TECHNICAL FIELD
[0001] The present disclosure generally relates to high voltage DC power cables.
BACKGROUND
[0002] Some high voltage DC power cables have non-solid conductors, in the following referred
to as multi-wire conductors. Multi-wire conductors are made by stranding a plurality
of wires. Such wires may for example have a circular or elliptical cross-section,
or they may have other shapes, such as in the case of keystone or profiled conductors.
[0003] The filling grade of the wires is typically in the range of 92%-96%, with the lower
figure being typical for stranded round wire conductors and the higher figure being
typical for keystone conductors. Since the filling grade is not 100%, there is a risk
that water may migrate longitudinally into the interstices between the wires for example
after a cable fault.
[0004] High voltage DC power cables on the market today use water swelling tapes to prevent
longitudinal migration of water after a cable fault or in the case of defects in the
end caps during transport or installation of the cable, which may lead to water ingression.
The water swelling tape may be provided between layers of the conductor wires and/or
around the conductor.
[0005] US 4095039 A discloses a power cable with a stranded conductor to which a semi-conducting conductor
shield is applied. A layer of insulation, preferably polyethylene surrounds the conductor
shield, and a semi-conducting insulation shield is arranged around the outside of
the insulation. A filler material fills all spaces of the stranded conductor. The
filler material is a compound of low molecular weight polyisobutylene rubber or a
low molecular weight copolymer of isobutylene-isoprene rubber.
[0006] WO 2016/206715 A1 discloses a water blocking material in the conductor of an HVDC cable in the form
of a yarn incorporated between the strands of the conductor. The yarn is laid mainly
in the longitudinal direction with the same lay direction as the strands. Alternatively,
the water blocking material could be in the form of a water absorbent powder or the
powder could be included in the conductor by means of a tape comprising the powder.
[0007] US4703132 A discloses a water migration resisting filler for filling the interstices of a stranded
conductor, an electrical power transmission cable including such filler and a method
of making such cable. The filler includes a polymeric compound having a 100 gram needle
penetration value between 50 and 100 tenths of a millimeter at 25 degrees C, and particles
of a water swellable material having a particle size of not greater than 200 microns
are in contact with the polymeric compound either by admixing it with the compound
or applying it to the surface thereof. In the method, the polymeric compound is flowed
around the wires of the conductor as they are stranded together and the water swellable
material is either admixed with the compound or applied thereto as the conductor is
formed, a semi-conductive layer is extruded around the so-filled conductor and a layer
of insulation is extruded around the semi-conductive layer.
[0008] US4130450 A discloses high-voltage power cables with extruded dielectric plastic insulation,
installed underground, have their life shortened by the formation of electrochemical
trees in the insulation. The high-voltage power transmission cable is constructed
with sealant in interstices of a stranded conductor that are not filled by the semi-conducting
material of a conductor shield of the cable.
[0009] WO9636054 A1 discloses a power transmission cable and method of making such cable including first
and second filling compounds which function to prevent degradation in cable performance
as a result of the permeation of water through the polyethylene sheath (14) of the
cable (10) and which do not liquefy at high temperature.
SUMMARY
[0010] One drawback with water swelling tapes is that they may release components that migrate
into the solid insulation system of the power cable. These components could potentially
contaminate the solid insulation system. In contrast to AC cables, it is especially
important for high voltage DC cables that the solid insulation system is kept as contamination
free as possible, to ensure a long lifetime of the power cable.
[0011] The present inventors have found that these issues start to become a problem for
high voltage DC power cables operating at voltages of 320 kV or higher. The electric
field across the insulation is in this case so high that the insulation material may
due to the contamination become conductive enough to increase the temperature of the
insulation to undesirable levels at which it degrades over time.
[0012] In view of the above, an object of the present disclosure is to provide a high voltage
DC power cable which solves or at least mitigates existing problems of the state of
the art.
[0013] There is hence provided a high voltage DC power cable designed for voltages of 320
kV or higher, comprising: a multi-wire conductor, an inner semiconducting layer arranged
around the multi-wire conductor, the inner semiconducting layer forming a screen layer
for the multi-wire conductor, a solid insulation system arranged around the inner
semiconducting layer, and a water-blocking compound configured to restrict water migration
into the high voltage DC power cable.
