阅读说明：本技术 电缆缓冲层状态评价方法及系统 (Cable buffer layer state evaluation method and system ) 是由 张静 陈佳 程林 胡胜男 胡萍 江翼 李文杰 王浩明 刘衍宏 张�杰 于 2019-09-04 设计创作，主要内容包括：本发明涉及电工检测技术领域,更具体地说,涉及电缆缓冲层状态评价方法及系统,所述方法包括：获取被测电缆的透视图；根据被测电缆的透视图,计算得到被测电缆的脱离长度；所述脱离长度为：被测电缆中波纹铝保护套与缓冲层实际脱离的长度；根据被测电缆的参数,计算得到被测电缆的允许距离；所述允许距离为：被测电缆中波纹铝保护套与缓冲层被允许脱离的长度；对比被测电缆的脱离长度和允许距离,得到被测电缆的评价结果。本发明能够直观、准确地对缓冲层状态进行评价。(The invention relates to the technical field of electrician detection, in particular to a method and a system for evaluating the state of a cable buffer layer, wherein the method comprises the following steps: acquiring a perspective view of a cable to be tested; calculating the separation length of the cable to be detected according to the perspective view of the cable to be detected; the disengagement length is: the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable; calculating the allowable distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated; and comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable. The invention can intuitively and accurately evaluate the state of the buffer layer.)

1. A cable buffer layer state evaluation method is characterized by comprising the following steps:

acquiring a perspective view of a cable to be tested;

calculating the separation length of the cable to be detected according to the perspective view of the cable to be detected; the disengagement length is: the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

calculating the allowable distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated;

and comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable.

2. The method for evaluating the condition of the cable buffer layer according to claim 1, wherein the step of obtaining the perspective view of the tested cable specifically comprises the following steps:

and taking a picture of the inlet wire of the tested cable through a pulse ray machine to obtain an X-ray perspective view of the tested cable.

3. The method for evaluating the state of the buffer layer of the cable according to claim 1, wherein the step of calculating the separation length of the cable to be tested according to the perspective view of the cable to be tested specifically comprises the following steps:

identifying the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable according to the perspective view of the tested cable;

calculating the number of wave crests or wave troughs contained in the actually separated part of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

measuring the distance between two adjacent wave crests or wave troughs;

and calculating the separation length of the tested cable according to the distance between two adjacent peaks or troughs and the number of peaks or troughs contained in the actually separated part.

4. The method for evaluating the state of the buffer layer of the cable according to claim 1, wherein the step of calculating the allowable distance of the tested cable according to the parameters of the tested cable specifically comprises the following steps:

acquiring parameters of a tested cable, wherein the parameters comprise: the cable conductor shielding outer diameter, the cable insulating layer outer diameter, the buffer layer thickness, the cable insulating layer material dielectric constant, the buffer layer resistivity, the working voltage, the buffer layer allowable longitudinal voltage and the working power supply frequency;

calculating the allowable distance L of the tested cable according to the parameters; the concrete formula is as follows:

in the formula (1), d₁For shielding the cable conductor by the outer diameter d₂The outer diameter of the cable insulation layer, delta the thickness of the buffer layer, epsilon the dielectric constant of the cable insulation layer material, rho the resistivity of the buffer layer, U₀Working voltage, Us buffer layer allowed longitudinal voltage, f working power frequency.

5. The method for evaluating the state of the buffer layer of the cable according to claim 1, wherein the step of comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable specifically comprises the following steps:

comparing the separation length and the allowable distance of the tested cable;

when the separation length is smaller than the allowable distance, evaluating that the tested cable can continue to run;

and when the separation length is greater than or equal to the allowable distance, evaluating that the tested cable is in burning risk.

6. A cable buffer layer condition evaluation system, comprising:

the acquisition unit is used for acquiring a perspective view of the tested cable;

the calculation separation unit is used for calculating the separation length of the cable to be measured according to the perspective view of the cable to be measured; the disengagement length is:

the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

the calculation allowing unit is used for calculating and obtaining the allowed distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated;

and the comparison and evaluation unit is used for comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable.

