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Oil - SF6

bushings, type GOEK

Technical guide

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This Technical Guide has been produced to allow transformer manufacturers, and theirdesigners and engineers, access to all the technical information required to assist them intheir selection of the appropriate transformer bushing. The guide should be used inconjunction with the Selection Guideto allow the optimum selection to be made.

The technical information pertaining to bushings manufactured by ABB has been dividedinto separate documents, with one document for each type.

The information provided in this document is intended to be general and does not coverall possible applications. Any specific application not covered should be referred directlyto ABB, or its authorised representative.

ABB makes no warranty or representation and assumes no liability for the accuracy of theinformation in this document or for the use of such information. All information in thisdocument is subject to change without notice.

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Table of ContentsDesign ______________________ 4

Test tap ____________________________ 5

Testing _______________________ 5Test tap adapter _____________________ 5

Dimensions ___________________ 6

Electrical data _________________ 7Common specification ________________ 7

Connection details______________ 8Draw rod system with standard bottomcontact ____________________________ 8Tight bottom contact __________________ 8SF

6side terminal_____________________ 8

Data for end-shields ____________ 9

Conductor loading ______________ 10Short-time current ____________________ 10

Overload capacity of bushings __________ 10

Ordering particulars _____________ 10

Recommendations for positioning __ 11

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DesignBushing type GOEK is intended for immersed oil-SF

6

service and can be mounted in any direction from

vertical to horizontal. It can also be used for oil-oilapplications. The bushing is built up around a centretube on which the condenser body is wound. The con-denser body is wound from full width insulating paper.

The foils are located so that the best possiblecombination of external flashover withstand and internalpuncture strength is achieved.

The insulators and the mounting flange are held by thecentre tube and sealing is accomplished by oil-resistantrubber gaskets in grooves.

A set of concentric tubes is prestressed and serves as a

spring which holds the main bushing componentstogether and provides adequate pressure on the gasketsat all expected temperatures, load conditions andmounting directions.

The annular space formed between the tubes makes anefficient cooling duct for heat dissipation, thus improvingthe current-carrying capacity and thermal stability of thebushing.

The bushing is equipped with an expansion tank in whicha nitrogen-filled rubber bellows is mounted. This is anadvantage since it permits mounting at any angle from

vertical to horizontal, and also facilitates mounting onthe transformer without further connection to separateexpansion tanks.

Variations in the length of the centre tube and thehousing are compensated by a flexible connection insidethe top housing. The mounting flange is an aluminiumalloy casting, which is protected by a two-componentprimer and two-component grey-blue paint. The surfaceroughness of the gasket area is Ra 6.3 on the oil sideand Ra 1.6 on the SF

6side.

On the mounting flange there is a test tap. This tap isautomatically earthed by a protective cap when the tap

is not connected to external test or measuring circuits.

To detect possible gas leakage, the bushing can beequipped with an oil pressure monitoring equipment.

The connection of the bushing to the transformer can bemade with the draw-rod or tight bottom contact.

The bushing tube between the SF6side and the trans-

former is sealed in two ways. One seal is made by theSF

6terminal and the other by a plug in the centre tube or

by a tight bottom contact.

The mounting flange is equipped with an extension on

the oil side to provide space for current transformers.Extension lengths 300 and 600 mm are available. GOEK1675 can also be supplied without flange extension.

Fig. 1. Transformer bushing type GOEK.

The bushing requires a shield at the oil side. The pur-pose of this shield is to avoid excess voltages in the oil

at the bottom end nut and at the connection between theinsulated lead from the transformer winding and thebottom contact in the bushing. The maximum voltage inthe oil at the surface of the shield insulation must belimited to values that are normal for insulated conductorsand similar components in the same transformer.

ABB manufactures shields of this type - these arequoted for and supplied separately. The shields aremade of aluminium and are insulated with epoxy orpressboard. The shield may be mounted on the bottomend nut of the bushing, or on the bottom contact of thedraw rod.

Top housing

SF6

side terminal

Flexible connection

Pre-stressed tubes

Test tap onopposite side,see Fig. 2

M12 forearthing device

Extension forcurrenttransformers

Condenser body

Transformer oil

Bottom end nut

Bottom contact

Porcelaininsulator

Valve forconnection topressure sensor

Mounting flange

Expansion tankwith rubberbellows

Porcelaininsulator

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Test tap

The GOEK bushings are equipped with a test tapconnected to the outer layer of the condenser body. Thetest voltage of the tap is 20 kV, 50 Hz for one minute.Maximum service voltage is 6 kV.

