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WO2000039820A1 - Transformateur haute tension - Google Patents

Transformateur haute tension Download PDF

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Publication number
WO2000039820A1
WO2000039820A1 PCT/EP1999/010509 EP9910509W WO0039820A1 WO 2000039820 A1 WO2000039820 A1 WO 2000039820A1 EP 9910509 W EP9910509 W EP 9910509W WO 0039820 A1 WO0039820 A1 WO 0039820A1
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WO
WIPO (PCT)
Prior art keywords
winding
transformer according
cable
electrically insulating
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP1999/010509
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English (en)
Inventor
Udo Fromm
Christian Sasse
Pär Holmberg
Nicholas Warren
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ABB AB
Original Assignee
ABB AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GBGB9828652.9A external-priority patent/GB9828652D0/en
Priority claimed from GBGB9912610.4A external-priority patent/GB9912610D0/en
Application filed by ABB AB filed Critical ABB AB
Priority to AU27959/00A priority Critical patent/AU2795900A/en
Publication of WO2000039820A1 publication Critical patent/WO2000039820A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F36/00—Transformers with superconductive windings or with windings operating at cryogenic temperature
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

Definitions

  • This invention relates to a high voltage (HV) transformer, having at least one cooled winding, preferably, but not exclusively, a cooled, superconducting winding.
  • HV high voltage
  • the term "high voltage” is intended to mean in excess of 2 kV and preferably in excess of 10 kV.
  • HV induction devices such as electric machines or HV transformers
  • induction devices based on cables are not suited to handling high voltages in combination with low currents. This is because the electrical insulation thickness of a cable is dependent on the cross-sectional area of the conductors. For small conductor cross-sectional areas (i.e. small currents), the electrical insulation is large and the induction device is therefore uneconomic.
  • the present invention seeks to provide an HV transformer having at least one winding formed from a cable having a cooled winding with surrounding electrical insulation.
  • a high voltage transformer including:
  • a cable arranged in at least one loop and comprising electrically conducting means wound about a longitudinal axis of the cable to provide a first winding having adjacent turns electrically insulated from each other and electrically insulating means associated with and surrounding the first winding and within which the electric field of the first winding is contained in use of the transformer;
  • cooling means for cooling at least one of said windings.
  • the present invention makes use of an insulation system, preferably solid insulation based on extruded technology, which surrounds at least the first winding of an integrated HV transformer.
  • an insulation system preferably solid insulation based on extruded technology, which surrounds at least the first winding of an integrated HV transformer.
  • the electrically insulating means comprises an inner layer of semiconducting material in electrical contact with the first winding only at spaced apart intervals along the length of the first winding, an outer layer of semiconducting material at a controlled electrical potential along its length and an intermediate layer of electrically insulating material between the said inner and outer layers.
  • semiconductor material means a material which has a considerably lower conductivity than an electric conductor but which does not have such a low conductivity that it is an electrical insulator.
  • a semiconducting material should have a volume resistivity of from 1 to 10 5 ohm. cm, preferably from 1 to 500 ohm. cm and most preferably from 10 to 100 ohm. cm. e.g 20 ohm. cm.
  • the electrically insulating means is preferably of unitary form with the semiconducting and electrically insulating layers either in close mechanical contact or, more preferably, joined together, e.g. bonded by extrusion.
  • the layers are preferably formed of plastics material having resilient or elastic properties at least during manufacture and assembly at room temperature. This allows the cable to be flexed and shaped into any desired form.
  • thermal and electric loads within the insulation are reduced.
  • the insulating intermediate layer and the semiconducting inner and outer layers should have at least substantially the same coefficients of thermal expansion ( ⁇ .) so that defects caused by different thermal expansions when the layers are subjected to heating or cooling will not arise. Ideally the layers will be extruded together around the or the associated electrically conducting means.
  • the electrically insulating intermediate layer of the electrically insulating means comprises solid thermoplastics material, such as low or high density polyethylene (LDPE or HDPE) ) , polypropylene (PP) , polybutylene (PB) , polymethylpentene (PMP) , ethylene (ethyl) acrylate polymer, cross-linked materials, such as cross- linked polyethylene (XLPE) , or rubber insulation, such as ethylene propylene rubber (EPR) or silicone rubber.
  • the semiconducting inner and outer layers of the electrically insulating means may comprise similar material to the intermediate layer but with conducting particles, such as particles of carbon black or metallic particles, embedded therein. Generally it has been found that a particular insulating material, such as EPR, has similar mechanical properties when containing no, or some, carbon particles.
  • the intermediate layer may be divided into two or more sublayers by one or more additional intermediate layers of semiconducting material.
