CN114113231B - Defect detection method, device, equipment and medium for cable corrugated metal sheath - Google Patents
Defect detection method, device, equipment and medium for cable corrugated metal sheath Download PDFInfo
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- CN114113231B CN114113231B CN202210097284.5A CN202210097284A CN114113231B CN 114113231 B CN114113231 B CN 114113231B CN 202210097284 A CN202210097284 A CN 202210097284A CN 114113231 B CN114113231 B CN 114113231B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/20—Investigating the presence of flaws
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
Abstract
The invention discloses a method, a device, equipment and a medium for detecting defects of a corrugated metal sheath of a cable, wherein the method comprises the following steps: acquiring specification parameters of a corrugated metal sheath of the cable; measuring the total direct current resistance value of the corrugated metal sheath, and collecting the ambient temperature; calculating the direct current resistance value of the corrugated metal sheath in a single corrugated pitch under the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch; acquiring an inner side surface arc equation of the corrugated metal sheath under a cylindrical coordinate system; calculating the electric conductivity of the corrugated metal sheath at a preset reference temperature according to the inner side surface arc equation, the direct current resistance value in the single corrugated pitch, the inner side minimum radius, the corrugated pitch and the radial thickness; and comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result. The embodiment of the invention can accurately detect the defect condition of the corrugated metal sheath of the cable.
Description
Technical Field
The invention relates to the technical field of power cables, in particular to a method, a device, equipment and a medium for detecting defects of a corrugated metal sheath of a cable.
Background
The corrugated metal sheath is an important component of a high-voltage power cable and bears a plurality of key tasks of improving the mechanical strength of the cable, realizing radial water resistance of the cable, ensuring good grounding of a shielding layer of the cable and the like. The size and the conductivity of the corrugated metal sheath are the keys for guaranteeing the electrical performance, at present, due to the lack of an effective corrugated metal sheath conductivity detection method, the performance detection of the corrugated aluminum sheath in the material detection stage of a power grid company mainly stays in the thickness detection, and the performance detection in the conductivity direction of the corrugated metal sheath is carried out only rarely, so that how to accurately detect the defects of the corrugated metal sheath is of great significance for the safe and reliable operation of a power system.
Disclosure of Invention
The embodiment of the invention provides a method, a device, equipment and a medium for detecting defects of a corrugated metal sheath of a cable, which can accurately calculate the conductivity of the corrugated metal sheath of the cable and accurately judge whether the corrugated metal sheath of the cable has defects or not according to the conductivity.
The embodiment of the invention provides a defect detection method of a corrugated metal sheath of a cable, which comprises the following steps:
acquiring specification parameters of a corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
measuring the total direct current resistance value of the corrugated metal sheath, and collecting the ambient temperature under the measuring environment;
calculating to obtain a direct current resistance value of the corrugated metal sheath in a single corrugated pitch at the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch;
obtaining the corrugated metal sheath in a cylindrical coordinate system
The lower inside surface arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
calculating the conductivity of the corrugated metal sheath at the preset reference temperature according to the equation of the inner side surface arc, the direct current resistance value in the single corrugated pitch, the inner minimum radius, the corrugated pitch and the radial thickness;
and comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath.
As an improvement of the above solution, the calculation formula of the dc resistance value in the single wrinkle pitch is:
wherein the content of the first and second substances,
is a dc resistance value within said single corrugation pitch,
as the value of the total direct current resistance,
is the pitch of the corrugations of the paper,
in order to be the temperature coefficient of resistance,
is the preset reference temperature, and the temperature of the air conditioner is controlled,
for the environmentThe temperature of the mixture is controlled by the temperature,
is the total length.
As an improvement of the above solution, the measuring of the total dc resistance value of the corrugated metal sheath includes:
both ends of the corrugated metal sheath are connected with a potential electrode and a current electrode;
connecting the two potential electrodes and the two current electrodes with a direct current resistance tester to perform resistance measurement for multiple times so as to obtain multiple resistance measurement values;
and taking the average value of the resistance measurement values as the total direct current resistance value.
As an improvement of the scheme, the corrugated metal sheath is obtained in a cylindrical coordinate system
The following equation for the camber line, comprising:
based on cylindrical coordinate system
Selecting n interpolated data points from the inside surface of the corrugated metal sheath; wherein the coordinates of the kth interpolated data point is
，k=1，…，n；
And carrying out interpolation calculation according to the n interpolation data points to obtain the inner side surface arc equation.
As an improvement of the above, said calculating the conductivity of said corrugated metal sheath at said preset reference temperature according to said equation of the inside surface arc, the value of the direct current resistance within said single corrugation pitch, said inside minimum radius, said corrugation pitch and said radial thickness comprises:
solving equations
At real number [0, dlen/2]The immobile points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein the content of the first and second substances,
is the equation for the arc of the inner side surface,
m is the number of the fixed points for the wrinkle pitch,
is the value of the ith stationary point;
if m is 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a first calculation formula of the conductivity;
if m is larger than 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a second calculation formula of the conductivity; the second calculation formula is obtained by performing integral correction on the first calculation formula;
the first calculation formula is:
the second calculation formula is:
wherein the content of the first and second substances,
in order to be said of the electrical conductivity,
for the single wrinkleThe value of the direct current resistance within the pitch,
is the smallest radius of the inner side and,
in order to be said radial thickness,
in order to integrate the correction values,
is the radius coordinate of any point on the radial section of the corrugated metal sheath.
