CN112763851B - Rapid screening method of cable segment with potential ablation based on inner surface area of corrugated sheath - Google Patents

Abstract

The invention relates to a rapid screening method for cable sections with potential ablation based on the inner surface area of a corrugated sheath. According to the inner surface area of the corrugated sheath of the high-voltage power cable, use the contact ratio of the faulty cable section recorded in the historical data to calculate the screening threshold of the cable section with potential buffer layer ablation, and quickly screen the buffer layer through the screening threshold of the cable section with potential buffer layer ablation Layer ablation potential cable segments. The invention has a reasonable design, and realizes the function of quickly screening the hidden cable section of the buffer layer ablation by approximately calculating the inner surface area of the corrugated sheath of the high-voltage power cable. A list of potential cable segments for buffer layer ablation of existing cables is presented, which provides a reference for the operation and maintenance of high-voltage power cables.

Description

Rapid screening method of cable segment with potential ablation based on inner surface area of corrugated sheath

technical field

The present invention is in the technical field of high voltage and insulation, in particular to a rapid screening method for cable sections with potential ablation based on the inner surface area of a corrugated sheath.

Background technique

In recent years, the number of faults caused by ablation of the buffer layer of high-voltage power cables has gradually increased, and the hidden danger of buffer layer ablation has become one of the important hidden dangers threatening the security of the power grid. At present, the screening method for hidden cable sections of buffer layer ablation of high-voltage power cables is still very preliminary. Usually, a method is adopted to summarize the list of cable suppliers that have experienced such faults, and list other non-faulty cables from the suppliers as hidden cables. This method usually results in the result that a large number of high-voltage power cables from several suppliers need to be technically modified or replaced, but the products of other suppliers are completely free of hidden dangers. This screening method does not take into account the technical information of specific cables. On the one hand, it is easy to overestimate the hidden dangers of cable products in the screened supplier list, and on the other hand, it is easy to ignore the risks of cable products from other suppliers. Therefore, it is necessary to develop a screening method for ablation hazards that incorporates cable information.

Usually the ablation of the water blocking buffer layer is usually accompanied by the following two phenomena: (1) the water blocking buffer layer is damp; (2) the electrical connection between the corrugated sheath, the buffer layer and the insulating shielding material is relatively weak. The former can be prevented by enhanced control during the cable production phase as well as the construction phase. The latter is still difficult to find a replacement for the combination of corrugated aluminum sheath-water blocking buffer layer-insulation shielding material in a short period of time. Therefore, under the premise that the material cannot be changed, and the buffer tape has been tightly wrapped around the insulating shield, the contact area between the corrugated sheath and the buffer layer has become the key information to determine the electrical connection between the corrugated sheath and the insulating shielding layer. Based on this, methods to screen for potential buffer ablation can be developed.

Ignoring the influence of cable bending, the intuitive estimation method of the contact area between the corrugated sheath and the buffer layer (hereinafter referred to as the contact area) is the cylindrical area formed by the outer circle of the buffer layer covering the cable and along the cable axis, or The estimated value of the contact area is the circular cylindrical area formed by the "valley" position inside the corrugated sheath along the cable axis. The premise of this method is that the corrugated sheath is in close contact with the buffer layer, which is inconsistent with the actual engineering, and will bring great errors when analyzing the electrical connection. Therefore, there is still a lack of effective calculation methods for the key technical parameter of contact area. The solution of this problem mainly faces the following challenges:

(1) Power cable suppliers generally use metal corrugated production lines for the production of corrugated sheaths. The technical parameters of sheath wrinkle are controlled by two production parameters of wrinkle pitch and wrinkle depth. This method cannot directly determine the typical shape parameters of smooth wrinkles with curvature radius. In addition, due to the existence of peaks and valleys in the corrugated sheath, the contact mode with the buffer layer in the axial direction of the cable is generally discontinuous. These problems bring difficulties to the mathematical modeling and calculation of the contact area between the corrugated sheath and the buffer layer.

(2) At present, the corrugated sheath and the buffer layer still lack corresponding standard constraints in terms of size matching. Taking into account the mechanical strength of the cable, axial water resistance and other performance requirements, different power cable suppliers have adopted different technical solutions on whether the diameter of the inner "valley" of the corrugated sheath is larger than the outer diameter of the cable with the buffer layer. Therefore, under the action of gravity, the inner side of the corrugated sheath above the cables of some suppliers does not form effective contact with the buffer layer, as shown in Figure 1; the inner side of the corrugated sheath above the cables of some suppliers forms effective contact with the buffer layer, such as shown in Figure 2. Clearly, there is a need for a computational method that can accommodate both cases.

