CN111025092B - XLPE cable terminal air gap defect safety intelligent and rapid assessment method - Google Patents
XLPE cable terminal air gap defect safety intelligent and rapid assessment method Download PDFInfo
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- CN111025092B CN111025092B CN201911136890.8A CN201911136890A CN111025092B CN 111025092 B CN111025092 B CN 111025092B CN 201911136890 A CN201911136890 A CN 201911136890A CN 111025092 B CN111025092 B CN 111025092B
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- G—PHYSICS
- 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
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- 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
- G01R31/003—Environmental or reliability tests
Abstract
The invention is an XLPE cable terminal air gap defect security intelligence rapid assessment method, the invention is at first to set up the cable leakage current test platform to the XLPE cable test leakage current tested; the data acquisition unit (7) acquires current data every 2s, and each acquisition lasts for 10min for 9 rounds; a size-leakage current coefficient matrix Q is then calculated, and the thickness of the air gap defect is then calculated from the size-leakage current coefficient matrix QhAnd lengthlObtaining a general expression of an influence factor delta of the XLPE cable terminal air gap defect by using the parameters; finally, measuring the size and thickness of the air gap defect of the XLPE cable terminal before putting operationh=h 0And lengthl=l 0Calculating the air gap defect impact factor delta0The method and the device can evaluate the safety of the air gap defect of the XLPE cable terminal, can quickly, accurately and efficiently identify the defective cable, provide targeted guidance for field maintenance personnel during cable inspection work, reduce workload and lay a foundation for ensuring the safe operation of the cable.
Description
Technical Field
The invention belongs to the field of XLPE cable insulation defect safety assessment, and particularly relates to an intelligent and rapid XLPE cable terminal air gap defect safety assessment method.
Background
Crosslinked polyethylene (XLPE) is widely used in power distribution cables because of its simple structure, light weight, good heat resistance, strong load capacity, chemical corrosion resistance, high mechanical strength, and the like. On one hand, the XLPE cable which runs in a power grid for a long time has indefinite change of external environment, is influenced by low-temperature alternation, high-low pressure alternation and the like, accelerates the development of cable insulation aging and forms air gap defects, and on the other hand, due to the non-standardization of the process, such as the deviation of a stress tube, uneven coating of stress dispersion glue, scratches of a cutter, an air gap is left in the XLPE cable terminal, and the cable is caused to break down under high voltage and high current, thereby seriously threatening the safe running of the power grid.
However, the threat level to XLPE cables will vary significantly due to the size of the air gap, and even when the air gap size is small, there will be little effect on the cable, which can still be put into operation. Therefore, whether the size of an air gap existing in the XLPE cable terminal is safe or not is evaluated efficiently and conveniently, the fault occurrence rate of the XLPE cable and the cable cost are reduced, a method capable of effectively evaluating the safety of the insulation air gap containing defect of the XLPE cable of the power distribution network before operation is urgently needed, the method is an intelligent and rapid evaluation method for the safety of the air gap defect of the XLPE cable terminal, the method is simple to operate, and the safety of the air gap defect of the cable can be effectively evaluated by calculating and detecting leakage current.
Disclosure of Invention
The invention aims to provide an intelligent and rapid assessment method for the safety of the air gap defect of an XLPE cable terminal, which is simple to operate and can effectively assess the safety of the air gap defect of a cable by calculating and detecting leakage current.
