ABB UZE User manual

On-load tap-changers, type UZE and UZF,
with motor-drive mechanism, type BUF 3
Installation and commissioning guide
1ZSE 5492-115 en, Rev. 5

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.

Recommended practices
ABB recommends careful consideration of the following factors when installing on-load tap-
changers:
Before you install or commission a unit, make sure that the personnel doing the job have
read and fully understood the Installation and Commissioning Guide provided with the unit.
To avoid damaging the unit, never exceed the operating limits stated in delivery documents
and on rating plates.
Do not alter or modify a unit without rst consulting ABB.
Follow local and international wiring regulations at all times.
Use only factory authorized replacement parts and procedures.
WARNING, CAUTION and NOTE
WARNING
A WARNING provides information which, if disregarded, could cause injury or death.
CAUTION
A CAUTION provides information which, if disregarded, could cause damage to the equip-
ment.
NOTE: A NOTE provides additional information to assist in carrying out the work de-
scribed.
Safety precautions
WARNING
Unused transformer oil is slightly harmful. Fumes from unused warm oil may irritate
the respiratory organs and the eyes. After long and repeated contact with transformer
oil skin becomes very dry.
Used on-load tap-changer oil from diverter switch housings and selector switch
housings contains harmful substances. Fumes are irritating to the respiratory organs
and the eyes and are very easily set on re. Used transformer oil may well be carcino-
genic.
Avoid contact with the oil as much as possible and use oiltight protective gloves
when handling the oil.
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. Call a doctor.
Collect used oil in oil drums.Waste and cleaning up: Should be absorbed by an ab-
sorber. Treat it as hazardous to the environment.
Upon re: The re should be extinguished by using powder, foam or carbon acid.

WARNING
The motor-drive mechanism must not be installed in any explosive atmosphere. The
electrical equipment creates sparks which can cause an explosion.
Before any work is carried out on the on-load tap-changer:
Make sure that the transformer is disconnected and that earthing is properly carried
out. Obtain a signed certicate from the engineer in charge.
Before starting any work in the on-load tap-changer the protective motor switch and
the LOCAL/REMOTE switch must be set at ”0”.
Before starting any work inside the motor-drive mechanism, the auxiliary power must
be switched off.
N.B. The motor, contactors and heating element may be energized from separate
sources.
During drying of the transformer
CAUTION
The on-load tap-changer must not be included in the vapour phase drying process of the
transformer. For permissible pressure and temperature at the rear during drying process, see
chapter 3.
Mounting of gaskets
CAUTION
Sealing surfaces and gaskets must be clean and undamaged. Diametrically opposed bolts
in sealing joints must be tightened alternately several times, beginning with a low tighten-
ing torque and nally with the recommended tightening torque as described in section 1.7
Tightening Torque, in this guide.
During oil lling
WARNING
When oil that has been used in a selector switch compartment is pumped out, con-
ducting tubes and hoses that are earthed should be used to avoid the risk of explo-
sion due to the gases produced by the arcs during service.
CAUTION
Do not ll oil into the on-load tap-changer if the transformer tank is under vacuum and the
on-load tap-changer is not.
Do not ll oil into the transformer tank if the on-load tap-changer is under vacuum and the
transformer tank is not.
The oil level in the oil conservator of the on-load tap-changer should never be above the oil
level in the oil conservator of the transformer.

After oil lling
CAUTION
Do not energize the transformer earlier than three hours after oil lling in atmospheric pres-
sure. This waiting period is needed to allow airbubbles to disappear.
During service
WARNING
Small amounts of explosive gases will always come out from the breathing devices
(dehydrating breather or one-way breather). Make sure that no open re, hot surfaces
or sparks occur in the immediate surrounding of the breathing devices.
If a failure in power supply occurs during operation, the operation will be completed
when the power returns.
The hand crank must not be inserted during electrical operation.
If the on-load tap-changer is not in its exact position and the hand crank is pulled out,
the motor-drive mechanism will start and go to the exact position if the power supply
is on.
CAUTION
After a pressure relay trip, follow the instructions in the chapter ”Pressure Relay” in the Re-
pair Guide.
The pressure relay is a calibrated monitoring instrument. It must be handled with care and
protected against careless handling or any kind of mechanical damage.

