Investigation on insulation material morphological structure of 110 and 220 kV XLPE retired cables for reusing

Abstract

Most of the 110 and 220 kV cables are in service till the end of life, but part of them would be out of service by refurbishment. This research is focused on evaluating the cable insulation and determining whether the cable can be reused. All the cables used in this research satisfactorily passed the AC voltage and partial discharge tests. Then the fourier transform infrared spectroscopy, thermogravimetry analysis, differential scanning calorimetry, dynamic mechanical analysis, and tensile machine were used to analyze the insulation morphological structure and performance of 20 retired 110 and 220 kV crosslinked polyethylene cables obtained from the Beijing and Zhuhai districts. The results show that the structure parameters which can represent the physical change and the irreversible chemical change of cables have obvious time dependence characteristic. DSC result shows that crystallinity, melting range, and crystallization rate increase slightly with service years. DMA experiment illustrates that the temperature of mechanical loss peak, T γ , shifts to a higher temperature while the mechanical loss increases slightly and temperature dependency of storage modulus increases with service years. The electrical treeing experiment utilized cable operated for 17 years, which is the longest operation year for the samples. Compared with new cable, the cable operated for 17 years has a slight decrease in tree initiation time and an obvious increase in tree propagation time. These experiment data show that the insulation material morphological structure is mainly stable, and the test results are also a contribution to the lifetime expectancy evaluation of the 110 and 220 kV XLPE cable.

Crosslinking Dependence of Direct Current Breakdown Performance for XLPE-PS Composites at Different Temperatures

“…Meanwhile, there is only one loss tangent peak appearing in the temperature range of 10~100 °C for each sample, which has been attributed to the melting process of crystallites for polyethylene [ 25 ]. Compared with pure LDPE, the peak of loss tangent for LDPE/PS shifts to a higher temperature and the corresponding peak value of loss tangent is lower.…”

“…However, in crosslinked composites, with the increase of DCP content, the peak value of loss tangent for crosslinked samples tends to decrease but the peak of loss tangent shifts to a lower temperature. Meanwhile, there is only one loss tangent peak appearing in the temperature range of 10~100 • C for each sample, which has been attributed to the melting process of crystallites for polyethylene [25]. Compared with pure LDPE, the peak of loss tangent for LDPE/PS shifts to a higher temperature and the corresponding peak value of loss tangent is lower.…”

Neural networks and fuzzy logic approaches to predict mechanical properties of XLPE insulation cables under thermal aging

“…The information derived from this overall work helps to understand the degradation mechanisms of the material under service conditions. On the other hand, these investigations are focused on the XLPE insulation morphological structure to know whether this material can be possibly reused [11]. Numerous recent experimental studies have attempted to diagnose the electrical tree in XLPE cables [12][13][14][15].…”

Thermal Effect of Different Laying Modes on Cross-Linked Polyethylene (XLPE) Insulation and a New Estimation on Cable Ampacity

“…In Figure 7c or Figure 8c, the exothermic peaks of the treated specimens move towards a higher temperature and the endothermic peaks move towards a lower temperature, which means the thermal effects disrupt the distribution of crystal structure [28]. Therefore, the ability to crystallize is increased, but the quality is declined relatively.…”