Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2014P11308
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1
Description
Inductor and method for heating a geological formaeion
For in-situ extraction of hydrocarbons from an underground
reservoir, for example for extraction of heavy oils, ultra-
heavy oils or bitumen from oil sand or oil shale deposits, it
is necessary to achieve the greatest possible flowability of
the hydrocarbons to be extracted. One option for improving the
flowability of The hydrocarbons during their extraction is to
increase the temperature obtaining in the reservoir.
An applied method for increasing the temperature of the
reservoir is inductive heating by means of an inductor, which
is introduced into the reservoir (i.e. into the ground). By
means of the inductor eddy currents are induced in the
electrically-conductive reservoirs by electromagnetic fields
which form, which heat up the reservoir, so that this
consequently results in an improvement of the flowability of
the hydrocarbons present in the reservoir. Eddy currents are
induced in such cases, especially in the pore water of the
reservoir, which through sales dissolved therein has an
electrical conductivity. The heat is transferred from the
water to the hydrocarbon by thermal conduction.
In order to achieve a sufficient heating power in the
surroundings of the inductor for the required temperature
increase large alternating current strengths of a few 100 A
are typically needed, since the reservoir surrounding the
inductor mostly only has low electrical conductivity. By
operating the inductor with a high alternating current
strength a high inductive voltage drop is produced along the
inductor, wherein the inductive voltage drop can be of the
order of magnitude of a few 100 kV. Such high voltages can
only be handled with difficulty in practice, so that it is
expedient Lo compensate for said voltages.
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Compensation for the inductive voltage drop is made possible,
as described in patent DE 10 2007 040 605, by capacitors
connected in series for example (reactive power compensation).
In the solution presented in said document the current-
carrying conductors of the inductor are interrupted to form
the capacitors and thus have a plurality of interruption
points.
Series connection of capacitors can have the disadvantage that
the interruption point can form weak points of the inductor.
For example partial discharges can occur at the interruption
points in the event of a fault. Because of the inaccessibility
of an inductor introduced deep into the reservoir, especially
high demands are to be placed on the reliability of the
inductor. In particular the aim is a continuous and
maintenance-free operation over ten to twenty years. Should a
capacitor of the inductor fail, because of the series
connection of the capacitors, the whole inductor would cease
to function and would have to be replaced.
The underlying object of the present invention is consequently
to improve the reliability of an inductor.
The invention relates to an inductor for heating a geological
formation, especially a reservoir of a substance containing
hydrocarbons, for example an oil sand, oil shale or heavy oil
reservoir, by means of electromagnetic induction, especially
for recovering the substance containing hydrocarbons from the
reservoir, comprising at least one conductor, wherein the
conductor has at least one interruption point, characterized
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that a rounded conductive body is attached at least in an end
area of the conductor at the interruption point.
Preferably both end areas of an interrupted conductor are
embodied as described above at the interruption point.
The inventive fitting of a rounded conductive body is
especially to be understood as contact between the rounded
conductive body and the end area of the conductor. In this
case the rounded conductive body represents a separate
element. It is not simply a matncr of reshaping the end area
of the conductor.
The inductor represents a current conductor. The current
conductor is preferably manufactured, in a similar manner to a
cable, from a plurality of individual wires insulated
electrically in relation to one another. With the repeated
application of interruption points on the inventive inductor
an electrical series resonant circuit can be obtained, wherein
the design is preferably implemented so that a resonant
frequency ranging from around 13 kHz to 200 kHz is obtained,
which also represents the preferred operating frequency of the
inductor. The inductor is preferably activated via a generator
which is at least operated with the said frequency range in
this case.
The inventive interruption point is used to form conductor
sections acting capacitively (in the sense of capacitors).
This is done by the capacitive coupling of the adjacenn
conductor groups over a defined conductor length - for example
to 50m - for reactive power compensation. The capacitances
are preferably arranged as a series circuit. In a series
circuit, if a capacitor fails, depending on the fault
involved, the complete inductor can cease to function. This
problem is reduced in accordance with the invention by a
parr_ial discharge resistance of insulated individual wires
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being increased in relation to adjacent continuous wires and
the opposite wire ends.
A further inventive advantage is that sharp edges which would
otherwise lead to an excessive field strength increase
(excessive increase in the electrical field strength) at the
interruption point are avoided by the inventive embodiment.
Advantageously the reliability of the inductor is further
improved by the avoidance of the excessive field strengths,
which can lead over the period of continuous operation of the
inductor to a destruction of the insulation layer at the
interruption point and consequently to a failure of the
inductor.
One embodiment of the invention is intended to provide each
individual wire - a core - which is preferably individually
insulated, with such an interruption point. Each wire
preferably has such interruption points at repeated spacings.
This embodiment is advantageous if a wire is prepared for an
inductor in a first step and is only subsequently stranded
with further wires, together with a sequence of interruption
points.
Another embodiment of the invention is aimed at providing a
bundle of wires with such an interruption point, wherein the
wires are preferably individually insulated. At one position
in the inductor all wires of a bundle are interrupted and not
just one wire. The interruption points occur over the length
of the inductor at repeated spacings. This embodiment is
advantageous if an already completely stranded cable without
interruption points is present and is post-processed in a
subsequent step for obtaining an inductor in which a bundle of
wires on the cable is repeatedly separated at specific points.
In an embodiment of the invention the rounded conductive body
can comprise a hemispherical surface or a continuously curved
collar-shaped surface.
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In a further embodiment the conductor can consist of a number
of, preferably single - i.e. individual - insulated wires.
Wire ends of the end area of the conductor can be connected to
the rounded conductive body by means of pressing and/or
crimping and/or soldering and/or welding and/or electrically-
conductive glue ing.
Furthermore the conductor can consist of a single wire. A
plurality of conductors can form the inductor.
Furthermore the rounded conductive body can be embodied at one
end as a sleeve. The end area of the conductor can be
introduced into the sleeve.
In particular the sleeve can have a blind hole or a through-
hole into which the end area of the conductor is introduced
into the sleeve.
Preferably a mechanical connection between the sleeve and the
end area of the conductor can be made by means of pressing
and/or crimping and/or soldering and/or welding and/or
electrically-conductive glueing.
In one embodiment a further rounded conductive body can be
attached to a further end area of the conductor at the
interruption point. An insulating spacer can be positioned
between the rounded conductive body and the further rounded
conductive body.
Furthermore the insulating spacer can have a surface section
embodied such that the surface section of the insulated spacer
is connected mechanically and preferably by a form fit to a
surface section of the rounded conductive body.
Furthermore the insulating spacer can be embodied and surface
shapes of the insulating spacer can engage into surface shapes
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of the rounded conductive body and into surface shapes of the
further rounded conductive body so that the rounded conductive
body and the further rounded conductive body are fixed to each
other without any offset and at a pre-specified distance from
one another.
Preferably a mechanical connection can be made between the
rounded conductive body and the insulating spacer by means of
pressing and/or crimping and/or soldering and/or welding
and/or glueing.
Furthermore the rounded conductive body and the further
rounded conductive body and the insulating spacer can be
introduced into a hollow-cylindrical further sleeve, wherein
the further sleeve is embodied as an insulator or as a
conductive sleeve.
