CN115128454A - Method for detecting cable electrical performance parameters and judging conformity - Google Patents

Method for detecting cable electrical performance parameters and judging conformity Download PDF

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Publication number
CN115128454A
CN115128454A CN202111634334.0A CN202111634334A CN115128454A CN 115128454 A CN115128454 A CN 115128454A CN 202111634334 A CN202111634334 A CN 202111634334A CN 115128454 A CN115128454 A CN 115128454A
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uncertainty
cable
measurement
electrical performance
performance parameters
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滑景义
林敏�
李慧霞
廖伟超
付红兵
龙冰冰
何路华
张玉苹
尹云鹏
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Fangyuan Detection Certification Co ltd
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract

The invention discloses a method for detecting electrical performance parameters of a cable and judging the conformity of the electrical performance parameters of the cable, which comprises the following steps of: s1: measuring a certain conductive performance parameter of the cable for multiple times to obtain an average value
Figure DDA0003441312420000011
And measure uncertainty U X (ii) a S2: according to the mean value
Figure DDA0003441312420000012
And uncertainty U X The result of determining the performance index parameter X is:
Figure DDA0003441312420000013
s3: the performance measurement result X is compared with a value X specified in a standard min Or X max Make a comparison if
Figure DDA0003441312420000014
Or
Figure DDA0003441312420000015
Then it can be judged to be acceptable. The invention effectively reduces the misjudgment rate of the measurement result, thereby ensuring the improvement of the product inspection quality.

