead lines, L3 is a cable-overhead hybrid line, L4 is a cable line, and the feeder parameters are shown in Table 1.

[0050] Table 1 Line Parameters Figure 2 In the diagram, Ld1~Ld16 are three-phase symmetrical loads connected at the end of each line segment, with parameters shown in Table 2. The neutral point voltage measuring device is installed between the grounding transformer Z and the switch S1, and can measure the zero-sequence voltage of the system. M1~M16 are three-phase current measuring nodes, which can measure and upload the three-phase current waveform data flowing through circuit breakers CB1~16. DG1~3 represent the installation locations of distributed power sources. Taking the fault occurring at 50% of section L3 (11-12), they represent the busbar, upstream of the fault, and downstream of the fault connected to the distributed power source, respectively. The sampling frequency for voltage and current measurements is 4.8kHz.

[0051] Table 2 Line Load Parameters Taking a short-circuit fault occurring at 50% of section 11-12 in L3 of a neutral-point ungrounded system as an example, the fault time is 0.06s, and the initial fault angle is 45°. The fault types and settings are as follows: single-phase ground fault (AG, grounding resistance 300Ω), two-phase short-circuit fault (AB, short-circuit resistance 20Ω), two-phase short-circuit ground fault (ABG, short-circuit resistance 20Ω, grounding resistance 20Ω), and three-phase short-circuit fault (ABC, short-circuit resistance 20Ω). Since this paper selects the most obvious dq component eigenvalue, and the d-axis characteristic is most obvious at the initial fault angle, only the d-axis current is shown. The d-axis current waveform of the faulted line at this time is as follows. Figure 3 As shown.

[0052] Depend on Figure 3 It can be observed that the d-axis current waveform of the faulty line has obvious characteristics at 60ms after the fault, with significant differences in the mean value of the d-axis current before and after the fault, transient change amplitude, and peak-to-peak value after the fault: See Figure 3 (a)-3(c), for single-phase ground faults: The transient amplitude of ports M10 and M11 is greater than the third threshold, the longitudinal differential signal of M10 and M11 is 1, and the longitudinal differential protection of section 10-11 is blocked; while the transient amplitude of port M12 is less than the third threshold, the longitudinal differential signal of M12 is 0, and the longitudinal differential protection of section 11-12 is allowed to operate; the fault section location of the single-phase ground fault is completed; See Figure 3 (d)- Figure 3 (l), Figure 3 (d)- Figure 3 (f) shows the current waveform of a two-phase short-circuit ground fault. Figure 3 (g)- Figure 3 (i) shows the current waveform during a two-phase short-circuit fault. Figure 3 (j)- Figure 3 (l) shows the current waveform of a three-phase short-circuit fault.

[0053] The difference in average current before and after the fault at ports M10 and M11 is greater than the second threshold, so the longitudinal differential signal of M10 and M11 is 1, and the longitudinal differential protection of section 10-11 is blocked; while the difference in average current before and after the fault at port M12 is less than the second threshold, so the longitudinal differential signal of M12 is 0, and the longitudinal differential protection of section 11-12 is allowed to operate; the fault section location for the phase-to-phase short circuit fault is completed. For fault type identification of phase-to-phase short circuit faults: Three-phase short circuit faults exhibit a relatively stable waveform with very small peak-to-peak values ​​after the fault. A three-phase short circuit fault can be identified when the peak-to-peak value after the fault is less than the preset peak-to-peak value distinction threshold. Two-phase faults exhibit a waveform with a large 100Hz component and a large peak-to-peak value after the fault. A two-phase fault can be identified when the peak-to-peak value after the fault is greater than the preset peak-to-peak value distinction threshold. The d-axis current waveforms of two-phase short-circuit-to-ground faults and two-phase short circuit faults are basically the same. Identification can be completed based on whether a zero-sequence voltage initiation signal is received at the port. If a zero-sequence voltage initiation signal of 1 is received, it is a two-phase short-circuit-to-ground fault; otherwise, it is a two-phase short circuit fault. Accurate identification of the fault type of phase-to-phase short circuit faults is achieved.

[0054] To more clearly demonstrate the protection action logic of this method, the timing diagram of the protection action logic for a three-phase short-circuit fault is as follows: Figures 4-6 As shown, the horizontal dashed line represents the set threshold, and the vertical dashed line represents the time when the fault occurs.