(3) The early cables lacked the factory test report and other information, resulting in incomplete basic cable data, and it was difficult to provide sufficient information 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 ability to access the measured data in order to cope with the lack of cable information.

How to use the calculation of the inner surface area of the corrugated sheath of the high-voltage power cable and quickly screen the hidden cable section of the high-voltage power cable buffer layer ablation is an urgent problem to be solved at present.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and to propose a reasonably designed and fast and accurate method for quickly screening cable segments with potential ablation risks based on the inner surface area of the corrugated sheath.

The present invention solves its technical problem by adopting the following technical solutions to realize:

A rapid screening method for ablation potential cable segments based on the inner surface area of a corrugated sheath, comprising the following steps:

Step 1. Approximately calculate the inner surface area of the corrugated sheath of the high-voltage power cable according to the inner surface area of the corrugated sheath in a single corrugated pitch;

Step 2. According to the inner surface area of the corrugated sheath of the high-voltage power cable, use the contact ratio of the faulty cable section recorded in the historical data to calculate the screening threshold of the cable section with potential buffer layer ablation, and quickly pass the screening threshold of the cable section with potential buffer layer ablation Screen cable segments for potential buffer ablation.

Moreover, the concrete realization method of described step 1 is:

Step 1.1. Arrange the following data according to the cable factory test report or actual measurement results: cable segment length d _cable nominal value, corrugated sheath inner radius d _OA nominal value, wrinkle pitch d _len nominal value, wrinkle depth d _dep Nominal value, nominal value of corrugated sheath thickness d _al ;

Step 1.2. Calculate the inner surface area S _total-pit of the wrinkled sheath according to the following formula:

Moreover, the method for calculating the screening threshold of the cable segment of the buffer layer ablation hidden danger in the step 2 is:

(1) For the set of faulty cable segments {l _i } _i=1,...,n under the specified voltage level, sort out the data information of the factory cables, and sort out the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath. If the data is insufficient, Then enter step (2); otherwise, enter step (3);

(2) For all the faulty cable segments with insufficient data, carry out the actual test on the cable segments cut out during fault processing, fill in the data required by the contact area calculation method, and go to step (3);

(3) For all i=1,...,n, check whether there is a contact ratio calculation result record before l _i . For each specific i=1,...,n, if there is a contact ratio saving result, go to step ⑷; otherwise go to Step ⑸;

(4) For the faulty cable section numbered i, compare the data required for the calculation method of the contact area with the historical data, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data; if the two required data and the historical data are not available difference, and there is a contact ratio to save the result, then use the contact ratio to save the result w(l _i ), and go to step ⑹; otherwise, go to step ⑸, where:

⑸ For the faulty cable section numbered i, save the data required by the calculation method of the contact area as historical data to calculate the total contact area to obtain S _total (li _i ); save the data required by the calculation method of the inner surface area of the corrugated sheath as The historical data is used to calculate the inner surface area of the corrugated sheath to obtain S _total-pit (l _i ); the contact ratio w(l _i ) of the faulty cable section is calculated, and the calculation result of the contact ratio is saved;

(6) The set of contact ratios of faulty cable segments {w(l _i )} _i=1,...,n is obtained by summarizing the calculation, and the screening threshold t of the cable segment with potential buffer layer ablation under this voltage level is calculated:

Moreover, the specific implementation method of the rapid screening of the cable segment with the potential for ablation of the buffer layer is as follows:

(1) For the set of cable segments to be screened {q _j } _j=1,...,m at the same voltage level as {l _i } _i=1,...,n , sort out the factory cable data information, collect the contact area and wrinkles The data required for the calculation method of the inner surface area of the sheath, if the data is insufficient, then go to step (2); otherwise, go to step (3);

(2) For all cable segments to be screened with insufficient data, perform actual tests on cable segments of the same model and batch, fill in the data required for the calculation method of the contact area and the inner surface area of the wrinkled sheath, and go to step (3);

(3) For all j=1,...,m, check whether there is a contact ratio calculation result record before q _j ; for each specific j=1,...,m, if there is a contact ratio saving result, go to step (4); otherwise go to Step ⑸;

