This Standard provides guidance for the calculation of electrical distances between live and earthed parts required to prevent air-gap breakdown which may endanger members of the public who legitimately come close to live parts. It is applicable only to overhead lines designed to operate at more than 45 kV phase-to-phase a.c. It deals with the electrical component of distances between conductors and movable objects - vehicles on the ground, vessels on water, persons on top of objects or on the ground, wildlife on the ground (but not airborne), etc. This standard does not deal with the following public and worker safety aspects: ---- This standard does not g