CN112782526B - Method for screening ablation hidden danger cable sections of buffer layer based on inner surface area of corrugated sheath - Google Patents
Method for screening ablation hidden danger cable sections of buffer layer based on inner surface area of corrugated sheath Download PDFInfo
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Abstract
The invention relates to a method for screening cable sections with potential ablation hazards of buffer layers based on the inner surface area of a corrugated sheath, which is technically characterized by comprising the following steps of: according to the inner side surface area of the corrugated sheath in the single corrugated pitch, the inner side surface area of the corrugated sheath of the high-voltage power cable is approximately calculated; according to the surface area of the inner side of the wrinkle sheath of the high-voltage power cable, a screening threshold value of the potential ablation hazard cable section of the buffer layer is obtained by calculating the contact ratio of the fault cable section, and the potential ablation hazard cable section of the buffer layer is screened through the screening threshold value of the potential ablation hazard cable section of the buffer layer. The cable section screening device is reasonable in design, achieves the cable section screening function of ablation hidden danger of the high-voltage cable buffer layer according to the inner side surface area of the high-voltage power cable corrugated sheath, can be used for performance evaluation under the condition that the high-voltage power cable corrugated sheath is matched with the buffer layer in size, gives a list of ablation hidden danger cable sections of the buffer layer of cables in stock, and provides reference for operation and maintenance of the high-voltage power cable.
Description
Technical Field
The invention belongs to the technical field of high voltage and insulation, and particularly relates to a method for screening ablation hidden danger cable sections of a buffer layer based on the inner surface area of a corrugated sheath.
Background
In recent years, the number of faults caused by ablation of a buffer layer of a high-voltage power cable is gradually increased, and the ablation hidden danger of the buffer layer becomes one of important hidden dangers threatening the safety of a power grid. At present, a method for screening cable sections with hidden buffer layer ablation risks of high-voltage power cables is still very primary, and a method for summarizing a list of cable suppliers with faults of the type and listing other cables which are not in fault in the list as hidden cables is generally adopted. This approach usually results in a number of high voltage power cables from several suppliers requiring technical modification or replacement, but other supplier products are completely non-hazardous. The screening method does not take technical information of specific cables into account, so that the hidden dangers of cable products of screened supplier lists are easily overestimated on one hand, and the risks of cable products of other suppliers are easily ignored on the other hand. Therefore, a method for screening ablation risks by combining cable information needs to be developed.
In general, the ablation of a water-blocking buffer layer is generally accompanied by the following two phenomena: (1) the water-blocking buffer layer is affected with damp; (2) 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 and the construction stage. The latter is still difficult due to the short time to find a replacement for the combination corrugated aluminum sheath-water-blocking buffer-insulation shielding material. Therefore, on the premise that materials cannot be changed, under the condition that the buffer tape is tightly wrapped on the insulation shielding layer, the contact area between the corrugated sheath and the buffer layer becomes key information for determining the electrical connection between the corrugated sheath and the insulation shielding layer, and a method for screening the ablation hidden danger of the buffer layer can be developed according to the key information.
Neglecting the influence caused by the bending of the cable, the method for intuitively estimating the contact area (hereinafter referred to as the contact area) between the corrugated sheath and the buffer layer is to take the cylindrical area formed by the circle which is coated on the outer side of the buffer layer on the cable and is formed along the axial direction of the cable or the cylindrical area formed by the circle at the position of the wave trough on the inner side of the corrugated sheath and is formed along the axial direction of the cable as the estimated value of the contact area. The premise of the method is that the corrugated sheath is completely and tightly contacted with the buffer layer, and the method is not in accordance with the actual engineering and brings great errors when the electrical connection condition is analyzed. Therefore, the contact area, a key technical parameter, still lacks an effective calculation means, and the solution of the problem mainly has the following challenges:
(1) Power cable suppliers commonly use metal corrugated production lines for corrugated sheath production. The technical parameters of the sheath wrinkles are controlled through two production parameters of the wrinkle pitch and the wrinkle depth. This approach does not directly determine the shape parameters of smooth wrinkles typical of the radius of curvature. In addition, the contact with the buffer layer in the axial direction of the cable is generally discontinuous due to the presence of peaks and valleys in the corrugated jacket. These problems present difficulties in mathematical modeling and calculation of the contact area of the corrugated sheath with the cushioning layer.
