A method for fault location of a power transmission line by observing a traveling wave at a single point along the line

Abstract

The application relates to a power transmission line fault ranging method using a single observation point along a line to observe a traveling wave, and belongs to the technical field of power system protection. The application uses the fault traveling wave polarity characteristics caused by the topology that both ends of the power transmission line are multi-outlet lines, reads the recorded wave data collected by the current traveling wave observation point along the line and the installation position of the observation point, calibrates the wave head and extracts the same polarity wave head of the initial fault traveling wave; taking the initial fault traveling wave as a reference, based on the fixed time difference, the unique healthy section length characteristics are reflected, the first outgoing wave of the healthy section meeting the time difference condition is searched, the healthy section and the fault section are determined; taking the identified first outgoing wave of the healthy section as a reference, the maximum amplitude wave head in the subsequent wave is taken as the fault first reflected wave to calculate the relative distance from the fault to the observation point; on the basis of determining the fault section and the relative fault distance, the absolute fault distance from the fault to the first end of the line is converted, and the power transmission line fault ranging is realized.

Description

Technical Field

[0001] This invention relates to a method for fault location in power transmission lines that utilizes traveling wave observation at a single measuring point along the line, belonging to the field of power system protection technology. Background Technology

[0002] Transmission lines span vast geographical areas and are susceptible to external environmental factors such as lightning, storms, and hail, resulting in a relatively high probability of failure. Furthermore, with the increasing prevalence of high-voltage and high-capacity power systems, the system's tolerance and resilience to faults have significantly weakened. Faults in high-voltage, long-distance, and high-capacity transmission lines pose serious risks, making line inspection difficult and causing transmission line congestion that leads to severe losses. Accurate and timely fault location, rapid fault diagnosis, accelerated repair, reduced line outage time, and reduced transmission channel congestion are of paramount importance for improving power system stability and ensuring reliable and continuous power supply, thus promoting societal energy transformation and carbon emission reduction.

[0003] Distributed measuring points along transmission lines must be deployed in pairs and can only perform double-ended fault location that strictly relies on clock synchronization. They cannot operate independently after clock synchronization fails. Considering that in actual power production, distributed traveling wave (TW) devices installed on boundary towers or across different jurisdictions cannot perform independent fault location, they often require a paired TW device to assist in the measurement. Therefore, developing a transmission line fault location method that utilizes traveling wave observations from a single measuring point along the line, as a supplementary location method after clock synchronization failure at distributed measuring points, is of great value in improving the reliability of traveling wave fault location in transmission lines. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for fault location of transmission lines by observing traveling waves at a single measuring point along the line, so as to determine the first emitted wave of the sound section and identify the fault section, thereby effectively calculating the relative distance from the fault to the measuring point and completing the fault location.

[0005] The technical solution of this invention is: a method for fault location in transmission lines using traveling waves observed at single measuring points along the line. This method utilizes the polarity characteristics of the traveling waves caused by the multi-circuit topology at both ends of the transmission line. It reads the waveform data collected from the traveling wave measuring points along the line and the installation location of the measuring points, calibrates the wavefronts, and extracts the same polarity wavefront of the initial traveling wave of the fault. Using the initial traveling wave of the fault as a reference, and based on the unique characteristic of the healthy section length with a fixed time difference, it searches for traveling waves that meet the time difference conditions to determine the first emitted wave of the healthy section, thus identifying the healthy section and the fault section. Using the identified first emitted wave of the healthy section as a reference, it takes the wavefront with the largest subsequent amplitude as the first reflected wave of the fault to calculate the relative distance from the fault to the measuring point. Based on determining the fault section and the relative fault distance, it converts the absolute fault distance from the beginning of the line to achieve fault location in transmission lines.

[0006] Specifically, it includes:

[0007] Step 1: Read the fault waveform data and the measurement point installation location to obtain the same polarity waveheads of the initial traveling wave of the fault.

[0008] Step 2: Based on the initial traveling wave of the fault, and the unique characteristic of the length of the healthy section with a fixed time difference, search for the traveling wave that meets the specific time difference and same polarity conditions after the initial traveling wave of the fault to determine the first outgoing wave of the healthy section, thereby distinguishing between the healthy section and the faulty section.