[0014] The water-blocking compound provides longitudinal water-tightness, preventing water
to migrate into the high voltage DC power cable. This may be achieved without providing
water swellable tape around the multi-wire conductor, or between layers of wires of
the multi-wire conductor.
[0015] By achieving a water-blocking functionality without using water swellable tapes,
which contain by-products from production that may migrate into the solid insulation
system, the solid insulation system may be made free or essentially free of contaminants.
Thereby, the performance of the solid insulation system and hence of the high voltage
DC power cable may be improved.
[0016] That the high voltage DC power cable is designed for voltages of 320 kV or higher
means that the solid insulation system is made of a material specifically configured
to withstand voltage levels of 320 kV or higher and that the solid insulation system
is dimensioned to handle these voltage levels.
[0017] The water-blocking compound may be configured to restrict water migration into the
multi-wire conductor. The water-blocking compound may be configured to restrict water
migration into interstices between the wires of the multi-wire conductor.
[0018] According to one embodiment the water-blocking compound is provided in interstices
between the wires of the multi-wire conductor. Water is thereby not able to migrate
longitudinally in between the wires.
[0019] According to one embodiment the water-blocking compound is provided radially outwards
of and around the solid insulation system.
[0020] The high voltage DC power cable may comprise an outer semiconducting layer provided
around the solid insulation system. The water-blocking compound may for example be
provided on the external surface of the outer semiconducting layer.
[0021] The high voltage DC power cable may comprise screen wires arranged radially outwards
of the outer semiconducting layer. The water-blocking compound may for example be
provided between the screen wires and/or over the screen wires.
[0022] According to one example, the water-blocking compound may be provided in the interstices
between the wires of the multi-wire conductor and radially outwards of and around
the solid insulation system.
[0023] The water-blocking compound may be provided to obtain a filling grade of the multi-wire
conductor in the range of 98%-100%, such as 99%-100%, such as over 99% to 100%, or
even a 100% filling grade.
[0024] The water-blocking compound may be provided in interstices between the perimeter
of the multi-wire conductor and the inner semiconducting layer. The water-blocking
compound may be hydrophobic.
[0025] The water-blocking compound may contain a hydrophilic swelling agent. According to
one embodiment the water-blocking compound comprises a hydrocarbon-based component
or a silica-based component.
[0026] The water-blocking compound is a liquid with a viscosity greater than 20
Pa ·
s at a temperature of 20
o C.
[0027] According to one embodiment the solid insulation system is composed of an electrically
insulating material which has an electrical conductivity of at most 1000 fS/m, at
most 100 fS/m, or at most 10 fS/m measured at nominal voltage at a temperature of
20° C. These characteristics are measured on the electrically insulating material
of the high voltage DC power cable.
[0028] The higher the electrical conductivity of the electrically insulating material the
smaller the influence of a water-blocking swelling tape, because electrically insulating
materials with a high electrical conductivity will carry charges under high enough
electrical fields and thus heat the electrically insulating material even without
contamination. Electrically insulating materials with a higher electrical conductivity
are therefore less sensitive to contamination than electrically insulating materials
with lower electrical conductivity.
[0029] Because of the water-blocking compound, which reduces the risk of contamination of
the solid insulation system, electrically insulating materials with lower electrical
conductivity, preferably not higher than 200 fS/m such as not higher than 150 fS/m,
may be used in the high voltage DC power cable. According to one embodiment the solid
insulation system is composed of an electrically insulating material which has the
inherent property that a non-heat treated 1 mm thick press-moulded plate made from
the electrically insulating material has an electrical conductivity of at most 50
fS/m measured after 24 hours at 70° C and an electric field of 30 kV/mm applied across
the thickness dimension of the press-moulded plate.
[0030] The measurement of the electrical conductivity is thus performed after the press-moulded
plate has been continuously subjected to an electric field of 30 kV/mm at 70° C for
24 hours.
[0031] The press-moulded plate may for example be made from granules composed of the electrically
insulating material, which are placed in a mould to form the plate.
[0032] The solid insulation system may comprise a thermoset such as cross-linked polyethylene
(XLPE) or a thermoplastic such as polypropylene. The solid insulation system comprising
polypropylene may according to one example not be cross-linked.
[0033] According to the invention the water-blocking compound is electrically conducting.
Electrical contact is hence provided between the layers separated by the compound.
