Improved Means for Insulating Underground Electrical Conductors.
Year: 1891

page_text: Date of Application, 12th Mar., 1891
Complete Specification Left, 12th Jan. 1892-Accepted, 13th Feb., 1892
PROVISIONAL SPECIFICATION.
Improved Means for Insulating Underground Electrical Conductors.
I, LUIS FERDINAND HARRY COURTHOPE MORGAN-GRENVILLE, of Stowe,
in the County of Buckingham, Captain in Her Majesty's York and Lancaster
Regiment, do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved method of and means for insulating
electrical conductors, such as electric light on telegraph wires or cables,
particularly such as are laid underground and require to be protected from water
or moisture.
Electrical conductors provided with a perishable covering of insulating material
are sometimes enclosed in iron or lead pipes; the space between the conductor or
conductors and the pipe being filled with oil or with a solid insulating substance
This method is not
which can be melted and poured into the pipe in liquid form.
only expensive, but is unsatisfactory in respect of efficiency, owing to the absence
of permanent means for retaining the conductor or conductors in a central position
relatively to the surrounding pipe.
The object of my invention is to maintain an electrical conductor, whether
furnished with a covering of insulating material or not, in a central position
relatively to the pipe, within which it is enclosed; materials of a permanent
character being alone employed for this purpose. By the means I employ, the
insulation is preserved at a high value so long as the pipe remains intact; and the
quantity of oil or other insulating fluid, employed to fill the interstices and to
prevent the ingress of water, is reduced.
In applying my invention to the insulation of an electrical conductor enclosed in
a pipe, I thread upon the conductor, either before or after introduction to the pipe,
a series of hollow cylinders, perforated spheroids or other conveniently-shaped
bodies resembling 'vertebræ' and made of earthenware, glass or other suitable non-
conducting material. These bodies of non-conducting material fit loosely on the
conductor; the external diameter of the former being rather less than the internal
diameter of the pipe. Between each two lengths of pipe, or at other suitable intervals,
a junction-box or splice-box is provided; the extremities of the said pipes being
securely jointed thereto. At these points, the branch-conductors, if any, are connectel.
The earthenware, glass or other bodies of non-conducting material extend from end to
The pipe on
end of the pipe or from one junction-box or splice-box to the next.
each side of a junction-box or splice-box may be closed by an insulating cover fitting
with a water-tight and oil-tight joint. Each cover may contain a stuffing-box in
which the conductor is packed. The interstices between the non-conducting bodies
and between these and the conductor and the inside of the pipe are filled with oil
or equivalent insulating material capable of being introduced in a liquid form.
The oil is poured in at the lower end of the pipe and gradually ascends; driving
out the air before it. On occount of the annular space between the conductor and
the pipe being almost wholly taken up by the non-conducting bodies, much less oil
is required than where no such bodies are employed. At each end of each length
of pipe, a nozzle may be provided for emptying the pipe of, or refilling the same
with, liquid without disturbing the said pipe."
When cylindrical insulating bodies are used in curved pipes, I prefer to make
one end of each cylinder concave and the contiguous face of the next cylinder
convex. The cylinders are threaded on the conductor with their like ends all
pointing in one direction, so that the convex end of one cylinder fits in the concave
end of the adjoining cylinder. For use in pipes curved to a comparatively small
radius, convex-sided rings may be employed in place of cylinders or spheroids such