In connection with an external capacitance, the test tapcan be used as a voltage tap. The test tap hasdimensions according to IEEE, Potential tap type A.

Fig. 2. Test tap.

TestingA tightness test is carried out on the assembled bushingafter the final drying and impregnation. The test iscarried out according to IEC 60137. Each bushing issubjected to a final electrical routine test. The test ismade at room temperature with the bushing submerged

in transformer oil. Capacitance and tan d are measuredin steps up to the power frequency withstand voltage,which is held for one minute.

Capacitance and tan d are also measured with decrea-sing voltage at the same voltage levels as before theone minute test. Measurements for detection of internalpartial discharge (PD-measurements) are also made.These measurements are carried out at the same time,and at the same levels, as the tan d test. It is alwaysdemonstrated that the PD-value is maximum 5 pC at atest voltage level equal to the rated system voltage.

Electrical testing is carried out according to IEC 60137and IEC 61639, i.e. the gas side is placed in a metalcylinder filled with insulating gas at the pressure of 0.35MPa (absolute) and with the diameter 450/540/650 forGOEK 1050/1425/1675 respectively.

NOTE:Dimensions of the bushings do not meetrequirements shown in IEC 61639, Table 3.

During testing of the transformer, a bushing type GOEK1050 can be replaced by a bushing type GOE 900-650; abushing type GOEK 1425 can be replaced by a bushingtype GOE 1300-1150; and a bushing type GOEK 1675can be replaced by a bushing type GOE 1675-1175.

Test tap adapter

For permanent connection of the test tap to measuringcircuits, a test tap adapter is required. Catalogue number2769 522-C.

Fig. 3. Test tap adapter.

(Pg 16 acc. to DIN 40430)Turnable in optional directionPr 22.5

goek_011

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Fig. 4. Dimensions.* For bushings with tight bottom contact, see Fig. 6 for definition of L5.

Flange SF6

side

Position of test tap

Position of pressuresensor

Flange oil sideEarthed layer

M12 For earthing device

DimensionsAll dimensions in millimetres unless otherwise stated.

Type Extension Type Catalogue L1 L2 L3 L4 L5 L6 L7 L8GOEK for current bottom number

transformers contactmm

1050 300 Standard LF 124 001-B 450 885 305 325 835 230 395 740

1050 300 Tight LF 124 011-B 305 325 9051050 600 Standard LF 124 001-C 605 625 1135

1050 600 Tight LF 124 011-C 605 625 1205

1425 300 Standard LF 124 002-B 650 1090 305 315 1035 350 545 520

1425 300 Tight LF 124 012-B 305 315 1105

1425 600 Standard LF 124 002-C 605 615 1335

1425 600 Tight LF 124 012-C 605 615 1405

1675 0 Standard LF 124 003-A 880 1395 5 150 985 350 695 915

1675 0 Tight LF 124 013-A 5 150 1055

1675 300 Standard LF 124 003-B 305 360 1285

1675 300 Tight LF 124 013-B 305 360 1355

1675 600 Standard LF 124 003-C 605 640 1585

1675 600 Tight LF 124 013-C 605 640 1655

Table 1. Dimensions.

*

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Electrical data

D1 D2 D3 D4 D5 t Mass Cantilever load, Nkg In operation Test

at mounting forangle 60 s0-30 >30

20 (8x) 350 400 244 264 23 180 2500 1500 5000

180200 2500 1500 5000

200

20(8x) 430 480 244 330 23 285 2500 1500 5000

285

320 2500 1500 5000

320

24 (12x) 660 720 344 428 30 495 2500 1500 5000

495

540 2500 1500 5000

540

575 2500 1500 5000

575

For conditions exceeding the standard specification above, please consult ABB.

