A method for measuring fault location of feeder lines in distribution network

Abstract

The present invention discloses a distribution network feeder fault distance measurement method, which comprises: S1, applying a high-voltage pulse to a fault line, and collecting a starting-end voltage waveform of the fault line; S2, judging the reflection and transmission conditions at a fault point of the fault line according to the starting-end voltage waveform analysis, if the fault point is total reflection, proceeding to step S3, if reflection and transmission occur simultaneously at the fault point, proceeding to step S4; S3, applying a high-voltage pulse to the starting end and the ending end of the fault line respectively, measuring the line fault distance by analyzing the high-voltage waveforms at both ends, eliminating the influence of the wave velocity on the measurement result, and obtaining the corresponding fault distance; S4, measuring the line fault distance by analyzing the starting-end voltage waveform of the fault line, eliminating the influence of the wave velocity on the measurement result, and obtaining the corresponding fault distance.

Description

Technical Field

[0001] The present invention relates to the field of distribution network feeder fault location and distance measurement, and in particular to a distribution network feeder fault distance measurement method. Background Art

[0002] As we all know, in distribution network systems, effective fault distance measurement technology can not only accurately and quickly locate fault points, but also provide accurate and reliable data to on-site line patrol personnel in a timely manner. It can reduce the current line fault patrol range to more than 90%, thereby effectively reducing the labor intensity of line patrol personnel and ultimately improving line fault patrol efficiency and fault patrol rate, providing strong support for restoring system power supply as soon as possible, reducing the comprehensive economic losses caused by power outages, and even improving the safe, stable and economic operation level of the power system.

[0003] Currently, fault location can be divided into three areas based on the accuracy of the location: fault line selection, fault section location, and fault distance measurement. Fault distance measurement directly, quickly, and accurately locates the fault point, eliminating the need for manual line inspections to locate the fault point.

[0004] Among the many fault location methods, pulse ranging uses the principle of pulse reflection to inject a pulse into the line and measure the distance by measuring the time difference between the injected and reflected pulses. This approach can easily achieve fault location. However, the inventors have found that when using this pulse ranging method, when the pulse is short, its high-frequency component is rich and attenuates significantly on the line. When the pulse is long, the measured high-voltage waveform may show overlap between the incident and reflected pulses, as feeders are generally shorter than transmission lines. Furthermore, due to the wide and complex distribution of distribution network lines, the inconsistent wave speeds of different lines can also have a certain impact on the accuracy of fault location.

[0005] Therefore, in order to solve the problems existing in the fault location method based on the pulse reflection principle, the present invention designs a new distribution network feeder fault location method based on long pulses that can eliminate the influence of wave speed. Summary of the Invention

[0006] In order to overcome the defects of the above-mentioned prior art, the technical problem to be solved by the present invention is: to solve the problem of distribution network feeder fault location and ranging. In combination with the characteristics of short distribution network feeder distance and inconsistent line wave speed, a distribution network feeder fault ranging method based on long pulses that can eliminate the influence of wave speed is designed and obtained. The distribution network feeder fault ranging method can provide feeder fault distance measurement for distribution network systems with shorter lines in a relatively simple and accurate manner. It is based on long pulses for measurement and can effectively avoid the problem of excessive attenuation of high-frequency components of short pulses. At the same time, it solves the problems of inconsistent line wave speed and long pulse overlap, thereby improving the ranging accuracy.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution: a distribution network feeder fault location method, which includes the following steps:

[0008] S1. Apply a high-voltage pulse to the fault line and collect the voltage waveform at the starting end of the fault line;

[0009] S2. Analyze the reflection and transmission conditions at the fault point of the fault line based on the starting-end voltage waveform. If the fault point is totally reflected, proceed to step S3. If both reflection and transmission occur at the fault point, proceed to step S4.

[0010] S3, applying high voltage pulses at the starting and ending points of the fault line respectively, measuring the line fault distance by analyzing the high voltage waveforms at both ends, and eliminating the influence of wave velocity on the measurement results to obtain the corresponding fault distance;

[0011] S4. Measure the line fault distance by analyzing the voltage waveform at the starting end of the fault line, and eliminate the influence of the wave velocity on the measurement result to obtain the corresponding fault distance.

