Method for Locating Ground Fault of Underground Cable

Abstract

The present invention specifically relates to a method for locating underground cable grounding faults, belonging to the technical field of data processing methods for locating underground cable grounding faults by using matrices. Considering the differences in the traveling wave propagation speed in different fault scenarios, the present invention combines the speed and time of the traveling wave, and selects the distances at which the traveling waves generated at the fault point reach the endpoints of the main line and each branch line to form a fault difference matrix, which is subtracted from the fixed difference matrix formed by the network topology of the underground cable to form a position judgment difference matrix. The position judgment difference matrix is used to determine whether the fault point specifically occurs on the main line or a specific branch line of the underground cable. Finally, the specific position of the fault point is calculated based on the speed and time at which the traveling waves collected by the traveling wave collector arrive. Without relying on the electrical parameters of the cable, the calculation difficulty is greatly reduced, and rapid and accurate location of underground cable grounding faults is achieved.

Description

Technical Field

[0001] The present invention specifically relates to a method for locating the grounding fault of underground cables, belonging to the technical field of data processing methods for locating the grounding fault of underground cables using matrices (G06F17 / 16). Background Art

[0002] Underground cables have an insulating outer layer, which can effectively prevent cable aging, insulation layer shedding, and corrosion by acid-base gases and water vapor in the atmosphere, thereby improving the safety of power transmission. The laying method of underground cables avoids faults caused by external factors such as wind, rain, and animal gnawing in overhead lines, improving the reliability of the power grid. However, the insulation layer of the cable may be corroded under harsh environmental conditions such as high temperature and humidity, the insulation layer may be exposed due to improper operation during construction, or the cable may be damaged by various external factors such as lightning strikes and animal gnawing, all of which can cause grounding faults in underground cables. After a grounding fault occurs in an underground cable, it will not only affect the normal operation of the power system but also pose a threat to personal safety. Therefore, after the cable is laid, detection measures need to be taken to facilitate the discovery and handling of the fault at the initial stage or before serious consequences occur to ensure the safety and stability of the power system. The Chinese patent application number is CN202310455087.0, and the patent name is: A Method and Device for Locating Traveling Waves of Multi-Branch Faults in a Distribution Network Based on Time Difference Matrix Data Fitting. This method compares and analyzes the constructed reference time difference matrix under the simulated fault state with the fault time difference matrix after the actual fault occurs to identify the main fault line. However, this strategy does not fully consider the differences in the traveling wave propagation speed under different fault scenarios. At the same time, the matrix fitting of each value leads to a sharp increase in the calculation amount, a large storage requirement, and an extended fault determination period. In addition, complex distance point calculation methods need to be used in the fault location process, resulting in an overly cumbersome entire location method and a poor location accuracy rate. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: how to quickly and accurately locate the occurrence position of the grounding fault of underground cables.

[0004] To solve the above technical problem, the technical solution proposed by the present invention is: A method for locating the grounding fault of underground cables, comprising the following steps:

[0005] Step 1: Draw the network topology of the underground cable structure, using A s and A m to represent the starting end and the ending end of the main line of the underground cable; the endpoints of the n branch lines from the starting end to the ending end of the main line of the underground cable are successively represented by A 1 、A 2 、…、to A nis represented; the n branch lines from the starting end to the ending end of the main line of the underground cable and the branch nodes of the main line of the underground cable are successively represented by B 1 , B 2 , …, to B n ; an underground cable coordinate system is established in the depth plane where the underground cable is located. The underground cable coordinate system takes the starting end of the main line of the underground cable as the origin, the direction from the starting end to the ending end of the main line of the underground cable as the X-axis, and the straight line perpendicular to the X-axis and located in the depth plane where the underground cable is located as the Y-axis;

[0006] Step 2: In the underground cable coordinate system, calculate the distances between the A 1 , A 2 , …, and A n to the B 1 , B 2 , …, and B n successively through the following formula (1),

[0007] (1)

[0008] In formula (1), is the distance between the end point of the i-th branch branch among the n branch lines and the B 1 , B 2 , …, and B n ; is the X-axis coordinate of the end point of the i-th branch branch among the n branch lines; is the X-axis coordinate of the i-th branch node among the n branch nodes; is the Y-axis coordinate of the end point of the i-th branch branch among the n branch lines; is the Y-axis coordinate of the i-th branch node among the n branch nodes;