There may for example be attained an electrical contact between the multi-wire conductor
and the inner semiconducting layer, or between an outer semiconducting layer and screen
wires. In this manner, there will be no or essentially no potential difference between
e.g. the wires of the multi-wire conductor and the inner semiconducting layer, or
between the outer semiconducting layer and the screen wires.
[0034] According to the invention the water-blocking compound comprises a carbon-based component
which provides the electric conductivity of the water-blocking compound.
[0035] According to the invention the carbon-based component is graphite.
[0036] One embodiment comprises an electrically conducting or an electrically non-conducting
tape wound around the multi-wire conductor and arranged between the multi-wire conductor
and the inner semiconducting layer.
[0037] The tape may prevent the water-blocking medium to contaminate the cable production
line during manufacturing of the high voltage DC power cable. The tape may also prevent
accumulation of water-blocking compound, which thereby could turn into lumps that
protrude into the inner semiconducting layer and the solid insulation system.
[0038] The tape may according to one example have water-blocking capability.
[0039] The tape does preferably not contain any swelling agent.
[0040] According to one embodiment the tape is in direct contact with the multi-wire conductor
and/or the water-blocking compound and with the inner semiconducting layer.
[0041] According to one embodiment the multi-wire conductor is formed by a plurality of
layers of wires, wherein the water-blocking compound is provided in interstices between
each layer of wires.
[0042] According to one embodiment the water-blocking compound is provided on an outermost
layer of wires of the multi-wire conductor.
[0043] According to the invention the water-blocking compound comprises polybutadiene, an
antioxidant, and graphite. This compound does not contaminate the solid insulation
system.
[0044] According to one embodiment the solid insulation system is partially cross-linked
so that it only passes a hot set test according to IEC 60811-507 up to 50% of the
load specified by IEC 60811-507.
[0045] The load specified by IEC 60811-507 is 20 N/cm
2.
[0046] According to one embodiment the solid insulation system is partially cross-linked
so that it only passes a hot set test according to IEC 60811-507 up to 40%, such as
up to 30%, such as up to 25%, of the load specified by IEC 60811-507.
[0047] According to one embodiment the solid insulation system comprises a thermoplastic
polypropylene-based material.
[0048] According to one embodiment the water-blocking compound is a water-blocking or water-absorbing
compound.
[0049] The high voltage DC power cable may be a land cable or a submarine cable. There is
according to a second aspect of the present disclosure provided a method of manufacturing
a high voltage DC power cable according to the first aspect, wherein the method comprises:
providing the water-blocking compound internally in the high voltage DC power cable
to restrict water migration into the high voltage DC power cable.
[0050] The method may for example comprise: stranding a plurality of wires to form the multi-wire
conductor, wherein the stranding involves providing the water-blocking compound between
each layer of wires, and extruding the inner semiconducting layer and the solid insulation
system onto the multi-wire conductor.
[0051] Generally, all terms used in the claims are to be interpreted according to their
ordinary meaning in the technical field, unless explicitly defined otherwise herein.
All references to "a/an/the element, apparatus, component, means, etc. are to be interpreted
openly as referring to at least one instance of the element, apparatus, component,
means, etc.", unless explicitly stated otherwise.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] The specific embodiments of the inventive concept will now be described, by way of
example, with reference to the accompanying drawings, in which:
Fig. 1 schematically shows a cross-section of an example of a high voltage DC power
cable;
Fig. 2 schematically shows a cross-section of another example of a high voltage DC
power cable;
Fig. 3 schematically shows a cross-section of yet another example of a high voltage
DC power cable; and
Fig. 4 is a flowchart of a method of manufacturing a high voltage DC power cable.
DETAILED DESCRIPTION
[0053] The inventive concept will now be described more fully hereinafter with reference
to the accompanying drawings, in which exemplifying embodiments are shown. The inventive
concept may, however, be embodied in many different forms and should not be construed
as limited to the embodiments set forth herein; rather, these embodiments are provided
by way of example so that this disclosure will be thorough and complete, and will
fully convey the scope of the inventive concept as defined by the appended claims
to those skilled in the art.
[0054] Like numbers refer to like elements throughout the description.
[0055] Fig. 1 schematically shows a cross-section of an example of a high voltage DC (HVDC)
power cable 1-1. The exemplified HVDC power cable 1-1 is a land cable but could alternatively
be a submarine power cable. In the latter case, the general structure of the HVDC
power cable would be somewhat different, as it would be configured for underwater
use and e.g. comprise a water-blocking sheath and optionally armouring. The HVDC power
cable 1-1 is designed to have a voltage rating equal to or greater than 320 kV.
