Ultra-low frequency dielectric loss-based DC cable extrusion insulation aging state evaluation method

Abstract

The invention discloses an ultra-low frequency dielectric loss-based DC cable extrusion insulation aging state evaluation method, wherein the extrusion type solid insulation of a DC cable is adopted as a research object. The method comprises the following steps of preparing an insulated inner-layer slice sample, an insulated intermediate-layer slice sample and an insulated outer-layer slice sample of a cable; according to the rated operating voltage of the cable and the dimension parameters of the cable, determining a measurement voltage; measuring the dielectric loss of slice samples under different voltages at a frequency of 0.1 Hz; processing measurement data and preparing a dielectric loss-voltage graph in a normalized coordinate system; according to the dielectric loss values of the inner and outer layers of the dielectric loss-voltage graph and the varying trend thereof along with the application of an externally applied voltage, evaluating the extrusion insulation aging state of the DC cable. According to the technical scheme of the invention, the extrusion insulation aging state of the DC cable can be accurately evaluated, so that the real-time state of the extrusion type DC cable can be effectively determined. Meanwhile, the method is small in test sample size, and low in requirement on the voltage and the capacity of a test instrument. The influence of the test instrument on the system error is reduced. The requirement on the accuracy of the test instrument is lowered. Meanwhile, the data of the method are free from being compared with historical data, so that the method can be used for evaluating the cable state, wherein original data are missed.

Description

technical field [0001] The invention relates to a method for evaluating the insulation aging state of an extruded insulated DC cable, in particular to the slice measurement and data analysis of the ultra-low frequency dielectric loss tangent based on a solid medium, and for the DC power cable with extruded insulation. Methods for assessing the aging state of insulation. Background technique [0002] In recent years, DC cables have attracted worldwide attention due to their advantages in long-distance, high-voltage, large-capacity applications, especially across large water areas. At present, the most widely used extruded DC cables mainly use cross-linked polyethylene (XLPE) with stable internal structure and reliable performance as the insulating medium. During the manufacturing process of DC cables, there will inevitably be uneven insulation inside, and the cable laying process is also prone to defects in the insulation. After the DC cable is put into actual operation, un...

AI Technical Summary

Problems solved by technology

However, a large number of studies have found that the criteria listed in the standard are not applicable to engineering practice. For example, the standard stipulates that when the measured tanδ is greater than 4×10 -3 , it indicates that the cable is seriously aged and must be replaced immediately

In fact, a large number of cables in good condition have tanδ measurements greater than 4×10 -3 , and the measured value of tanδ itself is greatly affected by the test system and the external environment

[0007] For DC cables with extruded insulation, there is no relevant research on whether the 0.1Hz dielectric loss measurement value can be used to judge the aging state of the insulation, as well as the specific evaluation technology

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