WO1998034247A1 - Cable pour enroulement electrique et enroulement ainsi forme - Google Patents

Cable pour enroulement electrique et enroulement ainsi forme Download PDF

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Publication number
WO1998034247A1
WO1998034247A1 PCT/SE1998/000159 SE9800159W WO9834247A1 WO 1998034247 A1 WO1998034247 A1 WO 1998034247A1 SE 9800159 W SE9800159 W SE 9800159W WO 9834247 A1 WO9834247 A1 WO 9834247A1
Authority
WO
WIPO (PCT)
Prior art keywords
cable
winding
cable according
semiconducting layer
layer
Prior art date
Application number
PCT/SE1998/000159
Other languages
English (en)
Inventor
Udo Fromm
Pär Holmberg
Peter Carstensen
Mats Leijon
Original Assignee
Asea Brown Boveri 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 SE9700344A external-priority patent/SE508523C2/sv
Application filed by Asea Brown Boveri Ab filed Critical Asea Brown Boveri Ab
Priority to JP53280198A priority Critical patent/JP2001509963A/ja
Priority to EP98902356A priority patent/EP0956569A1/fr
Priority to AU58910/98A priority patent/AU5891098A/en
Priority to CA002276348A priority patent/CA2276348A1/fr
Publication of WO1998034247A1 publication Critical patent/WO1998034247A1/fr
Priority to NO993715A priority patent/NO993715L/no

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/288—Shielding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/32—Insulating of coils, windings, or parts thereof
    • H01F27/323—Insulation between winding turns, between winding layers

