The Correlation and Balance of Material Properties for DC Cable Insulation at Design Field

The innovation of materials with disruptive properties can be efficiently guided by improved physical understanding of material design principles. The design of a polymeric insulation depends on the desired requirements of the specific application, which, in the case of DC cable insulation, can be stated in terms of the following properties: controlled electrical conductivity, low space charge accumulation and high breakdown strength. Full characterization and detailed understanding of these properties as well as their correlation and balance may bring the ability to engineer needed dielectric properties for using as DC cable insulation. The aim of this paper is to identify the optimal DC insulation design space and to develop a formalism of the correlation between the conductivity and space charge, guided by a relatively simple model based on two physical parameters, activation energy (<inline-formula> <tex-math notation="LaTeX">$\xi$ </tex-math></inline-formula>) and mean trap separation (<inline-formula> <tex-math notation="LaTeX">$\lambda$ </tex-math></inline-formula>). With respect to implications for practical material design, the study demonstrates that a polymer material with activation energies in the range of 0.4 to 0.5 eV with relatively high trap density (<inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>) (<inline-formula> <tex-math notation="LaTeX">$N= \lambda ^{-3}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$\lambda =1$ </tex-math></inline-formula> nm, <inline-formula> <tex-math notation="LaTeX">$N=1\text {E}+27\,\,\text {m}^{-3}$ </tex-math></inline-formula>) can be suitable for HVDC cable insulation.