minimum air clearance in transmission line

[samundra24]

I have this double circuit 220kV line and the formula used for designing minimum air clearance between conductor and earthed part is a = 6.5 inch per 10kV rms; Is this an european or US standard? Thanks in advance

 

[FPelec]

Samundra24,
the clearance depends on the required impulse withstand (switching / lightening) and not on the nominal voltage, which generally dictates the creepage distsnce.
The correlation between standard rated voltages, rated impulse withstand voltages and minimum air clearances are reported in IEC 60071.
For a 220 kV system (Um=245 kV), the highest standard BIL is 1050 kV, leading to a standard conductor-structure clearance distance of 1.9 m.


Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[bacon4life]

That doesn't sound like anything directly out of the USA NESC. Table 235-6 requires 11 inches + 0.2 inches per kV over 50 kV for the distance from conductors to the supporting structure.

Clearances from other objects such as buildings are typically listed as a base value plus 0.4 inches per kV over 22 kV phase to ground (6.92in/10 kV Phase to phase).

 

[samundra24]

Thanks a lot guys.