  • the electric field generated within the cable by the or each winding is confined within the electrical insulation surrounding the winding, preferably between the semiconducting inner and outer layers on the inside and outside of the insulating intermediate layer.
  • the electric field is substantially radial and confined within the intermediate layer.
  • the semiconducting outer layer is designed to act as a screen to prevent losses caused by induced voltages. Induced voltages in the outer layer could be reduced by increasing the resistance of the outer layer.
  • the resistance can be increased by reducing the thickness of the outer layer but the thickness cannot be reduced below a certain minimum thickness.
  • the resistance can also be increased by selecting a material for the layer having a higher resistivity.
  • the semiconducting outer layer is therefore a compromise between a conductor having low resistance and high induced voltage losses but which (at least for the outermost electrical insulation) is easily connected to a controlled potential, typically earth or ground potential, and an insulator which has high resistance with low induced voltage losses but which needs to be connected to the controlled potential along its length.
  • the resistivity p s of the semiconducting outer layer should be within the range ain ⁇ s ⁇ P ma ⁇ / where p min is determined by permissible power loss caused by eddy current losses and resistive losses caused by voltages induced by magnetic flux and p, ⁇ is determined by the requirement for no corona or glow discharge.
  • the semiconducting outer layer may have anisotropic resistive properties, i.e. the resistance in the azi uthal direction is very high to prevent short circuits but is considerably lower in the axial direction.
  • the semiconducting outer layer (or the outermost outer layer if more than one electrically insulating means is provided) to earth potential, or to some other controlled potential, along its length, e.g. by continuous electrical contact with a wire or other conductor along the length of the (outermost) outer layer or by electrical contact at spaced apart intervals along the length of the semiconducting (outermost) outer layer, the need for an outer metal shield and protective sheath to surround the semiconducting (outermost) outer layer is eliminated. The diameter of the cable is thus reduced.
  • the (outermost) outer layer of semiconducting material may be at least partly surrounded by a metal sheath.
  • the sheath should not be completely closed in order not to cause an inductive short circuit. It should have at least one interruption in the form of a slit along the main axis of the induction device (this is the "long" axis defining the centre of the inductor) .
  • the metal sheath could completely surround the sheath provided that overlapping sheath portions are electrically insulated from each other.
  • the metallic sheath should contact the (outermost) outer layer of semiconducting material and be earthed or grounded (or at some other controlled potential) so that the (outermost) outer layer is also at the controlled potential along the length of the cable. If the surrounding sheath is non-metallic (plastics material) , then it may completely enclose the (outermost) outer layer of semiconducting material.
  • the first winding is wound from elongate electrically conducting means having a surrounding electrical insulation, such as varnish.
  • the electrical insulation is removed at spaced apart regions along the length of the conducting means so that the latter makes electrical contact with the inner layer of semiconducting material.
  • the inner layer of semiconducting material makes electrical contact with regions or points at opposite ends of the, or the associated, winding.
  • the inner layer of semiconducting material also makes electrical contact with the first winding at one or more points or regions between the opposite end of the winding.
  • the inner layer of semiconducting material makes electrical contact with the winding at every n turns of the coil ⁇ O.ln turns, where n is typically from 100 to 10,000, typically about 1000.
  • the electrically conducting means has superconducting properties.
  • the invention is not intended to be limited to electrically conducting means having superconducting properties and is intended to cover any electrically conducting means whose electrical conducting properties significantly improve at low temperatures, e.g. at temperatures below 200 K.
  • the electrically conducting means may comprise low temperature superconductors, but most preferably comprise HTS materials, for example electrically insulated HTS wires or tape helically wound on an inner tube.
  • a convenient HTS tape comprises silver-sheathed BSCCO-2212 or BSCCO-2223 (where the numerals indicate the number of atoms of each element in the [Bi, Pb] 2 Sr 2 Ca 2 Cu 3 O x molecule) and hereinafter such HTS tapes will be referred to as "BSCCO tape(s)".
  • BSCCO tapes are made by encasing fine filaments of the oxide superconductor in a silver or silver oxide matrix by a powder-in-tube (PIT) draw, roll, sinter and roll process. Alternatively the tapes may be formed by a surface coating process. In either case the oxide is melted and resolidified as a final process step.
  • HTS tapes such as TiBaCaCuO (TBCCO-1223) and YBaCuO (YBCO-123) have been made by various surface coating or surface deposition techniques.
  • an HTS wire should have a current density beyond j c ⁇ 10 5 Acm "2 at operation temperatures from 65 K, but preferably above 77 K.
  • the filling factor of HTS material in the matrix needs to be high so that the engineering current density j a 10 4 Acm "2 . j c should not drastically decrease with applied field within the'Tesla range.
