Influence of Oxygen Diffusion on Thermal Ageing of Cross-Linked Polyethylene Cable Insulation

Abstract

Thermal ageing of cross-linked polyethylene (XLPE) cable insulation is an important issue threatening the safe operation of power cables. In this paper, thermal ageing of XLPE was carried out at 160 °C in air for 240 h. The influence of oxygen diffusion on thermal ageing of XLPE was investigated by Ultraviolet–visible spectrophotometer (UV–Vis), tensile testing, and Fourier transformed infrared spectroscopy (FTIR). It was observed that the degradation degree not only depended on ageing time but also on sample positions. The thermally aged samples were more oxidized in the surface region, presented a darker color, more carbon atoms appeared in the conjugate cluster, had smaller elongation at break and tensile strength, and a larger carbonyl index. As ageing time increased, the non-uniform oxidation of the XLPE samples became more prominent. The degree of non-uniform oxidation caused by oxygen diffusion was quantitatively studied by first order oxidation kinetic. The calculated results demonstrated that carbonyl index measured by FTIR was more sensitive to non-uniform oxidation with a shape parameter in the range of 1–2. The result shown in this paper is helpful for interpreting and predicting the non-uniform ageing behavior of high voltage XLPE cables.

Influence of Thermal Aging on the Combustion Characteristics of Cables in Nuclear Power Plants

“…Studies on the aging properties and mechanisms of cables consisting of polymeric materials have been conducted steadily in recent years [8][9][10]. Chi et al [1] and Zhang et al [11] reported on the changes of the properties of cable insulation with thermal aging including the chemical, thermal, dielectric and mechanical properties. Sarac et al [12] and Min et al [13] studied the influence of gamma ray irradiation on the mechanical and dielectric characteristics of polymers used in NPPs.…”

Research on Lifespan Prediction of Cross-Linked Polyethylene Material for XLPE Cables

“…(3) Moreover, as results in the previous research have shown, there is a correlation between tensile strength and the physicochemical properties of XLPE cables [14]. The reasons for the changing law of tensile strength and breaking elongation are that the crystallinity of samples decreases with the increase in aging time, as mentioned in Section 2.1.2, which, in turn, results in a more chaotic arrangement of molecules and more frequent molecular movements.…”

“…Tensile testing is one of the widely accepted methods for evaluating the aging performance of XLPE cables. On the basis of test results, some scholars propose to use two parameters, tensile strength and elongation, to characterize the aging degree of XLPE cables [14]. In this paper, the changing law of tensile strength and breaking elongation of samples after each aging process was assessed by tensile testing.…”

Invariant electrical conductivity upon thermal ageing of a crosslinked copolymer blend for high voltage insulation

“…5,6 It is of paramount importance that the excellent dielectric properties of click chemistry-cured copolymer blends do not deteriorate with time. Ageing of polyethylene-based insulation materials can introduce chemical defects as well as structural changes, which can negatively affect their dielectric and thermomechanical properties [22][23][24][25][26] and hence may cause electrical treeing as well as a decrease in the dielectric breakdown strength. [27][28][29][30] Here, we study how long-term ageing at 90 1C -the currently highest HVDC cable operating temperature -for up to 2500 h influences the dielectric and thermo-mechanical properties of a cured copolymer blend comprising p(E-stat-GMA) and p(E-stat-AA).…”

“…5,6 It is of paramount importance that the excellent dielectric properties of click chemistry-cured copolymer blends do not deteriorate with time. Ageing of polyethylene-based insulation materials can introduce chemical defects as well as structural changes, which can negatively affect their dielectric and thermo-mechanical properties 22–26 and hence may cause electrical treeing as well as a decrease in the dielectric breakdown strength. 27–30…”