Description

Method for detecting cable electrical performance parameters and judging conformity
Technical Field
The invention relates to the technical field of wire and cable products, in particular to a method for detecting electrical performance parameters of a cable and judging the conformity of the electrical performance parameters of the cable.
Background
The electric wire and the cable are widely applied to various fields of national economy, provide important supporting guarantee for national defense construction, various industries, major projects and the like, and the conductivity of the electric wire and the cable is a key technical index for ensuring the quality of the electric wire and the cable. At present, various cable products manufactured at home and abroad are widely used in the field of power transmission and transformation transmission in China, and because the power cable is used for transmitting high-power electric energy and works under the conditions of high voltage and large current, the requirement on the electrical property of the power cable is very high, and in order to test the manufacturing and installation quality of the cable, reduce the operation accidents and improve the power supply reliability, the electrical property test and inspection must be carried out.
For cable products used in various engineering projects, the country only has the general detection technical requirements of the products, no specific method for qualified evaluation of the conductivity of the products exists, no unified detection result judgment standard exists, and particularly, when the measurement result of the conductivity of the cable is close to the required limit value, the influence of measurement errors cannot be reasonably analyzed to generate misjudgment, so that the quality of the cable products is difficult to ensure, the performance of some electric wire and cable products has hidden dangers, and the service life of the electric wire and cable products in long-term use is gradually reduced. In order to ensure that the electric conductivity of the electric wire and the cable can meet the technical requirements for inspection and the use requirements, the electric conductivity of key items influencing the product quality of the electric wire and the cable is necessary to be effectively controlled and can be higher than the index requirements of national technical standards and the specific requirements of customers, so that the misjudgment probability is reduced, and the product yield of the cable is effectively controlled. Therefore, a method for detecting and judging the electrical conductivity of the power cable product with unified specifications is imperative.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for detecting electrical performance parameters of a cable and judging the conformity of the electrical performance parameters of the cable.
In order to achieve the purpose, the invention adopts the following specific scheme:
a method for detecting electrical performance parameters of a cable and judging the conformity of the electrical performance parameters of the cable comprises the following steps:
s1: measuring a certain conductive property parameter of the cable for multiple times to obtain an average value
Figure RE-GDA0003825240030000011
And measure uncertainty U X ；
S2: according to the average value
Figure RE-GDA0003825240030000021
And uncertainty U X The result of determining the performance index parameter X is:
Figure RE-GDA0003825240030000022
±U X ；
s3: the performance measurement result X is compared with a value X specified in a standard min Or X max Make a comparison if
Figure RE-GDA0003825240030000023
Figure RE-GDA0003825240030000024
Or
Figure RE-GDA0003825240030000025
Then it can be judged to be acceptable.
Preferably, in step S1, the method for measuring uncertainty includes the following steps:
s101: measuring major effects of uncertainty, including measuring the introduced influence u of uncertainty by the measuring instrument 1 And repeated measurements introduce an uncertainty influence u 2 ；
S102: according to u 1 And u 2 Synthetic standard uncertainty u c ：
Figure RE-GDA0003825240030000026
S103: extended measurement uncertainty U X ：U X ＝k·u c Wherein k is a calculation factor, and k is an element of [1.5, 2 ]]。
Preferably, in step S3, if the measurement standard is given a lower limit value X min And the qualification judgment formula of the measurement result of the electrical property parameter is as follows:
Figure RE-GDA0003825240030000027
if the standard is given an upper limit value X max And the qualification judgment formula of the measurement result of the electrical property parameter is as follows:
Figure RE-GDA0003825240030000028
preferably, in step S1, the electrical property index parameter X of the cable product may represent a conductor dc resistance, an ac voltage, and a semiconductive shield resistivity.
By adopting the technical scheme of the invention, the invention has the following beneficial effects: the detection quality control and the detection judgment rule of the electric conductivity of the cable product are standardized, so that the technical index requirements and the use requirements of the technical standard of the product are met; according to the method, the conformity of the main performance of the electric wire and the electric cable is judged, the misjudgment rate of the measurement result is effectively reduced, and the improvement of the inspection quality of the product is further ensured.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a flow chart of measuring uncertainty according to the present invention;
FIG. 3 is a schematic diagram illustrating the determination of the eligibility of the measurement results according to the present invention;
FIG. 4 is a schematic diagram illustrating the qualification of the resistance measurement result according to the present invention.
Detailed Description
The invention is further described below with reference to the following figures and specific examples.
Referring to fig. 1, the present invention includes the steps of:
s1: measuring certain electrical property parameter of the cable for multiple times to obtain the average value
Figure RE-GDA0003825240030000031
And measure uncertainty U X ；
S2: according to the mean value
Figure RE-GDA0003825240030000032
And uncertainty U X The result of determining the performance index parameter X is:
Figure RE-GDA0003825240030000033
±U X ；
s3: the performance measurement X is compared with a minimum limit value X specified in the standard min Or maximum limit X max Make a comparison if
Figure RE-GDA0003825240030000034
Or
Figure RE-GDA0003825240030000035
Then it can be judged as eligible.
Referring to fig. 2, in the step S1, the method for measuring uncertainty includes the following steps:
s101: measuring major effects of uncertainty, including measuring the effects u of uncertainty introduced by the measuring instrument 1 And repeated measurements introduce an uncertainty influence u 2 ；
S102: according to u 1 And u 2 Synthetic standard uncertainty u c ：
Figure RE-GDA0003825240030000036
S103: extended measurement uncertainty U X ：U X ＝k·u c Wherein k is a calculation factor, and k is epsilon [1.5, 2 ]]。
In FIG. 3
Figure RE-GDA0003825240030000037
The measurement uncertainty U is extended for the measured average of the first electrical property parameter (black dot on the left) 1 The latter measurement results
Figure RE-GDA0003825240030000038
If the measured value still falls to the left of the minimum limit value, the measurement result is unqualified;
Figure RE-GDA0003825240030000039
extending the measurement uncertainty U as the measured average of the second electrical property parameter (second black dot) 2 The latter measurement results
Figure RE-GDA00038252400300000310
If the measured value falls into the right qualified area of the minimum limit value, the measurement result is qualified;
Figure RE-GDA00038252400300000311
extending the measurement uncertainty U as the mean of the measurement of the third electrical property parameter (third black dot) 3 The latter measurement results
Figure RE-GDA00038252400300000312
If the measured value falls into the qualified area on the left of the maximum limit value, the measurement result is qualified;
Figure RE-GDA00038252400300000313
the measurement uncertainty U is extended for the measured average of the fourth electrical property parameter (fourth black dot) 4 The latter measurement results
Figure RE-GDA00038252400300000314
If the measured value falls into the unqualified area on the right side of the maximum limit value, the measured result is judged to be unqualified.
