Power transmission line fault distance measurement method based on double-end voltage fault component

Abstract

The invention discloses a power transmission line fault distance measurement method based on double-end voltage fault components. According to the method provided by the invention, the power transmission network is simplified through the equivalent circuit, so that the fault position can be quickly and accurately analyzed; according to the method disclosed by the invention, fault phase selection is realized by utilizing the measured transient voltage under the condition of not considering the ground capacitance and conductance of the line; according to the method, the result precision is not influenced by the change of the transition resistance and the impedance of the opposite-end system, the fault positioning accuracy of the power transmission line is improved, and the method has good universality.

Description

Technical Field

[0001] The present invention relates to the field of power transmission, and more particularly to a method for fault location measurement of a power transmission line based on a double-terminal voltage fault component. Background Art

[0002] With the rapid development of my country's national economy and the increasing demand for electricity, various faults are inevitable in high-voltage transmission lines, which have brought serious harm and impact to the normal operation and reliable power supply of the entire power system. Therefore, studying how to quickly and accurately complete fault phase selection in a vast power grid is of great practical significance for quickly isolating and promptly repairing faulty lines to ensure the safe and reliable operation of the power grid.

[0003] When a short circuit occurs in a large-scale power grid, the transient state is short-lived but contains rich fault information, which makes it possible to quickly and accurately locate the short circuit fault in the power grid. In recent years, the structure and function of the Wide Area Measurement System (WAMS) in my country's power grid have been increasingly improved.

[0004] At present, the main methods for fault phase selection based on wide area power grid operation data collected by wide area measurement systems are:

[0005] Traveling wave method: When a high-voltage transmission line fails, a transient traveling wave generated at the fault point propagates along the transmission line to the surrounding area. Traveling wave fault location was created in the 1940s. Because the speed of traveling waves in the power grid is close to the speed of light and is relatively stable, people gradually realized that accurate fault location can be achieved by measuring the propagation time of transient traveling waves between the fault point and the fault line bus. However, its significant disadvantages are that the positioning results are unreliable and there are problems such as high hardware costs;

[0006] Fault analysis method: When the line parameters and system operation mode are known, when a short circuit fault occurs in the line, the fault distance is calculated using the functional relationship between the measured voltage and current at the busbar and the measuring point and the fault point. The fault analysis method can be divided into the fault equation solving method, the time domain method and the search iteration method. However, the fault analysis method has high requirements on the filtering capacity of the filtering device, and there is also the problem of difficulty in identifying pseudo roots.

[0007] In addition, the invention patent "Analysis method of line parameters and fault disturbances in power grid" (patent application number: 201210592462.8) has proposed that among the possible fault lines connected with the maximum voltage disturbance, the transmission line with the smallest line attenuation rate is the fault line. However, the phase selection method has a large error. When the equivalent impedances of the lines on both sides of the fault line are different, it is easy to mistakenly judge the normal line with a large equivalent impedance as the fault line. At the same time, most of the transmission lines in the high-voltage power grid are operated in a ring network mode. This type of phase selection method is only for radial lines, without considering the actual structure of the power grid. The invention patent "Power grid system containing a ring network and fault line judgment method" (patent application number: 2015103197459) uses transient voltage and current to select fault phases, but the current transformer is easy to saturate, the error is large, and the hardware cost is very high. In addition, it is difficult to accurately locate the fault at the transformer with the existing patent technology.

[0008] Therefore, there is still a lack of a method in the art that can accurately and quickly locate the fault of a high-voltage transmission line. Summary of the invention

[0009] The purpose of the present invention is to provide a method for fault location of a transmission line based on a double-terminal voltage fault component; the method of the present invention is not affected by changes in transition resistance and opposite-end system impedance on the accuracy of the result, improves the accuracy of fault location of the transmission line, and has good versatility.