7. The cable buffer layer state evaluation system of claim 6, wherein the obtaining unit is specifically configured to:

and taking a picture of the inlet wire of the tested cable through a pulse ray machine to obtain an X-ray perspective view of the tested cable.

8. The cable buffer status evaluation system according to claim 6, wherein the calculation disengagement unit includes:

the identification module is used for identifying the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable according to the perspective view of the tested cable;

the first calculation module is used for calculating the number of wave crests or wave troughs contained in the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable;

the measuring module is used for measuring the distance between two adjacent wave crests or wave troughs;

and the second calculation module is used for calculating the separation length of the tested cable according to the distance between two adjacent peaks or troughs and the number of the peaks or the troughs contained in the actually separated part.

9. The cable buffer layer condition evaluation system according to claim 6, wherein the calculation permission unit includes:

the acquisition module is used for acquiring parameters of the tested cable, and the parameters comprise: the cable conductor shielding outer diameter, the cable insulating layer outer diameter, the buffer layer thickness, the cable insulating layer material dielectric constant, the buffer layer resistivity, the working voltage, the buffer layer allowable longitudinal voltage and the working power supply frequency;

the third calculating unit is used for calculating the allowable distance L of the tested cable according to the parameters; the concrete formula is as follows:

in the formula (1), d₁For shielding the cable conductor by the outer diameter d₂The outer diameter of the cable insulation layer, delta the thickness of the buffer layer, epsilon the dielectric constant of the cable insulation layer material, rho the resistivity of the buffer layer, U₀Working voltage, Us buffer layer allowed longitudinal voltage, f working power frequency.

10. The cable buffer layer state evaluation system of claim 6, wherein the comparative evaluation unit is specifically configured to:

comparing the separation length and the allowable distance of the tested cable;

when the separation length is smaller than the allowable distance, evaluating that the tested cable can continue to run;

and when the separation length is greater than or equal to the allowable distance, evaluating that the tested cable is in burning risk.

Technical Field

The invention relates to the technical field of electrician detection, in particular to a method and a system for evaluating the state of a cable buffer layer.

Background

The technological level of the insulation manufacturing of power cables in China reaches the advanced level of the world, however, insulation breakdown faults caused by ablation of buffer layers of high-voltage cross-linked polyethylene (XLPE) insulation cables in operation still occur in China from 2011 to the present. According to the preliminary analysis of the breakdown faults and defects of more than dozens of bodies in Beijing, Shanghai, Jiangsu, Hunan and other places, the fault phenomena are found to be highly consistent. The insulation breakdown failure caused by the discharge ablation of the cable buffer layer is the only factor except the external force damage, which seriously influences the operation reliability of the high-voltage cable. However, ablation of the buffer layer of a high voltage cable lacks effective countermeasures, as well as inspection and detection means and defect assessment methods. Meanwhile, the defect characteristics of the buffer layer ablation by discharge are different from other defects of a cable line, and the buffer layer ablation defect can be effectively detected through the existing electrified or offline maintenance equipment and technical means without verification.

Disclosure of Invention

The invention aims to solve the technical problem of providing a cable buffer layer state evaluation method and system, which can intuitively and accurately evaluate the buffer layer state.

The technical scheme adopted by the invention for solving the technical problems is as follows: on one hand, the method for evaluating the buffer layer state of the construction cable comprises the following steps:

acquiring a perspective view of a cable to be tested;

calculating the separation length of the cable to be detected according to the perspective view of the cable to be detected; the disengagement length is: the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

calculating the allowable distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated;

and comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable.

Further, the acquiring of the perspective view of the tested cable specifically includes:

and taking a picture of the inlet wire of the tested cable through a pulse ray machine to obtain an X-ray perspective view of the tested cable.

Furthermore, the calculating of the detachment length of the cable to be measured according to the perspective view of the cable to be measured specifically includes:

identifying the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable according to the perspective view of the tested cable;

calculating the number of wave crests or wave troughs contained in the actually separated part of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

measuring the distance between two adjacent wave crests or wave troughs;

and calculating the separation length of the tested cable according to the distance between two adjacent peaks or troughs and the number of peaks or troughs contained in the actually separated part.