Definitions

  • the present invention-p relates to an electric cable designed for an electric winding, such as a transformer or reactor winding, and a dry transformer or a reactor or inductor with such a winding.
  • Transformers are used for enabling exchange of electric en- ergy between two or more electrical systems.
  • Transformers are available for powers ranging from the VA region up to the 1000 MVA region. With respect to the voltage range a spectrum of up to the highest transmission voltages are used today.
  • the transformers referred to in the present invention are so-called power transformers having rated outputs from a few hundred kVA up to more than 1000 MVA and rated voltages of from 3 - 4 kV up to very high transmission voltages.
  • a power transformer In generally the main task of a power transformer is to enable the exchange of electric energy, of mostly differing voltages but with the same frequency, between two or more electrical systems.
  • a conventional power transformer comprises a transformer core made of laminated oriented sheets, normally of silicon iron.
  • the core consists normally of a number of core legs connected by yokes.
  • a number of windings are provided around the core legs, referred to as primary, secondary and regulating windings. In power transformers these windings are practically always arranged in concentric configuration and distributed along the length of the core leg.
  • the transformer may be provided with an outer casing, which in turn is provided with ventilating openings, in order to be pro ⁇ tected from contact and possibly reduce the external mag- netic field of the transformer.
  • an outer tank in which the transformer is to be contained, the latter consisting of a transformer core with coils, oil for insulation and cooling and different types of mechanical support means.
  • the tank has to meet very high mechanical requirements since prior to filling the transformer with oil it is necessary that it be vacuum treated to almost absolute vacuum.
  • the need for an outer tank implies very time- consuming manufacturing and testing procedures.
  • a tank implies also rather large outer dimensions.
  • the large outer dimensions entail also, as a rule, great transport problems.
  • Transformers are also, as a rule, provided with a complicated forced oil-cooling. For electrical connection between the outer connections of the transformer and the nearest connected coils/windings there is a bushing fixed to the tank which must meet the insulation requirements which occur both on the inside and' the outside of the tank.
  • a conductor is known through US 5,036,165, in which the in- sulation is provided with an inner and an outer layer of semiconducting pyrolized glassfiber. It is also known to provide conductors in a dynamo-electric machine with such an insulation, as described in US 5,066,881 for' instance, where a semiconducting pyrolized glassfiber layer is in contact with the two parallel rods forming the conductor, and the insulation in the stator slots is surrounded by an outer layer of semiconducting pyrolized glassfiber.
  • the pyrolized glassfiber material is described as suitable since it retains its resistivity even after the impregnation treatment.
  • the purpose of the present invention is to provide an electric cable having solid insulation of similar construction as cables for power distribution, intended for electric windings, which cable enables improvement of a.o. perform- ances of dry transformers. It is also the purpose of the invention to provide an electric winding of such a cable as well as to provide a dry transformer and a reactor or inductor comprising such windings.
  • a cable as defined in claim 1 a winding as defined in claim 21, a transformer as defined in claim 25 and an inductor as defined in claim 26.
  • the cable according to the invention can withstand very high voltages and due to its outer semiconducting layer and means to connect this layer to earth if needed, the potential of the winding cable with reference to its environment may be defined, both for alternating voltages and/or for impulse voltages which is a significant advantage as metallic components in for example power transformers are normally connected to a given earth potential.
  • a continuous earthing of the cable is also achieved, both for alternating voltages and impulse voltages, without the use of special contacting means as in the case of earthing in discrete points. The largest part of the total voltage is applied across the insulation of the cable. Between the outer semiconducting layer and earth only alter- nating voltages of the order of 100 V and impulses of the order kV may appear.
  • the insulation, between an outer, sec- ond semiconducting layer and an earthed conductor arranged thereon, is in the form of a band made of insulating tape, extending along the cable where the earthed conductor is applied as a band divided into separated parts, arranged onto the insulating tape.
  • said means for earthing comprise a second insulating layer, arranged on the outside of the second semiconducting layer, and an electrically conducting outer layer connected to earth, which surrounds the second insulating layer forming a capacitance together with the second semiconducting layer, which is significantly larger than the cable capacitance.
  • the outer semiconducting layer is forced into a low voltage by capacitive voltage division.
  • the insulation comprises an insulating tape wound around the second semiconducting layer and the earthed conductor comprises an outer casing of electrically conducting material connected to earth, said tape being wound in separated turns with a space provided between each turn and/or openings are provided in the tape so that air filled spaces are formed between the second semiconducting layer and the casing, which air filled spaces form discharge gaps in order to divert voltage impulses from the second semiconducting layer if their voltage exceeds the predetermined limit.
  • the tape By also dimensioning the tape such that a capacitance is formed between the outer casing and the second semiconduct- ing layer, which is significantly larger than the cable capacitance, it is ensured that the second semiconducting layer is continuously close to earth potential for alternating voltages.
  • the outer layer and the outer casing have circular cuts at predetermined positions along the cable.
  • the outer casing is in the form of separated rings of electrically conducting material around the insulation, applied separated at predetermined positions along the cable. This hinders short circuit loops in the winding which is formed by the cable.
  • the diameter is within the interval of 20 - 200 mm and the conductor area is within the interval of 80 - 3000 mm 2 .
  • the windings are preferably composed of cables having solid, extruded insulation, of a type now used for power distribution, such as XLPE-cables or cables with EPR-insulation.
  • cables are flexible, which is an important property in this context since the technology for the device according to the invention is based primarily on winding systems in which the winding is formed from a cable which is bent during assembly.
  • the flexibility of a XLPE-cable normally cor- responds to a radius of curvature of approximately 20 cm for a cable 30 mm in diameter, and a radius of curvature of approximately 65 cm for a cable 80 mm in diameter.
  • the term "flexible" is used to indicate that the winding is flexible down to a radius of curvature of the order of four times the cable diameter, preferably eight to twelve times the cable diameter.
  • the cable according to the present invention is constructed to retain its properties even when bent and when subjected to thermal stress during operation. It is vital that the layers retain their adhesion to each other in this context.
  • the material properties of the layers are decisive here, particularly their elasticity and relative coefficients of thermal expansion.
  • the insu- lating layer consists of cross-linked, low-density polyethylene, and the semiconducting layers consist of polyethylene with soot and metal particles mixed in.
  • the insulating layer may consist, for example, of a solid thermoplastic material such as low-density polyethylene (LDPE) , high-density polyethylene (HDPE) , polypropylene (PP) , polybutylene (PB) , polymethyl pentene (PMP) , cross- linked materials such as cross-linked polyethylene (XLPE) , or rubber such as ethylene propylene rubber (EPR) or silicon rubber.
  • LDPE low-density polyethylene
  • HDPE high-density polyethylene
  • PP polypropylene
  • PB polybutylene
  • PMP polymethyl pentene
  • XLPE cross-linked polyethylene
  • EPR ethylene propylene rubber
  • the inner and outer semiconducting layers may be of the same basic material but with particles of conducting material such as soot or metal powder mixed in.
  • the mechanical properties of these materials are affected relatively little by whether soot or metal powder is mixed in or not - at least in the proportions required to achieve the conductivity necessary according to the invention.
  • the insu- lating layer and the semiconducting layers thus have substantially the same coefficients of thermal expansion.
  • Ethylene-vinyl-acetate copolymers/nitrile rubber, butyl graft polyethylene, ethylene-butyl-acrylate-copolymers and ethylene-ethyl-acrylate copolymers may also constitute suitable polymers for the semiconducting layers.
  • the materials listed above have relatively good elasticity, with an E-modulus of E ⁇ 500 MPa, preferably ⁇ 200 MPa.
  • the elasticity is sufficient for any minor differences between the coefficients of thermal expansion for the materials in the layers to be absorbed in the radial direction of the elasticity so that no cracks or other damage appear and so that the layers are not released from each other.
  • the material in the layers is elastic, and the adhesion between the layers is at least of the same magnitude as the strength of the weakest of the materials.
  • the conductivity of the two semiconducting layers is sufficient to substantially equalize the potential along each layer.
  • the conductivity of the outer semiconducting layer is sufficiently large to contain the electrical field in the cable, but sufficiently small not to give rise to signifi- cant losses due to currents induced in the longitudinal direction of the layer.
  • each of the two semiconducting layers substantially constitutes one equipotential surface, and these layers will substantially enclose the electrical field between them.
  • a dry transformer is also produced having at least one cable winding according to the above mentioned.
  • a dry transformer is hereby obtained, which is able to operate at significantly higher voltages enabling effective cooling so that the transformer is able to tolerate high powers.
  • a transformer may also be mounted conveniently on site, i.e. the core and windings may be transported separately which minimises transport problems.
  • figure 1 shows a perspective view of the end of a first embodiment of a cable, according to the invention, provided with means for earthing the cable for impulse voltages
  • figure 2 shows the corresponding equivalent electrical circuit
  • figure 3 shows a cross-section of a second embodiment of the cable, according to the invention, provided with means for earthing the cable for alternating voltages
  • figure 4 shows the corresponding equivalent electrical circuit
  • figure 5 shows a perspective view of the end of a third embodiment of the cable, according to the invention, provided with means for earthing the cable for both im- pulse voltages and alternating voltages
  • figure 6 shows a winding of an embodiment of the cable according to the invention
  • - figure 7 shows a winding of another embodiment of the cable according to the invention.
  • FIG. 1 shows a perspective view of an end of an embodiment of the cable according to the invention.
  • the cable comprises a conducting core 2, consisting of a plurality of strands of electrically conducting material, for example copper.
  • the core 2 is arranged in the centre of the cable and around the core there is an inner first semiconducting layer 4.
  • an insulating layer 6, of for example XLPE-insulation Around the insulating layer 6 there is arranged an outer, second semiconducting layer 8.
  • On the insulating tape there is applied an electrical conductor in the form of a band 12 made of elec- trically conducting material, such as metal.
  • the conductor 12 is also earthed in a suitable manner.
  • FIG. 2 shows for this embodiment of the cable according to the invention, an equivalent electrical circuit where the voltage on the core 2 of the cable is denoted by U, the cable capacitance is denoted by C c and the discharge gap 14 is located between the outer, second semiconducting layer 8 and the conductor 12.
  • the conducting band 1 " 2 " is divided into separate parts which may each be earthed separately.
  • Figure 3 shows a second embodiment of the cable according to the invention where a relatively thin second insulating layer 16 is arranged on the outside of the second semiconducting layer 8.
  • an electrically conducting outer layer 18 connected to earth which surrounds the second insulating layer 16 forming an earthing capacitance together with the second semiconducting layer 8.
  • the outer layer 18 consists preferably of metal.
  • Figure 4 shows an equivalent electrical circuit to the embodiment of the cable shown in Figure 3.
  • the voltage on the core 2 of the cable is denoted by U and the cable capacitance is denoted by C c whereas the earthing capacitance between the second semicon- ducting layer 8 and the outer layer 18 is denoted by C G .
  • the earthing capacitance C G is significantly larger than the cable capacitance C c the potential of the second semiconducting layer 8 will remain close to earth potential by means of the capacitive voltage division between the voltage U on the core 2 of the cable and the earth potential which is on the outer layer 18.
  • the outer layer 18 may be earthed for every winding turn if each turn is separated by a certain distance.
  • Figure 5 shows an end of an embodiment of the cable according to the invention where an electrically insulating tape 20 is wound around the cable on the outside of the second semiconducting layer 8.
  • the tape 20 is wound with inter- spaces 22 and relatively small openings 24 are provided in the tape 20.
  • the outer casing 26 is preferably made of metal foil.
  • Air filled spaces are formed between the second semiconducting layer 8 and the outer casing 26 forming discharge gaps between the turns of the tape 20 and at the openings 24, which divert occurring voltage impulses away from the second semiconducting layer 8 to the outer casing 26 and earth if the impulse voltage exceeds a predetermined limit.
  • the described embodiment may of course be modified, so that air filled spaces forming discharge gaps exist only between the turns of the tape, i.e. no openings are provided in the tape, or the tape may be wound tightly, so that there are discharge gaps only through the openings in the tape.
  • An embodiment with relatively small openings renders a very ro- bust construction.
  • Figure 6 shows a winding of a cable according to the invention, in which the adjacent winding turns 28 are in contact with each other and the cuts 30 in the cable casing are arranged at the same location for each cable turn 28.
  • An interruption is hereby achieved in the outer casings across the whole winding and the outer layer of the winding needs only be earthed at one end 32 of the winding.
  • Figure 7 shows a winding with an embodiment of the cable where the outer casing is formed as rings 36 of conducting material which rings surround the insulation. These rings 36 are arranged at predetermined locations along the cable, and the insulating spaces " 38 between the rings 36 are broader than the rings 36.
  • a cable is wound such that rings 36 of adjacent winding turns are in contact with one another in such a way that the rings form at least one continuous electrical connection across the winding.
  • there are two such electrical connections across the winding which are earthed at 38 and 40 respectively.
  • two isolated rings which are also earthed, are shown at 42 and 44.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Coils Of Transformers For General Uses (AREA)
  • Insulated Conductors (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