[0010] The present invention provides a method for fault location of a power transmission line based on a double-terminal voltage fault component, the method comprising:

[0011] (1) obtaining voltages at different locations in the transmission line;

[0012] (2) obtaining voltage disturbance curves at different locations in the transmission line according to the voltage;

[0013] (3) in response to the voltage peak point of the voltage disturbance amount curve being less than a first threshold, determining that no fault has occurred at the location; in response to the voltage peak point of the voltage disturbance amount curve being above the first threshold, determining that a fault disturbance has occurred in the power grid, and performing fault distance measurement by the following method:

[0014] (3.1) Determining a suspected fault line: determining a suspected measuring point corresponding to the maximum value of the peak value of the voltage disturbance curve, the transmission line connected to the suspected measuring point is the suspected fault line, and the transmission lines other than the suspected fault line are normal lines;

[0015] (3.2) Determine the faulty line from the suspected faulty lines:

[0016] (3.2.1) Equivalent line: With the suspected measuring point as the center point, the power grid is equivalent to a straight line, wherein the center point is on the straight line, the equivalent length of the first side of the suspected measuring point is l1, the equivalent length of the second side of the suspected measuring point is l2, the equivalent voltage change rate of the normal line on the first side of the suspected measuring point is ρ1, and the equivalent voltage change rate of the normal line on the second side of the suspected measuring point is ρ2;

[0017] (3.2.2) Determining the fault occurrence side: when ρ1l1>ρ2l2, a fault occurs on the first side of the suspected measuring point; when ρ1l1=ρ2l2, a fault occurs at the suspected measuring point; when ρ1l1<ρ2l2, a fault occurs on the second side of the suspected measuring point;

[0018] (3.2.2) The distance x from the fault point to the suspected measuring point:

[0019] In another preferred example, the transmission line is divided into a radial line and a ring line.

[0020] In another preferred example, for the radial line, the voltage change rate of one or more sections of the transmission line between the normal measuring points on the first side of the suspicious measuring point is selected as ρ1; the voltage change rate of one or more sections of the transmission line between the normal measuring points on the second side of the suspicious measuring point is selected as ρ2.

[0021] In another preferred example, for the radial line, the sum of all transmission lines on the first side of the suspicious measuring point is l1; the sum of all transmission lines on the second side of the suspicious measuring point is l2.

[0022] In another preferred embodiment, for the ring line, when the suspected measuring point is connected to a plurality of transmission lines, the process (3.2) is repeated until the fault location and the fault distance are determined.

[0023] In another preferred example, the voltage quantities at different positions are collected by voltage transformers installed at different positions in the transmission line.

[0024] In another preferred example, in (2), the voltage disturbance curve at different positions in the transmission line is obtained by extracting the maximum and minimum values ​​of the voltage in (1), fitting them into an envelope curve, and adding and averaging them.

[0025] In another preferred example, the method further includes verifying the fault occurrence side through the x value: when x is less than 0, the transmission line on the first side of the suspected measuring point is a faulty line; when x is equal to 0, there is a fault at the suspected measuring point; when x is greater than 0, the transmission line on the second side of the suspected measuring point is a faulty line.

[0026] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 is a flow chart of a method for fault location of a power transmission line based on a double-terminal voltage fault component in an example of the present invention;

[0029] Figure 2 is a radial circuit diagram in an example of the present invention;

[0030] Figure 3 yes Figure 2 Equivalent circuit diagram of

[0031] Figure 4 is a ring circuit diagram in one embodiment of the present invention;

[0032] Figure 5 yes Figure 4 Equivalent circuit diagram of . DETAILED DESCRIPTION

[0033] After extensive and in-depth research and a large number of screenings, the inventors have developed for the first time a method for fault distance measurement of a transmission line based on a double-terminal voltage fault component; the method proposed in the present invention simplifies the transmission network through an equivalent circuit, and can thus quickly and accurately analyze the fault location; the method of the present invention uses the measured transient voltage quantity to achieve fault phase selection without considering the line-to-ground capacitance and conductivity; the method is not affected by the change in transition resistance and opposite-end system impedance, thereby improving the accuracy of fault location of the transmission line and having good versatility, and the present invention is completed on this basis.