As an improvement of the above scheme, the first calculation formula of the conductivity is established in the following manner:
in cylindrical coordinate system
Next, modeling the corrugated metal sheath within a single corrugation pitch;
carrying out resistance decomposition on the model to obtain a model subjected to resistance decomposition; the model after resistance decomposition is formed by connecting a plurality of metal wire resistors in parallel in the same direction as current, and each metal wire resistor is formed by connecting a plurality of infinitesimal resistors in series;
determining points on the resistance-decomposed model according to the resistance-decomposed model
Is defined as an arc equation of
；
According to the point
An arc equation and a conductivity calculation formula are established, and any point on the model after the resistance decomposition is established
The resistance value of the micro element resistor is calculated by the formula
(ii) a Wherein the content of the first and second substances,
is the resistance value of the micro element resistor;
according to the resistance value calculation formula of the infinitesimal resistor and the series resistance calculation formula, the resistance value calculation formula of the metal wire resistor is established as
(ii) a Wherein the content of the first and second substances,
is the resistance value of the wire resistor;
according to the resistance value calculation formula and the parallel resistance calculation formula of the metal wire resistor, the calculation formula for establishing the direct current resistance value in the single wrinkle pitch is
；
And deducing to obtain a first calculation formula of the conductivity according to a calculation formula of the direct current resistance value in the single wrinkle pitch.
As an improvement of the above solution, before the comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath, the method further includes:
and calculating a sum value between the conductivity and a preset error threshold value, and correcting the conductivity into the sum value.
Accordingly, another embodiment of the present invention provides a defect detecting apparatus for a corrugated metal sheath of a cable, including:
the acquisition module is used for acquiring the specification parameters of the corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
the measuring module is used for measuring the total direct current resistance value of the corrugated metal sheath and collecting the ambient temperature under the measuring environment;
the processing module is used for calculating and obtaining the direct current resistance of the corrugated metal sheath in a single corrugated pitch at the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch;
the processing module is also used for acquiring the cylindrical coordinate system of the inner side surface of the corrugated metal sheath
The lower arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
the processing module is further configured to calculate an electrical conductivity of the corrugated metal sheath at the preset reference temperature according to the arc equation, the dc resistance within the single corrugated pitch, the inside minimum radius, the corrugated pitch, and the radial thickness;
and the comparison module is used for comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkle metal sheath.
Another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and the processor implements the method for detecting defects of a wrinkled metal sheath of a cable according to any one of the above items when executing the computer program.
Another embodiment of the present invention provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program runs, an apparatus where the computer-readable storage medium is located is controlled to execute the method for detecting the defect of the wrinkled metal sheath of the cable according to any one of the above items.
Compared with the prior art, the method, the device, the terminal device and the storage medium for detecting the defects of the corrugated metal sheath of the cable disclosed by the embodiment of the invention, the total direct current resistance value of the corrugated metal sheath is measured by obtaining the specification parameters of the corrugated metal sheath of the cable and the arc equation of the inner side surface, collecting the environmental temperature under the measuring environment, calculating the direct current resistance value of the corrugated metal sheath in the single corrugated pitch under the preset reference temperature according to the total direct current resistance value, the environmental temperature and the specification parameters, and according to the inside surface arc equation, the direct current resistance value in the single wrinkle pitch and the specification parameters, the conductivity of the wrinkle metal sheath at the preset reference temperature can be accurately calculated, and further, the conductivity is compared with a preset conductivity qualified threshold value, so that the defect detection result of the wrinkle metal sheath can be accurately obtained.
Drawings
FIG. 1 is a flow chart of a method for detecting defects of a corrugated metal sheath 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 invention;
FIG. 3 is a cross-sectional view of a cable provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a resistivity decomposition model provided by an embodiment of the invention;
FIG. 5 is a schematic diagram of measuring the total DC resistance of a corrugated metal sheath provided by an embodiment of the present invention;
FIG. 6 is a block diagram of a defect detection apparatus for a corrugated metal sheath of a cable according to an embodiment of the present invention;
fig. 7 is a block diagram of a terminal device according to an embodiment of the present invention;
wherein, 10: an electric core; 20: a shielding layer; 30: a buffer layer; 40: a corrugated metal sheath; 41: the outside of the corrugated metal sheath; 42: inside the corrugated metal sheath; 31: the outer side of the buffer layer; 32: the buffer layer is arranged at the inner side.
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 defects of a corrugated metal sheath of a cable according to an embodiment of the present invention.
The method for detecting the defects of the corrugated metal sheath of the cable provided by the embodiment comprises the following steps:
s1, obtaining specification parameters of the corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
s2, measuring the total direct current resistance value of the corrugated metal sheath, and collecting the ambient temperature under the measuring environment;
s3, calculating the direct current resistance value of the corrugated metal sheath in a single corrugated pitch under the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch;
s4, obtaining the corrugated metal sheath in a cylindrical coordinate system
The lower inside surface arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
s5, calculating the conductivity of the corrugated metal sheath at the preset reference temperature according to the inner side surface arc equation, the direct current resistance value in the single corrugated pitch, the inner side minimum radius, the corrugated pitch and the radial thickness;
and S6, comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath.