[0012] Furthermore, in the distribution network feeder fault location method of the present invention, in step S2, the reflection and transmission conditions at the fault point of the fault line are determined based on the starting-end voltage waveform analysis, including the following steps:

[0013] S21. If the voltage waveform at the initial end of the fault line is always two pulses, one positive and one negative, then the fault point is a total reflection;

[0014] S22. If the voltage waveform at the starting end of the fault line includes one positive pulse and two negative pulses, reflection and transmission occur simultaneously at the fault point.

[0015] In the present invention, the reflection and transmission conditions at the fault point of the fault line are analyzed to determine whether the feeder fault point will produce total reflection of the starting high-voltage pulse. Specifically, the judgment is made by observing the starting voltage waveform. When a high-voltage pulse is applied to the fault line: if the starting voltage waveform is always two pulses, one positive and one negative, then there is total reflection at the fault point; if the starting voltage waveform contains one positive pulse and two negative pulses, then there is both reflection and transmission at the fault point.

[0016] Furthermore, in the distribution network feeder fault location method of the present invention, in step S3, if the positive pulse width in the starting-end voltage waveform is less than the initial pulse width, the fault distance x is calculated as follows:

[0017]

[0018] Where l is the distance from the beginning to the end of the fault line, t1 is the trailing edge time of the positive pulse in the voltage waveform at the beginning, and t1' is the trailing edge time of the positive pulse in the voltage waveform at the end.

[0019] Furthermore, in the distribution network feeder fault location method of the present invention, in step S3, if the positive pulse width in the starting-end voltage waveform is equal to the initial pulse width, the fault distance x is calculated as follows:

[0020]

[0021] Where l is the distance from the beginning to the end of the fault line, t2 is the leading edge time of the negative pulse in the voltage waveform at the beginning, and t2' is the leading edge time of the negative pulse in the voltage waveform at the end.

[0022] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, the voltage waveform at the starting end of the fault line is classified to obtain the following situations:

[0023] (a) The initial voltage waveform includes one positive pulse and two negative pulses, and the width of the positive pulse is equal to the width of the initial pulse;

[0024] (b) The positive pulse width in the initial voltage waveform is equal to the initial pulse width, and the negative pulse has three different amplitude steps due to overlap;

[0025] (c) The positive pulse of the initial voltage waveform has two different amplitude steps and two separated negative pulses;

[0026] (d) the positive pulse of the starting voltage waveform has two different amplitude steps, and the negative pulse has three different amplitude steps;

[0027] (e) The positive pulse of the initial voltage waveform has 2 to 3 different amplitude steps, and the negative pulse has two different amplitude steps.

[0028] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, if the starting voltage waveform is the above case (a), the calculation formula for the fault distance x is:

[0029]

[0030] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first negative pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

[0031] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, if the starting voltage waveform is the above case (b), the calculation formula for the fault distance x is:

[0032]

[0033] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first amplitude step in the negative pulse of the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

[0034] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, if the starting voltage waveform is the above-mentioned case (c), the calculation formula of the fault distance x is:

[0035]

[0036] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

[0037] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, if the starting voltage waveform is the above-mentioned case (d), the calculation formula of the fault distance x is:

[0038]

[0039] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

[0040] Furthermore, in the distribution network feeder fault location method of the present invention, in step S4, if the starting voltage waveform is the above-mentioned case (e), the calculation formula of the fault distance x is:

[0041]

[0042] Where, l is the distance from the beginning to the end of the fault line, is the trailing edge time of the first amplitude step of the positive pulse in the initial voltage waveform, It is the trailing edge time of the second amplitude step of the positive pulse in the initial voltage waveform.

[0043] The beneficial effects of the present invention are as follows: first, a high-voltage pulse is applied to the fault line, and the voltage waveform at the starting end is observed to determine whether total reflection occurs at the fault point. Then, in the case of total reflection at the fault point, a high-voltage pulse is applied to the starting end and the terminal end of the line respectively, and the line fault distance is achieved by analyzing the high-voltage waveforms at both ends, and the influence of the wave velocity on the measurement results is eliminated during the implementation process. For a more general case, that is, the case where reflection and transmission occur simultaneously at the fault point, the line fault distance is achieved only by analyzing the voltage waveform at the starting end, and the influence of the wave velocity on the measurement results is eliminated during the implementation process. The distribution network feeder fault distance measurement method designed by the present invention is relatively simple and accurate, and provides feeder fault distance measurement for distribution network systems with shorter lines. It is based on long pulses for measurement and can avoid the problem of excessive attenuation of high-frequency components of short pulses. At the same time, it solves the problems of inconsistent line wave velocities and overlapping long pulses, thereby improving the distance measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a flowchart of the steps of the distribution network feeder fault location method in one embodiment.

