\({D_s}\) is the GMR of each sub conductor of a four sub conductor bundle conductor and \(d\) is the bundle spacing. What is the GMR of the equivalent single conductor?
1
\(1.09\sqrt[4]{{{D_s} \times {d^3}}}\)
2
\(1.09\sqrt {D_s^3 \times d}\)
3
\(1.09\sqrt[4]{{D_s^3 \times d}}\)
4
\(1.09\sqrt {{D_s} \times {d^3}}\)