The technical scheme of the invention is as follows:
an intelligent and rapid assessment method for security of an air gap defect of an XLPE cable terminal comprises the following steps:
step 1: building cable leakage current test platform
A port 1 of a high-frequency voltage source is connected with a copper terminal of an XLPE cable terminal through a high-voltage test wire, a port 2 of the high-frequency voltage source is grounded, a grounding wire of the XLPE cable terminal penetrates through a high-frequency current transformer, the high-frequency current transformer is connected with a data acquisition unit, the data acquisition unit is connected with an upper computer, rated voltage U is applied to the XLPE cable terminal, and the upper computer records leakage current value In；
Step 2: setting a sampling period
The data acquisition unit acquires current data every 2s, and each acquisition is continuous10min, continuously performing 9 rounds, and recording current data acquired by the high-frequency current transformer as IijRepresents the j data collection in the ith round of collection, wherein i belongs to [1,9 ]]，j∈[1,300]I and j are integers;
and step 3: calculating a size-leakage current coefficient matrix Q
According to the step 2, the 1 st round of collected data is made to be I1jThe 2 nd round of data acquisition is I2j…, and so on, the 9 th round of data acquisition is I9j；
(6) In the formula, h is the air gap defect thickness, l is the breath defect length, unit: mm;
and 4, step 4: calculating an influence factor delta of an air gap defect of an XLPE cable terminal
γmax(QTQ) is QTMaximum eigenvalue of Q, gammamin(QTQ) is QTThe minimum eigenvalue of Q;
and 5: XLPE cable terminal air gap defect safety assessment
Before the XLPE cable is put into operation, the thickness h which has air gap defect at the terminal is measured0And length l ═ l0And substituting the equation (2) into the equation (2) to calculate the influence factor delta-delta of the XLPE cable air gap defect0,
When the influence factor of the XLPE cable terminal air gap defect is more than 0 and less than delta0Less than or equal to 2.34, safe air gap defect, no influence on XLPE cable, and when the air gap defect influence factor delta of XLPE cable terminal0> 2.34, air gap defect is unsafe, has an effect on XLPE cable, and delta0The larger the air gap, the more severe the threat to XLPE cables.
The invention relates to an intelligent and rapid evaluation method for the safety of an XLPE cable terminal air gap defect, which has the following advantages:
(1) the evaluation method has the advantages of concise data acquisition steps, simple and understandable operation flow and rigorous and reliable calculation process, and the intelligent and rapid evaluation method for the air gap defect safety of the XLPE cable terminal can quickly, accurately and efficiently identify the defective cable, provide targeted guidance for field maintenance personnel during cable inspection work, and reduce the workload.
(2) The evaluation method can accurately estimate the size of the air gap defect in the XLPE cable insulation through the detection and treatment of the leakage current, can further effectively judge the operation safety of the XLPE cable insulation, and can achieve the purpose of reducing the accident rate of cable explosion, breakdown and the like in operation.
Drawings
FIG. 1 is a schematic diagram of a leakage current detection connection according to the present invention.
Detailed Description
The invention is further illustrated below with reference to fig. 1:
step 1: building cable leakage current test platform
A port 1 9 of a high-frequency voltage source 1 is connected with a copper terminal 3 of an XLPE cable terminal 6 through a high-voltage test wire 2, a port 2 is grounded, a grounding wire 5 of the XLPE cable terminal 6 penetrates through a high-frequency current transformer 4, the high-frequency current transformer 4 is connected with a data collector 7, the data collector 7 is connected with an upper computer 8, a rated voltage U is applied to the XLPE cable terminal 6, and an upper computer 8 records a leakage current value In；
Step 2: setting a sampling period
The data collector 7 collects current data every 2s for 10min every time, the current data collected by the high-frequency current transformer 4 are recorded as IijRepresents the j data collection in the ith round of collection, wherein i belongs to [1,9 ]]， j∈[1,300]I and j are integers;
and step 3: calculating a size-leakage current coefficient matrix Q
According to the step 2, the 1 st round of collected data is made to be I1jThe 2 nd round of data acquisition is I2j…, byBy analogy, the 9 th round of data acquisition is I9j；
(6) In the formula, h is the air gap defect thickness, l is the breath defect length, unit: mm;
and 4, step 4: calculating an influence factor delta of an air gap defect of an XLPE cable terminal
γmax(QTQ) is QTMaximum eigenvalue of Q, gammamin(QTQ) is QTThe minimum eigenvalue of Q;
and 5: XLPE cable terminal air gap defect safety assessment
Before the XLPE cable is put into operation, the thickness h which has air gap defect at the terminal is measured0And length l ═ l0And substituting the equation (2) into the equation (2) to calculate the influence factor delta-delta of the XLPE cable air gap defect0,
When the influence factor of the XLPE cable terminal air gap defect is more than 0 and less than delta0Less than or equal to 2.34, safe air gap defect, no influence on XLPE cable,
when XLPE cable terminal air gap defect influence factor delta0> 2.34, air gap defect is unsafe, has an effect on XLPE cable, and delta0The larger the air gap, the more severe the threat to XLPE cables.