Wires of a further conductor can in this case be routed
through the materlal of the further sleeve embodied as an
insulator.
Preferably wires of a further conductor can be conductively
connected to the material of the conductive sleeve.
The inductor can also have at least two conductor bundles,
wherein a first of the two conductor bundles can comprise at
least the first conductor and a second conductor and a second
of the two conductor bundles can comprise at least a third
conductor and a fourth conductor, wherein a first hollow-
cylindrical sleeve is embodied in one piece such that a jacket
element of the first hollow-cylindrical sleeve and a jacket
element of the second hollow-cylindrical sleeve are combined
with one another for one secelon. A sleeve is thus produced
which in cross-section has the shape of a number 8.
In addition the inductor can comprise at least three conductor
bundles. A first of the three conductor bundles can comprise
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at least the first conductor and a second conductor. A second
of the three conductor bundles can comprise at least a third
conductor and a fourth conductor. A third of the three
conductor bundles can comprise at least the fifth conductor
and sixth conductor. A first hollow-cylindrical sleeve can be
embodied in one piece with the second hollow-cylindrical
sleeve and with a third hollow-cylindrical sleeve such that:
- a jacket element of the first hollow-cylindrical sleeve and
a jacket element of the second hollow-cylindrical sleeve are
combined with one another for a first section, and
- the jacket element of the first hollow-cylindrical sleeve
and a jacket element of the third hollow-cylindrical sleeve
are combined with one another for a second section, and
- the jacket element of the second hollow-cylindrical sleeve
and the jacket element of the third hollow-cylindrical sleeve
are combined with one another for a third section.
In this way an especially compact sleeve element comprising
three hollow cylinders is produced.
In a development of the invention the interruption point of
the conductor and conductor sections adjoining the
interruption point and components provided at the interruption
point can be surrounded by an outer sleeve.
Preferably the inductor can be errhodied as a multifilament
conductor. In particular the conductor can form a conductor or
a wire of the multifilament conductor.
With a plurality of conductors which each have an interruption
point, the respective interruption points of the conductors
can have an offset in relation to each other along a
longitudinal extent of the inductor.
Preferably the conductors can form an interlaced and/or
stranded structure which extends along the longitudinal extent
of the inductor.
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Invention further relates to an operating method for heating a
geological formation, especially a reservoir of a substance
containing hydrocarbons, for example an oil sand, oil shale or
heavy oil reservoir, by means of the electromagnetic
induction, especially for recovering the substance containing
hydrocarbons from the reservoir, in which an inductor with at
least one conductor disposed in the geological formation is
activated such that an electromagnetic field forms in the
geological formation, wherein the conductor has at least one
interruption point for this purpose, wherein a rounded
conductive body is fitted to at least one end area of the
conductor at the interruption point.
Preferably alternating current can he supplied to the
conductor, preferably with a frequency ranging from 10 kHz to
200 kHz.
The hemispherical embodiment of the ends advantageously
compensates for the sharp edges or corners which can arise
when the introduction point is produced, for example from the
separation of the conductor with a cutting tool. The partial
discharge resistance at the interruption point of the
conductor is further improved. This is the case since the
hemispherical even and/or smooth embodiment of the end
prevents excessive field strengths, as occur for example with
edge shapes. Preferably both ends of the interruption point
are embodied in a hemispherical shape.
An embodiment of the end area is preferred in which the radii
of curvature are greater than or equal to a radius of the
cross-section (cross-sectional radius) of the conductor.
Excessive field strengths are further reduced by this, so that
the partial discharge resistance of the conductor at the
interruption point is additionally increased.
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in accordance with an advantageous embodiment of the invention
the conductor forms one conductor of a multifilament
conductor.
There is provision here in particular for all conductors of
the multifilament conductor to have an interruption point, the
end areas of which are embodied in accordance with the
invention. By designing a multifilament conductor from a
plurality of conductors with inventive end areas an especially
advantageous inductor for inductive heating is made possible.
Here the filaments of the multifilament conductor are formed
by the plurality of conductors. Preferably a multifilament
conductor comprises a plurality of at least 10 and at most
5000 conductors. The heating power of the inductor is
advantageously increased by this.
In accordance with an advantageous embodiment of the invention
the interruption point of the conductor is enclosed by an
electrically-insulating outer sleeve.
The outer sleeve is used for mechanical, force-fir connection
of the two ends of the conductor, which ends are formed by the
interruption point of the conductor. The outer sleeve is
expediently embodied as an electrically-insulating sleeve here
to avoid a short-circuit at the interruption point. Preferably
it is an outer sleeve molded from insulating material and/or
insulating plastic which surrounds both ends of the
interruption points. An outer sleeve is provided here of which
the external diameter is significantly larger than the
diameter of the cross-section of the conductor.
An outer sleeve in the sense of the invention is an
electrically-insulating sealing element. It can involve a
molded sleeve which is produced when a hollow shape is molded.
It has an insulating effect and lends mechanical stability.
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An outer sleeve in this case is a connection element, and
especially also an insulation and/or protection element. The
outer sleeve is preferably connected firmly to the introduced
cable. It surrounds an interruption point. Embodiments as
cast-resin sleeves, gel sleeves, shrink sleeves - hot shrink
or cold shrink sleeves - are conceivable.
An inductor with a plurality of conductors is preferred,
wherein the interruption points of the conductors of a
conductor group have a mutual offset along a longitudinal axis
of the inductor. The offset is preferably small by comparison
with the distance to the adjacent interruption points of the
second conductor group.
Through this an inductor is advantageously formed of which the
individual conductors are coupled capacitively to one another.
The series connection of the capacitors which are embodied by
the capacitively-coupled conductors advantageously reduces the
reactive power of the inductor and/or almost compensates for
it in a resonant circuit.
Especially preferred is an inductor consisting of a plurality
of conductors, wherein the conductors extend in parallel along
the longitudinal axis of the inductor.
Advantageously the parallel course of the conductors means
that an approximately constant capacitance between the
conductors is made possible, so that there is an even and
equally-distributed loading of the conductors of the inductor.
In accordance with an advantageous embodiment of the invention
the conductors form an interlaced and/or stranded structure
which extends along the longitudinal axis of the inductor.
This advantageously makes possible a cable arrangement of the
conductors of the inductor which, through an interlacing
and/or stranding, on the one hand is mechanically stabilized
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and on the other hand is suitable for formation of
capacitances between the individual conductors.
In accordance with an advantageous embodiment of the invention
alternating current is supplied to the conductor. If the
conductor corresponds to a conductor group the conductor group
is supplied with alternating current.
Advantageously all conductor groups of the inductor are
supplied with alternating current.
This means that advantageously, by means of the inductance of
the conductor and the capacitances which are formed by the
interruption point and by means of the adjacent conductors, an
electrical resonant circuit with a resonant frequency specific
to the resonant circuit is embodied. Advantageously, through
the embodiment of a resonant circuit, especially in the
resonance of the resonant circuit, the reactive power which
must be provided for the operation of the inductor is reduced.