Specifically, in step S1, referring to fig. 2, the cable according to the embodiment of the present invention includes a battery cell (conductor) 10, a shielding layer 20, a corrugated metal sheath 40, and a buffer layer 30 disposed between the shielding layer 20 and the corrugated metal sheath 40. In specific implementation, the specification parameters of the corrugated metal sheath of the cable can be obtained according to factory test reports or obtained by actually measuring the cable.
It should be noted that, in this embodiment, considering that the surface of the actual corrugated metal sheath is a spatial curved surface, in the radial plane of the cable, the center position O of the corrugated metal sheath is taken as the origin, as shown in fig. 3, which can be established
In the figure, the minimum radius of the inside of the corrugated metal sheath is represented as A when the minimum radius of the inside of the corrugated metal sheath on the OP line is represented as A for any point P on the corrugated metal sheath in the plane polar coordinate (41 represents the outside of the corrugated metal sheath, 42 represents the inside of the corrugated metal sheath, 31 represents the outside of the buffer layer, and 32 represents the inside of the buffer layer)
. Then, at
On the basis of plane coordinates, a three-dimensional coordinate system can be established by taking the axial direction of the cable as the Z direction, as shown in FIG. 4. Because the difference of the radial thickness of each point of the corrugated metal sheath can be ignored, and when the direct current voltage is applied to the two ends of the corrugated metal sheath, the direction of the current flowing through each point in the corrugated metal sheath is the same as the direction of the tangent line of the cambered surface of the metal sheath with the point on the surface of the corrugated metal sheath in the same polar coordinate direction as the point, the accurate radial thickness and the accurate direct current resistance value in the single corrugated pitch, the minimum radius of the inner side, the corrugated pitch and the radial thickness of the inner side surface of the corrugated metal sheath can be realized according to the arc equation of the inner side surface of the corrugated metal sheathThe conductivity of the corrugated metal sheath was calculated accurately.
It should be noted that, in a specific implementation, the preset reference temperature may be set according to an actual requirement, and the conductivity qualified threshold may be set according to an actual conductivity standard requirement at the preset reference temperature, which is not limited herein. Alternatively, when the predetermined reference temperature is 20 ℃, the qualified threshold of the electrical conductivity can be set to 61% IACS (International Annealed Copper Standard) according to the requirements in YS/T454-7（1/ohm·m）。
Specifically, in the step S6, the conductivity is compared with a preset conductivity qualified threshold, if the conductivity is smaller than the conductivity qualified threshold, the defect detection result of the corrugated metal sheath is determined as that the conductivity of the corrugated metal sheath is not qualified, and if the conductivity is not smaller than the conductivity qualified threshold, the defect detection result of the corrugated metal sheath is determined as that the conductivity of the corrugated metal sheath is qualified.
According to the defect detection method of the corrugated metal sheath of the cable, provided by the embodiment of the invention, the total direct current resistance value of the corrugated metal sheath is measured by acquiring the specification parameters of the corrugated metal sheath and the inside surface arc equation, the environment temperature under the measurement environment is acquired, the direct current resistance value of the corrugated metal sheath in a single corrugated pitch under the preset reference temperature is calculated according to the total direct current resistance value, the environment temperature and the specification parameters, the conductivity of the corrugated metal sheath at the preset reference temperature can be accurately calculated according to the inside surface arc equation, the direct current resistance value of the single corrugated pitch and the specification parameters, and further, the conductivity is compared with the preset conductivity qualified threshold value, so that the defect detection result of the corrugated metal sheath can be accurately obtained.
As an alternative embodiment, the calculation formula of the dc resistance value in the single wrinkle pitch is as follows:
wherein the content of the first and second substances,
is a dc resistance value within said single corrugation pitch,
as the value of the total direct current resistance,
is the pitch of the corrugations of the paper,
in order to be the temperature coefficient of resistance,
is the preset reference temperature, and the temperature of the air conditioner is controlled,
is the temperature of the environment, and is,
is the total length.
As an alternative embodiment, the measuring the total dc resistance value of the corrugated metal sheath includes:
s21, connecting a potential electrode and a current electrode at two ends of the corrugated metal sheath;
s22, connecting the two potential electrodes and the two current electrodes with a direct current resistance tester to perform resistance measurement for multiple times so as to obtain multiple resistance measurement values;
and S23, taking the average value of the resistance measurement values as the total direct current resistance value.
Illustratively, before the measurement process is carried out, the sealing caps at two ends of the coiled cable are taken down, the outer sheath of the short section of the cable is removed, the anticorrosive layer and the oxide layer on the surface of the corrugated metal sheath are cleaned and removed,the accuracy of the measurement can be improved. Referring to fig. 5, specifically, a potential electrode is respectively installed at two ends of the corrugated metal sheath, a current electrode is respectively installed outside the two potential electrodes, and then a direct current resistance tester (for example, a wheatstone bridge) is used to connect the potential electrode and the current electrode, so as to measure the direct current resistance of the corrugated metal sheath, and after multiple measurements, an average value is taken, so as to obtain the total resistance value of the corrugated metal sheath, and the distances from the two potential electrodes to the outer sheath of the cable at the metric mark position are respectively recordedd 1 、d 2 Recording the distance between two rice-mark positionsd cable At this time, the process of the present invention,
。
in the embodiment of the invention, the measured value of the resistance value of the corrugated metal sheath is influenced by the fluctuation of the temperature of the cable and the error of a direct current resistance tester. Therefore, the resistance measurement needs to be performed for multiple times, and the average value is finally taken as the total resistance value, so that the influence of temperature fluctuation and resistance tester errors on the resistance measurement value can be reduced.
