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Cable insulation aging degree testing method and apparatus based on impact voltage

A technology of impulse voltage and cable insulation, applied in the direction of testing dielectric strength, etc., can solve the problems of large measurement deviation, small response current, and less cable characterization information, and achieve the effect of easy operation, advanced technology and high reliability

Active Publication Date: 2018-01-19
SICHUAN UNIV
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Problems solved by technology

[0003] However, the above-mentioned technology has the following disadvantages: (1) The response current of PDC is small (pA level) when testing short cables, and the test results are easily disturbed by the environment, and the measurement deviation is large; Spectrum testing is limited by the power of the power supply. It is difficult to test large-capacity equipment at high frequencies. It has not been used in long cable systems. In addition, the measurement of low-frequency bands takes a long time, and the on-site power outage time is sometimes difficult to meet; (3) XLPE cables with different frequencies The lower dielectric loss value comparison method obtains less characterization information of the cable, and cannot make a decisive judgment on the cable insulation state

Method used

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  • Cable insulation aging degree testing method and apparatus based on impact voltage
  • Cable insulation aging degree testing method and apparatus based on impact voltage
  • Cable insulation aging degree testing method and apparatus based on impact voltage

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Experimental program
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Embodiment 1

[0095] 1. Preparation of Short Cable Aging Samples

[0096] 1) Divide the YJLV22-8.7 / 15-3*95 short cables with a length of 40cm into three groups, which are marked as #1, #2, and #3, among which #1 is an unaged cable, and #2 is a one-month-aged cable. Cable, #3 is a cable aged 6 months.

[0097] 2) Use a steel needle to pierce small holes with a depth of 1.5mm at equal intervals (3-5mm) on the outer semiconductive layer of the cable sample. A volume of sodium chloride (Nacl) solution is then injected into the cavity of the heat shrink tubing and a copper electrode is inserted to ground. Further apply a high-frequency high-voltage signal with voltage U=6kV and frequency f=400Hz.

[0098] 3) One month later, #2 cable had obvious water tree defects inside, and the water tree length had exceeded 100 μm. After aging, the tanδ values ​​of the three batches of samples were tested with a dielectric loss tester. The test results are as follows: Table 1 shows.

[0099] Table 1 Diele...

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Abstract

The invention discloses a cable insulation aging degree testing method and apparatus based on impact voltages, and belongs to the electric cable detection field. According to the method, a frequency domain dielectric spectrum of a cable is obtained by obtaining voltage and current wave forms of the to-be-tested cable under the effect of different impact voltages, and the insulating aging degree ofthe cable is evaluated by obtaining dielectric response situations at the 0-10kHz frequency band in the frequency domain dielectric spectrum. Compared with a conventional dielectric response measuring method, the method has the advantages that a corresponding impact current amplitude is high, the impact currents are easy to measure and is not liable to be interfered by noise, and the impact voltage and current measuring technology is more mature. More information showing insulation aging of the cable can be obtained, and dielectric loss situations at different frequencies can be used for analysis and research. Therefore, the dielectric response under the effect of impact voltages can evaluate the aging degree of the cable more effectively.

Description

technical field [0001] The invention relates to a method and device for testing the aging degree of cable insulation based on impulse voltage, belonging to the field of power cable detection. technical background [0002] In the construction of urban distribution networks, the application of power cables is becoming more and more common, among which cross-linked polyethylene (XLPE) cables below 35kV are the main cables, which are widely used because of their reliable electrical and mechanical properties. At present, the domestic cables have a service life of about 20 years, and some cables are close to the end of the design life (30-40 years). Under the action of overvoltage, the insulation degradation area may cause electrical trees or even direct breakdown, which seriously threatens the stability of the power system. Therefore, it is of great significance and practical value to study the evaluation method of the cable operating state. In addition to the traditional preven...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/12
Inventor 周凯黄永禄赵世林何珉谢敏朱光亚冉立汪先进
Owner SICHUAN UNIV
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