Majority of electrical substations will be air insulated type. All the electrical equipment live parts will be exposed .All the electrical equipment in the substation shall be arranged in such a manner to ensure the clearance space between the live parts and other equipment of the substation (grounded or ungrounded). Adequate clearances should be provided for safety of the operating and maintenance personnel and also to prevent any conducting path between the phases.
Safety clearances associated with different voltage levels are given in the table below.
- Phase to phase clearance is the minimum clearance required to be provided between the live parts of different phases or is the minimum clearance between the same phases
- Phase to earth clearance is the minimum clearance required to be provided between the live parts of the system and earth structures
- Sectional clearance is the distance between the live parts of the phases and the terminals of the work section. This limits of work section or maintenance section may be a platform or ground on which operation personnel can carryout his task safely
· Ground clearance is the vertical clearance between the live parts of the equipment and the earth surface