What is the recommended creepage distance for sub-station insulators in clean areas?
1
\(16 \mathrm{~mm} / \mathrm{kV}\)
2
\(20 \mathrm{~mm} / \mathrm{kV}\)
3
\(22 \mathrm{~mm} / \mathrm{kV}\)
4
\(25 \mathrm{~mm} / \mathrm{kV}\)
5
\(30 \mathrm{~mm} / \mathrm{kV}\)