Destructive voltage-rises on low-tension busbars. A suggestion

The paper treats of a class of low-tension a.c. distribution system using bare conductors for electrical flexibility. A formula for self-inductance is calculated, from which it is shown that, given certain limiting conditions, the conductors must be unusually closely spaced. In practice, such a system is subject to frequent and apparently inexplicable flash-overs. Investigating this problem, the paper analyses mathematically the effect, on a steep-fronted voltage surge, of regularly localized insulator capacitance. The wave-complex arising at each reflection point is found to be divisible into groups, provisionally termed ¿sub-transients,¿ which are expressible by gamma functions. It is concluded that the insulators have a magnifying effect on voltage surges, which thereby easily attain destructive values. The researches of Steinmetz confirm the tendency for the phenomenon to persist, in systems of the type considered. Insulating barriers are suggested as being a proven, if expensive, remedy.