As one optional embodiment, the obtaining the corrugated metal sheath is performed in a cylindrical coordinate system
The following equation for the camber line, comprising:
based on cylindrical coordinate system
Selecting n interpolated data points from the inside surface of the corrugated metal sheath; wherein the coordinates of the kth interpolated data point is
，k=1，…，n；
And carrying out interpolation calculation according to the n interpolation data points to obtain the inner side surface arc equation.
In this embodiment, after the interpolation method is determined, an interpolation base point may be determined, and the coordinates of the interpolation data point may be obtained by performing multi-point actual measurement on the interpolation base point on the inner side surfaces of different corrugated metal sheaths of the cables of the same type and the same batch provided by the field cable or the supplier, and averaging the measured results
K =1, …, n, n is the number of interpolated data points required by the selected interpolation method. The method can be used for approximating the curve at the inner side of the corrugated metal sheath by polynomial interpolation, triangular interpolation and other methods, so that an approximate curved surface can be obtained
Interval interpolation function expression
。
As an alternative embodiment, said calculating the conductivity of said corrugated metal sheath at said preset reference temperature according to said equation of the inner surface arc, the value of the direct current resistance within said single corrugation pitch, said inner minimum radius, said corrugation pitch and said radial thickness comprises:
solving equations
At real number [0, dlen/2]The immobile points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein the content of the first and second substances,
is the equation for the arc of the inner side surface,
m is the number of the fixed points for the wrinkle pitch,
is the value of the ith stationary point;
if m is 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a first calculation formula of the conductivity;
if m is larger than 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a second calculation formula of the conductivity; the second calculation formula is obtained by performing integral correction on the first calculation formula;
the first calculation formula is:
the second calculation formula is:
wherein, the first and the second end of the pipe are connected with each other,
in order to be said of the electrical conductivity,
is a dc resistance value within said single corrugation pitch,
is the smallest radius of the inner side and,
in order to be said radial thickness,
in order to integrate the correction values,
is that it isRadial coordinate of any point on the radial section of the corrugated metal sheath.
In the present embodiment, the interpolation function is satisfied
The dead point of (2) may cause integral singularity, and when the dead point exists, the calculation robustness may be improved by performing the conductivity calculation using the second calculation formula obtained by performing integral correction on the first calculation formula.
Preferably, if the fixed point is not satisfied
Then will be
And
and merging into the same fixed point.
In specific implementation, the above formula may be solved by using a numerical integration method, wherein numerical integration methods such as a trapezoidal method, a simpson's law, a newton-kowss formula, a longbeck method, a gaussian integration method, a chebyshev integration method, and a monte carlo integration method, and modified forms thereof may be used to obtain the above integral.
Further, the first calculation formula of the conductivity is established in the following manner:
s01, in a cylindrical coordinate system
Next, modeling the corrugated metal sheath within a single corrugation pitch;
s02, performing resistance decomposition on the model to obtain a resistance-decomposed model; the model after resistance decomposition is formed by connecting a plurality of metal wire resistors in parallel in the same direction as current, and each metal wire resistor is formed by connecting a plurality of infinitesimal resistors in series;
s03, decomposed according to the resistanceModel, determining points on the model after the resistance decomposition
Is defined as an arc equation of
；
S04, according to the points
An arc equation and a conductivity calculation formula are established, and any point on the model after the resistance decomposition is established
The resistance value of the micro element resistor is calculated by the formula
(ii) a Wherein the content of the first and second substances,
is the resistance value of the micro element resistor;
s05, establishing a resistance value calculation formula of the metal wire resistor according to the resistance value calculation formula of the infinitesimal resistor and the series resistance calculation formula
(ii) a Wherein the content of the first and second substances,
is the resistance value of the wire resistor;
s06, according to the resistance value calculation formula and the parallel resistance calculation formula of the metal wire resistor, establishing a calculation formula of the direct current resistance value in the single wrinkle pitch as
；
And S07, deducing and obtaining a first calculation formula of the conductivity according to the calculation formula of the direct current resistance value in the single wrinkle pitch.