(4) For the cable section number j to be screened, compare the data required for the calculation method of the contact area with the historical data, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data; if the two required data are compared with the historical data There is no difference in the data, and there is a contact ratio storage result, then take the contact ratio storage result w(q _j ), and go to step ⑹; otherwise, go to step ⑸;

⑸ For the cable segment number j to be screened, save the data required by the contact area calculation method as historical data to calculate the total contact area to obtain S _total (q _j ); Save as historical data to calculate the inner surface area of the wrinkled sheath to obtain S _total-pit (q _j ); then calculate the contact ratio of the cable segment to be screened to calculate w (q _j ), and enter step (6), where:

(6) Collect and calculate the set of contact ratios of cable segments to be screened {w(q _j )} _j=1,...,m , and make the following judgments for all j=1,...,m: if w(q _j )≤ t, then q _j is added to the hidden danger list, otherwise q _j is excluded from the hidden danger list. Enter step ⑺;

⑺ Organize and output the hidden danger list, and screen the cable section of the cable buffer layer ablation hidden danger is completed.

The advantages and positive effects of the present invention are:

The design of the invention is reasonable, and it calculates the screening threshold of the hidden cable section of the buffer layer ablation by approximately calculating the inner surface area of the corrugated sheath of the high-voltage power cable according to the contact ratio of the faulty cable section recorded in the historical data, so as to realize the rapid screening of the buffer layer ablation. The function of hidden corrosion cable section can be used to evaluate the performance of high-voltage power cable corrugated sheath and buffer layer size matching, and gives a list of buffer layer ablation hidden cable sections of existing cables to provide reference for high-voltage power cable operation and maintenance.

Description of drawings

Fig. 1 is the schematic diagram of the non-contact situation between the corrugated sheath above the cable and the buffer layer;

Fig. 2 is the schematic diagram of the contact situation between the corrugated sheath above the cable and the buffer layer;

Figure 3 is an axial cross-sectional view of the contact surface between the corrugated sheath and the buffer layer;

FIG. 4 is a cross-sectional view of the approximate contact surface between the corrugated sheath and the buffer layer at θ= _θP plane.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

A rapid screening method for ablation potential cable segments based on the inner surface area of a corrugated sheath, comprising the following steps:

Step 1. Approximately calculate the inner surface area of the corrugated sheath of the high-voltage power cable.

The method for approximately calculating the inner surface area of the corrugated sheath of a high-voltage power cable proposed by the present invention is based on the following principles:

1. Calculation and decomposition of the inner surface area of the wrinkled sheath

Since there are peaks and valleys in the wrinkled sheath, in order to calculate the surface area of the wrinkled sheath, the following basic assumptions that are in line with engineering practice need to be made:

· Assume that the contact area within each wrinkle pitch is approximately the same;

• It is assumed that the effect of the inclination angle of the embossing on the contact area is negligible.

At this time, the contact area between the buffer layer and the corrugated sheath can be decomposed into the sum of the contact area between the buffer layer and the corrugated sheath within each corrugated pitch. Since a corrugated pitch is very small compared to the full length of the cable section, the contact area at both ends of the cable within less than one corrugated pitch can be approximated by a corresponding ratio. In the same way, the surface area of the wrinkle sheath can be decomposed, which can be obtained:

In the formula, S _total-pit is the surface area of the corrugated sheath; S _pit is the surface area of the corrugated sheath within a single corrugated pitch; d _cable is the nominal length of the cable segment; d _len is the nominal value of the corrugated pitch. Therefore, in order to obtain the inner surface area of the overall corrugated sheath of the cable, it is necessary to calculate the surface area of the corrugated sheath within a single corrugated pitch.

2. Approximate calculation of the inner surface area of the wrinkle sheath within a single wrinkle pitch

Considering that the contact surface between the actual buffer layer and the corrugated sheath is a space curved surface, in the radial plane of the cable, the center position O of the corrugated sheath is taken as the origin, as shown in Figure 1, the ρ-θ plane polar coordinates can be established. O' is the position of the center of the cable core, and the critical points where the buffer layer contacts the corrugated sheath are recorded as A and A'. As shown in Figure 3, on the basis of the ρ-θ plane coordinates, a three-dimensional coordinate system can be established with the cable axial direction as the Z direction. The dotted line in the figure is the schematic diagram of the contact surface between the buffer layer and the corrugated sheath. Obviously, within a wrinkle pitch, if the contact surface function is z=f(ρ, θ), the corresponding contact area can be calculated by the following formula:

Among them, Ωρθ is the projection of the inner curved surface of the corrugated sheath on the z=0 plane.