Still further, the calculating the allowable distance of the measured cable according to the parameter of the measured cable specifically includes:

acquiring parameters of a tested cable, wherein the parameters comprise: the cable conductor shielding outer diameter, the cable insulating layer outer diameter, the buffer layer thickness, the cable insulating layer material dielectric constant, the buffer layer resistivity, the working voltage, the buffer layer allowable longitudinal voltage and the working power supply frequency;

calculating the allowable distance L of the tested cable according to the parameters; the concrete formula is as follows:

in the formula (1), d₁For shielding the cable conductor by the outer diameter d₂The outer diameter of the cable insulation layer, delta the thickness of the buffer layer, epsilon the dielectric constant of the cable insulation layer material, rho the resistivity of the buffer layer, U₀Working voltage, Us buffer layer allowed longitudinal voltage, f working power frequency.

Still further, the comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable specifically includes:

comparing the separation length and the allowable distance of the tested cable;

when the separation length is smaller than the allowable distance, evaluating that the tested cable can continue to run;

and when the separation length is greater than or equal to the allowable distance, evaluating that the tested cable is in burning risk.

In another aspect, a cable buffer condition evaluation system is constructed comprising:

the acquisition unit is used for acquiring a perspective view of the tested cable;

the calculation separation unit is used for calculating the separation length of the cable to be measured according to the perspective view of the cable to be measured; the disengagement length is:

the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

the calculation allowing unit is used for calculating and obtaining the allowed distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated;

and the comparison and evaluation unit is used for comparing the separation length and the allowable distance of the tested cable to obtain the evaluation result of the tested cable.

Further, the obtaining unit is specifically configured to:

and taking a picture of the inlet wire of the tested cable through a pulse ray machine to obtain an X-ray perspective view of the tested cable.

Still further, the calculation detachment unit includes:

the identification module is used for identifying the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable according to the perspective view of the tested cable;

the first calculation module is used for calculating the number of wave crests or wave troughs contained in the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable;

the measuring module is used for measuring the distance between two adjacent wave crests or wave troughs;

and the second calculation module is used for calculating the separation length of the tested cable according to the distance between two adjacent peaks or troughs and the number of the peaks or the troughs contained in the actually separated part.

Still further, the calculation permission unit includes:

the acquisition module is used for acquiring parameters of the tested cable, and the parameters comprise: the cable conductor shielding outer diameter, the cable insulating layer outer diameter, the buffer layer thickness, the cable insulating layer material dielectric constant, the buffer layer resistivity, the working voltage, the buffer layer allowable longitudinal voltage and the working power supply frequency;

the third calculating unit is used for calculating the allowable distance L of the tested cable according to the parameters; the concrete formula is as follows:

in the formula (1), d₁For shielding the cable conductor by the outer diameter d₂The outer diameter of the cable insulation layer, delta the thickness of the buffer layer, epsilon the dielectric constant of the cable insulation layer material, rho the resistivity of the buffer layer, U₀Working voltage, Us buffer layer allowed longitudinal voltage, f working power frequency.

Still further, the comparison and evaluation unit is specifically configured to:

comparing the separation length and the allowable distance of the tested cable;

when the separation length is smaller than the allowable distance, evaluating that the tested cable can continue to run;

and when the separation length is greater than or equal to the allowable distance, evaluating that the tested cable is in burning risk.

The implementation of the invention has the following beneficial effects:

1. the invention adopts an image recognition mode, so that the judgment of the detection result is more intuitive, and meanwhile, the accuracy of the judgment result is improved by combining the field measurement of the distance between wave crests or wave troughs of the corrugated aluminum sheath.

2. The invention adopts the separation length as a parameter to evaluate the state, and has uniqueness, flexible field application and high detection efficiency.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic flow diagram of the process of the present invention;

FIG. 2 is a schematic diagram of the system of the present invention;

FIG. 3 is a schematic flow chart of a method according to an embodiment of the present invention.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the method for evaluating the state of the buffer layer of the cable according to the present invention includes:

101. acquiring a perspective view of a cable to be tested; specifically, the method comprises the following steps:

and taking a picture of the inlet wire of the tested cable through a pulse ray machine to obtain an X-ray perspective view of the tested cable.

