High-voltage transmission line fault location method based on new double-end distance measurement algorithm

Abstract

The invention discloses a high-voltage transmission line fault location method based on a new double-end distance measurement algorithm, and is applied to the field of power systems and automation thereof. According to the method, fault current signals are processed, so that the purpose of detecting an initial traveling wave head is achieved, and fault distance measurement is carried out according to the initial moment when the wave head reaches two end points of a line. Firstly, dynamic short-circuit current is measured without distortion through a Rogowski current transformer; then, the signal is decoupled through Karenbauer transformation; then, EMD (empirical mode decomposition) mode decomposition is carried out on the decoupled line mode current signal; then, calculating an instantaneous energy spectrum of imf1 by using a Teager energy operator, and detecting a traveling wave head; and finally, fault distance measurement is performed by using a new double-end distance measurement algorithm. Experimental results show that the wave head can be detected more accurately by adopting a mode of combining EMD and an energy operator. Meanwhile, a novel double-end distance measurement algorithm is adopted, the wave velocity is ingeniously simplified, and the distance measurement precision and the calculation speed are improved.

Description

Technical Field

[0001] The present application belongs to the field of power system automation, and more specifically, to a method for locating the distance of a high-voltage transmission line fault. Background Art

[0002] The rapid development of various industries in my country, especially the development of industry, has increased the demand for resources, especially the demand for electric power resources. The power system is developing in the direction of ultra-high voltage, large power grid and automation. The increase in voltage level makes the safe and reliable operation of the power system increasingly important. Local power outages caused by faults or even power outages in the entire region will have serious consequences for the production and operation of other sectors of the national economy. Transmission lines bear the heavy responsibility of transmitting electric energy and are the place where most faults occur in the power system. Transmission lines have long spans and are difficult to troubleshoot, so fault ranging technology is of great significance for quickly repairing faults and ensuring reliable power supply. The line protection fault ranging function is fast and concise, and can output the ranging results in the first time.

[0003] Transmission line fault location is a technical way to improve the reliability of power supply in the power system and an important means to promote the safe and stable operation of the power grid. After a fault occurs, the fault site should be quickly located according to the operating procedures, and the fault should be removed as quickly as possible to ensure that the output capacity can maintain the stable operation of the main power grid. Rapidly locating transmission line faults is of great significance, which undoubtedly improves the reliability, economy and safety of power system operation, while reducing the cost of blind maintenance.

[0004] The commonly used methods in engineering are still manual line inspections and field tests, which are time-consuming and laborious. In terms of theoretical research, some literature has proposed a traveling wave distance measurement scheme using a small number of measuring points; although it uses fewer measuring points, due to the presence of a large number of branches, the wave head of the characteristic traveling wave is difficult to identify, and the traveling wave propagates rapidly, making it very difficult to accurately measure the propagation time. Some researchers have improved the single-ended impedance method and can complete the distance measurement of the collector line using only one measuring point; however, it sets some assumptions, so the practicality of the method is still unclear, and this method requires fault assumptions to be made section by section, and the application of the method is relatively cumbersome and complicated. It can be seen that there is still a lack of economical, effective and simple fault distance measurement methods. Summary of the invention

[0005] The purpose of the present invention is to provide a method for locating a high-voltage transmission line fault in view of the above-mentioned defects of the prior art.

[0006] To solve the above-mentioned shortcomings, the technical route adopted by the present invention is:

[0007] A method for locating a high-voltage transmission line fault, comprising:

[0008] Construct a standard short-circuit signal and use PSCAD / EMTD simulation to build a simulation model consistent with the actual parameters.

[0009] The simulation model was constructed using PSCAD / EMTD simulation software. First, the line was divided into sections, each section was labeled, and a fault was set at the midpoint of each section. After the simulation, the signal of 0.25 power frequency cycle after the fault was recorded at the measuring point on the bus. This time period can ensure that the entire transient process is completed and the three-phase sequence of the fault signal is obtained.

[0010] Decouple the ideal current signal and release the coupling relationship between the three-phase currents.

[0011] Since the simulated signals are mutually coupled, it is necessary to decouple the coupling relationship. Common decoupling methods include Karen Bell transformation, phase sequence transformation, etc. Considering the influence of factors such as calculation speed, the simple transformation should be selected first. Because the three-order transformation involves relatively complex vector operations, the Karen Bell transformation is used for analysis and calculation, which can quickly and efficiently decouple. The transformation decoupling matrix is ​​as follows:

[0012]

[0013] Compared with other simulation software, the electromagnetic transient calculation program used in PSCAD / EMTD can effectively reflect the transient transformation process after the entire fault process. The simulation step size also has a significant impact on the transient solution. Considering the actual operation and traveling wave transmission conditions, it is reasonable to use a simulation step size of 1us.

[0014] Get the actual fault current signal.

[0015] The fault current signal sequence is extracted according to the actual power grid short circuit.

[0016] Decouple the actual current signal.

[0017] The decoupling method used is consistent with the standard fault signal decoupling method.

[0018] The actual signal and the fault signal are decomposed into three layers with db6 as the wavelet basis to obtain the energy distribution sequence.