For example, the thickness of an air gap defect of 0.5mm and the length of the air gap defect of 0.5mm are measured on an XLPE cable terminal before a release operation, and the influence factor delta of the air gap defect of the XLPE cable terminal is calculated by respectively substituting the expressions (1) and (2)0And if the air gap is 0.657, the air gap is safe and can be put into operation.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (1)
1. An intelligent and rapid assessment method for security of an air gap defect of an XLPE cable terminal is characterized by comprising the following steps:
step 1: building cable leakage current testing platform
A No. 1 port (9) of a high-frequency voltage source (1) is connected with a copper terminal (3) of an XLPE cable terminal (6) through a high-voltage test line (2), a No. 2 port (10) is grounded, a grounding line (5) of the XLPE cable terminal (6) penetrates through a high-frequency current transformer (4), the high-frequency current transformer (4) is connected with a data collector (7), the data collector (7) is connected with an upper computer (8), rated voltage U is applied to the XLPE cable terminal (6), and a leakage current value I is recorded by the upper computer (8)n；
Step 2: setting a sampling period
The data collector (7) collects current data once every 2s, each time lasts for 10min, 9 times, and the current data collected by the high-frequency current transformer (4) is marked as IijRepresents the j data collection in the ith round of collection, wherein i belongs to [1,9 ]]，j∈[1，300]I and j are integers;
and step 3: calculating a size-leakage current coefficient matrix Q
According to the step 2, the 1 st round of collected data is made to be I1jThe 2 nd round of data acquisition is I2j,., and so on, the 9 th round of data acquisition is I9j；
Wherein h is the air gap defect thickness, l is the breath defect length, unit: mm;
and 4, step 4: calculating an influence factor delta of an air gap defect of an XLPE cable terminal
γmax(QTQ) is QTMaximum eigenvalue of Q, gammamin(QTQ) is QTThe minimum eigenvalue of Q;
and 5: XLPE cable terminal air gap defect safety assessment
Before the XLPE cable is put into operation, the thickness h which has air gap defect at the terminal is measured0And length l ═ l0And substituting the equation (2) into the equation (2) to calculate the influence factor delta-delta of the air gap defect of the XLPE cable terminal0，
When the influence factor of the XLPE cable terminal air gap defect is more than 0 and less than delta0Less than or equal to 2.34, safe air gap defect, no influence on XLPE cable,
when XLPE cable terminal air gap defect influence factor delta0> 2.34, air gap defect is unsafe, has an effect on XLPE cable, and delta0The larger the air gap, the more severe the threat to XLPE cables.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS63205578A (en) * | 1987-02-20 | 1988-08-25 | Sumitomo Electric Ind Ltd | Method for diagnosing deterioration of crosslinked polyethylene insulated cable |
| JPH07306241A (en) * | 1994-05-11 | 1995-11-21 | Hitachi Cable Ltd | Insulation deterioration judging method for power cable |
| US9255970B2 (en) * | 2012-09-27 | 2016-02-09 | General Electric Company | On-line monitoring of stator insulation in motors and generators |
| KR101466623B1 (en) * | 2014-07-09 | 2014-11-28 | 한국전력공사 | Apparatus and method for condition diagnosis and predicting remains life of power cable status using the vlf td measured data |
| CN105842598A (en) * | 2016-06-14 | 2016-08-10 | 国家电网公司 | Cross-linked polyethylene cable life detection method |
| CN107621595A (en) * | 2017-03-28 | 2018-01-23 | 国网四川省电力公司电力科学研究院 | A kind of Condition assessment of insulation device and method of power cable |
| CN109917251B (en) * | 2019-04-09 | 2021-06-01 | 国网江苏省电力有限公司电力科学研究院 | Method for predicting aging life of XLPE cable insulation material |
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