ABB VUBB User manual

1ZSC000562-AAL EN, REV. B, 2020-03-18

Vacuum on-load tap-changers, type VUBB

User guide

The information contained in this document may be subject to change without prior warning and should not be considered

as binding on ABB AB’s behalf. ABB AB accepts no liability for any errors that may appear in this document. ABB AB is

not liable for any damage resulting from the incorrect interpretation of this document. This document, or parts thereof, may

not be reproduced or copied without ABB AB’s consent. It may not be distributed to others, or used by unauthorized

parties. Any breaches to the above will be penalized with the support of applicable laws.

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Contents

1 Safety 5

1.1 Levels of safety risks ................................................................................................................................................................... 5

1.2 Hazardous working situations ..................................................................................................................................................... 6

1.3 Safety precautions....................................................................................................................................................................... 6

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2 Introduction 7

2.1 Overview of maintenance............................................................................................................................................................ 7

2.2 Maintenance by ABB................................................................................................................................................................... 7

2.3 Replacement at end of life........................................................................................................................................................... 8

2.4 Maintenance schedule ................................................................................................................................................................ 8

2.5 Design ......................................................................................................................................................................................... 9

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3 Preparations 13

3.1 Planning ...................................................................................................................................................................................... 13

3.2 Required tools ............................................................................................................................................................................. 13

3.3 Consumables .............................................................................................................................................................................. 13

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4 Inspection 15

4.1 Inspection of the oil-level in the oil conservator........................................................................................................................... 15

4.2 Inspection of the breather............................................................................................................................................................ 15

4.3 Inspection of the motor-drive mechanism ................................................................................................................................... 16

4.4 Inspection of the shaft system..................................................................................................................................................... 16

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5 Analysis 19

5.1 Oil filtration or replacement of oil................................................................................................................................................. 19

5.2 Testing of oil quality, and dissolved gas analysis (DGA) .............................................................................................................19

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6 Oil-filling 23

6.1 Preparations ................................................................................................................................................................................ 23

6.2 Oil-filling with the atmospheric process ....................................................................................................................................... 24

6.3 Oil-filling with the vacuum process .............................................................................................................................................. 27

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7 Electrical connection and testing 31

7.1 Testing of the electrical connections............................................................................................................................................ 31

7.1.1 Testing of motor-drive unit BUE2............................................................................................................................... 31

7.1.2 Testing of motor-drive unit BUL2 ............................................................................................................................... 34

7.2 Testing of the protection devices ................................................................................................................................................. 36

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8 Troubleshooting 37

8.1 Troubleshooting........................................................................................................................................................................... 37

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9 Electrical diagrams 39

9.1 Overview ..................................................................................................................................................................................... 39

9.2 Standard circuit diagram BUE ..................................................................................................................................................... 39

9.3 Standard circuit diagram BUL2 ................................................................................................................................................... 40

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10 Spare parts and special tools 41

10.1 Summary ..................................................................................................................................................................................... 41

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11 Disposal and environmental information 43

11.1 Overview ..................................................................................................................................................................................... 43

11.2 Specification of materials ............................................................................................................................................................ 43

11.3 Disposal and recycling ................................................................................................................................................................ 44

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12 References 47

12.1 Summary ..................................................................................................................................................................................... 47

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1 Safety

1.1 Levels of safety risks

Throughout the manual, various types of safety risks are indicated. The most serious level on this scale

provides a warning about serious personal injury or possible death, or major damage to a product, if the

instructions 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 not

complied with and that it will result in serious personal injury or death and/or major damage to the

product.

It is used, for example, to warn of such dangers as: contact with high voltage, explosion or fire

risk, 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 or

slipping injuries, tripping, impacts, falls from high places, etc.

In addition, it is used to warn of functional requirements when assembling or removing equipment

where there is a risk of damage to the product or downtime.

NOTE!

The comment symbol identifies important information and conditions. Also used to indicate any

danger that could lead to property damage.

Torque

The torque symbol indicates tightening torque.

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1.2 Hazardous working situations

Hazard Action

Working close to high voltage. Disconnect all plant power. Ground all objects at the workplace.

If work must be done close to live plant components, make sure that

the safety distance is in compliance with the applicable safety

regulations.

Working on ladders and platforms. Work must be done in accordance with the applicable safety

regulations.

Do not use ladders or platforms in poor weather conditions.

Working with heavy objects. Do not walk under lifted objects.

Make sure that heavy objects are stable before starting work.

1.3 Safety precautions

Precaution Action

Transformer oil Collect used transformer oil in drums.

Transformer oil is dangerous. Fumes from hot oil can cause irritation

to the respiratory organs and the eyes. Long and repeated contact

with transformer oil can cause damage to your skin.

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

to the environment.

Fire Extinguish fires with powder, foam or carbon dioxide.