Referring to fig. 4, taking the dc resistance, which is the most important indicator in the electrical performance of the cable, as an example, the specific measurement result evaluation process is as follows, wherein the abscissa m in the figure is the measurement sequence, and the ordinate R is the resistance value per kilometer:
1. measuring the direct current resistance parameters of the cable:
before measurement, a tested piece of the cable with the length of 1m is taken as required, the tested piece is stored in a laboratory for 12-24 hours, the conductor temperature of the tested piece is kept consistent with the temperature of the laboratory, the temperature of the laboratory is controlled at (20 +/-3) DEG C, and then the measurement work is started. Obtaining the average value of the DC resistance through multiple measurements
Figure RE-GDA00038252400300000315
Resistance measurement of a typical cable test piece
Figure RE-GDA00038252400300000316
The value of 1km length at 20 c should be corrected according to standard formulas and coefficients. According to the technical standard, a formula is recommended:
Figure RE-GDA00038252400300000317
in the formula, R 20 The resistance value of the conductor at 20 ℃ is shown in unit of omega/km;
Figure RE-GDA0003825240030000041
measuring the resistance of the conductor with the unit of omega/km; p is a resistance correction coefficient; and L is the length of the tested cable and has the unit of m.
Under normal measurement conditions, the resistance correction factor p is inversely proportional to the measured temperature change. When the conductor is measured at a standard temperature of 20 ℃, p is 1; the temperature increase was measured at 1 ℃ and p was decreased by 0.004; otherwise, the temperature is reduced by 1 ℃, and the p is increased by 0.004. For example, when the measurement temperature is 19 ℃, p is 1.004; when the measurement temperature is 21 ℃, p is 0.996; and so on.
At a laboratory ambient temperature of 21 deg.CUnder the test, a digital DC low resistance tester was used to measure a 1m cable test piece, the temperature correction coefficient p was 0.9960, and the average value was calculated 3 times
Figure RE-GDA0003825240030000044
The values of the standard resistance corrected to the length of 1km at 20 ℃ for the secondary measurements are: r is 20 ＝0.0000595×0.9960×1000/1＝0.0593Ω/km。
2. And (3) evaluating uncertainty of conductor direct current resistance measurement:
the uncertainty effect from the dc resistance measurement mainly comes from the following: uncertainty u introduced by the measuring instrument 1 And uncertainty u introduced by non-repeated reading 2 (ii) a The secondary influences of inaccurate measured length and lead resistance value can be generally ignored when performing measurement uncertainty evaluation.
(1) Measurement uncertainty u introduced for digital DC low resistance tester 1 The extended uncertainty U and k values given by the instrument's calibration certificate. For example, the spread uncertainty given by the resistance tester calibration certificate: u is 0.0004 omega/km, and k is 2; then: u. of 1 ＝U/k＝0.0004/2＝0.0002Ω/km。
(2) Repeatability measures the introduced uncertainty u 2 And repeatedly measuring the direct current resistance of each sample by the measuring instrument for n times, and calculating to obtain the direct current resistance measuring instrument. The specific measurement data are respectively: 0.0594 Ω/km, 0.0596 Ω/km, 0.0591 Ω/km, calculated according to the range method, with a range coefficient C of 1.64, yielding:
Figure RE-GDA0003825240030000042
(3) synthetic standard uncertainty u c ：
Figure RE-GDA0003825240030000043
And the extended uncertainty of the dc resistance measurement: u shape R ＝k×u c ＝2×0.0003＝0.0006Ω/km。
3. And D, judging the conformity of the direct current resistance measurement result:
(1) in practical work, the detection mechanism uses a digital direct-current low-resistance tester pair 300m 2 The three-core cable insulation core wire is measured, and the average measured value of the direct current resistance of the red, yellow and green three groups of wires is converted into a standard value of 20 ℃, and the standard value is respectively as follows: 0.0594 omega/km, 0.0595 omega/km and 0.0593 omega/km, and the maximum allowable value of the conductor direct current resistance is as follows when the technical standard requires 20 ℃: r max The degree of uncertainty of the measurement result is 0.0006 omega/km, and whether the conductor direct current resistance index is qualified or not needs to be judged.
According to the measured data, the yellow line resistance is the largest, and the maximum value of the measurement result after considering the uncertainty of the measurement is as follows: 0.0595+0.0006 ≤ 0.0601 ≤ R max Therefore, the product is judged to be qualified; the resistance values of the red line and the green line are both smaller than the resistance value of the yellow line, and the resistance value is obviously judged to be qualified; therefore, the dc resistance detection result of the cable is judged to be acceptable.
(2) Using a digital DC low resistance tester pair of 300m 2 The other group of three-core cable insulation core wire samples are measured, and the average measured direct current resistance values of the red wire, the yellow wire and the green wire are converted into standard values of 20 ℃ respectively: 0.0596 omega/km, 0.0595 omega/km and 0.0595 omega/km, and the maximum value of the conductor direct current resistance is allowed to be as follows when the technical standard requires 20 ℃: r max 0.0601 Ω/km and a measurement spread uncertainty of 0.0006 Ω/km (when k is 2), the conductor dc resistance index is still determined.
From the measurement data, considering the extended measurement uncertainty, the maximum values of the dc resistance measurement results of the yellow and green lines are: 0.0595+0.0006 ═ 0.0601 ═ R max All can be judged to be qualified; for the direct current resistance of the red line, the maximum value of the measurement result after considering the uncertainty of the measurement is as follows: 0.0596+0.006 ═ 0.0602 > R max Although the maximum value is exceeded, it cannot be directly judged as a fail because the value is very close to the maximum allowable value; when the calculation factor of the measurement uncertainty is reduced within the allowable range, for example, when k is 1.6, the spread uncertainty is not more than 0.0005 Ω/km, and at this time, the maximum value of the red line resistance measurement result is: r is less than 0.0596+0.0005＝R max The determination is qualified.
Therefore, the DC resistance measurement of the cable should be judged to be acceptable.
(3) In the same way as the detection method in the above example, if a cable sample has three cable direct current resistance average measured values of red, yellow and green, converted into standard values, the values are respectively: 0.0606 omega/km, 0.06070/km and 0.0608 omega/km, and the maximum value of the direct current resistance of the conductor is allowed to be as follows when the technical standard requires 20 ℃: r is max The conductor dc resistance index is still determined at 0.0601 Ω/km and the measurement spread uncertainty is 0.0006 Ω/km (when k is 2).
From the measured data, the minimum value of the green line direct current resistance measurement result after considering the extended measurement uncertainty is: 0.0608-0.0006 ═ 0.602 > R max (0.0601), so the determination is failed; red line measurement minimum: 0.0606-0.0006 ═ 0.0600 < R max (0.0601), but very close to the upper limit requirement, it cannot be directly determined as disqualified; when the calculation factor of the measurement uncertainty is reduced within the allowable range, for example, when k is 1.6, the extended uncertainty is not greater than 0.0005 Ω/km, and the minimum value of the red line resistance measurement result should be: r > 0.0606-0.0005 ═ R max (0.0601), so that the red line resistance measurement result is judged to be unqualified; similarly, the minimum green line resistance measurement should be: r > 0.0607-0.0005 ═ 0.0602 > R max (0.0601), the test piece was judged to be rejected.
Therefore, the measurement result of the direct current resistance of the cable sample can be judged to be unqualified.
The method for judging the conformity of the measurement results of other main electrical performance parameter indexes of the cable, such as alternating voltage, conductor shielding resistivity and the like, can refer to a judgment method of the direct current resistance measurement result.
The above description is only a preferred example of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields directly/indirectly applied to the present invention are included in the scope of the present invention.