(2) Currently, the corrugated sheaths and cushioning layers still lack the corresponding standard constraints in terms of dimensional fit. Under the condition of comprehensively considering the requirements of the mechanical strength, the axial water resistance and other properties of the cable, different power cable suppliers adopt different technical schemes on the problem of 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. Thus, under the action of gravity, the inside of the corrugated sheath above the cable of some suppliers does not come into effective contact with the buffer layer, as shown in fig. 1; the inside of the corrugated sheath over part of the supplier's cable is in operative contact with the buffer layer as shown in fig. 2. Clearly, a calculation method that can take both cases into account is needed.
(3) Early cables lack information such as factory test reports, so that basic data of the cables are incomplete, and sufficient information is difficult to provide for calculating the contact area. Therefore, the calculation method of the contact area between the corrugated sheath and the buffer layer needs to have the capability of accessing measured data so as to deal with the situation of insufficient cable information.
How to calculate the surface area of the inner side of a corrugated sheath of a high-voltage power cable and quickly screen the ablation hidden danger cable section of a buffer layer of the high-voltage power cable is a problem which needs to be solved urgently at present.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a reasonable-design, rapid and accurate screening method for cable sections with ablation hidden troubles of buffer layers based on the inner surface area of a corrugated sheath.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a method for screening a cable section with ablation hidden danger of a buffer layer based on the inner surface area of a corrugated sheath comprises the following steps:
step 1, approximately calculating the inner side surface area of a corrugated sheath of a high-voltage power cable according to the inner side surface area of the corrugated sheath in a single corrugated pitch;
and 2, according to the surface area of the inner side of the wrinkle sheath of the high-voltage power cable, calculating the contact ratio of the fault cable section to obtain a screening threshold of the ablation hidden danger cable section of the buffer layer, and screening the ablation hidden danger cable section of the buffer layer through the screening threshold of the ablation hidden danger cable section of the buffer layer.
Moreover, the specific implementation method of the step 1 is as follows:
step 1.1, according to a cable factory test report or an actual measurement result, arranging to obtain the following data: length d of cable segment cable Nominal value, inside radius d of corrugated sheath OA Nominal value, wrinkle pitch d len Nominal value, wrinkle depth d dep A nominal value;
step 1.2, determining the selected interpolation method to obtain an interpolation base point rho k K =1,.. R, r is the number of interpolation data points required by the interpolation method;
step 1.3, interpolation of base points ρ, at different corrugations, on the same type of cable or batch of cables of the same type provided by the supplier, for all k =1 k Measuring the Z-direction coordinate of the inner side of the wrinkle at multiple points at the position, and averaging to obtain the coordinate (rho) of the interpolated data point k ，0，z k )；
Step 1.4, interpolation data point (rho) k ，0，z k ) K =1,.. And r, and performing interpolation calculation to obtain an interpolation function expression f (rho);
step 1.5, to the surface area S of the inside of the corrugated sheath of the formula total-pit Simplifying the integration, then calculating by using a numerical integration method to obtain a result, and calculating the inner surface area of the wrinkle sheath:
moreover, the method for obtaining the screening threshold of the cable segment with the ablation hidden danger of the buffer layer by calculating the contact ratio of the fault cable segment in the step 2 comprises the following steps:
(1) For a fault cable segment set { l under a specified voltage level i } i＝1，...，n Arranging factory cable data information, arranging data required by the calculation method of the contact area and the surface area of the inner side of the corrugated sheath, and entering the step (2) if the data is insufficient; otherwise, entering the step (3);
(2) For all fault cable sections with insufficient data, actually testing the cable sections intercepted during fault processing, and supplementing the data required by the calculation method;
(3) For all i =1.. Times.n, the total contact area is calculated, resulting in S total (l i )；
(4) Calculating the inside surface area of the wrinkled sheath for all i =1 total-pit (l i )；
(5) Calculation of contact ratio according to the following formula gives w (l) i )；
(6) The summary calculation obtains a fault cable section contact ratio set w (l) i )} i＝1，...，n And calculating a screening threshold t of the cable section with the potential ablation hazard of the buffer layer under the voltage level according to the following formula:
moreover, the method for screening the cable section with the ablation hidden danger of the buffer layer in the step 2 comprises the following steps:
(1) To and { l i } i＝1，...，n Cable segment set { q ] to be screened at same voltage level ｊ } j＝1，...，m Arranging factory cable data information, keeping the same calculation method of the contact area and the inner side surface area of the wrinkle sheath as the screening threshold calculation process, collecting data required by the calculation method of the contact area and the inner side surface area of the wrinkle sheath, and entering the step (2) if the data are insufficient; otherwise, entering the step (3);
(2) For all the cable segments to be screened with insufficient data, actually testing the same-model same-batch cable segments, and supplementing the data required by the calculation method;
(3) Calculate the total contact area for all j =1 total (q j )；
(4) Calculating the inside surface area of the wrinkled sheath for all j =1 total-pit (q j )；
(5) The contact ratio calculation was performed according to the following formula to obtain w (q) j )；
(6) The contact ratio set { w (q) of the cable segments to be screened is obtained through summarizing and calculating ｊ )｝ j＝1，...，m For all j =1.. Times, m, the following determinations are made: if w (q) j ) When t is less than or equal to t, q is added j Adding the potential hazards into a hidden danger list, otherwise, adding q into the hidden danger list j Excluded from the hidden danger list;
(7) And (5) sorting and outputting the hidden danger list, and screening the cable section with the ablation hidden danger of the cable buffer layer.