Here the offset of the interruption point, which offset
continues periodically along the conductors or the inductor,
corresponds to the resonance length of the inductor.
Supply of an alternating current of which the frequency ranges
from 10 kHz to 200 kHz is expedient.
Advantageously the resonant frequency of the resonant circuit
lies in the said range of 10 kHz to 200 kHz here.
The invention also relates to a manufacturing method for an
inductor for heating a geological formation, especially a
reservoir of a substance containing hydrocarbons, for example
an oil sand, oil shale or heavy oil reservoir, by means of
electromagnetic induction, comprising the following
manufacturing steps for at least one longitudinal position of
a cable:
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- Providing the cable with at least two conductor bundles
Lwisted with one another;
- Soreading out a first of the two conductor bundles at the
longitudinal position of the cable;
- Separating all wires of a second of the two conductor
bundles at the longitudinal position of the cable;
- Removing insulation from cable ends of the separated
wires;
- Connecting rounded conductive bodies to a de-insulated
cable end in each case;
- Inserting a respective spacer between pairs of rounded
conductive bodies;
- Optionally inserting a hollow-cylindrical shaped sleeve,
wherein wires of the first conductor bundle are routed in
a jacket surface of the sleeve;
- Optionally fitting an outer sleeve mold, injecting the
outer sleeve mold into an outer sleeve, wherein the outer
sleeve surrounds the rounded conductive bodies and a
section of the two conductor bundles, and removing the
outer sleeve mold.
As an alternative the invention relates to a further
manufacturing method for an inductor for heating a geological
formation, especially of a reservoir of a substance containing
hydrocarbons, for example an oil sand, or oil shale or heavy
oil reservoir, by means of the electromagnetic induction,
comprising the following manufacturing steps:
a) Carrying out the following working steps for at least one
longitudinal position of a wire:
- Providing the, preferably insulated, wire;
- Separating the wire at the longitudinal position of the
wire;
- Removing insulation from the two cable ends of the
separated wire;
- Connection of rounded conductive bodies in each case to a
respective de-insulated cable end;
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- Inserting a respective spacer between pairs of rounded
conductive bodies;
- Optionally fitting an outer sleeve mold, injecting the
outer sleeve mold into an outer sleeve, wherein the outer
sleeve surrounds the rounded conductive bodies and two
end areas of the separated wires, and removing the outer
sleeve mold;
b) Winding the processed wire and/or stranding a plurality of
wires processed in this way to form an inductor.
In the present method the rounded conductive bodies are
preferably first connected to the de-insulated cable ends.
Subsequently the respective spacers are inserted between pairs
of rounded conductive bodies.
These last mentioned steps can also be reversed as an
alternative, so that first of all an already connected unit
consisting of a spacer and a pair of rounded conductive bodies
connected to said spacer are provided. This unit is preferably
already connected using a force fit. Subsequently this unit
can be connected to the two de-insulated cable ends.
b) Winding the processed wire and/or stranding a plurality of
wires processed in this way to form an inductor.
The manufacturing method can preferably be implemented so that
the connection of rounded conductive bodies to a respective
de-insulated cable end in each case is carried out with the
following steps:
- Pushing sleeves onto the respective cable ends, wherein
the sleeves :In each case surround the rounded conductive
bodies;
- Force-fit connection, especially crimping, of the
respective sleeve with the respective de-insulated cable
end.
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In addition the aforementioned twisting of a plurality of wires
processed in this wat to form an inductor can be carried out
with the following steps:
Arranging a number of processed wires in relation to
one another so that at least two bundles of wires are formed,
whereby the wires of a first of the two bundles are aligned
in a longitudinal alignment to one another so that separation
points of the separated wires of the first bundle largely come
to lie next to one another and the wires of a second of the two
bundles in the longitudinal alignment are aligned in relation
to one another so that separation points of the separated wires
of the second bundle largely come to lie next to one another,
wherein the separation points of the first bundle are disposed
offset in relation to the separation points of the second
bundle to one another;
Stranding the wires thus disposed so that the wires
of the first bundle and of the second bundle are stranded
alternately to one another.
According to one aspect of the present invention, there is
provided an inductor for heating a geological formation, by
means of electromagnetic induction, comprising at least one
conductor, wherein the conductor has at least one interruption
point, wherein a rounded conductive body is fitted to at least
to one end area of the conductor at the interruption point, and
the rounded conductive body is embodied at one end as a sleeve
and the one end area of the conductor is introduced into the
sleeve.
According to another aspect of the present invention, there is
provided an operating method for heating a geological
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formation, by means of electromagnetic induction, in which an
inductor disposed in the geological formation with at least one
conductor is activated such that an electromagnetic field forms
in the geological formation, wherein the conductor has at least
one interruption point, wherein a rounded conductive body is
attached at least to one end area of the conductor at the
interruption point.
According to still another aspect of the present invention,
there is provided a manufacturing method for an inductor for
heating a geological formation, by means of electromagnetic
induction, comprising the following manufacturing steps: a)
carrying out the following working steps for at least one
longitudinal position of a wire: providing, the wire;
separating the wire at a longitudinal position of the wire;
removing insulation from two cable ends of the separated wire;
connecting rounded conductive bodies in each case to a
respective de-insulated cable end; inserting a respective
spacer between pairs of rounded conductive bodies; b) winding
the processed wire and/or stranding a plurality of wires
processed in this way to form an inductor.
According to yet another aspect of the present invention, there
is provided a manufacturing method for an inductor for heating
a geological formation, by means of electromagnetic induction,
comprising the following manufacturing steps: a) carrying out
the following working steps for at least one longitudinal
position of a wire: providing the wire; separating the wire at
the longitudinal position of the wire; removing insulation from
the two cable ends of the separated wire; providing an already
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connected unit consisting of a spacer and a pair of rounded
conductive bodies connected to said spacer; connection of the
unit to the two de-insulated cable ends; b) winding the
processed wire and/or stranding a plurality of wires processed
in this way to form an inductor.
Further advantages, features and details of the invention
emerge from the exemplary embodiments described below as well
as with reference to the drawings. In the drawings, in
schematic diagrams:
Figure 1 Shows an inductor section which has a conductor with
spherical terminations of an interruption point, after a first
manufacturing step;
Figure 2 shows a cross-sectional drawing of Figure 1 with a
spacer, after a second manufacturing step;
Figure 3 shows a cross-sectional drawing of Figure 2 with an
additional hollow-cylindrical surrounding insulation body,
after a third manufacturing step;
Figure 4 shows a three-dimensional diagram of Figure 3;
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Figure 5 shows a three-dimensional diagram of Figure 2 with an
additional hollow-cylindrical surrounding insulation
body, after an alternate third manufacturing step;
Figure 6 shows a diagram of three conductor sections with
additional hollow-cylindrical surrounding insulation
bodies attached in each case, which are part of the
inductor as a whole;
Figure 7 shows a diagram of an alternate embodiment of three
conductor sections with attached additional hollow-
cylindrical surrounding insulation bodies in each
case, which are part of the inductor as a whole;
Figure 8 shows a schematic diagram of an inductor section
comprising two multifilament conductors;
Figure 9 shows a sectional drawing of an alternate inductor
section in which an interruption point is connected
mechanically via two sleeves, a spacer and an outer
sleeve;
Figure 10 shows a sectional drawing of a further alternate
inductor section in which an interruption point is
connected mechanically via two alternately designed
sleeves, a spacer adapted thereto and an outer
sleeve;
Figure 11 shows a schematic diagram of a perspective view of an
inductor in a reservoir.
