Improvements in Protecting Telegraph, Telephone, Electric Lighting, and other Installations and Instruments from Damage by Lightning or other High Tension Electric Currents, and in Apparatus therefor.
Year: 1889

page_text: Date of Application, 5th Apr., 1889
Complete Specification Left, 6th Jan., 1890--Accepted, 15th Feb., 1890
PROVISIONAL SPECIFICATION.
Improvements in Protecting Telegraph, Telephone, Electric Lighting,
and other Installations and Instruments from Damage by
Lightning or other High Tension Electric Currents, and in
Apparatus therefor.
J, OLIVER JOSEPH LODGE D.Sc. F.R.S. of University College, Liverpool in the
County of Lancaster, Professor of Physics, do hereby declare the nature of this
invention to be as follows:-
As the result of a long course of experiments on the conditions and phenomena of
high tension discharges, I have arrived at a method of reliably protecting any kind of
apparatus from the effects of lightning or any other high tension currents, however
generated, which are not intended to enter it.
My invention consists of a number of air-gaps, connected to each other by coils or
lengths of wire or other conductor, solid or liquid, which oppose the current either by
self-induction or electromagnetic inertia, or by resistance proper, and of either
adjustable or fixed width. The apparatus to be protected, whether it be lamps, or
telephones, or telegraphic instruments, or galvanometers, or meters or any other kind
of electrical apparatus, is connected to the last air-gap of the series; the line wire
or exposed leads or other wires into which it is feared that lightning or high
tension currents may possibly come, are connected to the first air-gap of the
series.
The action of the arrangement is as follows:-
The ordinary currents, which it is intended to transmit through the apparatus to
be protected, traverse the connecting wires or self-induction coils and do not jump
any of the air-gaps. But lightning or any other foreign and violent currents which
may accidentally have got into the leads will jump one or more of the air-gaps and
be thus diverted from the instruments or lamps to be protected.
Thus, suppose the air-gaps are all of equal width they are arranged so that the
greater portion of a violent discharge will jump the first: a certain fraction, say a
tenth, will jump the second another fraction, say a tenth of this again, will jump
the third and so on: the amount finally permitted to go through the protected
instrument being thus reduced to any desired amount.
It may be well to set the air-gaps of different widths: for instance, the first wider
than the second, the second wider than the third, etcetera and capable of easy replace-
ment in case of damage by a flash. It may also be well to vary the connecting
coils, using thicker wire for some and thinner for others. All this and other such
reasonable latitude I claim to be allowed.
For electric light purposes, the whole arrangement may have to be more massive.
than for telegraphic or telephonic purposes, and fusible cut-outs of any ordinary
description may be introduced at any point or points to prevent damage by reason
of the spark, when it occurs, striking an arc at any air-gap.
By "air-gaps," I mean a small space between two knobs, plates, points, cylinders;
or other metallic or conducting surfaces, and in calling it an air-gap. I do not mean
to exclude a liquid being used instead of air, nor do I insist on air to the exclusion of
any other gas; vacuum may be used in the last of the series.
The connecting conductors will be usually so devised as to oppose the current more
by self-induction than by resistance proper; but I claim any kind of impediment as
permissible, using the one which obstructs the desired currents least and the undesired
most.
Lightning protectors consisting of an air-gap hetween plates are already well
known and in uso; but experience has shown that they often fail to protect!

page_text: and by experiment I have proved that they cannot possibly protect completely.
They are, moreover, usually not connected up to the circuit in the best
manner.
By arranging a series of them, however, connecting them with wires having some
amount of self-induction-which may be different for different purposes and by
connecting the line and earth wires or the two line wires or the leads generally to
one end, and the instrument to be protected by one or both of its termini to the other
end of the series, with a full knowledge of the behaviour, and connections necessary,
I show, both theoretically and experimentally, that any desired amount of protection
can be obtained up to theoretical perfection.
In fine, by my invention, I produce for the first time, such a combination of air-
gaps and conductors as will reduce the fraction of high tension disturbance passing
by an undesired route to any desired degree of smallness, and make it practically
infinitesimal.
The accompanying drawing shows one arrangement for achieving the purpose of
my specification.
In this-
A B are the terminals to be inserted in the leads, or between line wire and earth,
etcetera.
CD are the terminals to be connected to the instrument or thing requiring
protection.
The connecting coils may be of any shape, or they may be straight wires or carbon
rods or mercury tubes or any conducting arrangement whatever.
The knobs or points may be mounted in any convenient way, and may be either
fixed or adjustable. For many purposes only three terminals are required or at
intermediate stations a double instrument, each half with three terminals.
Dated this 4th day of April 1889.
WM. F. THOMPSON & CO.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Protecting Telegraph, Telephone, Electric Lighting,
and other Installations and Instruments from Damage by
Lightning or other High Tension Electric Currents, and in
Apparatus therefor.
I, OLIVER JOSEPH LODGE, D.Sc. F.R.S. of University College, Liverpool in the
County of Lancaster, Professor of Physics, 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 :-
As the result of a long course of experiments on the conditions and phenomena
of high tension discharges, I have arrived at a method of reliably protecting any
kind of apparatus from the effects of lightning or any other high tension currents,
however generated, which are not intended to enter it.
In the apparatus at present in use, a short lead is brought from the line wire to an
air-gap, electrically connected on the other side with the earth, the resistance of
this course being intended to be made so much less for high tension electricity
than the path through the instruments, that the greater part of the high tensional
charge shall be shunted to earth.
My invention consists in the use of a number of air-gaps or insulating spaces,
connected to each other by coils or lengths of wire or other conductor, solid or
liquid, which oppose the current rather by self-induction or electromagnetic inertia,
than by resistance proper. The gaps are of either adjustable or fixed width and the
line current has to go past all of the air-gaps while the momentary high tensional
currents are shunted through the gaps. The apparatus to be protected, whether it be
lamps, or inside wires, or underground or submarine cables, telephones, telegraphic

