Single-phase earth fault line selection method and system based on composite zero sequence admittance deviation degree
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WEIHAI WENDENG POWER SUPPLY CO OF STATE GRID SHANDONG ELECTRIC POWER CO
- Filing Date
- 2022-07-14
- Publication Date
- 2026-06-16
AI Technical Summary
Existing single-phase grounding fault location methods suffer from harmonic interference, signal interference, high equipment costs, high sampling accuracy requirements, and high-frequency harmonic effects caused by grid connection of new energy sources in arc suppression coil grounding systems, leading to location failures or misjudgments.
The method based on composite zero-sequence admittance deviation is adopted. By obtaining the zero-sequence voltage and current of the bus and line, the composite zero-sequence admittance amplitude and phase angle deviation index are calculated to preliminarily screen and verify the faulty lines and determine the final faulty lines.
It improves the accuracy of single-phase grounding fault location, reduces the cost of using and maintaining the device, reduces the impact on transient harmonics, and is suitable for arc suppression coil grounding systems.
Smart Images
Figure CN115616336B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of single-phase grounding fault location technology, and in particular to a method and system for single-phase grounding fault location based on composite zero-sequence admittance deviation. Background Technology
[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.
[0003] The neutral point grounding methods in power distribution networks mainly include ungrounded and grounding through an arc suppression coil. The most common and dangerous faults in power systems are grounding faults or phase-to-phase short circuits. Recent statistics show that single-phase grounding faults have the highest probability of occurrence in power distribution networks, accounting for more than 80% of all faults.
[0004] Currently, the main methods used for fault location of single-phase grounding faults include zero-sequence current method, first half-wave method, signal injection method, fifth harmonic method, and the use of transient and steady-state quantities. The zero-sequence current method selects the faulty line by using the opposite zero-sequence current of the faulty line to the zero-sequence current of the non-faulty line. This method meets the requirements of a neutral-point ungrounded system, but is not suitable for arc-suppression coil grounded systems. The first half-wave method selects the line by using the polarity of the first half-wave of the transient zero-sequence current after a fault occurs on both the faulty and non-faulty lines. The transient current value is not affected by the arc-suppression coil, making it suitable for arc-suppression coil grounded systems. However, a large number of harmonics are generated after a fault occurs, interfering with the detection of the zero-sequence current and increasing the difficulty of line selection. The signal injection method compares the amplitude of the injected signal on each line. The line with the larger injected signal is the faulty line. However, if the injected signal is small, it will be interfered with by the working signal; otherwise, the injected signal will be too large and will interfere with the normal working signal. The fifth harmonic method determines the faulty line by using the characteristic that the fifth harmonic zero-sequence current of each non-faulty feeder is greater than that of the non-faulty line. It achieves fault line selection and distance measurement based on the transient characteristics of DC reactance and capacitor voltage faults. It requires additional capacitor equipment, and it is difficult to accurately select and locate lines with many branches. The method of fault location using transient quantities can make full use of the high content and large amplitude transient fault components generated when a ground fault occurs in the system. However, this method requires high signal acquisition accuracy, high transient signal sampling and processing capabilities, high requirements for fault location devices, and high cost. At the same time, with the development of the power system, the proportion of new energy sources connected to the system is increasing. With the grid connection of new energy sources such as photovoltaic and wind power, a large number of supporting power electronic devices are connected, and a large number of high-frequency harmonic currents are injected into the grid. The high-frequency harmonic components above the 13th order are rapidly increasing in the grid and persisting for a long time. All of these factors bring difficulties to the method of fault location using transient components, ultimately leading to fault location failure or misjudgment. On the other hand, traditional steady-state quantity methods for fault location often suffer from insufficient sensitivity and slow fault location speed, making it difficult to meet the protection requirements of the rapid development of modern power grids. Moreover, many steady-state quantity fault location methods are theoretically flawed or methodologically imperfect, leading to fault location failure or misjudgment, which adds unnecessary burden to the safe and stable operation of the power grid. Summary of the Invention
[0005] To address the aforementioned problems, this invention proposes a method and system for single-phase grounding fault location based on composite zero-sequence admittance deviation. This method utilizes the difference in composite zero-sequence admittance to locate single-phase grounding faults, and is unaffected by three-phase zero-sequence asymmetry, fault resistance, or asynchronous signal sampling, thereby improving the accuracy of single-phase grounding fault location.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] Firstly, a single-phase ground fault location method based on composite zero-sequence admittance deviation is proposed, including:
[0008] Obtain the zero-sequence voltage and phase voltage of the busbar, and the zero-sequence voltage and zero-sequence current of each line;
[0009] Determine whether the system has a single-phase ground fault based on the zero-sequence voltage and phase voltage of the busbar;
[0010] When a single-phase ground fault occurs in the system, obtain the neutral point offset voltage of the system.
