Substation single-phase earth fault line selection discrimination method based on zero-sequence current reference value

Abstract

The invention discloses a transformer station single-phase earth fault line selection discrimination method based on a zero sequence current reference value, and the method comprises the steps: collecting the zero sequence current of all switches of a non-fault feeder line and the zero sequence current of a downstream switch of a fault point in a fault feeder line after a single-phase earth fault occurs, and dynamically updating the zero sequence current reference value of the corresponding switch; detecting the zero-sequence current value of each switch in real time, calculating the break variable of the zero-sequence current value and the corresponding zero-sequence current reference value, and judging the feeder line where the switch with the maximum break variable is located as a fault feeder line; traversing adjacent switch pairs of the fault feeder from the power supply side to the load side, and calculating the ratio of the zero-sequence current break variable of the upstream switch to the zero-sequence current break variable of the downstream switch; when the ratio is greater than or equal to a set threshold value, determining that a fault is located between the two adjacent switches; and if the ratio of all adjacent switch pairs is smaller than a set threshold value, determining that the fault is located at the tail end of the line.

Description

Technical Field

[0001] This invention relates to the field of power system fault detection technology, and in particular to a method for identifying single-phase grounding faults in substations based on zero-sequence current reference values. Background Technology

[0002] For the low-current grounding systems commonly used in current distribution networks (including ungrounded neutral points and grounding via arc suppression coils), the characteristic is that when a single-phase ground fault occurs, the fault current is relatively small, and the system can operate with the fault for 1-2 hours, buying time for fault diagnosis. However, this characteristic also leads to weak fault characteristics, making fault location one of the core challenges in distribution network operation and maintenance. Statistics show that single-phase ground faults account for more than 80% of short-circuit faults in distribution networks, making rapid and accurate identification of faulty lines crucial for ensuring power supply reliability and equipment safety.

[0003] Current mainstream methods for single-phase grounding fault location can be broadly categorized into two types: transient quantity methods and steady-state quantity methods, each with significant technical bottlenecks. Transient quantity methods locate faults by capturing high-frequency transient zero-sequence current signals (such as abrupt changes and harmonic components) generated at the moment of the fault. They often combine wavelet transform, variational mode decomposition, and other signal processing techniques to extract transient features, and utilize machine learning models such as support vector machines and neural networks for pattern recognition. Theoretically, this method can utilize the rich transient information in the early stages of a fault to improve sensitivity, but in practical applications, it is limited by three main problems: first, the distribution network contains numerous power electronic devices and nonlinear loads, whose noise can easily mask weak transient fault features; second, the computational complexity of signal processing and feature extraction is high, making it difficult to meet real-time requirements; and third, the transient signal energy attenuates drastically during high-resistance grounding (such as arc grounding or tree branch splicing), leading to feature extraction failure.

[0004] The steady-state quantitative method selects lines based on the steady-state amplitude change of zero-sequence current before and after a fault. Its core logic is that "the amplitude of the zero-sequence current on the faulty line is greater than that on the non-faulty line." This method requires no complex signal processing, has low implementation costs, and was once widely used in engineering practice. However, the steady-state quantitative method also has significant limitations: on the one hand, during normal operation of the distribution network, the zero-sequence current is affected by load fluctuations and line parameter imbalances, resulting in poor amplitude stability and easily leading to misjudgments of "abnormally increased amplitude on non-faulty lines"; on the other hand, during high-resistance grounding, the fault current is only slightly greater than the normal operating zero-sequence current, and the amplitude difference is not significant, making it difficult to distinguish using traditional amplitude comparison methods; furthermore, the method relies on manually set amplitude thresholds, but these thresholds vary greatly under different power grid structures and operating modes, resulting in insufficient universality and further reducing the reliability of the judgment.

