2750 515-12 en, 2016-09-30 transformerbushing,typegob ... · this section only applies to gob 1050....

2750 515-12 en, 2016-09-30

Transformer bushing, type GOBInstallation and maintenance guide

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The information contained in this document may be subject to change without prior warning and should not be consideredas binding on ABB AB’s behalf. ABB AB accepts no liability for any errors that may appear in this document. ABB AB isnot liable for any damage resulting from the incorrect interpretation of this document. This document, or parts thereof, maynot be reproduced or copied without ABB AB’s consent. It may not be distributed to others, or used by unauthorizedparties. Any breaches to the above will be penalized with the support of applicable laws.

Installation and maintenance guide2750 515-12 en, 2016-09-30

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Contents1 Safety 5

1.1 Levels of safety risks .................................................................................................................................................................... 51.2 Hazardous working situations....................................................................................................................................................... 51.3 Safety precautions........................................................................................................................................................................ 6

2 Product description 72.1 Design .......................................................................................................................................................................................... 72.2 Technical specifications ................................................................................................................................................................ 9

2.2.1 General specifications ................................................................................................................................................ 92.2.2 Mechanical loading..................................................................................................................................................... 9

3 Delivery 113.1 Transport and long term storage ................................................................................................................................................ 113.2 Lifting the bushing ...................................................................................................................................................................... 11

4 Installation 134.1 Tools ........................................................................................................................................................................................... 134.2 Consumables.............................................................................................................................................................................. 134.3 Horizontal mounting.................................................................................................................................................................... 144.4 Mounting of end-shield (only valid for GOB 1050)...................................................................................................................... 154.5 Installation using stranded cable ................................................................................................................................................ 164.6 Installation using solid rod conductor ......................................................................................................................................... 194.7 Mounting of outer terminal.......................................................................................................................................................... 244.8 Flange grounding........................................................................................................................................................................ 24

5 Commissioning 275.1 Waiting time before energizing ................................................................................................................................................... 275.2 Recommended tests before energizing...................................................................................................................................... 28

5.2.1 Overview................................................................................................................................................................... 285.2.2 Tightness test between transformer and bushing flange.......................................................................................... 285.2.3 Tightness test of bushing outer terminal................................................................................................................... 285.2.4 Measurement of capacitance and tan δ ................................................................................................................... 285.2.5 Check of through resistance..................................................................................................................................... 31

6 Maintenance 336.1 Recommended maintenance...................................................................................................................................................... 33

7 Re-packing 357.1 Dismantling................................................................................................................................................................................. 357.2 Re-packing of bushing after testing ............................................................................................................................................ 36

8 Spare parts 398.1 Summary .................................................................................................................................................................................... 39

9 Disposal and environmental information 419.1 Disposal and recycling................................................................................................................................................................ 41

4 Installation and maintenance guide2750 515-12 en, 2016-09-30


5

1 Safety

1.1 Levels of safety risks

Throughout the manual, various types of safety risks are indicated. The most serious level on this scaleprovides a warning about serious personal injury or possible death, or major damage to a product, if theinstructions are not observed.

Symbols and their meanings.

The following describes the symbols that appear in the manual, along with their meaning.

DANGER!The yellow, filled warning triangle warns that an accident will occur if the instructions are notcomplied with and that it will result in serious personal injury or death and/or major damage to theproduct.

It is used, for example, to warn of such dangers as: contact with high voltage, explosion or firerisk, risk for toxic gases, risk of crushing, impacts, falls from high places, etc.

CAUTION!The round warning symbol warns that an accident could occur if the instructions are not observed,and that this could result in personal injury and/or damage to the product.

It is also used to warn of risks that entail burns, eye or skin injuries, impaired hearing, crushing orslipping injuries, tripping, impacts, falls from high places, etc.

In addition, it is used to warn about functional requirements when assembling or removingequipment where there is a risk of damage to the product or that it might cause downtime.

NOTE!The comment symbol identifies important information and conditions. Also used to indicate anydanger that could lead to property damage.

TorqueThe torque symbol indicates the tightening torque.

