EP0202878A1 - Liquid-insulated tap-changer - Google Patents

Liquid-insulated tap-changer Download PDF

Info

Publication number
EP0202878A1
EP0202878A1 EP19860303735 EP86303735A EP0202878A1 EP 0202878 A1 EP0202878 A1 EP 0202878A1 EP 19860303735 EP19860303735 EP 19860303735 EP 86303735 A EP86303735 A EP 86303735A EP 0202878 A1 EP0202878 A1 EP 0202878A1
Authority
EP
European Patent Office
Prior art keywords
liquid
ester
tap
changer according
insulated tap
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.)
Granted
Application number
EP19860303735
Other languages
German (de)
French (fr)
Other versions
EP0202878B1 (en
Inventor
Fred Berry Waddington
Andreas Kallinicos
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.)
Micanite & Insulators Co Ltd
Original Assignee
Micanite & Insulators 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
Application filed by Micanite & Insulators Co Ltd filed Critical Micanite & Insulators Co Ltd
Publication of EP0202878A1 publication Critical patent/EP0202878A1/en
Application granted granted Critical
Publication of EP0202878B1 publication Critical patent/EP0202878B1/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/20—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils

Definitions

  • the present invention relates to switchgear, and in particular relates to fluid-insulated tap-changers.
  • Fluid-insulated tap-changers are employed for light-duty switching in a variety of applications, such as distribution transformer installations, underground railways and the like, where repeated on-load switching of currents of up to about 500A at voltages of typically a few kV is required.
  • a tap-changer may perform 20,000 to 30,000 make and break cycles annually, and a working life of a minimum of 20 years is normally expected.
  • tap-changer electrodes are subject to considerable wear in use, and for the same reason the dielectric fluid in a tap-changer quickly becomes contaminated with carbon and other arcing products, which in turn tend to cause the electrodes to wear more rapidly.
  • fluid-insulated tap-changers are distinguished from fluid-insulated switchgear in general by the requirement to renew their dielectric liquid at frequent intervals throughout their working life and also by the requirement that the dielectric liquid employed should be compatible with an absolute minimum of electrode wear.
  • the problem of electrode wear is less severe in heavy duty switchgear for example, even though such switchgear may switch currents of perhaps several kA at several tens of kV.
  • BS148 petroleum oil has the following disadvantages; a) it is highly inflammable b) it can have poor lubricating properties c) it can freeze at -20°C and d) being a natural petroleum product the molecular structure can contain various aromatic structures of questionable toxicity or carcinogeneticy. Also in operation in a tap-changer or switch, petroleum oil evolves large quantities of hydrogen and other flammable gases, and produces large quantities of colloidal carbon which requires periodic removal.
  • a liquid insulated tap-changer incorporates a dielectric liquid which includes as a major constituent one or more monomeric or polymeric esters of the general formula: wherein R' are the same or different alkyl groups having five to ten carbon atoms, and R are independently H or Me or Et or or (in the case that the ester is polymeric)
  • the dielectric liquid may comprise a single said ester or a mixture of such esters.
  • each R is or one R is ethyl and the other R is CH 2 -0-C-R'.
  • R' is preferably hexyl (C 6 ), heptyl (C 7 ) or octyl (C 8 ).
  • R' may be a straight chain or a branched chain alkyl group.
  • Preferred esters for use in accordance with the invention are esters (particularly tetra-esters) of pentaerythritol (C (CH 2 OH) 4 ) and heptanoic or octanoic (particularly the n-heptanoic and n-octanoic) acid.
  • Esters of trimethylol propane are also suitable, particularly when the acid is heptanoic or octanoic acid.
  • esters trimethylol-propane triheptanoate, trimethylol-propane tricaprylate and pentaerythritol tetrapelargonate and listed their viscosities, boiling points, electrical loss tangents (tan6), resistivities, permittivities, electrical breakdown strengths, fire points and autoignition temperatures.
  • esters in accordance with the invention when used as dielectric liquids in tap-changers, significantly reduce contact erosion in comprison with tap-changers which utilise petroleum oil (which has previously been considered the best dielectric fluid for tap-changers). Furthermore the esters of the present invention form only a small fraction of the carbon produced by petroleum oil in tap-changers, and the carbon produced by the esters of the present invention is less colloidal and separates more readily to leave a cleaner system. Thus, by using the esters of the present invention in tap-changers the overall life of the tap-changer may be increased and the required maintenance may be reduced.
  • the fire point was determined by the method specified in the Institute of Petroleum handbook No. 36/63
  • the pour point was determined by the method specified in the Institute of Petroleum Handbook No. 15/67 (ASTM Designation D97-66)
  • the type testing involved 20,000 make and break operations in a 33kV 500 amp High Speed Resistor Transition Tap-Changer.
  • esters produced from different batches of acid may be necessary in order to achieve the desired pour point, fire point, viscosity or other characteristics.
  • the precise composition is not critical, but it should be noted that the electrical properties, especially the loss tangent and the resistivity, improve with increasing molecular weight and increasing symmetry of the ester molecule.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Organic Insulating Materials (AREA)
  • Lubricants (AREA)