102. Calculating the separation length of the cable to be detected according to the perspective view of the cable to be detected; the disengagement length is: the actual separation length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable; specifically, the method comprises the following steps:

1021. identifying the part, actually separated from the buffer layer, of the corrugated aluminum protective sleeve in the tested cable according to the perspective view of the tested cable;

1022. calculating the number n of wave crests or wave troughs contained in the actually separated part of the corrugated aluminum protective sleeve and the buffer layer in the tested cable;

1023. measuring the distance a between two adjacent peaks or troughs; specifically, the method comprises the following steps:

1024. and calculating the separation length of the tested cable according to the distance between two adjacent peaks or troughs and the number of peaks or troughs contained in the actually separated part.

In the invention, the separation length l of the tested cable is (n +2) multiplied by a;

103. calculating the allowable distance of the tested cable according to the parameters of the tested cable; the allowable distance is: the length of the corrugated aluminum protective sleeve and the buffer layer in the tested cable allowed to be separated; specifically, the method comprises the following steps:

acquiring parameters of a tested cable, wherein the parameters comprise: the cable conductor shielding outer diameter, the cable insulating layer outer diameter, the buffer layer thickness, the cable insulating layer material dielectric constant, the buffer layer resistivity, the working voltage, the buffer layer allowable longitudinal voltage and the working power supply frequency;

calculating the allowable distance L of the tested cable according to the parameters; the concrete formula is as follows:

in the formula (1), d₁For shielding the cable conductor by the outer diameter d₂The outer diameter of the cable insulation layer, delta the thickness of the buffer layer, epsilon the dielectric constant of the cable insulation layer material, rho the resistivity of the buffer layer, U₀Working voltage, Us buffer layer allowed longitudinal voltage, f working power frequency.

104. Comparing the separation length and the allowable distance of the tested cable to obtain an evaluation result of the tested cable; specifically, the method comprises the following steps:

comparing the separation length and the allowable distance of the tested cable;

when the separation length is smaller than the allowable distance, evaluating that the tested cable can continue to run;

and when the separation length is greater than or equal to the allowable distance, evaluating that the tested cable is in burning risk.

In the invention, if the corrugated aluminum protective sleeve in the tested cable is not separated from the buffer layer, the tested cable is evaluated to be in good contact without burning risk.

The above technical solutions of the embodiments of the present invention are described in detail below with reference to application examples:

as shown in fig. 3, the cable buffer layer state evaluation method according to the present invention:

example 1, a cable test site;

step 1, acquiring an X-ray perspective image of a cable by adopting a portable pulse ray machine;

step 2, identifying the contact state of the corrugated aluminum sheath and the buffer layer by using an image:

if the corrugated aluminum sheath is not separated from the buffer layer, directly evaluating the good contact of the tested cable;

if the corrugated aluminum sheath and the buffer layer have a certain length and are not in contact, entering step 3;

step 3, identifying 18 untouched wave crests through the image; measuring the distance between two adjacent wave crests of the corrugated aluminum sheath by 2cm on site to obtain the separation length of the corrugated aluminum sheath and the buffer layer, wherein the separation length is 40 cm;

step 4, obtaining parameters of the cable, wherein the cable is a 110kV 630mm2XLPE cable, and the outer diameter d of a cable conductor shield of the cable₁Is 32.8mm, and the outer diameter d of the cable insulation layer₂65.8mm, slowThe thickness delta of the strike layer is 3mm, the material of the cable insulation layer is XLPE, the dielectric constant epsilon of the cable insulation layer is 2.3, and the resistivity rho of the buffer layer is 10⁶Omega mm, working voltage of U₀Is 6.4X 10³V, allowing the longitudinal voltage Us to be 100V and the working power supply frequency f to be 50Hz by the buffer layer;

step 5, calculating to obtain the allowable distance L of the tested cable, which is 18.75 cm;

step 6, comparing the separation length of the cable with the allowable distance,

and 7, obtaining an evaluation conclusion that: the cable to be tested is at risk of burning.