The direct method of calculation of capacitance of conductors

The capacitance, or electrostatic capacity, of conductors of various shapes has practically always been calculated by the “inverse method” of first assuming certain charges of electricity and from them calculating equi-potential lines and surfaces, which, in the more fortunate cases, agreed exactly with the shapes of the conductors. In other cases, such as that of a three-conductor sheathed cable, the agreement, and therefore the calculated capacitance, were only approximate. For multi-conductor cables with round conductors, a “direct method” of calculation of capacitance is described in this paper, which uses the exact shape of the round conductors, and which gives accurate expressions for the irregular distribution of electricity on the conductors, and for the value of the capacitance. Formulas and examples are given for the following cases: 1. Finite wire and infinitesimal wire. 2. Single-phase overhead line. 3. Two conductors and sheath. 4. Three conductors and sheath.