Insulation of Insulators

The Insulation of Insulators

From "The Electrical World"

COMMENCING with the green bottle glass telegraph insulator, of the size of a teacup, about ten years ago, the electric power-transmission engineers have been steadily increasing the size and cost of their high-tension insulators, until now they are using huge glass or porcelain insulators, the size of a cabbage. There has been no help for this visible swelling of the insulator. The little ones simply would not stand the electric stress, as the electric pressure rose by leaps and bounds. Even now the manufacturers would, be ready to risk constructing transformers for 100 kilovolts if the line engineers would accept that pressure. Perhaps the line engineers may do so before long. The question is, What will their insulators then be? Will they be as large as umbrellas? Is long-distance transmission to be limited by the cost of conductors, or by the cost of insulators? A new suggestion is offered from Italy. Instead of placing the high-tension conductor on the top of the insulator, and arranging a series of porcelain petticoats beneath, so that a beetle would have to walk some 60 centimetres [sic] centimeters in the shortest path over the surface from wire to pin, the new insulator hangs the wire underneath the top-most petticoat which is expanded into a relatively thin umbrella. The purpose of the umbrella is only to shelter from rain and not to insulate, so that the umbrella can be made light and inexpensive. The actual insulator below the umbrella is stated to be considerably smaller than would be necessary if the umbrella were removed.