Relationship between Statistical Distributions of Impinging and Stressing Overvoltages in Power Cable Lines

The knowledge of the statistical distribution of the overvoltages stressing the insulation of a cable line is fundamental for the insulation coordination. The estimation of such distributions requires the utilization of complex numerical programs. In this paper a simplified method which takes into account a typical configuration in a power system "overhead line - cable line - transformer" is introduced. The results, although in a general form, highlight that the knowledge of an overvoltage reduction factor, estimated once for all for different cables and power system configurations, can be used to evaluate in an easy way the distribution of the overvoltages stressing the insulation of a cable line starting from the statistical distribution of the overvoltages impinging the cable line.