[0045] Figure 2 The broken line diagram schematically shows the total reflection of the starting voltage waveform at the fault point of the fault line.

[0046] Figure 3 The broken line diagram schematically shows that the initial voltage waveform of the fault line at the fault point simultaneously reflects and transmits the initial voltage waveform.

[0047] Figure 4 Schematically shows the Figure 2 The voltage waveform at the starting point under total reflection is shown.

[0048] Figure 5 Schematically shows the Figure 3 The voltage waveforms at the starting point under reflection and transmission conditions are shown.

[0049] Figure 6 Schematically shows the Figure 2 The broken line graph shown is when high voltage pulses are applied to the beginning and end of the fault line respectively under the condition of total reflection.

[0050] Figure 7 The schematic diagram shows the voltage waveform and line graph at the starting point when there is total reflection at the fault point and no overlap between the incident and reflected pulses.

[0051] Figure 8 The schematic diagram shows the voltage waveform and line graph at the starting point when there is total reflection at the fault point and the incident and reflected pulses overlap.

[0052] Figure 9The schematic diagram shows the voltage waveform and line graph at the starting point when reflection and transmission exist at the fault point and there is no pulse overlap.

[0053] Figure 10 The schematic diagram shows the voltage waveform and line graph at the starting point when reflection, transmission and overlapping negative pulses exist at the fault point.

[0054] Figure 11 The schematic diagram shows the voltage waveform and line graph at the starting point when reflection and transmission exist at the fault point and the first negative pulse overlaps.

[0055] Figure 12 The schematic diagram shows the voltage waveform and line graph at the starting point when reflection and transmission exist at the fault point, the first negative pulse overlaps, and the two negative pulses overlap.

[0056] Figure 13 The schematic diagram shows the voltage waveform and line graph at the starting point when reflection and transmission exist at the fault point and a positive pulse and two negative pulses overlap. DETAILED DESCRIPTION

[0057] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0058] The key concept of the present invention lies in: based on long pulse measurement, it first applies a high-voltage pulse to the fault line to determine whether total reflection occurs at the fault point by observing the voltage waveform at the starting end. Then, in the case of total reflection at the fault point, high-voltage pulses are applied to the starting and ending ends of the line respectively. By analyzing the high-voltage waveforms at both ends, the line fault distance is achieved, and the influence of wave velocity on the measurement results is eliminated. For the more general case, that is, the situation where reflection and transmission occur simultaneously at the fault point, the present invention can determine the line fault distance by analyzing only the voltage waveform at the starting end, and eliminate the influence of wave velocity on the measurement results during implementation.

[0059] Please refer to Figure 1 As shown, the present invention designs a distribution network feeder fault location method, which specifically includes the following steps:

[0060] S1. Apply a high-voltage pulse to the fault line and collect the voltage waveform at the starting end of the fault line;

[0061] S2. Analyze the reflection and transmission conditions at the fault point of the fault line based on the starting-end voltage waveform. If the fault point is totally reflected, proceed to step S3. If both reflection and transmission occur at the fault point, proceed to step S4.

[0062] S3, applying high voltage pulses at the starting and ending points of the fault line respectively, measuring the line fault distance by analyzing the high voltage waveforms at both ends, and eliminating the influence of wave velocity on the measurement results to obtain the corresponding fault distance;

[0063] S4. Measure the line fault distance by analyzing the voltage waveform at the starting end of the fault line, and eliminate the influence of the wave velocity on the measurement result to obtain the corresponding fault distance.

[0064] In the present invention, it is first necessary to apply a high voltage pulse to the fault line, and specifically to determine whether total reflection occurs at the fault point by observing the voltage waveform at the starting end. Figure 2 and Figure 3 As shown, using Figure 2 and Figure 3 The line graph shown can clearly demonstrate the internal logic of determining whether total reflection occurs at the fault point.

[0065] See Figure 2 It can be seen that when there is total reflection at the fault point F, there is no signal at the terminal N of the fault line, and a reflected signal can be measured at the starting point M of the fault line. When there is both reflection and transmission at the fault point F, then Figure 3 As shown in the figure, the transmission signal can be measured at the terminal N of the fault line, and two reflected signals can be measured at the starting point M of the fault line. One reflected signal comes from the direct reflection at the fault point F, and the other reflected signal comes from the transmission signal reaching the terminal N and then being transmitted through the fault point F.