The same elements can be provided with :he same reference
characters in the figures.
The figures relate to an inductor 1 for the exploitation of
oil sand and heavy oil reservoirs, which is provided for
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heating up a reservoir in order to improve the flowability
in-situ of the hydrocarbons to be extracted. The
electromagnetic heating method presented is also called
inductive heating, in which one or more conductor loops to
which alternating current is supplied are introduced into the
reservoir. Subsequently eddy currents, which then heat up the
reservoir, are induced in the electrically-conductive
reservoirs. In accordance with the present invention the
current conductors, in a similar way to cables, are
manufactured from a plurality of electrically-insulated
individual wires.
Half of the individual wires are interrupted alternately and
at defined spacings. Thus the electrical current is forced to
penetrate the individual wire insulation as displacement
current. The cable inductor - inductor 1 - thus acts in
sections as a capacitance, through which the inevitable
inductance of the conductor arrangement can be compensated for
explicitly for a frequency. The conductor loop with the
periodically arranged interruptions acts electrically as a
series resonant circuit. In which is resonant frequency can be
operated without reactance, i.e. without reactive power.
The embodiment of interruption points in the cable inductor
discussed below has the advantage that sharp-edged wire ends
can be avoided. Since especially high electrical field
strengths can arise at sharp-edged wire ends it is
advantageous to avoid such embodiments.
Figures 1 to 7 relate to an embodiment in which a conductor in
the sense of the invention consists of a plurality of
individual wires. All these individual wires belonging to a
conductor are separated at one interruption point.
Figure 1 shows a section of an inductor 1, wherein the
inductor 1 comprises a conductor 2 with an interruption point
4. In the exemplary embodiment shown the inductor 1 is thus
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embodied by means of the conductor 2 and further conductors
not shown in the figure, wherein a plurality of conductors
embodied in the same way is preferred for the inductor 1 for
adaptation to the resonant frequency for example. To form a
suitable capacitance a second conductor largely running in
parallel to conductor 2 (not shown in Figure 1 but illustrated
in Figure 4) is provided. Here the second conductor (labeled
with reference characters 3 in Figure 3 and 4) has an
interruption point 4 offset in relation to the conductor 2,
wherein the offset is continued periodically and corresponds
to the resonance length.
At the interruption point 4 the conductor 2 has two end areas
6 to each of which a rounded conductive body 40 and 40' is
attached. The rounded conductive bodies 40 form ends of the
conductive cable-type structure.
The rounded conductive bodies 40, 40' are embodied in
accordance with Figure 1 in a hemispherical shape or a three-
quarter spherical shape, wherein the rounded parts of the two
rounded conductive bodies 40, 40' lie opposite one another and
are at a distance from one another and are thus not touching.
The hemispherical embodiment or shape of the ends means that
excessive field strengths are avoided at the ends and
consequently at the interruption points 4, so that through
this the partial discharge resistance of the interruption
points 4 is increased.
In accordance with Figure 1 a number of twisted wires form the
conductor 2.
The conductor 2 extending along a longitudinal axis A is
preferably surrounded by a layer of insulation (not shown),
which surrounds the conductor 2. Individual wires are likewise
preferably provided with an individual layer of insulation.
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The rounded conductive bodies 40, 40' are each full bodies
which are embodied conductive. In particular metals or
metallic alloys are considered as material.
The rounded conductive bodies 40, 40' can be called
electrodes. They are preferably massive bodies and/or solid
bodies. They are rounded in the same direction in which the
separated cable end would otherwise point.
Ends of the individual wires are connected to the respective
conductive bodies 40 or 40', especially on a rear side of the
rounded conductive bodies 40 or 40', which for their part can
form an even surface. The mechanical and conductive connection
of the wires with a respective rounded conductive body 40, 40'
can be made by soldering, welding, crimping or another
connection technology. Penetration of a wire end into the rear
side of a rounded conductive body 40, 40' to achieve a firm
and conductive connection is illustrated in Figure 2 for
example.
In operation the rounded conductive bodies 40, 40' are at the
same electrical potential as the conductor 2.
The rounded conductive body 40 (or also 40') can also be seen
as an electrode of a capacitor. In accordance with Figure 1
there are pairs of spherical electrodes into which all or at
least a number of wire ends are merged and electrically
connected. This avoids sharp-edged wire ends as well as the
resulting high electrical field strengths at these sharp-edged
wire ends, at which partial discharges would strike by
preference.
A force-fit and form-fit paired fixing of the rounded
conductive bodies 40, 40' can be provided. This is illustrated
in Figure 2 in a cross-sectional drawing. This figure shows an
insulating body as an insulating spacer 32. This is preferably
made of ceramic and/or mineral and/or plastic-based material.
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It comprises, at least partly, a pair of rounded conductive
bodies 40, 40'. The surface shape of a section of the
insulating spacer 32 in this case is adapted to the surface
shape of one of the rounded conductive bodies 40, 40'.
Preferably - as shown in Figure 2 - the insulating spacer 32
has two opposing recesses into which in each case a rounded
conductive body 40, 40' can he introduced at least partly.
The insulating spacer 32 can in such cases be a solid body
which has been manufactured in advance and is merely connected
to the rounded conductive bodies 40, 40'. As an alternative
the insulating spacer 32 can also be applied in liquid form by
means of injection-molding and/or filling technology, wherein
the material subsequently hardens. The insulating spacer 32
(also called the insulating layer) can be attached to the
surface of the conductor 2 by means of extrusion.
The insula,:ing spacer 32, which can preferably be ceramic or
mineral-based or can also be plastic-based, encloses the
electrodes, keeps them at a defined distance, centers them
relative to the conductor structure passing through them (not
shown in Figure 1 and 2, but shown in Figure 3) and thus
insures a defined electrical field distribution without
excessive fields (i.e. low relative peak values).
The rounded conductive bodies 40, 401, together with the
insulating spacer 32 simultaneously make possible a mechanical
and electrical stability of the insulation at the interruption
points 4 of the conductor 2.
In accordance with the invention the rounded conductive body
40 or 40' represents a separate element or a separate body
before assembly, which only forms a unit when joined to the
conductor 2. The rounded conductive body 40 or 40' is in
particular not merely the cable end of a separated conductor.
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Figures 1, 2, and 3 can be understood such that they
illustrate the inductor 1 at different consecutive stages of
its manufacture.
Figure 3 illustrates, in a cross-sectional drawing, how two
conductors 2 and 3 are advantageously disposed at an
interruption point 4 of one of the conductors 2. An inner
conductor corresponds to the conductor 2, which has an
interruption point 4 with a pair of rounded conductive bodies
40, 40' and an insulating spacer 32 disposed between them. A
further conductor 3 - likewise embodied by a number of twisted
wires - is routed - in a largely annular manner - past the
interruption points 4 :o the outside. For this purpose a
surrounding hollow-cylindrical insulation body 34 can be
provided at the interruption points 4, wherein the wires of
the further conductor 3 are routed through a jacket surface of
the hollow-cylindrical insulation body 34. For this purpose
the hollow-cylindrical insulation body 34 can have grooves
into which the wires of the conductor 3 can be inserted.