Contents
1. Introduction _______________________________________________________9
1.1 Required tools _________________________________________________10
1.2 Required material _______________________________________________10
1.3 Oil____________________________________________________________11
1.4 Oil conservator _________________________________________________11
1.5 Filter unit for continuous oil ltration________________________________13
1.6 Weights _______________________________________________________13
1.7 Tightening torque _______________________________________________13
2. Receiving _________________________________________________________14
2.1 Unpacking_____________________________________________________14
2.2 Inspection upon receiving ________________________________________14
2.3 Temporary storage before assembly _______________________________14
3. Drying ____________________________________________________________15
4. Installation on the transformer ________________________________________16
4.1 Attaching the on-load tap-changer to the transformer ________________16
4.1.1 Welding ___________________________________________________16
4.1.2 Bolting ____________________________________________________16
4.1.3 Assembly of accessories_____________________________________18
4.1.4 Retightening _______________________________________________18
4.2 Connection of the regulating winding of the transformer_______________18
4.3 Connection to the oil conservator _________________________________20
5. Pressure relay _____________________________________________________21
5.1 General _______________________________________________________21
5.2 Installation _____________________________________________________21
5.3 Checking when commissioning the transformer _____________________22
6. Oil lling __________________________________________________________23
6.1 Filling methods and restrictions ___________________________________23
6.1.1 Retightening _______________________________________________23
6.2 Filling at atmospheric pressure ____________________________________23
6.3 Filling under vacuum ____________________________________________24
6.4 Correct oil level _________________________________________________24
7. Electrical connection and testing _____________________________________25
7.1 General _______________________________________________________25
7.2 Connecting and testing __________________________________________25
7.3 Electrical tests on transformer ____________________________________26
7.4 After energizing_________________________________________________26
7.5 Resistance measurement ________________________________________26
8. Transport _________________________________________________________27
8.1 Oil level during transport _________________________________________27
8.1.1 Transformer lled with oil _____________________________________27
8.1.2 Transformer drained _________________________________________27

9. Commissioning ____________________________________________________28
9.1 Reassembly ___________________________________________________28
9.2 Oil lling _______________________________________________________28
9.2.1 Dehydrating breather ________________________________________28
9.3 Electrical connection and testing __________________________________28
9.3.1 Motor protection____________________________________________28
9.3.2 Counter ___________________________________________________28
9.3.3 Position transmitter and other multi-position switches ____________28
9.3.4 Light______________________________________________________28
9.3.5 Heater ____________________________________________________29
9.3.6 Pressure relay ______________________________________________29
9.4 Putting into operation ___________________________________________29
APPENDIX A. Welding and mounting instruction __________________________30
A1 Introduction ______________________________________________________30
A1.1 Required tools ________________________________________________30
A2 Receiving ________________________________________________________31
A2.1 Temporary storage before assembly ______________________________31
A3 Welding and mounting instruction ____________________________________31
A3.1 Welding of the ange and frame for the motor-drive mechanism ______31
A3.2 Installing the on-load tap-changer and the motor-drive
mechanism in the tank ______________________________________________33
A3.2.1 Installation of the on-load tap-changer ________________________33
A3.2.2 Installation of the motor-drive mechanism _____________________35
A3.3 Mounting of ttings for motor-drive mechanism cabinet______________37
A3.4 Welding of the ange and mounting of the pressure relay ____________38
A4 Welding instruction for inclined assembly______________________________39
A4.1 Welding of ange and frame for motor-drive mechanism _____________39
A4.2 Mounting of the on-load tap-changer _____________________________40

9
1ZSE 5492-115 en, Rev. 5
fm_00069
1 Introduction
1. Introduction
The on-tank concept of on-load tap-changer, realized by ABB in the UZ range, is unique.
The design offers advantages in installation and maintenance. The whole device is delivered
installed in a tank that is simply mounted onto the transformer tank together with the motor-
drive mechanism.
In the event of an on-load tap-changer being delivered without a tank, the transformer
manufacturer will supply the tank. Appendix A includes a welding and mounting instruction.
It is easy to access all parts of the on-load tap-changer for maintenance and repair. After
draining the oil, you simply unbolt and open the front cover to access any part you may
need to inspect or replace.
Lifting eye
Connection to oil conservator
On-load tap-changer tank
Oil valve
Pressure relay
Terminals for
conductors
Attachment ange to
transformer tank
Cover for access to conductors,
UZFonly
Fig. 1. General arrangement of on-load tap-changer.

