Improvements in Lightning Dischargers for Electrical Installations.
Year: 1896

page_text: Date of Application, 29th Jan., 1896
Complete Specification Left, 13th Oct., 1896-Accepted, 28th Nov., 1896
IONA
[Communicated from abroad by SIEMENS & HALSKE, of Berlin, in the German
Empire, Electrical Engineers.]
Improvements in Lightning Dischargers for Electrical Installations.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen Anne's Gate, Westminster,
in the County of Middlesex, Electrical Engineers, do hereby declare the nature of
this invention to be as follows:-
According to this invention a lightning discharger for electrical installations is
constructed as follows. Two metal sockets carried at a certain distance apart by
suitable insulators are connected, the one to the electric circuit to be protected,
and the other to earth; from each socket projects laterally a conducting rod or
bar, such rods being so formed as first to project in a more or less horizontal
direction towards each other, and, when within a short distance of each other, they
are bent up sharply and run vertically more or less parallel with each other
for a certain length at a small distance apart, and they then gradually diverge
from each other at a certain angle, such diverging upper parts being preferably
supported by insulated uprights projecting up from the sockets.
On a lightning discharge into the circuit to be protected taking place, the current
will pass first along the horizontal portion of the rod whose socket is connected to
the circuit, then across the small space intervening between the vertical parts of
the two rods to the second rod, and thence to earth.
The luminous arc which will thus be formed between the two rods will travel
upwards between the parallel and diverging portions of the two rods, until, owing
to the increase of the distance between these, it will eventually be extinguished.
Such upward motion of the arc is due both to the ascending current of heated
air produced by the arc, and to the known tendency of two successive portions of
an electric current, 'which change their direction, to become parallel to each
other.
The metal sockets with their rods are made adjustable on their insulating
supports, so that by such adjustment the small space between the parallel
portions of the rods can be accurately regulated to suit the normal pressure of
the line.
Dated this 29th der of January 1896
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Lightning Dischargers for Electrical Installations.
We SIEMENS BROTHERS & Co. LIMITED of 12, Queen Anne's Gate
Westminster in the County of Middlesex Electrical Engineers do hereby
declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
According to this invention a lightning discharger for electrical installations is

page_text: constructed as follows. Two metal sockets carried at a certain distance apart by
suitable insulators are connected, the one to the electric circuit to be protected, and
the other to earth; from each socket projects laterally a conducting rod or bar, such
rods being so formed as first to project in a more or less horizontal direction
towards each other, and, when within a short distance of each other, they are bent
up, and run vertically more or less parallel with each other for a certain length at
a small distance apart, and they then gradually diverge from each other at a certain
angle, such diverging upper parts being preferably supported by insulated uprights
projecting up from the sockets.
On a lightning discharge into the circuit to be protected taking place, the current
will pass first along the horizontal portion of the rod whose socket is connected to
the circuit, then across the small space intervening between the vertical parts of
the two rods to the second rod, and thence to earth.
The luminous arc which will thus be formed between the two rods will travel
upwards between the parallel and diverging portions of the two rods, until owing to
the increase of the distance between these, it will eventually be extinguished.
Figure 1 of the accompanying drawing shews a front elevation of a lightning
discharger constructed according to the above described invention,
Figures 2 and 3 shew diagrams of the electrical connections and of the action of
the apparatus.
The apparatus consists of two wires or rods D1 D2 of copper or other suitable
metal of peculiar form, which are carried by insulators II and . The wires
are composed of a lower horizontal part which is connected by a bend with a
vertical or nearly vertical length, terminating in a backward sloping length. These
wires are fixed on their insulating supports so that their vertical portions are
parallel with each other, or nearly so, and so close together, that at the narrowest
part of the space between them they are only a few millimetres apart, while
their upper parts diverge from each other to a considerable extent, the extreme
upper ends being from 400 to 800 millimetres apart, according to the tension of the
current that may pass through the circuit to which they are connected.
The lower ends need not necessarily be horizontal but they must recede from each
other to a certain extent; for facility of construction they are bent horizontal.
These horizontal parts are adjustably carried by the metal caps K' K' which are
cemented upon porcelain insulators. In order to afford support to the compara-
tively long upper parts of the wires, they are attached at a¹ a to upright supports
by means of insulating pieces and , so that no current can be transmitted through
the uprights. The lower parts of the wires being adjustable in the sockets K' K³,
the distance between their vertical parts can be adjusted according to the voltage
of the current used in the circuit.
The one wire is connected with the circuit and the other with earth, so that on
any lightning current entering the circuit, it will pass from the wire connected to
the circuit across the gap between the wires and thence to earth. If by such.
discharge a luminous are is formed, this will travel upward along the wires and
will consequently be gradually extended owing to the form of the wires so that after
a short time it will be extinguished, without requiring any additional appliance for
this purpose. The upward travel of the arc is due partly to the ascending current
of heated air produced by the arc, and partly to electrodynainic action, as will be
presently explained.
We are aware that it has before been proposed to construct a lightning
discharger with two electrodes separated by a gap and having such a form that the
gap gradually widens in an upward direction, but in that case the electrodes were
such that an electro-magnet required to be employed in combination with the
electrodes, in order to repel the luminous are so as to cause it to travel upward in
the gradually widening gap.
According to the present invention however no such electro-magent is requisite,
the upward travel of the arc and its ultimate extinction being entirely effected by
the peculiar wire or rod-like shape given to the electrodes D₁ D'.

