ABB VUBB User manual

Vacuum on-load tap-changers, type VUBB
User’s guide
1ZSC000562-AAL en

Original instruction
The information provided in this document is general by intention and does not
cover all possible applications. Any specific application not covered should be
referred directly to ABB or its authorized representative.
ABB makes no warranty or representation and assumes no liability for the
accuracy of the information in this document or for the use of such information. All
information in this document is subject to change without notice.
This document must not be copied without our written permission, and the contents
thereof must not be imparted to a third party nor be used for any unauthorized
purpose. Contravention will be prosecuted.

Content
1. Safety............................................................................................................................... 5
1.1 General..................................................................................................................... 5
1.2 Safety warnings ........................................................................................................ 5
1.3 Safety precautions .................................................................................................... 5
1.3.1 Personal safety................................................................................................... 5
1.3.2 Environmental safety........................................................................................... 5
1.3.3 First aid .............................................................................................................. 5
1.3.4 In the event of re............................................................................................... 5
2. Introduction ...................................................................................................................... 6
2.1 General..................................................................................................................... 6
2.2 Functional description ............................................................................................... 6
2.2.1 Switching sequence, operation with resistor side rst ......................................... 7
2.2.2 Switching sequence, operation with main contact rst........................................ 9
2.3 System overview....................................................................................................... 11
2.3.1 Types of switching .............................................................................................. 12
2.3.2 Types of connection ........................................................................................... 13
2.3.3 Housing.............................................................................................................. 14
2.3.4 Selector switch................................................................................................... 14
2.3.5 Change-over selector ......................................................................................... 14
2.4 Contacts................................................................................................................... 14
2.5 Vacuum interrupters.................................................................................................. 14
2.6 Transition resistors .................................................................................................... 14
2.7 Spring-loaded mechanism ........................................................................................ 14
2.8 Motor-drive mechanism ............................................................................................ 14
2.9 Accessories and protection devices.......................................................................... 14
2.10 Rating plate ............................................................................................................ 16
3. Commissioning................................................................................................................. 17
3.1 General..................................................................................................................... 17
3.2 Reassembly .............................................................................................................. 17
3.3 Required tools and materials..................................................................................... 17
3.4 Tightening torques .................................................................................................... 18
3.5 Oil lling .................................................................................................................... 18
3.5.1 Oil quality............................................................................................................ 18
3.5.2 Filling methods and restrictions........................................................................... 18
3.5.3 Correct oil level................................................................................................... 18
3.5.4 Filling at atmospheric pressure............................................................................ 18
3.5.5 Filling under vacuum........................................................................................... 19
3.6 Mounting of external drive shafts............................................................................... 20
3.6.1 Mounting of horizontal drive shaft ....................................................................... 20
3.6.2 Mounting of vertical drive shaft ........................................................................... 23
3.7 Testing ...................................................................................................................... 27
3.8 Energizing................................................................................................................. 28
3.9 Putting into operation................................................................................................ 28

4. Operation ......................................................................................................................... 29
4.1 Synchronization between tap-changer and motor-drive mechanism.......................... 29
5. Inspection......................................................................................................................... 30
5.1 General..................................................................................................................... 30
5.2 Inspection................................................................................................................. 30
5.3 Checking oil quality ................................................................................................... 31
5.4 Maintenance ............................................................................................................. 31
5.5 Replacement of the complete switching mechanism including vacuum interrupters .. 31
6. Troubleshooting................................................................................................................ 32
7. Repairs and adjustments .................................................................................................. 33
7.1 General..................................................................................................................... 33
8.1.1 Serial number ..................................................................................................... 33
7.2 Oil leakage................................................................................................................ 33
7.2.1 General .............................................................................................................. 33
7.2.2 Tools required..................................................................................................... 33
7.2.3 Materials and spare parts required...................................................................... 33
7.2.4 Procedure .......................................................................................................... 33
7.3 Replacement of pressure relay .................................................................................. 35
8. Electrical diagrams ........................................................................................................... 36
8.1 Standard circuit diagram BUE ................................................................................... 37
8.2 Contact timing diagram BUE..................................................................................... 38
8.3 Standard circuit diagram BUL2 ................................................................................. 39
8.4 Contact timing diagram BUL2................................................................................... 40
9. Technical data .................................................................................................................. 41
9.1 Dimensions............................................................................................................... 41
9.2 Weights .................................................................................................................... 41
9.3 Specication of materials .......................................................................................... 41
9.3.1 General .............................................................................................................. 41
9.3.2 Tap-changer housing.......................................................................................... 41
9.3.3 Selector switch................................................................................................... 41
9.3.4 Gearing mechanism ........................................................................................... 42
9.3.5 Drive shaft system .............................................................................................. 42