[0005] In recent years, to overcome the limitations of single methods, scholars have attempted to integrate multi-feature joint criteria of transient and steady-state signals and introduce intelligent algorithms such as deep learning to enhance feature mining capabilities. However, the fault scenarios of low-current grounding systems are complex (such as high-resistance grounding, arc grounding, and intermittent grounding), and the transient and steady-state characteristics of different fault types differ significantly. Simultaneously, the variable topology and flexible operation of distribution networks lead to a dispersed feature space, posing challenges to the effectiveness of multi-feature fusion and the algorithm's generalization ability. In summary, existing methods have not fully solved the problems of accuracy and real-time performance in single-phase grounding fault location in low-current grounding systems, necessitating new discrimination methods that are more resistant to interference and highly adaptable. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as load fluctuation interference with the reference current, weakened fault characteristics after arc suppression coil compensation, and the inability of traditional methods to simultaneously ensure the accuracy of line selection and section location, this invention provides a method and system for selecting the line and section of a single-phase grounding fault in a substation based on a dynamic zero-sequence current reference library. Its core innovative design is as follows:

[0007] 1. Dynamic benchmark library construction mechanism:

[0008] After each ground fault, only the zero-sequence current of all switches on the non-faulty feeder and the downstream switch of the fault point on the faulty feeder is collected, and the baseline value is dynamically updated by arithmetic averaging. This design eliminates the interference of load growth and grid changes, so that the sudden changes only reflect the actual fault disturbances.

[0009] 2. Selection logic for mutation ratio:

[0010] During fault segment selection, the ratio of upstream to downstream abrupt changes in the faulty feeder's adjacent switches is calculated. When this ratio exceeds a set threshold (typically 3), the fault is determined to be located between the two switches; otherwise, it is located at the end of the line. This method overcomes the sensitivity limitations of traditional steady-state methods, achieving meter-level fault segment location (accurately locating the fault point of an overhead line to the section between switches, with a measured ratio of 156 times; even in the arc suppression coil scenario, it still maintains a significant difference of 88 times).

[0011] 3. Arc suppression coil application compatibility:

[0012] By determining the ratio of dynamic benchmark value to sudden change, the problem of weakened fault characteristics after arc suppression coil compensation is effectively solved. After compensation, the sudden change at the beginning of the faulty feeder is still significantly greater than that of the non-faulty line (the measured sudden change at the beginning of the cable network is 2.64A, while that of the non-faulty line is 0.01A), and the ratio of sudden changes between adjacent switches maintains an ultra-high threshold characteristic.

[0013] 4. High-efficiency computing architecture:

[0014] The benchmark update and mutation ratio calculation based on arithmetic mean eliminate the need for complex operations such as wavelet decomposition for transient feature extraction, significantly improving real-time performance.

[0015] The present invention specifically adopts the following technical solution:

[0016] A method for selecting and identifying single-phase ground faults in substations based on zero-sequence current reference values ​​includes:

[0017] After a single-phase ground fault occurs, the zero-sequence current of all switches in the non-faulty feeder and the zero-sequence current of the downstream switch of the fault point in the faulty feeder are collected, and the zero-sequence current reference value of the corresponding switch is dynamically updated.

[0018] Real-time detection of zero-sequence current value of each switch, calculation of the abrupt change of its value with the corresponding zero-sequence current reference value, and determination of the feeder where the switch with the largest abrupt change is located as the faulty feeder.

[0019] Traverse the adjacent switch pairs of the fault feeder from the power supply side to the load side, and calculate the ratio of the zero-sequence current mutation of the upstream switch to the zero-sequence current mutation of the downstream switch.

[0020] When the ratio is greater than or equal to a set threshold, the fault is determined to be located between the two adjacent switches;

[0021] If the ratio of all adjacent switch pairs is less than the set threshold, the fault is determined to be located at the end of the line.

[0022] Furthermore, when dynamically updating the zero-sequence current reference value, only two types of data sources are used:

[0023] Zero-sequence current of all switches on the non-faulty feeder;

[0024] Zero-sequence current of all switches in the fault feeder located in the direction from the fault point to the load side.