[0056] The HVDC power cable 1-1 comprises a multi-wire conductor 3. The multi-wire conductor
3 comprises a plurality of wires 3a. The wires 3a are arranged in a stranded configuration.
The multi-wire conductor 3 has interstices between the wires 3a. The fill-factor of
the multi-wire conductor 3 as provided by the wires may for example be in the range
92-96%. This means that the conductor material fills 92-96% of the cross-sectional
area of the multi-wire conductor 3.
[0057] In the present example, the stranded wires 3a are rounded wires and the multi-wire
conductor 3a is a stranded round conductor. The multi-wire conductor could alternatively
for example be a keystone or profiled conductor, or a segmental or Milliken conductor.
[0058] The exemplified HVDC power cable 1-1 comprises an inner semiconducting layer 5. The
inner semiconducting layer 5 is provided around the multi-wire conductor 3. The inner
semiconducting layer 5 acts as a conductor screen. The inner semiconducting layer
5 hence forms a screen layer for the multi-wire conductor 3. The exemplified inner
semiconducting layer 5 may be polymer-based and may comprise a conductive component
such as carbon black.
[0059] The HVDC power cable 1-1 comprises a solid insulation system 7. The solid insulation
system 7 is an electrical insulation system. The solid insulation system 7 is provided
around the inner semiconducting layer 5. The solid insulation system 7 is hence arranged
radially outwards of the inner semiconducting layer 5.
[0060] The solid insulation system 7 is composed of, or comprises, an electrically insulating
material which has an electrical conductivity of for example at most 1000 femto Siemens
(fS)/m, such as at most 100 fS/m, or at most 10 fS/m, measured at nominal voltage
at a temperature of 20° C.
[0061] The solid insulation system 7 may be partially cross-linked so that it only passes
a hot set test according to IEC 60811-507 up to 50% of the load specified by IEC 60811-507.
The solid insulation system 7 thus fails the hot set test according to IEC 60811-507
when the load is larger than 50% of the load specified by IEC 60811-507.
[0062] The standard IEC 60811-507 referred to is Edition 1.0 of 2012-03.
[0063] The solid insulation system 7 may be partially cross-linked so that it only passes
a hot set test according to IEC 60811-507 up to 40%, such as up to 30%, such as up
to 25% of the load specified by IEC 60811-507.
[0064] An example of a compound with this property is LS4258DCE by Borealis.
[0065] The solid insulation system 7 may be polymer-based. The solid insulation system 7
may for example comprise cross-linked polyethylene, or polypropylene.
[0066] The HVDC power cable 1-1 comprises an outer semiconducting layer 9. The outer semiconducting
layer 9 is provided around the solid insulation system 7. The outer semiconducting
layer 9 is hence arranged radially outwards of the solid insulation system 7. The
solid insulation system 7 is sandwiched between the inner semiconducting layer 5 and
the outer semiconducting layer 9.
[0067] The outer semiconducting layer 9 acts as an insulation screen for the solid insulation
system 7. The exemplified outer semiconducting layer 9 may be polymer-based and may
comprise a conductive component such as carbon black.
[0068] The HVDC power cable 1-1 may comprise a metallic screen 11. The metallic screen 11
may be provided around the outer semiconducting layer 9. The metallic screen 11 may
for example comprise copper. The metallic screen 11 may comprise a plurality of screen
wires 11a. The screen wires 11a may be distributed along the perimeter of the outer
semiconducting layer 9. The screen wires 11a may be helically wound around the outer
semiconducting layer 9. The screen wires 11a may for example comprise copper.
[0069] The HVDC power cable 1-1 has an outer serving or sheath 13 covering the metallic
screen 11. The outer serving or sheath 13 forms the outermost layer of the HVDC power
cable 1-1. The outer serving or sheath 13 may for example comprise a polymeric material.
[0070] The HVDC power cable 1-1 comprises a water-blocking compound 15. The water-blocking
compound 15 is arranged to restrict water migration into the HVDC power cable 1-1.