The invention has the advantages and positive effects that:
the method is reasonable in design, the surface area of the inner side of the corrugated sheath of the high-voltage power cable is approximately calculated through the surface area of the inner side of the corrugated sheath in a single corrugated pitch, the screening threshold value of the ablation hidden danger cable section of the buffer layer of the high-voltage power cable is obtained through calculating the contact ratio of the fault cable section, the ablation hidden danger cable section of the buffer layer of the high-voltage power cable is screened according to the screening threshold value, the method can be used for evaluating the performance of the high-voltage power cable under the condition that the corrugated sheath and the buffer layer are matched in size, the list of the ablation hidden danger cable section of the buffer layer of the cable stock is given, and reference is provided for operation and maintenance of the high-voltage power cable.
Drawings
FIG. 1 is a schematic view of a condition of no contact between the corrugated sheath and the buffer layer over the cable;
FIG. 2 is a schematic view of the presence of contact between the corrugated jacket and the buffer layer over the cable;
FIG. 3 shows the contact surface between the corrugated sheath and the buffer layer at θ = θ P A plan sectional view.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
A method for screening a cable section with ablation hidden danger of a buffer layer based on the inner surface area of a corrugated sheath comprises the following steps:
step 1, approximately calculating the surface area of the inner side of the corrugated sheath of the high-voltage power cable.
The method for approximately calculating the surface area of the inner side of the corrugated sheath of the high-voltage power cable is carried out based on the following principle:
1. calculated decomposition of the inside surface area of a corrugated sheath
Due to the peak-valley position of the corrugated sheath, the following basic assumptions in accordance with engineering practice need to be made for calculating the inside surface area of the corrugated sheath:
assume that the inside surface area of the corrugated sheath within each corrugation pitch is approximately the same;
assume that the effect of the angle of inclination of the wrinkles on the inside surface area of the wrinkled jacket is negligible.
The surface area of the inner side of the corrugated sheath can be decomposed into the sum of the surface areas of the inner sides of the corrugated sheaths in each corrugated pitch. Since a corrugation pitch is small compared to the total length of the cable segment, the surface area at the ends of the cable less than one corrugation pitch can be approximated with a corresponding ratio. This gives:
in the formula, S total-pit Is the inside surface area of the corrugated sheath; s. the pit A corrugated sheath inside surface area within a single corrugated pitch; d len Is the nominal value of the corrugation pitch. So to obtain the cable overall corrugated jacket inside surface area, the corrugated jacket inside surface area within a single corrugated pitch needs to be calculated.
2. Approximate calculation of inside surface area of corrugated sheath within single corrugation pitch
Considering that the inner side surface of the actual corrugated sheath is a spatial curved surface, and taking the circle center position O of the corrugated sheath as an origin in a radial plane of the cable, a rho-theta plane polar coordinate can be established as shown in fig. 1. O 'is the centre of a circle of the cable core, and the critical points of the contact of the buffer layer and the corrugated sheath are marked as A and A'. As shown in fig. 3, on the basis of the rho-theta plane coordinate, a rho-theta-Z three-dimensional coordinate system can be established by taking the axial direction of the cable as the Z direction, 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, if the contact surface function is z = f (ρ, θ), the corresponding contact area can be calculated by the following equation:
wherein Ω ρ θ is a projection of the curved inner surface of the corrugated sheath on the z =0 plane.