[0025] Furthermore, the dynamic update employs the arithmetic mean method:

[0026] Add the currently collected valid zero-sequence current value to the historical valid dataset;

[0027] The arithmetic mean of the dataset is used as the updated baseline.

[0028] Furthermore, the mutation amount is calculated using absolute differences:

[0029] ΔI=∣I Kij - I Kij-base |

[0030] Where ΔI is the zero-sequence current abrupt change; I Kij I represents the real-time value of the zero-sequence current of the j-th switch on the i-th feeder; Kij-baseThis represents the zero-sequence current reference value of the j-th switch on the i-th feeder.

[0031] Furthermore, the set threshold is 3.

[0032] Furthermore, the criteria for defining the downstream switch of the fault point are as follows:

[0033] All switches from the fault point to the load side;

[0034] Zero-sequence current data from the upstream switch of the fault point is not used for baseline value updates.

[0035] Furthermore, when applied to arc suppression coil grounding systems: the ratio of sudden changes in the values ​​of adjacent switches at the fault point still satisfies ΔI. 上游 / ΔI 下游 ≥3.

[0036] Furthermore, the order of traversing adjacent switches is as follows: starting from the switch at the beginning of the feeder, compare adjacent switch pairs step by step towards the load side.

[0037] And, a substation single-phase ground fault location and identification system based on zero-sequence current reference value, comprising:

[0038] The data acquisition module is used to collect the zero-sequence current of all switches in the non-faulty feeder and the zero-sequence current of the downstream switch of the fault point in the faulty feeder after a single-phase ground fault occurs.

[0039] The reference value update module is connected to the data acquisition module and is used to dynamically update the zero-sequence current reference value of each switch.

[0040] The fault selection module is used to calculate the abrupt change between the real-time value and the reference value of the zero-sequence current of each switch, and to determine the feeder where the switch with the largest abrupt change is located as the faulty feeder.

[0041] The fault segment selection module is used to traverse the adjacent switch pairs of the fault feeder, calculate the ratio of the zero-sequence current change of the upstream switch to the downstream switch, locate the fault section when the ratio is greater than or equal to the set threshold, otherwise determine that the fault is located at the end of the line.

[0042] A topology database stores the upstream and downstream connection relationships of feeder switches.

[0043] Furthermore, a substation fault handling device includes a processor and a memory, wherein the memory stores a computer program that, when executed by the processor, implements the steps of the method described above.

[0044] And, a computer device including a processor and a memory storing a computer program, characterized in that, when the program is executed by the processor, it implements the steps of the method described above.

[0045] A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the steps of the method described above.

[0046] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects:

[0047] Solving load fluctuation interference problems:

[0048] By dynamically updating the benchmark library containing only non-faulty feeders and downstream switch data of faulty feeders, combined with the arithmetic average algorithm, the interference of load changes and grid structure adjustments on the zero-sequence current benchmark value is eliminated, so that the calculation of abrupt changes only reflects the actual fault disturbances.

[0049] Breakthrough in arc suppression coil application scenarios:

[0050] By utilizing the characteristic that the sudden change in the switch at the head end of the faulty feeder is significantly greater than that of the non-faulty line, and the judgment logic that the ratio of the sudden changes in adjacent switches exceeds the threshold, the problem of weakened fault characteristics after arc suppression coil compensation is overcome, and reliable positioning under the compensation system is achieved.

[0051] Improve the accuracy of fault location:

[0052] By adopting the threshold determination mechanism of the ratio of upstream mutation amount to downstream mutation amount, the traditional steady-state method can only select the line but cannot locate the section, and accurately locate the fault section (such as between switches or at the end of the line), avoiding the defect of poor universality of manual threshold.

[0053] Optimize computational efficiency and real-time performance:

[0054] By updating the baseline value based on the arithmetic mean and calculating the absolute value of the mutation, the complex calculations such as wavelet decomposition and feature extraction required by the transient method are avoided, significantly reducing the processing time and meeting the real-time fault handling needs of the distribution network.

