The capacitance of an a.c. system can be of great importance when designing the protection equipment for the busbars and associated electrical plant. Capacitances for several configurations of busbars are as follows, where
permittivity E = E0Er
where
Er = relative permittivity of the material.
Isolated twin line
Line above a conducting earth
Twin line above a conducting earth
Isolated three-phase line with transposition
Concentric cylinders
