US2650261A - Gas-filled electric cable with paper and polystyrene insulation - Google Patents

Gas-filled electric cable with paper and polystyrene insulation Download PDF

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Publication number
US2650261A
US2650261A US187040A US18704050A US2650261A US 2650261 A US2650261 A US 2650261A US 187040 A US187040 A US 187040A US 18704050 A US18704050 A US 18704050A US 2650261 A US2650261 A US 2650261A
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US
United States
Prior art keywords
dielectric
polystyrene
cable
paper
conductor
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.)
Expired - Lifetime
Application number
US187040A
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English (en)
Inventor
Davey Edward Leslie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WT Glover and Co Ltd
Original Assignee
WT Glover and Co Ltd
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 GB26332/49A external-priority patent/GB675224A/en
Application filed by WT Glover and Co Ltd filed Critical WT Glover and Co Ltd
Application granted granted Critical
Publication of US2650261A publication Critical patent/US2650261A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/02—Disposition of insulation
    • H01B7/0241—Disposition of insulation comprising one or more helical wrapped layers of insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/02—Disposition of insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/06—Gas-pressure cables; Oil-pressure cables; Cables for use in conduits under fluid pressure
    • H01B9/0644—Features relating to the dielectric of gas-pressure cables
    • H01B9/0655—Helically wrapped insulation