[0011] Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is obtained, and the zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line.
[0012] Extract the composite zero-sequence admittance amplitude of the line and the change in the phase angle of the composite zero-sequence admittance of the line before and after a single-phase ground fault in the system, and calculate the composite zero-sequence admittance amplitude deviation index and the phase angle deviation index.
[0013] Based on the amplitude deviation index, the faulty lines are initially screened, and based on the phase angle deviation index, the initially screened faulty lines are reviewed to determine the final faulty lines.
[0014] Secondly, a single-phase ground fault location system based on composite zero-sequence admittance deviation is proposed, including:
[0015] The data acquisition module is used to acquire the zero-sequence voltage and phase voltage of the bus, and the zero-sequence voltage and zero-sequence current of each line;
[0016] The single-phase grounding fault detection module is used to determine whether the system has a single-phase grounding fault based on the zero-sequence voltage and phase voltage of the bus.
[0017] The composite zero-sequence admittance acquisition module is used to acquire the neutral point offset voltage of the system when a single-phase ground fault occurs. Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is acquired. The zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line.
[0018] The amplitude deviation index and phase angle deviation index acquisition module is used to extract the composite zero-sequence admittance amplitude of the line and the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault occurs in the system, and to calculate the composite zero-sequence admittance amplitude deviation index and phase angle deviation index.
[0019] The fault line determination module is used to initially screen fault lines based on the amplitude deviation index, and to verify the initially screened fault lines based on the phase angle deviation index to determine the final fault line.
[0020] Thirdly, an electronic device is proposed, including a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When the computer instructions are executed by the processor, they complete the steps described in the single-phase ground fault location method based on composite zero-sequence admittance deviation.
[0021] Fourthly, a computer-readable storage medium is proposed for storing computer instructions, which, when executed by a processor, complete the steps described in the single-phase ground fault location method based on composite zero-sequence admittance deviation.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] 1. This invention calculates the composite zero-sequence admittance of each line, and based on this, calculates the composite zero-sequence admittance amplitude deviation index and phase angle deviation index. The amplitude deviation index is used for preliminary screening of faulty lines, and the phase angle deviation index is used to verify the preliminary screening of faulty lines, thus determining the final faulty line. This method is unaffected by three-phase zero-sequence asymmetry, fault resistance, or asynchronous signal sampling. Compared with the traditional steady-state quantity-based line selection method, it improves the line selection mechanism and enhances the accuracy of line selection protection. Compared with the transient method, it is less affected by transient harmonics, has lower requirements for sampling and data processing equipment, is easier to use, and has lower operation and maintenance costs.
[0024] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.
[0026] Figure 1 This is a flowchart of the method disclosed in Example 1;
[0027] Figure 2 A 10kV distribution network simulation model was established for Example 1;
[0028] Figure 3 The zero-sequence current of each line obtained in Example 1;
[0029] Figure 4 The zero-sequence voltages of each line obtained in Example 1;
[0030] Figure 5 The zero-sequence admittance of each line obtained in Example 1;
[0031] Figure 6 The absolute value of the zero-sequence admittance obtained in Example 1;
[0032] Figure 7 The composite zero-sequence admittance amplitude obtained in Example 1. Detailed implementation method:
[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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.
