Abstract
In order to study the failure mechanism of high-voltage cable buffer layer caused by moisture and the performance of the material after immersion and drying, according to the structure and size of 110 kV XLPE cable, the requirements for the separation distance between corrugated aluminum sheath and insulating outer shield before and after the change of buffer layer resistivity caused by moisture were calculated, the influence of moisture on ablation failure was analyzed. The test platform of buffer layer material was built, the properties of two kinds of materials without water immersion and after water immersion drying were tested, including semi-conductive buffer water-blocking tape and semi-conductive buffer tape. The results show that when the moisture content was large, the resistivity of the buffer layer increases, which reduces the requirements of the allowable separation distance of the cable, and was more likely to cause the discharge and ablation of the buffer layer. The water in the buffer layer was removed by drying at 70 °C, with thickness, weight, the water content, elongation at break, breaking strength and volume resistivity can be recovered, which verifies that the heating drying method is feasible for the removal of water from the buffer layer.
Highlights
XLPE cable with buffer layer and corrugated aluminum sheath structure is widely used in underground transmission lines [1-4]
The semiconductive buffer tape is usually composed of one or more layers of semi-conductive nonwoven fabric, and the semi-conductive buffer water-blocking tape is mainly composed of a layer of semi-conductive non-woven fabric, a layer of semi-conductive fluffy cotton, and a layer of polyacrylate expansion powder pasted in the middle
In order to analyze the surface ablation along the axial length of the cable caused by moisture, according to the paper [9], the cable buffer layer and the insulating shielding layer were equivalent to a "composite layer", and an equivalent circuit of high-voltage cable axial ablation along the surface was established, and the requirements for the separation distance between the cable metal sheath and the insulating outer shielding when the cable was discharged was deduced, see (1)
Summary
XLPE cable with buffer layer and corrugated aluminum sheath structure is widely used in underground transmission lines [1-4]. The buffer layer mainly has two structures of semi-conductive buffer tape and semi-conductive buffer water-blocking tape. The semiconductive buffer tape is usually composed of one or more layers of semi-conductive nonwoven fabric, and the semi-conductive buffer water-blocking tape is mainly composed of a layer of semi-conductive non-woven fabric, a layer of semi-conductive fluffy cotton, and a layer of polyacrylate expansion powder pasted in the middle. Due to improper storage or improper laying process of the cable, after the corrugated aluminum sheath is damaged, the humidity inside the layer will change greatly, causing the cable buffer layer ablation failure, so the dry repair method is very important. The research conclusions can provide a basis for the treatment of cable buffer layer after water immersion
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