Definitions

  • the minimum thickness that is specified in terms of numbers of layers or lappings will only be greater than 10% of the conductor radius in the case of cables operating at the lower end of the supertension voltage range and having conductors at the lower end of the range of practical conductor sizes, or in other cases, Where thick tapes of oriented polystyrene are used.
  • a minimum thickness of the wall of polystyrene of fourteen layers is required in order to ensure that any inaccuracies in lapping do not affect the dielectric strength of the wall to a serious extent and thus allow excessive electrical stress to be imposed on the impregnated paper beyond.
  • a coating of lubricant such as an oil or petroleum jelly may be applied to the surfaces of the strips of polystyrene film before they are wrapped on in place in the cable. This coating ensures sufficient freedom of relative movement between the superposed layers of polystyrene nlm for the normal bending of the cable during the subsequent manufacturing stages and during the laying operation.
  • the present invention we provide a modied form of the cable described and claimed in the specification of the aforesaid patent which eliminates or at least reduces to a considerable extent the sticking together of the strips of oriented polystyrene lm of which the inner part of the dielectric is built up.
  • the inner part of the dielectric is built up of alternate single strip layers of oriented polystyrene lm and layers, preferably single strip layers, of pre-impregnated paper.
  • pre-impregnated paper we mean paper impregnated before the lapping process with a cable impregnating compound that does not flow at any temperature within the working range of the cable.
  • Figure 1 is a perspective view of the stepped end of a length of cable embodying the invention.
  • Figure 2 is a diagrammatic drawing showing fragmental sections of the inner portions of a lapped cable dielectric, the sections being taken at longitudinally spaced points in the cable.
  • Figure l is a perspective view of a stepped end ⁇ of the cable.
  • the cable is designed for a working voltage of 132 kv. between the conductors of a B-phase A. C. transmission system. It will be seen that the cable comprises a stranded conductor l, the circumferentially disposed wires of which are flattened as by drawing the conductor through a die, the diameter of the drawn conductor being 2.0 cms.
  • the conductor is provided with a screen 2 consisting of two layers of pre-impregnated perforated metallized paper tape applied with a 5 to 10% overlap with their metallized faces outwards followed by a similar lapping of pre-impregnated unperforated metallized paper tape. These tapes are three mils thick so that the screen has a radial thickness of 0.023 cm., giving the conductors an effective external radius of 1.023 cms. and a smooth surface in contact with the surrounding dielectric.
  • the dielectric consists of an inner part 3 and an outer part 4.
  • the inner part 3 consists of alternate single strip layers 3a of pre-impregnated paper of 2.5 mils (0.006 cm.) thickness and single strip layers 3b of oriented polystyrene film of 4 mils (0.01 cm.) thickness built up to an external radius of 1.403 cms., the rst layer being of polystyrene, the next paper, the third of polystyrene and so on. Alternatively the rst layer may be of paper, the second of polystyrene, the third of paper, and so on.
  • the outer part 4 of the dielectric is built up entirely of helical lappings of strips of pre-impregnated paper to an external radius of 2.27 cms.
  • a screen 5 formed by a helical lapping of copper tape 3 mils thick applied with a to 20% overlap.
  • the screened core is enclosed in a lead or a lead alloy sheath 6 which is mechanically reinforced to withstand an internal gas pressure of about 14 atmospheres by helical lappings l, 8 and 9 of metal tape.
  • Enclosing these reinforcing tapes is a second lead or lead-alloy sheath l0 which is protected against corrosion by an outer protective covering Il of bitumen-impregnated jute or hessian or the like.
  • the interior of the cable namely the portion within the inner sheath B contains nitrogen under a pressure of 14 atmospheres.
  • the joints between the successive turns of tape in each layer are staggered with respect to those of the adjacent layers.
  • the amount of stagger may be expressed as of the width of a tape, in which case the dielectric can be seen to be formed of a number of superposed groups of n, layers. 20,11 0f which pings.
  • each group is an approximate repetition of the underlying group as regards the location of the helical gas spaces in the group. With accurate lapping the effective strength under surge conditions of each group is of that of a convolute wrapping of the same wall thickness. Should however two spaces in two successive layers of a group coincide at any point due to inaccurate application of the tapes or, as a result of a tape breakage, should the radial thickness of the space at the break be doubled by making a lap joint between the broken ends, the strength of the group will be reduced from If such a fault occurs in the polystyrene layer, the stress across the impregnated paper beyond the fault will be increased.
  • n should be as large as possible. It is however limited by the need for adequate lateral spacing of the gaps in adjacent layers. In practice a spacing of 25% of the width of the tape is desirable giving n a value of 4. With perfect lapping at such spacing the effective strength under surge conditions of the polystyrene portion of the dielectric will be of a convolute wrapping of the same wall thickness. The effect of a coincidence of two butt spaces in two successive layers will be to reduce this gure of '75% as will be more easily appreciated from a consideration of Figure 2 which of course is not to scale.
  • An enlarged space is shown at X1 in the right hand section where the second layer butt spaces inadvertently coincide with those of the underlying layer. This will reduce the effective strength of the polystyrene portion of the dielectric to an extent dependent upon the radial location of the coincident spaces and upon the number of layers.
  • the effective surge strength of the polystyrene portion should, inpractice, be about of the optimum value of '75%. It will be apparent that with fourteen layers the effective strength of the polystyrene wall will be about 85% of the optimum value of 75%, it being assumed that the chances of a second imperfection in the second and third groups occurring in radial alignment with an imperfection in the first group are negligible.
  • the maximum stress in the polystyrene would be 1150 kv./cm., which is well below 1250 kv./cm., the surge breakdown stress of the polystyrene iilm.
  • the cable is therefore more surge resistant than cable having a dielectric of the same radial dimensions built up wholly7 of pre-impregnated paper for under similar surge conditions the stress in the paper at the surface or the conductor of such a cable would be 910 kv./cm. Which is greater than 800 kv./cm. which is the surge breakdown strength of pre-impregnated paper when used alone.
  • the modified cable is more surge resistant than an all paper insulated cable of the same dimensions and is comparable as regards its surge strength with a cable having a dielectric consisting of an inner part built up entirely of polystyrene lm and an outer part built up of pre-impregnated paper, in accordance with the invention disclosed in the specification of our prior patent application No. 40,450.
  • a super-tension cable comprising a conductor, a plurality of helical lappings of insulating material on said conductor forming an intersticed laminated body of dielectric surrounding said conductor, a gas-impervious enclosure surrounding said body of dielectric, and under operating conditions gas under super-atmospheric pressure filling the interstices in said laminated body, said laminated body comprising an inner part built up of alternate single strip layers of oriented polystyrene film and layers of pre-impregnated paper, and an outer part built up of layers of pre-impregnated paper, said inner part comprising at least fourteen layers and having a radial wall thickness of not less than 10% of the radius of the conductor surface and not more than of the combined radial Wall thickness of said inner and outer parts.
  • a super-tension cable comprising a conductor, a plurality of helical lappings of insulating material on said conductor formingan intersticed laminated body of dielectric surrounding said conductor, a gas-impervious enclosure surrounding said body of dielectric, and under operating conditions gas under super-atmospheric pressure lling the interstices in said laminated body, said laminated body comprising an innel part built up of alternate single strip layers of oriented polystyrene lm of which the thickness is about 4 mils and layers of pre-impregnated paper of which the thickness is about 2.5 mils, and an outer Ipart built up of layers of pre-impregnated paper, said inner part comprising at least fourteen layers vand having a radial Wall thickness of not less than 10% of the radius 0f the conductor surface and not more than 45% of the combined radial Wall thickness of said inner and outer parts.