[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0036] Example 1
[0037] In this embodiment, a single-phase ground fault location method based on composite zero-sequence admittance deviation is disclosed, including:
[0038] Obtain the zero-sequence voltage and phase voltage of the busbar, and the zero-sequence voltage and zero-sequence current of each line;
[0039] Determine whether the system has a single-phase ground fault based on the zero-sequence voltage and phase voltage of the busbar;
[0040] When a single-phase ground fault occurs in the system, obtain the neutral point offset voltage of the system.
[0041] Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is obtained, and the zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line.
[0042] Extract the composite zero-sequence admittance amplitude of the line and the change in the phase angle of the composite zero-sequence admittance of the line before and after a single-phase ground fault in the system, and calculate the composite zero-sequence admittance amplitude deviation index and the phase angle deviation index.
[0043] Based on the amplitude deviation index, the faulty lines are initially screened, and based on the phase angle deviation index, the initially screened faulty lines are reviewed to determine the final faulty lines.
[0044] This embodiment provides a detailed description of the single-phase grounding fault location method based on composite zero-sequence admittance deviation.
[0045] A single-phase ground fault location method based on composite zero-sequence admittance deviation, such as Figure 1 As shown, it includes:
[0046] S1: Obtain the phase voltage and zero-sequence voltage of the bus and the zero-sequence voltage and zero-sequence current of each line.
[0047] In practical implementation, the system's operating voltage and operating current are obtained; and the zero-sequence voltage of the bus and the zero-sequence voltage and zero-sequence current of each line are calculated using the operating voltage and operating current.
[0048] S2: Determine whether a single-phase grounding fault has occurred in the system based on the zero-sequence voltage and phase voltage of the bus.
[0049] When the zero-sequence voltage of the bus exceeds the set multiple of the phase voltage of the system, and the phase voltage of one phase of the bus decreases while the phase voltages of the other two phases increase, it is determined that a single-phase ground fault has occurred in the system.
[0050] When a single-phase ground fault occurs in the system, start line selection and fault recording, and execute S3; otherwise, retain the current cycle voltage and current data, and repeat S1 and S2.
[0051] In practical implementation, the multiplier is set to 15%. That is, when the zero-sequence voltage of the bus exceeds 15% of the phase voltage of the system, and one phase voltage of the bus decreases while the other two phase voltages increase, it is determined to be a single-phase ground fault in the system.
[0052] S3: When a single-phase ground fault occurs in the system, obtain the neutral point offset voltage of the system; based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, obtain the zero-sequence admittance of each line, and accumulate the zero-sequence admittance of each line to obtain the composite zero-sequence admittance of the line.
[0053] For an ungrounded neutral system, if the three-phase zero-sequence parameters are unbalanced, a neutral point offset voltage will appear. For a non-faulty line h, consider the zero-sequence admittance Y when the three-phase zero-sequence parameters of the line are unbalanced. 0h for:
[0054]
[0055] in, Let h be the zero-sequence current of line h. This refers to the zero-sequence current under non-fault conditions. This is the neutral point offset voltage. Apply voltage to the fault.
[0056] Zero-sequence admittance Y of faulty line f 0f for:
[0057]
[0058] in, Let f be the zero-sequence current of line f. This refers to the zero-sequence current of line f under non-fault conditions. Y is the neutral point offset voltage. L This is the admittance of the grounding branch of the arc suppression coil.
