CN102645616A - A method for addressing transmission line faults - Google Patents

Abstract

The invention discloses a fault addressing method for a transmission line, mainly relates the technical field of power grid detection and monitoring, and solves the problems of low accuracy and high cost of traditional addressing methods. According to the fault addressing method for the transmission line, by means of pilot frequency standing wave virtual method addressing, the advantages of other traditional methods and the transmission principle of waves, positions of wave troughs and wave crests of standing waves, which are formed on the transmission line, are different due to different frequency of the waves, the wave crests of the waves emerge right at the injection points of the signals by changing the frequencies of the waves, the length of the line can be calculated under the condition of known wave velocity due to the fixed wave speed on the line, and the positioning is more accurate. According to the fault addressing method for the transmission line, the manufactured instruments have pattern digitization interfaces and are small in volume, convenient to carry, low in cost, simple in operation, capable of achieving fault addressing in transformer substations, high in work efficiency, capable of saving more precious time and a large amount of manual labors, financial resources and material resources for electric power departments, and good in application and popularization values.

Description

A method for addressing transmission line faults

technical field

The invention relates to the technical field of grid operation fault diagnosis, in particular to a fault addressing method for transmission lines.

Background technique

At present, a large number of 35KV and above transmission lines in China are generally distributed in mountainous areas, mainly responsible for the transmission of electric energy. However, due to the fact that most of the lines are laid in remote mountainous areas, coupled with the frequent occurrence of various extreme natural disasters in recent years, if lightning, landslides, typhoon attacks, earthquakes, ice and snow and other natural disasters aggravate the possibility of transmission line failure and the aging of the line insulation system It is very difficult to distinguish, maintain and inspect the line fault distance.

In recent years, people have done a lot of research on transmission line fault detection methods. The representative methods are traveling wave method, impedance method, fault recording and GPS positioning methods. These methods have achieved different results in transmission line fault addressing. degree of progress.

The fault recording analysis method uses various electrical quantities recorded during the fault, and the technical personnel conduct comprehensive analysis afterwards to obtain the fault location. With the development of computer technology and artificial intelligence technology, fault recording analysis can be quickly completed by automated equipment. However, this method will be affected by the system impedance and the transition impedance of the fault point, which will lead to the decline of fault location accuracy.

Impedance method is divided into single-ended method and double-ended method. Although single-ended method is simple in principle, easy to use, low in equipment investment, and does not require additional communication equipment, the accuracy of single-ended impedance method is not high in practical applications, especially It is easily affected by the transition resistance of the fault point, the impedance of the opposite side system, and the load current. At the same time, because in the calculation process, the algorithm is often based on one or several assumptions, and these assumptions are often inconsistent with the actual situation, so there are principle errors that cannot be eliminated in the single-ended impedance method. The double-ended method uses the electrical information at both ends of the line for fault location to eliminate the influence of transition resistance in principle, but the disadvantages of the double-ended method are: large amount of calculation, large equipment investment, and additional synchronization and communication equipment.

The traveling wave method has higher positioning accuracy than the impedance method, but its reliability, anti-interference ability and adaptability are poor. In particular, due to the complex structure of distribution network lines and scattered loads, traveling waves produce very complex refraction and reflection at the connection points of each section of lines and each primary equipment, and the identification of traveling wave signals has been seriously affected. In addition, the extraction of traveling wave signals will also be affected by larger loads.

Contents of the invention

The object of the present invention is to provide a method for fault addressing of transmission lines with high reliability and accuracy and low cost.

The technical scheme adopted for realizing the purpose of the present invention is: a kind of method for transmission line fault addressing, adopts different frequency standing wave virtual method to carry out fault addressing, comprises the steps:

a. Measure and sample through the frequency sweep circuit;

b. Select the corresponding voltage level identifier according to the measured line voltage level to determine the wave velocity of the line under this voltage level;

c. Change the position of the marking line by controlling the left and right keys, and find the lowest frequency point where the trough occurs;

d. Combining with the analysis, the measured curve is compressed and enlarged in the direction of the frequency axis, that is, the x-axis, and the fineness of the measurement is adjusted;

e. Through the analysis of the mathematical model, the end of the line is an open-circuit disconnection or a short-circuit ground fault status identification and distance calculation data;

f. The distance from the fault point to the measurement point is L=0.25v/f calculated by the single-chip computer for the wave velocity design conversion under the known voltage level;

g. Determine the relationship between output signal voltage and frequency variation characteristics through the standing wave valley detection module.

The present invention is a fault addressing method for a transmission line, which adopts the different-frequency standing wave virtual method for fault addressing, and utilizes the principle of wave transmission to form a standing wave on the transmission line. Since the frequency of the wave is different, the trough of the standing wave The position of the wave crest is different. By changing the frequency of the wave, the trough of the wave appears exactly at the injection point of the signal. Since the wave velocity on the line is fixed, the length of the line can be calculated when the wave velocity is known. The method provided by the present invention only needs to carry out fault measurement on the line above 35KV in the power failure state in the substation, and the instrument manufactured by this method has the advantages of small size, convenient portability, low cost, and dual-purpose battery for AC and DC , With graphic and digital display functions, easy to operate. Detecting the faulty line in the substation avoids the time-consuming and labor-intensive work of the line inspectors and improves the work efficiency. It can accurately measure the distance to the fault, determine the faulty tower, shorten the troubleshooting time, reduce the repair cost, and improve The economic benefit is about 30% or more. For example, if each prefecture-level company handles two transmission line emergency repair tasks every year, the direct repair cost and indirect power loss will be 500,000 yuan, and the resulting loss will reach 1 million yuan, which is the most conservative calculation. At the same time, under the circumstances that the current power supply and power maintenance tasks are intensified, shortening the time to find faults in transmission lines will not only have considerable economic benefits but also obvious social benefits.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is the relationship diagram of VSWR and frequency change when the line is open circuit fault;

Figure 2 is a graph of the relationship between standing wave ratio and frequency when the line is short-circuited.

