Non-destructive method for evaluating aging and operation state of cables

Abstract

The invention relates to a non-destructive method for evaluating an aging and operation state of cables. According to the method, electromagnetic shielding for two ends of all detected cables is carried out; polarization processing is carried out, insulation of one end is carried out, the other end is connected with a high voltage DC power source, and instantaneous short circuit processing on the polarized cables is carried out to remove free charges on surfaces; a de-polarization test system is accessed to realize de-polarization, isothermal relaxation currents are automatically measured and recorded through a computer, the isothermal relaxation currents I are taken as ordinates, the times t are taken as abscissas, a characteristic curve of the isothermal relaxation currents along with change of the times t is acquired, an aging factor A is acquired, the aging degree can be determined by comparing aging factors of to-be-detection cables and un-aged cables, and the aging and operation state of the cables is evaluated. The method realizes non-destructive detection, can not only evaluate insulation performance of the cables, but also can acquire internal spatial charge and trap distribution characteristics of the cables, and the method has great importance for evaluating insulation performance of the cables.

Description

technical field [0001] The invention belongs to the field of electrical insulation, and in particular relates to an evaluation method combined with relevant parameters such as the distribution characteristics of insulation internal traps, in particular to a non-destructive method for evaluating cable aging and operating status. Background technique [0002] The aging of cable insulation is an important factor affecting the electrical performance of cables, so the evaluation of the aging state and insulation life of cables in actual operation has always been the focus of attention in the industry. [0003] The withstand voltage method and the dielectric loss factor method are the experimental methods commonly used to evaluate XLPE cables. The withstand voltage method is a method for directly judging the cable insulation performance, which can evaluate the cable life more accurately, but it is difficult to accurately distinguish the influence of distributed defects and concent...

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Problems solved by technology

The withstand voltage method is a method for directly judging the cable insulation performance, which can evaluate the cable life more accurately, but it is difficult to accurately distinguish the influence of distributed defects and concentrated defects on the cable life by this method, and after withstand voltage, if the The discharge time of the cable core is not enough, and its residual charge will affect the measurement of insulation resistance

Moreover, during the experiment, this method needs to be constantly compared with the parameters of the new cable, and the data processing process is relatively cumbersome.

The dielectric loss factor method is mainly based on harmonic analysis to measure the dielectric loss angle δ. Because the power frequency signal of the power system is affected by various factors, its fundamental frequency will fluctuate to a certain extent, which is not always the ideal 50Hz, and The test and analysis of the dielectric loss angle δ based on the harmonic analysis method will also produce large errors due to the phenomenon of "spectrum leakage"

These disadvantages limit the popularization and application of these methods

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