[0055] Enhance system compatibility and robustness:

[0056] The topology order traversal mechanism ensures that faults near the power supply side are detected first, and the downstream switch has clearly defined rules to prevent data pollution, making the solution adaptable to complex distribution network structures such as overhead line / cable mixed connection and multiple branches.

[0057] It forms a closed-loop process of "dynamic benchmark maintenance → fault line selection → section location", taking into account the three core indicators of anti-interference, positioning accuracy and calculation efficiency, and provides a highly reliable solution for single-phase grounding faults in low current grounding systems. Attached Figure Description

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0059] Figure 1This is a schematic diagram of the technical route of an embodiment of the present invention.

[0060] Figure 2 This is a model diagram of a simulation example of an embodiment of the present invention.

[0061] Figure 3 This is an example diagram of a neutral point grounded system via an arc suppression coil, which is the application of this invention. Detailed Implementation

[0062] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0063] To make the features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings:

[0064] This invention proposes a novel method for identifying single-phase grounding faults in substations based on a zero-sequence current reference value. First, a reference zero-sequence current database for line switches is established. When a single-phase grounding fault occurs, the zero-sequence current flowing through each switch on the non-faulty feeder and the zero-sequence current of each switch downstream of the fault point on the faulty feeder are collected as the reference values ​​for the switch's zero-sequence current. After each grounding fault, the reference values ​​for the zero-sequence current of the aforementioned switches are updated by averaging. Fault assessment is divided into two stages. The first stage is fault selection. After a fault occurs, the real-time value of the zero-sequence current of each switch is compared with its corresponding reference value to calculate the abrupt change in the zero-sequence current. The feeder containing the switch with the largest abrupt change in zero-sequence current is the faulty feeder, thus completing the fault selection. The second stage is fault selection. After selecting the faulty feeder, all switches are traversed from upstream to downstream of the feeder. In two adjacent switches, the zero-sequence current change of the upstream switch is divided by the zero-sequence current change of the downstream switch. If the ratio is greater than a certain threshold (empirical value is 3), the fault is determined to be between these two switches. If the ratio is not satisfied when traversing all switches, the fault is determined to be at the end of the line.

[0065] The embodiments of this invention belong to the steady-state quantity method. To achieve the above objectives, the technical approach is as follows: Figure 1 As shown:

[0066] First, the substation terminal data acquisition system is used to obtain feeder current data. Specifically, after a ground fault occurs, a data call is triggered for all terminals, and the zero-sequence current values ​​of all line switches are saved to the database. The data is divided into the zero-sequence current of non-faulty feeder switches, and the zero-sequence current of the upstream and downstream switches of the faulty feeder.

[0067] Then, a baseline zero-sequence current database for substation lines is established. Specifically, this is calculated by collecting the zero-sequence current flowing through each switch on the non-faulty feeder and the zero-sequence current of the downstream switch on the faulty feeder when a single-phase ground fault occurs. These zero-sequence current baseline values ​​for each switch are used as the baseline values ​​for the zero-sequence current of each switch when a single-phase ground fault occurs. After each ground fault in the substation, the baseline values ​​for the zero-sequence current of the aforementioned switches are updated by averaging.

[0068] Next, single-phase grounding fault assessment is performed. The first stage is fault line selection, which involves comparing the real-time value of the zero-sequence current of each switch with its corresponding zero-sequence current reference value to calculate the abrupt change in the zero-sequence current. The feeder containing the switch with the largest abrupt change in zero-sequence current is the faulty feeder, thus completing the fault line selection.