Cette invention se rapporte à un câble électrique qui est conçu pour un enroulement électrique, tel qu'un enroulement de transformateur ou de réacteur, et qui comprend un noyau électroconducteur (2) placé en contact avec une première couche semi-conductrice interne (4) entourant le noyau. Une première couche isolante (6) est disposée sur l'extérieure de la première couche semi-conductrice de façon à l'entourer. Une seconde couche semi-conductrice externe (8) est disposée sur l'extérieur de la première couche isolante de façon à l'entourer. Des moyens (16, 18) sont également placés sur l'extérieur de la seconde couche semi-conductrice pour mettre le câble à la terre en vue de créer une alternance de tension et/ ou des impulsions de tension en continu sur la majeure partie au moins de la longueur dudit câble.
PCT/SE1998/000159 1997-02-03 1998-02-02 Cable pour enroulement electrique et enroulement ainsi forme WO1998034247A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP53280198A JP2001509963A (ja) 1997-02-03 1998-02-02 電気巻線用のケーブルおよび巻線
EP98902356A EP0956569A1 (fr) 1997-02-03 1998-02-02 Cable pour enroulement electrique et enroulement ainsi forme
AU58910/98A AU5891098A (en) 1997-02-03 1998-02-02 A cable for electrical windings, and such a winding
CA002276348A CA2276348A1 (fr) 1997-02-03 1998-02-02 Cable pour enroulement electrique et enroulement ainsi forme
NO993715A NO993715L (no) 1997-02-03 1999-07-30 Kabel for elektrisk vikling, og en slik kabel