Claims (4)

1. A method for detecting electrical performance parameters of a cable and judging the conformity of the electrical performance parameters of the cable is characterized by comprising the following steps of:
s1: measuring a certain conductive property parameter of the cable for multiple times to obtain an average value
Figure FDA0003441312390000011
And measure uncertainty U X ；
S2: according to the mean value
Figure FDA0003441312390000012
And uncertainty U X The result of determining the performance index parameter X is:
Figure FDA0003441312390000013
Figure FDA0003441312390000014
s3: the performance measurement result X is compared with a value X specified in a standard min Or X max Make a comparison if
Figure FDA0003441312390000015
Figure FDA0003441312390000016
Or
Figure FDA0003441312390000017
Then it can be judged to be acceptable.
2. The method for detecting and determining the cable electrical performance parameters according to claim 1, wherein in step S1, the method for measuring the uncertainty comprises the following steps:
s101: measuring major influence of uncertainty, including measuring influence u of uncertainty introduced by measuring instrument 1 And introduction of uncertainty in repeatability measurementQuantitative influence u 2 ；
S102: according to u 1 And u 2 Synthetic standard uncertainty u c ：
Figure RE-FDA0003825240020000018
S103: extended measurement uncertainty U X ：U X ＝k·u c Wherein k is a calculation factor, and k is an element of [1.5, 2 ]]。
3. The method for detecting and determining the cable electrical performance parameters as claimed in claim 1, wherein in step S3, if the measurement standard is given a lower limit value X min And the qualification judgment formula of the measurement result of the electrical property parameter is as follows:
Figure FDA0003441312390000019
if the standard is given an upper limit value X max And the qualification judgment formula of the measurement result of the electrical property parameter is as follows:
Figure FDA00034413123900000110
4. the method for detecting and determining the cable electrical performance parameters according to claim 1, wherein in step S1, the electrical performance index parameter X of the cable product represents a conductor dc resistance, an ac voltage, and a semiconductive shield resistivity.
CN202111634334.0A 2021-12-29 2021-12-29 Method for detecting cable electrical performance parameters and judging conformity Pending CN115128454A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117347721A (en) * 2023-10-07 2024-01-05 河北华伦线缆有限公司 Quality control method for high-conductivity cable
CN117452071A (en) * 2023-12-25 2024-01-26 深圳中缆电缆集团有限公司 Cable core resistance detection method in production process

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117347721A (en) * 2023-10-07 2024-01-05 河北华伦线缆有限公司 Quality control method for high-conductivity cable
CN117347721B (en) * 2023-10-07 2024-04-30 河北华伦线缆有限公司 Quality control method for high-conductivity cable
CN117452071A (en) * 2023-12-25 2024-01-26 深圳中缆电缆集团有限公司 Cable core resistance detection method in production process
CN117452071B (en) * 2023-12-25 2024-03-12 深圳中缆电缆集团有限公司 Cable core resistance detection method in production process

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