For the section of the drawing shown the conductor 2
represents an inner conductor. The further conductor 3
represents an outer conductor. For another section however the
conductor 2 can represent the outer conductor and the
conductor 3 the inner conductor.
Figure 4 shows the same arrangement as Figure 3 in a three-
dimensional view from outside.
The overall structure of the interruption in accordance with
Figure 3 and 4 is achieved by routing the two conductor groups
(2 and 3) away from each other into an inner group and an
outer group. The inner wires (i.e. the conductor 2) are
interrupted and merged on both sides into spherical
electrodes, while the outer continuous wires (i.e. the further
conductor 3) are routed in a defined manner in an insulating
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21
body. The entire arrangement can additionally be encapsulated
with an insulating mass or enclosed by shrink tubing.
Figure 3 and 4 illustrate how a twisted cable consisting of
two groups of wires can be processed, in which a first group
of wires is widened and/or spread out in order to make an
interruption for a second group of wires. In the axial course
the two groups will be merged together again, so that at the
two edges of the diagram of Figure 4 a largely normal twisted
cable is to be seen. Were Figure 4 now to be extended, which
is not shown however, the second group of wires would now be
widened and/or spread out at the resonance link distance, in
order now to make an interruption for the first group of
wires.
The hollow-cylindrical insulation body 34, through the jacket
surface of which the wires of the further conductor 3 are
routed, insures a defined distance of the wires of the further
conductor 3 from the rounded conductive bodies 40, 40. In
this way danger of electrical flashover is prevented. The
wires of the further conductor 3 are not interrupted by the
hollow-cylindrical insulation body 34 but run through the
insulation body 34.
Largely identical in its outer embodiment to Figure 3 and 4,
the hollow-cylindrical insulation body 34 can also be replaced
by a hollow-cylindrical conductor piece 33. This is
illustrated with reference to Figure 5.
Figure 5 represents an alternative to Figure 3 and 4 and shows
that the continuous outer wires of the further conductor 3
(thus the outer conductor for the section of the drawing
shown) are merged mechanically and electrically in a hollow-
cylindrical-shaped conductor 33. The inner insulation body
which still exists - the spacer 32 - holds the spherical
electrodes in position in relation to one another and relative
to the outer conductor (3) or to the hollow-cylindrical-shaped
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conductor 33. Once again defined electrical field
distributions with small excessive fields are achieved, for
which preferably the edges of the hollow-cylindrical-shaped
conductor 33 are also rounded.
In a similar way to the hollow-cylindrical insulation body 34,
the wires of the further conductor 3 can be simply routed
through the hollow-cylindrical-shaped conductor 33 so that the
hollow-cylindrical-shaped conductor 33 and the wires of the
conductor 3 have the same potential.
As an alternative the wires of the further conductor 3 can be
separated at the interruption point. Subsequently the
separated ends can be connected mechanically and electrically
to the hollow-cylindrical-shaped conductor 33. This method of
operation has the advantage that the complete inductor can be
separated on the spot, then the rounded conductive bodies 40,
40' and the spacer 32 can be inserted for the conductor 2, and
subsequently the wires of the conductor 3 can be connected
again via the hollow-cylindrical-shaped conductor 33.
Processing is thus simplified.
The cable inductor (inductor 1) can be constructed from a
number of conductor bundles. Figure 6 shows the inductor 1
with a three conductor bundles, which each have an outer
insulator (34) in accordance with Figure 3 and 4. In Figure 6a
a conductor bundle is largely covered in the three-dimensional
view by a further conductor bundle. Figure 6b shows the view
of the three conductor bundles from the axial direction. All
conductor bundles each have an interruption point 4, wherein
the interruption points 4 are made at a different longitudinal
position along the inductor 1. The positioning of the
interruption points 4 is illustrated with reference to
Figure 8.
The cable inductor in accordance with Figure 6 is constructed
from a number of conductor bundles which are all interrupted
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within a short axial distance in relation to one another (e.g.
within 1m). The inner conductors of the bundle can be
interrupted individually, wherein the interruptions are made
with a small axial offset. The interruptions (i.e. the
interruption points 4) could then be encapsulated together in
a an outer cable sleeve (not shown).
As an alternative - not shown - all wires of a respective
outer conductor (corresponding to the further conductor 3 as
shown in the figures) can now be formed from different bundles
into a common outer conductor. Likewise not illustrated, the
common outer conductor could be routed through a common cuter
insulating body.
Figure 6 shows a diagram with a number of hollow-cylindrical
insulation bodies 34. In a similar way an embodiment with
metal cylinders (from Figure 5) can also be embodied in
accordance with Figure 6. I.e. in this case hollow-cylindrical
insulation bodies 34 are not involved but rather a number of
hollow cylindrical metallic bodies 33. Otherwise the
embodiment in accordance with Figure 6 applies
correspondingly.
Figure 6b shows a cross-section through an inductor on an
inductor section in which the wires are not spread out. The
cross section is thus taken through a section in which the
wires are twisted in a compact manner. The cross-sectional
plane would be outside the area illustrated in Figure 6a.
Figure 6b therefore also additionally shows that the wires of
the conductor 2 and the wires of the further conductor 3, in
the sections of the inductor in which they are not spread out,
are twisted such that the wires of the conductor 2 and the
wires of the further conductor 3 are arranged alternately.
In a similar way to Figure 6, Figure 7 shows the inductor 1
with three conductor bundles, which each have an external
insulator (34) in accordance with Figure 3 and 4. In Figure ia
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a conductor bundle is largely hidden in the three-dimensional
view by a further conductor bundles. Figure 7b shows the view
of the three conductor bundles from the axial direction. All
conductor bundles each have an interruption point 4, wherein
the interruption points 4 can occur at different longitudinal
positions along the inductor 1 or at the same longitudinal
position. The diagram in Figure 7 is to be understood such
that, for the insulation body 34 shown, just one conductor is
interrupted. As an alternative a number of conductors can also
be interrupted for the insulation body 34 shown.
The cable inductor in accordance with Figure 7 is constructed
from a number of conductor bundles. The inner conductors of
the bundle can be interrupted individually. The interruptions
can then be encapsulated together in an outer cable sleeve
(not shown).
The three separately embodied hollow-cylindrical insulation
bodies 34 from Figure 6 are now embodied in accordance with
Figure 7 as a common body 34', in which three hollow cylinders
are connected via their jacket surface with one another.
Figure 7b illustrates in this case that the central axes of
the three hollow cylinders are disposed offset in relation to
each other by 1200 in each case, in relation to a central axis
of the insulation body (34'). This type of arrangement does
not lead to any lateral offset and thus leads to a very
compact construction.