In this embodiment, to measure the conductivity of the corrugated metal sheath, it is necessary to establish a functional relationship between the conductivity and the direct current resistance of the corrugated metal sheath. As shown in fig. 4, within a single corrugation pitch, the corrugated metal sheath's resistance consists of two symmetrical sections in series. Within a half pitch of corrugations, the corrugated metal sheath can be seen as consisting of a large number of wires in the direction of current flow, and the resistance of the corrugated metal sheath can be decomposed into a parallel connection of a large number of wires in the same direction as the current flow, e.g. a straight line on a radial section of the corrugated metal sheath
At any point on
Past the point
The resistance of the wire in the range of half the pitch of the corrugation is r2. Further, the wire resistance can be broken down in the Z-axis direction into a series of resistances in the form of a plurality of micro-elements, such as metal particles, as shown in FIG. 2 as r1As shown. For one
Point infinitesimal resistance r1The direction of current flowing through the micro-element resistor is the same as the tangential direction of the surface of the corrugated metal sheath, and the current passes through the surface point of the corrugated metal sheath
Is expressed as
The passing point can be known
Is an arc equation of
，d OA Is the minimum radius of the inside of the corrugated metal sheath, and is
From the conductivity calculation formula, the point can be obtained
The resistance value of the micro element resistor is calculated. Then, due to the wire resistance r2Is in a plurality of shapes such as r1The micro-element resistors are connected in series, so that a resistance value calculation formula of the metal wire resistor can be obtained by a series resistance formula. Then, due to the resistance r within a single corrugation pitchAlIs in a plurality of shapes such as r2The resistance of the metal wire is obtained in parallel, so a calculation formula of the direct current resistance value in a single wrinkle pitch can be obtained through a parallel resistance formula, and then the calculation formula of the direct current resistance value in the single wrinkle pitch is converted, so that a first calculation formula of the conductivity can be deduced.
In the embodiment, the corrugated metal sheath is subjected to resistance decomposition, and a first calculation formula of the conductivity is derived according to the relationship among the decomposed micro-element resistance, the metal wire resistance and the total resistance, so that the conductivity of any position in the corrugated metal sheath can be accurately calculated and represented on the premise that the coiled high-voltage cable is not disassembled, and the accuracy of defect evaluation is improved.
Specifically, for r2The formula after integral correction is as follows:
thus, the calculation formula for the dc resistance value within the single wrinkle pitch after integral correction can be derived as:
and then, converting the calculation formula of the direct current resistance value in the single wrinkle pitch after integral correction to obtain a second calculation formula of the conductivity.
As an optional embodiment, before the comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath, the method further includes:
and calculating a sum value between the conductivity and a preset error threshold value, and correcting the conductivity into the sum value.
In particular, the error threshold may be set according to actual conditions, and is not limited herein. Optionally, in this embodiment, the error threshold is 1% IACS.
In the present embodiment, an error threshold is set, and the conductivity is corrected according to the error threshold, so that the error misjudgment caused by the error can be reduced.
The following describes a method for detecting defects of a corrugated metal sheath of a cable according to this embodiment with a specific embodiment:
a1, obtaining the minimum radius of the inner side of the corrugated metal sheath according to factory test reports or actual measurement of the cabled OA And the corrugated pitch of the corrugated metal sheathd len The radial thickness t of the corrugated metal sheath is shown in table 1.
TABLE 1 Specification parameters
A2, measuring the total direct current resistance value of the corrugated metal sheath, and collecting the ambient temperature under the measuring environment, wherein the method comprises the following steps:
a21, respectively installing a potential electrode at two selected positions at two ends of a corrugated metal sheath, and respectively installing a current electrode at the outer side of each of the two potential electrodes;
a22, recording the distance between two potential electrodes and the outer sheath of cabled 1 、d 2 Recording the distance between two rice-mark positionsd cable As shown in Table 2, and calculating the total lengthd total ；
TABLE 2 Length parameters
A23, connecting the potential electrode and the current electrode with a direct current resistance tester (such as Wheatstone bridge), measuring the direct current resistance of the corrugated metal sheath, and averaging the measured direct current resistance to obtain the total resistance of the corrugated metal sheathR Al As shown in table 3;
a24, measuring the ambient temperature near the coiled cable by using a temperature measuring deviceTThe results are shown in Table 3.
A3, according to the temperature coefficient of resistance of the material corresponding to the corrugated metal sheath at a preset reference temperature of 20 DEG CaAmbient temperatureTCorrugated metal sheath total resistanceR Al Total length ofd total And pitch of the wrinklesd len Calculating the direct current resistance of the metal sleeve within a single wrinkle pitch at 20 DEG C
。
TABLE 3 values of the parameters
A4, obtaining the corrugated metal sheath in a cylindrical coordinate system
The following equation for the camber line, comprising:
a41, selecting the interpolation mode as a cubic polynomial interpolation mode, determining the interpolation base point
K =1, …, n, n is the number of interpolation data points required by the interpolation method;
a42, interpolating base points at different wrinkles on the same cable or the same batch of cables provided by the supplier or the cable concerned, for all interpolation base pointsr k Measuring the inside of wrinkles at multiple points at a locationZDirectional coordinates, the coordinates of the interpolated data points being obtained after averaging
. The measured interpolated data point coordinates are shown in table 4;
TABLE 4 interpolation Point coordinates
A43, performing interpolation calculation according to the n interpolation data points to obtain an inner side surface arc equation of
The values of the equation parameters are shown in table 5.
TABLE 5 camber line equation parameters for the inside surface
A5, solving the equation
At real number [0, dlen/2]The fixed points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein, if the fixed point is not satisfied
Then will be
And
and merging into the same fixed point. Equation of
The calculation results of the solution of (a) are shown in table 6.