[0009] Step 3: Using the first emitted wave of the healthy section as a reference, extract the wavefront with the largest amplitude among the subsequent wavefronts of the same polarity as the first reflected wave of the fault and calculate the relative fault distance from the measuring point.

[0010] Step 4: Based on the obtained fault section and relative distance to the fault, substitute both into the distance measurement formula to realize the distance measurement of transmission line faults.

[0011] Step 1 specifically refers to:

[0012] Step 1.1: Read the fault traveling wave data and the measurement point installation location. The wave data includes fault current traveling wave data and fault voltage traveling wave data. The measurement points are installed at unequal lengths, dividing the line into two unequal length sections L. A L B .

[0013] Step 1.2: Based on the read fault traveling wave data, perform fault line selection and phase selection and calibrate the wave head, and extract the arrival time of the same polarity wave head of the initial traveling wave of the fault.

[0014] Step 2 specifically includes:

[0015] Step 2.1: Traverse the wavefronts of the same polarity in the initial traveling wave of the fault, with the traversal interval being (t0, t0+2L / v).

[0016] Where v is the empirical wave velocity and L is the total length of the line.

[0017] Based on the time difference between the traversed wavehead and the initial traveling wave of the fault, match the fixed time difference reflected by the unequal length line segments read in Step 1.1 according to Equation (1), and determine whether there is a traveling wave that satisfies the fixed time difference and the same polarity condition after the initial traveling wave.

[0018]

[0019] In the formula, L k t is the length of the line segment, ε is the wavefront matching error, and t is the line segment length. i t0 is the arrival time of the current traversal wavehead, and t0 is the arrival time of the initial traveling wave of the fault.

[0020] If it exists, stop traversing and proceed to Step 2.2.

[0021] Otherwise, exit distance measurement.

[0022] Step 2.2: The wavefront that satisfies the fixed time difference condition in Step 2.1 is the arrival time t1 of the first emitted wave in the healthy section, and its matching line section is the healthy section L. s Then the faulty section L is identified. f and direction coefficient k.

[0023] Step 3 specifically refers to:

[0024] Step 3.1: Based on the first emitted wave of the healthy section, take the subsequent length 2L. f The wavefront with the largest amplitude in the / v data is the first reflected wave from the fault, where L f Let t2 be the length of the faulty section and mark its arrival time.

[0025] Step 3.2: Based on the time difference between the first reflected wave from the fault and the first emitted wave from the healthy section as described in Step 3.1, the relative distance from the fault to the measuring point is obtained as follows:

[0026] Δx=(t2-t1)v / 2 (2)

[0027] In the formula, t2 is the arrival time of the first reflected wavefront of the fault, and t1 is the arrival time of the first emitted wavefront of the healthy section.

[0028] Step 4 specifically refers to:

[0029] The fault section in Step 2.2 and the relative distance to the fault in Step 3.2 are obtained. These two values ​​are then substituted into the distance measurement formula to achieve fault location for transmission lines. The distance measurement formula is as follows:

[0030] x = L A +kv(t2-t1) / 2 (3)

[0031] Among them, L A t2 is the length of the first section of the line; k is the direction coefficient, k = -1 when the fault is determined to occur in the section before the measuring point along the line, and k = 1 when the fault is determined to occur in the section after the measuring point along the line; t2 is the arrival time of the first reflected wave of the fault, and t1 is the arrival time of the first emitted wave of the healthy section.

[0032] The beneficial effects of this invention are as follows: This invention comprehensively utilizes the certainty of the section length and the identifiability of the single-end subsequent traveling wave properties determined by the transmission network topology. The measurement point installation location is flexible, and a single measurement point can independently determine the fault section and distance, overcoming the shortcomings of traditional traveling wave distance measurement along the line, which can only be performed at both ends and must rely on clock synchronization. There are no dead zones at the beginning and end. Compared with traditional station-end traveling waves, the traveling wave along the line is less affected by transformers and secondary cables, has higher waveform quality, and is closer to the fault point, resulting in stronger observation capabilities for weak faults. It can serve as a supplement to existing traveling wave distance measurement, and can also independently serve as a line fault boundary indicator, with potential applications in distribution lines. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a 500kV local power transmission network in an embodiment of the present invention;