page_text: as previously described. The cross section of the conductor, insulating bodies and
pipe may be of any convenient configuration.
If preferred, both hollow cylinders and perforated spheroids or other con-
veniently-shaped bodies may be threaded on the same length of conductor.
Two or more conductors enclosed in 'vertebræ ' may be placed in the same pipe.
Dated this 12th day of March 1891.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improved Means for Insulating Underground Electrical Conductors.
I, LUIS FERDINAND HARRY COURTHOPE MORGAN-GRENVILLE, of Stowe,
in the County of Buckingham, Captain in Her Majesty's York and Lancaster
Regiment, 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 :--
This invention relates to an improved method of and means for insulating
electrical conductors, such as electric light or telegraph wires or cables,
particularly such as are laid underground and require to be protected from water
or moisture.
Electrical conductors provided with a perishable covering of insulating material
are sometimes enclosed in iron or lead pipes; the space between the conductor or
conductors and the pipe being filled with oil or with a solid insulating substance
which can be melted and poured into the pipe in liquid form. This method is not
only expensive, but is unsatisfactory in respect of efficiency owing to the absence
of permanent means for retaining the conductor or conductors in a central position
relatively to the surrounding pipe.
The object of my invention is to maintain an electrical conductor, whether
furnished with a covering of insulating material or not, in a central position
relatively to the pipe, with which it is enclosed; materials of a permanent
character being alone employed for this purpose. By the means I employ, the
insulation is preserved at a high value so long as the pipe remains intact and the
quantity of oil or other insulating fluid, employed to fill the interstices and to
prevent the ingress of water, is reduced.
In applying my invention to the insulation of an electrical conductor enclosed in
a pipe, I thread upon the conductor, either before or after introduction to the pipe,
a series of hollow cylinders, perforated spheroids or other conveniently-shaped
bodies, resembling vertebræ and made of earthenware, glass or other suitable non-
conducting material. The accompanying diagram represents in longitudinal
section an electrical conductor insulated according to my improved method;
A being the conductor, B the hollow cylinders or other insulating bodies threaded
thereon, and C a pipe in which the insulated conductor is enclosed. The bodies B
fit loosely on the conductor A; the external diameter of the former being rather
less than the internal diameter of the pipe C. Between each two lengths of pipe,
or at other suitable intervals, a junction-box or splice-box D is provided; the
extremities of the said pipes C being securely jointed thereto. At these points,
the branch-conductors, if any, are connected. The earthenware, glass or other
bodies of non-conducting material B extend from end to end of the pipe, or from
one junction-box or splice-box to the next. The pipe on each side of a junction-
box or splice-box may be closed by an insulating cover E, fitting with a water-
tight and oil-tight joint. Each cover may contain a stuffing-box e in which the
conductor is packed. The interstices between the non-conducting bodies B and
between these and the conductor A and the inside of the pipe C are filled with oil,
paraffin or equivalent insulating material capable of being introduced in a liquid

page_text: state. The oil is poured in at the lower end of the pipe and gradually ascends,
driving out the air before it. On account of the annular space between the con-
ductor and the pipe being almost wholly taken up by the non-conducting bodies,
much less oil is required than where no such bodies are employed. At each end of
each length of pipe, a nozzle F may be provided for emptying the pipe of, or
refilling the same with, the liquid dielectric. without disturbing the said pipe.
When cylindrical insulating bodies are used in curved pipes, I prefer to make
one end of each cylinder concave and the contiguous face of the next cylinder
convex. The cylinders are threaded on the conductor with their like ends all
pointing in one direction, as represented in the diagram, so that the convex end of one
cylinder fits in the concave end of the adjoining cylinder. For use in pipes curved
to a comparatively small radius, convex-sided rings may be employed as shewn at B³,
in place of cylinders or spheroids, such as previously described. The cross
section of the conductor, insulating bodies and pipe may be of any convenient
configuration.
If preferred, both hollow cylinders and perforated spheroids or other con-
veniently-shaped bodies may be threaded on the same length of conductor, as
illustrated at B².
Two or more conductors furnished in the manner herein before described may be
placed in the same pipe.
After each length of conductor furnished with the non-conducting bodies and
enclosed in the pipe has been fitted up complete from junction-box to junction-box,
but before charging the pipe with oil, I prefer to force air heated to a temperature
of about 400° Fahr. through the length with a view to thoroughly drying the
interior of the pipe and its contents. Whilst the parts are still warm, the oil,
melted paraffin, wax or similar dielectric, is pumped in, as hereinbefore described.
As the paraffin or wax cools, an additional quantity is fed at one or both ends to
compensate for contraction. If preferred, the moisture may be absorbed by means
of air dried by chemical treatment.
Should it at any time be desired to remove the paraffin or wax, an electric
current of sufficient power to heat the conductor is passed through the same;
whereupon the paraffin or wax melts, and may be drained out and preserved for
re-use, or a fresh charge may be substituted.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. The herein-described means for insulating underground electrical conductors,
consisting in threading or otherwise placing upon the conductor a series of hollow
cylinders or equivalent bodies composed of earthenware or other non-conducting
material, enclosing the same in a pipe or channel having closed ends, and filling
the interstices between the conductor, the insulating bodies and the interior of the
pipe or the sides of the channel with oil, paraffin or equivalent insulating material
capable of being introduced in a liquid state.
2. In conjunction with an electrical conductor mounted in a liquid or readily-
liquefiable insulating material enclosed in a pipe, the employment of cylindrical,
spheroidal or equivalent bodies, composed of earthenware or other non-conducting
material, threaded or otherwise placed upon the conductor and serving to retain
the latter in the centre of the pipe, substantially as herein described.
Dated the 31st day of December 1891.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.