[0071] Fig. 1 shows one example of the configuration of the water-blocking compound 15 in
the HVDC power cable 1-1. The water-blocking compound 15 is arranged between the interstices
of the wires 3a. The wires 3a are arranged in layers, and the interstices in and between
all layers may be filled with the water-blocking compound 15. All the interstices
between the wires 3a of the multi-wire conductor 3 are hence filled with the water-blocking
compound 15. The water-blocking compound 15 is arranged radially outside of the multi-wire
conductor 3, on the outer surface of the outermost layer of the wires 3a. Water is
hence prevented to migrate longitudinal in the interstices of the multi-wire conductor
3.
[0072] The water-blocking compound 15 is a liquid. The water-blocking compound 15 has a
viscosity equal to or greater than 20 Pa*s.
[0073] The water-blocking compound 15 may according to one example not forming part of the
current invention be a solid with a Shore D less than 65 at a temperature of 20° C.
[0074] The water-blocking compound 15 is electrically conducting. The water-blocking compound
15 comprises a carbon-based component which makes the water-blocking compound 15 electrically
conducting. The carbon-based component is graphite.
[0075] The water-blocking compound 15 may be hydrocarbon-based on silica-based.
[0076] The water-blocking compound 15 may comprise a hydrocarbon-based component or a silica-based
component. The water-blocking compound 15 comprises polybutadiene, an antioxidant,
and graphite. The water-blocking compound 15 may be hydrophobic or hydrophilic. The
water-blocking compound 15 may according to one example comprise a swelling agent.
[0077] Fig. 2 shows a cross-section of another example of an HVDC power cable 1-2.
[0078] The general structure of the HVDC power cable 1-2 is similar to the HVDC power cable
1-1. The HVDC power cable 1-2 however comprises a tape 17. The tape 17 is wound around
the multi-wire conductor 3. The tape 17 may be wound around the multi-wire conductor
3 along the entire length of the multi-wire conductor 3. The tape 17 may be electrically
conducting or electrically non-conducting/electrically insulating. The tape 17 may
for example comprise a polymer. The tape 17 is arranged between the multi-wire conductor
3 and the inner semiconducting layer 5. The tape 17 may be in direct contact with
the inner surface of the inner semiconducting layer 5. The tap 17 may be in direct
contact with the multi-wire conductor 3 and/or with the water-blocking compound 15.
[0079] Fig. 3 shows a cross-section of an example of an HVDC power cable 1-3. The structure
of the HVDC power cable 1-3 is similar to the HVDC power cable 1-1. The HVDC power
cable 1-2 has the water-blocking compound 15 provided in the interstices between the
screen wires 11a. The water-blocking compound 15 is also provided on the outer surface
of the screen wires 11a. The water-blocking compound 15 may in this example optionally
also be provided in the interstices between the wires 3a of the multi-wire conductor
3.
[0080] The water-blocking compound 15 could according to one variation be provided directly
on the outer surface of the outer semiconducting layer 9 instead of around/between
the interstices of the screen wires 11a.
[0081] The HVDC power cable 1-3 may according to one variation include a tape wound around
the outer semiconducting layer. The tape may for example be wound around the screen
wires 11a. The water-blocking compound may according to one example at least partly
be in direct contact with the tape.
[0082] Fig. 4 shows a flowchart of a method of manufacturing an HVDC power cable such as
HVDC power cable 1-1 to 1-3. The method in general comprises providing the water-blocking
compound 15 internally in the HVDC power cable 1-1 to 1-3 to restrict water migration
into the HVDC power cable 1-1 to 1-3.
[0083] For the HVDC power cables 1-1 and 1-2, the providing of the water-blocking compound
15 internally comprises a) stranding the plurality of wires 3a to form the multi-wire
conductor 3. The stranding involves providing the water-blocking compound 15 between
each layer of wires 3a. This may be achieved during the stranding process, as the
stranding machine strands the wires 3a layer by layer. The stranding may furthermore
involve providing the water-blocking compound 15 on the outermost layer, on the outer
surface, of the wires 3a. The method may further comprise b) extruding the inner semiconducting
layer 5 and the solid insulation system 7 onto the multi-wire conductor 3, which has
had its interstices/spaces between the wires 3a provided with the water-blocking compound
15. The outer semiconducting layer 9 is extruded on the solid insulation system 7.
The extrusion may be a triple-extrusion process, in which the inner semiconducting
layer 5, the solid insulation system 7 and the outer semiconducting layer 9 are co-extruded.
