A power cable extruded semi-conductive shielding sharp corner detection and evaluation system and method

Abstract

The present invention relates to a power cable extruded semi-conductive shielding sharp corner detection and evaluation system and method thereof. The present invention constructs an evaluation system including an image acquisition and display module, an arc coordinate positioning module, a sharp corner top coordinate positioning module and an evaluation calculation module. At the same time, the arc coordinate positioning module calculates the center and radius of the arc point set fitting, and the sharp corner top coordinate positioning module calculates the center and radius of the sharp corner top point set fitting. The evaluation calculation module quantitatively evaluates the semi-conductive shielding sharp corners to construct an evaluation method of the evaluation system. The present invention realizes the quantitative detection of the sharp corners of the extruded semi-conductive shielding of power cables. At the same time, the digital level of power cable network access detection is improved, the problem of sharp corners in semi-conductive shielding is eliminated, and the network access and laying of cables are improved, thereby improving the safety and reliability of the power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical equipment operation detection, and in particular to a power cable extruded semi-conductive shielding sharp corner detection and evaluation system and method. Background Art

[0002] The extruded semi-conductive shield of power cable is a semi-conductive shielding layer located on both sides of the insulation of extruded insulated power cable. Its function is to improve the electric field distribution in the cable insulation and prevent insulation breakdown caused by electric field distortion. According to GB / T 12706 rated voltage 1kV (Um=1.2kV) to 35kV (Um=40.5kV) extruded insulated power cable and accessories, GB / T 11017 rated voltage 110kV (Um=126kV) cross-linked polyethylene insulated power cable and accessories, GB / T 18890 rated voltage 220kV (Um=252kV) cross-linked polyethylene insulated power cable and accessories, the national standard clearly requires that the surface of the semi-conductive shielding layer of medium and high voltage power cables should be smooth and should not have sharp corners. Due to the three-layer co-extrusion process commonly used in cross-linked polyethylene power cables, the presence of sharp corners will inevitably cause the surface of the semi-conductive shield to be uneven and the insulation thickness to be uneven in all directions around the conductor. After the voltage is applied to the cable, the sharp corners on the semi-conductive shield will directly affect the electric field distribution in the insulation, and in severe cases, partial discharge will even occur, forming cable defects. Up to now, the detection of semi-conductive shielding sharp corners is limited to manual qualitative identification. For very serious sharp corner problems, they can be found by testing the excessive partial discharge amount during the partial discharge test phase of the whole cable, but there is still a lack of effective detection methods for general sharp corner problems. The adverse effects of these sharp corners will gradually be exposed over a long period of time, posing a hidden danger to cable operation and endangering the safety of the power grid system. Generally, the defects of cable accessories are concentrated in the accessories themselves, and the defects of accessories can be avoided after replacement, but the defects of the sharp corners of the cable semi-conductive shield involve a long range of cables, or even the entire length of the cable, which is difficult to locate and the cost of replacement is very high. Therefore, in order to prevent the impact of semi-conductive shielding sharp corners on medium and high voltage power cables, it is necessary to develop effective detection devices and methods to prevent defective cables from entering the power grid system. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a system and method for detecting and evaluating the sharp corners of the extruded semi-conductive shielding of a power cable, which realizes the quantitative detection of the sharp corners of the extruded semi-conductive shielding of the power cable, while improving the digital level of power cable network access detection, eliminating the problem of sharp corners of the semi-conductive shielding cable during network laying, and improving the safety and reliability of the power grid.

[0004] The present invention solves the technical problem by adopting the following technical solutions:

[0005] A power cable extruded semi-conductive shielding sharp corner detection and evaluation system comprises an image acquisition and display module, an arc coordinate positioning module, a sharp corner top coordinate positioning module and an evaluation calculation module, wherein the image acquisition and display module, the arc coordinate positioning module, the sharp corner top coordinate positioning module and the evaluation calculation module are connected in sequence, the image acquisition and display module acquires cable radial slice image information and establishes a coordinate system, the arc coordinate positioning module calculates the center point and radius or diameter of the arc point fitting, the sharp corner top coordinate positioning module calculates the center point and radius or diameter of the sharp corner top point fitting, and the evaluation calculation module calculates the obtained data.

[0006] An evaluation method for a power cable extruded semi-conductive shielding sharp corner detection and evaluation system comprises the following steps:

[0007] Step 1: The image acquisition and display module acquires radial slice image information of the cable and constructs a plane coordinate system based on the acquired image;

[0008] Step 2: In the plane coordinate system, the arc coordinate positioning module fits and calculates the circle in the plane coordinates according to the arc point data set, and obtains the center and radius or diameter of the arc point set fitting;

[0009] Step 3: In the plane coordinate system, the sharp corner top coordinate positioning module fits and calculates the circle in the plane coordinates according to the sharp corner top point data set, and obtains the center and radius or diameter of the fitted circle of the sharp corner top point set;

[0010] Step 4: The evaluation calculation module quantitatively evaluates the semi-conductive shielding sharp corners through the center and radius of the arc point set and the center and radius of the sharp corner top point set.