[0009] Calculate the distance between the A s and the B 1 , B 2 , …, and B n through the following formula (2),

[0010] (2)

[0011] In formula (2), is the X-axis coordinate of the A s ; is the Y-axis coordinate of the A s ;

[0012] Calculate the distances between the end points of the n branch lines and the n branch nodes and the As The difference in the distances between the end points of the n branch lines and the n branch nodes,

[0013] (3);

[0014] In formula (3), is the difference between the distance from the end point of the i-th branch branch of the n branch lines to the i-th branch node among the n branch nodes and the distance from the A s to the i-th branch node among the n branch nodes;

[0015] Calculate the differences between the distances from the end points of the n branch lines to the n branch nodes and the distances from the A 1 、A 2 、…、and A n-1 to the n branch nodes through the following formula (4),

[0016] (4);

[0017] In formula (3), is the difference between the distance from the end point of the i-th branch branch of the n branch lines to the i-th branch node among the n branch nodes and the distance from the end point of the j-th branch branch of the n - 1 branch lines to the i-th branch node among the n branch nodes;

[0018] Collect the differences between the distances from the end points of the n branch lines to the n branch nodes and the distances from the A s 、A 1 、A 2 、…、and A n-1 to the n branch nodes to form a fixed difference matrix Q, as shown in the following formula (4),

[0019] (4);

[0020] Step 3: Install traveling wave collectors at the starting end and the ending end of the main line of the underground cable; also install traveling wave collectors at the end points of the n branch lines of the underground cable; when a grounding fault occurs in the underground cable, define the time and speed at which the traveling wave generated by the fault point F reaches the starting end of the main line of the underground cable as and ; define the time and speed at which the traveling wave generated by the fault point F reaches the ending end of the main line of the underground cable as and ; define the time and speed at which the traveling wave generated by the fault point F reaches the terminal of the i-th branch line among the n branch lines of the underground cable as and ;

[0021] Step 4: Calculate the difference between the distance from the end points of the \(n\) branch lines to the fault point \(F\) and the distance from \(A\) s to the fault point \(F\) through the following formula (5),

[0022] (5)

[0023] In formula (5), is the difference between the distance from the end point of the \(i\)-th branch branch of the \(n\) branch lines to the fault point \(F\) and the distance from \(A\) s to the fault point \(F\); is the distance from the end point of the \(i\)-th branch branch of the \(n\) branch lines to the fault point \(F\); is \(A\) s to the distance to the fault point \(F\);

[0024] Calculate the difference between the distance from the end points of the \(n\) branch lines to the fault point \(F\) and the distances from \(A\) 1 , \(A\) 2 , …, and \(A\) n-1 to the fault point \(F\) through the following formula (6),

[0025] (6)

[0026] In formula (6), is the difference between the distance from the end point of the \(i\)-th branch branch of the \(n\) branch lines to the fault point \(F\) and the distance from the end point of the \(j\)-th branch branch of the \(n - 1\) branch lines to the fault point \(F\); is the distance from the end point of the \(j\)-th branch branch of the \(n - 1\) branch lines to the fault point \(F\);

[0027] Collect the differences between the distances from the end points of the \(n\) branch lines to the fault point \(F\) and \(A\) s , \(A\) 1 , \(A\) 2 , …, and \(A\) n-1 to the fault point \(F\) to form a fault difference matrix \(N\) as shown in the following formula (7),

[0028] (7);

[0029] Step 5: Subtract the fixed difference matrix \(Q\) from the fault difference matrix \(N\) to obtain a position judgment difference matrix as shown in the following formula (8),

[0030] (8);

[0031] If, except for the elements in the first column, there is a column in the position judgment difference matrix where all elements are 0, it is considered that the fault point F is on the main line of the underground cable;

[0032] Calculate the distance from the fault point F to the starting end of the main line of the underground cable according to the following formula (9) ,

[0033] (9);

[0034] If, except for the elements in the first column, there is a column in the position judgment difference matrix where all elements are less than 0, and all elements in the remaining columns are greater than or equal to 0, it is considered that the fault point F is on the branch line corresponding to the column where all elements are less than 0;

[0035] Calculate the distance from the fault point F to the end point of the branch branch where the fault point F is located according to the following formula (10) ,

[0036] (10)

[0037] In formula (10), is the speed at which the traveling wave collector at the end point of the branch branch where the fault point F is located receives the traveling wave generated when the fault occurs at the fault point F; The time when the traveling wave generated when the fault occurs at the fault point F reaches the end point of the branch branch where the fault point F is located.

