3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 insulation co-ordination: The selection of the dielectric strength of equipment in
relation to the voltages which can appear on the system for which the equipment is
intended and taking into account the service environment and the characteristics of the
available protective devices. [IEV 604-03-08, modified]
NOTE - By 'dielectric strength' of the equipment, is meant here its rated or its standard insulation level
as defined in 3.32 and 3.33 respectively.
3.2 external insulation: The distances in atmospheric air, and the surfaces in contact
with atmospheric air of solid insulation of the equipment which are subject to dielectric
stresses and to the effects of atmospheric and other external conditions, such as pollution,
humidity, vermin, etc. [IEV 604-03-02, modified]
NOTE - External insulation is either weather-profecfed or non-weather-protected. designed to operate
inside or outside closed shelters respectively.
3.3 internal insulation: The internal solid, liquid, or gaseous parts of the insulation of
equipment which are protected from the effects of atmospheric and other external
conditions. [IEV 604-03-031
3.4 self-restoring insulation: Insulation which completely recovers its insulating
properties after a disruptive discharge. [IEV 604-03-041