Influence of structural characteristics on cable ampacity and electrical property for cross-linked polyethylene (XLPE) cable

Abstract

The influence of structural characteristics on the cable ampacity and electrical property of the cross-linked polyethylene (XLPE) cable was presented in this paper. First, four HVAC XLPE cables were selected to detect the structural characteristics by Fourier transform infrared spectroscopy spectrum, gel content, differential scanning calorimetry, and x-ray diffraction measurements. Second, relevant structural parameters were extracted from the measurements. Subsequently, the cable ampacity and electrical property, serving as the macroscopic properties of the cable, were quantified by the measurement of thermal resistivity ρ and breakdown field strength E0. These two parameters reflect the behavior of thermal conduction and electrical conduction, respectively. Finally, the correlation between the structural characteristics and the macroscopic properties was established by linear regression fitting. The results show that the cable ampacity is deeply subjected to the integrity of the XLPE molecular chains and the proportion of secondary crystals within the XLPE. The electrical property is deeply dominated by the crystallinity and lamellar thickness of the primary crystals within the XLPE.

Influence of Combined Electrothermal Aging on Dielectric and Thermal Properties of HVAC XLPE Cable

“…This means the primary crystalline region of spherulites is improved, and the morphological distribution of spherulites becomes more uniform. This phenomenon is ascribed to the enhanced movement in the molecular chains under the thermal effect [10]. With regard to S7-2, even though the R m becomes narrow, the melting absorption peak moves to a lower temperature.…”

“…For S7-2, in Figure 4, compared with S7, varying degrees of decline in both the χ (%) and d of all layers indicate the molecular chains in the crystalline region stack irregularly, converting into the amorphous region. Under repeated melting-recrystallization processes, the newly formed lamellae formed in the cooling process may hinder the molecular chains to stack into thicker lamellae [10]. Especially, the drop in the parameters of the outer insulation is the most significant, which is probably due to the attenuation of the electrothermal effect.…”

“…In Equation (10), it is found that F DEP is proportional to (ε y − ε x ) and ∇E 2 , pointing to the direction of high electric field strength. Ideally, the polar compounds tend to migrate to the inner layer of the insulation under the dielectrophoretic force.…”

“…During the cable operation, several structural changes, such as variations in the quantity of polar compounds, variation in crystallinity, and variation in the cross-linking degree, may change the thermal conductive network within the XLPE. Xu et al found that the thermal parameters of XLPE were deeply subjected to the integrity of the XLPE molecular chains and the proportion of secondary crystals within the XLPE [10]. It was reported [3] that the XLPE thermal parameters were variable due to the change in microstructure and crystal structure.…”