1.2 Hazardous working situations

For all work on high-voltage devices, the following risks must be observed and corresponding measurestaken.

Risk Action

Working close to high voltage. Disconnect and earth around the workplace. If workmust be carried out close to live plant components,the safety distance must be in compliance with theapplicable safety regulations.

Working on ladders and platforms. Work must be executed in accordance withapplicable safety regulations. Avoid the use ofladders and platforms in poor weather conditions.


1.3 Safety precautions

Precaution Action

Transformer oil: Collect used oil in drums.

Transformer oil is slightly harmful. Fumes from unused warm oil may irritate therespiratory organs and the eyes. After long and repeated contact with transformeroil skin becomes very dry.

First aid: Skin contact: wash the hands. Use skin cream to counteract drying.

In the eyes: rinse the eyes in clean water.

Swallowing: drink water or milk. Avoid vomiting. Contact medical attendance.

SF6-gas: SF6-gas must be recycled and never released to the atmosphere.

Waste and cleaning up: Clean up liquid waste with an adsorbent. Treat waste as hazardous to theenvironment.

Fire: Fire should be extinguished by using powder, foam or carbon dioxide.


7

2 Product description

2.1 Design

The GOB is a capacitance graded oil impregnated paper bushing intended for immersed oil-air service. Theconductor consists of an aluminium tube. For bushings with a relatively small oil quantity the expansionspace at the top of the insulator is sufficient. For bushings with larger oil quantity the expansion space hasbeen increased with at top housing, or an alternative design, with an oil level glass of prisma.

The bushing can be connected to the transformer by pull-through conductors of either the flexible or solid rodtype.

For a more detailed description, see the Technical Guide, 1ZSE 2750-102.

Overview

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0277

1 Outer terminal

2 Insulator

3 Mounting flange

4 Flange extension

5 Bottom shield

6 Test tap

7 Insulator


Test tap

All bushings are equipped with a test tap connected to the outer layer of the condenser body. The test tap canbe used for measuring the bushing insulation by capacitance and dissipation factor. During operation theprotective cap must be fitted to ground the outer layer to the flange. The maximum test voltage for this testtap is 2 kV, one minute at 50 to 60 Hz. It serves as a test tap, and in connection with an external capacitance itcan be used as a voltage tap. The operating voltage is limited to 500 V.

CAUTION!The test tap should never be open during operation. It should always be connected to earth directlyvia the earthing spring or via an external impedance.

G00

0411

1 Stud

2 Earthing spring

3 Cover


9

2.2 Technical specifications

2.2.1 General specifications

Application: Transformers

Classification: Oil impregnated paper, capacitance graded, outdoor immersedbushing.

Ambient temperature: +40 °C to -40 °C, minimum value according to temperatureclass 2 of IEC 60137.

(-60 °C according to GOST 10693-81 item 2.26.)

Altitude of site: < 1000 m (Bushings for other altitudes can be provided onrequest.)

Level of rain and humidity: According to IEC 60060-1 and IEEE.

Pollution level: According to specific creepage distance and IEC 60815.

Immersion medium: Transformer oil

Maximum daily mean oil temperature: 90 °C.

Maximum temporary oil temperature, short time overload:115 °C.

Oil level in transformer: No lower than 30 mm from the bushing flange.

Max pressure of medium: 100 kPa (over pressure)

Angle of mounting: 0 to 45° angle from vertical or horizontal.

(For GOB 1050: 0 to 30° angle from vertical or horizontal.)

Test tap: Test tap with 4 mm male contact pin.

Arcing horns: Optional

Conductor: Solid or flexible draw lead conductor.

Markings: Conforming to IEC/IEEE

2.2.2 Mechanical loading

The bushings are designed for the following cantilever loads applied to the midpoint of the top end terminal,perpendicularly to the bushing axis. The bushing mounting angle can be 0 - 45° from vertical or horizontal(GOB 1050: 0 - 30° from vertical or horizontal).

In the axial direction the GOB bushing can continuously withstand 10 kN . The maximum torque on the outerterminal stud is 30 Nm .

