CN113588488A

CN113588488A - Cable defect detection method and device, terminal equipment and storage medium

Info

Publication number: CN113588488A
Application number: CN202111147103.7A
Authority: CN
Inventors: 房晟辰; 杨磊; 李维博; 朱晓辉; 张军; 贺春; 唐庆华; 陈刚; 范巍
Original assignee: State Grid Tianjin Electric Power Co Ltd; Electric Power Research Institute of State Grid Tianjin Electric Power Co Ltd
Current assignee: State Grid Tianjin Electric Power Co Ltd; Electric Power Research Institute of State Grid Tianjin Electric Power Co Ltd
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2021-11-02
Anticipated expiration: 2041-09-29
Also published as: CN113588488B

Abstract

The invention discloses a method and a device for detecting defects of a cable, terminal equipment and a storage medium, wherein the method comprises the following steps: acquiring the total air volume between a corrugated sheath and a buffer layer of a cable to be detected; acquiring the reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath; calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected; and judging whether the air ratio of the cable to be detected is greater than or equal to a defect ratio threshold value, if so, judging that the cable to be detected has defects, and if not, judging that the cable to be detected does not have defects. The embodiment of the invention can accurately detect the defect condition of the cable.

Description

Cable defect detection method and device, terminal equipment and storage medium

Technical Field

The invention relates to the technical field of power cables, in particular to a cable defect detection method, a cable defect detection device, terminal equipment and a storage medium.

Background

In recent years, the number of defects of high-voltage power cables is gradually increased, and the defects become one of important hidden dangers threatening the safety of a power grid, so that how to accurately detect the defects of the cables is of great significance to the safe and reliable operation of a power system.

Disclosure of Invention

The embodiment of the invention provides a method and a device for detecting the defects of a cable, terminal equipment and a storage medium, which can accurately detect the defect condition of the cable.

The embodiment of the invention provides a defect detection method of a cable, which comprises the following steps:

acquiring the total air volume between a corrugated sheath and a buffer layer of a cable to be detected;

acquiring the reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath;

calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected;

judging whether the air ratio of the cable to be detected is greater than or equal to a defect ratio threshold value, if so, judging that the cable to be detected has defects, and if not, judging that the cable to be detected does not have defects; wherein the defect ratio threshold is configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the at least one faulty cable to a baseline volume.

As an improvement of the above solution, said obtaining the total air volume between the corrugated sheath and the buffer layer of the cable to be tested comprises:

acquiring the total length of a cable to be detected and specification parameters within a single wrinkle pitch; wherein the specification parameters comprise an inside radius of the corrugated sheath, an outside radius of the buffer layer, a radius of the insulated wire core not wrapped around the buffer layer, the corrugated pitch, the corrugated depth and the thinnest point thickness of the buffer layer;

obtaining the contact curved surface of the wrinkle sheath and the buffer layer in a cylindrical coordinate systemρ-θ-ZAn approximate function expression of; the polar point of the cylindrical coordinate system is the center of the corrugated sheath, the polar axis is any radial direction of the center of the corrugated sheath, and the Z-axis direction is the axial direction of the cable;

determining the angle of the contact critical point of the corrugated sheath and the buffer layer according to the thinnest point thickness of the buffer layer, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath;

calculating an air volume between the crepe sheath and the breaker ply within a single crepe pitch according to one or more of an air volume calculation formula, the approximate functional expression, the angle of the contact critical point, and the specification parameters; wherein the air volume calculation formula is determined according to the corresponding relation between the air volume between the corrugated sheath and the buffer layer, the internal volume of the corrugated sheath, the volume of the insulated wire core wrapped with the buffer layer and the volume of the stressed deformation part of the buffer layer;

calculating the total air volume between the corrugated sheath and the cushioning layer according to the air volume, the total length and the corrugated pitch.

As an improvement of the scheme, the contact curved surface of the corrugated sheath and the buffer layer is obtained in a cylindrical coordinate systemρ-θ-ZThe following approximate functional expression, comprising:

based on cylindrical coordinate systemρ-θ-ZSelecting n interpolation data points from the contact curved surface of the wrinkle sheath and the buffer layer; wherein the coordinates of the kth interpolated data point is

，k=1，…，n；

Carrying out interpolation calculation according to the n interpolation data points to obtain the contact curved surface in the cylindrical coordinate systemρ-θ-ZThe following approximate function expression.

As an improvement of the above scheme, the air volume calculation formula is:

；

wherein the content of the first and second substances,

；

representing a volume of air between the corrugated sheath and the cushion layer within a single one of the corrugated pitches;d _OArepresents the inside radius of the corrugated sheath;d _O’Crepresents an outside radius of the buffer layer;d _O’Brepresents a radius of the insulated wire core;d _deprepresenting the wrinkle depth;d _lenrepresenting the wrinkle pitch;d _BB’represents the thinnest point thickness of the buffer layer;f(ρ)representing said approximation functionAn expression;θ _Arepresenting the angle of the critical point of contact.

As an improvement of the above scheme, the approximation function expression is:

；

wherein the content of the first and second substances,T ₃ 、T ₂ 、T ₁andT ₀is a polynomial coefficient.

；

wherein the content of the first and second substances,d _OArepresents the inside radius of the corrugated sheath;d _deprepresenting the wrinkle depth;d _lenthe corrugation pitch is indicated.

As an improvement to the above, the specification parameters further include a maximum distance, in a radial plane, from a center of the corrugated sheath to an outer side of the cushioning layer;

when the approximate function expression is

The air volume calculation formula is as follows:

；

wherein the content of the first and second substances,

representing a volume of air between the corrugated sheath and the cushion layer within a single one of the corrugated pitches;d _O’Crepresents an outside radius of the buffer layer;d _OCrepresenting the center of the corrugated sheath toA maximum distance of an outer side of the buffer layer;θ _Arepresenting the angle of the critical point of contact.

As an improvement of the above, the determining an angle of a contact critical point of the corrugated sheath with the buffer layer according to the thinnest point thickness of the buffer layer, the radius of the insulated wire core, the outside radius of the buffer layer and the inside radius of the corrugated sheath includes:

judging whether the thickness of the thinnest point of the buffer layer, the sum of the radius of the insulated wire core and the outer radius of the buffer layer are smaller than or equal to two times of the inner radius of the corrugated sheath or not;

if so, calculating to obtain the angle of the contact critical point of the corrugated sheath and the buffer layer according to the calculation formula of the inner radius of the corrugated sheath, the outer radius of the buffer layer, the radius of the insulated wire core, the thinnest point thickness of the buffer layer and the angle of the contact critical point;

if not, determining that the angle of the contact critical point of the wrinkle sheath and the buffer layer is equal to pi;

wherein, the contact critical point angle calculation formula is as follows:

；

wherein the content of the first and second substances,θ _Arepresents the angle of the critical point of contact;

；d _BB’represents the thinnest point thickness of the buffer layer;d _O’Brepresents a radius of the insulated wire core;d _O’Crepresents an outside radius of the buffer layer;d _OArepresenting the inside radius of the corrugated sheath.

As an improvement of the above, the specification parameters further include an inside maximum radius and an inside minimum radius of the corrugated sheath;

when the reference volume is the total internal volume of the corrugated sheath, the obtaining of the reference volume of the cable to be detected includes:

calculating to obtain a first volume corresponding to the cable to be detected according to the wrinkle pitch, the maximum radius of the inner side of the wrinkle sheath, the minimum radius of the inner side of the wrinkle sheath, the approximate function expression and a calculation formula for calculating the first volume of the insulated wire cores which are not wrapped with the buffer layer in the single wrinkle pitch;

calculating to obtain the total internal volume of the corrugated sheath according to the first volume, the total length and the corrugated pitch corresponding to the cable to be detected, and taking the total internal volume as the reference volume of the cable to be detected;

wherein the first volumeV _AThe calculation formula of (2) is as follows:

；

wherein the content of the first and second substances,V _Arepresenting the first volume;d _lenrepresenting the wrinkle pitch;d _OKrepresents the inside maximum radius of the corrugated sheath;d _ODrepresents an inside minimum radius of the corrugated sheath;f(ρ)representing the approximate function expression.