Figure 7 shows a diagram with a number of combined hollow-
cylindrical insulation bodies 34'. In a similar manner an
embodiment with a common metallic cylinder (combined from the
individual metallic cylinders from Figure 5) can also be
embodied in accordance with Figure 7. I.e. in this case a body
made of a number of hollow-cylindrical insulation bodies is
not involved but rather a body made of a number of hollow
cylindrical metallic bodies. Otherwise the embodiment in
accordance with Figure 7 applies correspondingly.
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It can be seen from Figures 4, 5, 6 and 7 that the inductor 1
per se is a twisted cable comprising a plurality of
individually insulated wires, wherein the twisting may
possibly he widened out for the interruption points. In the
said figures two conductor bundles - labeled 2 and 3 - are
shown, wherein all wires of a conductor bundle are at the same
potential. The wires of the conductor bundle are twisted so
that wires of the first conductor bundle are adjacent to wires
of a second conductor bundle and then once again adjoin wires
of the second conductor bundle. Through this adjacency of
different phases of the wires the capacitive effect between
the wires can be improved.
Also conceivable are inductors with more than two conductor
bundles. Then, for N conductor bundles one wire of each of the
different conductor bundles is disposed adjacent to one
another, to which the next N wires are then adjoined by a wire
in each case of the different conductor bundles.
All these wires run in an extent of the inductor 1 but are
twisted together however.
It is also conceivable to form different groups of wires and
to twist each group individually, wherein the inductor 1
includes all twisted groups.
Figure 8 shows an inductor 1 which has at least two
multifilament conductors 21, 22, wherein the multifilament
conductors 21, 22 are formed in each case from a plurality of
conductors 2.
Each conductor 2 of the multifilament conductors 21, 22
consequently has interruption points 4, wherein the end areas
6 of the conductors 2 not shown are embodied in accordance
with the invention at the interruption points 4. In other
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words the multifilament conductors 21, 22 are made up of a
plurality of conductors 2 in accordance with Figure 1.
The conductors 2 of the multifilament conductor 21, 22
essentially run in parallel to one another. Through the
interruption points 4 and an offset 14 of the interruption
points 4 of the first multifilament conductor 21 in relation
tc the interruption points 4 of the second multifilament
conductor 22, the conductors 2 of the first multifilament
conductor 21 are advantageously coupled capacitively with the
conductors 2 of the second multifilament conductor 22. The
offset 14 here essentially corresponds to a resonance length,
wherein the offset 14 continues periodically along the
conductor 2. The conductor 2 here has a plurality of
interruption points 4, wherein the interruption points 4 of
each conductor 2 have a constant spacing from one another.
The partial discharge resistance of the inductor 1 is
advantageously improved by the end areas 6 of the conductor 2
of the multifilament conductors 21, 22 not shown in any
greater detail and embodied in accordance with the invention.
In addition the mechanical strength at the interruption points
4 is increased.
Figure 9 shows a schematic cross-sectional diagram in which
the rounded conductive body 40, 40 is placed as a sleeve 31
on a cable end of a respective wire of the inductor.
Figures 9 and 10 relate here to an embodiment in which a
conductor in the sense of the invention consists of a single
individual wire - a single strand. Each individual wire is
separated at an interruption point and the two ends produced
are each individually provided with one sleeve 31.
In accordance with Figure 9 an interruption point 4 is shown
as an alternate embodiment to Figure 1 to 5. An end area 6 of
the conductor 2 - this can involve a plurality of twisted
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strands - has its insulation removed. Otherwise the conductor
2 is surrounded by an insulation 55. A largely cylindrical and
largely rotation-symmetrical sleeve 31 surrounds a recess for
receiving the end area 6 of the conductor 2. The other end of
the sleeve 31 forms the rounded conductive bodies 40, 40'. By
accepting the end area 6 of the conductor 2 into the recess of
the sleeve 31 and establishing a firm connection, the rounded
conductive body 40, 40' is thus applied to the conductor 2.
The firm connection - conductive and making a form fit - is
preferably made by means of pressing and/or crimping and/or
soldering and/or welding and/or electrically-conductive
glue ing.
The other end of the interrupted conductor likewise receives a
corresponding sleeve 31.
The sleeve 31 - also called the screening sleeve below - is in
this case a molded part, preferably made of copper or of
another electrically-conductive material.
The sleeve 31 corresponds to a cable shoe which can be pushed
during manufacturing of the inductor over a wire end - the end
area 6.
The sleeve 31 is thus at the same electrical potential during
operation as the conductor 2.
In accordance with the surface shape of The rounded conductive
bodies 40, 401 an insulating spacer 32 with two opposing
recesses is provided, which each correspond to the surface
shape of the rounded conductive body 40, 40'.
In this way the insulating spacer 32 can be connected via a
form fit and/or force fit to the rounded conductive bodies 40,
40'.
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The insulating spacer 32 in accordance with Figure 9 has a
recess into which the rounded conductive body 40, 40 can
penetrate. The insulating spacer 32 surrounds the sleeve 31
Preferably also transverse to the axial extent of sleeve 31,
so that the sleeve 31 is disposed coaxially with the conductor
2 and/or the insulating spacer 32.
In accordance with Figure 9 the entire arrangement of the
interruption points 4 is enclosed by an electrically-
insulating outer sleeve 30. The outer sleeve 30 in this case
is especially a molded outer sleeve. A molded outer sleeve has
the advantage that voids and air pockets can be avoided. The
outer sleeve 30 has an insulating effect and at the same time
lends mechanical stability.
The outer sleeve 30 in particular surrounds the two end areas
6 of the conductor 2, the two sleeves 31 and the spacer 32.
Preferably the outer sleeve 30 surrounds sections of the
conductor 2 already insulated, but also especially the
sections of the conductor 2 in the end areas 6 in which
insulation has been removed. The outer sleeve 30 in this case
is especially a rotation-symmetrical body.
In order to explain the manufacturing mer_hod reference is
further made to Figure 9. The two wire ends which are produced
when a wire is interrupted are introduced into the insulation
elements in order to connect them to each other mechanically
in a defined position and insulate them electrically. The
insulation element consists of two conductive screening
sleeves (31) (for example as a molded copper part), an
electrically-insulated spacer 32 mechanically connecting the
screening sleeves (31) and an insulating envelope acting
outwards which is especially embodied as a molded outer sleeve
(30). Each screening sleeve (31), which consists of material
which conducts electricity well - for example copper,
aluminum, other metals or alloys, graphite, possibly
electrically-conductive plastics such as CF PEEK (carbon fiber
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reinforced polyetheretherketone) has a hole into which the
individual wire end from which a few millimeters of insulation
has previously been stripped back is introduced. The
mechanical and electrical connection of the individual wire
end and screening sleeve (31) can be made by deforming the
collar of the screening sleeve (31) by means of a suitable
press/crimp tool, wherein the tool is designed such that no
burrs or edges occur on the screening sleeve (31). As an
alternative the connection can be made by soldering, welding
or electrically-conductive glueing. The spacer 32 is made of a
high-temperature-resistant and electrically-insulating
material, for example a plastic such as PFA (Perfluoro Alkoxy
Aikene), PTFE (Polytetrafluorethylene) or PEEK
(Polyetheretherketone) or a ceramic. The screening sleeves
(31) are introduced mechanically rigidly, preferably with a
form fit, into the spacer 32. The spacer creates a defined
axial distance between the screening sleeves (31), crier= the
screening sleeves (31) coaxially and centers them. The
production of the insulating element is concluded by a gas-
free enveloping (in the form of the said molded outer sleeve)
of screening sleeve pair (31) and spacer 32 through a high-
temperature-resistant insulation material, which is already on
the individual wire insulation. Preferably insulating plastics
(for example those mentioned above) can be used for this
purpose. Especially suitable are those which can be applied by
an injection (vacuum) molding or extruding method. In
particular the same thermoplastic can be used which already
forms the outer layer of the individual wire insulation and/or
the spacer 32, for example PFA.