[0038] Advantages of the present invention: Considering the difference in the traveling wave propagation speed in different fault scenarios, the present invention combines the speed and time of the traveling wave, selects the distance from the traveling wave generated at the fault point to the end points of the main line and each branch line, forms a position judgment difference matrix by subtracting the fixed difference matrix formed by the network topology of the underground cable from the fault difference matrix, and judges whether the fault point specifically occurs on the main line or a specific branch line of the underground cable through the position judgment difference matrix. Finally, the specific position of the fault point is calculated through the speed and time at which the traveling wave collected by the traveling wave collector arrives. Without relying on the electrical parameters of the cable, the calculation difficulty is greatly reduced, and the rapid and accurate positioning of the underground cable grounding fault is realized. Description of the Drawings

[0039] Figure 1 is a flowchart of a method for locating a grounding fault of an underground cable according to the present invention. Detailed Embodiment

[0040] The following further describes a method for locating underground cable grounding faults of the present invention in conjunction with specific embodiments and drawings.

[0041] Embodiment

[0042] The method for locating underground cable grounding faults in this embodiment is as Figure 1 shown and includes the following steps:

[0043] Step 1: Draw the network topology of the underground cable structure, and use A s and A m to represent the starting end and the ending end of the main line of the underground cable; sequentially represent the endpoints of the n branch lines from the starting end to the ending end of the main line of the underground cable with A 1 、A 2 、…、to A n ; sequentially represent the branch nodes of the n branch lines from the starting end to the ending end of the main line of the underground cable and the main line of the underground cable with B 1 、B 2 、…、to B n ; establish an underground cable coordinate system in the depth plane where the underground cable is located. The underground cable coordinate system takes the starting end of the main line of the underground cable as the origin, the direction from the starting end to the ending end of the main line of the underground cable as the X-axis, and the straight line perpendicular to the X-axis and located in the depth plane where the underground cable is located as the Y-axis.

[0044] Step 2: In the underground cable coordinate system, sequentially calculate the distances between A 1 、A 2 、…、and A n to B 1 、B 2 、…、and B n through the following formula (1),

[0045] (1)

[0046] In formula (1), is the distance between the endpoint of the i-th branch branch among the n branch lines and B 1 、B 2 、…、and B n ; is the X-axis coordinate of the endpoint of the i-th branch branch among the n branch lines; is the X-axis coordinate of the i-th branch node among the n branch nodes; is the Y-axis coordinate of the endpoint of the i-th branch branch among the n branch lines; is the Y-axis coordinate of the i-th branch node among the n branch nodes;

[0047] Calculate the distance from A s to B through the following formula (2)1 , B 2 , …, and B n The distance between

[0048] (2)

[0049] In formula (2), is the X-axis coordinate of A s ; is the Y-axis coordinate of A s ;

[0050] The difference between the distance from the endpoints of n branch lines to n branch nodes and the distance from A s to n branch nodes is calculated by the following formula (3),

[0051] (3);

[0052] In formula (3), is the difference between the distance from the endpoint of the i-th branch branch in n branch lines to the i-th branch node in n branch nodes and the distance from A s to the i-th branch node in n branch nodes;

[0053] The difference between the distance from the endpoints of n branch lines to n branch nodes and the distance from A 1 , A 2 , …, and A n-1 to n branch nodes is calculated by the following formula (4),

[0054] (4);

[0055] In formula (3), is the difference between the distance from the endpoint of the i-th branch branch in n branch lines to the i-th branch node in n branch nodes and the distance from the endpoint of the j-th branch branch in n - 1 branch lines to the i-th branch node in n branch nodes;