As an improvement of the above scheme, when the reference volume is the total volume of the insulated wire core wrapped with the buffer layer, the obtaining of the reference volume of the cable to be detected includes:

calculating to obtain a second volume corresponding to the cable to be detected according to the outside radius of the buffer layer, the wrinkle pitch and a calculation formula for calculating the second volume of the insulated wire core wrapped with the buffer layer in the single wrinkle pitch;

calculating to obtain the total volume of the insulated wire core wrapped with the buffer layer according to the second volume corresponding to the cable to be detected, the total length and the wrinkle pitch, and taking the total volume as the reference volume of the cable to be detected;

wherein the calculation formula of the second volume is:

；

wherein the content of the first and second substances,V _Brepresenting the second volume;d _lenrepresenting the wrinkle pitch;d _O’Crepresenting the outside radius of the buffer layer.

As an improvement of the above, the method further comprises:

obtaining a total air volume between a corrugated sheath and a buffer layer of a plurality of the faulty cables;

acquiring reference volumes of a plurality of fault cables;

calculating the ratio of the total air volume of the fault cables to a reference volume to obtain the air ratio of the fault cables;

selecting the minimum value of the air ratios of the fault cables as the defect ratio threshold value.

As an improvement of the above, the method further comprises:

when the cable to be detected is judged to have defects, adding the cable to be detected into a risk list;

and outputting the risk list to a set terminal when the condition for outputting the risk list is determined to be met.

Accordingly, another embodiment of the present invention provides a defect detecting apparatus for a cable, including:

the air volume acquisition module is used for acquiring the total air volume between the corrugated sheath and the buffer layer of the cable to be detected;

the reference volume acquisition module is used for acquiring the reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath;

the air ratio calculation module is used for calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected;

the defect judging module is used for judging whether the air ratio of the cable to be detected is greater than or equal to a defect ratio threshold value, if so, judging that the cable to be detected has defects, and if not, judging that the cable to be detected does not have defects; wherein the defect ratio threshold is configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the at least one faulty cable to a baseline volume.

Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the method for detecting a defect of a cable according to any one of the above methods when executing the computer program.

Another embodiment of the present invention provides a computer-readable storage medium, which includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the method for detecting a defect of a cable according to any one of the above.

Compared with the prior art, the cable defect detection method, the cable defect detection device, the cable defect detection terminal device and the cable defect detection storage medium disclosed by the embodiment of the invention have the advantages that the total air volume between the corrugated sheath and the buffer layer of the cable to be detected and the reference volume of the cable to be detected are obtained, the ratio of the total air volume of the cable to be detected to the reference volume is calculated to obtain the air ratio of the cable to be detected, and then the size relation between the air ratio of the cable to be detected and the defect ratio threshold value configured according to the ratio of the total air volume between the corrugated sheath and the buffer layer of at least one fault cable is used for judging whether the cable to be detected has defects, so that the defect condition of the cable can be accurately detected.

Drawings

Fig. 1 is a flowchart of a method for detecting defects of a cable according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a cable provided by an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a plane of the cable without contact between the corrugated jacket and the buffer layer over the cable provided by an embodiment of the present invention;

FIG. 4 shows the contact surface between the corrugated sheath and the cushioning layer according to the embodiment of the present invention

A plan sectional view;

FIG. 5 is a cross-sectional view of the plane of the cable with contact between the corrugated jacket and the buffer layer over the cable provided by an embodiment of the present invention;

FIG. 6 shows an approximate interface between a corrugated sheath and a cushioning layer according to an embodiment of the present invention

A plan sectional view;

fig. 7 is a block diagram of a defect detection apparatus for a cable according to an embodiment of the present invention;

fig. 8 is a block diagram of a terminal device according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a schematic flow chart of a method for detecting a defect of a cable according to an embodiment of the present invention.

The air volume between the corrugated sheath and the buffer layer on the whole cable depends on the size information such as the total length, the insulation thickness and the like of the actual cable, the size design of the high-voltage cables of various cable suppliers is not consistent, and the air volume mainly reflects the contact condition between the insulation wire core of the cable and the corrugated sheath through the buffer layer, so that the defect detection of the cable is carried out by using the air ratio in order to realize the comparison of the cables with different sizes. The method for detecting the defects of the cable provided by the embodiment comprises the following steps:

s1, acquiring the total air volume between the corrugated sheath and the buffer layer of the cable to be detected;

s2, acquiring the reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath;

s3, calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected;

s4, judging whether the air ratio of the cable to be detected is larger than or equal to a defect ratio threshold value or not, if so, judging that the cable to be detected has defects, and if not, judging that the cable to be detected does not have defects; wherein the defect ratio threshold is configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the at least one faulty cable to a baseline volume.

It should be noted that the formula for calculating the air ratio of the cable to be detected is as follows

. Wherein w is the air ratio of the cable to be tested, V_totalIs the total air volume, V, of the cable to be tested_baseIs the reference volume of the cable to be detected.

In an alternative embodiment, the total air volume may be obtained by measuring the internal volume of the corrugated sheath and the total volume of the insulated wire core wrapped with the buffer layer in the cable to be detected, and subtracting the total volume of the insulated wire core wrapped with the buffer layer from the internal volume of the corrugated sheath of the cable to be detected.

For example, the total volume of the insulated wire core not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer, or the total volume of the inside of the corrugated sheath may be measured by X-ray.

In one embodiment, the cable may have defects including ablation defects in the buffer layer, which are typically accompanied by the following two phenomena: firstly, the water-blocking buffer layer is affected with damp; second, the corrugated sheath, buffer layer and insulation shield material are relatively weak in electrical connection. The former can be prevented by enhancing management and control in the cable production stage as well as in the construction stage, while the latter still has difficulty in finding a substitute for the combination of corrugated sheath-buffer layer-insulating shielding material in a short time. Therefore, on the premise that the material cannot be changed, under the condition that the buffer tape is tightly wrapped on the insulated wire core, the air volume between the corrugated sheath and the buffer layer becomes key information for evaluating the connection between the corrugated sheath and the insulated shielding layer. In said step S4, the defect rate threshold may be a threshold including a buffer layer ablation defect rate, and accordingly, the faulty cable may be a faulty cable including the occurrence of buffer layer ablation, the buffer layer ablation defect ratio threshold may be configured based on a ratio of a total air volume and a reference volume between the corrugated sheath and the buffer layer of the at least one faulty cable in which buffer layer ablation occurred, therefore, the embodiment of the invention obtains the total air volume between the corrugated sheath and the buffer layer of the cable to be detected and the reference volume of the cable to be detected, calculates the ratio of the total air volume of the cable to be detected to the reference volume, to obtain the air ratio of the cable to be detected, comparing the air ratio of the cable to be detected with the ablation defect ratio threshold of the buffer layer, whether the buffer layer of the cable to be detected has ablation defects or not is judged, and therefore the ablation defect condition of the cable buffer layer can be accurately detected.

