High voltage cables with extruded insulationߞStatistical controls and reliability evaluation

Design characteristics of high voltage cables with extruded insulation can be established by use of the failure probability distribution of the insulation materials involved The evaluation of the distribution parameters is discussed and the validity of the theory for a wide range o f cable dimensions is proved. Also discussed is the importance that, in order to ensure cable reliability, these parameters should remain constant for time intervals ranging from a few minutes to many years. Finally it is shown by analysis of the relative influence of the distribution parameters how it is possible to establish the insulation requirements for the design of 60 to 138 kV cables.