  • the electrically insulated helically wound HTS tape is cooled to below the critical temperature T c of the HTS by a cooling fluid, preferably liquid nitrogen, passing through the inner support tube.
  • the first winding may be provided with a magnetic core of magnetisable material, such as particulate material, preferably a compound of iron, wire, e.g. iron based, or tape material, e.g. iron based, amorphous or nano- crystalline.
  • the first winding may have an air core or a core of other non-magnetisable materials, such as plastics materials or non-magnetisable metals or ceramics.
  • the choice of the magnetic material depends on the application.
  • the core may also be hollow inside to allow a cooling channel of said cooling means to run therethrough. Typically such a cooling channel, especially for cooling superconductors, would carry a cooling medium such as liquid nitrogen to cool the coil down to required superconducting temperatures.
  • the core can typically be formed in two ways along the main axis of the winding in question.
  • the magnetic core is at a controlled specific potential and has to be electrically insulated against the first winding.
  • the potential of the first winding at its opposite ends is defined by the voltage applied to the winding.
  • the potential along the winding itself is given by the induced voltage caused by each turn of the winding around the core.
  • the magnetic core will be at equal constant potential all along the length of the first winding.
  • the winding however has a potential that depends on the induced voltage, as explained above.
  • the potential difference between the core and the winding will differ along the length of the winding. It is thus necessary to electrically insulate the core sufficiently against the winding so that no local discharges occur.
  • the second possibility for a magnetic core made of magnetisable material is to have no electrical insulation against the core but to provide an electrically insulated first winding. This has the advantage of saving insulation material and decreasing the total thickness of the resulting winding.
  • the magnetic core in this case has to be split up into overlapping "threads" or lengths which are electrically insulated against each other. Since the induced voltage along the winding per meter is less than 1000 Volts, it is sufficient to utilise standard insulation, such as enamel, for the core. It is also possible to use for the magnetic core thin tape of magnetic material or magnetic powder where the particles are insulated with an electrically insulating coating.
  • opposite end portions of the looped cable forming the first winding are embedded in and connected by magnetic material of high magnetic permeability so that the flux path can close with smaller reluctance.
  • the second winding may be arranged and formed in a number of different ways.
  • a second cable is arranged in at least one loop, with the looped first and second cables interlinking with each other, the second cable comprising: second electrically conducting means wound about a longitudinal axis of the second cable to provide the second winding, adjacent turns of the second winding being electrically insulated from each other; and second electrically insulating means associated with and surrounding the second winding and comprising solid plastics material within which the electric field of the second winding is contained in use of the transformer.
  • a magnetic flux ⁇ is induced along the longitudinal axis of the first-mentioned cable. This magnetic flux ⁇ x couples with the second winding. The magnetic flux ⁇ 2 induced in the second winding couples with the first winding. Thus excellent magnetic coupling is obtained.
  • the second cable may be constructed and arranged similarly to the first-mentioned cable described above.
  • a second cable is wound about a portion of the first-mentioned cable to provide electrically insulated turns of the second winding.
  • the second cable comprises second electrically conducting means and second electrically insulating means surrounding the second electrically conducting means and comprising solid plastics material within which the electric field of the second electrically conducting means is contained in use of the transformer.
  • the second electrically insulating means suitably comprises an inner layer of semiconducting material in electrical contact with said second electrically conducting means, an outer layer of semiconducting material at a controlled electrical potential along its length and an intermediate layer of electrically insulating material between the said inner and outer layers.
  • the construction of the second electrically insulating means may be as described above for the electrically insulating means of the first-mentioned cable.
  • the second winding is part of the cable and is wound about the longitudinal axis of the cable over the electrically insulating means.
  • the two windings share the same core (air core or magnetic core) inside the first winding.
  • the cable forming the first winding of the transformer may be wound in a helical path around a toroidal shaped magnetic core.
  • the cable may be wound around a rectangular or other shaped closed magnetic core.
  • the amount of superconducting means can be optimised.
  • the superconducting first winding can be wound as a tight helix or as a loose helix using less superconductor material. Also the "tightness" of the wound cable on the large closed magnetic core can be adjusted as required.
  • a shell type transformer in which a magnetic core is wrapped around the cable.
  • each cable may, instead of having a single first (or second) windings, have two or more coaxially arranged windings, typically connected in series.