[0084] For the HVDC cable 1-3, the providing of the water-blocking compound 15 involves
providing it onto and in between the screen wires 11a.
[0085] All the HVDC power cables 1-1 to 1-3 disclosed herein may be free of water swelling
tape.
[0086] The inventive concept has mainly been described above with reference to a few examples.
However, as is readily appreciated by a person skilled in the art, other embodiments
than the ones disclosed above are equally possible within the scope of the inventive
concept, as defined by the appended claims.
1. A high voltage DC power cable (1-1; 1-2; 1-3) designed for voltages of 320 kV or higher,
comprising:
a multi-wire conductor (3),
an inner semiconducting layer (5) arranged around the multi-wire conductor (3), the
inner semiconducting layer (5) forming a screen layer for the multi-wire conductor
(3),
a solid insulation system (7) arranged around the inner semiconducting layer (5),
and
a water-blocking compound (15) configured to restrict water migration into the high
voltage DC power cable (1-1; 1-2; 1-3), wherein the water-blocking compound (15) is
electrically conducting,
characterised in that the water-blocking compound (15) is a liquid with a viscosity greater than 20 Pα·s at a temperature of 20°C, and
in that the water-blocking compound (15) comprises a carbon-based component which provides
the electric conductivity of the water-blocking compound (15), wherein the carbon-based
component is graphite, wherein the water-blocking compound (15) comprises polybutadiene,
and an antioxidant.
2. The high voltage DC power cable (1-1; 1-2) as claimed in claim 1, wherein the water-blocking
compound (15) is provided in interstices between the wires (3a) of the multi-wire
conductor (3).
3. The high voltage DC power cable (1-3) as claimed in claim 1, wherein the water-blocking
compound (15) is provided radially outwards of and around the solid insulation system
(7).
4. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, wherein the water-blocking compound (15) comprises a hydrocarbon-based component
or a silica-based component.
5. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, wherein the solid insulation system (7) is composed of an electrically insulating
material which has an electrical conductivity of at most 1000 fS/m, at most 100 fS/m,
or at most 10 fS/m measured at nominal voltage at a temperature of 20° C.
6. The high voltage DC power cable as claimed in any of claims 1-4, wherein the solid
insulation system (7) is composed of an electrically insulating material which has
the inherent property that a non-heat treated 1 mm thick press-moulded plate made
from the electrically insulating material has an electrical conductivity of at most
50 fS/m measured after 24 hours at 70° C and an electric field of 30 kV/mm applied
across the thickness dimension of the press-moulded plate.
7. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, comprising an electrically conducting or an electrically non-conducting tape
(17) wound around the multi-wire conductor (3) and arranged between the multi-wire
conductor (3) and the inner semiconducting layer (5).
8. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in claim 7, wherein the
tape (17) is in direct contact with the multi-wire conductor (3) and/or the water-blocking
compound (15) and with the inner semiconducting layer (5).
9. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, wherein the multi-wire conductor (3) is formed by a plurality of layers of
wires (3a), wherein the water-blocking compound (15) is provided in interstices between
each layer of wires (3a).
10. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, wherein the water-blocking compound (15) is provided on an outermost layer
of wires (3a) of the multi-wire conductor (3).
11. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of the preceding
claims, wherein the solid insulation system (7) is partially cross-linked so that
it only passes a hot set test according to IEC 60811-507 up to 50% of the load specified
by IEC 60811-507.
12. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in claim 11, wherein the
solid insulation system (7) is partially cross-linked so that it only passes a hot
set test according to IEC 60811-507 up to 40%, such as up to 30%, such as up to 25%,
of the load specified by IEC 60811-507.
13. The high voltage DC power cable (1-1; 1-2; 1-3) as claimed in any of claims 1-11,
wherein the solid insulation system (7) comprises a thermoplastic polypropylene-based
material.
