ABB UC Series User manual

Brand: ABB

Model: UC Series

Type: User manual

This manual is also suitable for

On-load tap-changer, type UC with

motor-drive mechanisms, type BUE/BUL

Repair guide

1ZSE 5492-129 en, Rev. 6

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 for service and repair work

on on-load tap-changers.

Do not repair an on-load tap-changer or motor-drive mechanism with a serious mechanical

or electrical fault without rst consulting ABB.

Before you start any work, make sure that the personnel doing the job have read and fully

understood the Repair documents 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

Before any work is carried out on the on-load tap-changer:Make sure that the trans-

former is disconnected and that earthing is properly carried out. Obtain a signed

certicate from the engineer in charge.

The relevant technical documents should be read and understood before any work is

started, and the procedures in this document should be followed at all times.

Before carrying out work on the on-load tap-changer, put the LOCAL/REMOTE switch

in the motor-drive mechanism to position 0. It is also recommended to shut the door

of the motor-drive mechanism and pad lock it when work is carried out on the on-load

tap-changer. The key should be kept by the operator. This is done to avoid unexpect-

ed start of the motor-drive mechanism.

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.

Be aware of the risk for slipperiness caused by oil spillage for instance when working

on the transformer cover.

CAUTION

ABB recommends that only service engineers with appropriate skills regarding on-load tap-

changers carry out the repairs.

ABB recommends that only maintenance engineers trained by ABB carry out contact re-

placement.

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 surroundings 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 this guide.

During oil handling

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 absorber. Treat it as hazardous to

the environment.

Upon re: The re should be extinguished by using powder, foam or carbon acid.

WARNING

When oil that has been used in a diverter 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.

The oil in the diverter switch compartment may be hot. Be cautious!

There is always a cushion of explosive gases over the oil surface. This is sucked into

the on-load tap-changer tank during draining of the oil. No open re, hot surfaces or

sparks may be present when the top cover is opened.

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.

Leave a gas cushion on top of the oil in the diverter switch housing.

Take care to avoid ingestion of moist air when oil is drained. If the ambient air is moist, let

incoming air pass through a dehydrating breather with slow air ow to obtain proper dehy-

dration.

NOTE: Check the oil level one month after lling. It is usual for the oil level of the oil

conservator to fall due to gas absorption in the oil from the gas cushion in the diverter

switch housing, if the on-load tap-changer is not operated. Restore the gas cushion

and the oil level according to section 3.3.

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 1.6

Tightening torque, in this guide.

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.

Contents

1. Introduction _______________________________________________________9

1.1 General _______________________________________________________9

1.2 Repair categories _______________________________________________9

1.3 Serial number __________________________________________________11

1.4 Spare parts list _________________________________________________11

1.5 Maintenance guide ______________________________________________12

1.6 Tightening torque _______________________________________________12

2. Trouble-shooting ___________________________________________________13

2.1 On-load tap-changer ____________________________________________13

2.2 Pressure relay __________________________________________________14

2.3 Motor-drive mechanism __________________________________________15

2.3.1 Control system _____________________________________________15

2.3.2 Power system ______________________________________________17

2.3.3 Miscellaneous ______________________________________________17

3. Repairs and adjustments ____________________________________________22

3.1 Replacement of gear box on the on-load tap-changer or

replacement of o-rings for the gear box ________________________________22

3.1.1 General ___________________________________________________22

3.1.2 Tools required ______________________________________________22

3.1.3 Material and spare parts required ______________________________22

3.1.4 Procedure _________________________________________________23

3.2 Replacement of diverter switch housing cover gasket ________________27

3.2.1 General ___________________________________________________27

3.2.2 Tools required ______________________________________________27

3.2.3 Material and spare parts required ______________________________27

3.2.4 Procedure _________________________________________________27

3.3 Restoring the gas cushion _______________________________________28

3.3.1 General ___________________________________________________28

3.3.2 Equipment required _________________________________________28

3.3.3 Procedure _________________________________________________28

3.4 Replacement or addition of a multi-position switch (BUL only) __________30

3.4.1 General ___________________________________________________30

3.4.2 Tools Required _____________________________________________30

3.4.3 Procedure _________________________________________________30

3.5 Examination of the diverter switch after a pressure relay trip ___________32

3.5.1 Tools and material required ___________________________________32

3.5.2 Procedure _________________________________________________32

3.6 Tests of the pressure relay ________________________________________33

3.7 Replacement of pressure relay ___________________________________34

3.7.1 General ___________________________________________________34

3.7.2 Tools required ______________________________________________34

3.7.3 Spare parts required ________________________________________34

3.7.4 Procedure _________________________________________________34

1ZSE 5492-129 en, Rev. 6

1. Introduction

1.1 General

The UC range of on-load tap-changers manufactured by ABB has been developed over

many years to provide maximum of reliability. The simple and rugged design gives a service

