The paper deals with a transmission line structure, whose outer conductor consists of two parallel semi-infinite conducting planes forming into a semicircular edge at one end and the inner conductor is a right circular cylinder. The space between the two conductors is filled by a uniform dielectric material. The self-capacitance between the two conductors has been obtained for various structural configurations. About 300 cases, which cover practically all important configurations, have been analysed and results are presented graphically as well as closed form formulae. Solutions for a particular case have also been checked against some experimentally observed values.