[0069] The second stage is fault segment selection. After selecting the faulty feeder, all switches on the feeder are traversed from the power source side (upstream) to the load side (downstream) according to the topology. For any switch K, if the change in zero-sequence current of switch K is several times that of its adjacent downstream switch (the multiple can be set, with an empirical value of 3), then the area between switch K and its downstream adjacent switch is considered a fault zone; otherwise, the area is not considered a fault zone. If none of the switches satisfy the above multiple relationship, the fault is determined to be located at the end of the line, i.e., the end switch is the upper boundary of the fault zone. The basis for fault zone segment selection is as follows: the change in zero-sequence current measured by the upstream switch of the fault point on the faulty feeder is significant, while the change in zero-sequence current of the downstream switch is very small due to the current diversion effect at the fault point. Therefore, the difference in the multiple of the change in the zero-sequence current between two adjacent switches is greater than the empirical multiple, i.e., the fault zone is determined to be located between two adjacent switches.

[0070] Compared with existing technologies, the present invention has at least the following advantages:

[0071] 1) The fault selection process involves comparing the changes between the zero-sequence current value of each feeder switch and its zero-sequence current reference value during a fault. The sudden change in the non-faulty line switch is significantly smaller than that of the faulty line switch. When considering the influence of the arc suppression coil, the fault zero-sequence current after arc suppression coil compensation will show a significant sudden change regardless of whether it is greater than or less than the zero-sequence current reference value, which can also achieve fault selection.

[0072] 2) Traditional steady-state quantity methods are affected by load fluctuations and grid structure adjustments. The proposed method can update the zero-sequence current reference value after load adjustment so that the sudden change only reflects the fault disturbance, thereby eliminating the impact of load growth.

[0073] The following is a specific implementation example to further demonstrate and introduce the solution of the present invention:

[0074] Assume the substation has a three-feeder structure, with each feeder having a feeder switch K. i1 Feeder line sub-circuit switch K i2 With feeder line switch K i3 There are a total of 9 switches, such as Figure 2 As shown. The three-phase current values ​​measured by each feeder switch are input into the segment selection and line selection measurement module for processing to obtain the zero-sequence current value. All three feeders are equipped with three-phase symmetrical loads, with active power P = 10kW and reactive power Q. L =Q C =100var.

[0075] The line parameter settings simulate an overhead line. The positive sequence and zero sequence resistance, capacitance, and inductance per unit length are set as shown in Table 1.

[0076] Table 1 Line Parameter Settings

[0077] Line type Phase sequence Resistance Ω / km Inductance H / km Capacitance F / km Feeder length (km) Overhead lines Ascending order 0.01273 0.9337e-3 12.74e-9 40、40 Overhead lines Zero sequence 0.3864 4.1264e-3 7.751e-9 40

[0078] Next, the zero-sequence current reference value is determined. It is known that there are 9 switches in this model. Therefore, a single-phase ground fault is set in the line between each switch. The zero-sequence current value of the non-faulted line switch is collected and the zero-sequence current reference value is determined in combination with formula (1).

[0079] (1)

[0080] Where i represents the i-th feeder; j represents the j-th switch of a certain feeder; I Kij-base I represents the zero-sequence current reference value of the j-th switch of the i-th feeder; Kij-n This represents the zero-sequence current value of the non-faulty line switch; m represents the number of times a single-phase ground fault occurred on other feeders plus the number of times the fault point in the faulty feeder occurred in the upstream section of this switch.

[0081] The following is a brief description of the method for selecting the zero-sequence current value of a non-faulty feeder switch, assuming the fault occurs at feeder 1 switch K. 11 With K 12 Between these points, the zero-sequence currents of each switch are shown in Table 2. The zero-sequence currents collected from all switches on the non-faulty feeders (Line 2 and Line 3) can be used to calculate the zero-sequence current reference value. For the faulty line 1, switch K... 11Located upstream of the fault, the zero-sequence current it collects cannot be used as a reference value at this time. K 12 With K 12 Located downstream of the fault, the zero-sequence currents collected can all be used to calculate the reference value.

[0082] Table 2. Steady-state values ​​of zero-sequence current of each switch when feeder switch K1 section fails.