life equal to the service life of the transformer. Minimum maintenance is required for trouble-

free operation. The only parts requiring maintenance are contacts that might need replace-

ment during the service life, the insulating oil and the motor-drive mechanism.

The design allows excellent access to all parts, making inspection and maintenance quick

and simple.

The on-load tap-changers, type UC, are housed in the transformer tank. The motor-drive

mechanisms, types BUE or BUL are attached to the transformer tank and connected to the

on-load tap-changer by means of drive-shafts and a bevel gear, see Figs. 1 and 2.

1.2 Repair categories

Repairs on the UC range of on-load tap-changers fall into two categories:

■ Repairs. Repairs are to replace worn or end-of-service-life parts.

■ Modications. Modications are only issued by ABB to improve the already very high

standard of reliability and to assist in prolonging the service life of the equipment.

The modications fall into two areas:

- Immediate, where the modication should be completed at the earliest possible oppor-

tunity.

- Routine, where the modication should be completed during a routine service interval.

1. Introduction

1ZSE 5492-129 en, Rev. 6

Bottom valve for

drying process

Pressure relay

Top-section

Shielding-ring

Diverter switch

Plug-in contacts

Bottom section

Oil valve

Cover

Driving disc for the

diverter switch

Insulating cylinder

Draining tube

Guide-pins

Current terminal

Transition resistors

Fixed and moving

contacts

Intermediate gear

Insulating shaft

Bevel gear

Position indicator

Fig. 1. General arrangement of on-load tap-changer, type UC.

Earthing terminal

Serial No.

Diverter switch housing

Serial No.

Connection ange for

gas operated relay

Shielding-ring

1) Only at impulse withstand

voltage to earth of 650 kV

and 1050 kV

2) Not on UCG of the short type

Tap selector

Fixed ne-selector

contacts

Moving ne-

selector contacts

Change-over

selector

Geneva gear

Current collector

1. Introduction

1ZSE 5492-129 en, Rev. 6

1.3 Serial number

Before consulting ABB for technical advice to assist with repairs or to order spare parts to

complete the repairs, the on-load tap-changer serial number must be known. The serial

number can be found on the following locations:

■ Rating plate on the motor-drive mechanism (Fig. 2)

■ Diverter switch housing (Fig. 1)

■ Diverter switch (Fig. 1)

■ Tap selector (Fig. 1)

If the on-load tap-changer serial number cannot be obtained, the transformer serial number

should be used (only if the transformer is manufactured by ABB in Ludvika, Sweden).

NOTE: One of these serial numbers must be quoted in all correspondence and telefax

messages, and during any telephone conversations with ABB. Failure to use the serial

number may cause delays.

Serial No.

BUL

FM_00006

FM_00200

BUE

1.4 Spare parts list

The Repair guide does not contain information about spare parts and how to order them.

For information about spare parts, please refer to the 1ZSE 5492-133 Spare parts list for the

UC range of on-load tap-changers with motor-drive mechanisms, types BUE and BUL.

The Spare parts list also contains several exploded views, which can be very handy when

making repairs.

1. Introduction

Fig. 2. Rating plate.

1ZSE 5492-129 en, Rev. 6

1.5 Maintenance guide

Inspection and overhaul of the UC range of on-load tap-changers are carried out accord-

ing to the instructions in the appropriate Maintenance guide. You will need the Maintenance

guide since references are made to it.

1.6 Tightening torque

The following tightening torques are recommended

for metallic screw joints: M6, 10 Nm ±10 %

M8, 24.5 Nm ±10 %

M10, 49 Nm ±10 %

M12, 84 Nm ±10 %

for non-metallic screw joints: M10, 9 Nm ±10 %

M12, 13 Nm ±10 %

M16, 22 Nm ±10 %

if not otherwise is stated in this guide.