TABLE 6 results of calculation
Since m is greater than 0, the resistance of the metal jacket within a single corrugation pitch at 20 DEG Cr Al And calculating the conductivity of the corrugated metal sheath at 20 ℃ by using a second calculation formula of the conductivitys=3.7056×107(1/ohm. m). Wherein the numerical integration calculation is carried out by applying a Longbeth method.
A6, calculating the conductivitysWith a predetermined error thresholdeThe sum of =1% IACS is 3.7056 × 107+1% IACS and conductivity corrected tos=3.7056×107+1% IACS。
A7, electrical conductivitys=3.7056×107The +1% IACS is compared with a preset qualified threshold value of the conductivity of 61% IACS, becausesAnd the defect detection result of the wrinkled metal sheath is that the conductivity of the wrinkled metal sheath is qualified, wherein the =64.89% IACS is more than 61% IACS.
Referring to fig. 6, fig. 6 is a block diagram of a defect detecting apparatus for a corrugated metal sheath of a cable according to an embodiment of the present invention.
The defect detection device for the corrugated metal sheath of the cable provided by the embodiment comprises:
an obtaining module 21, configured to obtain specification parameters of a corrugated metal sheath of a cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
the measuring module 22 is used for measuring the total direct current resistance value of the corrugated metal sheath and collecting the environmental temperature under the measuring environment;
the processing module 23 is configured to calculate, according to the total dc resistance value, the ambient temperature, the preset reference temperature, the resistance temperature coefficient, the total length, and the wrinkle pitch, a dc resistance of the wrinkle metal sheath within a single wrinkle pitch at the preset reference temperature;
the processing module 23 is further configured to obtain a cylindrical coordinate system of the inner side surface of the corrugated metal sheath
The lower arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
said processing module 23, further configured to calculate an electrical conductivity of said corrugated metal sheath at said preset reference temperature according to said arc equation, a dc resistance within said single corrugation pitch, said inside minimum radius, said corrugation pitch, and said radial thickness;
and the comparison module 24 is configured to compare the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath.
The defect detection device for the corrugated metal sheath of the cable disclosed by the embodiment of the invention measures the total direct current resistance value of the corrugated metal sheath by acquiring the specification parameters and the inside surface arc equation of the corrugated metal sheath, acquires the environment temperature under the measurement environment, calculates the direct current resistance value of the corrugated metal sheath in a single corrugated pitch under the preset reference temperature according to the total direct current resistance value, the environment temperature and the specification parameters, can accurately calculate the conductivity of the corrugated metal sheath at the preset reference temperature according to the inside surface arc equation, the direct current resistance value in the single corrugated pitch and the specification parameters, and further can accurately obtain the defect detection result of the corrugated metal sheath by comparing the conductivity with the preset conductivity qualified threshold.
As an improvement of the above solution, the calculation formula of the dc resistance value in the single wrinkle pitch is:
wherein the content of the first and second substances,
is a dc resistance value within said single corrugation pitch,
as the value of the total direct current resistance,
for the pitch of the corrugations to be described,
in order to be the temperature coefficient of resistance,
is the preset reference temperature, and the temperature of the air conditioner is controlled,
is the temperature of the environment, and is,
is the total length.
As an improvement of the above solution, the measuring of the total dc resistance value of the corrugated metal sheath includes:
both ends of the corrugated metal sheath are connected with a potential electrode and a current electrode;
connecting the two potential electrodes and the two current electrodes with a direct current resistance tester to perform resistance measurement for multiple times so as to obtain multiple resistance measurement values;
and taking the average value of the resistance measurement values as the total direct current resistance value.
As an improvement of the scheme, the corrugated metal sheath is obtained in a cylindrical coordinate system
The following equation for the camber line, comprising:
based on cylindrical coordinate system
Selecting n interpolated data points from the inside surface of the corrugated metal sheath; wherein the coordinates of the kth interpolated data point is
，k=1，…，n；
And carrying out interpolation calculation according to the n interpolation data points to obtain the inner side surface arc equation.
As an improvement of the above, said calculating the conductivity of said corrugated metal sheath at said preset reference temperature according to said equation of the inside surface arc, the value of the direct current resistance within said single corrugation pitch, said inside minimum radius, said corrugation pitch and said radial thickness comprises:
solving equation
At real number [0, dlen/2]The immobile points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein the content of the first and second substances,
is the equation for the arc of the inner side surface,
m is the number of the fixed points for the wrinkle pitch,
is the value of the ith stationary point;
if m is 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a first calculation formula of the conductivity;
if m is more than 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a second calculation formula of the conductivity; the second calculation formula is obtained by performing integral correction on the first calculation formula;
the first calculation formula is:
the second calculation formula is:
wherein, the first and the second end of the pipe are connected with each other,
in order to be said of the electrical conductivity,
is a dc resistance value within said single corrugation pitch,
is the smallest radius of the inner side and,
is the thickness in the radial direction of the sheet,
in order to integrate the correction values,
is the radius coordinate of any point on the radial section of the corrugated metal sheath.