[0083] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 > Feeder 1 2.295231163 1.017236416 0.914052789 Feeder 2 1.149064683 1.019879681 0.916427927 Feeder 3 1.14616836 1.017429673 0.914607644

[0084] Assume the fault occurs at switch K on feeder 2. 23 Downstream, the zero-sequence currents of each switch are shown in Table 3. Since the fault point occurs at switch K... 21 K 22 With K 23 Downstream of these switches, the current flowing through them is not diverted at the fault point, and the zero-sequence current value is affected by the fault, so they cannot be used to calculate the zero-sequence current reference value.

[0085] Table 3 shows the steady-state values ​​of zero-sequence current for each switch during a fault in section K22 of the lower-level circuit.

[0086] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 > Feeder 1 1.164646978 1.033596601 0.928637334 Feeder 2 2.326354204 2.471404248 2.623406147 Feeder 3 1.161709131 1.031111172 0.926790446

[0087] In summary, after collecting the steady-state data of the zero-sequence current of each switch, the reference zero-sequence current values ​​of each switch are obtained by combining formula (1) as shown in Table 4.

[0088] Table 4 Zero-sequence current reference values

[0089] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 > Feeder 1 1.155728267 1.02455536 0.919965446 Feeder 2 1.155609253 1.024482606 0.919922761 Feeder 3 1.154752591 1.023849349 0.919506305

[0090] Based on the zero-sequence current reference value of each switch, single-phase fault assessment can be achieved. The first stage is to select the fault line. When a single-phase ground fault occurs in the substation, the real-time value of the zero-sequence current of the switch after the fault is collected. By comparing the real-time value of the zero-sequence current of each switch with its corresponding zero-sequence current reference value, the sudden change in the zero-sequence current is calculated, as shown in formula (2). The feeder where the switch with the largest zero-sequence sudden change is located is the fault feeder, thus completing the fault line selection.

[0091] (2)

[0092] Where ΔI is the zero-sequence current abrupt change; I Kij- This represents the real-time value of the zero-sequence current of the j-th switch on the i-th feeder.

[0093] The second stage involves fault segment selection: After selecting the faulty feeder, all remote control switches are traversed from the power source side (upstream) to the load side (downstream) according to the topology. The fault section is located by comparing the multiples of the zero-sequence current surges of adjacent line switches. Assume the zero-sequence current surge of a certain upstream switch is ∆I. 上游 The zero-sequence current change of the adjacent downstream switch is ∆I 下游 The selection rules are as follows:

[0094] (3)

[0095] (4)

[0096] The empirical value for the multiplier here is set to 3.

[0097] by Figure 2 Taking the simulation model as an example, the fault point is set at switch K of feeder 1. 11 With K 12 Based on the judgment method proposed in this embodiment, the judgment results are as follows:

[0098] The switch with the largest change in zero-sequence current is k11 (located in branch 1, segment 1), with a change of 1.1424 A.

[0099] All switch changes, sorted from largest to smallest, are as follows:

[0100] k11: 1.1424

[0101] k12: 0.007309

[0102] k21: 0.0065247

[0103] k13: 0.0059028

[0104] k31: 0.005668

[0105] k22: 0.0045853

[0106] k32: 0.003952

[0107] k23: 0.003479

[0108] k33: 0.0030625

[0109] The branch with the largest change in real-time zero-sequence current value compared to the reference current value is branch 1, with a change of 1.1424 A.

[0110] The actual values ​​of the zero-sequence current changes at the beginning of each branch are arranged in descending order of magnitude as follows:

[0111] Branch 1: 1.1424 A

[0112] Branch 2: 0.0065 A

[0113] Branch 3: 0.0057 A

[0114] The fault location analysis results show that the fault in branch 1 is located at the beginning of segment k11 (d1 - 1 = 156.33).

[0115] Combination Figure 3 To understand, switch K 11 The zero-sequence current surge ΔI is the largest, so according to the line selection principle, the fault point is likely in feeder 1. Then, the switches K of the faulty feeders are traversed. 11 K 12 With K 13 Combining their ΔI with formulas (3) and (4), it can be seen that switch K 11 With K 12 The zero-sequence current abrupt change reached 156.33 times, far exceeding the set threshold of 3 times, therefore the fault range can be located at K. 11 With K 12 between.

