Fig. 215. COMB OR TOOTHED LIGHTNING ARRESTER.
Fig. 216. FILM OR PLATE LIGHTNING ARRESTER.
Lightning Arrester, Counter-electro-motive Force.
An invention of Prof. Elihu Thompson. A lightning arrester in which the
lightning discharge sets up a counter-electro-motive force opposed to
its own. This it does by an induction coil. If a discharge to earth
takes place it selects the primary of the coil as it has low
self-induction. In its discharge it induces in the secondary a reverse
electro-motive force which protects the line.
Lightning Arrester Plates.
The toothed plates nearly in contact, tooth for tooth, or the flat
plates of a film lightning arrester, which constitute a lightning
arrester. Some advocate restricting the term to the plate connected to
the line.
Lightning Arrester, Vacuum.
A glass tube, almost completely exhausted, into which the line wire is
fused, while a wire leading to an earth connection has its end fused in
also.
A high tension discharge, such as that of lightning, goes to earth
across the partial vacuum in preference to going through the line, which
by its capacity and self-induction opposes the passage through it of a
lightning discharge.
It is especially adapted for underground and submarine lines.