Abstract

A liquid insulated tap-changer in which the dielectric liquid includes as a major constituent a monomeric or polymeric ester of the general formula:
Figure imga0001
wherein R' are the same or different alkyl groups having five to ten carbon atoms, and R are independently H or Me or Et or
Figure imga0002
or (in the case that the ester is polymeric)

Description

  • The present invention relates to switchgear, and in particular relates to fluid-insulated tap-changers.
  • Fluid-insulated tap-changers are employed for light-duty switching in a variety of applications, such as distribution transformer installations, underground railways and the like, where repeated on-load switching of currents of up to about 500A at voltages of typically a few kV is required. Typically a tap-changer may perform 20,000 to 30,000 make and break cycles annually, and a working life of a minimum of 20 years is normally expected. Owing to their frequent make and break cycles, tap-changer electrodes are subject to considerable wear in use, and for the same reason the dielectric fluid in a tap-changer quickly becomes contaminated with carbon and other arcing products, which in turn tend to cause the electrodes to wear more rapidly. Consequently fluid-insulated tap-changers are distinguished from fluid-insulated switchgear in general by the requirement to renew their dielectric liquid at frequent intervals throughout their working life and also by the requirement that the dielectric liquid employed should be compatible with an absolute minimum of electrode wear. The problem of electrode wear is less severe in heavy duty switchgear for example, even though such switchgear may switch currents of perhaps several kA at several tens of kV.
  • Thus although a fairly wide range of dielectric liquids have been used for switchgear in general the only insulating fluid found suitable for tap-changers and similar light-duty switching has been petroleum oil to BS148 insulating specification. However, BS148 petroleum oil has the following disadvantages; a) it is highly inflammable b) it can have poor lubricating properties c) it can freeze at -20°C and d) being a natural petroleum product the molecular structure can contain various aromatic structures of questionable toxicity or carcinogeneticy. Also in operation in a tap-changer or switch, petroleum oil evolves large quantities of hydrogen and other flammable gases, and produces large quantities of colloidal carbon which requires periodic removal. Up to recently attempts to replace petroleum oil with an alternative less flammable fluid has not met with complete success. Dielectrics based on halogenated oils such as polychlorinated biphenyls fluorinated oils or mixtures of halogenated chlorofluoro compounds have resulted in the formation of large quantities of toxic or corrosive products such as hydrochloric acid or hydrolysable fluorides. Experience has also shown that there is in addition a marked increase in contact erosion with such fluids. Other fluids based on silicone materials such as dimethylsiloxane and phenylmethyl siloxanes have also been found to be unsatisfactory due to the formation of silica and gelatinous silicone polymers on arcing during switching which effectively abrade electrodes/contacts and can cause insulating films of fused silica to be formed on the contacts.
  • According to the present invention, a liquid insulated tap-changer incorporates a dielectric liquid which includes as a major constituent one or more monomeric or polymeric esters of the general formula:
    Figure imgb0001
    wherein R' are the same or different alkyl groups having five to ten carbon atoms, and R are independently H or Me or Et or
    Figure imgb0002
    or (in the case that the ester is polymeric)
    Figure imgb0003
  • The dielectric liquid may comprise a single said ester or a mixture of such esters.
  • Preferably in an ester employed in a dielectric liquid according to the invention each R is
    Figure imgb0004