1. Hochspannungs-(HV-)-DC-Stromkabel (1-1; 1-2; 1-3), das für Spannungen von 320 kV oder
höher ausgelegt ist, umfassend:
einen Mehrdrahtleiter (3),
eine innere Halbleiterschicht (5), die um den Mehrdrahtleiter (3) angeordnet ist,
wobei die innere halbleitende Schicht (5) eine Abschirmschicht für den Mehrdrahtleiter
(3) bildet,
ein festes Isolationssystem (7), das um die innere Halbleiterschicht (5) angeordnet
ist, und
eine Wassersperrverbindung (15), die so konfiguriert ist, dass sie die Wassermigration
in das HVDC-Stromkabel (1-1; 1-2; 1-3) einschränkt, wobei die Wassersperrverbindung
(15) elektrisch leitend ist,
dadurch gekennzeichnet, dass die Wassersperrverbindung (15) eine Flüssigkeit mit einer Viskosität von mehr als
20 Pα · s bei einer Temperatur von 20 °C ist, und
dass die Wassersperrverbindung (15) eine Komponente auf Kohlenstoffbasis umfasst,
die die elektrische Leitfähigkeit der Wassersperrverbindung (15) bereitstellt, wobei
die kohlenstoffbasierte Komponente Graphit ist, wobei die Wassersperrverbindung (15)
Polybutadien und ein Antioxidationsmittel umfasst.
2. HVDC-Stromkabel (1-1; 1-2) nach Anspruch 1, wobei die Wassersperrverbindung (15) in
Zwischenräumen zwischen den Drähten (3a) des Mehrdrahtleiters (3) bereitgestellt ist.
3. HVDC-Stromkabel (1-3) nach Anspruch 1, wobei die Wassersperrverbindung (15) radial
außerhalb des festen Isolationssystems (7) und um dieses bereitgestellt ist.
4. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, wobei die
Wassersperrverbindung (15) eine kohlenwasserstoffbasierte Komponente oder eine Komponente
auf Siliziumdioxidbasis umfasst.
5. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, wobei das
feste Isoliersystem (7) aus einem elektrischen Isoliermaterial besteht, das eine elektrische
Leitfähigkeit von höchstens 1000 fS/m, höchstens 100 fS/m oder höchstens 10 fS/m,
gemessen bei Nennspannung bei einer Temperatur von 20 °C, aufweist.
6. HVDC-Stromkabel nach einem der Ansprüche 1 bis 4, wobei das feste Isoliersystem (7)
aus einem elektrischen Isoliermaterial besteht, das die inhärente Eigenschaft aufweist,
dass eine nicht wärmebehandelte, 1 mm dicke, aus dem elektrischen Isoliermaterial
gepresste Platte eine elektrische Leitfähigkeit von höchstens 50 fS/m aufweist, gemessen
nach 24 Stunden bei 70 °C und einem elektrischen Feld von 30 kV/mm, das über die Dickenabmessung
der gepressten Platte angelegt wird.
7. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, mit einem
elektrisch leitenden oder einem elektrisch nicht leitenden Band (17), das um den Mehrdrahtleiter
(3) gewickelt und zwischen dem Mehrdrahtleiter (3) und der inneren Halbleiterschicht
(5) angeordnet ist.
8. HVDC-Stromkabel (1-1; 1-2; 1-3) nach Anspruch 7, wobei das Band (17) in direktem Kontakt
mit dem Mehrdrahtleiter (3) und/oder der Wassersperrverbindung (15) und mit der inneren
Halbleiterschicht (5) steht.
9. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, wobei der
Mehrdrahtleiter (3) durch eine Vielzahl von Schichten von Drähten (3a) gebildet ist,
wobei die Wassersperrverbindung (15) in Zwischenräumen zwischen jeder Schicht von
Drähten (3a) bereitgestellt ist.
10. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, wobei die
Wassersperrverbindung (15) auf einer äußersten Schicht von Drähten (3a) des Mehrdrahtleiters
(3) bereitgestellt ist.
11. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der vorhergehenden Ansprüche, wobei das
feste Isoliersystem (7) teilweise vernetzt ist, so dass es eine Wärmedehnungsprüfung
gemäß IEC 60811-507 nur bis zu 50 % der durch IEC 60811-507 spezifizierten Last besteht.
12. HVDC-Stromkabel (1-1; 1-2; 1-3) nach Anspruch 11, wobei das feste Isoliersystem (7)
teilweise vernetzt ist, so dass es eine Wärmedehnungsprüfung gemäß IEC 60811-507 nur
bis zu 40 %, wie etwa bis zu 30 %, wie etwa bis zu 25 %, der durch IEC 60811-507 spezifizierten
Last besteht.
13. HVDC-Stromkabel (1-1; 1-2; 1-3) nach einem der Ansprüche 1 bis 11, wobei das feste
Isoliersystem (7) ein thermoplastisches Material auf Polypropylenbasis umfasst.