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
SE9700344A SE508523C2 (sv) 1997-02-03 1997-02-03 Elektrisk kabel, avsedd för elektrisk lindning, samt sådan lindning, torrtransformator och reaktor
SE9700344-6 1997-11-28
SE9704418A SE9704418D0 (sv) 1997-02-03 1997-11-28 Elektrisk komponent
SE9704418-4 1997-11-28

Publications (1)

Publication Number Publication Date
WO1998034247A1 true WO1998034247A1 (fr) 1998-08-06

Family

ID=26662870

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1998/000159 WO1998034247A1 (fr) 1997-02-03 1998-02-02 Cable pour enroulement electrique et enroulement ainsi forme

Country Status (8)

Country Link
EP (1) EP0956569A1 (fr)
JP (1) JP2001509963A (fr)
CN (1) CN1244287A (fr)
AU (1) AU5891098A (fr)
CA (1) CA2276348A1 (fr)
NO (1) NO993715L (fr)
SE (1) SE9704418D0 (fr)
WO (1) WO1998034247A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000041190A1 (fr) * 1998-12-30 2000-07-13 Square D Company Technique de suppression de transitoires d'enroulement

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101883070B1 (ko) * 2016-10-25 2018-07-27 삼성전기주식회사 인덕터
ES2770126T3 (es) 2017-03-24 2020-06-30 Abb Schweiz Ag Arrollamiento de alta tensión y dispositivo de inducción electromagnética de alta tensión

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4109098A (en) * 1974-01-31 1978-08-22 Telefonaktiebolaget L M Ericsson High voltage cable
US5036165A (en) * 1984-08-23 1991-07-30 General Electric Co. Semi-conducting layer for insulated electrical conductors

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4109098A (en) * 1974-01-31 1978-08-22 Telefonaktiebolaget L M Ericsson High voltage cable
US5036165A (en) * 1984-08-23 1991-07-30 General Electric Co. Semi-conducting layer for insulated electrical conductors

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000041190A1 (fr) * 1998-12-30 2000-07-13 Square D Company Technique de suppression de transitoires d'enroulement

Also Published As

Publication number Publication date
NO993715D0 (no) 1999-07-30
AU5891098A (en) 1998-08-25
CN1244287A (zh) 2000-02-09
EP0956569A1 (fr) 1999-11-17
NO993715L (no) 1999-07-30
SE9704418D0 (sv) 1997-11-28
CA2276348A1 (fr) 1998-08-06
JP2001509963A (ja) 2001-07-24

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