page_text: connected to the first air-gap of the series.
Referring to the drawings:
:-
Figure 1 shows a simple form of carrying my invention into effect with adjustable
air-gaps.
Figure 2 a simple arrangement for lightning switch, specially useful at the junction
of overhead and underground or submarine lines, or other position where there are
covered wires or cables to protect.
Figure 3 an arrangement useful at an intermediate telegraph station having no
earth connection.
Figure 4 shows the invention utilising existing lightning protectors, such as plates
or tubular protectors or points in a vacuum.
Like letters refer to like parts in all these.
Referring first to Figure 1:
A and B are the terminals inserted in the leads, or A is connected with the line
wire and B with earth; C D are terminals connected with the instrument to be
protected, or C with the instrument and D with the earth, or with the instrument
and D left insulated as desired. E' E', etcetera, are air-gaps or insulating spaces.
These can be formed with one or more points, or rounded ends, as shown; or with
knobs or plates or vacuum tubes or other suitable device G₁ G³, etcetera, are self-
induction coils, consisting, for instance, of gutta percha covered wire coiled up on
bobbins.
The action of the arrangement is as follows:-
The ordinary currents, which it is intended to transmit through the apparatus
to be protected, traverse the connecting wires or self-induction coils G' G³, etcetera,
and do not jump any of the air-gaps. But lightning or any other foreign and violent
currents which inay accidentally have got into the leads will jump one or more of the
series of air-gaps, and be thus diverted from the instruments or lamps to be
protected.
Thus, the insulating spaces or air gaps may be arranged so that the greater portion
of a violent discharge will jump the first, E'; a certain fraction, say a tenth of the
remainder will jump the second, E'; another fraction, say a tenth of this again, will
jump the third E³, and so on; the amount finally permitted to go through the
protected instrument being thus reduced to any desired amount.
It may be well to set the air-gaps or insulating spaces of different widths; for
instance, the first having broad rounded ends wider apart than the second, exposing
larger surface and capable of easy examination and replacement (as by binding
screw h) in case of damage by a Hash; the second having small rounded ends or
points close together, and capable of minute adjustment by screwing up as shown
(with lock-nuts), or equivalent device; the third still closer and finer, etcetera. It may
also be well to vary the connecting coils, using thicker and more highly insulated wire
for the earlier coils, and thinner for the later, as shown.
Figure 2 shows a variation useful for protecting the insulation of covered wires or
cables in which the exposed line is attached to terminal A, and the protected one to C.
B is connected to earth.
The first, F1, is preferably a knob, plate or rounded end, as shown, and of stout
conducting material, the second and subsequent ones, F, F, etcetera, can be knobs
or points, preferably the latter, and can be adjusted nearer the central knob F'
thau Fis.
In place of self-induction coils, straight wires, carbon rods, mercury tubes, or
other conducting arrangement giving sufficient impedance or resistance can be used.
Also each of the knobs or points F2, F, F, F³, can be connected directly with
the earth, instead of with each other.
In Figure 3, A is connected to the up line wire, B to the down line wire,
C and D to all the instruments in the station, and E to the earth.

page_text: The conductor K, connected with ‘the earth, is placed between the entrance and
exit wires, each of which is provided with a series of knobs, plates, or points; (with
self-induction coils between) forming air-gaps with this conductor.
In this
Figure 4 shows an arrangement whereby existing protectors can be coupled up
with resistances and other protectors in accordance with my invention.
Figure and in Figure 1, like letters relate to equivalent parts. F and F¹, in this
drawing, however, are the ordinary plate lightning protectors; F³ and F, the well
known tubular lightning protector in which a rod F4 is closely surrounded but
insulated from a cylinder F3, the one being on one line, the other, on the other line.
Either the rod or the cylinder is usually studded with points almost; but not actually;
in contact with the other, being separated therefrom by a thin stratum of air;a film
of mica, or of other insulating material. F³ F and F F8 are lightning protecting
devices on the same plan as those in Figure 1.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed,. 1 declare that. what I
claim is
1. The method of protecting instruments or other electrical appliances from lightning
or other high tensional currents such for instance as may be received from electric
lighting leads, which consists in placing a series of two or more air-gaps or other
insulating spaces between the protected apparatus and the main line; whereby, after
the first air-gap has shunted most of the high tension electricity, the second'shunts
most of the remainder, and so on, substantially as described.
2. The method of protecting from lightning and high tension electricity generally,
which consists in offering self-induction obstruction on the one hand, and di-electric
weakness on the other, to the lightning; and air-resistance obstruction on the one
hand, and thick wire conduction on the other, to the useful current; each offer being
repeated several times, substantially as described.
3. The apparatus for protecting instruments and line wires from lightning or other
high tensional electricity, which consists in a series of narrow air or other insulating
gaps on the line wire with coiled resistances or impedances between, substantially as
described.
4. The addition to an existing lightning protecting device on the air gap principle
of one or more extra devices of the like nature joined up "in parallel
with it,
whereby the residual high tension electric fluid not taken off by the original device is
in great part shunted by the second, and the residue of the remainder in great part by
the third, and so on.
Dated this 4th day. T
1000
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, and London, Patent Agents.