ReducedRated current for Nominal capacitances

current 1) horizontal between conductor andRated Dry Dry at mounting mounting test tap C1 10 %

Rated phase-to- lightning switching Routine test angle and up to pFvoltage earth voltage impulse impulse 1 min. dry 0 - 75 15 from

Type Ur UY LI SI 50 Hz Ir horizontal Flange extension, mmGOEK kV, r.m.s. kV, r.m.s. kV, peak kV, peak kV, r.m.s. A A 0 300 600

1050 245 170 1050 850 460 2500 1600 274 3641425 420 245 1425 1175 630 2500 1600 263 3351675 550 318 1675 1300 750 2500 1600 231 253 308

Table 2. Electrical data. The electrical data are valid in accordance with criteria in IEC 61639 "Direct connectionbetween power transformers and gas-insulated switchgear".1) 5000 A available on request.

Transformers

Oil impregnated paper, capacitance graded, completely immersed bushing

+40 C to -40 C, minimum value acc. to temperature class 2 of IEC 60137

< 1 000 m

Transformer oil. Maximum daily mean oil temperature 90 C. Maximum temporary oil temperature 115 C.

Maximum 30 mm

100 kPa over pressure

Conforming to IEC/ IEEE

Application:

Classification:

Ambient temperature:

Altitude of site:

Immersion medium:

Oil level below bushing flange:

Max. pressure of medium:

Markings:

Common specifications

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Connection detailsDraw rod system with standard bottom

contactThe centre tube of the bushing is used as currentconductor. The transformer leads are fitted with cablelugs, which are bolted to a bottom contact. This contactis drawn against the bottom end nut by a thin steel drawrod. See Fig. 5.

Bottom contacts with 4 or 6 threaded holes (N1=4 orN1=6) for cable lugs are available. The bottom contactsare made of copper in one piece and have roundededges, so that they may be used without any shield forlow insulation levels.

At the level of the flange the draw rod is split into twoparts. If required to meet the transport conditions, wecan position a joint at any desired level below the flange.This must be stated in the order. The lower part withcontact and shield can then be secured to the coverduring transport and storage of the transformer. Thissystem has the following additional advantagescompared to other methods used for high currents:

No hand holes required in the transformer tank.

The centre tube is used as conductor.

No special supports required in the transformer as the

case with plug contacts.

Perfect guiding of the bushing into the transformer.

The end shield may be fixed to the bottom contact

and will thus be correctly positioned with respect tothe bottom end nut (for contact with N1=6).

No mechanical forces exerted on the leads from the

transformer winding at any time.

Tight bottom contact

A system with tight bottom contact is also available.This system consists of a bottom contact with 4

threaded holes. The bottom contact is soldered togetherwith the bottom end nut. See Fig. 6.

SF6

side terminal

The terminal stud assembly consists of a stud, a tight-ening ring, a gasket, bolts and washers. The tighteningring is made of stainless steel in order to separate thecopper and aluminium parts and thus avoid corrosion.The electrical contact function and the sealing functionare completely separated.

The stud is first fastened to the bushing top with 6 bolts,which provide proper electrical contact. The contactsurface is located inside the gasket and is thereby wellprotected from corrosion. Finally the tightening ring withthe gasket is pressed against the stud by means of 6additional bolts.

Fig. 5. Draw rod system with standard bottom contacts.

Fig. 6. Tight bottom contact.

SF6

sideterminal

Flange oil side

Threaded hole M8for pulling wire

Additionaljoint

M12

M12

L5

Fig. 7. Terminal stud, SF6

side.

LF 170 050-AA(Aluminium)orLF 170 050-AL(Copper, silver-plated)

LF 170 050-AH (Copper, silver-plated)

M12N1=4 N1=6

goek_012

H1L5L5

19

goek_031

240

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9

Data for end-shieldsThe maximum voltages in the oil at the surface of theshield insulation and the parts surrounding the bushing

must be limited to those values normal for insulatedconductors and other similar components in the sametransformer.

The withstand voltages in a specific case depend uponmany factors beyond the control of the bushingmanufacturer. Therefore the configurations anddistances given below are only intended as guide lines.

U = Power frequencyLI = Lightning impulse

Fig. 9. Recommended minimum distance A for differentshields and test voltages.