[0066] Therefore, when a high voltage pulse is applied at the beginning, Figure 1 and Figure 2 From the analysis of the line graph shown, we can see that the voltage waveform at the start end can be divided into the following categories: Figure 4 and Figure 5 There are two types shown, so the reflection and transmission conditions at the fault point of the fault line can be analyzed and judged according to the starting voltage waveform diagram.

[0067] like Figure 4 and Figure 5 As shown, in step S2 of the distribution network feeder fault location method designed by the present invention, the reflection and transmission conditions at the fault point of the fault line are determined based on the starting voltage waveform analysis, which specifically includes the following steps:

[0068] S21. If the voltage waveform at the beginning of the fault line is always Figure 4 As shown in the figure, there are two pulses, one positive and one negative, and the fault point F is totally reflected;

[0069] S22. If the voltage waveform at the beginning of the fault line includes Figure 5 As shown in FIG. 1 , there is one positive pulse and two negative pulses, and reflection and transmission occur simultaneously at the fault point.

[0070] It should be noted that in Figure 4 and Figure 5 In the waveform diagram, T and τ are also set. It should be noted that τ represents the pulse width, and T represents the time interval between the pulse propagating from the fault point to the starting point. Figure 4 and Figure 5 The settings are only for understanding and will not be described here.

[0071] Furthermore, in step S3 of the present invention, for the total reflection of the fault point F, in order to eliminate the influence of wave velocity on the measurement results, after applying high voltage pulses at the starting end M and the terminal end N of the fault line respectively, it is necessary to measure the time delay of the reflected pulses at both ends. The specific principle is as follows: Figure 6 shown.

[0072] like Figure 6 As shown, Δt1 represents the time interval between the pulse generated by the starting end and the reflected pulse received from the fault point; Δt2′ represents the time interval between the pulse generated by the terminal and the reflected pulse received from the fault point.

[0073] In addition, since the actually emitted high-voltage pulse has a certain width, when this pulse width is large, the time when the front edge of the reflected pulse reaches the measuring end may overlap with the duration of the incident pulse. Therefore, in step S3 of the distribution network feeder fault location method of the present invention, it is also necessary to determine whether there is overlap between the incident pulse and the reflected pulse based on the measured starting-end voltage waveform, and specifically divide it into the following two cases A and B to detect and obtain the corresponding fault distance x:

[0074] A: If the measured initial voltage waveform is as follows Figure 7 As shown in (a), the positive pulse width is equal to the initial pulse width, indicating that there is no overlap between the incident pulse and the reflected pulse.

[0075] At this time, the time difference t2 between the positive pulse leading edge and the negative pulse leading edge in the voltage waveform at the starting end (t2 is the leading edge time of the negative pulse in the voltage waveform at the starting end) is the time it takes for the high voltage pulse to travel back and forth between the starting end and the fault point. Its internal logic is as follows: Figure 7 (b) shown.

[0076] Figure 7 It shows that after the starting end sends a rectangular pulse with a width of t1, the relationship between the wave velocity v, the time t2 for the high-voltage pulse to travel back and forth between the starting end and the fault point, and the fault distance x can be obtained based on the starting end voltage waveform:

[0077] vt2=2x

[0078] Similarly, when the terminal emits a rectangular pulse with a width of t2, the relationship between the wave velocity v, the time t2' for the high-voltage pulse to travel back and forth between the terminal and the fault point, and the fault distance x can be obtained based on the terminal voltage waveform:

[0079] vt2'=2(lx)

[0080] Therefore, after eliminating the wave velocity, the fault distance x is calculated as follows:

[0081]

[0082] Where l is the distance from the beginning to the end of the fault line, t2 is the leading edge time of the negative pulse in the voltage waveform at the beginning, and t2' is the leading edge time of the negative pulse in the voltage waveform at the end.

[0083] B: If the measured initial voltage waveform is as follows Figure 8 As shown in (a), the positive pulse width is smaller than the initial pulse width, indicating that there is overlap between the incident and reflected pulses.

[0084] At this time, the trailing edge of the positive pulse in the voltage waveform is the time it takes for the leading edge of the reflected pulse to reach the starting end. This means that the positive pulse width is the time it takes for the pulse to travel back and forth between the sending end and the fault point. Its internal logic is as follows: Figure 8 (b) shown.