Bushing Type test load 1 minute (N) Max. cantilever operating load(N)

GOB 250/800 2000 1800

GOB 250/1250 2500 3000

GOB 325/800 2000 1500

GOB 380/800 1800 1400

GOB 380/1250 2500 2000

GOB 450/800 1500 1150

GOB 550/800 1600 1300

GOB 550/1250 3100 2400

GOB 650/1250 3200 2600

GOB 750/1250 3200 2600

GOB 1050/1100 3200 1250


11

3 Delivery

3.1 Transport and long term storage

Keep the transportation box protected from penetrating water when stored outdoors.

For longer storage times (>6 months) it is recommended to raise the bushing to vertical position with the topend upwards or inclined position with the top end upwards and at an angle of at least 7°.

The transportation box should only be lifted with a applicable lifting gear at prescribed locations.

Carefully inspect the bushings upon receiving with regard to shipping damage. Please note that the bushingshave been routine tested in oil and some oil may remain on the oil side of the bushing.

The bushings are normally delivered from ABB in boxes with the bushing supported by blocks andfiberboard. The boxes are marked with “Top End”.

Long term storage

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0294

3.2 Lifting the bushing

Light bushings may be handled manually. Lift heavier bushings with the aid of a lifting tool. The weight ofthe bushing is stated on the rating plate.

Lift the bushing to the vertical position and at an angle according to the figures. Use a soft bedding under thebottom end of the bushing, e.g. a rubber mat.

NOTE!Transformer bushings should be stored in transport boxes until immediately before assembly.

NOTE!Remove the transport securing device before lifting.


Lifting from the box

CAUTION!For lifting the bushing from the box, secure two clean lifting slings as shown. Support the bushingat the same points as in the box if placed on the ground or block it under the flange and the metaltop piece. Light bushings may be handled manually.

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0278

Lifting the bushing

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0279

1 Soft bedding, e.g. rubber mat or wood board

2 Lifting eye


13

4 Installation

4.1 Tools

Tool Part number Note

Lifting gear - -

Soft bedding - E.g. rubber mat or wood board

Soft slings - -

Lifting eye bolt M12 (DIN 580) 2183 2001-3 For mounting at an angle.

Pull-through cord with M8 swivel. 9760 669-A -

Torque wrench key for hex bolts,16 mm (M10) and 13 mm (M8),torque 20 to 40 Nm.

- -

Wrench for hex bolt 30 mm oradjustable wrench for 30 mm boltsor larger.

- For test tap cover.

Open wrench, 55 or 66 mm. - For tightening outer terminal.

Tackle - For mounting the bushing at aspecific angle.

4.2 Consumables

Brand Type / Name Note

- Oil based vaseline Not harmful to the transformer oil,to lubricate bolts that come intocontact with the transformer oil.

MOBIL Mobil grease 28 For bolts that come in contact withthe transformer oil. Not harmful tothe transformer oil, to lubricate andprotect the ground bolt and theouter terminal O-ring gasket.


4.3 Horizontal mounting

Overview

If a bushing intended to be mounted in the horizontal position, then this must be clearly stated in the order.The bushing flange is then supplied with an oil hole at the oil side of the flange, for connection of the bushingoil system to the transformer oil. As horizontally mounted bushings must be completely oil filled and thishole will provide the necessary oil expansion for the bushing. The bushing will use the transformer expansionvessel.

At delivery the hole is covered by a covering plate with gasket as shown in the figure. This arrangementmakes sure that the hole is opened before mounting of the bushing.

NOTE!It is important to check that the gasket on the transformer flange does not cover this hole inservice.

G00

0280

1 Covering plate with gasket

2 Flange

Filling transformer using vacuum

Remove covering plate with gasket from the oil hole in the flange. Mount the bushing with the hole upwards.The bushing will be completely oil filled at the filling of the transformer.

Filling transformer without using vacuum

Place the bushing vertically and open one of the filling plugs at the top. Add clean and dry transformer oiluntil the bushing is completely filled. Put back and tighten the plug and place the bushing horizontally withthe opening in the flange upwards. Remove the covering plate with gasket and mount the bushing in thetransformer immediately without turning or tilting it.