    or one R is ethyl and the other R is CH2-0-C-R'. R' is preferably hexyl (C6), heptyl (C7) or octyl (C8). R' may be a straight chain or a branched chain alkyl group. Preferred esters for use in accordance with the invention are esters (particularly tetra-esters) of pentaerythritol (C (CH2 OH)4) and heptanoic or octanoic (particularly the n-heptanoic and n-octanoic) acid. Esters of trimethylol propane (particularly 1, 1, 1 trimethylol propane), di-trimethylol propane and dipentaerythritol ( (CH 2 OH)3C-CH2-0-CH2-C(CH20H)3) are also suitable, particularly when the acid is heptanoic or octanoic acid.
  • The use of certain aliphatic esters as insulating fluids in fluid-insulated electrical apparatus in general is disclosed in our U.K. Patent No. 1602092, which is hereby incorporated by reference. Specifically, this patent disclosed the esters trimethylol-propane triheptanoate, trimethylol-propane tricaprylate and pentaerythritol tetrapelargonate and listed their viscosities, boiling points, electrical loss tangents (tan6), resistivities, permittivities, electrical breakdown strengths, fire points and autoignition temperatures. However this patent did not suggest that any of the esters of the present invention were suitable for use in tap-changers and in particular did not disclose the amount of contact erosion or carbon production which arises when the esters are used in tap-changers. These two parameters are very important in tap-changer applications but are much less important in most other types of switchgear applications.
  • We have unexpectedly found that esters in accordance with the invention, when used as dielectric liquids in tap-changers, significantly reduce contact erosion in comprison with tap-changers which utilise petroleum oil (which has previously been considered the best dielectric fluid for tap-changers). Furthermore the esters of the present invention form only a small fraction of the carbon produced by petroleum oil in tap-changers, and the carbon produced by the esters of the present invention is less colloidal and separates more readily to leave a cleaner system. Thus, by using the esters of the present invention in tap-changers the overall life of the tap-changer may be increased and the required maintenance may be reduced.
  • The esters of the present invention are considered to be of low toxicity and have the following known advantages over petroleum oil:
    • a) the esters can be formulated to be fire resistant i.e. they can readily comply with national fire specifications for a low flammability insulating fluid (fire point above 300 0 C).
    • b) smaller amounts of hydrogen and other flammable gases are produced on arcing.
  • An example of one ester mixture employed in a tap-changer in accordance with the invention consists of pentaerythritol tetra-heptanoate and pentaerythritol tetra-octanoate esters having a composition as follows:
    Figure imgb0005
  • The advantages of this ester mixture can be seen from the following table which lists comparative data for BS148 petroleum oil, fluoropentane, and the ester mixture.
    Figure imgb0006
  • In each case, the fire point was determined by the method specified in the Institute of Petroleum handbook No. 36/63, the pour point was determined by the method specified in the Institute of Petroleum Handbook No. 15/67 (ASTM Designation D97-66), and the type testing involved 20,000 make and break operations in a 33kV 500 amp High Speed Resistor Transition Tap-Changer.
  • It will be appreciated that in practice, commercially available mixtures of aliphatic acids may be reacted with the alcohol to form the required esters, and that appropriate blending of esters produced from different batches of acid may be necessary in order to achieve the desired pour point, fire point, viscosity or other characteristics. In general the precise composition is not critical, but it should be noted that the electrical properties, especially the loss tangent and the resistivity, improve with increasing molecular weight and increasing symmetry of the ester molecule.

