An Improved Method of and Apparatus for Protecting Dynamo- electric Generators and other Apparatus from the Effects of Lightning.
Year: 1891

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by THE THOMSON-HOUSTON INTERNATIONAL
ELECTRIC COMPANY, of 620, Atlantic Avenue, Boston, Massachusetts,
United States of America.]
An Improved Method of and Apparatus for Protecting Dynamo-
electric Generators and other Apparatus from the Effects of
Lightning.
1, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, 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 :-
My present invention is designed to supplement the action of the ordinary
lightning arrester in protecting a dynamo-electric generator, motor or other
apparatus included in an electric circuit from lightning or other high potential
discharges.
To this end the communicators have devised a new method and apparatus for the
above purpose, which consists, briefly, in causing the lightning discharge, when
passing to earth, to generate by induction a counter-electromotive force opposing
the passage of the discharge through the generator, or other apparatus to be
protected, and thus effectually prevent injury thereto.
The accompanying drawing illustrates diagrammatically various forms of my
invention, in which:
Figures 12 and 3 illustrate respectively modifications identical in principle, but
differing in matters of detail, as will be hereinafter explained.
In these views L represents a line circuit, in which is located a dynamo electric
generator D supplying current to the circuit; but while this dynamo is selected
herein for purposes of illustration, it will be understood that it may be replaced by
other forms of apparatus which are to be protected from lightning.
The line wire L is connected to ground at one end of the circuit, and at the
other end, there are two conducting paths to ground, one the ordinary lightning
discharge path, shunting the generator by way of arrester plates P and the ground
plate E, and including also a few turns of wire C', while the second comprises a
corresponding coil C which may be interior or exterior to the coil C¹ and passes
through the generator to ground. The two coils C, C' are arranged in inductive
relation to one another, but are well insulated. Their effect is to cause a lightning
or other static discharge when passing directly to ground through the path of
comparatively low self-induction and coil C to generate an opposing counter-
electromotive force from the generator to the line in the other coil C, and in this.
way to balance the inductive effects.
In Figure 2 the coil C in the direct lightning discharge path is, in effect, an
exterior casing, or basket work of metal which surrounds the dynamo, while the
windings of the machine itself serve as the second coil, corresponding to C in
Figure 1. The connection from the line L and earth plate E to the casing C may
be either made directly, or through a series of insulated plates P, P, which are
separated by a small interval enabling a static discharge to pass throughout the
series. In case a direct connection to the casing is made, an arc-rupturing lightning
arrester would be interposed in the ground connection between the cage and earth
plate E, but if the insulated plates P, P¹ be used an arc will not be maintained
between individual plates on account of the number of spark gaps in series.
In this form of my invention the passage of an inductive discharge from the line
by way of the cage C, shunting the generator, will set up a counter induction effect

page_text: in the windings of the dynamo itself, and those two will oppose one another so that
the dynamo will be thoroughly protected.
In Figure 3 a still further modification of the invention is shown, in which the
dynamo is connected to line through the two coils in series, and here it is the
interior coil C, which is connected directly to the dynamo and is shunted by
the ground connection through the coil C, arrester plates P and earth plate E.
The lightning will be more apt to traverse the coil C, as this is the exterior one,
and pass directly to earth, while in doing so it generates a counter-electromotive
force in the coil C, protecting the generator D as before.
In this modification, a second set of arrester plates Pare provided which form
a shunt for the coil C around the dynamo, and whose object is to cut off from the
dynamo any excessive induced discharge, which might be generated in the coil C¹ by
a vigorous discharge to earth through the direct conducting path.
In this way a
static discharge towards the dynamo, in opposition to the original discharge, when
too great will pass to ground through the arrester plates P¹.
No definite instructions need be given for proportioning the windings C, C₁. In
some cases the number of turns would be the same, in others the coil in the dynamo
branch would have a few more turns than the other and good results can sometimes
be obtained with double the number of turns so as to give an excess of counter-
electromotive force in this branch and obviate the possibility of any current
reaching the dynamo or other protected apparatus. The number of turns will of
course be understood to vary according to the size, character and relation of the
coils one to the other and can be determined by experiment for each case.
In any case, however, the two windings should be so related that a discharge
coming from the line and passing through the ground winding, induces in the line
winding an electromotive force opposite to that which the discharge itself produces
therein. This condition is fulfilled by winding the coils or choosing the connections
so that the two windings pass around the coils in the same direction, starting in
each case from that end which is nearer the line. These windings may be designated
as electro-magnetic induction devices.
As indicated above, this invention may be worked out in a number of modified
ways; but as I am the first, so far as I know, to cause the discharge in passing
through the ground branch to generate a counter-electromotive force in the main
line and to utilize the counter-electromotive force as an additional precaution
against injury to the apparatus protected by the lightning arrester my intention is
to claim the same broadly, irrespective of modifications in the specific ways the
invention may be used.
Thus while I have attained the desired result by means of electro-magnetic
induction it is obvious that my invention is not limited to this kind of induction,
but may be carried out by means of well known equivalents therefor.
My system of protection is morcover applicable to all systems of distribution of
electric currents whether direct or alternating, and the dynamo D may therefore be
considered as either a direct, or an alternating current generator.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me
by my foreign correspondents, I declare that what I claim is :-
First. The method herein described of protecting dynamo electric generators,
motors, or other apparatus included in electric circuit from the effects of lightning
or other high potential discharges, which consists in diverting the discharge
to earth and causing such diverted discharge to generate a counter-clectromotive
force in the circuit of the generator or other apparatus opposing the passage of the
discharge through the same.
Second. The combination of a dynamo electric generator motor, or other
apparatus included in an electric circuit and the usual shunt to ground around the
same for affording protection from lightning or other high potential discharges;
with the counter-inductive generator of electromotive force excited by the passage

page_text: of the discharge in the ground shunt and acting to oppose the passage of the
discharge through the dynamo or other apparatus to be protected.
Third. The combination with a line circuit of two conducting paths therefrom to
ground, one shunting and the other including a dynamo electric generator, motor
or other apparatus to be protected, and so arranged in inductive relation to one
another that the passage of the discharge through the path leading directly to
ground generates a counter-electromotive force in the path through the dynamo
opposing the passage of the discharge in said second path.
Fourth. The combination with a dynamo electric generator or other apparatus
included in an electric circuit, of a lightning discharge path from the line circuit to
ground shunting said generator, and coils respectively in such line circuit and the
shunt to ground, and arranged in inductive relation to one another, so that the
passage of the discharge through the ground shunt coils generates a counter-
electromotive force in the line circuit coils opposing the passage of the discharge
through the generator or other apparatus to be protected.
Fifth. The combination with a dynamo electric generator or other apparatus to
be protected and a lightning discharge path shunting the same, of the coils
respectively in the circuit of the dynamo and the discharge path, and arranged in
inductive relation to one another so that on the passage of a discharge through the
discharge path coil, a counter-electromotive force is generated in the other coil
opposing the passage of the discharge through the apparatus to be protected, and a
second lightning discharge path forming a shunt for the coil in which the opposing
counter-electromotive force is generated.
Dated this 23rd day of June 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.