Figure 10 shows an alternative embodiment to Figure 9, in
which the arrangement is embodied analogously to that shown in
Figure 9, except for the shape of the sleeves 31 and the
spacer 32. The transition between the sleeve 31 and the spacer
32 is however largely inverse to Figure 9, i.e. concave
surfaces are now convex and vice versa.
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The rounded conductive body 40, 40' has a hemispherical convex
surface in Figure 9. In accordance with Figure 10 it now has a
continuously curved collar-shaped surface (40B). The surface
of the sleeve 31 is concave in sections. Since the sleeve 31
is preferably rotationally-symmetrical, the shape of the a)dal
end side directed towards the spacer 32 can also be referred
to as toroidal, more precisely as semi-toroidal.
The spacer 32 is again adapted to the surface of the sleeve
31. Consequently the insulated spacer 32 has a rounded pin.
The pin in this case can be introduced into the recess of the
central collar-shaped surface (40B) of the sleeve 31, so that
a stable connection between sleeve 31 and spacer 32 arises.
Preferably the spacers 32 in Figure 9 and 10 are embodied
axis-symmetrically and rotation-symmetrically. However it is
also possible to provide individual shapes so that the spacer
32 and the sleeve 31 engage into one another so that only a
specific position is possible. It should be insured here
however that the surfaces of the conducting elements are as
even in shape as possible and the conductive body is rounded,
so that a flashover of an arc can be avoided.
The spacer 32 creates a defined axial distance between the
surfaces (40A) of the screening sleeves (31) facing towards
one another. It orients the screening sleeves (31) coaxially
to one another. It centers them in relation to one another.
The embodiment of Figure 10 differs from that of Figure 9 in
that the spacer 32, similar to the wire ends, is introduced
into a screening sleeve (31) modified for its part with blind
holes on both sides. As an alternative - not shown - a
through-hole with possibly different radii on both sides of a
screening sleeve (31) can be used. The connection of screening
sleeve (31) and electrically-insulating spacer 32 can be made
by pressing or crimping (possibly in one operation together
with the wire ends) or glueing. Theinjection-molded outer
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31
sleeve finally applied - i.e. the outer sleeve 30 - once again
insures insulation radially outwards, especially to the
adjacent continuous wires.
Figures 1 to 7 relate to an embodiment in which the conductor
2 in the sense of the invention consists of a plurality of
individual wires. All these individual wires belonging to a
conductor are separated at one interruption point. This is
advantageous if a twisted cable already exists and
interruption points are to be inserted retroactively.
Figures 9 and 10 by contrast relate to an embodiment in which
the conductor 2 in the sense of the invention consists of a
single individual wire. This individual wire can for example
have a cross-section of around 1 mm2. Each individual wire is
separated at an interruption point and the two ends produced
are each provided with a sleeve 31. This embodiment is
advantageous if individual wires are provided with
interruption points beforehand and only subsequently is a
twisting or stranding or winding into a common cable
comprising a number of these individual wires undertaken. The
stranding has the effect of relieving the strain on the
inductor 1.
The use of rounded surfaces (cf. 40, 40') at the interruption
point 4 has the following advantages:
The arrangement makes it possible to avoid local peaks of the
electrical field strengths at conductor edges and points which
would otherwise be present which could lead to partial
discharges and thus to the failure of the inductor 1. It is
further advantageous that the number of critical conductor
ends is drastically reduced, which likewise serves to enhance
reliability.
A positive side effect is that the inductor cable (in a first
step however without interruptions) can be continuously
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manufactured like a normal cable and the interruptions can be
made retroactively. It is thus especially possible to subject
the still uninterrupted cable to a partial discharge test
beforehand in order to identify possible weak points of the
individual conductor insulation in advance.
Furthermore the determination of the resonant frequency, which
depends like the inductor loop geometry on the distance
between the interruptions, can be tuned after the cable
manufacturing to the respective reservoir and does not have to
be known before the cable manufacturing. I.e. the cable can be
manufactured within limits independent of the individual
reservoir and the adaptation is only made by the retroactive
insertion of the interruption points at an individually
defined distance (resonance length).
The advantages of the insulation element are also as follows:
The screening sleeves (31) envelope the individual wire ends
which, because of the separation/cutting without further
measures, generally have sharp edges and burrs and avoid peaks
of the electrical field at the individual wire ends because of
the screening effect caused by equal potential of wire end and
screening sleeve (31).
Excesses of the electrical field do not occur on the outer
surfaces of the screening sleeves (31), since the screening
sleeves (31) in accordance with the invention do not have any
edges, but only roundings.
The spacers 32 insure that the electrical field strength
between a screening sleeve pair (reference character 31 in
each case) do not exceed any critical values.
Critical field strengths at the end of the individual wire
insulation of the wire end are avoided or reduced by the
overhang of the screening sleeve (31) provided. This point is
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critical since it may not be able to be insured that they can
be surround-molded in a gas-free manner.
The insulation element creates a connection with tensile
strength from one wire end via first screening sleeve (31),
spacer 32, second screening sleeve (31) to the other wire end.
This is needed for subsequent s-,1-randing steps.
The spacer according to Fiaure 9 guarantees a minimum layer
thickness of the insulation thickness in the radial direction,
even if the molded outer sleeve - i.e. the outer sleeve 30 -
is attached axially offset, since the spacer during the
injection molding process can rest at a maximum on the inner
wall of the injection mold.
With the spacer 32 according to Figure 10 a more rational
production may possibly be achieved, in that the wire ends can
be pressed simultaneously with the spacer 32 with the
screening sleeve (31).
Figure 11 shows a perspective cross-section of an oil sand
reservoir as the reservoir with an inductor 1, which can also
be referred to as an electrical conductor loop, running
largely horizontally in the reservoir. An oil sand deposit
referred to as a reservoir is shown, wherein for the specific
considerations a cuboid unit 100 with the length 1, the width
w and the height h is chosen as an example. The length 1 can
amount to up to a few multiples of 500 m, the width w 60 up to
100 m and the height h about 20 to 100 m. it should be taken
inLo account that, starting from the earth surface E, an
"overburden" of depth s of up to 500 m can be present.