10 1ZSE 5492-115 en, Rev. 5
UZE requires the transformer conductors to be accessed from the rear of the on-load tap-
changer.
UZF has an inclined rear wall and a top cover that is removable to provide access to the
transformer conductors.
WARNING
The cover for access to conductors on top of UZF tank may be opened after draining
the transformer main tank.
UZE models are available for use without a separate oil conservator. For example, when
used on sealed tank transformers.
1.1 Required tools
■Normal set of screwdrivers
■Normal set of open-end wrenches
■Hexagonal wrench, 8 mm
■Dynamometric wrench (5-85 Nm)
■Air pump with pressure gauge and connection to male thread R 1/8” (0-100 kPa)
■Flexible tube with connection, internal thread R 1/8”
■Tool for opening of oil drums
■Clamping blocks, (only for installation)
■Small brush (width 10 mm, only for installation)
1.2 Required material
■Equipment for oil lling for connection to the oil valve. For dimensions see the dimension
drawing.
■Equipment for connection between the on-load tap-changer and the transformer when
lling under vacuum.
■Sealing tape
■Glue (ABB 1 3401-608), 0.5 kg (contact adhesive on nitrile rubber base, only for instal-
lation)
■Oil as per section 1.3
■Maintenance Guide, 1ZSE 5492-123
■Circuit diagram for the motor-drive mechanism
1 Introduction

11
1ZSE 5492-115 en, Rev. 5
1.3 Oil
The oil quality should be IEC 60296-LCSET -30° (former Class II). The oil should have an
electrical withstand of at least 40 kV, measured in a 2.5 mm gap, according to IEC 60156.
New oil should have a water content below 15 ppm and have been handled and stored ac-
cording to IEC 60422 point 10.
Table 1. Weight of oil in kg.
Type designation
UZE.N, UZE.T
OLTC with separate
conservator 1)
OLTC with expansion volume
in the tank
200/... 500 450
250/... 500 450
380/... 950 880
550/... 1250 1150
650/... 1250 1150
Type designation
UZF.N, UZF.T
OLTC with separate
conservator 1)
OLTC with expansion volume
in the tank
200/... 400 430
250/... 400 430
380/... 750 800
550/... 1050 1120
650/... 1050 1120
1) The oil for the conservator is not included.
WARNING
Do not energize the transformer until oil has been lled as per chapter 6, Oil Filling, in
this guide.
1.4 Oil conservator
The on-load tap-changer has to be connected to an oil conservator, except when it is an
UZE with expansion volume in the tank. ABB recommends the use of a separate conserva-
tor for the on-load tap-changer with both oil and air side separated from the main conserva-
tor of the transformer.
The volume of the conservator should be such that there is oil left in the conservator even at
the lowest oil temperature expected and such that no ooding can occur at the highest oil
temperature expected.
A suitable dimension of the tube for connection to the conservator is an inner diameter of
approximately 20 mm. The tube should be inclined at least 3 degrees to avoid gas cushions
in the tube. A valve in the connection to the conservator is recommended.
The conservator must be equipped with a breathing device that does not allow moist air into
the conservator and that allows the gas from the arcs to disappear. We recommend that the
breather for the tap-changer should be bigger than normally used for that amount of oil, as
the tap-changer is breathing more frequently because of the gas produced at each tap-
changer operation.
The conservator should also be equipped with an oil level indicator, and an alarm contact for
low oil level is recommended.
1 Introduction

12 1ZSE 5492-115 en, Rev. 5
fm_00089
fm_00118
tc_00182
1 Introduction
Fig. 4. UZF with built-on oil conservator.
Fig. 3. UZE with oil expansion volume in the tank.
Fig. 2. UZE with separate oil conservator.
Min 3°