It can be seen from the introduction in the background section that the analytical expression of f(ρ, θ) is difficult to obtain. The approximation of the surface area of the inner side of the corrugated sheath can be obtained by performing surface integral calculation on a continuously differentiable approximation function of the z=f(ρ, θ) surface. This patent proposes an approximate calculation method for the inner surface area of a wrinkle sheath within a single wrinkle pitch. Since the projection of the inner curved surface of the corrugated sheath on the z=0 plane is symmetrical with a straight line in the direction of θ=0, and the inner curved surface of the corrugated sheath within a single corrugation pitch is symmetrical with the z=0 plane, the calculation of the value of S _pit only needs to In the interval of π≥θ≥0, Z≥0, the surface integral calculation can be multiplied by 4 times.

区间内的函数表达式为：In terms of the integrand, as shown in Figure 4, the approximate surface can be obtained in

The function expression in the interval is:

Among them, d _dep is the nominal value of the wrinkle depth; d _OA is the nominal value of the inner radius of the wrinkle sheath.

The approximate expression of the inner surface area of the wrinkled sheath within a single wrinkle pitch is:

Based on the above principles, the approximate calculation method for the inner surface area of the corrugated sheath of a high-voltage power cable given in this step includes the following steps:

Step 1.1. Arrange the following data according to the cable factory test report or actual measurement results: cable segment length d _cable nominal value, corrugated sheath inner radius d _OA nominal value, wrinkle pitch d _len nominal value, wrinkle depth d _dep Nominal value, wrinkle sheath thickness d _al nominal value.

Step 1.2. Calculate the inner surface area S _total-pit of the wrinkled sheath according to the following formula. The wrinkle sheath surface area is calculated.

Step 2. According to the inner surface area of the corrugated sheath of the high-voltage power cable, quickly screen the cable segment with potential ablation of the buffer layer of the high-voltage power cable.

The contact area between the corrugated sheath and the buffer layer on the entire cable depends on the actual cable segment length, insulation thickness and other dimensional information, and the high-voltage cable size design of various cable suppliers is not consistent. Since the contact area mainly reflects the contact between the cable insulation shield and the corrugated sheath through the buffer layer, in order to realize the comparison of cables of different sizes, the present invention proposes a method of using the contact ratio for comparison.

On the basis that the contact area can be calculated or estimated, the contact ratio is calculated using the following formula:

In the formula, w is the contact ratio between the insulating shield and the corrugated sheath; S _total-pit is the inner surface area of the corrugated sheath.

According to the contact ratio information of the faulty cable segment, the screening threshold of the hidden cable segment can be obtained, and compared with the contact ratio information of the cable to be screened, the conclusion is drawn whether the cable to be screened contains the hidden danger of buffer layer ablation.

According to actual needs, the rapid screening method for cable sections with potential buffer layer ablation will be run multiple times. On the premise that the input data remains unchanged, the calculation results of the contact ratio can be reused repeatedly; if other applications complete the calculation of the contact area, the calculation results will also be Can be saved for use in quick screening methods for cable sections with potential for buffer ablation to increase screening speed.

Based on the above description, the specific implementation method of this step includes the following steps:

Step 2.1. Calculate the screening threshold of the cable segment with hidden buffer layer ablation. The specific method is as follows:

(1) For the set of faulty cable segments {l _i } _i=1,...,n under the specified voltage level, for all i=1,...,n, sort out the cable data information such as the factory report, sort out the contact area and the inner side of the corrugated sheath The data required by the surface area calculation method, if the data is insufficient, then go to step (2); otherwise, go to step (3).

(2) For all the faulty cable segments with insufficient data, carry out the actual test on the cable segments cut out during fault processing, fill in the data required by the contact area calculation method, and go to step (3).

(3) For all i=1,...,n, check whether there is a contact ratio calculation result record before l _i . For each specific i=1,...,n, if there is a contact ratio saving result, go to step ⑷; otherwise, go to step ⑸.