To be used Dimensions according to Fig. 8 (mm) Mass Epoxy PressboardShield with GOEK D4 D5 H4 H5 H5 H6 R1 R2 R3 kg Cat. No. insulated insulated 1)

(tight bottom

contact)

U 1050-1425 262 174 265 170 100 90 492 30 8 2.1 LF 170 046 -U -UP

V 1675 352 200 365 240 170 120 351 24 14 2.5 LF 170 046 -V -VP

Table 3. Insulated shield, oil side.1) All dimensions refer to the epoxy insulated shield, which is used as a base. The thickness of the pressboard is 3 mm for -UP and -VP.

Fig. 10. Mounting alternatives, oil side.

Fig. 8. Shield, oil side.

LF 170 046-F

Fig. 11. Shield, SF6

side.

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Supply voltage Catalogue number

230 V AC LF 410 024-K115 V AC LF 410 024-L

Table 6. Pressure monitoring equipment. (For details, seeProduct information 5693 827E-6.)

Ordering particularsWhen ordering, please state:

Type and catalogue number for bushing.

Catalogue number for draw rod, if standard bottom contact is chosen.

Catalogue number for SF6side terminal.

Catalogue number for shield on oil side. Shield on SF6

side must also be specified.

Catalogue number for pressure monitoring equipment.

Additional accessories or modifications.

Test required in addition to the normal routine tests.

Conductor loadingThe rated currents specified in this catalogue are basedon thermal tests and are in accordance with IEC 60137

and apply to the built-in conductors of the bushings. TheGOEK bushings conform to the requirements of IEC60137 and IEEE for currents given in Table 4.

Short-time current

The rated thermal short-time current (Ith), as defined in

IEC 60137 clause 2, is listed in Table 4 for draw rodsystem and for tight bottom contact.

Overload capacity of bushings

If the conductor for the bushing is selected with 120 %of the rated current of the transformer, the bushing isconsidered to be able to withstand overload conditionsaccording to IEC 60354 without further clarification ortests. This recommendation complies with IEC 60137.

Rated Current Short-time current Dynamic currentcurrent IEEE I

thIth

Id

IEC A 1 s 2 s peakA kA kA kA

2500 2100 100 100 250

Table 4. Rated current, short-time current and dynamic

current as defined in IEC 60137.

Extension for Catalogue number for draw rodType current transformers Type Catalogue number Number of threaded holes in the bottom contactGOEK mm bottom contact for bushing 4 6

1050 300 Standard LF 124 001-B LF 124 101-B LF 124 101-E1050 300 Tight LF 124 011-B - -1050 600 Standard LF 124 001-C LF 124 101-C LF 124 101-F1050 600 Tight LF 124 011-C - -

1425 300 Standard LF 124 002-B LF 124 102-B LF 124 102-E1425 300 Tight LF 124 012-B - -1425 600 Standard LF 124 002-C LF 124 102-C LF 124 102-F1425 600 Tight LF 124 012-C - -

1675 0 Standard LF 124 003-A LF 124 103-A LF 124 103-D1675 0 Tight LF 124 013-A - -1675 300 Standard LF 124 003-B LF 124 103-B LF 124 103-E1675 300 Tight LF 124 013-B - -1675 600 Standard LF 124 003-C LF 124 103-C LF 124 103-F1675 600 Tight LF 124 013-C - -

Table 5. Catalogue numbers.

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Recommendations for positioning

The expansion tank must be in its uppermost position. SeeFig. 12.

For further information see Testing(for SF6

side spacing)and Data for end-shields(for oil side spacing). 90

Fig. 12. Recommendations for positioning.

Nameplate with marking example.

Catalogue number for SF6

side terminal Catalogue number for shieldsMaterial Oil side SF

6side

Aluminium Copper, silver plated Epoxy insulated Pressboard insulated

LF 170 050-AA LF 170 050-AL or -AH LF 170 046-U LF 170 046-UP LF 170 046-F

LF 170 050-AA LF 170 050-AL or -AH LF 170 046-U LF 170 046-UP LF 170 046-F

LF 170 050-AA LF 170 050-AL or -AH LF 170 046-V LF 170 046-VP LF 170 046-F

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1ZSE2

750-106en,

Rev.

4,

2006-06-15

ABB Power Technologies ABComponents

Visiting address:Lyviksvgen 10Postal address:SE-771 80 Ludvika, SWEDENTel.+46 240 78 20 00Fax +46 240 121 57E-mail: sales@se.abb.com

www.abb.com/electricalcomponents