As an improvement of the above scheme, the first calculation formula of the conductivity is established in the following manner:
in cylindrical coordinate system
Next, modeling the corrugated metal sheath within a single corrugation pitch;
carrying out resistance decomposition on the model to obtain a resistance decomposed model; the model after resistance decomposition is formed by connecting a plurality of metal wire resistors in parallel in the same direction as current, and each metal wire resistor is formed by connecting a plurality of infinitesimal resistors in series;
determining points on the resistance-decomposed model according to the resistance-decomposed model
The equation of the arc at is
；
According to the point
An arc equation and a conductivity calculation formula are established, and any point on the model after the resistance decomposition is established
The resistance value of the micro element resistor is calculated by the formula
(ii) a Wherein the content of the first and second substances,
is said microThe resistance value of the element resistor;
according to the resistance value calculation formula of the infinitesimal resistor and the series resistance calculation formula, the resistance value calculation formula of the metal wire resistor is established as
(ii) a Wherein the content of the first and second substances,
is the resistance value of the wire resistor;
according to the resistance value calculation formula and the parallel resistance calculation formula of the metal wire resistor, the calculation formula for establishing the direct current resistance value in the single wrinkle pitch is
；
And deducing to obtain a first calculation formula of the conductivity according to a calculation formula of the direct current resistance value in the single wrinkle pitch.
As an improvement of the above, the apparatus further comprises:
and the correction module is used for calculating the sum value between the conductivity and a preset error threshold value and correcting the conductivity into the sum value.
Fig. 7 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 processor 310 implements the method for detecting the defect of the wrinkled metal sheath of the cable according to any of the above embodiments.
The processor 310, when executing the computer program, implements the steps in the above-described embodiments of the method for detecting defects of a corrugated metal sheath of a cable, such as all the steps of the method for detecting defects of a corrugated metal sheath 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 acquisition module, a measurement module, a processing module and a comparison module, and each module has the following specific functions: the acquisition module is used for acquiring the specification parameters of the corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature; the measuring module is used for measuring the total direct current resistance value of the corrugated metal sheath and collecting the ambient temperature under the measuring environment; the processing module is used for calculating and obtaining the direct current resistance of the corrugated metal sheath in a single corrugated pitch at the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch; the processing module is also used for acquiring the cylindrical coordinate system of the inner side surface of the corrugated metal sheath
The lower arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable; the processing module is further configured to calculate the electrical conductivity of the corrugated metal sheath at the preset reference temperature according to the arc equation, the dc resistance within the single corrugation pitch, the inside minimum radius, the corrugation pitch, and the radial thickness; a comparison module for comparing the conductivity with a preset conductivity qualified threshold value to obtain the corrugated metal sheathThe defect detection result of (1).
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, discrete hardware components, etc. 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 for at least one function, and the like; the storage data area may store data 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 (9)
1. A defect detection method for a corrugated metal sheath of a cable is characterized by comprising the following steps:
acquiring specification parameters of a corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
measuring the total direct current resistance value of the corrugated metal sheath, and collecting the environmental temperature under the measuring environment;
calculating to obtain a direct current resistance value of the corrugated metal sheath in a single corrugated pitch at the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch;
obtaining a cylindrical coordinate system of the corrugated metal sheath
The lower inside surface arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
calculating the conductivity of the corrugated metal sheath at the preset reference temperature according to the equation of the inner side surface arc, the direct current resistance value in the single corrugated pitch, the inner minimum radius, the corrugated pitch and the radial thickness;
comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkled metal sheath;
wherein said calculating the conductivity of said corrugated metal sheath at said preset reference temperature from said inside surface arc equation, a DC resistance value within said single corrugation pitch, said inside minimum radius, said corrugation pitch, and said radial thickness comprises:
solving equation
At real number [0, dlen/2]The immobile points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein the content of the first and second substances,
is the equation for the arc of the inner side surface,
m is the number of the fixed points for the wrinkle pitch,
is the value of the ith stationary point;
if m is 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a first calculation formula of the conductivity;
if m is larger than 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a second calculation formula of the conductivity; the second calculation formula is obtained by performing integral correction on the first calculation formula;
the first calculation formula is:
the second calculation formula is:
wherein the content of the first and second substances,
in order to be said of the electrical conductivity,
is a dc resistance value within said single corrugation pitch,
is the smallest radius of the inner side and,
in order to be said radial thickness,
in order to integrate the correction values,
is the radius coordinate of any point on the radial section of the corrugated metal sheath.
2. The method for detecting defects in corrugated metal sheaths of cables according to claim 1, characterized in that the dc resistance value in a single corrugation pitch is calculated by the formula:
wherein the content of the first and second substances,
is a dc resistance value within said single corrugation pitch,
as the value of the total direct current resistance,
for the pitch of the corrugations to be described,
in order to be the temperature coefficient of resistance,
is the preset reference temperature, and the temperature of the air conditioner is controlled,
is the temperature of the environment, and is,
is the total length.
3. The method for detecting defects in a corrugated metal sheath of a cable of claim 1, wherein said measuring a total dc resistance value of said corrugated metal sheath comprises:
both ends of the corrugated metal sheath are connected with a potential electrode and a current electrode;
connecting the two potential electrodes and the two current electrodes with a direct current resistance tester to perform resistance measurement for multiple times so as to obtain multiple resistance measurement values;
and taking the average value of the resistance measurement values as the total direct current resistance value.
