1. Geometric sizing

1.1 Isolation distances

An overhead line is characterized by its phase-to-phase voltage.

• This voltage defines the insulation of the line, which is obtained by maintaining, in all circumstances, air gaps of sufficient length between the conductors and objects at earth potential, and between the conductors themselves.

  These intervals are permanently subjected to line voltage, but they are also subject to exceptional stresses, the most annoying of which are the surges caused by lightning ...