standards / manuals / guidelines for small hydro development - AHEC

Between phases or Phase/pole to earthpoles36 kV 356 mm 222 mm12 kV 127 mm 76 mmIn indoor kiosks in power stations and main receiving stations, the busbar andconnections should also be taped but the fact of taping should however, be taken intoconsideration in deciding the clearances. In addition indoor kiosks etc. should besubjected to a flashover test at works to prove that clearances are adequate so as toprevent flashovers during surge conditions.2.4.5 Standard Bay Widths (in meters) as TNEB Practices66 kV - 733kV - 4.622 kV - 3.811 kV - 3.52.5 Insulators – Creepage DistanceProvision of adequate insulation in a substation is of primary importance from the pointof view of reliability of supply and safety of personnel. However, the station designshould be so evolved that the quantity of isolators required is minimum commensuratewith the expected security of supply. An important consideration in determining theinsulation in a sub-station, particularly if it is located near sea or a thermal powergenerating station or an industrial plant is the level of pollution. As a first step to combatthis problem, special insulators with higher creepage distance should be used.The creepage distances for the different pollution levels are provided according to table2.8.Table 2.8: Creepage distance for different pollution levelsPollution LevelCreepage distance (mm/kV ofhighest system voltage)Recommendedfor adoptedLight 16 25 x highestMedium 20system voltageHeavy 25i.e. 1813 mmVery heavy 31for 72.5 kVFor determining the creepage distance requirement, the highest line-to-line voltage of thesystem forms the basis.1-12