4. The method of claim 1, wherein said obtaining of said corrugated metal sheath is in a cylindrical coordinate system
The following equation for the camber line, comprising:
based on cylindrical coordinate system
From said corrugated metal sheathSelecting n interpolation data points on the inner side surface; wherein the coordinates of the kth interpolated data point is
，k=1，…，n；
And carrying out interpolation calculation according to the n interpolation data points to obtain the inner side surface arc equation.
5. The method for detecting defects in corrugated metal sheaths of cables according to claim 1, characterized in that said first calculation formula is established by:
in cylindrical coordinate system
Next, modeling the corrugated metal sheath within a single corrugation pitch;
carrying out resistance decomposition on the model to obtain a resistance decomposed model; the model after resistance decomposition is formed by connecting a plurality of metal wire resistors in parallel in the same direction as current, and each metal wire resistor is formed by connecting a plurality of infinitesimal resistors in series;
determining points on the resistance-decomposed model according to the resistance-decomposed model
Is defined as an arc equation of
；
According to the point
An arc equation and a conductivity calculation formula are established, and any point on the model after the resistance decomposition is established
The resistance value of the micro element resistor is calculated by the formula
(ii) a Wherein the content of the first and second substances,
is the resistance value of the micro element resistor;
according to the resistance value calculation formula of the infinitesimal resistor and the series resistance calculation formula, the resistance value calculation formula of the metal wire resistor is established as
(ii) a Wherein the content of the first and second substances,
is the resistance value of the wire resistor;
according to the resistance value calculation formula and the parallel resistance calculation formula of the metal wire resistor, the calculation formula for establishing the direct current resistance value in the single wrinkle pitch is
；
And deducing to obtain a first calculation formula of the conductivity according to a calculation formula of the direct current resistance value in the single wrinkle pitch.
6. The method for detecting defects of a corrugated metal sheath of a cable according to claim 1, wherein before comparing the conductivity with a preset conductivity qualified threshold to obtain a defect detection result of the corrugated metal sheath, the method further comprises:
calculating a sum of the conductivity and a preset error threshold, and correcting the conductivity to be the sum.
7. A defect detection device for corrugated metal sheaths of cables, comprising:
the acquisition module is used for acquiring the specification parameters of the corrugated metal sheath of the cable; wherein the specification parameters include a total length, an inside minimum radius, a corrugation pitch, a radial thickness, and a temperature coefficient of resistance at a preset reference temperature;
the measuring module is used for measuring the total direct current resistance value of the corrugated metal sheath and collecting the ambient temperature under the measuring environment;
the processing module is used for calculating and obtaining the direct current resistance of the corrugated metal sheath in a single corrugated pitch under the preset reference temperature according to the total direct current resistance value, the environment temperature, the preset reference temperature, the resistance temperature coefficient, the total length and the corrugated pitch;
the processing module is also used for acquiring the cylindrical coordinate system of the inner side surface of the corrugated metal sheath
The lower arc equation; the polar point of the cylindrical coordinate system is the center of the corrugated metal sheath, the polar axis is any radial direction of the center of the corrugated metal sheath, and the Z-axis direction is the axial direction of the cable;
the processing module is further configured to calculate an electrical conductivity of the corrugated metal sheath at the preset reference temperature according to the arc equation, the dc resistance within the single corrugated pitch, the inside minimum radius, the corrugated pitch, and the radial thickness;
the comparison module is used for comparing the conductivity with a preset conductivity qualified threshold value to obtain a defect detection result of the wrinkle metal sheath;
wherein said calculating the conductivity of said corrugated metal sheath at said preset reference temperature from said inside surface arc equation, said DC resistance value within said single corrugation pitch, said inside minimum radius, said corrugation pitch, and said radial thickness comprises:
solving equations
At real number [0, dlen/2]The immobile points in the interval are arranged according to the ascending order of the numerical value and are recorded as
(ii) a Wherein the content of the first and second substances,
is the equation for the arc of the inner side surface,
m is the number of the fixed points for the wrinkle pitch,
is the value of the ith stationary point;
if m is 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a first calculation formula of the conductivity;
if m is larger than 0, calculating the conductivity of the corrugated metal sheath at the preset reference temperature by adopting a second calculation formula of the conductivity; the second calculation formula is obtained by performing integral correction on the first calculation formula;
the first calculation formula is:
the second calculation formula is:
wherein the content of the first and second substances,
in order to be said of the electrical conductivity,
is a dc resistance value within said single corrugation pitch,
is the smallest radius of the inner side and,
in order to be said radial thickness,
in order to integrate the correction values,
is the radius coordinate of any point on the radial section of the corrugated metal sheath.
8. 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 the method of defect detection of a wrinkled metal sheath of a cable according to any one of claims 1 to 6 when executing the computer program.
9. 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 wrinkled metal jacket of a cable according to any one of claims 1 to 6.
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| CN112782526A (en) * | 2020-12-28 | 2021-05-11 | 国网天津市电力公司电力科学研究院 | Method for screening ablation hidden danger cable sections of buffer layer based on inner surface area of corrugated sheath |
| CN113588724A (en) * | 2021-09-29 | 2021-11-02 | 国网天津市电力公司电力科学研究院 | Defect detection method, device and equipment for cable buffer layer |
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