1. Câble d'alimentation CC à haute tension (1-1 ; 1-2 ; 1-3) conçu pour des tensions
de 320 kV ou plus, comprenant :
un conducteur multifil (3),
une couche semiconductrice intérieure (5) agencée autour du conducteur multifil (3),
la couche semiconductrice intérieure (5) formant une couche écran pour le conducteur
multifil (3),
un système d'isolation solide (7) agencé autour de la couche semiconductrice intérieure
(5), et
un composé de blocage d'eau (15) configuré pour interdire toute migration d'eau dans
le câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3), dans lequel le composé
de blocage d'eau (15) est électriquement conducteur,
caractérisé en ce que le composé de blocage d'eau (15) est un liquide avec une viscosité supérieure à 20
Pa.s à une température de 20°C, et
en ce que le composé de blocage d'eau (15) comprend un composant à base de carbone qui assure
la conductivité électrique du composé de blocage d'eau (15), dans lequel le composant
à base de carbone est du graphite, dans lequel le composé de blocage d'eau (15) comprend
du polybutadiène, et un antioxydant.
2. Câble d'alimentation CC à haute tension (1-1 ; 1-2) selon la revendication 1, dans
lequel le composé de blocage d'eau (15) est fourni dans des interstices entre les
fils (3a) du conducteur multifil (3).
3. Câble d'alimentation CC à haute tension (1-3) selon la revendication 1, dans lequel
le composé de blocage d'eau (15) est fourni radialement vers l'extérieur du système
d'isolation solide (7) et autour de celui-ci.
4. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, dans lequel le composé de blocage d'eau (15) comprend
un composant à base d'hydrocarbures ou un composant à base de silice.
5. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, dans lequel le système d'isolation solide (7) est composé
d'un matériau d'isolation électrique présentant une conductivité électrique d'au plus
1000 fS/m, d'au plus 100 fS/m ou d'au plus 10 fS/m mesurée à une tension nominale
à une température de 20°C.
6. Câble d'alimentation CC à haute tension selon l'une quelconque des revendications
1 à 4, dans lequel le système d'isolation solide (7) est composé d'un matériau d'isolation
électrique ayant la propriété inhérente qu'une plaque pressée-moulée d'une épaisseur
de 1 mm non soumise à un traitement thermique et constituée du matériau d'isolation
électrique présente une conductivité électrique d'au plus 50 fS/m mesurée après 24
heures à 70°C et un champ électrique de 30 kV/mm appliqué à travers la dimension d'épaisseur
de la plaque pressée-moulée.
7. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, comprenant un ruban de conduction électrique ou de non-conduction
électrique (17) enroulé autour du conducteur multifil (3) et agencé entre le conducteur
multifil (3) et la couche semiconductrice intérieure (5).
8. Câble d'alimentation CC à haute tension (1-1 ; 1-2 ; 1-3) selon la revendication 7,
dans lequel le ruban (17) est en contact direct avec le conducteur multifil (3) et/ou
le composé de blocage d'eau (15) et avec la couche semiconductrice intérieure (5).
9. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, dans lequel le conducteur multifil (3) est constitué d'une
pluralité de couches de fils (3a), dans lequel le composé de blocage d'eau (15) est
fourni dans des interstices entre chaque couche de fils (3a).
10. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, dans lequel le composé de blocage d'eau (15) est fourni
sur une couche la plus extérieure de fils (30a) du conducteur multifil (3).
11. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications précédentes, dans lequel le système d'isolation solide (7) est partiellement
réticulé de sorte qu'il passe uniquement un essai de fluage à chaud selon CEI 60811-507
jusqu'à 50 % de la charge spécifiée par CEI 60811-507.
12. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon la revendication 11,
dans lequel le système d'isolation solide (7) est partiellement réticulé de sorte
qu'il passe uniquement un essai de fluage à chaud selon CEI 60811-507 jusqu'à 40 %,
comme jusqu'à 30 %, comme jusqu'à 25 %, de la charge spécifiée par CEI 60811-507.
13. Câble d'alimentation CC à haute tension (1-1 ; 1-2; 1-3) selon l'une quelconque des
revendications 1 à 11, dans lequel le système d'isolation solide (7) comprend un matériau
à base de polypropylène thermoplastique.