As described in the background section, the analytical expression of f (ρ, θ) is difficult to obtain. An approximation of the inside surface area of the corrugated sheath is obtained by surface integral calculation of a continuous micro-approximable function of the z = f (ρ, θ) surface. The patent proposes a method for approximate calculation of the inside surface area of a corrugated sheath in a single corrugation pitch. Since the projection of the inner curved surface of the corrugated sheath on the z =0 plane is symmetrical with the line in the θ =0 direction, and the inner curved surface of the corrugated sheath within a single corrugated pitch is symmetrical with the z =0 plane, S is calculated pit The value of (a) is only required to finish the calculation of the curved surface integral multiplied by 4 times in the interval of pi is more than or equal to theta is more than or equal to 0,Z is more than or equal to 0.
As shown in FIG. 3, for an arbitrary point P ∈ Ω ρ θ, let its coordinate be (ρ ∈ Ω ρ θ) P ，θ P ,0). On a plane z =0, taking a ray from an origin O to a point P, and marking an intersection point of the ray and the outer side of the insulation shield as B; the intersection point of the buffer layer and the outer side is marked as C; the intersection point of the inner side of the corrugated sheath is marked as D; the critical positions of the contact between the wrinkle sheath and the buffer layer in the single wrinkle pitch are E, F two points respectively, and the starting point and the ending point of the single wrinkle pitch are G, H two points. By approximating the wrinkle curve GDH in the cable axial direction, a wrinkle sheath and a cushion can be obtainedAn approximate curved surface (hereinafter referred to as an approximate curved surface) of the layer-contacting curved surface.
In terms of the integrand, polynomial interpolation, triangular interpolation, etc. may be applied to approximate the curve GD inside the wrinkled jacket. After the interpolation method is determined, an interpolation base point can be determined, the field cable or the supplier can be provided with the same type and batch of cables, the interpolation base point in different wrinkles can be subjected to multi-point actual measurement, and the coordinates (rho) of the interpolation data point can be obtained after the averaging k ，0，z k ) k =1, r, r is the number of interpolation data points required by the selected interpolation method. Thereby obtaining an approximate curved surface
The interpolation function within the interval is expressed as f (ρ).
The approximate expression for the inside surface area of the corrugated sheath within a single corrugation pitch is available as:
wherein d is OA Is the nominal value of the inside radius of the corrugated sheath; d dep Is the nominal value of wrinkle depth.
After determining a particular interpolation function, the above integration attempt may be simplified. It can be found that the integral before and after the simplification can not guarantee to have an analytic solution, and a numerical integration method can be applied to solve. Numerical integration methods such as a trapezoidal method, a Simpson's law, a Newton-Ke Tesi formula, a Long Beige method, a Gaussian integration method, a Chebyshev integration method, a Monte Carlo integration method and the like and improved forms thereof can be used for solving the integration, so that an approximate value of the inner side surface area of the wrinkle sheath in a single wrinkle pitch is obtained.
Based on the principle, the method for calculating the surface area of the inner side of the corrugated sheath of the high-voltage power cable comprises the following steps:
step 1.1, according to a cable factory test report or an actual measurement result, arranging to obtain the following data: length d of cable segment cable Nominal value, inside radius d of corrugated sheath oA Nominal value, wrinkle pitch d len Nominal value, wrinkle depth d dep A nominal value.
Step 1.2, determining the selected interpolation method to obtain an interpolation base point rho k K =1.. And r, r is the number of interpolation data points required by the interpolation method.
Step 1.3, interpolating base points ρ, r, in different wrinkles, on the same type of cable or batch of cables of the same type provided by the supplier or cable of interest, for all k =1 k Measuring the Z-direction coordinate of the inner side of the wrinkle at multiple points at the position, and averaging to obtain the coordinate (rho) of the interpolated data point k ，0，z k )。
Step 1.4, interpolation data point (rho) k ，0，z k ) And k =1.. And r, and performing interpolation calculation to obtain an interpolation function expression f (rho).