[0085] Figure 8 It shows that after the starting end sends a long pulse with a width of t2, its pulse leading edge is reflected by the fault point and reaches the starting end at time t1. According to the voltage waveform at the starting end, the relationship between the wave velocity v, the time t1 for the high-voltage pulse to travel back and forth between the starting end and the fault point, and the fault distance x can be obtained:

[0086] vt1=2x

[0087] Similarly, when the terminal emits a long pulse with a width of t2, the relationship between the wave velocity v, the time t1' for the high-voltage pulse to travel between the terminal and the fault point, and the fault distance x can be obtained based on the terminal voltage waveform:

[0088] vt1'=2(lx)

[0089] After eliminating the wave velocity, the corresponding fault distance calculation formula is as follows:

[0090]

[0091] Where l is the distance from the beginning to the end of the fault line, t1 is the trailing edge time of the positive pulse in the voltage waveform at the beginning, and t2 is the trailing edge time of the positive pulse in the voltage waveform at the end.

[0092] In general, reflection and transmission occur simultaneously at the fault point. It is only necessary to analyze the voltage waveform at the starting end to obtain the fault point location information. The principle can also be used Figure 3 Similarly, when the pulse width of the emitted pulse is large, the time it takes for the reflected pulse's leading edge to reach the measurement end may overlap with the duration of the emitted pulse. Therefore, it is necessary to first determine whether there is overlap between the pulses based on the measured voltage waveform. This can be classified into the following five situations (a)-(e) based on the voltage waveform at the beginning of the fault line:

[0093] (a) If the voltage waveform at the initial end is as follows Figure 9 As shown in (a), the positive pulse width is equal to the initial pulse width, and the one positive pulse and two negative pulses are independent of each other, indicating that there is no overlap between the incident pulse, the reflected pulse, and the transmitted pulse.

[0094] At this time, the time difference between the positive pulse leading edge and the first negative pulse leading edge is It is the time it takes for the pulse to travel back and forth between the sending end and the fault point; the time difference between the leading edge of the positive pulse and the leading edge of the second negative pulse It is the time it takes for a pulse to travel back and forth between the sending end and the terminal. Figure 9 (b) shows:

[0095] Figure 9 Indicates that the starting width is After the rectangular pulse, the leading edge of the pulse is reflected by the fault point. The arrival time of the reflected pulse at the fault point can be obtained according to the voltage waveform at the starting end. The relationship between (the first negative pulse leading edge) and the fault distance x satisfies:

[0096]

[0097] Similarly, the wave velocity v and the arrival time of the transmitted pulse after reflection at the terminal can be obtained based on the voltage waveform at the starting end. The relationship between (the second negative pulse leading edge) and the fault distance x satisfies:

[0098]

[0099] After eliminating the wave velocity, the fault distance x is calculated as follows:

[0100]

[0101] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first negative pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

[0102] (b) If the voltage waveform at the initial end is as follows Figure 10 As shown in (a), the positive pulse width is equal to the initial pulse width, and the negative pulse has three amplitude steps of different amplitudes due to overlap. At this time, the time difference between the positive pulse front and the negative pulse first amplitude step front is It is the time it takes for the pulse to travel back and forth between the sending end and the fault point; the time difference between the leading edge of the positive pulse and the leading edge of the second amplitude step in the negative pulse It is the time it takes for a pulse to travel back and forth between the sending end and the terminal. Its internal logic is as follows: Figure 10 (b) shown.

[0103] Figure 10 Indicates that the starting width is After the rectangular pulse, the leading edge of the pulse is reflected by the fault point. The arrival time of the reflected pulse at the fault point can be obtained according to the voltage waveform at the starting end. The relationship between the leading edge of the first amplitude step in the negative pulse and the fault distance x satisfies:

[0104]

[0105] Similarly, the wave velocity v and the time it takes for the transmitted pulse to reach the starting end after being reflected by the terminal can be obtained based on the voltage waveform at the starting end. The relationship between the second amplitude step front in the negative pulse and the fault distance x satisfies:

[0106]

[0107] After eliminating the wave velocity, the fault distance x is calculated as follows:

[0108]

[0109] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first amplitude step in the negative pulse of the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

[0110] (c) If the voltage waveform measured at the starting end is as follows Figure 11 As shown in (a), the positive pulse has two different amplitude steps and there are two separated negative pulses. The time difference between the leading edge of the positive pulse and the leading edge of the second amplitude step of the positive pulse is It is the time it takes for the pulse to travel back and forth between the sending end and the fault point; the time difference between the leading edge of the positive pulse and the leading edge of the second negative pulse It is the time it takes for a pulse to travel back and forth between the sending end and the terminal. Its internal logic is as follows: Figure 11 (b) shown.

