How is dielectric strength defined in cable technology?

Dielectric strength represents a material's capacity to withstand electrical stress without breakdown, quantified as the maximum voltage per unit thickness required to cause insulator failure. This fundamental property determines insulation performance in cable systems, with higher values indicating superior electrical resistance capabilities.

Testing follows standardized procedures outlined in IEC 60243, involving sample placement between electrodes with voltage gradually increased until breakdown occurs—typically through puncture or material decomposition. Specimens measuring 0.8–3.2mm thick undergo evaluation, with samples exceeding 2mm often submerged in oil to prevent surface flashover from prematurely terminating tests. The resulting dielectric strength value is calculated by dividing the breakdown voltage by the material thickness.

Engineering plastics commonly utilized in cable insulation demonstrate dielectric strength ranging from 10–30 kV/mm. Notable examples include Low Density Polyethylene (LDPE) at 27 kV/mm, Polypropylene (PP) at 22 kV/mm, and Polyvinylchloride (PVC) at 14 kV/mm, with these metrics guiding material selection for specific voltage and environmental requirements in cable design.