page_text: With this construction, namely, the electric current being introduced at C
and escaping at D, Figure 2, the luminous arc, whose points of contact, are,.
Bay A and B, must necessarily form the highest part of the course of the
current.
As before stated, the hot air produced by the arc tends to cause it to travel
upward, but in addition to this, the current has an electrodynamic action which
acts in the same direction; in passing in the direction of the arrows, the parts of
the current at a and b form approximately a right angle with each other. In
consequence hereof the part of the current at b will, according to a known law,.
tend to place itself parallel to the part at a, that is to say it will tend to turn upward
from the point A, as indicated by the arrows in Figure 3. In the same way the
part of the current at c will tend to turn upward from the point B, and thus a
further tendency for the arc to rise is produced.
This electrodynamic effect can only be insured when the electrodes are of wire
or rod form, and the current is made to enter and leave them from the lowest
points as in this case the arc must always be formed at the highest part of the
currents course. When on the other hand the electrodes are of plate form as has
been heretofore proposed, the current may flow first upward in the plate and then
downward again before passing across the gap so that in this case not only will!
the above described electrodynamic effect not be such as to tend to cause the
are to travel upward, but the contrary effect would be produced, and consequently
additional means would have to be employed for driving the arc in an upward.
direction.
From the above it will be seen that it is also necessary in order to insure the
electrodynamic effect, to insulate the supports at from the upper parts of the
wires as described.
A lightning discharger constructed according to the above described invention
is peculiarly simple and efficacious; it not only interrupts the luminous arc with
perfect certainty, even at the highest tensions, but also possesses all the properties.
of a good lightning conductor.
It has practically no self-induction, and thus offers no obstacle to the discharge
of atmospheric electricity, and it has no movable parts that require special.
attention.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
A lightning discharger consisting of two conductors insulated from each other
and of linear form, such as wires or rods, such conductors having each a vertical or
nearly vertical part arranged opposite each other at a small distance apart, while
above such vertical part they diverge considerably from each other the parts of
the conductors below the vertical part being connected respectively with the electric
circuit to be protected and with earth, so that a current passing through can only
traverse those parts of the conductors that are situated below the point where the-
luminous are is formed, substantially as described.
Dated this 13th day of October 1896.
ABEL & IMRAY,
Agents for the Applicants..