BS IEC 61865:2001

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms, definitions and symbols
   3.1 Definitions
   3.2 Symbols
4 Approach used to derive the electrical distance
5 Overvoltages
   5.1 Classification of overvoltages
   5.2 Temporary overvoltages
   5.3 Slow-front overvoltages
   5.4 Fast-front overvoltages
6 Required withstand voltage of the air gap
   6.1 General
   6.2 Calculation of the required withstand voltage
7 Calculation of the distance associated with the
   overvoltages
Annex A (informative) Relationship between U(50)
        and the gap length, d
Annex B (informative) Example of the calculation of
        the electrical component
Bibliography

Gives 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. Applicable only to overhead lines designed to operate at more than 45 kV phase-to-phase a.c. It manages 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.