In another embodiment, extensive fault analysis has found that a vertical cable section below a cable terminal is longer, the dead weight of the cable is larger, and if the holding force of the corrugated sheath on the insulated wire core is insufficient, the terminal supporting spring force is insufficient due to the action of the cable gravity after long-term operation, so that an air gap is generated between the stress cone and the epoxy sleeve to discharge, and thus a fault is caused. Although a plurality of vertical fixing devices are arranged by a construction unit according to anti-accident measures, the vertical hoops only tightly hold the cable sheaths, the tight holding force of the corrugated sheaths on the internal buffer layers and the insulated wire cores is only related to the structure of the cable, the number of the vertical hoops is irrelevant, and the air volume between the corrugated sheaths and the buffer layers is a quantitative index visually reflecting the tight holding force of the corrugated sheaths on the insulated wire cores. In step S4, the defect ratio threshold may be a defect ratio threshold including a holding force, and accordingly, the faulty cable may be a faulty cable including a corrugated sheath with insufficient holding force on the insulated wire core, and the defect ratio threshold may be configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the faulty cable with insufficient holding force on the insulated wire core by at least one corrugated sheath to a reference volume, so that the embodiment of the present invention obtains the air ratio of the cable to be detected by obtaining the total air volume between the corrugated sheath and the buffer layer of the cable to be detected and the reference volume of the cable to be detected, and calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected, and then comparing the air ratio of the cable to be detected with the defect ratio threshold to determine whether the cable to be detected has a defect of insufficient holding force on the insulated wire core by the corrugated sheath, therefore, the defect of the holding force of the corrugated sheath of the cable buffer layer on the insulated wire core can be accurately detected.

As an alternative embodiment, the acquiring of the total air volume between the corrugated sheath and the buffer layer of the cable to be tested comprises:

s11, acquiring the total length of the cable to be detected and specification parameters within a single wrinkle pitch; wherein the specification parameters comprise an inside radius of the corrugated sheath, an outside radius of the buffer layer, a radius of the insulated wire core not wrapped around the buffer layer, the corrugated pitch, the corrugated depth and the thinnest point thickness of the buffer layer;

s12, obtaining the contact curved surface of the corrugated sheath and the buffer layer in a cylindrical coordinate systemρ-θ-ZAn approximate function expression of; the polar point of the cylindrical coordinate system is the center of the corrugated sheath, the polar axis is any radial direction of the center of the corrugated sheath, and the Z-axis direction is the axial direction of the cable;

s13, determining the angle of the contact critical point of the corrugated sheath and the buffer layer according to the thinnest point thickness of the buffer layer, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath;

s14, calculating the air volume between the wrinkle sheath and the buffer layer within a single wrinkle pitch according to one or more parameters of an air volume calculation formula, the approximate function expression, the contact critical point angle and the specification parameters; wherein the air volume calculation formula is determined according to the corresponding relation between the air volume between the corrugated sheath and the buffer layer, the internal volume of the corrugated sheath, the volume of the insulated wire core wrapped with the buffer layer and the volume of the stressed deformation part of the buffer layer;

and S15, calculating the total air volume between the wrinkle sheath and the buffer layer according to the air volume, the total length and the wrinkle pitch.

Referring to fig. 2, the cable according to the embodiment of the present invention includes a core (conductor) 10, a shielding layer 20, a corrugated sheath 40, and a buffer layer 30 disposed between the shielding layer 20 and the corrugated sheath 40, wherein the core (conductor) 10 and the shielding layer 20 constitute an insulated wire core. In specific implementation, the total length of the cable to be detected and the specification parameters within a single wrinkle pitch can be measured according to a factory test report or an actual measurement result of the cable. Wherein the total length of the cable to be testedd _cableInside radius of corrugated sheathd _OAOutside radius of the buffer layerd _O’CRadius of insulated wire core not wrapped with buffer layerd _O’BPitch of the corrugationsd _lenDepth of wrinklesd _depMinimum thickness of buffer layerd _BB’. Wherein the above-mentioned total length and the specification parameters within a single corrugation pitch may be nominal values. Referring to fig. 3 and 5, 41 denotes the outside of the corrugated sheath, 42 denotes the inside of the corrugated sheath, 31 denotes the outside of the cushion layer, and 32 denotes the inside of the cushion layer.

It should be noted that the actual wrinkles are consideredThe contact surface of the sheath and the buffer layer is a space curved surface, and the center of the corrugated sheath is positioned in the radial plane of the cableOFor origin, as shown in FIG. 3, can be established

Plane polar coordinates.O’The critical point of the buffer layer contacting with the corrugated sheath is marked as the center of a circle of the core of the cableAAndA’. As shown in FIG. 4, in

On the basis of plane coordinates, the axial direction of the cable is taken asZThe direction can establish a three-dimensional coordinate system, and the dotted line part in the figure is a schematic diagram of the contact surface of the buffer layer and the corrugated sheath. Obviously, within one corrugation pitch, the air volume can be calculated by the following equation:

wherein the content of the first and second substances,V _Ais the internal volume of the corrugated sheath;V _Bthe volume of the insulated wire core is wrapped with the buffer layer;V _Cis the volume of the force-deformed portion of the cushioning layer.V _AAndV _Care closely related to the function of the curved surface inside the corrugated sheath, and the embodiment obtains the contact curved surface in a cylindrical coordinate systemρ-θ-ZThe following approximate functional expression, in combination with one or more of the angle of the contact critical point and the specification parameters, can approximate the internal volume of the corrugated sheath and the volume of the force-deformed portion of the cushioning layer.

It should be noted that, because of the peak-valley position of the corrugated sheath, the following basic assumptions in accordance with engineering practice can be made for calculating the air volume between the corrugated sheath and the cushioning layer: the volume of air within each corrugation pitch is approximately the same; the effect of the angle of inclination of the wrinkles on the air volume is negligible. Then, the air volume between the corrugated sheath and the cushion layer at this time can be decomposed into the sum of the air volumes between the corrugated sheath and the cushion layer within each corrugated pitch. Since the individual corrugation pitch is small compared to the full length of the line, the volume of air at the ends of the cable less than one corrugation pitch can be approximated with a corresponding ratio. This gives:

in the formula (I), the compound is shown in the specification,V _totalis the total air volume of the cable;V _Uis the volume of air within a single corrugation pitch;d _cableis the total length of the cable;d _lenis the corrugation pitch.

At present, the influence caused by bending of a cable is ignored, and the difference between the cylindrical volume formed by the circle at the position of a wave trough on the inner side of the corrugated sheath along the axial direction of the cable and the cylindrical volume formed by the circle coated on the outer side of the buffer layer on the cable along the axial direction of the cable is used as the air volume in the intuitive estimation method of the air volume (hereinafter referred to as the air volume for short) between the corrugated sheath and the buffer layer. Furthermore, power cable suppliers generally use metal corrugated production lines to produce corrugated sheaths, and control the technical parameters of the sheath corrugation through two production parameters of the corrugation pitch and the corrugation depth, but the method cannot directly determine the shape parameters of smooth corrugations, which are typical of the curvature radius, and the contact mode with the buffer layer in the axial direction of the cable is generally discontinuous due to the peak-valley position of the corrugated sheath, and the problems are difficult to mathematically model and calculate the air volume between the corrugated sheath and the buffer layer. Secondly, at present, the corrugated sheath and the buffer layer still lack corresponding standard constraints in the aspect of size matching, and under the condition of comprehensively considering various performance requirements such as cable mechanical strength, axial water blocking and the like, different power cable suppliers adopt different technical schemes on the problem that whether the diameter of the 'wave trough' on the inner side of the corrugated sheath is larger than the diameter of the outer side of the cable containing the buffer layer or not, so that under the action of gravity, the inner side of the corrugated sheath above the cable of one part of suppliers does not form effective contact with the buffer layer, as shown in fig. 3, the inner side of the corrugated sheath above the cable of the other part of suppliers forms effective contact with the buffer layer, as shown in fig. 5, obviously, an air volume calculation method capable of considering both conditions is needed. In addition, because the early cable lacks information such as factory test reports, the basic data of the cable is incomplete, enough information is difficult to provide for calculating the air volume, the air volume cannot be accurately calculated, and the defect that whether the cable buffer layer is ablated or not cannot be accurately judged. To solve the above problems, the present embodiment can accurately calculate the total air volume between the corrugated sheath and the cushion layer by calculating the air volume of the corrugated sheath and the cushion layer within a single corrugated pitch, and then combining the total length and the corrugated pitch.