[0055] Depend on Figures 4-6 It can be observed that the mean difference characteristic during a three-phase short-circuit fault is quite significant. (See [reference]) Figure 4 (a)- Figure 4 (b) The mean difference between the upstream ports M10 and M11 before and after the fault is approximately 300A, which is greater than the set threshold (100A). The dq component of the port current then initiates signal transmission. (See also...) Figure 4 (c) The mean difference between the fault and the fault value of the downstream port M12 before and after the fault is about -5A. The absolute value is 5A, which is less than the set threshold (100A). The current dq component of the port does not start transmitting.

[0056] See Figure 5 (a)- Figure 5 (c) Since the current dq component is used to start the signal, it can be determined that a phase-to-phase short circuit fault has occurred. The current dq component is used as the longitudinal differential signal. The longitudinal differential signals at both ends of circuit breaker CB10 are 1, so it does not operate; the longitudinal differential signals at both ends of circuit breaker CB11 are 1 and 0, so it operates; the longitudinal differential signals at both ends of circuit breaker CB12 are 0, so it does not operate.

[0057] See Figure 6 (a) After the fault occurs, the peak-to-peak value remains near 0, far below the set threshold (100A). This is because the port is located upstream of the fault point, and the transient characteristics of the fault current are not reflected here; therefore, the fluctuation of the dq component is extremely small. See also Figure 6(b) After the fault occurred, the peak-to-peak value showed a small step change, but remained well below the set threshold (100A). This indicates that a fault disturbance was detected at this port. However, since a three-phase short circuit is a symmetrical fault, there is almost no negative sequence component in the fault current; therefore, the fluctuation of the dq component (peak-to-peak value) is very small, consistent with the characteristics of a three-phase short circuit. See also Figure 6 (c) After the fault occurred, the peak-to-peak value remained near 0 and did not exceed the set threshold (100A). This is because the port is located downstream of the fault point and no fault current was detected, so the dq component did not fluctuate significantly.

[0058] See Figure 7 This invention provides a distribution network fault detection device based on current transient characteristics, comprising: a data acquisition module, a data identification module, a calculation module, a first detection module, a second detection module, and a third detection module. The data acquisition module is used to acquire the zero-sequence voltage at the neutral point port of the distribution network and the three-phase current data at each measurement port. The data recognition module is used to traverse the three-phase current data through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. The calculation module is used to calculate the target difference between the three-phase current data in the latest sliding window data block in the buffer and the three-phase current data in the earliest historical sliding window data block. The first detection module is used to determine that there is a single-phase grounding fault in the distribution network when the effective value of the zero-sequence voltage exceeds a preset first threshold and all target differences do not exceed a preset second threshold, calculate the transient change amplitude of each measurement port at the time of the single-phase grounding fault, and take the measurement port whose transient change amplitude exceeds a preset third threshold as the single-phase grounding fault measurement point. The second detection module is used to determine that there is a phase-to-phase short circuit fault in the distribution network when any target difference exceeds a preset second threshold, and to use the measurement port where the target difference exceeds the preset second threshold as a single-phase grounding fault measurement point. The third detection module is used to determine that there is no fault in the distribution network when the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold.

[0059] In a preferred embodiment, the data identification module is specifically used for: Park transformation is performed on all the collected three-phase current data to obtain the DC component corresponding to each three-phase current data. The DC component includes the d-axis DC component and the q-axis DC component. A preset sliding window is invoked to traverse each DC component, and N sliding window data blocks are updated and stored in the buffer in real time according to the chronological order; wherein, each sliding window data block includes the maximum and minimum values ​​of each DC component; N is a positive integer.

[0060] In a preferred embodiment, the computing module is specifically used for: Based on the maximum and minimum values ​​of each DC component in the latest sliding window data block in the buffer, the first mean value of each DC component in the latest sliding window data block is calculated. The second mean of each DC component in the earliest historical sliding window data block is calculated based on the maximum and minimum values ​​of each DC component in the earliest historical sliding window data block. Calculate the first difference between the first mean of each DC component and the second mean of each DC component, and take the first difference with the largest value as the target difference.