[0059] The zero-sequence admittance Y is obtained 0f During the sampling period, the zero-sequence admittance Y 0f The composite zero-sequence admittance phasor is obtained by phasor summation, and the final composite zero-sequence admittance value Y is obtained. 0ca for
[0060]
[0061] Where t0 is the start time of the first cycle, t g Let g be the end time after the g-th period, where g is the time from t0 to t1. g The number of cycles passed, Re[Y 0f [t] represents the zero-sequence admittance Y. 0f The real part of [t], Im[Y 0f [t] represents the zero-sequence admittance Y. 0f The imaginary part of [t], where j is the imaginary factor.
[0062] Compared to the directly obtained zero-sequence admittance, the composite zero-sequence admittance can more stably reflect the energy flow of the fault, point to the faulty line, and reflect the difference between the faulty and non-faulty lines with high accuracy. The line selection is more accurate and reliable than the traditional zero-sequence admittance method.
[0063] In engineering applications, the composite zero-sequence admittance Y can be calculated using the following formula (4) within the sampling period. 0ca .
[0064]
[0065] Where k = 1, 2, 3, ..., m are the sampling points, m is the number of sampling points, [Y 0f [k]] is the zero-sequence admittance of line f at sampling point k.
[0066] S4: Extract the composite zero-sequence admittance amplitude of the line and the change in the phase angle of the composite zero-sequence admittance before and after a single-phase ground fault in the system, and calculate the deviation index of the composite zero-sequence admittance amplitude and the phase angle deviation index.
[0067] The specific process of the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault in the system is as follows:
[0068] Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line before the single-phase ground fault in the system, the zero-sequence admittance of each line before the single-phase ground fault in the system is obtained. The zero-sequence admittance of each line before the single-phase ground fault in the system is accumulated to obtain the composite zero-sequence admittance of the line before the single-phase ground fault in the system.
[0069] Extract the composite zero-sequence admittance phase angle of the line before the single-phase ground fault occurs and the composite zero-sequence admittance phase angle of the line when the single-phase ground fault occurs.
[0070] Based on the two phase angles, the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault is obtained. Specifically, the difference between the composite zero-sequence admittance phase angle of the line when a single-phase ground fault occurs and the composite zero-sequence admittance phase angle of the line before the single-phase ground fault occurs is obtained.
[0071] Because power systems may have sampling asynchrony issues in actual operation, the asynchronous sampling of voltage and current on a single line can cause the calculated zero-sequence admittance of that line to rotate clockwise or counterclockwise compared to the actual zero-sequence admittance; and the transmission delay of different lines can cause the phase angle of the zero-sequence admittance of asynchronous lines to deviate from that of other lines.
[0072] Therefore, the composite zero-sequence admittance phase angle of each line is preliminarily processed. First, to address the potential sampling asynchrony issue on a single line, after a fault is detected, the phase angle value of the previous cycle is maintained, and the difference between the current phase angle value and the phase angle value before the fault is calculated to obtain the phase angle change of the composite zero-sequence admittance before and after the fault. Second, for the transmission delay between lines, the moment when the zero-sequence voltage change is detected on each line is taken as the starting time, and the lines are integrated into the same coordinate system for analysis.
[0073] Taking line i as an example, the processed composite zero-sequence admittance Y is extracted. 0cai (The amplitude A of the composite zero-sequence admittance that appears subsequently is the value obtained after integration) 0i With phase angle change θ 0i .
[0074]
[0075]
[0076] in, The composite zero-sequence admittance phase angle after a single-phase ground fault occurs on line i. Let Re[Y] be the composite zero-sequence admittance phase angle before a single-phase ground fault occurs on line i. 0cai [Y is the composite zero-sequence admittance of line i] 0cai The real part, Im[Y 0cai[Y is the composite zero-sequence admittance of line i] 0cai The imaginary part.
[0077] Due to the differences in parameters between overhead lines and cable lines, in order to avoid errors in the fault selection algorithm when the busbar is faulty, the root mean square of the magnitude of the composite zero-sequence admittance is used as the basic quantity for the fault selection algorithm.