  • each first is surrounded by a separate "band" of electrically insulating means, each insulation "band” comprising an inner layer of semiconducting material in electrical contact with its associated winding only at spaced apart intervals along the length of the winding, an outer layer of semiconducting material and an intermediate layer of electrically insulating material between the said inner and outer layers.
  • each insulation "band” comprising an inner layer of semiconducting material in electrical contact with its associated winding only at spaced apart intervals along the length of the winding, an outer layer of semiconducting material and an intermediate layer of electrically insulating material between the said inner and outer layers.
  • the winding angle and/or winding direction may be chosen to influence the flexibility of the cable or to reduce mechanical stress for brittle superconducting means
  • the winding angle and/or winding direction is primarily selected to influence the magnetic field created by a particular winding.
  • the winding angles used in the formation of the different windings are conveniently selected according to how the magnetic fields from each winding are to be arranged with respect to each other.
  • the respective winding angles and/or winding directions may be chosen so that in certain applications the magnetic fields from adjacent windings compliment and strengthen each other whereas in other applications the magnetic fields from adjacent windings oppose each other.
  • Figure 1 is a schematic representation of one embodiment of a high voltage transformer according to the invention having first and second windings;
  • Figure 2 is a schematic representation of the first and second windings of the transformer shown in Figure 1;
  • Figure 3 is a schematic, sectional view, on an enlarged scale, of one embodiment of the first or second winding of the transformer shown in Figure 1, the winding having an air core;
  • Figure 3A is a schematic, sectional view, on an enlarged scale, of a further embodiment of the first or second winding of the transformer shown in Figure 1, the winding having an air core;
  • Figure 4 is a partly cut away perspective view of another embodiment of the first or second winding of the transformer shown in Figure 1, the winding having a magnetic core;
  • Figure 5 is a schematic, partly cut away perspective view of further embodiment of the first or second winding of the transformer shown in Figure 1, the winding having a magnetic core;
  • Figure 6 is a schematic view, on an enlarged scale, of a magnetic core of the winding shown in Figure 5;
  • Figure 7 is a schematic, partly cut away perspective view of a yet further embodiment of the first or second winding of the transformer shown in Figure 1;
  • Figure 8 is a schematic representation of another embodiment of a high voltage transformer according to the invention having first and second windings
  • Figure 9 is a schematic representation of a further embodiment of a transformer according to the invention.
  • Figure 10 is a schematic representation of a yet further embodiment of a transformer according to the invention.
  • Figure 11 is a schematic representation of a still further embodiment of a transformer according to the invention.
  • Figure 12 is a schematic representation of a another embodiment of a transformer according to the invention.
  • FIGs 1 and 2 shows one embodiment of a high voltage (HV) transformer 1 according to the invention.
  • the transformer 1 is in the form of two cables 2 and 3 each formed into at least one closed loop and interlinked with each other.
  • the interlinked looped cables 2 and 3 will typically have the same construction.
  • the cables can take as illustrated below with reference to Figures 3 to 7.
  • Only cable 2 will be described, it being realised that cable 3 will suitably have a similar construction.
  • Opposite end portions of the two looped cables are preferably connected together by being embedded in magnetic material of high magnetic permeability.
  • FIG 3 shows one embodiment of cable 2 which comprises a coil or winding 4 wound from elongate high- temperature (T c ) superconducting (HTS) material, for example BSCCO tape or the like, which is electrically insulated, e.g. with varnish or the like, and wound on a support tube 5.
  • T c high- temperature
  • HTS superconducting
  • the support tube is conveniently made of an electrically insulating material.
  • the individual turns of the coil 4 are electrically insulated from each other.
  • a solid electrical insulation system surrounds the coil 4 and comprises an inner layer 6 of semiconducting material, an outer layer 7 of semiconducting material and, sandwiched between these semiconducting layers, an insulating layer 8.
  • the HTS material has its electrical insulation, e.g.
  • the layers 6-8 preferably comprise thermoplastics materials in close mechanical contact or preferably solidly connected to each other at their interfaces. Conveniently these thermoplastics materials have similar coefficients of thermal expansion and are resilient or elastic at least at room temperature.
  • the layers 6-8 are extruded together around the winding 4, using a multi-layer extrusion die or the like, to provide a monolithic structure so as to minimise the risk of cavities and pores within the electrical insulation. The presence of such pores and cavities in the insulation is undesirable since it gives rise to partial discharge in the electrical insulation at high electric field strengths.
  • the solid insulating layer 8 may comprise cross-linked polyethylene (XLPE) .
  • XLPE cross-linked polyethylene
  • the solid insulating layer may comprise, for example, other cross-linked materials, low density polyethylene (LDPE) , high density polyethylene (HDPE) , polypropylene (PP) , or rubber insulation, such as ethylene propylene rubber (EPR) , ethylene-propylene-diene monomer (EPDM) or silicone rubber.