[0061] In a preferred embodiment, the first detection module is specifically used for: All time window data blocks at the moment a single-phase ground fault occurs are used as reference sliding window data blocks; each reference sliding window data block corresponds to a measurement port; Extract the mean value of each DC component in the preceding sliding window data block of the reference sliding window data block, and extract the maximum value of each DC component in the following reference sliding window data block. Calculate the difference between the maximum value and the corresponding mean value of each DC component, and use it as the second difference value; For each measurement port, the second largest difference is taken as the transient change amplitude of the current measurement port; Measurement ports whose transient amplitude exceeds the preset third threshold are identified as single-phase grounding fault measurement points.

[0062] In a preferred embodiment, the first detection module is specifically used for: When it is determined that there is only one single-phase ground fault measurement point, the section located downstream of the single-phase ground fault measurement point is taken as the fault section; When two or more single-phase ground fault measurement points are identified, the section downstream of the downstreamst single-phase ground fault measurement point is taken as the fault section.

[0063] In a preferred embodiment, the second detection module is specifically used for: When it is determined that there is only one single-phase ground fault measurement point, the section located downstream of the single-phase ground fault measurement point is taken as the fault section; When two or more single-phase ground fault measurement points are identified, the section downstream of the downstreamst single-phase ground fault measurement point is taken as the fault section.

[0064] In a preferred embodiment, the second detection module is further configured to: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network.

[0065] See Figure 8 In a preferred embodiment, the power distribution network fault detection device based on current transient characteristics further includes: a signal transmission module; The signal transmitting module is used to send a first fault characteristic signal to the neutral point port and each measurement port of the distribution network when it is detected that the effective value of the zero-sequence voltage exceeds a preset first threshold. When any mean value is detected to exceed a preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port.

[0066] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for detecting faults in a distribution network based on transient current characteristics, characterized in that, include: Collect zero-sequence voltage at the neutral point port of the distribution network and three-phase current data at each measurement port; The three-phase current data is traversed through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. Calculate the target difference between the three-phase current data in the latest sliding window data block in the buffer and the three-phase current data in the earliest historical sliding window data block. When the effective value of the zero-sequence voltage exceeds the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is a single-phase grounding fault in the distribution network. The transient change amplitude of each measurement port at the time of the single-phase grounding fault is calculated. The measurement port whose transient change amplitude exceeds the preset third threshold is taken as the single-phase grounding fault measurement point. Based on all the single-phase grounding fault measurement points, the fault section is determined. When any target difference is detected to exceed the preset second threshold, it is determined that there is a phase-to-phase short-circuit fault in the distribution network. The measurement port where the target difference exceeds the preset second threshold is taken as the single-phase grounding fault measurement point, and the fault section is determined based on all the single-phase grounding fault measurement points. When the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold, it is determined that there is no fault in the distribution network.

2. The distribution network fault detection method based on current transient characteristics as described in claim 1, characterized in that, The process involves traversing the three-phase current data through a preset sliding window. During this traversal, several sliding window data blocks are formed and stored in a buffer in chronological order, including: Park transformation is performed on all the collected three-phase current data to obtain the DC component corresponding to each three-phase current data. The DC component includes the d-axis DC component and the q-axis DC component. A preset sliding window is invoked to traverse each DC component, and N sliding window data blocks are updated and stored in the buffer in real time according to the chronological order; wherein, each sliding window data block includes the maximum and minimum values ​​of each DC component; N is a positive integer.

3. The distribution network fault detection method based on current transient characteristics as described in claim 2, characterized in that, The target difference between the three-phase current data in the latest sliding window data block and the three-phase current data in the oldest historical sliding window data block in the calculation buffer includes: Based on the maximum and minimum values ​​of each DC component in the latest sliding window data block in the buffer, the first mean value of each DC component in the latest sliding window data block is calculated. The second mean of each DC component in the earliest historical sliding window data block is calculated based on the maximum and minimum values ​​of each DC component in the earliest historical sliding window data block. Calculate the first difference between the first mean of each DC component and the second mean of each DC component, and take the first difference with the largest value as the target difference.