(4) For the faulty cable section numbered i, compare the data required for the calculation method of the contact area with the historical data, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data. If there is no difference between the two required data and the historical data, and there is a contact ratio storage result, take the contact ratio storage result w(l _i ), and go to step ⑹; otherwise, go to step ⑸.

⑸ For the faulty cable segment with number i, save the data required by the contact area calculation method as historical data to calculate the total contact area and obtain S _total (l _i ). The data required by the method for calculating the surface area of the inner side of the corrugated sheath is saved as historical data to calculate the inner surface area of the corrugated sheath to obtain S _total-pit (l _i ). Then, the contact ratio calculation is performed according to the following formula to obtain w(l _i ), and the contact ratio calculation result is saved. Go to step ⑹.

(6) The set of contact ratios of faulty cable segments {w(l _i )} _i=1,...,n is obtained by summarizing and calculating, and the screening threshold t of cable segments with potential buffer layer ablation under the voltage level is calculated according to the following formula.

Step 2.2. Screen the cable segment for potential ablation of buffer layer

(1) For the set of cable segments to be screened {q _j } _j=1,...,m with the same voltage level as {l _i } _i=1,...,n , for all j=1,...,m, sort out From the factory report and other cable data information, collect the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath. If the data is insufficient, go to step (2); otherwise, go to step (3).

(2) For all cable segments to be screened with insufficient data, perform actual tests on cable segments of the same model and batch, fill in the data required for the calculation method of the contact area and the inner surface area of the wrinkled sheath, and go to step (3).

(3) For all j=1,...,m, check whether there is a record of the calculation result of the contact ratio before q _j . For each specific j=1,...,m, if there is a contact ratio saving result, go to step ⑷; otherwise, go to step ⑸.

(4) For the cable section number j to be screened, compare the data required for the calculation method of the contact area with the historical data, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data. If there is no difference between the two required data and the historical data, and there is a contact ratio storage result, take the contact ratio storage result w(q _j ), and go to step ⑹; otherwise, go to step ⑸.

⑸ For the cable segment number j to be screened, save the data required by the contact area calculation method as historical data to calculate the total contact area to obtain S _total (q _j ). The data required for the calculation method of the inner surface area of the corrugated sheath is saved as historical data, and the inner surface area of the corrugated sheath is calculated to obtain S _total-pit (q _j ). Then, the contact ratio is calculated according to the following formula to obtain w(q _j ).

Go to step ⑹.

(6) Collect and calculate the set of contact ratios of cable segments to be screened {w(q _j )} _j=1,...,m , and make the following judgments for all j=1,...,m: if w(q _j )≤ t, then q _j is added to the hidden danger list, otherwise q _j is excluded from the hidden danger list. Go to step ⑺.

⑺ Organize and output a list of hidden dangers. The cable segment screening for potential ablation of the cable buffer layer has been completed.

The effect of the present invention is verified below by two examples:

Example 1

In this example, the potential cable section for ablation and corrosion of the buffer layer of a 220kV high-voltage power cable is screened. There are 3 faulty cable sections in total, namely faulty section A, faulty section B and faulty section C; 4 cable sections to be screened are respectively in transport section A, in transport section B, in transport section C and in transport section D . All cables have no historical data and previous calculation results are saved.

First, the threshold calculation of the screening threshold of the cable segment with potential buffer layer ablation is carried out.

The first step is to collect {l _i } _i=1,...,3 for the faulty cable segments under 220kV level, and for all i=1,...,3, sort out the cable data information such as the factory report, sort out the contact area and wrinkle protection Set the data required by the inner surface area calculation method. If the data is insufficient, go to step 2; otherwise, go to step 3.

Step 2: For all faulty cable segments with insufficient data, perform actual tests on the cable segments cut out during fault handling, fill in the data required by the calculation method, and go to Step 3.

After the first two steps, the input data of the faulty cable set after sorting is as follows:

Step 3: For all _i =1, . For each specific i=1,...,3, if there is a contact ratio to save the result, go to step 4; otherwise, go to step 5.

Step 5: For the faulty cable section numbered i, save the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath as historical data, perform the calculation of the contact area, and go to step 5.1.

In step 5.1, calculate the inner surface area S _total-pit of the wrinkled sheath according to the following formula. After the inner surface area of the wrinkled sheath is calculated, go to step 5.2.

Step 5.2, then calculate the contact ratio according to the following formula to obtain w(l _i ), and save the calculation result of the contact ratio. Go to step 6.

