The geometric mean radius of the 400 kV, 200 km long transmission line is 21 mm. The roughness factor of its conductor is 0.87. The geometric mean length between phases is 11 m. The air pressure along the line is 700 mmHg and the temperature is 23 C. a) Calculate the voltage at which ionization begins and the corona voltage. b) Find the corona loss for operating voltage using the peek formula. c) Find the corona loss for a 10% increase in operating voltage.