Further, the contact curved surface of the corrugated sheath and the buffer layer is obtained in a cylindrical coordinate systemρ-θ-ZThe following approximate functional expression, comprising:

s121, based on cylindrical coordinate systemρ-θ-ZSelecting n interpolation data points from the contact curved surface of the wrinkle sheath and the buffer layer; wherein the coordinates of the kth interpolated data point is

，k=1，…，n；

S122, carrying out interpolation calculation according to the n interpolation data points to obtain the contact curved surface in the cylindrical coordinate systemρ-θ-ZThe following approximate function expression.

Note that, as shown in fig. 4, the following description refers to

Is curved in contact withzProjection on the plane of =0, for arbitrary points

Noting its coordinates as

. In thatzOn the plane of =0, from the originODirection pointPMaking rays, and marking the intersection point of the rays and the outside of the insulated wire core asB(ii) a The outer intersection point with the buffer layer is marked asC(ii) a The inside intersection with the corrugated sheath is notedD(ii) a The contact critical points of the wrinkle sheath and the buffer layer in the single wrinkle pitch are respectivelyE、FTwo points are included; the projection of the maximum point of the inside diameter of the corrugated sheath in the ray direction isKAnd (4) point. In the axial direction of the cable, by fitting a corrugated curveEDFAnd performing approximation to obtain an approximate curved surface of the contact curved surface of the corrugated sheath and the buffer layer. Illustratively, polynomial interpolation, triangular interpolation and the like can be applied to the curve inside the wrinkle sheathDEAn approximation is made. After determining the interpolation method, an interpolation base point may be determined

K =1, …, n, n is the number of interpolation data points required by the selected interpolation method; for all k =1, …, n, on the cable of interest or the same batch of cables provided by the supplier, measuring the Z-direction coordinate of the inner side of the wrinkle at the k position of the interpolation base point of different wrinkles at multiple points, and obtaining the coordinate of the interpolation data point after averaging

(ii) a Carrying out interpolation calculation according to the n interpolation data points, thereby obtaining an approximate curved surface

Approximate function expression in interval

。

Specifically, a cubic polynomial interpolation method may be used, which requires 4 interpolated data points, and the approximation function expression is:

；

Of course, in the specific implementation, other interpolation methods such as triangular interpolation and the like can be selected for the curve inside the wrinkle sheathDEThe approximation is performed to obtain different forms of approximation function expressions, and the expression form of the approximation function expression is not limited herein.

Further, the air volume calculation formula is:

；

wherein the content of the first and second substances,

；d _OArepresents the inside radius of the corrugated sheath;d _O’Crepresents an outside radius of the buffer layer;d _O’Brepresents a radius of the insulated wire core;d _deprepresenting the wrinkle depth;d _lenrepresenting the wrinkle pitch;d _BB’represents the thinnest point thickness of the buffer layer;f(ρ)representing the approximate function expression;θ _Arepresenting the angle of the critical point of contact.

It should be noted that the corrugated sheath is curved insidezProjection on the plane of =0

The direction is linearly symmetrical, and the inner side surface in the single corrugation pitch is curvedz=0 plane symmetry, so calculationV _AAndV _Cneed only be at

The interval completion volume calculation is multiplied by 4 times. Triple integral pairs using cylindrical coordinate systemV _A，V _BAndV _Ccan carry out calculationObtaining:

。

wherein the content of the first and second substances,d _OKthe inside maximum radius of the corrugated sheath;d _ODis the inside minimum radius of the corrugated sheath;d _OCis the originOToCThe distance of the points.

In terms of upper and lower limits of integration, it is easy to know that

In the direction of the air flow, the air flow is in a straight line,BDthe distance between the two points has the minimum value, which is the thickness of the thinnest point extruded by the buffer layer under the action of gravity and is recorded asd _BB’. It can be found that:

wherein the content of the first and second substances,d _OO’is the distance between the two circle centers.

According to the cosine theorem it can be found that:

due to the fact thatd _OC>0, derived:

according toV _A、V _B、V _CAndd _OCand is combined with

An approximate definite integral expression of the air volume within a single wrinkle pitch may be obtained, that is, the air volume calculation formula is specifically:

。

in specific implementation, the air volume calculation formula can be solved by using a numerical integration method, for example, a trapezoidal method, a simpson's law, a newton-costs formula, a longbeck method, a gaussian integration method, a chebyshev integration method, a monte carlo integration method and other numerical integration methods and improved forms thereof can be used for solving the air volume calculation formula, so that an approximate value of the air volume between the corrugated sheath and the buffer layer in a single corrugated pitch is obtained, and an approximate value of the total air volume of the whole cable section is obtained.

Alternatively, as shown in FIG. 6, note

Is curved in contact withzProjection on the plane of =0, for arbitrary points

Noting its coordinates as

. In thatzOn the plane of =0, from the originODirection pointPMaking rays, and marking the intersection point of the rays and the outside of the insulated wire core asB(ii) a The outer intersection point with the buffer layer is marked asC(ii) a The inside intersection with the corrugated sheath is notedD(ii) a The contact critical points of the wrinkle sheath and the buffer layer in the single wrinkle pitch are respectivelyE、FTwo points are included; the projection of the maximum point of the inside diameter of the corrugated sheath in the ray direction isKAnd (4) point. In the axial direction of the cableIn the direction of the curve passing through the wrinklesEDFAnd performing approximation to obtain an approximate curved surface of the contact curved surface of the corrugated sheath and the buffer layer. Can obtain an approximate curved surface

The function expression in the interval, that is, the approximate function expression, specifically is:

；

On this basis, the specification parameters also include the maximum distance, in a radial plane, from the centre of the corrugated sheath to the outside of the cushioning layer. As shown in FIG. 6, the wrinkle curve is approximated by a straight line connecting the peak and valley positions of the wrinkles in the axial direction of the cable, since the inner curved surface of the wrinkle sheath is at the position of the inner curved surface of the wrinkle sheathzProjection on the plane of =0

The interval is completed by multiplying the volume calculation by 4 times, and then, when the approximate function expression is

In time, a cylindrical coordinate system is adopted to form a triple integral pairV _A，V _BAndV _Cthe following calculation is carried out:

and are combined with

And

the air volume calculation formula can be obtained as follows:

；

wherein the content of the first and second substances,d _O’Crepresents an outside radius of the buffer layer;d _OCrepresents the maximum distance from the center of the corrugated sheath to the outside of the cushioning layer;d _BB’represents the thinnest point thickness of the buffer layer;θ _Arepresenting the angle of the critical point of contact.

Further, the determining an angle of a contact critical point of the corrugated sheath with the buffer layer according to the thinnest point thickness of the buffer layer, the radius of the insulated wire core, the outside radius of the buffer layer and the inside radius of the corrugated sheath includes:

s131, judging whether the thickness of the thinnest point of the buffer layer, the sum of the radius of the insulated wire core and the outer radius of the buffer layer are smaller than or equal to two times of the inner radius of the corrugated sheath or not;

s132, if so, calculating to obtain the angle of the contact critical point of the corrugated sheath and the buffer layer according to the calculation formula of the inner radius of the corrugated sheath, the outer radius of the buffer layer, the radius of the insulated wire core, the thinnest point thickness of the buffer layer and the contact critical point angle;

s133, if not, determining that the angle of the contact critical point of the wrinkle sheath and the buffer layer is equal to pi;

wherein, the contact critical point angle calculation formula is as follows:

；

It is noted that, with reference to fig. 4, in the case of no contact between the corrugated sheath and the buffer layer above the cable, i.e. in the case of a cable with a corrugated sheath of the same typed _BB’+d _O‘B+d _O’C≤2d _OAAt the contact critical point of the corrugated sheath and the buffer layerAThe method comprises the following steps:

. Obviously, in the case of contact between the corrugated sheath and the buffer layer over the cableI.e. byd _BB’+d _O’B+d _O‘C>2d _OAWhen there is

。

As one of the alternative embodiments, the gauge parameters further include an inside maximum radius and an inside minimum radius of the corrugated sheath;

s211, calculating to obtain a first volume corresponding to the cable to be detected according to the wrinkle pitch, the maximum radius of the inner side of the wrinkle sheath, the minimum radius of the inner side of the wrinkle sheath, the approximate function expression and a calculation formula for calculating the first volume of the insulated wire cores which are not wrapped with the buffer layer in the single wrinkle pitch;

s212, calculating the total internal volume of the corrugated sheath according to the first volume, the total length and the corrugated pitch corresponding to the cable to be detected, and taking the total internal volume as the reference volume of the cable to be detected;

wherein the first volumeV _AThe calculation formula of (2) is as follows:

；

It should be noted that, in the following description,V _Athe derivation process of the calculation formula may refer to the foregoing embodiments, and is not described herein again.