[0078]
[0079] Define the composite zero-sequence admittance magnitude deviation index P of line i Yi With phase angle deviation index P θi for:
[0080]
[0081]
[0082] Among them, Q 0ir Q 0jr Let θ be the root mean square of the magnitude of the composite zero-sequence admittance of lines i and j. 0ir θ 0jr Let be the phase angle change of the composite zero-sequence admittance of lines i and j, r be the number of sampling points at a fixed sampling interval, c be the number of sampling points at a fixed sampling interval within the selected sampling time range, and n be the total number of lines.
[0083] S5: Based on the amplitude deviation index, the faulty lines are initially screened. Based on the phase deviation index, the initially screened faulty lines are reviewed to determine the final faulty lines. Specifically: when the amplitude deviation index of line i is greater than that of the other lines, line i is the initially screened faulty line; when the absolute value of the phase deviation index of the initially screened faulty line is the largest and the sign is opposite to that of the phase deviation index of the other lines, the initially screened faulty line is determined to be the final faulty line.
[0084] The line composite zero-sequence admittance amplitude deviation index indicates the degree of deviation between the magnitudes of the zero-sequence admittance of each line. The higher the value, the less similar the line is to other lines, and the more likely it is to be a faulty line. This index can be used to make a preliminary judgment on the faulty line.
[0085] For healthy lines in the system, when the basic line parameters of each line are not significantly different, the zero-sequence admittance phase angles of each line are also not significantly different, so the zero-sequence admittance phase angle difference of each line is approximately 0. At this time, the dispersion of the phase angle difference of each healthy line is close to 0, and the sign is positive. However, for faults in the system, their zero-sequence admittance phase angles differ significantly from those of healthy lines, that is, the phase angle deviation is large. This is used to verify and determine the faulty line.
[0086] Therefore, when initially screening faulty lines based on the amplitude deviation index, each line is compared according to the amplitude deviation index. When a line exhibits a composite zero-sequence admittance amplitude deviation P, the comparison is made. Yi If the deviation is greater than that of all other lines, the line is preliminarily identified as a faulty line; otherwise, return to S2.
[0087] The composite zero-sequence admittance phase angle dispersion index P of line i θi Compare with other lines one by one, if |P θi If the value is the maximum and the phase angle dispersion sign is opposite to that of other lines, line i is determined to be a faulty line, the line selection ends, and a fault trip signal is issued. Otherwise, return to S4.
[0088] Establish a 10kV distribution network simulation model as follows Figure 2 As shown, G is the system's equivalent power source; T is the main transformer with a rated capacity of 100MVA; L arc For an arc suppression coil with adjustable detuning, R arc The resistor is connected in series with the arc suppression coil.
[0089] The system model consists of seven lines, L1-L7, with lengths of 4km, 6km, 6km, 8km, 8km, 10km, and 6km respectively. The main parameters of the lines in the system model are shown in Table 1. Among the lines, L1 is a purely cable line, L2 is a purely overhead line, and the remaining lines are a hybrid of cable and overhead lines. L1-L4 do not contain branches, while L6 has a cable branch, L7. The zero-sequence admittance of lines L4 and L2 is asymmetrical.
[0090] Table 1 Feeder Parameter Table
[0091]
[0092] Suppose a single-phase ground fault occurs on line L4. The fault occurs at 0.126s and lasts for 0.25s. The zero-sequence currents of each line are as follows: Figure 3 As shown, the zero-sequence voltage of each line is as follows: Figure 4 As shown, when selecting a faulty line according to the single-phase grounding fault selection method based on composite zero-sequence admittance deviation disclosed in this embodiment, the obtained zero-sequence admittance is as follows: Figure 5 As shown, the absolute value of the zero-sequence admittance is as follows Figure 6 As shown, the composite zero-sequence admittance magnitude coefficient is as follows Figure 7 As shown,
[0093] The deviation of the composite zero-sequence admittance amplitude for each line can be obtained by calculating the deviation index using simulation data.