15

4.4 Mounting of end-shield (only valid for GOB 1050)

Overview

This section only applies to GOB 1050.

The end-shield is packed in a plywood box with the fastening bolts and the washers included. The end-shieldis mounted on the bottom end of the bushing according to the following procedure.

Procedure

1. Mount the end-shield (1) with bolts and washers(2).

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0287

2. Tighten the bolts (2).

CAUTION!If the bushing is lowered in transformeroil, the air cushion in the end-shieldmust be vented by a hose.

Torque10 Nm

End of instruction


4.5 Installation using stranded cable

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0281

1 O-ring (1100-1250A / 59.2x3 / 1ZSC004442-CAJ)

2 O-ring (800A / 39.2x3 / 1ZSC004442-CAE)

3 Locking pin (800A / 2111 764-A)

4 Locking pin (1100-1250A / 2111 764-B)

5 Outer terminal

6 Bushing

7 Inner terminal

Procedure

1. Braze or crimp the winding cable/cables from the transformer to the inner terminal (7).

2. Carefully clean and inspect the oil end of the bushing and the inside of the center hole.


17

3. Drop the pull-through cord (10) through thebushing center hole.

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0282

4. Fasten the M8 swivel with the pull-through cord(10) to the inner terminal (7).

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0203

5. Lower the bushing into the transformer whileguiding the stranded cable by keeping thepull-through cord (10) taut.

NOTE!If there are inspection openings nearthe bushings on the transformer, theymust be open while mounting thebushing, in order to ensure that thelead is entering the bushing in thecorrect manner.

CAUTION!If fixed stud bolts are used for fasteningthe bushing flange, it is advisable toapply plastic sleeves on two or three ofthe studs both to guide the flange andto prevent chipping of the stud bolts,with the subsequent risk of chips,falling into the transformer.

G00

0283

6. Fasten the bushing to the transformer flange.

NOTE!Cross-tighten the bolts.

TorqueM12 50 ±5 Nm

1/2” UNC 55 ±5 Nm


7. Secure the inner terminal (7) by insert the lockingpin (3 or 4).

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0288

8. Gently release the pull-through cord (10) so the inner terminal (7) rests on the locking pin (3 or 4).

9. Remove the pull-through cord.

10. Proceed immediately to Mounting of outer terminal, page 24.

End of instruction


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4.6 Installation using solid rod conductor

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0284

1 O-ring (1100-1250A / 59.2x3 / 1ZSC004442-CAJ)

2 O-ring (800A / 39.2x3 / 1ZSC004442-CAE)

3 Locking pin (800A / 2111 764-A)

4 Locking pin (1100-1250A / 2111 764-B)

5 Outer terminal

6 Bushing

7 Solid rod (upper part)


Procedure for 1100-1250 A

1. Braze or crimp the winding cable/cables from thetransformer to the lower part of the solid rodconductor (12).

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0209


3. Lift the bushing above the opening on the transformer.


G00

0282

5. Fasten the M8 swivel with the pull-through cord(10) to the solid rod (7).

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0203

6. Partly pull up the upper part (7) of the solid rod into the center hole.


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7. Clean and grease the contact surfaces betweenthe lower (12) and the upper (7) part of the solidrod.

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0209

8. Lubricate the bolts (11) with Mobilgrease 28 andattach the upper part (7) to the lowerpart (12) ofthe solid rod.

NOTE!Or use a similar lubricant, not harmfulto the transformer oil.

Torque35-40 Nm

9. Lower the bushing into the transformer while guiding the solid rod by keeping the pull-through cord(10) taut.

CAUTION!If fixed stud bolts are used for fastening the bushing flange, it is advisable to apply plasticsleeves on two or three of the studs both to guide the flange and to prevent chipping of thestud bolts, with the subsequent risk of chips, falling into the transformer.