Wherein the electricity to be detectedReference volume of cableV _baseAs shown in the following formula:

。

as an optional embodiment, when the reference volume is the total volume of the insulated wire core wrapped with the buffer layer, the obtaining of the reference volume of the cable to be detected includes:

s221, calculating to obtain a second volume corresponding to the cable to be detected according to the outer radius of the buffer layer, the wrinkle pitch and a calculation formula for calculating the second volume of the insulating wire core wrapped with the buffer layer in the single wrinkle pitch;

s222, calculating to obtain the total volume of the insulated wire core wrapped with the buffer layer according to the second volume corresponding to the cable to be detected, the total length and the wrinkle pitch, and taking the total volume as the reference volume of the cable to be detected;

wherein the calculation formula of the second volume is:

；

It should be noted that, in the following description,V _Bthe derivation process of the calculation formula may refer to the foregoing embodiments, and is not described herein again.

Wherein the reference volume of the cable to be detectedV _baseAs shown in the following formula:

。

as an optional embodiment, the method further comprises:

s1', obtaining a total air volume between the corrugated jacket and the buffer layer of the plurality of faulty cables;

s2', obtaining the reference volume of the fault cables;

s3', calculating the ratio of the total air volume of the fault cables to the reference volume to obtain the air ratio of the fault cables;

s4', selecting the minimum value of the air ratios of the plurality of faulty cables as the defect ratio threshold.

In one embodiment, the cable has defects including a buffer layer ablation defect and insufficient holding force of the corrugated sheath on the insulated wire core, and the defect ratio threshold may be a buffer layer ablation defect ratio threshold, and accordingly, the faulty cable may be a faulty cable including the occurrence of buffer layer ablation, and the buffer layer ablation defect ratio threshold may be obtained by selecting the minimum value of the air ratios of the faulty cables having the occurrence of buffer layer ablation.

In another embodiment, the cable may have a defect that includes insufficient holding force of the corrugated sheath against the insulated core, and the defect ratio threshold may be a defect ratio threshold that includes the holding force, and accordingly, the faulty cable may be a faulty cable that includes insufficient holding force of the corrugated sheath against the insulated core, and the holding force defect ratio threshold may be obtained by selecting a minimum value of air ratios of the faulty cables that have insufficient holding force.

It should be noted that, in steps S1 'to S3', the specific calculation method and principle of the total air volume, the reference volume, and the ratio of the total air volume to the reference volume of each faulty cable may refer to the related descriptions in steps S1 to S3 of the foregoing embodiment, and are not described herein again.

As an optional embodiment, the method further comprises:

s5, when the cable to be detected is judged to have defects, adding the cable to be detected into a risk list;

and S6, outputting the risk list to a setting terminal when the risk list output condition is determined to be satisfied.

The risk list output condition may be set according to actual requirements, for example, set to determine that the number of detections reaches a set number, or set to receive a risk list acquisition request sent by a user.

In a specific implementation, the risk list may include information of a plurality of cables to be detected with a defect in the buffer layer.

In this embodiment, when it is determined that the cable to be detected has a defect, the risk list is output to a setting terminal, so that relevant personnel can timely receive defect feedback and timely process the defect.

The method for detecting defects of the cable provided by the present embodiment is described below with three specific embodiments.

The first embodiment is as follows:

a1', acquiring the total air volume between the corrugated sheath and the buffer layer of a plurality of fault cables (fault cables) with buffer layer ablation, specifically comprising the steps A11' to A15 ':

a11', obtaining the total length of the multiple faulty cables and the specification parameters within a single corrugation pitch, as shown in table 1;

TABLE 1 fundamental data of faulty cables

A12', obtaining the contact curved surface of the corrugated sheath and the buffer layer in a cylindrical coordinate systemρ-θ-ZThe following approximate function expression specifically comprises the following steps of A121 'to A122':

a121', since a cubic polynomial interpolation method is used, 4 interpolated data points are required in this embodiment, which is based on a cylindrical coordinate systemρ-θ-ZIn a

The average distribution on the interval obtains an interpolation base point

，k=1, …,4, for allk=1, …,4, inInterpolation of base points in different wrinkles on faulty cables

Position multipoint measurement of wrinkle insideZDirection coordinates, the coordinates of the interpolated data points being obtained after averaging

The coordinates of the interpolated data points obtained after measurement are shown in table 2:

TABLE 2 interpolated data point coordinates for each faulty cable

Interpolated data points	Interpolated data point 1	Interpolated data points 2	Interpolated data points 3	Interpolated data points 4
					Section a of trouble	(0.0650, 0, 0)	(0.0671, 0, 0.0060)	(0.0691, 0, 0.0089)	(0.0712, 0, 0.0160)
Section B of fault	(0.0606, 0, 0)	(0.0627, 0, 0.0061)	(0.0649, 0, 0.0089)	(0.0670, 0, 0.0140)
					Third stage of failure	(0.0590, 0, 0)	(0.0611, 0, 0.0060)	(0.0631, 0, 0.0092)	(0.0652, 0, 0.0150)

A122' from the interpolated data points

，kPerforming interpolation calculation to obtain an approximate function expression of the contact curved surface of each fault cable in a cylindrical coordinate system rho-theta-Z

(ii) a Wherein the coefficients of the approximate functional expression for each faulty cable are shown in table 3.

TABLE 3 coefficients of approximate function expressions for each faulty cable

A13', determining the angle of the contact critical point of the corrugated sheath and the buffer layer of each fault cable according to the thinnest point thickness of the buffer layer of each fault cable, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath, and specifically comprising the steps A131' to A133 '.

A131' for each fault cable, by formula

Calculating the distance between two circle centersd _OO’And make a judgment ond _BB’+ d _O‘B + d _O’C ≤ 2d _OAWhether or not this is true.

A132', if true, the corrugated sheath and the buffer layer are not in contact above the cable, and the contact critical point angle of the corrugated sheath and the buffer layer

；

A133', if not, the corrugated sheath on the cable is effectively contacted with the buffer layer,

。

the calculation results of the faulty cables are shown in table 4.

Table 4 calculation results of contact critical point angle of each faulty cable

A14', calculating the air volume between the corrugated sheath and the buffer layer within a single corrugated pitch according to the air volume calculation formula, the approximate function expression, the angle of the contact critical point and one or more of the specification parameters for each faulty cable, and calculating the air volume between the corrugated sheath and the buffer layer according to the following air volume calculation formulaV _USimplifying the double integral, then applying a numerical integration method to obtain the product by calculationV _U。

A15', based on air volume, total length and corrugation pitch, for each faulty cable according to the formula

Calculating to obtain the total air volume between the corrugated sheath and the buffer layerV _total。

A2', obtaining reference volumes of a plurality of fault cables, specifically:

to alli=1, …, 3, according to formula

Calculating a reference volume to obtain

。

A3', calculating the ratio of the total air volume of the plurality of fault cables to the reference volume to obtain the air ratio of the plurality of fault cables, specifically:

according to the formula

Air ratio calculation is carried out to obtainw(l _i)。

The calculation results of the above steps a14', a15', a2 'and A3' are shown in table 5.