[0094]
[0095] It can be seen that the deviation of the composite zero-sequence admittance amplitude of line L4 is much greater than that of the other lines. Although the deviation of the other lines will vary in magnitude due to the differences in feeder type, line length and the influence of line L4, the overall trend of magnitude remains unchanged, and it can be preliminarily judged that line L4 is a faulty line.
[0096] Calculate the phase angle deviation of the composite zero-sequence admittance for each line.
[0097]
[0098] As can be seen from the above, the absolute value of the composite zero-sequence admittance phase angle deviation of line L4 is greater than that of other lines, and the signs are opposite. Due to the differences in feeder type, line length, and the influence of line L4, the deviation of each line other than line L4 will vary in magnitude, but the overall magnitude and the positive-to-negative relationship remain unchanged. Therefore, line L4 can be identified as the faulty line.
[0099] The above analysis confirms that the line experiencing the single-phase ground fault is L4, which fully verifies the accuracy of the single-phase ground fault line selection method based on composite zero-sequence admittance deviation disclosed in this embodiment for fault line selection.
[0100] This embodiment discloses a single-phase ground fault location method based on composite zero-sequence admittance deviation. It calculates the composite zero-sequence admittance of each line, and based on this, calculates the composite zero-sequence admittance amplitude deviation index and phase angle deviation index. The amplitude deviation index is used for preliminary screening of faulty lines, and the phase angle deviation index is used for verification to determine the final faulty line. This method is unaffected by three-phase zero-sequence asymmetry, fault resistance, or asynchronous signal sampling. Compared with traditional steady-state quantity-based fault location methods, it improves the fault location mechanism and enhances the accuracy of fault location protection. Compared with transient methods, it is less affected by transient harmonics, has lower requirements for sampling and data processing equipment, is easier to use, and has lower operation and maintenance costs.
[0101] Example 2
[0102] In this embodiment, a single-phase ground fault location system based on composite zero-sequence admittance deviation is disclosed, comprising:
[0103] The data acquisition module is used to acquire the zero-sequence voltage and phase voltage of the bus, and the zero-sequence voltage and zero-sequence current of each line;
[0104] The single-phase grounding fault detection module is used to determine whether the system has a single-phase grounding fault based on the zero-sequence voltage and phase voltage of the bus.
[0105] The composite zero-sequence admittance acquisition module is used to acquire the neutral point offset voltage of the system when a single-phase ground fault occurs. Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is acquired. The zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line.
[0106] The amplitude deviation index and phase angle deviation index acquisition module is used to extract the composite zero-sequence admittance amplitude of the line and the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault occurs in the system, and to calculate the composite zero-sequence admittance amplitude deviation index and phase angle deviation index.
[0107] The fault line determination module is used to initially screen fault lines based on the amplitude deviation index, and to verify the initially screened fault lines based on the phase angle deviation index to determine the final fault line.
[0108] Example 3
[0109] In this embodiment, an electronic device is disclosed, including a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When the processor executes the computer instructions, it completes the steps of the single-phase ground fault location method based on composite zero-sequence admittance deviation disclosed in Embodiment 1.
[0110] Example 4
[0111] In this embodiment, a computer-readable storage medium is disclosed for storing computer instructions. When the computer instructions are executed by a processor, they complete the steps described in the single-phase ground fault location method based on composite zero-sequence admittance deviation disclosed in Embodiment 1.