[0034] the term

[0035] As used in this article, the term "transient component" refers to the electrical quantity generated by energy storage elements such as inductors and capacitors in the network when the system network structure changes; it decays exponentially and no longer exists after the transition process ends.

[0036] As used herein, the term "fault phase selection" means that when a transmission line fault occurs, the protection device can not only measure the fault distance, but also select the fault phase, that is, fault phase selection.

[0037] As used herein, the term "ring network" refers to a system in which nodes are connected together through branches to form a ring, and the ring formed by the nodes and branches as a whole constitutes a "ring network".

[0038] As used herein, the terms “voltage change rate”, “line decay rate”, etc. may be used interchangeably.

[0039] The main advantages of the present invention include:

[0040] (a) The accuracy of the results is not affected by changes in transition resistance and impedance of the opposite end system;

[0041] (b) Improve the accuracy of fault location of transmission lines;

[0042] (c) It has good versatility.

[0043] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, the accompanying drawings are schematic diagrams, so the device and apparatus of the present invention are not limited by the size or ratio of the schematic diagrams.

[0044] It should be noted that in the claims and description of this patent, 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 sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0045] Example

[0046] The transient component generated when a high-voltage transmission line has a short-circuit fault contains a large amount of fault information, including line length, line parameters, fault distance and fault time. According to the superposition principle, the network after the short circuit can be equivalent to two parts: the normal state and the disturbance component network. The disturbance component network is a network under the action of a disturbance voltage source (the voltage source is equal to the voltage at the short-circuit point under normal conditions and opposite in direction). In the case of a short-circuit fault, the disturbance component generated under the action of a single disturbance voltage source contains two components: the fundamental frequency component and the attenuation disturbance amount.

[0047] For the wide area power grid operation data collected by the wide area measurement system, the flow chart of the method for fault location of a transmission line based on a two-terminal voltage fault component (voltage fault component, i.e., voltage peak value) of this embodiment is as follows: Figure 1 shown.

[0048] The method includes:

[0049] (1) Use voltage transformers installed at different locations in the transmission line to collect the voltage at that location and transmit it to the measuring device unit in the electronic room through the OPGW communication wire;

[0050] (2) The measuring device unit extracts the maximum and minimum values ​​of each voltage quantity and fits them into an envelope curve, and the curve after adding and taking the average value is the voltage disturbance quantity curve at different positions in the transmission line;

[0051] (3) Based on the extracted voltage disturbance curve, first determine whether a short-circuit fault disturbance occurs in the power grid; if the voltage peak point of the voltage disturbance curve is less than the preset threshold, that is, U max <ε, then there is no fault in the power grid; otherwise, a fault disturbance occurs in the power grid, and step (4) is executed;

[0052] (4) Determine the fault line;

[0053] The following uses radial lines and ring lines as examples to explain how to determine the faulty line.

[0054] The method of determining the fault line of the radial line is as follows: first determine the measuring point corresponding to the maximum value of the peak value of the voltage disturbance among all measuring points, and the line connected to it is the possible fault line; take the measuring point with the maximum peak value of the disturbance as the reference, simplify the network diagram, and compare the relationship between the voltage change rate and the equivalent length of the normal transmission lines on both sides of the fault to determine the fault line. The simplification of the equivalent length of the line is consistent with the line impedance relationship.

[0055] Among them, the voltage change rate ρ mn (Unit: V / m) is expressed as

[0056]

[0057] Where Um max 、Un max --------The peak value of the voltage disturbance at the two end measuring points (measuring point m and measuring point n) on the transmission line, unit: V;

[0058] l mn ----------The length of the transmission line between measuring point m and measuring point n, unit: m.