[0116] To compensate for the capacitive current flowing through the fault point after a single-phase ground fault, an arc-suppression coil can be installed at the neutral point of the distribution network to extinguish the arc. However, after compensation by the arc-suppression coil, the steady-state component amplitude characteristics of the single-phase ground fault are not obvious, and it is impossible to distinguish between faulty and non-faulty lines based on the phase difference of the zero-sequence current, making the detection effect of traditional steady-state detection methods unsatisfactory. Therefore, the following analysis examines the judgment effect of the method proposed in this embodiment in the scenario of neutral point grounding via an arc-suppression coil. The model and related parameter settings are as follows, with three cable outgoing lines, each feeder having three switching sections, and each switching section having a line length of 5km. The compensation method of the arc-suppression coil in this model is overcompensation, with a compensation degree of 10%, and the inductance of the arc-suppression coil is L=0.244H.

[0117] Table 5 Cable Line Parameter Settings

[0118] Line type Phase sequence Resistance Ω / km Inductance H / km Capacitance F / km Feeder length (km) cable lines Ascending order 0.2700 0.2550e-3 339e-9 15、15 Zero sequence 2.700 1.0490e-3 280e-9 15

[0119] As described above, the zero-sequence current reference values ​​for each switch are determined, as shown in Table 6. It can be seen that when the switch is configured as a cable outlet, the reference zero-sequence current value increases significantly compared to Table 4. This is because the ground capacitance current of the cable outlet is greater than that of the overhead line. Furthermore, since the line parameters are set to be basically symmetrical, the zero-sequence current reference values ​​for the switches at corresponding positions on the three feeders are equal.

[0120] Table 6. Reference zero-sequence current values ​​when L=0.244H

[0121] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 <!-- 7 -->]]> Feeder 1 10.88102319 7.293406496 3.719778655 Feeder 2 10.88102319 7.293406496 3.719778655 Feeder 3 10.88102319 7.293406496 3.719778655

[0122] When the fault point is set at K in line1 12 With K 13 The steady-state values ​​of the zero-sequence current of each switch measured during this period are shown in Table 7 below.

[0123] Table 7 K 12 With K 13 Zero-sequence current steady-state value during single-phase ground fault

[0124] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 > Feeder 1 13.49613671 9.937265018 3.751289413 Feeder 2 10.87936703 7.279636889 3.708262841 Feeder 3 10.87936703 7.279636889 3.708262841

[0125] Next, the abrupt change in the steady-state value of the zero-sequence current compared to the zero-sequence current value for each switch was calculated, as shown in Table 8. Based on the above judgment principles, switch K... 12 The zero-sequence current surge ∆I is the largest, therefore the fault is determined to occur in feeder 1. Additionally, for the adjacent switch K... 12 With K 13 K 12 ∆I and K 13 The ∆I ratio is greater than 3, therefore the faulty section is determined to be K. 12 With K 13 The analysis was correct.

[0126] Table 8 K 12 With K 13 Zero-sequence current mutation during a single-phase ground fault

[0127] Row <![CDATA[Feeder switch K i1 > <![CDATA[Subordinate line switch K i2 > <![CDATA[Subordinate line switch K i3 > Feeder 1 2.615113521 2.643858522 0.031510758 Feeder 2 0.001656158 0.013769607 0.011515814 Feeder 3 0.001656158 0.013769607 0.011515814

[0128] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the programs include program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.

[0129] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0130] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0131] The foregoing has shown and described the basic principles, main features, and advantages of this disclosure. Those skilled in the art should understand that this disclosure is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this disclosure. Various changes and modifications can be made to this disclosure without departing from its spirit and scope, and all such changes and modifications fall within the scope of this disclosure as claimed.