  • the inner and outer layers 6 and 7 of semiconducting material may comprise, for example, a base polymer of the same material as the solid insulating layer 8 and highly electrically conductive particles, e.g. particles of carbon black or metallic particles, embedded in the base polymer.
  • the volume resistivity of these semiconductive layers e.g. 20 ohm. cm, may be adjusted as required by varying the type and proportion of carbon black added to the base polymer. The following shows how the resistivity can be varied using different types or quantities of carbon black.
  • the semiconducting outer layer 7 is connected at spaced apart regions along its length to a controlled potential, e.g. via electrically conductive strips.
  • this controlled potential will be earth or ground potential, the specific spacing apart of adjacent earthing points, i.e. the spacing apart of the earthing strips, being dependent on the resistivity of the layer 7.
  • a conductor e.g. a wire or conductive strip, along the length of the outer layer 7 and at the controlled potential.
  • the semiconducting outer layer 7 acts as a static shield and as an earthed outer layer which ensures that the electric field of the winding 4 is retained within the solid insulating layer 8 between the semiconducting layers 6 and 7. Losses caused by induced voltages in the layer 7 are reduced by increasing the resistance of the layer 7. However, since the layer 7 must be at least of a certain minimum thickness, e.g. no less than 0.8 mm, the resistance can only be increased by selecting the material of the layer to have a relatively high resistivity. The resistivity cannot be increased too much, however, else the voltage of the layer 7 mid-way between two adjacent earthing points will be too high with the associated risk of partial discharges occurring.
  • the superconducting winding 4 may be cooled by a cooling fluid, such as liquid nitrogen, to the required superconducting temperatures.
  • a cooling fluid such as liquid nitrogen
  • the liquid nitrogen may be passed along a channel (not shown), e.g. an annular channel formed between the support tube 5 and an inner, concentrically arranged tube (not shown) spaced from the support tube 5.
  • the cable 2 may be enclosed within a cryostat (not shown) to cool the winding to superconducting temperatures.
  • the cable 2 is arranged in a loop or loops and opposite end portions of the cable 2 (and cable 3) are suitably embedded in connecting magnetic material to close the flux path of the air core with small reluctance. Ideally the end portions of the cable should terminate close to each other.
  • the potential difference between the opposite ends of the winding 4 is high and thus the opposite ends of the winding should be well electrically insulated from each other.
  • a magnetic flux ⁇ is induced in the first winding of the cable 2 along the longitudinal axis of the cable 2.
  • This magnetic flux ⁇ x couples with the second winding of the cable 3.
  • the magnetic flux ⁇ 2 induced in the second winding couples with the first winding.
  • excellent magnetic coupling is obtained.
  • FIG 3A schematically shows a modified cable 101 for replacing either one or both of the cables 2 and 3 shown in Figures 1 to 3.
  • the cable 101 comprises a first coil 102 wound from elongate high- temperature (T c ) superconducting (“HTS”) material, for example BSCCO tape or the like, which is electrically insulated, e.g. with varnish or the like, and helically wound on a tubular support 103.
  • T c high- temperature
  • HTS superconducting
  • the individual turns of the first coil 102 are electrically insulated from each other.
  • Liquid nitrogen, or other cooling fluid may be passed along the tubular support 103 to cool the surrounding superconducting first coil to below its critical superconducting temperature T c .
  • a band 120 of solid electrical insulation surrounds the first coil 102 and comprises inner and outer layers 120a and 120b, respectively, of semiconducting material and an intermediate layer 120c of insulating material.
  • the HTS material has its electrical insulation, e.g. varnish insulation, removed therefrom at its opposite ends and preferably also at spaced intervals along its length so that the surrounding layer 120a is able to make electrical contact with the coil 102 along its length.
  • the outer layer e.g. varnish insulation
  • the 120b has elongate axial channels 121 formed in its outer surface and is surrounded by a metallic tubular support 122 similar to the support 3.
  • the channels and support 22 define axial cooling ducts for cooling fluid if required.
  • Helically wound electrically insulated elongate HTS material for example BSCCO tape or the like, is wound on the support 122 to form a second coil 123 around the tubular support 122 having its individual turns electrically insulated from each other.
  • the HTS material forming the second coil 123 has its electrical insulation, e.g. varnish insulation, removed therefrom at its opposite ends and preferably also at spaced intervals along its length so that the surrounding layer 125a is able to make electrical contact with the coil 123 along its length.
  • a further band 125 of insulation is positioned around the second coil 123.
  • the band 125 comprises inner and outer layers 125a and 125b of semiconducting material and an intermediate layer 125c of insulating material.
  • the outer layer 125b of the outermost electrical insulation band 125 is grounded at spaced intervals along its length as shown schematically at 127.
  • the layers 120a and 125a can be positioned in contact with the underlying coils 102 and 123, respectively, to ensure electrical contact with the insulation removed portions of the coils.