TorqueM12 50 ±5 Nm

1/2” UNC 55 ±5 Nm

11. Insert the locking pin (3 or 4) to secure the solidrod (7).

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0288

12. Gently release the pull-through cord (10) so the solid rod (7) rests on the locking pin (3 or 4).


14. Proceed to Mounting of outer terminal, page 24.

End of instruction


Procedure for 800 A

1. Braze or crimp the winding cable/cables from thetransformer to the lower part of the solid rodconductor (12).

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0290


3. Lift the bushing above the opening on the transformer.


G00

0282

5. Fasten the M8 swivel with the pull-through cord(10) to the solid rod (7).

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0203

6. Partly pull up the upper part (7) of the solid rod into the center hole.


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7. Lubricate the screw (14) with Mobilgrease 28 andthread the upper part (7) of the solid rod to thelower part of the draw rod (12).


G00

0290

13. Locking pin (2111 764-C)

14. Screw (2122 751-2)

15. Insets for 17 mm wrench

8. Tighten the insets (15) with a 17 mm wrench. Torque35-40 Nm

9. Lower the bushing into the transformer while guiding the solid rod by keeping the pull-through cord(10) taut.

CAUTION!If fixed stud bolts are used for fastening the bushing flange, it is advisable to apply plasticsleeves on two or three of the studs both to guide the flange and to prevent chipping of thestud bolts, with the subsequent risk of chips, falling into the transformer.



TorqueM12 50 ±5 Nm

1/2” UNC 55 ±5 Nm

11. Secure the solid rod (7) by insert the locking pin(3 or 4).

CAUTION!Turn clockwise to align the holes forthe locking pin.

G00

0288

12. Gently release the pull-through cord (10) so the solid rod (7) rests on the locking pin (3 or 4).


14. Proceed to Mounting of outer terminal, page 24.

End of instruction


4.7 Mounting of outer terminal

1. Carefully clean the contact and gasket surfaces.

Lubricate the O-ring (8) with Mobilgrease 28.


G00

0285

2. Grease the thread for the terminal stud (5) with vaseline.

NOTE!Or use a similar lubricant, not harmful to the transformer oil.

3. Fit the the O-ring (8) and the outer terminal stud(5) in place.

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0286

4. Tighten the outer terminal stud.

Width across flats

800 A: 55 mm

1100/1250 A: 66 mm

Torque60-80 Nm

5. Carefully wire-brush and grease the outer aluminium terminals, use a contact compound or vaseline.

NOTE!It is important to remove oxide from the aluminium terminals before connecting the contactclamps.

End of instruction

4.8 Flange grounding

Overview

The bushing flange has a tapped hole (M12). After tightening the bolts that secure the bushing to thetransformer tank, the flange should be grounded. This prevents electrical discharges between the bushingflange and transformer tank under normal service conditions.

There are two alternatives.


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Alternative 1, using pointed set bolt

1. Apply a large quantity of grease to the pointed setbolt (13), use Mobilgrease 28.

NOTE!Or use a similar lubricant.

G00

0292

13. M12 stainless steel A4-80 recommended

2. Screw in the pointed set bolt (13) and tighten. Thetip of the bolt penetrates the paint.

This makes an electrical connection between thebushing and the transformer tank, keeping themat the same voltage.

Torque40 Nm

End of instruction

Alternative 2, using flexible cable

1. Run a flexible cable (14) between the M12grounding hole in the bushing flange and acorresponding connection point in the transformer.

G00

0291

13. M12 stainless steel A4-80 recommended

2. Apply a large quantity of grease to the bolt (13), use Mobilgrease 28.

NOTE!Or use a similar lubricant.

3. Screw in the bolt (13) and tighten. Torque40 Nm

4. Connect the other end of the cable (14) to the transformer.

This makes an electrical connection between the bushing and the transformer tank, keeping them atthe same voltage.

End of instruction


27

5 Commissioning

5.1 Waiting time before energizing

CAUTION!When a bushing has been stored horizontally, it must be raised with the top up for at least 12 hoursbefore service voltage is applied and 24 hours before test voltage is applied. If, by mistake, thebushing has been stored horizontally more than one year, it must be placed in the vertical positionfor at least one week before energizing. Some waiting time may be necessary before energizing inorder to avoid flashovers or partial discharges due to airbubbles at the bushing surface.

Vacuum filled transformer

No waiting time is necessary regarding the bushing.