The above calculation results are organized into the following table:

Step 6: Summarize and calculate to obtain a set of contact ratios of faulty cable segments {w(l _i )} _i=1,...,3 According to the following formula, calculate the threshold value t of cable segment screening for potential electrochemical corrosion of buffer layer under this voltage level:

In this example, the calculation can be obtained, t = 10.79%.

The screening process for cable segments with potential buffer ablation is then performed.

Step 1: Collect {q _j } _j=1,...,4 for the cable segment set to be screened at 220kV voltage level, and for all j=1,...,4, sort out the cable data information such as the factory report, collect the contact area and The data required for the calculation method of the inner surface area of the wrinkled sheath, if the data is insufficient, go to step 2; otherwise, go to step 3.

Step 2: For all cable segments to be screened with insufficient data, perform actual tests on cable segments of the same model and batch, fill in the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath, and go to Step 3.

After the first two steps, the input data of the cable set to be screened after sorting is as follows:

Step 3: For all j=1,...,4, check whether there is a contact ratio calculation result record before q _j . For each specific j=1,...,4, since there is no contact ratio to save the result, go to step 5.

Step 5: For the cable segment number j to be screened, save the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath as historical data, perform the contact area calculation, and go to step 5.1.

In step 5.1, calculate the inner surface area S _total-pit of the wrinkled sheath according to the following formula. After the inner surface area of the wrinkled sheath is calculated, go to step 5.2.

Step 5.2, then calculate the contact ratio according to the following formula to obtain w(q _j ), and save the calculation result of the contact ratio. Go to step 6.

The above calculation results are organized into the following table:

Step 6: Summarize and calculate to obtain a set of contact ratios of cable segments to be screened {w(q _j )} _j=1,...,4 , and make the following judgments for all j=1,...,4: if w(q j ) _j )≤10.79, then q _j is added to the hidden danger list, otherwise q _j is excluded from the hidden danger list. Go to step seven.

Step 7, organize and output the hidden danger list, and get the hidden danger list as: {in the transport section A, in the transport section B}.

Example 2

The scenario of Example 2 is based on the completion of the screening of hidden cable sections for high-voltage power cable buffer layer ablation in Example 1, the ablation of the buffer layer in the Transport A section causes a fault, and the actual measurement and update data are performed on the fault section in the Transport Section A. After that, it is necessary to perform the screening of the potential cable segment for buffer layer ablation again.

The following is the calculation of the screening threshold of the cable segment with potential buffer layer ablation.

The first step is to collect {l _i } _i=1,...,4 for the faulty cable segments under the 220kV voltage level, and for all i=1,...,4, sort out the cable data information such as the factory report, sort out the contact area and wrinkles The data required for the calculation method of the inner surface area of the sheath. If the data is insufficient, go to step 2; otherwise, go to step 3.

Step 2: For all faulty cable segments with insufficient data, perform actual tests on the cable segments cut out during fault processing, fill in the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath, and go to Step 3.

After the first two steps, the input data of the faulty cable set after sorting is as follows:

Step 3: For all i=1,...,4, check whether there is a contact ratio calculation result record before l _i . For each specific i=1,...,4, since there is a contact ratio to save the result, go to step 4.

The fourth step is to compare the data required for the calculation method of the contact area with the historical data for the faulty cable section numbered i, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data. If there is no difference between the two required data and the historical data, and there is a contact ratio storage result, take the contact ratio storage result w(l _i ), and go to step 6; otherwise, go to step 5.

Step 5: For the faulty cable section numbered i, save the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath as historical data, perform the calculation of the contact area, and go to step 5.1.

In step 5.1, calculate the inner surface area S _total-pit of the wrinkled sheath according to the following formula. After the inner surface area of the wrinkled sheath is calculated, go to step 5.2.

Step 5.2, then calculate the contact ratio according to the following formula to obtain w(l _i ), and save the calculation result of the contact ratio. Go to step 6.

Obviously, for i=1, . . . , 3, the contact ratio has saved results and the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath are no different from the historical data, and w(l _i ) can be directly obtained. For i=4, since the data required for the calculation method of the contact area and the surface area of the inner side of the corrugated sheath is different from the historical data, it is necessary to proceed to step 5 for calculation. A summary of the results is shown below.