[0111] Accordingly, Figure 11 Indicates that the starting width is After the long pulse, the pulse front is reflected by the fault point. The time it arrives at the starting end is obtained based on the voltage waveform at the starting end. The wave velocity v and the time it takes for the reflected pulse at the fault point to arrive at the starting end are obtained. The relationship between the leading edge of the second amplitude step in the positive pulse and the fault distance x satisfies:

[0112]

[0113] Similarly, the wave velocity v and the time it takes for the transmitted pulse to reach the starting end after being reflected by the terminal can be obtained based on the voltage waveform at the starting end. The relationship between (the second negative pulse leading edge) and the fault distance x satisfies:

[0114]

[0115] After eliminating the wave velocity, the fault distance x is calculated as follows:

[0116]

[0117] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

[0118] (d) If the voltage waveform measured at the starting end is as follows Figure 12 As shown in (a), the positive pulse has two different amplitude steps, and the negative pulse has three different amplitude steps due to overlap. At this time, the time difference between the leading edge of the positive pulse and the leading edge of the second amplitude step of the positive pulse is It is the time it takes for the pulse to travel back and forth between the sending end and the fault point; the time difference between the leading edge of the positive pulse and the leading edge of the second amplitude step in the negative pulse It is the time it takes for a pulse to travel back and forth between the sending end and the terminal. Its internal logic is as follows: Figure 12 (b) shown.

[0119] Accordingly, Figure 12 Indicates that the starting width is After the long pulse, the pulse front reaches the starting end at time after being reflected by the fault point. According to the voltage waveform at the starting end, the wave velocity v and the time when the reflected pulse at the fault point reaches the starting end can be obtained. The relationship between the leading edge of the second amplitude step in the positive pulse and the fault distance x satisfies:

[0120]

[0121] Similarly, the wave velocity v and the time it takes for the transmitted pulse to reach the starting end after being reflected by the terminal can be obtained based on the voltage waveform at the starting end. The relationship between the leading edge of the second amplitude step in the negative pulse and the fault distance x satisfies:

[0122]

[0123] After eliminating the wave velocity, the fault distance x is calculated as follows:

[0124]

[0125] Where, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

[0126] (e) If the voltage waveform measured at the starting end is as follows Figure 13 As shown in (a), the positive pulse of the initial voltage waveform has 2 to 3 different amplitude steps, and the negative pulse has two different amplitude steps. At this time, the time difference between the leading edge of the positive pulse and the trailing edge of the first amplitude step of the positive pulse is It is the time it takes for the pulse to travel back and forth between the sending end and the fault point; the time difference between the leading edge of the positive pulse and the trailing edge of the second amplitude step of the positive pulse It is the time it takes for a pulse to travel back and forth between the sending end and the terminal. Its internal logic is as follows: Figure 13 (b) shown.

[0127] Accordingly, Figure 13 Indicates that the starting width is After the long pulse, the pulse front is reflected by the fault point. The time it arrives at the starting end is obtained based on the voltage waveform at the starting end. The wave velocity v and the time it takes for the reflected pulse at the fault point to arrive at the starting end are obtained. The relationship between the trailing edge of the first amplitude step in the positive pulse and the fault distance x satisfies:

[0128]

[0129] Similarly, the wave velocity v and the time it takes for the transmitted pulse to reach the starting end after being reflected by the terminal can be obtained based on the voltage waveform at the starting end. The relationship between the trailing edge of the second amplitude step of the positive pulse and the fault distance x satisfies:

[0130]

[0131] After eliminating the wave velocity, the fault distance x is calculated as follows:

[0132]

[0133] Where, l is the distance from the beginning to the end of the fault line, is the trailing edge time of the first amplitude step of the positive pulse in the initial voltage waveform, It is the trailing edge time of the second amplitude step of the positive pulse in the initial voltage waveform.