De-gassed oil-filled transformer

During mounting, use a clean and dry paintbrush to release surface bubbles. Wait 6 hours before energizing.

Gas-saturated oil-filled transformer

During mounting, use a clean and dry paintbrush to release surface bubbles. Wait 24 hours before energizing.

De-gassed oil filled transformer with reduced oil-level

After restoring the oil-level, wait 24 hours before energizing. For all alternatives except vacuum-filledtransformers, the oil should be allowed to enter the center tube to at least flange height by releasing the outerterminal sealing system and allowing air to escape.

NOTE!A certain amount of waiting time may be necessary before energizing to avoid flashovers orpartial discharges due to air bubbles on the bushing surface. Choose a suitable procedure.


5.2 Recommended tests before energizing

5.2.1 Overview

The following tests should be performed to check the insulation, sealing and current path of the bushing.

NOTE!The tests should be performed after installation, but before connecting the outer terminal of thebushing to the rest of the switchyard power circuit.

5.2.2 Tightness test between transformer and bushing flange

Several different methods may be used and we thus refer to instructions provided by the company responsiblefor field erection. As a simple example, the tightness of the seal between a transformer and bushing flangecan be checked when the transformer is oil-filled by using chalk or, perhaps easier, with paper strips.

5.2.3 Tightness test of bushing outer terminal

Since the top terminal is often situated above the oil level of the transformer expansion system, a leak at thispoint is extremely serious, because water could enter directly into the transformer insulation. It is thusrecommended to conduct a tightness test after installation, preferably both with a vacuum and over-pressure.Several different methods may be used and we refer to instructions provided by the firm responsible for fielderection.

One possible method is the tracer gas method:

1. Put a tracer gas into the center tube before mounting the outer terminal. The oil level of the transformermust be above the bottom end of the bushing but below the bushing flange.

2. Increase the pressure in the center tube by increasing the oil level as much as possible.3. Search for leaking gas at the gasket with a gas detector (sniffer).

5.2.4 Measurement of capacitance and tan δ

After mounting, a capacitance measurement is recommended. Connect a measuring bridge between the outerterminal and the test tap/voltage tap. Or use ABB’s test tap adapter (2769 522-C). This can be done withoutremoving the bushing as the bushing has an insulated test tap. More details can be found in productinformation 2750 515-142, “Bushing diagnostics and conditioning”.

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0356

1 Test tap

2 Cover (2749 528-B) with O-ring (1ZSC001606-AAW)


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With the transformer de-energized and the bushing outer terminal disconnected, the test tap cover is removed.The measuring equipment is connected to the test tap and the measuring voltage source to the bushingterminal.

The capacitances C1 between the outer terminal and the test tap, and the capacitance C2 , between the test tapand the flange are marked on the rating plate. The nominal capacitances C1 of the different bushing types arelisted in the table. C2 is highly dependent on the surrounding parts inside the transformer and it is notpossible to provide a nominal value valid for all service conditions.

CAUTION!The test tap is not self grounding.

Since C2 is usually relatively small, the test tap must never be open-circuited when applying avoltage to the bushing. It must always be grounded or connected to an external impedance. Noconnection may destroy the bushing.

NOTE!When not measuring, always make sure that the cover is properly tightened with the O-ring inplace. This is to prevent dust and water from entering the test tap.

NOTE!The transport container must be removed before measuring capacitance and tan δ.


Bushing Catalogue No

LF 123 ...

Nominal capacitance (pF)

C1 (C2)

GOB 250 013, 014, 171, 172

015, 016, 173, 174

017, 167

019, 168

083, 084, 175, 176

085, 169

125

205

165

270

275

375

90

500

110

750

800

1200

GOB 325 025, 026, 177, 178

027, 028, 179, 180

089, 090, 181, 182

135

200

260

95

200

425

GOB 380 037, 038, 183, 184

039, 040, 185, 186

041, 101

043, 102

095, 096, 187, 188

097, 103

145

200

185

265

245

320

110

335

150

550

550

1150

GOB 450 049, 050, 145, 146

051, 052, 147, 148

053, 054, 149, 150

145

200

245

125

570

770

GOB 550 061, 189, 062

063, 190, 064

107, 191, 108

065, 142

067, 143

109, 144

150

170

210

170

195

240

156

400

750

150

320

575

GOB 650 073,192

075, 193

113, 194

205

235

280

200

340

550

GOB 750 077, 104

078, 105

079, 106

205

235

275

390

565

950

GOB 1050 281

280

310

367

450

700


31

Test tap adapter

An adapter (1ZSC003881-AAC) is available for permanent connection to measuring circuits.