[0034] Figure 2 This is a fault current traveling wave waveform diagram in an embodiment of the present invention;

[0035] Figure 3 This is a diagram illustrating the specific implementation steps of Step 1 of the present invention;

[0036] Figure 4 This is a diagram illustrating the specific implementation steps of Step 2 of the present invention;

[0037] Figure 5 This is a diagram illustrating the specific implementation steps of Step 3 of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1: A current recording device based on a 1MHz sampling rate collected single-phase grounding fault data on a 500kV transmission line in a certain area at 16:03 on August 20, 2023. The line topology is as follows. Figure 1 As shown, the line is 116.17km long, and both busbars at both ends of the line are multi-circuit outgoing lines. The fault rate during manual inspection is 0.821km.

[0040] The specific implementation steps are as follows:

[0041] Step 1: Read the fault data and installation location of the traveling wave measurement points along the line, and obtain the wavefront calibration results of the traveling wave recording data to obtain the wavefronts of each polarity of the initial traveling wave of the fault. The specific implementation steps are as follows: Figure 2 As shown.

[0042] Step 1.1: Read the fault traveling wave data and the installation location of the measuring point. Divide the transmission line into L... A =45.034km, L B=71.136km, capturing 150 points before and 1131 points after the initial traveling wave mutation at the start of the fault. Due to the limited original waveform data from the actual traveling wave device, the actual data captured were the first 150 points and the last 864 points, totaling 1014 points of fault phase current data. The waveform is as follows. Figure 3 As shown.

[0043] Step 1.2: Based on the captured fault traveling wave data, use wavelet transform to calibrate the wavefronts and extract the arrival time series t of the same polarity wavefronts of the initial fault traveling wave. m .

[0044] Step 2: Using the initial traveling wave of the fault as a reference, and based on the unique characteristic of the healthy segment length with a fixed time difference response, search for traveling waves that satisfy the time difference condition to determine the first emitted wave of the healthy segment, in order to distinguish between the healthy segment and the faulty segment. The specific implementation steps are as follows: Figure 4 As shown.

[0045] Step 2.1: The time series set t extracted in Step 1.2 m In the middle, at t m The wavefronts are traversed within the interval (151, 790). Length matching is performed according to formula (1) based on the line segment length characteristics, with an error ε of 1 km and an empirical wave velocity v = 0.294 km / μs. There exists a subsequent wavefront that satisfies:

[0046] |71.136-(631-151)×0.294 / 2|=0.576<ε (1)

[0047] Matched the line segment L read in Step 1.1 B Once the wavefront that meets the fixed time difference condition is found, stop the search and proceed to Step 2.2.

[0048] Step 2.2: The wavefront that satisfies the fixed time difference condition in Step 2.1 is the arrival time of the first emitted wave in the healthy segment, t1 = 631 μs, and its matched L B The corresponding section is a healthy section, L A If the corresponding section is a faulty section, then the faulty section is determined to be L. A And the direction coefficient k = -1.

[0049] Step 3: Using the initial reflected wave of the intact section as a reference, extract the wavefront with the largest amplitude among subsequent wavefronts of the same polarity as the first reflected wave of the fault and calculate the relative fault distance from the measuring point. The specific implementation steps are as follows: Figure 5 As shown;

[0050] Step 3.1: Using t1 determined in Step 2.2 as a reference, determine the wavefront with the largest amplitude as the arrival time of the first reflected wave of the fault in the subsequent time series set of 306 points with a finite length, t2 = 931 μs.

[0051] Step 3.2: Based on the initial reflected wave of the fault determined in Step 3.1 and the initial emitted wave of the healthy section, calculate the relative fault distance Δx from the measuring point using formula (2):

[0052] Δx=(931-631)×0.294 / 2=44.1km (2)

[0053] Step 4: After obtaining the fault section and the relative distance of the fault, substitute them into the distance measurement formula (3) to realize the distance measurement of the transmission line fault.

