Nontransversal electrostatic fields in cable models

Potentials of electrostatic fields in models of straight shielded cables are often assumed to be cylindrical (i.e., independent of the coordinate in axial direction of the cable). We give a rigorous motivation for this assumption. From the boundary conditions at the cable ends of shielded cables there result deviations of the potential from the cylindrical potential in the proximity of the cable ends. Such deviations were firstly introduced as residual potentials by us at ISTET '03. Here, we present new optimized estimations for residual potentials. To a nontrivial residual potential, there corresponds nontransversal electrostatic field strength, denoted as residual field strength. For the first time, we discuss an estimation of the residual field strength along the conductors of a cable model in this paper.