[0059] like Figure 2 As shown, measuring points a, b, c, d, e, and f are connected in sequence to form a radial line. Line L on the radial line cd A fault occurs at the location. Six voltage transformers are used to collect voltages at different measuring points. The voltage disturbance at the measuring point is extracted and the peak value of the disturbance is compared. The peak value extracted from measuring point c or measuring point d is the largest. This example uses the peak value extracted from measuring point c as an example. Then we can analyze that the transmission line L bc and L cd is a possible fault line. Taking the measuring point c as the reference, the equivalent length of the line is Figure 3 As shown in the figure, l1' and l2' are the equivalent lengths of the lines on the left and right sides of the measuring point C, respectively, where l1' = l ab +l bc ; l2' = l cd +l de +l ef , where l ab , l bc , l cd , l de and l ef Decibel indicates the transmission line L ab , L bc , L cd , L de and L ef Select the transmission line L ab The voltage change rate ρ ab and transmission line L de The voltage change rate ρ de The magnitudes of represent the voltage change rates of the transmission lines on the left and right sides of the fault, that is, ρ1'=ρ ab ; ρ2'=ρ de If the voltage change rate and equivalent length of the line satisfy ρ1'l1'>ρ2'l2', the line on the left side of the measuring point c is faulty, that is, the transmission line L bc Fault; When the voltage change rate and equivalent length of the line satisfy ρ1'l1'=ρ2'l2', there is a fault at the measuring point c; When the voltage change rate and equivalent length of the line satisfy ρ1'l1'>ρ2'l2', there is a fault on the line to the right of the measuring point c, that is, the transmission line L cd Fault.

[0060] In order to further realize the accurate location of the fault point, it is assumed that the distance from the fault p to the measuring point c is x'. We know that the expression of x' is

[0061] The specific method of determining the fault line of the ring line is: first determine the measuring point corresponding to the maximum peak value of the voltage disturbance among all measuring points, and the line connected to it is the possible fault line. Figure 4 This is a schematic diagram of fault location on a ring line. Figure 4 In the figure, measuring points c, d and f are connected to form a ring loop, where measuring point e is connected to measuring point d, measuring points a and b are connected, and measuring point b is connected to measuring point c, and measuring point h is connected to measuring point f. Seven voltage transformers are used to collect voltages at different measuring points, extract voltage disturbances at the measuring points, and compare the peak values ​​of the disturbances. The peak value extracted from measuring point c or measuring point f is the largest. This example uses the peak value extracted from measuring point c as an example. It can be analyzed that the transmission line L bc , L cd and L cf is a possible fault line. We assume that the transmission line L cf When a short circuit occurs, the distance from the fault point p to the measuring point c is x. The equivalent schematic diagram of the line is as follows: Figure 5 As shown in Figure 1, l1 and l2 are the equivalent lengths of the ring line after star network transformation.

[0062]

[0063]

[0064]

[0065]

[0066] Where l ce , l ed , l cd , l df , l ac , l ef , l fh and l cf Respectively represent transmission lines

[0067] L ce , L ed , L cd , L df , L ac , L ef , L fh and L cf Length.

[0068] Similar to the radial line, ρ1 and ρ2 represent the voltage change rate of the transmission lines on the left and right sides of the fault after simplification, that is, the transmission line L ab The voltage change rate ρ ab , Transmission Line L de The voltage change rate ρ de and transmission line L fh The voltage change rate ρ fh The related representation after the star network transformation, where When ρ2l2<ρ1l1, the transmission line L cf Assume that the transmission line L is a normal line. bc or L cd Fault recalculation; when ρ2l2=ρ1l1, there is a fault at the measuring point c; when ρ2l2>ρ1l1, the transmission line L cf is the fault line. The distance x from the fault point p to the measuring point c is expressed as

[0069] In the transmission line L cf Assuming that the transmission line L is a normal line, bc When a short circuit occurs, the distance from the fault point p to the measuring point b is x. l1 and l2 are the equivalent lengths of the ring line after star network transformation.