Step 1.5, to the surface area S of the inside of the corrugated sheath of the formula total-pit And simplifying the integral, then calculating by using a numerical integration method to obtain a result, and finishing the calculation of the inner side surface area of the wrinkle sheath.
The method can be applied to obtain the approximate surface area value of the buffer layer of the newly-delivered cable according to the dimension nominal value information on the cable delivery test report. The method can be used for carrying out approximate calculation on the surface area of the buffer layer of the commissioned cable by using the measured data of the cable.
And 2, screening cable sections with ablation hidden troubles of the buffer layer of the high-voltage power cable according to the surface area of the inner side of the corrugated sheath of the high-voltage power cable.
The contact area of the corrugated sheath and the buffer layer on the whole cable depends on the size information of the length of the actual cable segment, the thickness of insulation and the like, and the size design of the high-voltage cable of each cable supplier is not consistent. Since the contact area mainly reflects the contact condition of the buffered layer between the cable insulation shield and the corrugated sheath, in order to realize the comparison of cables with different sizes, the invention provides a method for performing comparison by using the contact ratio.
On the basis that the contact area can be calculated or estimated, the contact ratio is calculated using the following equation:
wherein w is a contact ratio between the buffer layer and the wrinkled jacket; s total The contact area of the corrugated sheath and the buffer layer; s total-pit Is the inside surface area of the corrugated sheath.
After the contact area of the wrinkle sheath and the buffer layer on the whole cable and the inner surface area of the wrinkle sheath are determined, a hidden danger cable section screening threshold value can be obtained according to the contact ratio information of the fault cable, and the hidden danger cable section screening threshold value is compared with the contact ratio information of the cable to be screened, so that the conclusion whether the cable to be screened contains the ablation hidden danger of the buffer layer is obtained.
Based on the above description, the specific implementation method of this step includes the following steps:
step 2.1, calculating a screening threshold value of the cable section with the ablation hidden danger of the buffer layer, wherein the specific method comprises the following steps:
(1) For a fault cable segment set { l under a specified voltage level i } i＝1，...，n And sorting cable data information such as factory reports and the like for all i =1. And respectively determining a contact area and a calculation method of the inner side surface area of the corrugated sheath. Finishing data required by the calculation method of the contact area and the surface area of the inner side of the wrinkle sheath, and entering the step (2) if the data are insufficient; otherwise, entering the step (3).
(2) And for all fault cable sections with insufficient data, actually testing the cable sections intercepted during fault processing, and supplementing the data required by the calculation method.
(3) For all i =1.. Times.n, the total contact area is calculated, resulting in S total (l i )。
(4) Calculating the inside surface area of the wrinkled sheath for all i =1 total-pit (l i )。
(5) Calculating the contact ratio according to the following formulaTo w (l) i )。
(6) The summary calculation obtains a fault cable section contact ratio set w (l) i )} i＝1，...，n And calculating to obtain the screening threshold t of the cable section with the ablation hidden danger of the buffer layer under the voltage level according to the following formula.
Step 2.2, screening the cable section with the ablation hidden danger of the buffer layer, wherein the specific method comprises the following steps:
(1) To and { l i } i＝1，...，n Cable segment set { q ] to be screened at same voltage level j } ｊ＝，...m And for all j =1,. And m, cable data information such as factory reports is arranged. The same contact area and wrinkle sheath inside surface area calculation method is applied as the screening threshold calculation process is maintained. Collecting data required by the calculation method of the contact area and the surface area of the inner side of the wrinkle sheath, and entering the step (2) if the data are insufficient; otherwise, entering the step (3).
(2) And for all the cable segments to be screened with insufficient data, actually testing the same-model same-batch cable segments, and supplementing the data required by the calculation method.
(3) Calculate the total contact area for all j =1 total (q j )。
(4) Calculating the inside surface area of the wrinkled sheath for all j =1 total-，pit (q j )。
(5) Calculation of contact ratio according to the following formula gives w (q) j )。
(6) Summarizing and calculating to obtain the contact of the cable section to be screenedRatio set { w (q) } j )} j＝1，...，m For all j =1.. Times, m, the following determinations are made: if w (q) j ) When t is less than or equal to t, q is added j Adding the potential hazards into a hidden danger list, otherwise, adding q into the hidden danger list j Excluded from the hidden danger list.