4. The distribution network fault detection method based on current transient characteristics as described in claim 3, characterized in that, The extreme values ​​include the maximum value and the minimum value; The calculation of the transient amplitude of each measurement port at the moment of occurrence of a single-phase ground fault, and the determination of the measurement port whose transient amplitude exceeds a preset third threshold as the single-phase ground fault measurement point, includes: All time window data blocks at the moment a single-phase ground fault occurs are used as reference sliding window data blocks; each reference sliding window data block corresponds to a measurement port; Extract the mean value of each DC component in the preceding sliding window data block of the reference sliding window data block, and extract the maximum value of each DC component in the following reference sliding window data block. Calculate the difference between the maximum value and the corresponding mean value of each DC component, and use it as the second difference value; For each measurement port, the second largest difference is taken as the transient change amplitude of the current measurement port; Measurement ports whose transient amplitude exceeds the preset third threshold are identified as single-phase grounding fault measurement points.

5. The distribution network fault detection method based on current transient characteristics as described in claim 4, characterized in that, The process of determining the fault section based on all single-phase ground fault measurement points includes: When it is determined that there is only one single-phase ground fault measurement point, the section located downstream of the single-phase ground fault measurement point is taken as the fault section; When two or more single-phase ground fault measurement points are identified, the section downstream of the downstreamst single-phase ground fault measurement point is taken as the fault section.

6. The distribution network fault detection method based on current transient characteristics as described in claim 5, characterized in that, After determining that a phase-to-phase short-circuit fault exists in the distribution network and identifying the fault section based on all single-phase grounding fault measurement points, the process also includes: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network.

7. The distribution network fault detection method based on current transient characteristics as described in claim 1, characterized in that, Also includes: When the effective value of the zero-sequence voltage exceeds the preset first threshold, a first fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port. When any mean value is detected to exceed a preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port.

8. A distribution network fault detection device based on current transient characteristics, characterized in that, include: The system comprises a data acquisition module, a data recognition module, a calculation module, a first detection module, a second detection module, and a third detection module. The data acquisition module is used to acquire the zero-sequence voltage at the neutral point port of the distribution network and the three-phase current data at each measurement port. The data recognition module is used to traverse the three-phase current data through a preset sliding window. During the traversal, several sliding window data blocks are formed and stored in the buffer area in chronological order. The calculation module is used to calculate the target difference between the three-phase current data in the latest sliding window data block in the buffer and the three-phase current data in the earliest historical sliding window data block. The first detection module is used to determine that there is a single-phase grounding fault in the distribution network when the effective value of the zero-sequence voltage exceeds a preset first threshold and all target differences do not exceed a preset second threshold, calculate the transient change amplitude of each measurement port at the time of the single-phase grounding fault, take the measurement port whose transient change amplitude exceeds a preset third threshold as the single-phase grounding fault measurement point, and determine the fault section based on all the single-phase grounding fault measurement points. The second detection module is used to determine that there is a phase-to-phase short circuit fault in the distribution network when any target difference exceeds a preset second threshold, to take the measurement port where the target difference exceeds the preset second threshold as a single-phase ground fault measurement point, and to determine the fault section based on all single-phase ground fault measurement points; The third detection module is used to determine that there is no fault in the distribution network when the effective value of the zero-sequence voltage does not exceed the preset first threshold and all target differences do not exceed the preset second threshold.

9. The distribution network fault detection device based on current transient characteristics as described in claim 8, characterized in that, The second detection module is also used for: The peak-to-peak value is calculated based on the maximum and minimum values ​​of each DC component within the earliest historical sliding window data block in the buffer. When the peak-to-peak value is less than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed a preset first threshold, it is determined that there is a three-phase short-circuit fault in the distribution network. When it is determined that the peak-to-peak value is greater than the preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage does not exceed the preset first threshold, it is determined that there is a two-phase short-circuit fault in the distribution network. When the peak-to-peak value is greater than a preset peak-to-peak value distinction threshold and the effective value of the zero-sequence voltage exceeds a preset first threshold, it is determined that there is a two-phase short-circuit ground fault in the distribution network.

10. The distribution network fault detection device based on current transient characteristics as described in claim 8, characterized in that, Also includes: Signal transmitting module; The signal transmitting module is used to send a first fault characteristic signal to the neutral point port and each measurement port of the distribution network when it is detected that the effective value of the zero-sequence voltage exceeds a preset first threshold. When any mean value is detected to exceed a preset second threshold, a second fault characteristic signal is sent to the neutral point port of the distribution network and each measurement port.

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