  • radial gaps 128 and 126 may be provided, respectively, between the band 120 and the layer 114 and the band 125 and the superconducting layer 123. These radial gaps 128 and 126 provide gaps for expansion and contraction to compensate for the differences in the thermal coefficients of expansion (a) between the electrical insulation bands and the superconducting coils.
  • the gaps 128 and 126 may be void spaces or may incorporate foamed, highly compressible material to absorb any relative movement between the superconducting coils and surrounding electrical insulation.
  • the foamed material if provided, may be semiconducting to ensure electrical contact between the coil 102 and layer 120a and the coil 123 and layer 125a. Additionally, or alternatively, metal wires may be provided for ensuring the necessary electrical contact.
  • a cryostat 115 arranged outside the semiconducting layer 125b, comprises two spaced apart flexible corrugated metal tubes 116 and 117. The space between the tubes 116 and 117 is maintained under vacuum and contains thermal superinsulation 118. Instead of the cryostat 115, the induction device may be contained within a thermally insulated, cryogenically cooled container shown schematically at 150.
  • the coils 102 and 123 may be connected in series.
  • the bands of electrical insulation 120 and 125 are formed in a similar manner to the insulation formed by the corresponding insulation layers described with respect to the embodiment of Figure 3.
  • Figure 4 shows an alternative design of cable 2' for a winding of the transformer 1 and illustrates how an inner magnetic core 11 can be integrated into the design.
  • the cable 2' is similar to the cable 2 (or cable 101 of Figure 3A) and, where possible, the same reference numerals have been used to designate the same or similar parts.
  • the magnetic core 11 comprises magnetic material which may be particulate, e.g. in the form of particulate iron or compounds of iron; wire, e.g. iron based; or tape, e.g. Fe based, amorphous or nano-crystalline.
  • the potential at opposite ends of the winding 4 of the cable 2' is defined by the voltage applied to the elongate superconducting material.
  • the potential along the winding 4 is determined by the induced voltage in each turn of the winding around the magnetic core 11.
  • a controlled potential e.g. ground potential or the high potential of the HV system, is applied to the magnetic core 11 which will have this same constant potential along its length.
  • the winding 4 has a potential that depends on the induced voltage, as explained above, the potential difference between the magnetic core 11 and the winding 4 will also differ along the length of the cable 2.
  • the first insulation system comprising the inner and outer layers 6 and 7 of semiconducting material and the intermediate layer 8 of insulating material, is positioned radially outside the winding 4.
  • the second insulation system is positioned radially inside the winding 4 and comprises the insulation layer 12, an outer layer 13 of semiconducting material and an inner layer 14 of semiconducting material.
  • This second insulation system is similar to the first insulation system with the individual layers 12-14 forming a unitary construction.
  • the winding 4 is wound directly on the outer layer 13 (i.e. the support tube 5 of the Figure 3 embodiment is not required) .
  • the semiconducting inner layer 6 and semiconducting outer layer 13 should make electrical contact with the winding 4 at opposite ends of the latter and preferably also at spaced apart locations between the ends of the winding.
  • FIG. 5 An alternative design of cable 2" for a winding of the transformer 1 is shown in Figures 5 and 6, in which a magnetic core 21 is kept at a "floating" potential along its length which obviates the necessity of having electrical insulation between the magnetic core 21 and the surrounding winding 4.
  • the winding 4 may be wound on an electrically insulating support tube 5.
  • the support tube 5 may be made of semiconducting material which is electrically connected to the magnetic core 21.
  • the magnetic core 21 is formed of a plurality of overlapping
  • the core lengths 22 can be made from tape of magnetic material or from insulated magnetic particles.
  • the outer layer 7 of semiconducting material of a cable of the transformer 1 may be surrounded by an electrically insulated metal sheath 31 (see Figure 7) . It is important that the sheath 31 is not completely closed so as to prevent the creation of an inductive short circuit.
  • the sheath 31 should therefore have at least one interruption, e.g. in the form of a slit 32, along its length.
  • the sheath 31 maybe used to apply a controlled potential, e.g. ground potential, along the length of the outer layer 7.
  • rigidity may be provided by a surrounding sheath (not shown) of non-metallic, e.g. plastics, material which may completely enclose the cable.
  • FIG 8 shows another embodiment of a high voltage (HV) transformer 40 according to the invention.
  • the transformer has a high voltage first winding formed from a cable 41 similar to any of the cables 2, 2', 2" or 101 described above.
  • the low voltage second winding 42 is wound from a different type of cable 43.
  • the cable 43 comprises inner electrically conducting means surrounded by solid electrical insulation.
  • the wound turns of the cable 43 provide the insulated turns of the second winding 42.
  • the inner electrically conducting means can be considered to be similar to the cable 2 described above except that the winding 4 in this embodiment is replaced by wound electrically conducting means, e.g. tape, which is not electrically insulated and thereby provides a generally cylindrical superconducting conductor instead of a winding with turns insulated from each other.
