Overhead lines-loading and strength: the probabilistic approach viewed internationally

Recently, several countries have published documents related to the probabilistic design of overhead lines, and almost concurrently the International Electrotechnical commission (IEC) has issued four Reports in the 826 series, representing an international consensus of opinion on this subject. The underlying principles are that neither the loads applied to an overhead line nor the strengths of the components can be described by single values, and a statistical knowledge of the loads and of the strengths is required. Any attempt at preparing a loading specification without a parallel strength specification would defeat the new approach, which permits the evaluation of relative reliabilities.