[0011] Moreover, the specific implementation method of constructing the plane coordinate system in step 1 includes: using a plane coordinate system in which a digital projector or a reading microscope with a magnification that meets the cable insulation size detection standard is connected to a computer, using a plane coordinate system provided by a digital projector or a reading microscope, or re-establishing a new coordinate system.

[0012] Furthermore, the step 2 comprises the following steps:

[0013] Step 2.1, establish an arc point coordinate set, and set the arc point coordinate set to an empty set;

[0014] Step 2.2, providing a prompt message to the user, requiring the user to specify a point on the inner or outer arc of the semi-conductive shield on the collected and enlarged radial cross-section of the cable;

[0015] Step 2.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the arc point coordinate set. If so, return to step 2.2, otherwise proceed to step 2.4;

[0016] Step 2.4, add the point coordinates provided by the user to the arc point coordinate set;

[0017] Step 2.5, determine the number of points in the arc point coordinate set. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point on the inner or outer arc of the semi-conductive shield on the collected and enlarged cable radial profile, and return to step 2.2; otherwise, proceed to step 2.6;

[0018] Step 2.6, determine whether all the point coordinates in the arc point coordinate set are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the arc point coordinate set and return to step 2.2; otherwise, proceed to step 2.7;

[0019] Step 2.7, provide prompt information to the user, the number of points in the arc point coordinate set reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 2.2, otherwise go to step 2.8;

[0020] Step 2.8, determine the number of points in the arc point coordinate set, if the number is equal to 3, proceed to step 2.9; otherwise, proceed to step 2.10;

[0021] Step 2.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the arc fitting center O and the length R of the radius or diameter p ;

[0022] Step 2.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the arc fitting center O and the radius or diameter length R p .

[0023] Furthermore, the step 3 comprises the following steps:

[0024] Step 3.1, establish a sharp corner top point coordinate set, and set the sharp corner top point coordinate set to an empty set;

[0025] Step 3.2, providing a prompt message to the user, requiring the user to specify a point on the top of the inner or outer corner of the semi-conductive shield on the collected and enlarged radial cross-section of the cable, and proceed to step 3.3;

[0026] Step 3.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the coordinate set of the tip top point. If so, return to step 3.2, otherwise proceed to step 3.4;

[0027] Step 3.4, add the point coordinates provided by the user to the coordinate set of the top point of the sharp corner;

[0028] Step 3.5, determine the number of points in the coordinate set of the sharp corner top point, if the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point of the inner or outer sharp corner top of the semi-conductive shield on the collected and enlarged cable radial cross-section, and return to step 3.2; otherwise, proceed to step 3.6;

[0029] Step 3.6: Determine whether all the point coordinates in the coordinate set of the tip top point are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the coordinate point set and return to step 3.2; otherwise, proceed to step 3.7;

[0030] Step 3.7, provide prompt information to the user, the number of points in the coordinate set of the tip top point reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 3.2, otherwise proceed to step 3.8;

[0031] Step 3.8: Determine the number of points in the coordinate set of the tip top point. If the number is equal to 3, proceed to step 3.9; otherwise, proceed to step 9.

[0032] Step 3.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius or diameter length R s ;

[0033] Step 3.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius or diameter length R s .

[0034] Furthermore, the step 4 comprises the following steps:

[0035] Step 4.1, read the fitting circle center coordinates and radius or diameter length results of the arc coordinate positioning module in step 2 and the sharp corner top coordinate positioning module in step 3;

[0036] Step 4.2: Calculate the distance d from the arc fitting center O to the corner top fitting center O' OO’ ;

[0037] Step 4.3: The distance d from the arc fitting center O to the sharp corner top fitting center O' OO’Calculate the semi-conductive shielding sharp angle deviation rate m;

[0038] Step 4.4: According to R p With R s Read the result and calculate the sharp angle amplitude l.

[0039] Moreover, the specific calculation method of step 4.3 is:

[0040]

[0041] Among them, R p Fit the center O coordinate and radius or diameter length of the arc.

[0042] Moreover, the specific calculation method of step 4.4 is:

[0043]

[0044] Among them, R p R is the coordinate of the center O of the arc fitting and the length of the radius or diameter. s Fit the center O' coordinates and radius or diameter length of the circle to the tip of the sharp corner.

[0045] Moreover, the method for determining whether the coordinates of the point coincide with all the points in the set of coordinates of the top point of the sharp corner is: a vector is formed by subtracting the coordinates of the two points, and if the norm of the vector is less than a certain threshold, the two points are considered to coincide, otherwise they do not coincide;

[0046] The method for determining whether all the coordinates of the points in the coordinate set are approximately on the same straight line is: fitting the plane straight line equation with the coordinates of all the points, calculating the distances from all the points to the straight line, and the result forms a vector. If the norm of the vector is less than a certain threshold, it is considered that the points are collinear, otherwise they are not collinear.