[0056] Collect the differences between the distances from the endpoints of n branch lines to n branch nodes and the distances from A s , A 1 , A 2 , …, and A n-1 to n branch nodes to form a fixed difference matrix Q, as shown in the following formula (4),

[0057] (4);

[0058] Step 3: Install traveling wave collectors at the starting end and the ending end of the main line of the underground cable; also install traveling wave collectors at the endpoints of the n branch lines of the underground cable; when a grounding fault occurs in the underground cable, define that the time and speed at which the traveling wave generated by the fault point F reaches the starting end of the main line of the underground cable are and ; define that the time and speed at which the traveling wave generated by the fault point F reaches the ending end of the main line of the underground cable are and ; define that the time and speed at which the traveling wave generated by the fault point F reaches the terminal of the i-th branch line among the n branch lines of the underground cable are and ;

[0059] Step 4: Calculate the difference between the distance from the endpoints of the n branch lines to the fault point F and the distance from A s to the fault point F through the following formula (5),

[0060] (5)

[0061] In formula (5), is the difference between the distance from the endpoint of the i-th branch branch among the n branch lines to the fault point F and the distance from A s to the fault point F; is the distance from the endpoint of the i-th branch branch among the n branch lines to the fault point F; is A s the distance to the fault point F;

[0062] Calculate the difference between the distance from the endpoints of the n branch lines to the fault point F and the distances from A 1 、A 2 、…、and A n-1 to the fault point F through the following formula (6),

[0063] (6)

[0064] In formula (6), is the difference between the distance from the endpoint of the i-th branch branch among the n branch lines to the fault point F and the distance from the endpoint of the j-th branch branch among the n - 1 branch lines to the fault point F; is the distance from the endpoint of the j-th branch branch among the n - 1 branch lines to the fault point F;

[0065] Compare the distance from the endpoints of the n branch lines to the fault point F with A s 、A 1 、A 2 、…、and A n-1The differences in the distances to the fault point F are collected to form a fault difference matrix N, as shown in the following equation (7):

[0066] (7);

[0067] Step 5: Subtract the fixed difference matrix Q from the fault difference matrix N to obtain a position judgment difference matrix , as shown in the following equation (8):

[0068] (8);

[0069] If, except for the elements in the first column, there is a column in the position judgment difference matrix where all elements are 0, it is considered that the fault point F is on the main line of the underground cable;

[0070] Calculate the distance from the fault point F to the starting end of the main line of the underground cable according to the following equation (9) ,

[0071] (9);

[0072] If, except for the elements in the first column, there is a column in the position judgment difference matrix where all elements are less than 0, and all elements in the remaining columns are greater than or equal to 0, it is considered that the fault point F is on the branch line corresponding to this column where all elements are less than 0;

[0073] Calculate the distance from the fault point F to the end point of the branch where the fault point F is located according to the following equation (10) ,

[0074] (10)

[0075] In equation (10), is the speed at which the traveling wave collector at the end point of the branch where the fault point F is located receives the traveling wave generated when the fault occurs at the fault point F; is the time when the traveling wave generated when the fault occurs at the fault point F reaches the end point of the branch where the fault point F is located.