Claims (11)

1. A liquid insulated tap-changer incorporating a dielectric liquid which includes as a major constituent one or more monomeric or polymeric esters of formula:
Figure imgb0007
wherein R' are the same or different alkyl groups having five to ten carbon atoms, and R are independently H or Me or Et or
Figure imgb0008
or (in the case that the ester is polymeric)
Figure imgb0009
2. A liquid insulated tap-changer according to Claim 1 wherein the dielectric liquid incorporates a said ester, in which each R is
Figure imgb0010
3. A liquid insulated tap-changer according to Claim 1 wherein the dielectric liquid incorporates a said ester in which one R is ethyl and the other R is
Figure imgb0011
4. A liquid insulated tap-changer according to Claim 1 wherein the dielectric liquid incorporates a said ester, in which R' is hexyl (C6), heptyl (C7) or octyl (C 8).
5. A liquid insulated tap-changer according to Claim 4 wherein R' is a straight chain or a branched chain alkyl group.
6. A liquid insulated tap-changer according to any preceding Claim wherein the dielectric liquid incorporates, as a said ester, an ester of pentaerythritol and heptanoic or octanoic acids.
7. A liquid insulated tap-changer according to any one of Claims 1 to 5 wherein the dielectric liquid incorporates as a said ester an ester of trimethyl propane, di-trimethylol propane or dipentaerythritol and heptanoic or octanoic acid.
8. A liquid insulated tap-changer according to Claim 1 wherein the dielectric liquid comprises a mixture of pentaerythritol tetra-heptanoate and pentaerythritol tetra-octanoate esters.
9. A liquid insulated tap-changer according to Claim 1 wherein the dielectric liquid comprises an ester mixture having the following compositions:-
Figure imgb0012
10. A dielectric liquid suitable for use in a liquid insulated tap-changer according to any preceding Claim and comprising an ester or mixture of esters of pentaerythritol and heptanoic or octanoic acid.
11. A dielectric liquid suitable for use in a liquid insulated tap-changer according to any preceding Claim and comprising an ester or mixture of esters of trimethyl propane or dipentaerythritol with heptanoic or octanoic acid.
EP19860303735 1985-05-17 1986-05-16 Liquid-insulated tap-changer Expired EP0202878B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB858512488A GB8512488D0 (en) 1985-05-17 1985-05-17 Fluid-insulated switchgear
GB8512488 1985-05-17

Publications (2)

Publication Number Publication Date
EP0202878A1 true EP0202878A1 (en) 1986-11-26
EP0202878B1 EP0202878B1 (en) 1989-02-01

Family

ID=10579273

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19860303735 Expired EP0202878B1 (en) 1985-05-17 1986-05-16 Liquid-insulated tap-changer

Country Status (3)

Country Link
EP (1) EP0202878B1 (en)
DE (1) DE3662016D1 (en)
GB (2) GB8512488D0 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2229583A (en) * 1989-03-15 1990-09-26 Alsthom Gec High temperature transformers
EP0787792A1 (en) * 1996-02-01 1997-08-06 New Technology Management Co., Ltd. Electro-sensitive movable fluids, methods of using the same and motors for the electro-sensitive movable fluids
US6495071B1 (en) 1996-02-01 2002-12-17 New Technology Management Co., Ltd. Method of using electro-sensitive movable fluids
WO2005118756A1 (en) * 2004-05-27 2005-12-15 Cognis Ip Management Gmbh Polyol ester for transformers