[0047] The method for performing circular fitting calculation based on the coordinates of three non-collinear points is:

[0048] Let the coordinates of the center of the fitted circle be (x0, y0), the radius be r, and the coordinates of the three non-collinear points be (x1, y1), (x2, y2), and (x3, y3). Since the distances from the center to the three points are equal, the simultaneous equations give the coordinates of the center:

[0049]

[0050] Calculate the radius of the fitted circle based on the distance between the center (x0, y0) and (x1, y1)

[0051] The method for calculating the circular fitting based on the coordinates of more than three points is as follows: let the coordinates of the center of the fitting circle be (x0, y0), the radius be r, and the coordinates of the three or more non-collinear points be (x i ,y i ), where i = 1, ..., n, the least squares method is used to determine the coordinates of the center and radius of the fitting circle, and the intermediate variables a, b, c, d, e, g, h are recorded to obtain:

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] Finally, we get:

[0061]

[0062]

[0063] The advantages and positive effects of the present invention are:

[0064] The present invention constructs an evaluation system including an image acquisition and display module, an arc coordinate positioning module, a sharp corner top coordinate positioning module and an evaluation calculation module. At the same time, the center and radius of the arc point set fitting are calculated according to the arc coordinate positioning module, and the center and radius of the sharp corner top point set fitting are calculated according to the sharp corner top coordinate positioning module. The evaluation calculation module quantitatively evaluates the semi-conductive shielding sharp corners to construct an evaluation method of the evaluation system. Quantitative detection of the semi-conductive shielding sharp corners of power cables is achieved. At the same time, the digital level of power cable network access detection is improved, the problem of sharp corners of semi-conductive shielding is eliminated, and the network access and laying of cables are improved to improve the safety and reliability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a structural block diagram of the system of the present invention. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below with reference to the accompanying drawings.

[0067] A power cable extruded semi-conductive shielding sharp corner detection and evaluation system, such as Figure 1 As shown, it includes an image acquisition and display module, an arc coordinate positioning module, a sharp corner top coordinate positioning module and an evaluation calculation module, and the image acquisition and display module, the arc coordinate positioning module, the sharp corner top coordinate positioning module and the evaluation calculation module are connected in sequence.

[0068] The image acquisition and display module realizes the functions of acquiring radial slice image information of the cable and displaying it to the user, and constructs a plane coordinate system based on the acquired image.

[0069] The user specifies the positions of several points on the inner (or outer) arc of the semi-conductive shield, and the arc coordinate positioning module gives the coordinates of each point in the arc point set specified by the user. According to the arc point data set, the circle in the plane coordinate is fitted and calculated to obtain the center and radius or diameter (or diameter) of the arc point set.

[0070] This module allows the user to specify the positions of several points on the inner (or outer) corner of the semi-conductive shield. The corner top coordinate positioning module gives the coordinates of each point in the corner top point set specified by the user. Based on the corner top point data set, the circle in the plane coordinates is fitted and calculated to obtain the center of the circle and the radius or diameter (or diameter) of the corner top point set.

[0071] The evaluation calculation module realizes the quantitative evaluation of the semi-conductive shielding sharp corners by using the fitting center and radius (or diameter) of the arc point data set and the sharp corner top point data set.

[0072] An evaluation method for a power cable extruded semi-conductive shielding sharp corner detection and evaluation system comprises the following steps:

[0073] Step 1: The image acquisition and display module acquires the radial slice image information of the cable and constructs a plane coordinate system based on the acquired image.

[0074] The implementation method of this step is: the image acquisition and display module adopts a plane coordinate system that connects a digital projector or a reading microscope with a magnification that meets the cable insulation size detection standard requirements and a computer, adopts the plane coordinate system provided by the digital projector or the reading microscope, or re-establishes a new coordinate system.

[0075] Step 2: In the plane coordinate system, the arc coordinate positioning module fits and calculates the circle in the plane coordinates based on the arc point data set to obtain the center and radius or diameter of the arc point set.

[0076] Step 2.1, establish an arc point coordinate set, and set the arc point coordinate set to an empty set;

[0077] Step 2.2, providing a prompt message to the user, requiring the user to specify a point on the inner or outer arc of the semi-conductive shield on the collected and enlarged radial cross-section of the cable;

[0078] Step 2.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the arc point coordinate set. If so, return to step 2.2, otherwise proceed to step 2.4;

[0079] Step 2.4, add the point coordinates provided by the user to the arc point coordinate set;

[0080] Step 2.5, determine the number of points in the arc point coordinate set. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point on the inner or outer arc of the semi-conductive shield on the collected and enlarged cable radial profile, and return to step 2.2; otherwise, proceed to step 2.6;

[0081] Step 2.6, determine whether all the point coordinates in the arc point coordinate set are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the arc point coordinate set and return to step 2.2; otherwise, proceed to step 2.7;

[0082] Step 2.7, provide prompt information to the user, the number of points in the arc point coordinate set reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 2.2, otherwise go to step 2.8;

[0083] Step 2.8, determine the number of points in the arc point coordinate set, if the number is equal to 3, proceed to step 2.9; otherwise, proceed to step 2.10;

[0084] Step 2.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the arc fitting center O and the length R of the radius or diameter p ;

[0085] Step 2.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the arc fitting center O and the radius or diameter length R p .