Landscapes

  • Organic Insulating Materials (AREA)
  • Insulated Conductors (AREA)
  • Laminated Bodies (AREA)
  • Ropes Or Cables (AREA)
US187040A 1947-08-05 1950-09-27 Gas-filled electric cable with paper and polystyrene insulation Expired - Lifetime US2650261A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB270121X 1947-08-05
GB26332/49A GB675224A (en) 1947-08-05 1949-10-13 Improvements in electric cables

Publications (1)

Publication Number Publication Date
US2650261A true US2650261A (en) 1953-08-25

Family

ID=32299785

Family Applications (1)

Application Number Title Priority Date Filing Date
US187040A Expired - Lifetime US2650261A (en) 1947-08-05 1950-09-27 Gas-filled electric cable with paper and polystyrene insulation

Country Status (7)

Country Link
US (1) US2650261A (en, 2012)
BE (3) BE498509A (en, 2012)
CH (2) CH270121A (en, 2012)
DE (2) DE914507C (en, 2012)
FR (4) FR969538A (en, 2012)
GB (2) GB625512A (en, 2012)
NL (2) NL141712B (en, 2012)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2782248A (en) * 1951-06-01 1957-02-19 Gen Electric Electrical cable structure
US2980755A (en) * 1958-01-20 1961-04-18 British Insulated Callenders Electric cables
US3078333A (en) * 1963-02-19 High voltage power cable
US4415761A (en) * 1980-06-06 1983-11-15 Societa Cavi Pirelli Societa Per Azioni Taped electric cable
US4774382A (en) * 1986-07-16 1988-09-27 Societa' Cavi Pirelli S.P.A. Direct current cable insulation with insulating composition including electronegative gas

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2440883A (en) * 1943-02-24 1948-05-04 Avco Mfg Corp Lubricating system for internalcombustion engines
US4039740A (en) * 1974-06-19 1977-08-02 The Furukawa Electric Co., Ltd. Cryogenic power cable
US4487991A (en) * 1983-07-15 1984-12-11 The United States Of America As Represented By The United States Department Of Energy Fully synthetic taped insulation cables

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2068940A (en) * 1934-06-23 1937-01-26 Okonite Co Electric cable
US2093411A (en) * 1933-09-20 1937-09-21 Enfield Cable Works Ltd Protective coating and sheathing for cables, pipes, and the like
US2102974A (en) * 1934-06-22 1937-12-21 Callenders Cable & Const Co Electric cable
US2289734A (en) * 1938-01-11 1942-07-14 Int Standard Electric Corp Electric power cable
US2309992A (en) * 1937-12-24 1943-02-02 Int Standard Electric Corp Electric power cable

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2093411A (en) * 1933-09-20 1937-09-21 Enfield Cable Works Ltd Protective coating and sheathing for cables, pipes, and the like
US2102974A (en) * 1934-06-22 1937-12-21 Callenders Cable & Const Co Electric cable
US2068940A (en) * 1934-06-23 1937-01-26 Okonite Co Electric cable
US2309992A (en) * 1937-12-24 1943-02-02 Int Standard Electric Corp Electric power cable
US2289734A (en) * 1938-01-11 1942-07-14 Int Standard Electric Corp Electric power cable

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3078333A (en) * 1963-02-19 High voltage power cable
US2782248A (en) * 1951-06-01 1957-02-19 Gen Electric Electrical cable structure
US2980755A (en) * 1958-01-20 1961-04-18 British Insulated Callenders Electric cables
US4415761A (en) * 1980-06-06 1983-11-15 Societa Cavi Pirelli Societa Per Azioni Taped electric cable
US4774382A (en) * 1986-07-16 1988-09-27 Societa' Cavi Pirelli S.P.A. Direct current cable insulation with insulating composition including electronegative gas

Also Published As

Publication number Publication date
DE1063667B (de) 1959-08-20
FR60497E (fr) 1954-11-03
BE484104A (en, 2012)
GB625512A (en) 1949-06-29
NL77748C (en, 2012)
DE914507C (de) 1954-07-05
FR72319E (fr) 1960-04-06
FR969538A (fr) 1950-12-21
CH270121A (de) 1950-08-15
NL141712B (nl)
BE498509A (en, 2012)
GB817616A (en) 1959-08-06
CH288079A (de) 1952-12-31
FR61032E (fr) 1955-03-23
BE498508A (en, 2012)

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