[0132] This invention is not limited to the preferred embodiment described above. Anyone inspired by this invention can derive other various forms of substation single-phase grounding fault location methods based on zero-sequence current reference values. All equivalent variations and modifications made within the scope of the claims of this invention shall fall within the scope of this invention.

Claims

1. A method for selecting and identifying single-phase grounding faults in substations based on zero-sequence current reference values, characterized in that, include: After a single-phase ground fault occurs, the zero-sequence current of all switches in the non-faulty feeder and the zero-sequence current of the downstream switch of the fault point in the faulty feeder are collected, and the zero-sequence current reference value of the corresponding switch is dynamically updated. Real-time detection of zero-sequence current value of each switch, calculation of the abrupt change of its value with the corresponding zero-sequence current reference value, and determination of the feeder where the switch with the largest abrupt change is located as the faulty feeder. Traverse the adjacent switch pairs of the fault feeder from the power supply side to the load side, and calculate the ratio of the zero-sequence current mutation of the upstream switch to the zero-sequence current mutation of the downstream switch. When the ratio is greater than or equal to a set threshold, the fault is determined to be located between the two adjacent switches; If the ratio of all adjacent switch pairs is less than the set threshold, the fault is determined to be located at the end of the line.

2. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 1, characterized in that: When dynamically updating the zero-sequence current reference value, only two types of data sources are used: Zero-sequence current of all switches on the non-faulty feeder; Zero-sequence current of all switches in the fault feeder located in the direction from the fault point to the load side.

3. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 2, characterized in that: The dynamic update uses the arithmetic mean method: Add the currently collected valid zero-sequence current value to the historical valid dataset; The arithmetic mean of the dataset is used as the updated baseline.

4. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 1, characterized in that: The mutation amount is calculated using the absolute difference: ΔI=∣I Kij - I Kij-base ∣ Where ΔI is the zero-sequence current abrupt change; I Kij Indicates the i The first feeder j Real-time value of zero-sequence current of each switch; I Kij-base Indicates the i The first feeder j The zero-sequence current reference value of each switch.

5. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 1, characterized in that: The set threshold is 3.

6. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 1, characterized in that: The criteria for defining the downstream switch of the fault point are as follows: All switches from the fault point to the load side; Zero-sequence current data from the upstream switch of the fault point is not used for baseline value updates.

7. The method for selecting and identifying single-phase grounding faults in substations based on zero-sequence current reference values ​​as described in claim 1, characterized in that: When applied in an arc suppression coil grounding system: the ratio of sudden changes in the values ​​of adjacent switches at the fault point still satisfies ΔI. 上游 / ΔI 下游 ≥3.

8. The substation single-phase grounding fault location method based on zero-sequence current reference value according to claim 1, characterized in that: The order of traversing adjacent switches is as follows: starting from the switch at the beginning of the feeder, compare adjacent switch pairs step by step towards the load side.

9. A substation single-phase grounding fault location and identification system based on zero-sequence current reference value, characterized in that, include: The data acquisition module is used to collect the zero-sequence current of all switches in the non-faulty feeder and the zero-sequence current of the downstream switch of the fault point in the faulty feeder after a single-phase ground fault occurs. The reference value update module is connected to the data acquisition module and is used to dynamically update the zero-sequence current reference value of each switch. The fault selection module is used to calculate the abrupt change between the real-time value and the reference value of the zero-sequence current of each switch, and to determine the feeder where the switch with the largest abrupt change is located as the faulty feeder. The fault segment selection module is used to traverse the adjacent switch pairs of the fault feeder, calculate the ratio of the zero-sequence current change of the upstream switch to the downstream switch, locate the fault section when the ratio is greater than or equal to the set threshold, otherwise determine that the fault is located at the end of the line. A topology database stores the upstream and downstream connection relationships of feeder switches.

10. A substation fault handling device, comprising a processor and a memory, characterized in that: The memory stores a computer program that, when executed by a processor, implements the steps of the method as described in any one of claims 1-8.

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