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3894959A (en) * 1972-10-17 1975-07-15 Exxon Research Engineering Co Mixed carboxylic acid esters as electrical insulating oils
GB1602092A (en) * 1978-05-25 1981-11-04 Micanite & Insulators Co Ltd Fluid insulated electrical apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3894959A (en) * 1972-10-17 1975-07-15 Exxon Research Engineering Co Mixed carboxylic acid esters as electrical insulating oils
GB1602092A (en) * 1978-05-25 1981-11-04 Micanite & Insulators Co Ltd Fluid insulated electrical apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"New Dielectric Fluids for Power Engineering" organised by Professionel Group Committee S2 (Materials, Science and Technology) 1980-03-12, Digest number 1980/14 * PAGES 3/1-4/3 * *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2229583A (en) * 1989-03-15 1990-09-26 Alsthom Gec High temperature transformers
EP0787792A1 (en) * 1996-02-01 1997-08-06 New Technology Management Co., Ltd. Electro-sensitive movable fluids, methods of using the same and motors for the electro-sensitive movable fluids
US6030544A (en) * 1996-02-01 2000-02-29 New Technology Management Co., Ltd. Electro-sensitive movable fluids, methods of using the same and motors for the electro-sensitive movable fluids
US6495071B1 (en) 1996-02-01 2002-12-17 New Technology Management Co., Ltd. Method of using electro-sensitive movable fluids
WO2005118756A1 (en) * 2004-05-27 2005-12-15 Cognis Ip Management Gmbh Polyol ester for transformers

Also Published As

Publication number Publication date
GB8512488D0 (en) 1985-06-19
GB2175311A (en) 1986-11-26
EP0202878B1 (en) 1989-02-01
GB8611961D0 (en) 1986-06-25
DE3662016D1 (en) 1989-03-09
GB2175311B (en) 1988-08-10

Similar Documents

Publication Publication Date Title
McShane Relative properties of the new combustion-resist vegetable-oil-based dielectric coolants for distribution and power transformers
US4082866A (en) Method of use and electrical equipment utilizing insulating oil consisting of a saturated hydrocarbon oil
CN101273416B (en) A mineral insulating oil, a process for preparing a mineral insulating oil, and a process for using a mineral insulating oil
EP1969607B1 (en) A composition of insulating fluid and process for the preparation thereof
US4266264A (en) Meta isopropyl biphenyl insulated electrical apparatus
EP0202878B1 (en) Liquid-insulated tap-changer
US3673093A (en) Liquid dielectric composition of alkyl benzene and an antioxidation stabilizer
CA2304708C (en) Food grade dielectric fluid
GB2124253A (en) Dielectric fluids
US6391228B1 (en) Dielectric composition having an improved gas absorption
CA1086487A (en) Insulating oil, method of use and electrical equipment utilizing said oil
US2105407A (en) Liquid insulating composition
EP2082406A1 (en) Electrical oil composition
CA1339673C (en) Perchloroethylene dielectric fluid containing aliphatic hydrocarbons
GB1602092A (en) Fluid insulated electrical apparatus
JP2003500520A (en) High stress electrical insulating oil
US2012301A (en) Halogenated polyphenyl ketone
McShane Relative properties of the new combustion resistant vegetable oil based dielectric coolants
US2122278A (en) Fluorinated paraffin wax
CA1079951A (en) Electrical devices containing improved dielectric fluids
US4401871A (en) Halogenated hydrocarbon compositions and electrical apparatus containing such compositions
WO1997004465A1 (en) Electrical insulating oil based compound and its use
JPS59142293A (en) Lubricant composition for electric contact
KR101384267B1 (en) Vegetable insulating oil composition
US1944730A (en) Composition for dielectric use

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR IT NL

17P Request for examination filed

Effective date: 19861219

17Q First examination report despatched

Effective date: 19880208

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR IT NL

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

REF Corresponds to:

Ref document number: 3662016

Country of ref document: DE

Date of ref document: 19890309

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19910429

Year of fee payment: 6

ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19910531

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19910729

Year of fee payment: 6

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19921201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930129

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930202

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050516