Detailed ways

When designing the measurement, the output terminal is connected to the fault phase overhead line with a lead wire, and the ground terminal is connected to the ground wire of the transformer. If there is a phase-to-phase short circuit fault in the overhead line, one phase can be output to the terminal and the other can be connected to the ground terminal.

a. Measurement sampling is performed through the frequency sweep circuit.

b. Select the corresponding voltage level identifier according to the measured line voltage level to determine the wave velocity of the line under this voltage level.

c. Change the position of the marking line by controlling the left and right keys to find the lowest frequency point where the trough occurs. As shown in Figure 1 and Figure 2: f0 is the frequency of the first standing wave point. In the analysis function state, use the left or right key to move the marking line, repeatedly adjust near the first standing wave point, and observe the standing wave ratio Variations to find the lowest point. At this time, the fault distance is L, the frequency of the first standing wave point is f, and the standing wave ratio is A.

d. Combining analysis, compress and amplify the measured curve in the direction of the frequency axis, that is, the x-axis, to adjust the fineness of the measurement; in order to find the minimum A value of the first standing wave point, the curve can be enlarged or compressed, for the best precision. After adjusting the fineness, enter the analysis state for analysis.

e. Through the analysis of the mathematical model, the end of the line is an open-circuit disconnection or short-circuit grounding fault status identification and data for distance calculation; after the sampling measurement is completed, the nature of the line fault is automatically judged as short-circuit or open-circuit. If the automatic judgment is wrong, the nature of fault judgment can be changed through short circuit/open circuit, and the distance L will change. If the line is an open circuit fault, the displayed curve is similar to the cosine curve, that is, the value of A changes from large to small as the frequency increases, as shown in Figure 1. If the line is a short-circuit fault, the displayed curve is similar to the sinusoidal curve, that is, the value of A changes from small to large and then small with the increase of frequency, as shown in Figure 2.

f. Calculate the wave velocity under the known voltage level by the single-chip computer to design and convert the distance from the fault point to the measurement point L=0.25v/f.

g. Determine the relationship between output signal voltage and frequency variation characteristics through the standing wave valley detection module. According to the test of specific line segment parameters, modify the wave velocity parameters of the overhead line in the program to ensure the measurement accuracy. When measuring a line with a known length L0, the user can measure the non-faulted phase length L1 and the faulted phase length L2 respectively, and the fault distance can be obtained by the following formula: Lx=L0×L2/L1.

According to the wave transmission theory and theoretical formula, when the fault point is closer to the test point, the frequency f0 when the first standing wave trough appears at the injection point is higher. When the fault point is too close, the value of f0 may not be measured. When the fault point is too far away from the test point, the value of f0 may only be a few hundred Hz. What we measure may not be the first standing wave point but the second , The third standing wave point, when the fault distance indicated by the first standing wave point in the curve waveform is greater than 50kM, accurate measurement can be performed by selecting a gear greater than 50kM.

The method provided by the present invention only needs to carry out fault measurement on the line above 35KV in the power failure state in the substation, and the instrument manufactured by this method has the advantages of small size, convenient portability, low cost, and dual-purpose battery for AC and DC , With graphic and digital display functions, easy to operate. Detecting the faulty line in the substation avoids the time-consuming and labor-intensive work of the line inspectors and improves the work efficiency. It can accurately measure the distance to the fault, determine the faulty tower, shorten the troubleshooting time, reduce the repair cost, and improve The economic benefit is about 30% or more. For example, if each prefecture-level company handles two transmission line emergency repair tasks every year, the direct repair cost and indirect power loss will be 500,000 yuan, and the resulting loss will reach 1 million yuan, which is the most conservative calculation. At the same time, under the circumstances that the current power supply and power maintenance tasks are intensified, shortening the time to find faults in transmission lines will not only have considerable economic benefits but also obvious social benefits.

Claims (1)

1. A method for transmission line fault addressing, characterized in that: adopting different frequency standing wave virtual method to carry out fault addressing, comprising the steps of: a. Measure and sample through the frequency sweep circuit; b. Select the corresponding voltage level identifier according to the measured line voltage level to determine the wave velocity of the line under this voltage level; c. Change the position of the marking line by controlling the left and right keys, and find the lowest frequency point where the trough occurs; d. Combining with the analysis, the measured curve is compressed and enlarged in the direction of the frequency axis, that is, the x-axis, and the fineness of the measurement is adjusted; e. Through the analysis of the mathematical model, the end of the line is an open-circuit disconnection or a short-circuit ground fault status identification and distance calculation data; f. The distance from the fault point to the measurement point is L=0.25v/f calculated by the single-chip computer for the wave velocity design conversion under the known voltage level; g. Determine the relationship between output signal voltage and frequency variation characteristics through the standing wave valley detection module.

Images