Question: how to calculate gmd and gmr?
Answer: Consider a 3-ph unsymmetrical line with distances b/w phases equal to D1,D2,D3 and solid conductor of radius r . Then GMD=[D1D2D3]^(1/3) and GMR= 0.7788r for the calculation of L , line inductance and GMR =r , for the calculation of C , line Capacitance.