The above calculation results are organized into the following table:

Step 6: Summarize and calculate to obtain the set of contact ratios of faulty cable segments {w(l _i )} _i=1,...,4 According to the following formula, calculate the threshold value t of cable segment screening for potential electrochemical corrosion of buffer layer under this voltage level:

In this example, the calculation can be obtained, t = 12.04%.

The following is the process of screening cable segments for potential buffer ablation.

Step 1: Collect {q _j } _j=1,...,3 for the 220kV voltage level cable segment set to be screened, and for all j=1,...,3, sort out the cable data information such as the factory report, collect the contact area and The data required for the calculation method of the inner surface area of the wrinkled sheath, if the data is insufficient, go to step 2; otherwise, go to step 3.

Step 2: For all cable segments to be screened with insufficient data, perform actual tests on cable segments of the same model and batch, fill in the data required for the calculation method of the contact area and the inner surface area of the corrugated sheath, and go to Step 3.

After the first two steps, the input data of the cable set to be screened after sorting is as follows:

Step 3: For all j=1,...,3, check whether there is a contact ratio calculation result record before q _j . For each specific j=1,...,3, since there is a contact ratio to save the result, go to step 4.

The fourth step is to compare the data required for the calculation method of the contact area with the historical data for the cable segment number j to be screened, and compare the data required for the calculation method of the inner surface area of the corrugated sheath with the historical data. If there is no difference between the two required data and the historical data, and there is a contact ratio storage result, take the contact ratio storage result w(q _j ), and go to step 6; otherwise, go to step 5.

Obviously, for j=1,...,3, the contact ratio has saved results and the data required by the contact area calculation method is no different from the historical data, and w(q _j ) can be directly obtained.

Step 6: Summarize and calculate to obtain a set of contact ratios of cable segments to be screened {w(q _j )} _j=1,...,3 , and make the following judgments for all j=1,...,3: If w(q j ) _j )≤12.04, then q _j is added to the hidden danger list, otherwise q _j is excluded from the hidden danger list. Go to step 7.

Step 7: Arrange and output the hidden danger list, and get the hidden danger list as: {In-transit Section B}.

It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive, so the present invention includes but is not limited to the embodiments described in the specific implementation manner. Other embodiments derived from the scheme also belong to the protection scope of the present invention.

Claims (1)

1. A method for rapidly screening ablation hidden danger cable sections 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, calculating a screening threshold of the cable section with the ablation hidden danger of the buffer layer by using the contact ratio of the fault cable section recorded in historical data according to the surface area of the inner side of the corrugated sheath of the high-voltage power cable, and quickly screening the cable section with the ablation hidden danger of the buffer layer through the screening threshold of the cable section with the ablation hidden danger of the buffer layer;

the specific implementation method of the step 1 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 Nominal value, wrinkled jacket thickness d _al A nominal value;

step 1.2, calculating the surface area S of the inner side of the wrinkled jacket according to the following formula _total-pit ：

When the screening threshold value of the cable segment with the ablation hidden danger of the buffer layer is calculated in the step, the set of the fault cable segments under the specified voltage level is set as { l } _i } _i＝1,...,n For the fault cable section with the number i, the data required by the contact area calculation method is stored as historical data, the total contact area is calculated according to the historical data, and S is obtained _total (l _i ) (ii) a The data required by the calculation method of the inner surface area of the wrinkled jacket is stored as historical data, and the inner surface area of the wrinkled jacket is calculated according to the historical data to obtain S _total-pit (l _i ) (ii) a Then, the contact ratio was calculated according to the following formula to obtain w (l) _i ) And saving the contact ratio calculation result:

the summary calculation results in a set of contact ratios of the fault cable sections { 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 the screening threshold value of the cable segment with the ablation hidden danger of the buffer layer is calculated, the data required by the contact area calculation method for the cable segment to be screened with the number j is saved as historical data, the total contact area is calculated, and S is obtained _total (q _j ) (ii) a The data required by the calculation method of the inner surface area of the wrinkle sheath is saved as historical data, so that the inner surface area of the wrinkle sheath is calculated to obtain S _total-pit (q _j ) (ii) a Then, the contact ratio calculation was performed according to the following formula to obtain w (q) _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, \ 8230;, m, the following determinations were made: if w (q) _j ) When t is less than or equal to t, q is added _j Adding the potential danger list, otherwise, adding q to the potential danger list _j Excluded from the hidden danger list.

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