[0086] Step 3: In the plane coordinate system, the sharp corner top coordinate positioning module fits and calculates the circle in the plane coordinates based on the sharp corner top point data set to obtain the center and radius or diameter of the fitted circle of the sharp corner top point set.

[0087] Step 3.1, establish a sharp corner top point coordinate set, and set the sharp corner top point coordinate set to an empty set;

[0088] Step 3.2, providing a prompt message to the user, requiring the user to specify a point on the top of the inner or outer corner of the semi-conductive shield on the collected and enlarged radial cross-section of the cable, and proceed to step 3.3;

[0089] Step 3.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the coordinate set of the tip top point. If so, return to step 3.2, otherwise proceed to step 3.4;

[0090] Step 3.4, add the point coordinates provided by the user to the coordinate set of the top point of the sharp corner;

[0091] Step 3.5, determine the number of points in the coordinate set of the sharp corner top point, if the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point of the inner or outer sharp corner top of the semi-conductive shield on the collected and enlarged cable radial cross-section, and return to step 3.2; otherwise, proceed to step 3.6;

[0092] Step 3.6: Determine whether all the point coordinates in the coordinate set of the tip top point are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the coordinate point set and return to step 3.2; otherwise, proceed to step 3.7;

[0093] Step 3.7, provide prompt information to the user, the number of points in the coordinate set of the tip top point reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 3.2, otherwise proceed to step 3.8;

[0094] Step 3.8: Determine the number of points in the coordinate set of the tip top point. If the number is equal to 3, proceed to step 3.9; otherwise, proceed to step 9.

[0095] Step 3.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius or diameter length R s ;

[0096] Step 3.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius or diameter length R s .

[0097] Step 4: The evaluation calculation module quantitatively evaluates the semi-conductive shielding sharp corners through the center and radius of the arc point set and the center and radius of the sharp corner top point set.

[0098] Step 4.1, read the fitting circle center coordinates and radius or diameter length results of the arc coordinate positioning module in step 2 and the sharp corner top coordinate positioning module in step 3;

[0099] Step 4.2: Calculate the distance d from the arc fitting center O to the corner top fitting center O' OO’ .

[0100] Step 4.3: The distance d from the arc fitting center O to the sharp corner top fitting center O' OO’ Calculate the semi-conductive shielding corner deviation rate m.

[0101]

[0102] Among them, R p Fit the center O coordinate and radius or diameter length of the arc.

[0103] Step 4.4: According to R p With R s Read the result and calculate the sharp angle amplitude l.

[0104]

[0105] Among them, R p R is the coordinate of the center O of the arc fitting and the length of the radius or diameter. s Fit the center O' coordinates and radius or diameter length of the circle to the tip of the sharp corner.

[0106] The arc coordinate positioning module and the corner top coordinate positioning module determine whether the coordinates of the point coincide with all the points in the corner top point coordinate set by: forming a vector with the result of subtracting the coordinates of the two points, and if the norm of the vector is less than a certain threshold, the two points are considered to coincide, otherwise they do not coincide;

[0107] The method to determine whether all the coordinates of the points in the coordinate set are approximately on the same straight line is: fit the plane straight line equation with the coordinates of all the points, calculate the distances from all the points to the straight line, and the result forms a vector. If the norm of the vector is less than a certain threshold, the points are considered to be collinear, otherwise they are not collinear.

[0108] The method for calculating circular fitting based on the coordinates of three non-collinear points is:

[0109] Let the coordinates of the center of the fitted circle be (x0, y0), the radius be r, and the coordinates of the three non-collinear points be (x1, y1), (x2, y2), and (x3, y3). Since the distances from the center to the three points are equal, the simultaneous equations give the coordinates of the center:

[0110]

[0111] Calculate the radius of the fitted circle based on the distance between the center (x0, y0) and (x1, y1)

[0112] The method of calculating the circular fitting based on the coordinates of more than three points is as follows: let the coordinates of the center of the fitting circle be (x0, y0), the radius be r, and the coordinates of the three or more non-collinear points be (x i ,y i ), where i = 1, ..., n, the least squares method is used to determine the coordinates of the center and radius of the fitting circle, and the intermediate variables a, b, c, d, e, g, h are recorded to obtain:

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121] Finally, we get:

[0122]

[0123]

[0124] According to the above-mentioned power cable extruded semi-conductive shielding sharp corner detection and evaluation system and method, two experiments are conducted to clearly and completely describe the present invention.

[0125] Example 1:

[0126] There is a radial insulation slice of an extruded insulated cable and a digital projector that meets the detection requirements. The process of using the present invention to detect the sharp corner of the conductor shield is carried out according to the following steps.

[0127] Step 1: Set the arc point coordinate set to an empty set, select the Euclidean norm to determine whether the coordinates of two points coincide, and set the coordinate coincidence threshold to 1×10 -6 , select the distance between the point and the fitted line in the y-axis direction as the distance measure between the point and the line, select the infinite norm for the judgment of multiple points collinearity, and set the collinearity threshold to 1×10 -2 , proceed to step 2.

