Electric Cables for High Tension Currents.
Year: 1898

page_text: Date of Application, 21st Nov., 1898
Complete Specification Left, 1st Aug., 1899-Accepted, 16th Sept., 1899
PROVISIONAL SPECIFICATION.
Electric Cables for High Tension Currents.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23, Southampton Buildings, in the
County of London, Patent Agent, do hereby declare the nature of this invention
(a communication to me from La Société Française des Câbles Electriques,
Système Berthoud, Borel and Cie., of 11, Chemin Pré-Gaudry, Lyons, in the
Republic of France), to be as follows:-
Subterranean electric cables are generally constituted of one or several copper
cords insulated from the earth as also from each other by the interposition of
layers or coats of materials which are bad conductors of electricity..
Electric cables, for currents of high tension, 2000 volts and upwards, hitherto
differ only from cables for low tension current in the quality of the insulating
material employed, and in the thickness of the insulating, layers or coats separat-
ing the conductors from each other and from the earth.
The present improvement has for its object to increase the resistance of these
insulating layers or coats, by a special arrangement of the electric cords or
conductors which are enclosed therein...
The conducting cords (the cores, the conductors) of subterranean electric
cables, are generally composed of a certain number of cylindrical strands of
naked copper wire, twisted together.
The number and diameter of these strands varying with the conducting
section it is desired to obtain.
Experience has brought the communicators to constitute the improved con-
ducting cords for high tension currents in the manner represented at Fig. 1
of the accompanying drawing. In the centre, as usual, are placed twisted
together, a certain number of strands A of naked copper forming a certain
fraction of the total required section.
to
On this central naked copper cord A, is placed a concentric layer or coat B,
of copper strands, covered with an insulating layer or coat which insulates them
from each other as also from the central conducting cord, the sum of the metallic
sections of this peripheral layer or coat will complete the section the conductor
is required to have."
The conducting cords thus formed are placed in the usual manner and in con-
venient number in their envelope furnished with insulating material, as is
shown, by way of example, at Fig. 2 in section.
A given thickness of insulating material with these conducting cords with
peripheral insulated strands, resists double or triple tensions, according to the
diameters of the peripheral strands: employed, as compared with those which it
resists with ordinary conducting cords of naked strands.
These new subterranean electric cables may have one or several twisted con-
ductors, or several concentric conductors which may have the entire or only
part of their conducting strands, insulated from each other, and particularly
those of the peripheral layer or coat. The insulating material separating
these strands may be of any kind, india rubber, gutta percha, cotton, paper, jute,
.

page_text: impregnated or not; the thickness of the insulating material between the con-
ducting strands of the conducting cords may also be of any kind, but generally
very thin say a few tenths of millimeters.
The proportion between the section of the insulated peripheral strands and
the section of the central non-insulated strands, may be varied and such as to
facilitate as much as possible the construction of the cables.
Dated this 21st day of November 1898.
Electric Cables for High Tension Currents.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23, Southampton Buildings, in the
County of London, Patent Agent, do hereby declare the nature of this invention
(a communication to me from La Société Française des Câbles Electriques,
Système Berthoud, Borel & Cie., of 11, Chemin du Pré-Gaudry, Lyons, in the
Republic of France) and in what manner the same is to be performed to be par-
ticularly described and ascertained in and by the following statement:.
-
Subterraneous electric cables are generally constituted of one or several copper
cords insulated from the earth as also from each other by the interposition of
layers or coats of materials which are bad conductors of electricity.
Electric cables for currents of high tension 2000 volts and upwards, hitherto
differ only from cables for low tension currents in the quality of the insulating
material employed, and in the thickness of the insulating layers or coats separat-
ing the conductors from each other and from the earth.
The present improvement has for its object to increase the resistance of these
insulating layers or coats, by a special arrangement of the electric cords or
conductors which are enclosed therein.
The conducting cords (the cores, the conductors) of subterranean electric
cables, are generally composed of a certain number of cylindrical strands of
naked copper, twisted together.
The number and diameter of these strands varying with the conducting
section it is desired to obtain.
Experience has brought the communicators to constitute the improved con-
ducting cords for high tension currents in the manner represented at Fig. 1
of the drawings accompanying my Provisional Specification. In the centre, as
usual, are placed twisted together, a certain number of strands A of naked
copper forming a certain fraction of the total required section.
On this central naked copper cord A is placed a concentric layer or coat B,
of copper strands, covered with an insulating layer or coat which insulates them
from each other as also from the central conducting cord, the sum of the metallic
sections of this peripheral layer or coat will complete the section the conductor
is required to have."
The conducting cords thus formed are placed in the usual manner and in con-
venient number in their envelope furnished with insulating material C, as is
shown by way of example, at Fig. 2 in section.
A given thickness of insulating material with these conducting cords with
peripheral insulated strands, resists double or triple tensions, according to the
diameters of the peripheral strands employed, as compared with those which it
resists with ordinary conducting cords of naked strands.

page_text: These new subterranean electric cables may have one or several twisted con-
ductors, or several concentric conductors which may have the entire or only
part of their conducting strands, insulated from each other, and particularly
those of the peripheral layer or coat. The insulating material separating
these strands may be of any kind, india rubber, gutta percha, cotton, paper, jute,
impregnated or not; the thickness of the insulating material between the con-
ducting strands of the conducting cords may also be of any kind, but generally
very thin, say, a few tenths of millimeters.
The proportion between the section of the insulated peripheral strands and
the section of the central non-insulated strands, may be varied and such as to
facilitate as much as possible the construction of the cables.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:―
1. A subterranean electric cable having the strands forming the peripheral
layer or coat of each conductor insulated from each other and from the central
strands, substantially as herein set forth.
2. A subterranean electric cable having each of its conducting cords formed
of a core of twisted naked metallic strands and a peripheral layer or coat of
metallic strands insulated from each other and from the central conducting
cord, substantially as herein set forth.
Dated this 1st day of August 1899.
HARRIS & MILLS,
23, Southampton Buildings, London, "W.C., Agents.