(7) And (5) sorting and outputting the hidden danger list. And finishing screening the cable section with the ablation hidden danger of the cable buffer layer.
And 2, rapidly screening the cable section with the ablation hidden danger of the buffer layer of the high-voltage power cable according to the surface area of the inner side of the corrugated sheath of the high-voltage power cable.
The contact area of the corrugated sheath and the buffer layer on the whole cable depends on the size information of the length of the actual cable segment, the thickness of insulation and the like, and the size design of the high-voltage cable of each cable supplier is not consistent. Since the contact area mainly reflects the contact condition of the buffered layer between the cable insulation shield and the corrugated sheath, in order to realize the comparison of cables with different sizes, the invention provides a method for performing comparison by using the contact ratio.
On the basis that the contact area can be calculated or estimated, the contact ratio is calculated using the following equation:
wherein w is a contact ratio between the buffer layer and the wrinkled jacket; s. the total The contact area of the corrugated sheath and the buffer layer; s total-pit Is the inside surface area of the corrugated sheath.
After the contact area of the wrinkle sheath and the buffer layer on the whole cable and the inner surface area of the wrinkle sheath are determined, a hidden danger cable section screening threshold value can be obtained according to the contact ratio information of the fault cable, and the hidden danger cable section screening threshold value is compared with the contact ratio information of the cable to be screened, so that the conclusion whether the cable to be screened contains the ablation hidden danger of the buffer layer is obtained.
Based on the above description, the specific implementation method of this step includes the following steps:
step 2.1, calculating a screening threshold value of the cable section with the ablation hidden danger of the buffer layer, wherein the specific flow is as follows:
(1) For a set of fault cable sections (l) under a specified voltage level i } i＝1，...，n And sorting cable data information such as factory reports and the like for all i =1. And respectively determining the contact area and the inner side surface area of the corrugated sheath. Finishing data required by the calculation method of the contact area and the surface area of the inner side of the wrinkle sheath, and entering the step (2) if the data are insufficient; otherwise, entering the step (3).
(2) And for all fault cable sections with insufficient data, actually testing the cable sections intercepted during fault processing, and supplementing the data required by the calculation method.
(3) For all i =1.. Times.n, the total contact area is calculated, resulting in S total (l i )。
(4) Calculating the inside surface area of the wrinkled sheath for all i =1 total-pit (l i )。
(5) The contact ratio was calculated according to the following formula to obtain w (l) i )。
(6) The summary calculation obtains a fault cable section contact ratio set w (l) i )} i＝1，...，n And calculating to obtain the screening threshold t of the cable section with the ablation hidden danger of the buffer layer under the voltage level according to the following formula.
Step 2.2, screening the cable section with the ablation hidden danger of the buffer layer, wherein the specific method comprises the following steps:
(1) To and { l i } i＝1，...，n Cable segment set { q ] to be screened at same voltage level j } j＝1，...，4 And for all j =1. The same contact area and wrinkle sheath inside surface area calculation method is applied as the screening threshold calculation process is maintained. Collecting contact area and wrinklesIf the data is insufficient, entering the step (2); otherwise, entering the step (3).
(2) And for all the cable segments to be screened with insufficient data, actually testing the same-model same-batch cable segments, and supplementing the data required by the calculation method.
(3) Calculate the total contact area for all j =1 total (q j )。
(4) Calculating the inside surface area of the wrinkled sheath for all j =1 total-pit (q j )。
(5) Calculation of contact ratio according to the following formula gives w (q) j )。
(6) The contact ratio set { w (q) of the cable segments to be screened is obtained through summarizing and calculating j )} j＝1，...，m For all j =1,.. M, the following determination is made: if w (q) j ) When t is less than or equal to t, q is added j Adding the potential hazards into a hidden danger list, otherwise, adding q into the hidden danger list j Excluded from the hidden danger list.
(7) And (5) sorting and outputting the hidden danger list. And finishing screening the cable section with the ablation hidden danger of the cable buffer layer.
The effect of the present invention is verified by one example as follows:
in the example, a cable section with ablation corrosion hidden danger of a buffer layer of a 220kV high-voltage power cable is screened. 3 sections of fault cable sections are shared, namely a fault section A, a fault section B and a fault section C; and 4 cable sections to be screened are respectively a first conveying section, a second conveying section, a third conveying section and a third conveying section.