[0134] In summary, the distribution network feeder fault distance measurement method designed by the present invention is relatively simple and accurate, and provides feeder fault distance measurement for distribution network systems with shorter lines. It is based on long pulses for measurement and can avoid the problem of excessive attenuation of high-frequency components of short pulses. At the same time, it solves the problems of inconsistent line wave speeds and long pulse overlap, and improves the ranging accuracy. It has good promotion prospects and application value.

[0135] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A distribution network feeder fault location method, characterized in that: Including steps: S1. Apply a high-voltage pulse to the fault line and collect the voltage waveform at the starting end of the fault line; S2. Analyze the reflection and transmission conditions at the fault point of the fault line based on the starting-end voltage waveform. If the fault point is totally reflected, proceed to step S3. If both reflection and transmission occur at the fault point, proceed to step S4. In step S2, the reflection and transmission conditions at the fault point of the fault line are determined based on the starting-end voltage waveform analysis, including the following steps: S21. If the voltage waveform at the initial end of the fault line is two pulses, one positive and one negative, then the fault point is a total reflection; S22. If the voltage waveform at the beginning of the fault line includes one positive pulse and two negative pulses, reflection and transmission occur simultaneously at the fault point; S3, applying high voltage pulses at the starting and ending points of the fault line respectively, measuring the line fault distance by analyzing the high voltage waveforms at both ends, and eliminating the influence of wave velocity on the measurement results to obtain the corresponding fault distance; In step S3, if the positive pulse width in the starting voltage waveform is smaller than the initial pulse width, the fault distance The calculation formula is as follows: in, is the distance from the beginning to the end of the fault line, is the trailing edge time of the positive pulse in the initial voltage waveform, is the trailing edge time of the positive pulse in the terminal voltage waveform; S4. Measure the line fault distance by analyzing the voltage waveform at the starting end of the fault line and eliminating the influence of the wave velocity on the measurement result to obtain the corresponding fault distance; In step S4, the voltage waveform at the initial end of the fault line is classified to obtain the following situations: (a) The initial voltage waveform includes one positive pulse and two negative pulses, and the width of the positive pulse is equal to the width of the initial pulse; (b) The positive pulse width in the initial voltage waveform is equal to the initial pulse width, and the negative pulse has three different amplitude steps due to overlap; (c) The positive pulse of the initial voltage waveform has two different amplitude steps and two separated negative pulses; (d) the positive pulse of the initial voltage waveform has two different amplitude steps, and the negative pulse has three different amplitude steps; (e) The positive pulse of the initial voltage waveform has 2 to 3 different amplitude steps, and the negative pulse has two different amplitude steps.

2. The distribution network feeder fault location method according to claim 1, characterized in that: In step S3, if the positive pulse width in the starting voltage waveform is equal to the initial pulse width, the fault distance The calculation formula is as follows: in, is the distance from the beginning to the end of the fault line, is the leading edge time of the negative pulse in the initial voltage waveform, is the leading edge time of the negative pulse in the terminal voltage waveform.

3. The distribution network feeder fault location method according to claim 1, characterized in that: In step S4, if the voltage waveform at the starting point is the above case (a), then the fault distance x The calculation formula is: in, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first negative pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

4. The distribution network feeder fault location method according to claim 1, characterized in that: In step S4, if the voltage waveform at the starting point is the above case (b), then the fault distance x The calculation formula is: in, l is the distance from the beginning to the end of the fault line, is the leading edge time of the first amplitude step in the negative pulse of the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

5. The distribution network feeder fault location method according to claim 1, characterized in that: In step S4, if the voltage waveform at the starting point is the above case (c), then the fault distance x The calculation formula is: in, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second negative pulse in the initial voltage waveform.

6. The distribution network feeder fault location method according to claim 1, characterized in that: In step S4, if the voltage waveform at the starting point is the above case (d), then the fault distance x The calculation formula is: in, l is the distance from the beginning to the end of the fault line, is the leading edge time of the second amplitude step of the positive pulse in the initial voltage waveform, It is the leading edge time of the second amplitude step in the negative pulse of the initial voltage waveform.

7. The distribution network feeder fault location method according to claim 1, characterized in that: In step S4, if the voltage waveform at the starting end is the above case (e), then the fault distance x The calculation formula is: in, l is the distance from the beginning to the end of the fault line, is the trailing edge time of the first amplitude step of the positive pulse in the initial voltage waveform, It is the trailing edge time of the second amplitude step of the positive pulse in the initial voltage waveform.

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