G00

0299

5.2.5 Check of through resistance

The through resistance measurement method depends on the design of the transformer. In general, a current isapplied from bushing to bushing. The voltage drop from outer terminal to outer terminal is measured. Theresistance is calculated with Ohm’s law, U = R*I. (U: Measured voltage drop. I: Through current. R: Totalcircuit resistance).

The total through resistance is the sum of the transformer winding and lead resistance and the bushingconductor and contact resistance. The additional resistance from the bushing conductor should not be morethan 10 ... 100 mΩ. Since the through resistance of the HV winding of a typical power transformer is in theorder of 0.1 ... 1 Ω, this is a very rough method that can only be used to detect very large faults in the currentpath, such as open circuits.

Less-than-perfect contacts can only be detected by making a sensitive measurement across each connectionpoint, or by measuring the temperature increase during operation with an infrared sensitive camera(thermovision).


33

6 Maintenance

6.1 Recommended maintenance

The bushings are in principle maintenance free; no regular maintenance is needed.

DANGER!No work at all may be performed on the bushing while it is energized or ungrounded.

NOTE!For bushings with oil level glas, it is recommended to check oil level at plant supervision.

Cleaning of insulator surface

Under conditions of extreme pollution it may be necessary to clean the insulator surface. This should be doneby wiping with a moist cloth. If necessary, ethyl-alcohol or ethyl-acetate may be used.

NOTE!1,1,1 -Trichloroethane or Methylchloride are not recommended due to their possibly harmful andenvironmentally detrimental properties.

Measurement of capacitance and tan δ

Please refer to Measurement of capacitance and tan δ, page 28.

Thermovision (infrared camera) check for local overheating on connectors

At maximum rated current, the bushing outer terminal normally handles a temperature of about 35 to 45 °Cabove the ambient air. Significantly higher temperatures, especially at lower current loading, can be a sign ofbad connections.

Tightness check

Make a visual inspection for oil leakage during normal station supervision.

Checking of oil level and oil sampling

CAUTION!Oil sampling and dissolved gas in oil analysis.

Normally we do not recommend taking oil samples or opening our bushings. The bushing issealed and tightness tested at the time of manufacturing. An oil sampling means that the bushinghas to be opened. Thus, there is also a risk of improper sealing after the sampling is finished.However, when a problem is known, for example high power factor over C1 or visible leakage,there might be a need for oil sampling and gas analysis or oil level check. In this case, ask forproduct information 2750 515-142 "Bushing diagnostics and conditioning".


35

7 Re-packing

7.1 Dismantling

For bushings mounted vertically no special precautions are needed after removal, because the bushings aresealed. Storing a bushing completely oil filled without expansion space could result in a high internalpressure. For bushings mounted horizontally, follow the procedure.

Procedure

1. Remove the bushing from the transformer.

2. Drain a small amount of oil.

3. Tighten the bolt in the flange (2) with the coverplate (1).

G00

0293

4. Raise the bushing vertically.

5. Unscrew the plug (4).

G00

0289

6. Check the oil level through the oil filling hole (4) at the top with a dry and clean dipstick.


7. If necessary, adjust the oil level according to thetable (from top of the flange at 20 ±10 °C).

Type Withouttophousing

Withtophousing

GOB 250-450 110 ±8 mm 165 ±8 mm

GOB 550 170 ±10 mm 270 ±15 mm

GOB 650 175 ±10 mm 275 ±15 mm

GOB 750 275 ±15 mm 330 ±15 mm

Bushings with one oil level sight glass has thecorrect oil level in the middle of the glass. GOB750 and 1050 has two sight glasses and the oillevel plug is between the two glasses.