13
1ZSE 5492-115 en, Rev. 5
1 Introduction
1.5 Filter unit for continuous oil ltration
If the on-load tap-changer should have an oil lter unit for continuous oil ltration from ABB,
installation and commissioning instructions can be found in the manual for the oil lter unit,
”Oil Filter Unit for On-Load Tap-Changers, Manual” delivered with the oil lter unit.
1.6 Weights
Table 2 contains the approximate weights of all the models in the UZ range of on-load tap-
changers. The weight of the motor-drive mechanism is included in the overall weight.
Table 2. Weights for UZ on-load tap-changers in kg.
On-load tap-changer
Type designation
Tap-changer with tank
without oil
Insert without motor-drive
mechanism
UZE.N, UZE.T
200/... 700 220
250/... 700 220
380/... 930 270
550/... 1100 340
650/... 1100 340
UZF.N, UZF.T
200/... 720 220
250/... 720 220
380/... 900 270
550/... 1100 340
650/... 1100 340
The weight of the motor-drive mechanism is approximately 110 kg
1.7 Tightening torque
The following tightening torques are recommended:
M6, 10 Nm ±10 % (7.4 lbf x ft)
M8, 24.5 Nm ±10 % (18 lbf x ft)
M10, 49 Nm ±10 % (36 lbf x ft)
M12, 84 Nm ±10 % (62 lbf x ft)
Welded stud bolts
M12, 42 Nm (31 lbf x ft)
unless otherwise stated in this guide.

14 1ZSE 5492-115 en, Rev. 5
fm_00070
2. Receiving
2.1 Unpacking
Check that the package is free from transport damage. Open the cover of the transport box.
Remove the supporting blocks of wood. If the package is damaged a careful investigation
must be carried out.
Lift the on-load tap-changer, using the lifting eyes on the top.
2.2 Inspection upon receiving
1. Check that there is no visible damage.
2. Open the door of the cabinet of the motor-drive mechanism and check that the motor-
drive mechanism is free from damage.
3. If transport damage is found, and it is adjudged that correct operation of the on-load
tap-changer is not possible, a damage report should be sent to the insurance company.
It is also recommended that photographs be taken of the damaged details. Mark the
photos with the serial number of the on-load tap-changer and send them to ABB for
comments.
4. Check that the quantity delivered, the type designation and the serial number agree
with the delivery documents, e.g. the packing list or ABB’s ordering acknowledgement.
The serial number is stamped on the rating plate.
5. Remove the drying agent (placed according to Fig. 5), before the on-load tap-changer
is taken into service.
6. If the packing material seems to be wet (e.g the plastic is coated with moisture), the
on-load tap-changer must be dried at least 24 hours at a temperature of max. 70 °C
(158°F) before it is tted to the transformer. See chapter 3, Drying.
2 Receiving
Rating plate with
Serial No.
Fig. 5. Inspection on receipt
Drying agent
2.3 Temporary storage before assembly
If the on-load tap-changer is not to be installed on the transformer immediately, once the
delivery has been approved the on-load tap-changer must be kept warm and dry. Let the
unit be kept in its plastic enclosure and leave the drying agent until assembly.

15
1ZSE 5492-115 en, Rev. 5
3. Drying
Drying of the on-load tap-changer is normally not required, see section 2.2, step 6.
The following temperatures and pressures between the on-load tap-changer tank and the
transformer tank are allowed when drying:
Pressure Standard on-load tap-changer On-load tap-changer with reinforced
barrier
Zero Up to 115 °C (239 °F) on the
transformer side.
Up to 90 °C (194 °F) inside the tank.
Up to 115 °C (239 °F) on the
transformer side.
Up to 90 °C (194 °F) inside the tank.
Up to 100 kPa Up to 60 °C (140 °F). Up to 90 °C (194 °F).
100–150 kPa Not allowed. Up to 60 °C (140 °F).
The temperature inside the motor drive cabinet must not exceed 70 °C (158 °F).
During or after drying the on-load tap-changer must not be operated until it has been lled
with oil. The motor-drive mechanism should not be included in a vacuum process, as the
process would remove the grease necessary for operation.
3 Drying

16 1ZSE 5492-115 en, Rev. 5
fm_00071
4 Installation on the transformer
4. Installation on the transformer
CAUTION
The on-load tap-changer must not be included in the drying process of the transformer.
The on-load tap-changer is either bolted or welded to the transformer tank, see
section 4.1.
NOTE: In the event of the on-load tap-changer being delivered without a tank, the
transformer manufacturer has to make the tank and mount it onto the transformer
tank; or make the on-load tap-changer tank integrated with the transformer tank.
Appendix A includes a welding and mounting instruction. In this case, continue with
section 4.2 directly.
4.1 Attaching the on-load tap-changer to the transformer
4.1.1 Welding
For welding the on-load tap-changer to the transformer tank, use llet weld with a ≥ 4 mm
(Fig. 6).
4.1.2 Bolting
A set of cork-rubber gaskets is provided to seal against the transformer tank.
When you install the on-load tap-changer, the gasket should be glued as described below.
Tighten the bolts by approximately 90 Nm torque.
Ensure that the surfaces being in contact with the gaskets are clean and free from grease
and oil.
After cleaning, stick the gaskets to the transformer tank ange (Fig. 7) with ABB glue
13401-608, by brushing glue on both the gasket and the ange.
On-load tap-changer
ange
a ≥ 4 mm
Transformer tank
Fig. 6. Welding detail.