[0070]

[0071] l1=l ab .

[0072] Similar to the radial line, ρ1 and ρ2 represent the voltage change rate of the transmission lines on the left and right sides of the fault after simplification, that is, the transmission line L ab The voltage change rate ρ ab , Transmission Line L dc The voltage change rate ρ dc and transmission line L cf The voltage change rate ρ cf Indicates that, ρ1=ρ ab ; ρ2=ρ dc +ρ cf If ρ2l2>ρ1l1, it means that the transmission line L bc Fault, otherwise the transmission line L cd Fault. The distance x from the fault point f to the measuring point b is expressed as

[0073] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for fault location of a transmission line based on a double-terminal voltage fault component, characterized in that: The method comprises: (1) obtaining voltages at different locations in the transmission line; (2) obtaining voltage disturbance curves at different locations in the transmission line according to the voltage; (3) in response to the voltage peak point of the voltage disturbance amount curve being less than a first threshold, determining that no fault has occurred at the location; in response to the voltage peak point of the voltage disturbance amount curve being above the first threshold, determining that a fault disturbance has occurred in the power grid, and performing fault distance measurement by the following method: (3.1) Determining a suspected fault line: determining a suspected measuring point corresponding to the maximum value of the peak value of the voltage disturbance curve, the transmission line connected to the suspected measuring point is the suspected fault line, and the transmission lines other than the suspected fault line are normal lines; (3.2) Determine the faulty line from the suspected faulty lines: (3.2.1) Equivalent line: With the suspected measuring point as the center point, the power grid is equivalent to a straight line, wherein the center point is on the straight line, the equivalent length of the first side of the suspected measuring point is l1, the equivalent length of the second side of the suspected measuring point is l2, the equivalent voltage change rate of the normal line on the first side of the suspected measuring point is ρ1, and the equivalent voltage change rate of the normal line on the second side of the suspected measuring point is ρ2; (3.2.2) Determining the fault occurrence side: when ρ1l1>ρ2l2, a fault occurs on the first side of the suspected measuring point; when ρ1l1=ρ2l2, a fault occurs at the suspected measuring point; when ρ1l1<ρ2l2, a fault occurs on the second side of the suspected measuring point; (3.2.2) The distance x from the fault point to the suspected measuring point:

2. The method according to claim 1, characterized in that The transmission lines are divided into radial lines and ring lines.

3. The method according to claim 2, characterized in that For the radial line, the voltage change rate of one or more sections of the transmission line between the normal measuring points on the first side of the suspicious measuring point is selected as ρ1; the voltage change rate of one or more sections of the transmission line between the normal measuring points on the second side of the suspicious measuring point is selected as ρ2.

4. The method according to claim 2, characterized in that For the radial line, the sum of all transmission lines on the first side of the suspicious measuring point is l1; the sum of all transmission lines on the second side of the suspicious measuring point is l2.

5. The method according to claim 2, characterized in that For the ring line, when the suspected measuring point is connected to a plurality of transmission lines, the process (3.2) is repeated until the fault location and the fault distance are determined.

6. The method according to any one of claims 1 to 5, characterized in that The voltage quantities at different positions are collected by voltage transformers installed at different positions in the transmission line.

7. The method according to any one of claims 1 to 5, characterized in that In (2), the voltage disturbance curve at different positions in the transmission line is obtained by extracting the maximum and minimum values ​​of the voltage in (1), fitting them into an envelope curve, and adding and averaging them.

8. The method according to any one of claims 1 to 5, characterized in that The method also includes verifying the fault occurrence side through the x value: when x<0, the transmission line on the first side of the suspected measuring point is a faulty line; when x=0, there is a fault at the suspected measuring point; when x>0, the transmission line on the second side of the suspected measuring point is a faulty line.

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