[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A method for locating single-phase ground faults based on composite zero-sequence admittance deviation, characterized in that, include: Obtain the zero-sequence voltage and phase voltage of the busbar, and the zero-sequence voltage and zero-sequence current of each line; Determine whether the system has a single-phase ground fault based on the zero-sequence voltage and phase voltage of the busbar; When a single-phase ground fault occurs in the system, obtain the neutral point offset voltage of the system. Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is obtained, and the zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line. Extract the composite zero-sequence admittance amplitude of the line and the phase angle change of the composite zero-sequence admittance of the line before and after the single-phase ground fault in the system: Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line before the single-phase ground fault in the system, obtain the zero-sequence admittance of each line before the single-phase ground fault in the system, and sum the zero-sequence admittance of each line before the single-phase ground fault in the system to obtain the composite zero-sequence admittance of the line before the single-phase ground fault in the system. Extract the composite zero-sequence admittance phase angle of the line before the single-phase ground fault occurs and the composite zero-sequence admittance phase angle of the line when the single-phase ground fault occurs. Based on the two phase angles, the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault in the system is obtained. ; in, For the line Composite zero-sequence admittance phase angle after a single-phase ground fault. For the line i The composite zero-sequence admittance phase angle prior to a single-phase ground fault; And calculate the composite zero-sequence admittance magnitude deviation index. Deviance from phase angle index : in, , For the line , The root mean square of the magnitude of the composite zero-sequence admittance. , For the line , The phase angle change of the composite zero-sequence admittance. Sampling points with a fixed sampling interval This represents the number of sampling points within a fixed sampling interval included in the selected sampling time range. Total number of lines; Based on the amplitude deviation index, the faulty lines are initially screened, and based on the phase angle deviation index, the initially screened faulty lines are reviewed to determine the final faulty lines.
2. The single-phase grounding fault location method based on composite zero-sequence admittance deviation as described in claim 1, characterized in that, When the zero-sequence voltage of the bus exceeds the set multiple of the system phase voltage, and the phase voltage of one phase of the bus decreases while the phase voltages of the other two phases increase, it is determined that a single-phase ground fault has occurred in the system.
3. The single-phase grounding fault location method based on composite zero-sequence admittance deviation as described in claim 1, characterized in that, When the line i When the amplitude deviation index of line A is greater than that of other lines, line B is considered to be in a negative position. i These are the faulty lines identified in the initial screening.
4. The single-phase grounding fault location method based on composite zero-sequence admittance deviation as described in claim 1, characterized in that, When the absolute value of the phase angle deviation index of the initially screened faulty line is the largest and the sign is opposite to that of the phase angle dispersion of the other lines, the initially screened faulty line is determined to be the final faulty line.
5. The single-phase grounding fault location method based on composite zero-sequence admittance deviation as described in claim 1, characterized in that, The composite zero-sequence admittance of the circuit is calculated using the following formula. : in, For sampling points, The number of sampling points. For the line f exist k Zero-sequence admittance at a single sampling point.
6. A single-phase ground fault location system based on composite zero-sequence admittance deviation, employing the single-phase ground fault location method based on composite zero-sequence admittance deviation as described in any one of claims 1-5, characterized in that, include: The data acquisition module is used to acquire the zero-sequence voltage and phase voltage of the bus, and the zero-sequence voltage and zero-sequence current of each line; The single-phase grounding fault detection module is used to determine whether the system has a single-phase grounding fault based on the zero-sequence voltage and phase voltage of the bus. The composite zero-sequence admittance acquisition module is used to acquire the neutral point offset voltage of the system when a single-phase ground fault occurs. Based on the zero-sequence voltage, zero-sequence current and neutral point offset voltage of the line, the zero-sequence admittance of each line is acquired. The zero-sequence admittance of each line is accumulated to obtain the composite zero-sequence admittance of the line. The amplitude deviation index and phase angle deviation index acquisition module is used to extract the composite zero-sequence admittance amplitude of the line and the change in the composite zero-sequence admittance phase angle of the line before and after a single-phase ground fault occurs in the system, and to calculate the composite zero-sequence admittance amplitude deviation index and phase angle deviation index. The fault line determination module is used to initially screen fault lines based on the amplitude deviation index, and to verify the initially screened fault lines based on the phase angle deviation index to determine the final fault line.
7. An electronic device, characterized in that, It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, perform the steps of a method according to any one of claims 1-5.
8. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the steps of a method according to any one of claims 1-5.