17
1ZSE 5492-115 en, Rev. 5
A
A
fm_00072
4 Installation on the transformer
After spreading the glue let it dry at room temperature for a minimum of 10 minutes and a
maximum of 30 minutes.
Keep the gaskets in the correct position by using clamping blocks for a minimum of 3 hours.
Glue the inner gasket bands only, both to the on-load tap-changer ange side and to the
transformer-tank ange side.
The required amount of glue (ABB 1 3401-608) is 0.5 kg.
Do not glue gaskets at temperatures below 0 °C (32 °F).
NOTE: ABB glue 1 3401-608 is a contact adhesive of nitrile rubber base.
May consist of
two gaskets
Supporting gasket
Sealing gasket
Corner gasket
View A – A
26
Fig. 7. Gluing the gasket.
10
Opening for
draining

18 1ZSE 5492-115 en, Rev. 5
4.1.3 Assembly of accessories
All details which have been removed for the transport are specied on the packing list. The
openings on the on-load tap-changer are then sealed by transport covers.
1. Remove the transport covers.
2. Check the O-rings. Make sure they are pressed into the bottom of the groove on the
anges.
3. Assemble the accessories. Tightening torque for the nuts as per section 1.7.
4.1.4 Retightening
When a gasket is subjected to the pressure from the ange bolts it will change its shape or
settle. This reduces the pressure on the bolts, making them loose.
The settling effect will increase at higher temperatures. For this reason retightening is re-
quired.
Retighten one day after assembly. Retighten again after the transformer has been in service
for about two weeks to let the gaskets settle at service temperature. The retightening torque
should again be approximately 90 Nm.
Retighten the dome nuts with 42 Nm before oil lling. See section 6.1.1.
4.2 Connection of the regulating winding of the transformer
On UZE the winding has to be connected from the rear.
On both UZE and UZF the cable lugs can be either crimped or brazed. The free distance
between the cable lugs for adjacent contacts must be at least 7 mm. Tightening torque is
38 Nm. For star point design, attach the neutral connection as shown in Fig. 8 and the con-
nection diagram.
On UZF the top cover is intended to be used when connecting the transformer’s regulating
winding leads to the on-load tap-changer terminals.
Remove the cover and connect the leads. Tightening torque is 38 Nm for the cable lugs.
For star-point design, attach the neutral connection as shown in Fig. 8 and the connection
diagram. Bolt on the cover. Tightening torque is 42 Nm for the dome nuts.
If the oil conservator is to be installed on the top of the on-load tap-changer, connect the
regulating winding leads before installing the oil conservator.
4 Installation on the transformer

19
1ZSE 5492-115 en, Rev. 5
fm_000196
4 Installation on the transformer
Fig. 8. Assembly of the neutral connection.
Neutral connection

20 1ZSE 5492-115 en, Rev. 5
fm_00073
4 Installation on the transformer
4.3 Connection to the oil conservator
See Fig. 9.
Remove the transport cover from the ange for the oil conservator. Check that the
O-ring is in place on the ange and connect the pipe to the oil conservator.
In cases where the oil conservator is installed directly on the top of the on-load tap-changer,
install the oil conservator directly on the ange with the connection sealed by an O-ring that
is left on the ange when the transport cover is removed. After that, the other bracket of the
conservator is mounted to the tank.
For UZ with normal barrier, the oil level difference between on-load tap-changer and trans-
former should be a maximum of 1.2 m. For a reinforced barrier, the oil level difference may
be 8 m.
CAUTION
Where the conservator is common to the transformer and the on-load tap-changer, an oil
lter must be placed in the pipe between the on-load tap-changer and the conservator.
Filter with housing can be ordered from ABB, ordering No. LL 114 004-AP.
O-ring 64.2 x 5.7
Ø 52
Ø 100
Ø 130
Stud M12
Fig. 9. Attachment ange for oil conservator.