And calculating a screening threshold value of the cable section with the ablation hidden danger of the buffer layer.
Step 1, collecting fault cable sections { l) under 220kV level i } i＝1，...，3 And sorting cable data information such as factory reports and the like for all i =1. Separately determining contact area and wrinkle sheath inside surface area calculationsA method. And (4) finishing the contact area and calculating the required data of the method for calculating the surface area of the inner side of the corrugated sheath. If the data is insufficient, entering the step 2; otherwise, entering the step 3.
And 2, for all fault cable sections with insufficient data, actually testing the cable sections intercepted during fault processing, supplementing the data required by the calculation method, and entering the step 3.
Through the first two steps, the input data of the sorted fault cable set are as follows:
and 3, respectively calculating the total contact area of all the i =1, the total (l i ) And the result is as follows, and step 4 is entered.
Step 4, for all i =1, 3, step 4.1 is entered, respectively.
At step 4.1, the example determined the use of a cubic polynomial interpolation method, which requires 4 interpolated data points. In that
Obtaining an interpolation base point rho by evenly distributing on the interval k K =1, 4, step 4.2 is entered.
Step 4.2, for all k =1,.., 4, on the same type of cable or batch of cable provided by the supplier in question, the base point ρ is interpolated in different corrugations k The Z-direction coordinate of the inner side of the wrinkle is measured in a position multi-point mode, and the coordinate (rho) of an interpolation data point can be obtained after the average value is obtained k ，0，z k ). And 4.3, entering the step 4.3.
The interpolated data point coordinates obtained after measurement are as follows:
step 4.3, interpolation data point (rho) is determined k ，0，z k ) K =1.. 4, and performing interpolation calculation to obtain an interpolation function expression f (ρ) = T 3 ρ 3 +T 2 ρ 2 +T 1 ρ+T 0 And entering the step 4.4.
The result of the cubic polynomial interpolation calculation is as follows:
step 4.4, to the inside surface area S of the corrugated sheath of the formula total-pit And (5) simplifying the integral, then calculating by using a numerical integration method to obtain a result, and entering the step 5 after the calculation of the inner side surface area of the wrinkle sheath is finished.
Step 5, calculating the contact ratio according to the following formula to obtain w (l) i ) And entering the step 6.
The calculation results are collated in the following table:
step 6, summarizing and calculating to obtain a fault cable section contact ratio set { w (l) i )} i＝1，...，3 Calculating the buffer layer under the voltage level according to the following formulaAnd (4) screening a threshold value t for the cable section with the ablation hidden danger.
In this example, it is calculated that t =13.72%.
And then, carrying out a buffer layer ablation hidden danger cable section screening process.
Step 1, for a 220kV voltage level cable segment set to be screened { q j } j＝1，...，4 And for all j =1, the. The same contact area and wrinkle sheath inside surface area calculation method is applied as the screening threshold calculation process is maintained. Collecting data required by the contact area and the wrinkle sheath inner side surface area calculation method, and entering the step 2 if the data are insufficient; otherwise, entering the step 3.
And step 2, for all the cable segments to be screened with insufficient data, actually testing the same-model same-batch cable segments, supplementing the data required by the calculation method, and entering step 3.
Through the first two steps, the input data of the cable set to be screened after the arrangement is as follows:
and 3, respectively calculating the total contact area of all j =1, j.. And 4 by adopting a method for calculating the contact area of the buffer layer and the wrinkle sheath to obtain S total (q j ) And the result is as follows, and step 4 is entered.
Step 4, go to step 4.1 for all j =1.
At step 4.1, the example determined to use a cubic polynomial interpolation method, which requires 4 interpolated data points. In that
The interpolation base points rho are obtained by the average distribution on the interval k K =1, 4, step 4.2 is entered.
Step 4.2, for all k =1,.., 4, on the same type of cable or batch of cable provided by the supplier in question, the base point ρ is interpolated in different corrugations k The position is measured at multiple points and the Z-direction coordinate is measured, and the coordinate (rho) of the interpolated data point can be obtained after the average value is obtained k ，0，z k ). And 4.3, entering the step 4.3.