TABLE 5 calculation results of steps A14', A15', A2' and A3

A4', calculating the air ratio set of the fault cable section

According to the formula

Selecting the minimum value of the air ratios of the fault cables as a defect ratio threshold valuet. In this particular embodiment, the calculation may be such that,t=7.5476%。

a1, Cable set to be tested for 220kV voltage class

To all ofj=1, …,4, obtaining the total air volume between the corrugated sheath and the buffer layer of each cable to be tested, comprising in particular the steps a11 to a 15:

a11, acquiring the total length of a plurality of cables to be detected and specification parameters within a single wrinkle pitch, as shown in Table 6;

TABLE 6 basic data of the cables to be tested

A12, obtaining the contact curved surface of the corrugated sheath and the buffer layer of a plurality of cables to be detected in a cylindrical coordinate systemρ-θ-ZThe following approximate function expression, the specific steps include a121 to a 122:

a121, since a cubic polynomial interpolation method is used, 4 interpolated data points are required in the embodiment, which is based on a cylindrical coordinate systemρ-θ-ZIn a

The average distribution on the interval obtains an interpolation base point

，k=1, …,4, for allk=1, …,4, interpolation of base points in different wrinkles on each cable to be tested

The coordinates of the interpolated data points obtained after measurement are shown in table 7:

TABLE 7 interpolated data point coordinates for each cable to be tested

Interpolated data points	Interpolated data point 1	Interpolated data points 2	Interpolated data points 3	Interpolated data points 4
					In the nail transporting section	(0.0608, 0, 0)	(0.0628, 0, 0.0060)	(0.0648, 0, 0.0090)	(0.0668, 0, 0.0150)
In the second section of transportation	(0.0562, 0, 0)	(0.0580, 0, 0.0060)	(0.0599, 0, 0.0090)	(0.0617, 0, 0.0145)
					In the third stage of transportation	(0.0590, 0, 0)	(0.0609, 0, 0.0061)	(0.0627, 0, 0.0093)	(0.0646, 0, 0.0160)
In the D conveying section	(0.0600, 0, 0)	(0.0619, 0, 0.0059)	(0.0637, 0, 0.0089)	(0.0656, 0, 0.0140)

A122, according to the interpolation data point

，kPerforming interpolation calculation on the (= 1, …, 4) to obtain an approximate function expression of the contact curved surface of each cable to be detected under the cylindrical coordinate system rho-theta-Z

(ii) a Wherein, the coefficients of the approximate function expression of each cable to be detected are shown in table 8.

TABLE 8 coefficients of approximate function expressions for each cable to be tested

A13, determining the angle of the contact critical point of the corrugated sheath and the buffer layer of each cable to be detected according to the thinnest point thickness of the buffer layer of each cable to be detected, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath, and specifically comprising the steps A131 to A133.

A131, for each cable to be detected, using the formula

A132, if true, the corrugated sheath and the buffer layer are not in contact above the cable, and the contact critical point angle of the corrugated sheath and the buffer layer

；

A133, if the cable is not erected, the corrugated sheath on the cable is effectively contacted with the buffer layer,

。

the calculation results of the cables to be tested are shown in table 9.

TABLE 9 calculation results of contact critical point angle of each cable to be tested

A14, for each cable to be detected, calculating the air volume between the corrugated sheath and the buffer layer within a single corrugated pitch according to one or more of the air volume calculation formula, the approximate function expression, the angle of the contact critical point and the specification parameters, and calculating the air volume between the corrugated sheath and the buffer layer according to the following air volume calculation formulaV _USimplifying the double integral, then applying a numerical integration method to obtain the product by calculationV _U。

A15, for each cable to be tested, based on air volume, total length and corrugation pitch, according to the formula

A2, obtaining the reference volume of a plurality of cables to be detected, specifically:

to allj=1, …,4, according to formula

Calculating a reference volume to obtain

。

A3, calculating the ratio of the total air volume of the cables to be detected to the reference volume to obtain the air ratio of the cables to be detected, which specifically comprises the following steps:

to allj=1, …,4, according to formula

Air ratio calculation is carried out to obtainw(q _j)。

Wherein, the calculation results of the above steps a14, a15, a2 and A3 are shown in table 10.

TABLE 10 calculation of steps A14, A15, A2 and A3

A4, summarizing and calculating to obtain a cable section air ratio set to be screened

To all ofj=1, …,4, making the following judgments: if it is

Then, it is determinedq _jThe defect of buffer layer ablation exists, otherwise, the judgment is madeq _jThe buffer layer ablation defect does not exist;

a5, to allj=1, …,4, when judgedq _jWhen the ablation defect of the buffer layer exists, the buffer layer isq _jAdding the risk list into the risk list to obtain a risk list as follows: { in the first transportation stage, in the second transportation stage };

a6, when determining that the risk list output condition is satisfied, outputting the risk list to the setting terminal.

The second embodiment is as follows:

a11', the total length of the multiple faulty cables and the specification parameters within a single corrugation pitch were obtained, as shown in table 11.

TABLE 11 fundamental data of faulty cables

A12', obtaining the contact curved surface of the corrugated sheath and the buffer layer in a cylindrical coordinate systemρ-θ-ZApproximate function expression of

。

A131' for each fault cable, by formula

；

。

the calculation results of the faulty cables are shown in table 12.

TABLE 12 calculation results of contact critical point angle of each faulty cable

A2', obtaining reference volumes of a plurality of fault cables, specifically:

to alli=1, …, 3, according to formula

Calculating a reference volume to obtain

。

A3' according to the formula

Calculating the ratio of the total air volume of a plurality of fault cables to the reference volume to obtain the air ratio of the plurality of fault cablesw(l _i)。

The calculation results of the above steps a14', a15', a2 'and A3' are shown in table 13.

TABLE 13 calculation of steps A14', A15', A2' and A3

A4', calculating the air ratio set of the fault cable section

According to the formula

Selecting the minimum value of the air ratios of the fault cables as a defect ratio threshold valuet. In this particular embodiment, the calculation may be such that,t=7.5114%。

a1, Cable set to be tested for 220kV voltage class

To all ofj=1, …,4, the total air volume between the corrugated sheath and the buffer layer of each cable to be tested is taken.

A11, acquiring the total length of a plurality of cables to be detected and specification parameters within a single corrugation pitch, as shown in table 14;

TABLE 14 basic data for each cable to be tested

A12, obtaining the contact curved surface of the corrugated sheath and the buffer layer of a plurality of cables to be detected in a cylindrical coordinate systemρ-θ-ZApproximate function expression of

。

A131, for each cable to be detected, using the formula

；

。

the calculation results of the cables to be tested are shown in table 15.

TABLE 15 calculation results of contact critical point angle of each cable to be tested

A15, air-based for each cable to be detectedVolume, total length and corrugation pitch according to the formula

to allj=1, …,4, according to formula

Calculating a reference volume to obtain

。

to allj=1, …,4, according to formula

Air ratio calculation is carried out to obtainw(q _j)。

The results of the steps a14, a15, a2 and A3 are shown in table 16.