8. Scrw in and tighten the plug (4). Torque20 Nm

End of instruction

7.2 Re-packing of bushing after testing

G00

0278

CAUTION!For lifting the bushing to the box, apply two clean lifting slings as shown. Support the bushing atthe same points as in the box if placed on the ground or block it under the flange and the metal toppiece. Light bushings may be handled manually.

NOTE!The bushing and transformer must be marked for final erection at the same position.

NOTE!During transport the inner terminal/oil side parts of the draw rod may be fastened to the transportcover in transformer. Upon erection, the transport cover is removed, and the terminal/draw rodloosened.


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NOTE!Please note the position of the lifting sling! For polymeric insulators, the lifting sling should beplaced as close as possible to the flange and not on the rubber surface.

NOTE!The transformer bushing(s) should be re-packed in the transport box as per delivered. The bushingshould be fixed in axial and radial direction, and secured against rotation.

At the ABB factory, the bushing box is closed with bolts and plastic straps. It is advisable to usebolts and plastic straps when reclosing the box after transformer testing.


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8 Spare parts

8.1 Summary

In the event of major damage to the bushing we recommend that it be returned to ABB for possible repair andre-testing. Certain parts that may be damaged or lost during transport or installation, can be ordered fromABB.


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9 Disposal and environmental information

9.1 Disposal and recycling

ABB strives to minimize the product’s impact on the environment throughout its entire life cycle. Technicaland product development focuses on environmental aspects. The ecocycle approach is strived for andconsideration is taken to the materials’ environmental impact and recycling alternatives. The manufacturingprocesses are selected to be as safe for the environment as possible.

Disposing of worn-out equipment

Worn-out equipment must be phased out in an environmentally sound manner.

When disposing of used equipment, much of the material, or energy content in the material, can be recycledfollowing sorting and cleaning. The amount that is recycled varies depending on the technical resources andexperience in each country. Non-recyclable components should be sent to an approved environmental wastetreatment plant for destruction or disposal.

Porcelain

After cleaning, the porcelain can be sent for disposal or used for other purposes, such as for use as fillingmaterial.

Electronics

Electronics equipment should be sent to an approved recycling company or sorted into different componentmaterials for appropriate treatment.

Metals

Metals should be sorted according to type and surface coating and sent to an approved recycling company.Following the removal of any paint or other surface coating, clean metal can usually be melted down andused in new products. Many metal components of iron, steel and aluminum are large and easy to identify, e.g.support structures. ABB strives to reduce the use of precious metals and the release of environmentallyhazardous metals.

Recycling of these is particularly important. Precious metals such as copper and silver are expensive and areonly present in small amounts in the Earth’s crust. Copper is primarily used in current paths, puffers, contactsand cables. Silver plating of contacts may occur. Emissions from certain metals may cause damage. Thisapplies to copper, but also zinc and nickel, which are used sparingly as surface coatings.

Plastics

The different types of plastic should be separated and sent to an approved environmental waste treatmentplant or recycling company. The energy content in thermoplastics and thermosetting plastics can often berecovered through combustion at a plant designed for the purpose. Thermoplastics can usually be melteddown and reused without any major loss of quality. Composites can be fractioned and used as fillingmaterials in other materials or be disposed of.


Oils and greases

Before disposal, oil, grease and similar products must be removed and sent to an approved environmentalwaste treatment plant or recycling company. By utilizing gravimetric forces, oil waste can be separated intooil, water and a range of contaminants. In many cases, the oil can then be reused. Alternatively, the energycontent in oil can be recovered through combustion at a plant designed for the purpose.

Rubber

Rubber can be sent to an approved environmental waste treatment plant, either for disposal or reuse forvarious purposes.

Rubber is present in various seals.

Other materials

Other materials are sorted and sent to an approved environmental waste treatment plant.

Contact Us

ABB ABComponentsSE-771 80 Ludvika, SwedenPhone: +46 240 78 20 00Fax: +46 240 121 57

www.abb.com/electricalcomponents

2750 515-12 en, 2016-09-30 transformerbushing,typegob ... · this section only applies to gob 1050....

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