Claims

1. A method for locating an underground cable grounding fault, characterized in that: The following steps are involved: Step 1: Draw the network topology of the underground cable structure using A s and A m to indicate the starting and ending points of the main line of the underground cable; the endpoints of the n branch lines from the starting end to the end of the main line of the underground cable are represented by A1, A2, ..., to A n The n branch lines from the starting end to the end of the main line of the underground cable and the branch nodes of the main line of the underground cable are represented by B1, B2, ..., to B n To represent; establish an underground cable coordinate system on the depth plane where the underground cable is located, wherein the underground cable coordinate system takes the starting end of the main line of the underground cable as the origin, the direction from the starting end to the end of the main line of the underground cable as the X-axis, and the straight line perpendicular to the X-axis and located in the depth plane where the underground cable is located as the Y-axis; Step 2: Calculate A1, A2, ..., and A in the underground cable coordinate system in sequence by the following formula (1): n to B1, B2, ..., and B n The distance between In formula (1), is the connection between the endpoint of the i-th branch line in the n branch lines and the B1, B2, ..., and B n The distance between is the X-axis coordinate of the endpoint of the i-th branch line among the n branch lines; is the X-axis coordinate of the i-th branch node among the n branch nodes; is the Y-axis coordinate of the endpoint of the i-th branch line among the n branch lines; is the Y-axis coordinate of the i-th branch node among the n branch nodes; The A is calculated by the following formula (2): s to B1, B2, ..., and B n The distance between In formula (2), It is the A s The X-axis coordinate of It is the A s The Y-axis coordinate of The distances between the endpoints of the n branch lines and the n branch nodes and the A are calculated by the following formula (3): s The difference in distances to the n branch nodes, In formula (3), is the distance between the endpoint of the i-th branch line in the n branch lines and the i-th branch node in the n branch nodes and the A s The difference in distance to the i-th branch node among the n branch nodes; The distances between the endpoints of the n branch lines and the n branch nodes and the distances between A1, A2, ..., and A n-1 The difference in distances to the n branch nodes, In formula (4), is the difference between the distance between the endpoint of the i-th branch line among the n branch lines and the i-th branch node among the n branch nodes and the distance between the endpoint of the j-th branch line among the n-1 branch lines and the i-th branch node among the n branch nodes; The distances between the endpoints of the n branch lines and the n branch nodes are compared with A s , A1, A2, …, and A n-1 The differences in the distances to the n branch nodes are collected to form a fixed difference matrix Q, as shown in the following formula (4-1): Step 3: Install traveling wave collectors at the starting and ending points of the main line of the underground cable; also install traveling wave collectors at the ending points of the n branch lines of the underground cable; when a ground fault occurs in the underground cable, define the time and speed of the traveling wave generated by the fault point F to reach the starting end of the main line of the underground cable as t s and v s ; Define the time and speed of the traveling wave generated by the fault point F to reach the end of the main line of the underground cable as t m and v m ; Define the time and speed of the traveling wave generated by the fault point F to reach the terminal of the i-th branch line among the n branch lines of the underground cable as t i and v i ; Step 4: Calculate the distance between the endpoints of the n branch lines and the fault point F and the distance between the A and the fault point F by the following formula (5): s The difference in distance to the fault point F, In formula (5), is the distance between the endpoint of the i-th branch line in the n branch lines and the fault point F and the distance between the i-th branch line and the fault point F and the A s The difference in distance to the fault point F; is the distance between the endpoint of the i-th branch line among the n branch lines and the fault point F; It is the A s The distance to the fault point F; The distances between the endpoints of the n branch lines and the fault point F and the distances between A1, A2, ..., and A n-1 The difference in distance to the fault point F, In formula (6), is the difference between the distance between the endpoint of the i-th branch line among the n branch lines and the fault point F and the distance between the endpoint of the j-th branch line among the n-1 branch lines and the fault point F; is the distance between the endpoint of the jth branch line among the n-1 branch lines and the fault point F; The distances between the endpoints of the n branch lines and the fault point F are compared with A s , A1, A2, …, and A n-1 The difference between the distance to the fault point F is collected to form a fault difference matrix N, as shown in the following formula (7): Step 5: Subtract the fixed difference matrix Q from the fault difference matrix N to obtain the position judgment difference matrix δ, as shown in the following formula (8): If, except for the first column of elements in the position judgment difference matrix δ, there is a column whose elements are all 0, it is considered that the fault point F is located on the main line of the underground cable; The distance l from the fault point F to the starting end of the main line of the underground cable is calculated according to the following formula (9): z , l z =v s ×t s (9); If, in the position judgment difference matrix δ, except for the first column of elements, there is a column whose elements are all less than 0, and the elements of all the remaining columns are all greater than or equal to 0, it is considered that the fault point F is located on the branch line corresponding to the column whose elements are all less than 0; The distance l from the fault point F to the end point of the branch where the fault point F is located is calculated according to the following formula (10): f , l f =v f ×t f (10) In formula (10), v f It is the speed of the traveling wave generated when the fault point F fails and is received by the traveling wave collector at the end point of the branch line where the fault point F is located; t f The time it takes for the traveling wave generated when a fault occurs at the fault point F to reach the end point of the branch where the fault point F is located.

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