[0128] Step 2: Place the insulating slice in the observation area of ​​the digital projector, turn on the digital projector, and the digital projector completes the establishment of the plane coordinate system, and then proceeds to step 3.

[0129] Step 3: Provide a prompt message to the user, asking the user to specify a point on the outer arc of the conductor shield on the collected and enlarged cable radial cross-section diagram. Go to step 4.

[0130] At this time, the user enters a point coordinate (-122.13, 36.8).

[0131] Step 4: Collect the information of the point provided by the user, and determine whether the coordinates of the point overlap with the points in the arc point coordinate set. If there is overlap, return to step 3, otherwise go to step 5.

[0132] Since the current arc point coordinates are an empty set, there is no overlap.

[0133] Step 5: Add the point coordinates provided by the user to the arc point coordinate set and proceed to step 6.

[0134] Step 6: Determine the number of points in the arc point coordinate set. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to supplement the position of the points on the arc on the collected and enlarged cable radial profile diagram, and return to step 3; otherwise, go to step 7.

[0135] Since the number of points in the current arc point coordinate set is 1, return to step 3.

[0136] At this time, the user enters a point coordinate (-122.13, 36.8).

[0137] In step 4, it is determined whether the coordinates of the two points coincide with each other. ||(-122.13, 36.8)-(-122.13, 36.8)||2=0 is less than the threshold value 1×10 -6 , we consider the two points to be coincident, so we return to step 3.

[0138] By analogy, after the user inputs two non-overlapping arc points, the arc point coordinate set contains the following two points:

[0139] Arc point coordinate set x y Point 1 -122.13 36.8 Point 2 -113.74 45.95

[0140] Since the number is less than 3, the user enters another point coordinate (-102.1, 58.62) and proceeds to step 7.

[0141] Step 7: For all points in the arc point coordinate set, determine whether the coordinate points are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the arc point coordinate set and return to step 3; otherwise, go to step 8.

[0142] At this time, the point information in the arc point coordinate set is as follows:

[0143] Arc point coordinate set x y Point 1 -122.13 36.8 Point 2 -113.74 45.95 Point 3 -102.1 58.62

[0144] The equation of the straight line fitted by three points is:

[0145] y=1.089311x+169.8415

[0146] Then the distances from the three points to the straight line are:

[0147] Arc point coordinate set x y Distance from the fitted line Point 1 -122.13 36.8 0.003925 Point 2 -113.74 45.95 0.0067538 Point 3 -102.1 58.62 0.002829

[0148] Then the infinite norm of the spacing vector is ||(0.003925, 0.0067538, 0.002829)|| ∞ =0.0067538 is less than the threshold value 1×10 -2 , the three points are considered to be collinear, so the third point is deleted from the arc point coordinate set and return to step 3.

[0149] After that, when the user completes the third point information and the third point is not collinear with the first two points, proceed to step 8.

[0150] Step 8: Provide prompt information to the user. When the number of points in the arc point coordinate set reaches the requirement to complete the calculation, add more point information to improve the fitting calculation accuracy. Ask the user whether to add more point information. If the user chooses to continue to add, return to step 3, otherwise go to step 9.

[0151] At this time, the user chooses to calculate directly without adding any additional information.

[0152] Step 9: Determine the number of points in the arc point coordinate set. If the number is equal to 3, proceed to step 10; otherwise, proceed to step 11.

[0153] Step 10: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the arc fitting center O and the radius length R p , the module function ends.

[0154] Step 11: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the arc fitting center O and the radius length R p , the module function ends.

[0155] Since the number of arc point coordinate sets is 3 at this time, go to step 10. At this time, the arc point coordinate set is:

[0156]

[0157]

[0158] According to the following formula:

[0159]

[0160] The calculation results show that the coordinates of the center of the fitting circle O are (-110.63, 34.67) and the radius of the fitting circle R p =11.70.

[0161] Step 12: Provide a prompt message to the user, requiring the user to specify a point on the top of the outer corner of the conductor shield on the collected and enlarged cable radial cross-section diagram, and then proceed to step 13.

[0162] Step 13: Collect information of the point provided by the user, and determine whether the coordinates of the point overlap with all the points in the coordinate set of the tip top point. If there is overlap, return to step 12, otherwise go to step 14.

[0163] Step 14: Add the point coordinates provided by the user to the coordinate set of the tip top point and proceed to step 15.

[0164] Step 15: Determine the number of points in the coordinate set of the sharp corner top point. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point at the top of the sharp corner outside the conductor shield on the collected and enlarged cable radial profile, and return to step 12; otherwise, go to step 16.

[0165] Step 16: For all points in the coordinate set of the tip top point, determine whether the coordinate points are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the coordinate point set and return to step 12; otherwise, go to step 17.

[0166] Step 17: Provide prompt information to the user. When the number of points in the coordinate set of the tip top point reaches the requirement to complete the calculation, add more point information to improve the fitting calculation accuracy. Ask the user whether to add more point information. If the user chooses to continue to add, return to step 12, otherwise go to step 18.