The interpolated data point coordinates obtained after measurement are as follows:
step 4.3, according to the interpolation data point (rho) k ，0，z k ) K =1.. 4, and performing interpolation calculation to obtain an interpolation function expression f (ρ) = T 3 ρ 3 +T 2 ρ 2 +T 1 ρ+T 0 And entering the step 4.4.
The results of the cubic polynomial interpolation calculation are as follows:
step 4.4, to the inside surface area S of the corrugated sheath of the formula total-pit And (5) simplifying the integral, then calculating by using a numerical integration method to obtain a result, and entering the step 5 after the calculation of the inner side surface area of the wrinkle sheath is finished.
Step 5, contact ratio meter is carried out according to the following formulaCalculating to obtain w (q) j ) And entering the step 6.
The calculation results are collated in the following table:
step 6, summarizing and calculating to obtain a cable section contact ratio set { w (q) to be screened j )} j＝1，...，4 For all j =1,.. 4, the following determinations are made: if w (q) j ) Q is less than or equal to 13.72, then q is j Adding the potential hazards into a hidden danger list, otherwise, adding q into the hidden danger list j Excluded from the hidden danger list. And 7, entering the step.
And 7, sorting and outputting the hidden danger list to obtain a hidden danger list: { in second segment }.
It should be emphasized that the embodiments described herein are illustrative and not restrictive, and thus the present invention includes, but is not limited to, the embodiments described in the detailed description, as well as other embodiments that can be derived by one skilled in the art from the teachings herein.
Claims (1)
1. A method for screening potential ablation hazard cable sections of a buffer layer based on the inner surface area of a corrugated sheath is characterized by comprising the following steps: the method comprises the following steps:
step 1, approximately calculating the inner side surface area of a corrugated sheath of a high-voltage power cable according to the inner side surface area of the corrugated sheath in a single corrugated pitch;
step 2, according to the surface area of the inner side of the high-voltage power cable corrugated sheath, calculating the contact ratio of a fault cable section to obtain a buffer layer ablation hidden danger cable section screening threshold, and screening the buffer layer ablation hidden danger cable section through the buffer layer ablation hidden danger cable section screening threshold;
the specific implementation method of the step 1 comprises the following steps:
step (ii) of1.1, according to a cable factory test report or an actual measurement result, arranging to obtain the following data: length d of cable segment cable Nominal value, inside radius d of corrugated sheath OA Nominal value, wrinkle pitch d len Nominal value, wrinkle depth d dep A nominal value;
step 1.2, determining the selected interpolation method to obtain an interpolation base point rho k K =1, …, r, r is the number of interpolation data points required by the interpolation method;
step 1.3, interpolation of base points ρ in different corrugations on the same type of cable in the same batch of cables provided by the cable or supplier of interest, for all k =1, …, r k Measuring the Z-direction coordinate of the inner side of the wrinkle at multiple points at the position, and averaging to obtain the coordinate (rho) of the interpolated data point k ,0,z k )；
Step 1.4, interpolation data point (rho) k ,0,z k ) K =1, …, r, and performing interpolation calculation to obtain an interpolation function expression f (ρ);
step 1.5, inner surface area S of corrugated sheath of formula total-pit Simplifying the integration, then calculating by using a numerical integration method to obtain a result, and calculating the inner surface area of the wrinkle sheath:
when the screening threshold value of the cable section with the ablation hidden danger of the buffer layer is calculated, the contact ratio w (l) is calculated according to the following formula i )：
Wherein in the formula i } i＝1,...,n For a set of faulty cable sections at a given voltage level, S total (l i ) Is the total contact area, S total-pit (l i ) Is the inside surface area of the corrugated sheath;
the summary calculation obtains a fault cable section contact ratio set w (l) i )} i＝1,...,n And calculating a screening threshold t of the cable section with the potential ablation hazard of the buffer layer under the voltage level according to the following formula:
when screening cable sections with potential ablation hazards of buffer layers, setting and matching { l i } i＝1,...,n The cable segment set to be screened with the same voltage grade is { q } j } j＝1,...,m The contact ratio w (q) was calculated as follows j )：
The contact ratio set { w (q) of the cable segments to be screened is obtained through summarizing and calculating j )} j＝1,...,m For all j =1, …, m, the following determinations are made:
if w (q) j ) When t is less than or equal to t, q is added j Adding the potential hazards into a hidden danger list, otherwise, adding q into the hidden danger list j Excluded from the hidden danger list.
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