  • the electrical insulation surrounding the inner electrically conducting means is similar to the insulation system described above with reference to Figures 3 and 4. Although it is preferred that the electrically conducting means is superconducting (and as such will be provided with cooling means for cooling to superconducting temperatures), this is not essential.
  • a specific example of a non-superconducting winding which could be used as the second winding is a winding of the type disclosed in WO 97/45847 (PCT/SE97/00875) .
  • FIG 9 shows a cable 50 similar in construction to the cable 2 shown in Figure 3 (or cable 101 shown in Figure 3A) but having an additional, insulated electrical conducting means wound around the semiconducting outer layer 7 to provide the second winding 51.
  • the first and second windings in this design share the same core.
  • the core may be as shown or may be designed as described above with regard to the other embodiments .
  • the core may be a magnetic core or an air core.
  • the ends of the cable 50 may be joined together by magnetic material of high magnetic permeability to provide a low reluctance path for the magnetic flux.
  • a transformer 60 has a high voltage first winding formed from a cable 61 similar to any of the cables 2, 2', 2" or 101 described above. However the cable
  • 61 is wound in a helical path around a closed magnetic core
  • the current in the cable 61 can be divided into two components, one component flowing in the azimuthal direction with a constant radius and the other component flowing axially along the longitudinal axis of the cable. Since the cable is wrapped around a toroidal magnetic core, the effect of the induction is twofold. Firstly as the axial component in the cable, as mentioned above, and secondly as the axial component in the large magnetic core about which the cable is wound, i.e. as in conventional transformers. With a superconducting cable, the amount of superconducting means can be optimised. The superconducting first winding of the cable 61 can be wound as a tight helix or as a loose helix using less superconductor material.
  • the "tightness" of the wound cable 61 on the large closed magnetic core 62 can be adjusted as required.
  • the low voltage winding is not shown.
  • the core 62 need not be truly “toroidal".
  • the core may have a non-circular section, e.g.
  • the D-shaped or oval in a plane perpendicular to the plane of Figure 10.
  • the "straight" part of the D- section forms a cylindrical inner wall of the "torus".
  • the torus need not be truly annular in shape.
  • the transformer 70 shown in Figure 11 is similar to that shown in Figure 10. However a rectangular shaped core 71 is provided about which the cable 72 is wound. Again the low voltage winding is not shown.
  • Figure 12 shows a shell -type transformer 80 in which a core 81 is positioned, or wrapped, around the wound cable 82.
  • the present invention is especially well suited for superconductors although it is not limited to superconducting windings.
  • the windings may merely be cooled externally, e.g. by air or other cooling fluid.
  • enclosure means may be provided around the windings, the cooling fluid being supplied to the space between the enclosure means and the windings.
  • the external cooling means prevents overheating of the winding (s) so that the or each cooled winding is cooled, for example, to ambient temperatures, e.g. below about 25 °C.
  • the transformer Since the high voltage winding consists of many turns, it can be very long (several kilometres) and thus must have a very low resistance in order to carry a high current.
  • the transformer is well suited for high voltages in combination with both low and high currents.
  • the magnetic coupling is excellent between the low and high voltage windings.
  • the cable core forming at least the first winding is well insulated and can easily be installed e.g. as part of a transmission line.
  • the production technology is simple and is built on known cable technology.
  • the system is modular as a device may consist of several cable core units in parallel or in series.
  • the insulation system is superb and is superior to conventional epoxy insulation.
  • the achievable inductance is very high due to the winding arrangements described.
  • the mechanical stress (for example in case of a short circuit) is very evenly distributed in the winding and is stabilised mechanically through the insulation surrounding the winding.
  • An insulation system can be made of an all-synthetic film with inner and outer semiconducting layers or portions made of polymeric thin film of, for example, PP, PET, LDPE or HDPE with embedded conducting particles, such as carbon black or metallic particles and with an insulating layer or portion between the semiconducting layers or portions.
  • a dry, wound multilayer thin film insulation has also good thermal properties and can be combined with a superconducting pipe as an electric conductor and have coolant, such as liquid nitrogen, pumped through the pipe.
  • an electrical insulation system is similar to a conventional cellulose based cable, where a thin cellulose based or synthetic paper or non-woven material is lap wound around a conductor.
  • the semiconducting layers on either side of an insulating layer, can be made of cellulose paper or non-woven material made from fibres of insulating material and with conducting particles embedded.
  • the insulating layer can be made from the same base material or another material can be used.
  • an insulation system is obtained by combining film and fibrous insulating material, either as a laminate or as co-lapped.
  • An example of this insulation system is the commercially available so-called paper polypropylene laminate, PPLP, but several other combinations of film and fibrous parts are possible. In these systems various impregnations such as mineral oil or liquid nitrogen can be used.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)