[0167] Step 18: Determine the number of points in the coordinate set of the tip top point. If the number is equal to 3, proceed to step 19; otherwise, proceed to step 20.

[0168] Step 19: Perform a circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius length R s , proceed to step 21.

[0169] Step 20: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius length Rs , proceed to step 21.

[0170] Similar to the process of constructing the arc point coordinate set, the user enters the information of three non-overlapping and non-collinear points and chooses not to add any more information. The coordinate set of the top point of the sharp corner is:

[0171] The coordinate set of the tip top point x y Point 1 -120.5 31.54 Point 2 -118.52 42.02 Point 3 -107.65 45.81

[0172] According to the following formula:

[0173]

[0174] The calculation results show that the coordinates of the fitting circle center O' are (-109.97, 34.98) and the fitting circle radius R s =11.08.

[0175] Step 21: Read the fitting center coordinates and radius (or diameter) length results of the arc coordinate positioning module and the sharp corner top coordinate positioning module, and proceed to step 22.

[0176] Step 22: Calculate the distance d from the arc fitting center O to the corner top fitting center O' OO’ , go to step 23;

[0177] Step 23: Calculate the conductor shielding sharp angle deviation rate m according to the following formula and proceed to step 23:

[0178]

[0179] Step 24: Calculate the sharp angle amplitude l according to the following formula, and the function of this module ends.

[0180]

[0181] Carry out various calculations in sequence to obtain the distance d between the centers of the two circles OO’ =0.72, sharp corner deviation rate m=6.19%, sharp corner amplitude l=5.32%, completing the conductor shielding sharp corner detection and evaluation.

[0182] Example 2:

[0183] There is a radial insulation slice of an extruded insulated cable and a digital projector that meets the detection requirements. The process of detecting the conductor shielding corner using the semi-conductive shielding corner detection and evaluation method proposed in this patent is carried out according to the following steps.

[0184] Step 1: Set the arc point coordinate set to an empty set, select the Euclidean norm to determine whether the coordinates of two points coincide, and set the coordinate coincidence threshold to 1×10 -6, select the distance between the point and the fitted line in the y-axis direction as the distance measure between the point and the line, select the infinite norm for the judgment of multiple points collinearity, and set the collinearity threshold to 1×10 -2 , proceed to step 2.

[0185] Step 2: Place the insulating slice in the observation area of ​​the digital projector, turn on the digital projector, and the digital projector completes the establishment of the plane coordinate system, and then proceeds to step 3.

[0186] Step 3: Provide a prompt message to the user, asking the user to specify a point on the outer arc of the conductor shield on the collected and enlarged cable radial cross-section diagram. Go to step 4.

[0187] Step 4: Collect the information of the point provided by the user, and determine whether the coordinates of the point overlap with the points in the arc point coordinate set. If there is overlap, return to step 3, otherwise go to step 5.

[0188] Step 5: Add the point coordinates provided by the user to the arc point coordinate set and proceed to step 6.

[0189] Step 6: Determine the number of points in the arc point coordinate set. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to supplement the position of the points on the arc on the collected and enlarged cable radial profile diagram, and return to step 3; otherwise, go to step 7.

[0190] Step 7: For all points in the arc point coordinate set, determine whether the coordinate points are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the arc point coordinate set and return to step 3; otherwise, go to step 8.

[0191] Step 8: Provide prompt information to the user. When the number of points in the arc point coordinate set reaches the requirement for completing the calculation, add more point information to improve the fitting calculation accuracy. Ask the user whether to add more point information. If the user chooses to continue to add, return to step 3, otherwise go to step 9.

[0192] The previous steps are similar to those in Example 1 and will not be repeated here. In step 8, the user chooses to continue to add point information, and enters a total of 6 non-overlapping and non-collinear points, and chooses to calculate. At this time, the arc point coordinate set is:

[0193] Arc point coordinate set x y Point 1 -122.13 36.8 Point 2 -113.74 45.95 Point 3 -102.52 43.11 Point 4 -98.94 32.41 Point 5 -106.96 23.51 Point 6 -118.55 26.14

[0194] Step 9: Determine the number of points in the arc point coordinate set. If the number is equal to 3, proceed to step 10; otherwise, proceed to step 11.

[0195] Step 10: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the arc fitting center O and the radius length Rp , the module function ends.

[0196] Step 11: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the arc fitting center O and the radius length R p , the module function ends.

[0197] Since the number of arc point coordinate sets is 6 at this time, we proceed to step 11. Remember the intermediate variables a, b, c, d, e, g, h to get:

[0198]

[0199]

[0200]

[0201]

[0202]

[0203] as well as:

[0204]

[0205]

[0206]

[0207] The calculation results show that the coordinates of the center of the fitting circle O are (-110.54, 34.66) and the radius of the fitting circle R p =11.73.

[0208] Step 12: Provide a prompt message to the user, requiring the user to specify a point on the top of the outer corner of the conductor shield on the collected and enlarged cable radial cross-section diagram, and then proceed to step 13.

[0209] Step 13: Collect information of the point provided by the user, and determine whether the coordinates of the point overlap with all the points in the coordinate set of the tip top point. If there is overlap, return to step 12, otherwise go to step 14.