[0019] There are many ways to decompose faults, but the more commonly used decomposition methods for short-circuit faults are EMD, VMD, wavelet decomposition, and wavelet packet decomposition. However, the wavelet decomposition algorithm generally used in the traveling wave fault algorithm after a short circuit is more effective when the fault arrival time is selected. The defect of wavelet decomposition is that it only decomposes low-frequency signals and does not decompose high-frequency signals. However, the high-frequency signal after a short circuit is the frequency band where the traveling wave signal is located, which highlights the shortcomings of wavelet decomposition. To address this shortcoming, the better algorithm currently available is the wavelet packet algorithm. The outstanding feature of the wavelet packet algorithm is that it also decomposes the high-frequency band and can effectively extract the fault traveling wave signal.

[0020] The wavelet packet transform decomposition algorithm has the following steps:

[0021] The ratio of wavelet packet information to energy entropy:

[0022]

[0023] Energy calculation formula:

[0024]

[0025] The information entropy calculation formula is as follows:

[0026]

[0027] The energy density probability calculation method is as follows:

[0028]

[0029] According to the above calculation method, the wavelet packet decomposition basis is optimized, and the db series wavelets, sym series wavelets, and coif series wavelets are selected. According to the above calculation method, the ratio of the fault signal is calculated, and the wavelet with the largest ratio is selected as the decomposition basis to decompose the fault signal, so that the characteristics of the fault signal can be effectively extracted and amplified. After calculation, it is found that the ratio of the db6 wavelet basis is the largest among them, so this basis is selected as the decomposition basis.

[0030] Construct the entropy calculation formula for fault conditions and standard short-circuit conditions.

[0031] The energy normalization sequence of the fault signal decomposition sequence of the i-th segmented standard fault signal at the busbar measuring point is as follows:

[0032] p 11 , p 12 ,…,p 18

[0033] The sequence normalized energy of the actual fault sequence decomposition is as follows:

[0034] p1, p2, …, p8

[0035] After obtaining the above two quantities, the calculation is performed according to the similarity of energy entropy. The calculation formula for n fault sections is as follows:

[0036]

[0037] Step 1: Perform Karen Bell transform on the signal.

[0038] Step 2: Perform wavelet packet transform on the signal mode 1 component of the fault step 2 to obtain the energy distribution sequence.

[0039] Step 3: Calculate the similarity entropy between the standard signal and the actual fault signal.

[0040] Step 4: Determine the section where the fault is located.

[0041] The present application discloses a method for locating faults in high-voltage transmission lines based on a new two-terminal ranging algorithm, which is applied to the field of power systems and automation thereof. The method processes the fault current signal to thereby achieve the purpose of detecting the initial traveling wave head, and uses the initial moment when the head reaches both ends of the line for fault ranging. First, the dynamic short-circuit current is measured without distortion by a Roche current transformer; then, the signal is decoupled by Karenbauer transformation; then, the decoupled line mode current signal is subjected to EMD modal decomposition; then, the instantaneous energy spectrum of imf1 is calculated by the Teager energy operator to detect the traveling wave head; finally, the new two-terminal ranging algorithm is used for fault ranging. Experimental results show that the wave head can be detected more accurately by combining EMD and energy operators. At the same time, the new two-terminal ranging algorithm is used to cleverly simplify the wave velocity, thereby improving the ranging accuracy and calculation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Attached Figure 1 It is the identification flow chart of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the examples of the present invention. Obviously, the examples described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Referring to the accompanying drawings, a schematic flow chart of a method for locating a fault in a power transmission line disclosed in an embodiment of the present invention is shown.

[0045] In this embodiment, from acquiring fault information to finally locating the fault distance, there are the following steps:

[0046] Step 1: Use the impedance channel or HFCT channel to collect sample signals, and use PSCAD / EMTDC to establish the fault sequence of the standard short-circuit signal at the busbar measurement point.

[0047] Step 2: Measure the dynamic short-circuit current without distortion using a Rogowski current transformer.

[0048] Step 3: Decouple the signal through Karenbauer transformation.

[0049] Step 4: Perform EMD modal decomposition on the decoupled line mode current signal.

[0050] Step 5: Use the Teager energy operator to calculate the instantaneous energy spectrum of imf1.

[0051] Step 6: Detect the traveling wave head.

[0052] Step 7: Use the new dual-terminal ranging algorithm to perform fault distance measurement.

[0053] Step 8: Determine the section where the fault is located.

[0054] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A method for locating faults in high-voltage transmission lines based on a new double-terminal ranging algorithm, characterized in that: include: Obtaining fault current signals of high-voltage transmission lines; Perform signal decoupling to release the coupling relationship between the three-phase currents; Detect the traveling wave head, perform empirical mode decomposition on the traveling wave component of the line mode current, and solve the initial time when the traveling wave reaches the endpoint through the instantaneous energy spectrum of the modal component; Fault distance measurement uses the time when the double-ended initial traveling wave reaches the endpoints, the initial fault time, and the horizontal distance between the two end points of the transmission line to calculate the fault distance.

2. The detection traveling wave head according to claim 1, characterized in that: Instantaneous energy spectrum detection using empirical mode decomposition and Teager energy operator solution.

3. The fault distance measurement according to claim 1, characterized in that: The fault location is measured using the time when the initial traveling wave reaches both ends, the initial fault time and the horizontal distance between the two end points of the line.

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