Abstract

L'invention concerne un transformateur haute tension (1) comprenant un câble (2) arrangé en au moins une boucle et comprenant un dispositif électroconducteur enroulé autour d'un axe longitudinal du câble de manière à former une première bobine (4) à spires adjacentes isolées électriquement les une des autres ainsi qu'un dispositif d'isolation électrique solide (6-8) associé à la première bobine (4) et entourant celui-ci et qui contient le champ électrique de la première bobine pendant l'utilisation du transformateur. Ce dernier comprend également au moins une seconde bobine (3) couplé par induction à la première bobine ainsi qu'un dispositif de refroidissement servant à refroidir au moins l'une des bobines.
PCT/EP1999/010509 1998-12-23 1999-12-23 Transformateur haute tension Ceased WO2000039820A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU27959/00A AU2795900A (en) 1998-12-23 1999-12-23 A high voltage transformer

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9828652.9 1998-12-23
GBGB9828652.9A GB9828652D0 (en) 1998-12-23 1998-12-23 A high voltage transformer
GBGB9912610.4A GB9912610D0 (en) 1999-05-28 1999-05-28 A high voltage transformer
GB9912610.4 1999-05-28

Publications (1)

Publication Number Publication Date
WO2000039820A1 true WO2000039820A1 (fr) 2000-07-06

Family

ID=26314926

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1999/010509 Ceased WO2000039820A1 (fr) 1998-12-23 1999-12-23 Transformateur haute tension

Country Status (2)

Country Link
AU (1) AU2795900A (fr)
WO (1) WO2000039820A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009013318A1 (de) * 2009-03-18 2010-09-23 Nexans Supraleitender Strombegrenzer mit Magnetfeldtriggerung
WO2018206953A1 (fr) * 2017-05-10 2018-11-15 Megger Instruments Ltd Capteur de courant flexible

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998034245A1 (fr) * 1997-02-03 1998-08-06 Asea Brown Boveri Ab Transformateur d'alimentation/bobine d'induction
GB2332557A (en) * 1997-11-28 1999-06-23 Asea Brown Boveri Electrical power conducting means

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998034245A1 (fr) * 1997-02-03 1998-08-06 Asea Brown Boveri Ab Transformateur d'alimentation/bobine d'induction
GB2332557A (en) * 1997-11-28 1999-06-23 Asea Brown Boveri Electrical power conducting means

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009013318A1 (de) * 2009-03-18 2010-09-23 Nexans Supraleitender Strombegrenzer mit Magnetfeldtriggerung
WO2018206953A1 (fr) * 2017-05-10 2018-11-15 Megger Instruments Ltd Capteur de courant flexible
US11009537B2 (en) 2017-05-10 2021-05-18 Megger Instruments Ltd. Flexible current sensor

Also Published As

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