Also shown is an arrangement for inductive heating of the
reservoir section 100. This can be formed by a long, i.e. a
few 100 m to 1.5 km, conductor loop 120 to 121 laid in the
ground, wherein the outwards conductor 120 and return
conductor 121 are routed next to one another, i.e. at the same
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depth, and are connected to one another at the end via an
element 15 inside or outside the reservoir. At the start the
conductors 120 and 121 are routed vertically or at a slight
angle downwards and are supplied with electrical power by a
high-frequency generator 60 which can be accommodated in an
external housing. The high-frequency generator 60 or medium-
frequency generator preferably covers a range of 10 kHz to
200 kHz or a sub range thereto and can preferably be set to
any given frequencies in this frequency range. Also
conceivable is an operating range of 1 kHz to 500 kHz.
In Figure 11 the conductors 120 and 121 run next to one
another at the same depth. They can also be routed above one
another. Below the conductor loop (i.e. the conductor 120 and
121), i.e. on the floor of the reservoir unit 100, an
extraction pipe 102 is shown, via which the liquefied bitumen
or heavy oil can be collected and/or transported away.
Typical distances between the outwards and return conductors
120, 121 are 5 to 60 m for an external diameter of the
conductors of 10 to 50 cm (0.1 to 0.5 m).
The outwards conductor 120 and the return conductor 121 from
Figure 11 are, at least in the area of their largely
horizontal extent, preferably embodied with interruptions in
accordance with Figures 1 to 10.
Typical operating parameters are for example an inductively
introduced heating power of 1 kW per meter of double
conductor. A current amplitude of 300 A to 1000 A can be
provided for example. An individual wire can for example have
a diameter of 0.5 to 1 mm. Overall the wires in the inductor
can have a cross-section of 1000 to 1500 mm2. For example the
inductor can consist of 2500 to 3500 individual massive wires.
Copper can be provided as the material for the wires. Teflon
can be provided for example as insulation for each individual
wire. Wall thicknesses of the insulation can for example
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amount to 0.2 to 0.3 mm. The doubled resonance length through
typical inductor can e.g. amount to 35 to 50 m. The wires are
arranged in the longitudinal direction with an offset of the
interruption points by the resonance length.
The invention in accordance with the figures relates to an
arrangement and a method for application of heat to a
geological formation, especially to a reservoir present in a
geological formation, especially for recovering a substance
containing hydrocarbons - especially crude oil - from the
reservoir. An inductor is proposed which is designed for
in-situ extraction with underground reservoirs, approximately
as from a depth of around 75 m. this means that with this
technique the oil sand - i.e. the sand and the stone with the
oil contained therein - remains in place. The oil or the
bitumen is separated from the grains of sand by means of
electromagnetic waves and possibly further different methods
and is made more filowahle, so that it can be extracted. The
"in-situ" method presented has the principle of increasing the
temperature underground and thus reducing the viscosity of the
bound oil or of the bitumen and making it more flowable in
order to subsequently pump it out. The heating effect
especially causes the long-chain hydrocarbons of the highly-
viscous which in to fracture. The inductor - i.e. an
electrical conductor which is embodied as an induction line -
can be operated with low losses as a resonant circuit. Since
preferably both ends cf the inductor are connected to the
frequency generator, the induction line forms an induction
loop. The technical realization of the electrical line is
carried out as a resonant circuit. The frequency generator can
preferably be embodied as a frequency converter, which
converts a frequency of 50Hz or 60Hz from the mains into a
voltage with a frequency in the range of 1 kHz to 500 kHz. The
frequency converter can be installed on the surface.
Furthermore in the reservoir zone heated by the induction loop
preferably at least one extracLion hole can be drilled. In
addition at least one injection hole for injection of hot
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steam can be provided optionally between two continuous quasi-
parallel holes in which the induction loop is disposed.
After the inductor has been laid as an induction loop into at
least two holes and the induction loop has been connected to
the frequency generator, the supply of power to the conductor
begins in operation and thus the inductive heating underground
with the resultant formation of a heating zone which is
characterized by an increased temperature. The conductor loop
or induction loop acts in operation as an induction hearer in
order to introduce additional heat into the reservoir. The
active area of the conductor, in the essentially horizontal
direction within the reservoir, can describe a practically
closed loop (i.e. an oval). An end area - possibly laid above
ground - can be joined to the active area. The parts of the
start and end area of the conductor laid above ground can be
electrically contacted with a current source - the frequency
generator. There is preferably provision to compensate for the
line inductivity of the conductor in sections by series
capacitances. In this case there can be provision for the line
with integrated compensation that the frequency of the
frequency generator is tuned to the resonant frequency of the
current loop. The capacitance in the conductor can be formed
between cable sections. A dielectric present can be selected
in such cases such that it fulfills the requirement for a high
dielectric strength and a high temperature resistance.
Insulation of the inductor from the surrounding soil is
advantageous in order to prevent resistive currents through
the soil between the adjacent cable sections, especially in
the area of the capacitors. The insulation further prevents a
resistive current flow between outwards and return conductor.
The longitudinal inductance can be compensated for in
operation by means of cross capacitances. The capacitance per
unit length - which a two-wire line, such as for example a
coaxial line or multi-wire line, provides over its entire
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length in any event - can be used to compensate for the
longitudinal inductances. For this purpose the inner and outer
conductor are interrupted at equal distances alternately and
thus the current flow is forced via the distributed cross
capacitances.
The temperature in operation in the heating zone depends on
the introduced electromagnetic power, which is produced by the
geological and physical (e.g. electrical conductivity)
parameters of the reservoir and also the technical parameters
of the electrical arrangement, especially consisting of the
inductor and the high-frequency generator. This temperature
can reach up to 300 C and is able to be regulated by changing
the current strength through the loop of the inductor. The
regulation is undertaken via the frequency generator. The
electrical conductivity of the reservoir can be increased by
additional injection of water or of another fluid, e.g. an
electrolyte.
The temperature initially develops as a result of the
induction of eddy currents into the electrically conductive
underground areas. During the course of the heating
temperature gradients arise, meaning locations at a higher
temperature than the original reservoir temperature. The
higher temperature locations occur where eddy currents are
induced. The output point of the heat is therefore not the
induction loop or the electrical conductor but is the eddy
currents induced by the electromagnetic field in the
electrically-conductive layer. Through the temperature
gradients arising over the course of time, depending on the
thermal parameters such as thermal conductivity, thermal
transfer also arises, through which the temperature profile
equalizes. With a greater distance to the conductor the
strength of the alternating field reduces so that only a
lesser heating is made possible there.
2014P11308
CA 02949555 2016-11-18
38
If on the other hand the fluids or the electrically-conductive
liquids made fluid are transported away immediately as soon as
they have been made fluid, then at the emptied points there is
less heating by electrical eddy currents the more the soil
with its electrical conductivity has been also transported
away. Although the electromagnetic field is still there, Eddy
currents can only form however where there is still
conductivity present. However a flowing away of a liquid can
have the effect of another liquid flowing in.
The power provided is preferably set to between 100 kW and
several megawatts.
The invention merely relates to one inductor. However a number
of inductors next to one another and at a distance from one
another can be laid in a reservoir, depending on its size.
Although the invention has been illustrated in greater detail
and described by exemplary embodiments, the invention is not
restricted by the disclosed examples and other variat_ions can
be derived herefrom by the person skilled in the art without
departing from the scope of protection of the invention.