[0054] x=45.034-(931-631)×0.294 / 2=0.934km (3)

[0055] This invention, based on the unique characteristic of the length of a healthy segment with a fixed time difference, searches for traveling waves that satisfy the time difference condition to determine the first emitted wave of a healthy segment, thus distinguishing between healthy and faulty segments. Furthermore, by using the first emitted wave of the healthy segment as a reference and selecting the wavefront with the most significant subsequent amplitude, single-end ranging of distributed measuring points can be achieved, avoiding the drawback that distributed measuring points must be arranged in pairs and cannot independently perform fault ranging at a single end.

[0056] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for fault location in transmission lines using traveling wave observation at a single measuring point along the line, characterized in that: Step 1: Read the fault waveform data and the measurement point installation location to obtain the same polarity wavefronts of the initial traveling wave of the fault; Step 2: Based on the initial traveling wave of the fault, and based on the unique characteristic of the length of the healthy section with a fixed time difference, search for the traveling wave that meets the specific time difference and same polarity conditions after the initial traveling wave of the fault to determine the first outgoing wave of the healthy section, so as to distinguish between the healthy section and the faulty section. Step 3: Using the first outgoing wave of the healthy section as the benchmark, extract the wavefront with the largest amplitude among the subsequent wavefronts of the same polarity as the first reflected wave of the fault and calculate the relative fault distance from the measuring point. Step 4: Based on the obtained fault section and relative distance to the fault, substitute both into the distance measurement formula to realize the fault distance measurement of the transmission line. Step 2 specifically includes: Step 2.1: Traverse the wavefronts of the same polarity in the initial traveling wave of the fault, with the traversal interval being (t0, t0+2L / v); Where v is the empirical wave velocity and L is the total length of the line; Based on the time difference between the traversed wavehead and the initial traveling wave of the fault, match the fixed time difference reflected by the unequal length line segments according to formula (1), and determine whether there is a traveling wave that satisfies the fixed time difference and the same polarity condition after the initial traveling wave. （1）； In the formula, L k t is the length of the line segment, ε is the wavefront matching error, and t is the line segment length. i t0 is the arrival time of the current traversed wavehead, and t0 is the arrival time of the initial traveling wave of the fault. If it exists, stop traversing and proceed to Step 2.2; Otherwise, exit distance measurement; Step 2.2: The wavefront that satisfies the fixed time difference condition is the arrival time t1 of the first emitted wave in the healthy section, and its matched line section is the healthy section L. s Then the faulty section L is identified. f and direction coefficient k.

2. The method for fault location of transmission lines using traveling waves observed at a single measuring point along the line as described in claim 1, characterized in that, Step 1 specifically refers to: Step 1.1: Read the fault traveling wave data and the measurement point installation location. The wave data includes fault current traveling wave data and fault voltage traveling wave data. The measurement points are installed at unequal lengths, dividing the line into two unequal length sections L. A L B ; Step 1.2: Based on the read fault traveling wave data, perform fault line selection and phase selection and calibrate the wave head, and extract the arrival time of the same polarity wave head of the initial traveling wave of the fault.

3. The method for fault location of transmission lines using traveling waves observed at a single measuring point along the line as described in claim 1, characterized in that, Step 3 specifically refers to: Step 3.1: Based on the first emitted wave of the healthy section, take the subsequent length 2L. f The wavefront with the largest amplitude in the / v data is the first reflected wave from the fault, where L f The length of the faulty section is given, and its arrival time t2 is also specified. Step 3.2: Based on the time difference between the first reflected wave from the fault and the first emitted wave from the healthy section, the relative distance from the fault to the measuring point is obtained as follows: （2）； In the formula, t2 is the arrival time of the first reflected wavefront of the fault, and t1 is the arrival time of the first emitted wavefront of the healthy section.

4. The method for fault location of transmission lines using traveling waves observed at a single measuring point along the line as described in claim 1, characterized in that, Step 4 specifically refers to: The fault location of the transmission line is achieved by substituting the fault section and the relative distance to the fault into the ranging formula: （3）； Among them, L A t2 is the length of the first section of the line, k is the direction coefficient, k=-1 when the fault is determined to occur in the section before the measuring point along the line, k=1 when the fault is determined to occur in the section after the measuring point along the line, t2 is the arrival time of the first reflected wave of the fault, and t1 is the arrival time of the first emitted wave of the healthy section.

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