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2 Introduction

2.1 Overview of maintenance

General

The ABB range of on-load tap-changers are developed for maximum reliability and a minimum of

maintenance is required.

The tap-changer is made for a service life equal to that of the transformer.

The tap-changer oil is separated from the oil in the transformer oil, this prevents contamination of the the oil

in the transformer. Because the oil deteriorates, and loses its dielectric strength, when it quenches the oil at

the switching operations, the oil has to be changed at regular intervals. This is also important because the oil

looses its lubricating properties as it becomes contaminated.

Maintenance intervals

The wear on the contacts (determined by the number of operations), and the hours in service determines

when the tap-changer needs maintenance.

The number of operations by the tap-changer is recorded by a counter in the cabinet of the motor-drive

mechanism.

Maintenance generally takes at least 8 hours, this includes a 3 hour waiting period after oil-filling.

About replacement of the tap-changer

The contacts will withstand a very large number of switching operations. For common power transformers

the number of switching operations is approximately 20 per day, thus it is usually not necessary to replace the

contacts during the life of the transformer.

2.2 Maintenance by ABB

For maintenance, please contact ABB or make sure that personnel performing maintenance are trained and

certified by ABB.

Maintenance of the tap-changer should be performed regularly at intervals of 300000 operations; refer to the

table below. The relevant information is stated on the rating plate. This permits confirmation of mechanical

integrity and monitoring of contact wear, and the necessary preparations can be made for replacing the

vacuum interrupters.

Number of operations Main activity

300000 Maintenance (sequence measurement via inspection

hole on cover).

600000 Replacement of switching mechanism (including

vacuum interrupters).

900000 Maintenance (sequence measurement via inspection

hole on cover).

1200000 End of life.

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2.3 Replacement at end of life

The vacuum interrupters are sensitive and the settings must be exact. It is thus important that replacement is

performed by an ABB-certified technician. Contact ABB or make sure that personnel performing

replacement of the complete switching mechanism including vacuum interrupters are trained and certified

by ABB.

The estimated contact life of the vacuum interrupters in the selector switch at rated load is stated on the rating

plate of the tap-changer. Refer to the table in Maintenance by ABB, page 7.

2.4 Maintenance schedule

Maintenance schedule

Action Inspection Analysis Maintenance End of life

Yearly At 2, 6, 11

and 15

years

300000

operations

600000

operations

900000

operations

1200000

operations

Inspection of the oil-level

in the oil conservator,

page 15

X - X X X -

Inspection of the

breather, page 15

X - X X X -

Inspection of the

motor-drive mechanism,

page 16

X - X X X -

Inspection of the shaft

system, page 16

- - X X X -

Testing of oil quality, and

dissolved gas analysis

(DGA), page 19

- X X X X -

Oil filtration or

replacement of oil,

page 19

- X X X X -

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2.5 Design

Overview

The VUBB on-load tap-changer is of the in-tank design. The motor-drive mechanism is attached to the side

of the transformer tank, and connected to the tap-changer by drive shafts and a bevel gear.



G004252

1. Vertical driveshaft

2. Bevel gear

3. Horizontal driveshaft

4. Tap-changer

5. Transformer tank

6. Motor-drive mechanism

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Exterior details of the tap-changer

G006219

1. Pressure relay

2. Bevel gear

3. Position indicator window on inspection cover

4. Valve

5. Bottom flange with valve

6. Selector switch

7. Terminals

8. Terminals

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Details of the selector-switch

G006222

1. Terminal

2. Fixed contact

3. Main auxillary contact

4. Vacuum interrupter

5. Transition resistor

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3 Preparations

3.1 Planning

To shorten the down-time when doing maintenance, it is important to plan the work so that waiting time is

minimized. Thus, when the tap-changer is oil-filled with the atmospheric process, work should be completed

on the tap-changer before work is started on the motor-drive. So that the waiting time requirement is satisfied

as soon as possible.

Oil-filling process Minimum required waiting time

Atmospheric 3 hours

Vacuum Waiting time not necessary

The atmospheric oil-filling process

Some waiting time is necessary after the tap-changer has been oil-filled, before it is energized. The reason for

this is that air bubbles stick to the surfaces inside the tap-changer when it is filled with oil, and flashovers and

partial discharges can form in the bubbles. Thus, it is important to let the necessary waiting time pass, to

make sure that all the air bubbles have risen to the surface of the oil before the tap-changer is energized.

3.2 Required tools

Tool Article number Note

Standard set of open-end

wrenches

- 9/16" is used.

Standard set hex-keys - 3/8" is used.

Ratchet wrench handle with

extension

- -

Oil sampling container - -

Test equipment - IEC 60156, IEC 60475

Protective gloves - Oil-resistant

3.3 Consumables

Item Brand Part number Note

Transformer oil - - Volume approximately 270 liter.

• Complies with

IEC 60296-LCSET.

• Electrical withstand

requirement

>40 kV@ 2.5 mm gap,

according to IEC 60156.