TABLE 16 calculation of steps A14, A15, A2 and A3

To all ofj=1, …,4, making the following judgments: if it is

Then, it is determinedq _jWith buffer layer firingEtching defect, otherwise, judgingq _jThe buffer layer ablation defect does not exist;

The third concrete embodiment:

a10', obtaining fault cablel _iTotal length of the corrugated sheet and specification parameters within a single corrugation pitch, as shown in table 17;

TABLE 17 fundamental data of faulty cables

A11' for alli=1, …,4, inquiry fault cablel _iIf the calculation result record of the air ratio exists before and the basic data acquired in the step a10 'is the same as the historical data, if the calculation result record of the air ratio exists and the basic data acquired in the step a10' is the same as the historical data, the calculation result record of the faulty cable is directly acquired as the air ratio, if the calculation result record of the air ratio does not exist or the basic data acquired in the step a10 'is not the same as the historical data, the steps a12' to A3 'are executed to obtain the air ratio of the faulty cable, and after the air ratios of all the faulty cables are obtained, the process proceeds to a 4'.

。

A13', determining the angle of the critical contact point of the corrugated sheath and the buffer layer of the fault cable according to the thinnest point thickness of the buffer layer of the fault cable, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath, and particularly comprising the steps a131' to a133 '.

A131' expressed by the formula

A132', if true, the corrugated sheath and the buffer layer are not in contact above the faulty cable, the critical point angle of contact between the corrugated sheath and the buffer layer

；

。

the calculation results of the faulty cables are shown in table 18.

TABLE 18 calculation of contact critical point angle for each faulty cable

A14', calculating the air volume between the corrugated sheath and the cushioning layer within a single corrugation pitch according to one or more of the air volume calculation formula, the approximate function expression, the contact critical point angle and the specification parameters, and calculating the following air volume calculation formulaV _USimplifying the double integral, then applying a numerical integration method to obtain the product by calculationV _U。

A15' based on air volume, total length and corrugation pitch, according to the formula

A2', obtaining the reference volume of the fault cable, specifically:

according to the formula

Calculating a reference volume to obtain

。

A3' according to the formula

Calculating the ratio of the total air volume of the fault cable to the reference volume to obtain the air ratio of the fault cablew(l _i)。

The calculation results of the above steps a14', a15', a2 'and A3' are shown in table 19.

TABLE 19 calculation of steps A14', A15', A2' and A3

A4', calculating the air ratio set of the fault cable section

According to the formula

Selecting the minimum value of the air ratios of the fault cables as a defect ratio threshold valuet. In this particular embodiment, the calculation may be such that,t=7.0258%。

a10, for 220kV voltage classDetecting cable assemblies

To all ofj=1, …, 3, total length of multiple cables to be detected and specification parameters within a single corrugation pitch are obtained, as shown in table 20;

TABLE 20 basic data for each cable to be tested

A11, for allj=1, …, 3, inquiry cable to be detectedq _jIf the calculation result record of the air ratio exists before and the basic data acquired in the step a10 'is the same as the historical data, if the calculation result record of the air ratio exists and the basic data acquired in the step a10' is the same as the historical data, directly acquiring the calculation result record of the cable to be detected as the air ratio, and if the calculation result record of the air ratio does not exist or the basic data acquired in the step a10 is not the same as the historical data, executing a12 to A3 to obtain the air ratio of the cable to be detected; after the air ratios of all cables to be tested are obtained, the process proceeds to step a 4. In the present embodiment, forj=1, …, 3, air ratio has saved result and the data required by air volume calculation method is not different from historical data, can directly getw(q _j) And proceeds to step a 4.

A12, obtaining the contact curved surface of the corrugated sheath and the buffer layer of the cable to be detected in a cylindrical coordinate systemρ-θ-ZApproximate function expression of

。

A131, for each cable to be detected, using the formula

；

。

A2, acquiring the reference volume of the cable to be detected, specifically:

according to the formula

Calculating a reference volume to obtain

。

A3, calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected, which is specifically as follows:

according to the formula

Air ratio calculation is carried out to obtainw(q _j)。

The air ratio of each cable to be tested is shown in table 21. To allj=1, …, 3, making the following judgments: if it is

Then, it is determinedq _jThe defect of buffer layer ablation exists, otherwise, the judgment is madeq _jThere is no buffer layer ablation defect.

TABLE 21 air ratio of cables to be tested

Cable segment name	Air ratio w (%)
		In the second section of transportation	19.6336
In the third stage of transportation	6.2844
		In the D conveying section	1.7596

A5, to allj=1, …, 3, when judgedq _jWhen the ablation defect of the buffer layer exists, the buffer layer isq _jAdding the risk list into the risk list to obtain a risk list as follows: { in second segment }.

It should be noted that, a scenario addressed by the third specific embodiment is a case where, when it is detected that a buffer layer of a cable in the first segment of transport has a defect, after actual measurement and data updating are performed on a fault segment in the first segment of transport, buffer layer ablation risk cable segment screening needs to be performed again.

Referring to fig. 7, fig. 7 is a block diagram of a defect detection apparatus for a cable according to an embodiment of the present invention.

The defect detection device of the cable provided by the embodiment comprises:

the air volume acquisition module 21 is used for acquiring the total air volume between the corrugated sheath and the buffer layer of the cable to be detected;

a reference volume obtaining module 22, configured to obtain a reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath;

the air ratio calculation module 23 is configured to calculate a ratio of a total air volume of the cable to be detected to a reference volume, so as to obtain an air ratio of the cable to be detected;

the defect judging module 24 is configured to judge whether the air ratio of the cable to be detected is greater than or equal to a defect ratio threshold, determine that the cable to be detected has a defect if the air ratio of the cable to be detected is greater than or equal to the defect ratio threshold, and determine that the cable to be detected does not have a defect if the air ratio of the cable to be detected is not greater than the defect ratio threshold; wherein the defect ratio threshold is configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the at least one faulty cable to a baseline volume.

As one optional embodiment, the air volume obtaining module specifically includes:

the parameter acquisition unit is used for acquiring the total length of the cable to be detected and specification parameters within a single wrinkle pitch; wherein the specification parameters comprise an inside radius of the corrugated sheath, an outside radius of the buffer layer, a radius of the insulated wire core not wrapped around the buffer layer, the corrugated pitch, the corrugated depth and the thinnest point thickness of the buffer layer;

a function obtaining unit for obtaining the contact curved surface of the wrinkle sheath and the buffer layer in a cylindrical coordinate systemρ-θ- ZAn approximate function expression of; the polar point of the cylindrical coordinate system is the center of the corrugated sheath, the polar axis is any radial direction of the center of the corrugated sheath, and the Z-axis direction is the axial direction of the cable;

the angle acquisition unit is used for determining the angle of the contact critical point of the corrugated sheath and the buffer layer according to the thinnest point thickness of the buffer layer, the radius of the insulated wire core, the outer radius of the buffer layer and the inner radius of the corrugated sheath;

a first volume obtaining unit for calculating an air volume between the wrinkle sheath and the cushion layer within a single wrinkle pitch according to one or more of an air volume calculation formula, the approximate function expression, the angle of the contact critical point, and the specification parameter; wherein the air volume calculation formula is determined according to the corresponding relation between the air volume between the corrugated sheath and the buffer layer, the internal volume of the corrugated sheath, the volume of the insulated wire core wrapped with the buffer layer and the volume of the stressed deformation part of the buffer layer;

and the second volume acquisition unit is used for calculating and obtaining the total air volume between the wrinkle sheath and the buffer layer according to the air volume, the total length and the wrinkle pitch.

Further, the function obtaining unit is specifically configured to:

，k=1，…，n；

Further, the air volume calculation formula is:

；

wherein the content of the first and second substances,

Further, the approximation function expression is:

；

Optionally, the approximate function expression is:

；

Further, the gauge parameters further include a maximum distance, in a radial plane, from a center of the corrugated sheath to an outer side of the cushioning layer;

when the approximate function expression is

The air volume calculation formula is as follows:

；

wherein the content of the first and second substances,d _O’Crepresents an outside radius of the buffer layer;d _OCrepresents the maximum distance from the center of the corrugated sheath to the outside of the cushioning layer;θ _Arepresenting the angle of the critical point of contact.