[0210] Step 14: Add the point coordinates provided by the user to the coordinate set of the tip top point and proceed to step 15.

[0211] Step 15: Determine the number of points in the coordinate set of the sharp corner top point. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point at the top of the sharp corner outside the conductor shield on the collected and enlarged cable radial profile, and return to step 12; otherwise, go to step 16.

[0212] Step 16: For all points in the coordinate set of the tip top point, determine whether the coordinate points are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the coordinate point set and return to step 12; otherwise, go to step 17.

[0213] Step 17: Provide prompt information to the user. When the number of points in the coordinate set of the tip top point reaches the requirement to complete the calculation, add more point information to improve the fitting calculation accuracy. Ask the user whether to add more point information. If the user chooses to continue to add, return to step 12, otherwise go to step 18.

[0214] Step 18: Determine the number of points in the coordinate set of the tip top point. If the number is equal to 3, proceed to step 19; otherwise, proceed to step 20.

[0215] Step 19: Perform a circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius length R s , proceed to step 21.

[0216] Step 20: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius length R s , proceed to step 21.

[0217] Similar to the process of constructing the arc point coordinate set, the user enters information about 6 non-overlapping and non-collinear points and chooses not to add any more information. The coordinate set of the top point of the sharp corner is:

[0218] Point coordinates of the tip x y Point 1 -120.5 31.54 Point 2 -118.52 42.02 Point 3 -107.65 45.81 Point 4 -99.49 38.62 Point 5 -101.63 27.03 Point 6 -112.99 23.89

[0219] Remember the intermediate variables a, b, c, d, e, g, h and we get:

[0220]

[0221]

[0222]

[0223]

[0224]

[0225] as well as:

[0226]

[0227]

[0228]

[0229] The calculation results show that the coordinates of the fitting circle center O' are (-109.88, 34.74) and the fitting circle radius R s =11.23.

[0230] Step 21: Read the fitting center coordinates and radius (or diameter) length results of the arc coordinate positioning module and the sharp corner top coordinate positioning module, and proceed to step 22.

[0231] Step 22: Calculate the distance d from the arc fitting center O to the corner top fitting center O' OO’ , go to step 23;

[0232] Step 23: Calculate the conductor shielding sharp angle deviation rate m according to the following formula and proceed to step 24:

[0233]

[0234] Step 24: Calculate the sharp angle amplitude l according to the following formula, and the function of this module ends.

[0235]

[0236] Carry out various calculations in sequence to obtain the distance d between the centers of the two circles OO’ =0.66, sharp corner deviation rate m=5.67%, sharp corner amplitude l=4.32%, completing the conductor shielding sharp corner detection and evaluation.

[0237] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. An evaluation method for a power cable extruded semi-conductive shielding sharp corner detection and evaluation system, characterized in that: The evaluation system used includes an image acquisition and display module, an arc coordinate positioning module, a sharp corner top coordinate positioning module and an evaluation calculation module, which are connected in sequence. The image acquisition and display module acquires radial slice image information of the cable and establishes a coordinate system. The arc coordinate positioning module calculates the center and radius or diameter of the arc point fitting. The sharp corner top coordinate positioning module calculates the center and radius or diameter of the sharp corner top point fitting. The evaluation calculation module calculates the obtained data. The evaluation method comprises the following steps: Step 1: The image acquisition and display module acquires radial slice image information of the cable and constructs a plane coordinate system based on the acquired image; Step 2: In the plane coordinate system, the arc coordinate positioning module fits and calculates the circle in the plane coordinates according to the arc point data set, and obtains the center and radius or diameter of the arc point set fitting; Step 3: In the plane coordinate system, the sharp corner top coordinate positioning module fits and calculates the circle in the plane coordinates according to the sharp corner top point data set, and obtains the center and radius or diameter of the fitted circle of the sharp corner top point set; Step 4, the evaluation calculation module quantitatively evaluates the semi-conductive shielding sharp corner by the center and radius of the arc point set and the center and radius of the sharp corner top point set; Step 4.1, read the fitting circle center coordinates and radius or diameter length results of the arc coordinate positioning module in step 2 and the sharp corner top coordinate positioning module in step 3; Step 4.2: Calculate the distance d from the arc fitting center O to the corner top fitting center O' OO’ ; Step 4.3: The distance d from the arc fitting center O to the sharp corner top fitting center O' OO’ Calculate the semi-conductive shielding sharp angle deviation rate m; Step 4.4: According to R p With R s Read the result and calculate the sharp angle amplitude l.

2. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 1 is characterized by: The specific implementation method of constructing the plane coordinate system in step 1 includes: using a plane coordinate system in which a digital projector or a reading microscope with a magnification that meets the cable insulation size detection standard is connected to a computer, using a plane coordinate system provided by a digital projector or a reading microscope, or re-establishing a new coordinate system.

3. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 1 is characterized by: The step 2 comprises the following steps: Step 2.1, establish an arc point coordinate set, and set the arc point coordinate set to an empty set; Step 2.2, providing a prompt message to the user, requiring the user to specify a point on the inner or outer arc of the semi-conductive shield on the collected and enlarged radial cross-section of the cable; Step 2.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the arc point coordinate set. If so, return to step 2.2, otherwise proceed to step 2.4; Step 2.4, add the point coordinates provided by the user to the arc point coordinate set; Step 2.5, determine the number of points in the arc point coordinate set. If the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point on the inner or outer arc of the semi-conductive shield on the collected and enlarged cable radial profile, and return to step 2.2; otherwise, proceed to step 2.6; Step 2.6, determine whether all the point coordinates in the arc point coordinate set are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the arc point coordinate set and return to step 2.2; otherwise, proceed to step 2.7; Step 2.7, provide prompt information to the user, the number of points in the arc point coordinate set reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 2.2, otherwise go to step 2.8; Step 2.8, determine the number of points in the arc point coordinate set, if the number is equal to 3, proceed to step 2.9; otherwise, proceed to step 2.10; Step 2.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the arc fitting center O and the length R of the radius or diameter p ; Step 2.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the arc fitting center O and the radius or diameter length R p .

4. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 1, characterized in that: The step 3 comprises the following steps: Step 3.1, establish a sharp corner top point coordinate set, and set the sharp corner top point coordinate set to an empty set; Step 3.2, providing a prompt message to the user, requiring the user to specify a point on the top of the inner or outer corner of the semi-conductive shield on the collected and enlarged radial cross-section of the cable, and proceed to step 3.3; Step 3.3, collect information about the point provided by the user, and determine whether the coordinates of the point coincide with all the points in the coordinate set of the tip top point. If so, return to step 3.2, otherwise proceed to step 3.4; Step 3.4, add the point coordinates provided by the user to the coordinate set of the top point of the sharp corner; Step 3.5, determine the number of points in the coordinate set of the sharp corner top point, if the number is less than or equal to 2, provide a prompt message to the user, requiring the user to add the position of the point of the inner or outer sharp corner top of the semi-conductive shield on the collected and enlarged cable radial cross-section, and return to step 3.2; otherwise, proceed to step 3.6; Step 3.6: Determine whether all the point coordinates in the coordinate set of the tip top point are approximately on the same straight line. If they are approximately on a straight line, delete a point coordinate from the coordinate point set and return to step 3.2; otherwise, proceed to step 3.7; Step 3.7, provide prompt information to the user, the number of points in the coordinate set of the tip top point reaches the requirement for completing the calculation, add more point information, improve the fitting calculation accuracy, and ask the user whether to add more point information. If the user chooses to continue to add, return to step 3.2, otherwise proceed to step 3.8; Step 3.8: Determine the number of points in the coordinate set of the tip top point. If the number is equal to 3, proceed to step 3.9; otherwise, proceed to step 9. Step 3.9: Perform circular fitting calculation based on the coordinates of the three non-collinear points to obtain the coordinates of the center of the pointed corner fitting circle O' and the radius or diameter length R s ; Step 3.10: Perform circular fitting calculation based on the coordinates of three or more points to obtain the coordinates of the fitting center O' of the tip and the radius or diameter length R s .

5. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 1, characterized in that: The specific calculation method of step 4.3 is: Among them, R p Fit the center O coordinate and radius or diameter length of the arc.

6. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 1, characterized in that: The specific calculation method of step 4.4 is: Among them, R p R is the coordinate of the center O of the arc fitting and the length of the radius or diameter. s Fit the center O' coordinates and radius or diameter length of the circle to the tip of the sharp corner.

7. The evaluation method of a power cable extruded semi-conductive shielding sharp corner detection and evaluation system according to claim 3 or claim 4, characterized in that: The method for determining whether the coordinates of the point coincide with all the points in the coordinate set of the top point of the sharp corner is: a vector is formed by subtracting the coordinates of the two points, and if the norm of the vector is less than a certain threshold, the two points are considered to coincide, otherwise they do not coincide; The method for determining whether all the coordinates of the points in the coordinate set are approximately on the same straight line is: fitting the plane straight line equation with the coordinates of all the points, calculating the distances from all the points to the straight line, and the result forms a vector. If the norm of the vector is less than a certain threshold, it is considered that the points are collinear, otherwise they are not collinear. The method for performing circular fitting calculation based on the coordinates of three non-collinear points is: The coordinates of the center of the fitted circle are (x0, y0), the radius is r, and the coordinates of the three non-collinear points are: (x1, y1), (x2, y2), (x3, y3). Since the distances from the center to the three points are equal, the simultaneous equations can be used to obtain the coordinates of the center: Calculate the radius of the fitted circle based on the distance between the center (x0, y0) and (x1, y1) The method for calculating the circular fitting based on the coordinates of more than three points is as follows: let the coordinates of the center of the fitting circle be (x0, y0), the radius be r, and the coordinates of the three or more non-collinear points be (x i ,y i ), where i = 1, ..., n, the least squares method is used to determine the coordinates of the center and radius of the fitting circle, and the intermediate variables a, b, c, d, e, g, h are recorded to obtain: Finally, we get:

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