Lubrication oil - - For bearings.

GULF-718 EP Gulf - For ball-bearings.

Aero Shell Grease 22 Shell - For shaft system.

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About transformer oil

Used transformer oil can be used again in the tap-changer, if the water content is ≤15 ppm, and it has been

stored according to IEC 60422 point 10.

A small volume of new transformer oil should be kept available to replace waste oil, and for cleaning.

Approximately 40 liter is sufficient.

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4 Inspection

4.1 Inspection of the oil-level in the oil conservator

Overview

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 year

300000

operations

600000

operations

900000

operations

1200000

operations

X - X X X -

Maintenance schedule, page 8.

Procedure

1. Inspect the oil-level in the oil conservator, refer to the instructions form the supplier of the oil

conservator.

CAUTION!

The oil may be hot.

End of instruction

4.2 Inspection of the breather

Overview

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 year

300000

operations

600000

operations

900000

operations

1200000

operations

X - X X X -

Maintenance schedule, page 8.

Procedure

1. Inspect the breather, refer to the documentation from the transformer manufacturer.

DANGER!

Risk of explosion!

The breather and the piping from the transformer contains explosive gases.

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2. Inspect the drying agent.

1. If the top of the drying agent has changed color, inspect the breather and couplings for leakage.

If there is a leakage, locate it and seal it.

2. If more than half of the draying agent has changed color, then replace it.

The drying agent can also be dried.

End of instruction

4.3 Inspection of the motor-drive mechanism

Overview

The inspection consists of a visual check of the motor-drive mechanism and reading of the counter's value to

determine when maintenance is due.

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 year

300000

operations

600000

operations

900000

operations

1200000

operations

X - X X X -

Maintenance schedule, page 8.

Procedure

1. Inspect the counter and record the number of operations.

2.

Inspect the heater, refer to the transformer manufacturers documentation.

3.

Inspect the condition of the drive-belt on the motor-drive.

End of instruction

4.4 Inspection of the shaft system

Overview

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 year

300000

operations

600000

operations

900000

operations

1200000

operations

- - X X X -

Maintenance schedule, page 8.

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Procedure

1. Loosen the hose clamps (6), and move back the

protective tubes (8).

G006231

2.

Make sure that the axial play is less than 2 mm.

If the axial play is more than 2 mm:

1. Loosen the hex screws (2).

2. Move the coupling halves outwards (9).

3. Tighten the hex screws (2).

G006232

3.

Apply Aero Shell grease 22 to the couplings (12).

G006354

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4. Move the protective tubes (8) apart, and tighten

the hose clamps (6).

G006231

5.

Remove the four bolts (13), and remove the lid

(14).

G006356

6.

Apply Aero Shell grease 22 to the gears.

G006355

7.

Install the lid (14).

Torque

24 Nm

End of instruction

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5 Analysis

5.1 Oil filtration or replacement of oil

Overview

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 years

300000

operations

600000

operations

900000

operations

1200000

operations

- X X X X -

Maintenance schedule, page 8.

Procedure

1. Put the oil through the filtering equipment until the particle content is satisfactory. Refer to

IEC 60422:2005.

2.

Do the oil break-down test, refer to IEC 60156-7:1995.

NOTE!

The break down value for the oil has to be more than 40 kV @ a 2.5 mm gap.

3.

If the oil failed the break down test, replace the oil.

End of instruction

5.2 Testing of oil quality, and dissolved gas analysis (DGA)

Overview

The purpose of this test is to determine if the oil can be used again, or has to be replaced.

Maintenance interval End of life

Yearly After 2,6,11,15

and then every

3 years

300000

operations

600000

operations

900000

operations

1200000

operations

- X X X X -

Maintenance schedule, page 8

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Procedure

1. Connect the oil hose (5) to the oil valve (3). Refer

to the dimension drawings of the tap-changer for

the threads of the oil valve (3).

DANGER!

Make sure that hoses and equipment is

correctly grounded. Unsatisfactorily

grounded equipment can cause

explosive gases to ignite.

Explosive gases are generated during

normal operation of the transformer.

G004527

2.

If the tap-changer shares oil conservator with the

transformer, close the oil valve (2) on the pipe

from the oil conservator.

G006234

3.

Open the oil valve and drain a small quantity of oil into a container, and dispose of it in accordance

with local environmental regulations.

DANGER!

Hot oil. The oil can be 90°C

NOTE!

Be prepared to close the oil valve when enough oil has been removed.

4.

Drain the necessary quantity of oil for the oil quality test.

5.

Do the oil quality test, refer to IEC 60422, 2005-10.

NOTE!

Document the test results.

NOTE!

Some maintenance may be necessary based on the test results.

6.

Drain a sample of oil for the dissolved gas analysis (DGA), and send the sample to the laboratory.

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ABB VUBB User manual

ABB VUBB User manual

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