Further, the angle obtaining unit is specifically configured to:

wherein, the contact critical point angle calculation formula is as follows:

；

Further, the gauge parameters also include an inside maximum radius and an inside minimum radius of the corrugated sheath;

when the reference volume is the total internal volume of the corrugated sheath, the reference volume acquiring module is specifically configured to:

wherein the first volumeV _AThe calculation formula of (2) is as follows:

；

wherein the content of the first and second substances,V _Arepresents the firstA volume;d _lenrepresenting the wrinkle pitch;d _OKrepresents the inside maximum radius of the corrugated sheath;d _ODrepresents an inside minimum radius of the corrugated sheath;f(ρ)representing the approximate function expression.

Further, when the reference volume is the total volume of the insulated wire core wrapped with the buffer layer, the reference volume acquiring module is specifically configured to:

wherein the calculation formula of the second volume is:

；

As an optional embodiment, the apparatus further includes a threshold obtaining module, specifically configured to:

acquiring reference volumes of a plurality of fault cables;

As an optional embodiment, the apparatus further includes a risk list output module, specifically configured to:

The defect detection device for the cable disclosed by the embodiment of the invention can be used for judging whether the cable to be detected has defects or not by acquiring the total air volume between the corrugated sheath and the buffer layer of the cable to be detected and the reference volume of the cable to be detected, calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected, and judging whether the cable to be detected has defects or not according to the size relation between the air ratio of the cable to be detected and a defect ratio threshold value configured according to the ratio of the total air volume between the corrugated sheath and the buffer layer of at least one fault cable to the reference volume, thereby accurately detecting the defect condition of the cable.

Fig. 8 is a schematic structural diagram of a terminal device according to an embodiment of the present invention.

The terminal device provided by the embodiment of the present invention includes a processor 310, a memory 320, and a computer program stored in the memory 320 and configured to be executed by the processor 310, and when the processor 310 executes the computer program, the defect detection method for a cable according to any of the above embodiments is implemented.

The processor 310, when executing the computer program, implements the steps of the above-described embodiments of the method for defect detection of a cable, such as all the steps of the method for defect detection of a cable shown in fig. 1. Alternatively, the processor 310, when executing the computer program, implements the functions of each module/unit in the above-mentioned defect detecting apparatus for cables, for example, the functions of each module of the defect detecting apparatus for cables shown in fig. 7.

Illustratively, the computer program may be partitioned into one or more modules that are stored in the memory 320 and executed by the processor 310 to implement the present invention. The one or more modules may be a series of computer program instruction segments capable of performing specific functions, which are used for describing the execution process of the computer program in the terminal device. For example, the computer program may be divided into an air volume obtaining module, a reference volume obtaining module, an air ratio calculating module and a defect determining module, and each module has the following specific functions: the air volume acquisition module is used for acquiring the total air volume between the corrugated sheath and the buffer layer of the cable to be detected; the reference volume acquisition module is used for acquiring the reference volume of the cable to be detected; the reference volume is the total volume of the insulated wire core which is not wrapped with the buffer layer, the total volume of the insulated wire core wrapped with the buffer layer or the total volume of the inside of the corrugated sheath; the air ratio calculation module is used for calculating the ratio of the total air volume of the cable to be detected to the reference volume to obtain the air ratio of the cable to be detected; the defect judging module is used for judging whether the air ratio of the cable to be detected is greater than or equal to a defect ratio threshold value, if so, judging that the cable to be detected has defects, and if not, judging that the cable to be detected does not have defects; wherein the defect ratio threshold is configured according to a ratio of a total air volume between the corrugated sheath and the buffer layer of the at least one faulty cable to a baseline volume.

The terminal device can be a desktop computer, a notebook, a palm computer, a cloud server and other computing devices. The terminal device may include, but is not limited to, a processor 310, a memory 320. It will be appreciated by those skilled in the art that the schematic diagram is merely an example of a terminal device and does not constitute a limitation of a terminal device, and may include more or less components than those shown, or combine certain components, or different components, for example, the terminal device may also include input output devices, network access devices, buses, etc.

The Processor 310 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, and the processor 310 is the control center of the terminal device and connects the various parts of the whole terminal device by various interfaces and lines.

The memory 320 can be used for storing the computer programs and/or modules, and the processor 310 can implement various functions of the terminal device by running or executing the computer programs and/or modules stored in the memory 320 and calling the data stored in the memory 320. The memory 320 may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data (such as audio data, a phonebook, etc.) created according to the use of the terminal device, and the like. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.

Wherein, the terminal device integrated module/unit can be stored in a computer readable storage medium if it is implemented in the form of software functional unit and sold or used as a stand-alone product. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.

It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A method of detecting defects in a cable, comprising:

2. The method of claim 1, wherein said obtaining a total air volume between a corrugated sheath and a buffer layer of a cable to be tested comprises:

3. The method for detecting defects in an electrical cable of claim 2, wherein said obtaining a curved contact surface of said corrugated sheath and said buffer layer is performed in a cylindrical coordinate systemρ-θ-ZThe following approximate functional expression, comprising:

，k=1，…，n；

4. The method for detecting defects in an electrical cable according to claim 3, wherein said air volume calculation formula is:

；

wherein the content of the first and second substances,

；

representing a volume of air between the corrugated sheath and the cushion layer within a single one of the corrugated pitches;d _OArepresents the inside radius of the corrugated sheath;d _O’Crepresents an outside radius of the buffer layer;d _O’Brepresents a radius of the insulated wire core;d _deprepresenting the wrinkle depth;d _lenrepresenting the wrinkle pitch;d _BB’represents the thinnest point thickness of the buffer layer;f(ρ)representing the approximate function expression;θ _Arepresenting the angle of the critical point of contact.

5. The method for detecting defects in an electrical cable according to claim 3, wherein said approximation function expression is:

；

6. The method for detecting defects in an electrical cable according to claim 2, wherein said approximation function expression is:

；

7. The method of defect detection of cable of claim 6, wherein said gauge parameters further include a maximum distance, in a radial plane, from a center of said corrugated jacket to an outer side of said buffer layer;

when the approximate function expression is

The air volume calculation formula is as follows:

；

wherein the content of the first and second substances,

representing a volume of air between the corrugated sheath and the cushion layer within a single one of the corrugated pitches;d _O’Crepresents an outside radius of the buffer layer;d _OCrepresents the maximum distance from the center of the corrugated sheath to the outside of the cushioning layer;θ _Arepresenting the angle of the critical point of contact.

8. The method of detecting defects in an electrical cable according to claim 2, wherein said determining an angle of a critical point of contact of said corrugated jacket with said buffer layer based on a thinnest point thickness of said buffer layer, a radius of said insulated wire core, an outside radius of said buffer layer, and an inside radius of said corrugated jacket comprises:

wherein, the contact critical point angle calculation formula is as follows:

；

9. The method of defect detection of cable of claim 2, wherein said gauge parameters further comprise an inside maximum radius and an inside minimum radius of said corrugated sheath;

wherein the calculation formula of the first volume is as follows:

；

10. The method for detecting the defects of the cable according to claim 2, wherein when the reference volume is the total volume of the insulated wire core wrapped with the buffer layer, the obtaining of the reference volume of the cable to be detected comprises:

wherein the calculation formula of the second volume is:

；

11. The method of defect detection of a cable according to claim 1, further comprising:

acquiring reference volumes of a plurality of fault cables;

12. The method of defect detection of a cable according to claim 1, further comprising:

13. A defect detection apparatus for a cable, comprising:

14. A terminal device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing a method of defect detection of a cable according to any one of claims 1 to 12 when executing the computer program.

15. A computer-readable storage medium, comprising a stored computer program, wherein the computer program, when executed, controls an apparatus in which the computer-readable storage medium is located to perform a method for defect detection of a cable according to any one of claims 1 to 12.