1ZSC000562-AAL en | User’s guide VUBB 5
1. Safety
1.1 General
This user‘s guide must be read and understood must be
followed at all times.
1.2 Safety warnings
The following warnings and notes are used in the manual:
WARNING
WARNING indicates an imminently hazardous
situation which if not avoided, will result in death or
serious injury. This signal word is to be limited to the
most extreme situations.
WARNING also indicates a potentially hazardous
situation which if not avoided, could result in death or
serious injury.
CAUTION
CAUTION indicates a potentially hazardous situation
which if not avoided, may result in minor or moderate
injury. It may also be used to alert against unsafe
practices.
CAUTION may also indicate property-damage-only
hazards.
INFO provides additional information to assist in
carrying out the work described and to provide
trouble-free operation.
1.3 Safety precautions
1.3.1 Personal safety
Unused transformer oil is somewhat harmful. Fumes from
unused warm oil may irritate the respiratory organs and the
eyes. After long and repeated contact with transformer oil, the
skin becomes very dry. Avoid contact with the oil as much as
possible and use oil-tight protective gloves when handling the
oil.
Used tap-changer oil contains harmful substances. Fumes are
irritating to the respiratory organs and the eyes and very easily
catch fire. Used transformer oil may be carcinogenic.
1.3.2 Environmental safety
Collect used oil in oil drums.
An absorbing agent should be used when cleaning up waste
oil. Treat waste oil as hazardous to the environment.
1.3.3 First aid
Skin contact
1. Wash the body part that has been exposed to the oil.
2. Rub moisturizer into the skin to counteract drying.
In the eyes
Rinse the eyes with clean water.
Swallowing
WARNING
Avoid vomiting.
1. Drink water or milk.
2. Call a doctor.
1.3.4 In the event of fire
In the event of fire, extinguish with a powder, foam or carbon
acid extinguishing agent.

6 User’s guide VUBB | 1ZSC000562-AAL en
2. Introduction
2.1 General
The on-load tap-changers manufactured by ABB have been
developed over a period of many years to provide maximum
reliability. In most applications, the simple and robust
design provides a service life equal to the service life of the
transformer.
Minimum maintenance is required for trouble-free operation.
Maintenance is normally not required on the parts situated
in the oil of the transformer tank. The only parts requiring
maintenance are the vacuum interrupters (which may
require replacement), the insulating oil and the motor-drive
mechanism.
WARNING
Small amounts of explosive gases are constantly
discharged from the breathing devices (dehydrating
breather or one-way breather). Make sure that no
open fires, hot surfaces or sparks are present in the
immediate surroundings of the breathing devices.
Personnel operating and inspecting the tap-changer
must have good knowledge of the apparatus and be
aware of the risks pointed out in this manual.
Personnel making electrical connections in the motor-
drive mechanism must be certified for such work.
CAUTION
After a pressure relay trip, contact ABB. The tap-
changer housing must be drained and the selector
switch lifted and carefully examined before the
transformer is reenergized.
2.2 Functional description
The on-load tap-changer is a device for changing the tapping
connection of a winding while the transformer is under load.
The main purpose is to maintain a constant voltage out from
the transformer and to compensate for variations in the load
situation. The tap-changer is connected to the transformer
via the tap winding. The main function is tap selection, which
is accomplished by changing the number of turns on the
regulating winding.
Although numerous different circuit solutions are available,
the selected solution has been found to offer the best
combination of technical performance and potential
for economic operation. By using auxiliary contacts in
combination with vacuum interrupters, the contacts are used
for carrying current and the vacuum interrupters are used
for energized switching. With this solution, only two vacuum
interrupters are required per phase.
The electrical circuit principle for the VUBB is shown in
Figs.1-18. The purpose of the operation is to commute the
load from one tap to the other in order to change the voltage.
Depending on in which direction the center shaft is rotating,
two different contact sequences are obtained – either the
main contacts operate first, or in the other direction, the
transition contacts operate first.
The figures on the following pages show the contact
sequence along with the physical position of the interrupter.

1ZSC000562-AAL en | User’s guide VUBB 7
12
12
12
12
12
2.2.1 Switching sequence, operation with resistor side
first
1. Position for continuous load through fixed contact 1.
2. Resistor auxiliary contact disconnects from fixed
contact1.
3. Resistor vacuum interrupter opens.
4. Resistor auxiliary contact connects to fixed contact 2.
5. Resistor vacuum interrupter closes, producing a circulating
current.
Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.

8 User’s guide VUBB | 1ZSC000562-AAL en
12
12
12
12
6. Main vacuum interrupter opens, breaking the circulating
current and commuting the load current to the resistor
branch.
7. Main auxiliary contact disconnects from fixed contact 1.
8. Main auxiliary contact connects to fixed contact 2.
9. Main vacuum interrupter closes, commuting the load
current to the main branch. Continuous load on fixed
contact 2.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.

1ZSC000562-AAL en | User’s guide VUBB 9
12
12
12
12
12
2.2.2 Switching sequence, operation with main contact
first
1. Position for continuous load through fixed contact 2.
Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13.
Fig. 14.
2. Main vacuum interrupter opens, breaking the load current,
and in doing so commutes it to the resistor branch.
3. Main auxiliary contact disconnects from fixed contact 2.
4. Main auxiliary contact connects to fixed contact 1.
5. Main vacuum interrupter closes. The load current
commutes to the main branch, producing a circulating
current.

10 User’s guide VUBB | 1ZSC000562-AAL en
12
12
12
12
Fig. 15.
Fig. 16.
Fig. 17.
Fig. 18.
6. Resistor vacuum interrupter opens, breaking the
circulating current.
7. Resistor auxiliary contact disconnects from fixed
contact2.
8. Resistor vacuum interrupter closes.
9. Resistor auxiliary contact connects to fixed contact 1.