1. Introduction

1ZSE 5492-129 en, Rev. 6

2. Trouble-shooting

This chapter mainly contains information used to locate a fault. Instructions for correcting the

fault, replacement of parts etc. are contained in chapter 3 Repairs and Adjustments.

2.1 On-load tap-changer

Error condition Fault ﬁnding procedure

High oil level alarm. A rising oil level in the on-load tap-changer oil con-

servator may indicate a leakage between the diverter

switch housing and the transformer tank.

Make sure that the cause for the alarm is not over-lling

at commissioning or overhaul. This can be checked

by adjusting the oil level according to the transformer

documentation and then rechecking some time later.

Low oil level in the oil conser-

vator

1. Check for leakages.

2. If no leakages are found, the gas cushion is solved

in the oil and should be restored. Follow the instruc-

tions in section 3.3 in this guide.

Pressure relay trip See section ”Pressure relay” in this guide.

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

2.2 Pressure relay

WARNING

To take the transformer into service after a pressure relay trip without carrying out a

careful investigation of the diverter switch by lifting it out of the diverter switch hous-

ing, and repairing faults, if any, may cause severe damages to the on-load tap-chang-

er and the transformer.

Error condition Fault ﬁnding procedure

The pressure relay has tripped

during normal operation.

1. Examine the diverter switch according to section

3.5 ”Examination of the diverter switch after a pres-

sure relay trip” in this guide. Continue with steps 2

and 3 if no fault is found.

2. Carry out tests on the pressure relay according

to section 3.7 ”Tests of the pressure relay” in this

guide.

3. The on-load tap-changer is now ready for service.

Fig. 3. Pressure relay.

Information plate

Valve handle

Test tap (R 1/8’’)

TC_00264

Connection nut

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

2.3 Motor-drive mechanism

2.3.1 Control system

Error condition Fault ﬁnding procedure

LOCAL operation or

REMOTE operation is not

possible.

1. LOCAL operation is not possible when the control

selector switch is in position REMOTE or 0, and

REMOTE operation is not possible in position LOCAL

or 0.

2. Check the power supply both for control and motor.

3. Check if the protective motor switch has been re-

leased.

4. Check if the emergency stop has been pressed.

Release by turning clockwise and reset the protective

motor switch.

5. Check if the running-through protection has been re-

leased. Reset by setting the LOCAL/REMOTE switch

to 0 and then back to previous position and after that

reset the protective motor switch.

6. If the motor-drive has been handcranked against the

mechanical endstop, handcrank back to end-position.

The on-load tap-changer

performs more steps than

ordered, or operates to-

wards the end stop.

1. Check that the maintaining contact releases after

operation.

WARNING

Dangerous voltage!

2. Check that the raise and lower contactors function

properly (see circuit diagram, Fig. 4 respectively

Fig. 6, and contact timing diagram, Fig. 5 respectively

Fig. 7).

BUE:

3. Check that the brake disc stops in its middle posi-

tion with a tolerance of ±25 degrees. For information

about how to adjust the brake, refer to the Mainte-

nance guide.

4. Check that the starting contact fuctions properly (see

circuit diagram and contact timing diagram).

BUL:

3. Check that the roller on the brake arm stops in the

middle of the notch in the cam disc.

For information about how to adjust the brake, see

the Maintenance guide.

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

Error condition Fault ﬁnding procedure

The remote position indicator

shows wrong position or there

is no signal

1. If there is a measuring amplier:

Adjust the output signal from the measuring ampli-

er with its two adjustment screws. If the failure

does not disappear, proceed as follows:

WARNING

Dangerous supply voltage!

Measure the output signal from the measuring

amplier in all positions. The signal shall raise linear

up to the highest position.

If no signal, check the feeding to the measuring

amplier and to the position transmitter.

Check that the signal reaches the position indica-

tor.

2. Measure the resistance on the terminals of the

position transmitter in all positions after both raise

and lower operations.

WARNING

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.

BUE:

3. Check that the contact plate and arm on the

multi-position switch are free from dust and oxide.

Check the contact function with the moving con-

tact arm in all positions.

Check the resilience of the moving contacts in the

multi-position switch.

For information about how to adjust the resilience,

see the Maintenance guide.

BUL:

3. If the resistances are wrong replace the position

transmitter. See section 3.4 in this guide.

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

2. Trouble-shooting

2.3.2 Power system

Error condition Fault ﬁnding procedur

The three-phase motor runs

back and forth without the

on-load tap-changer changes

position.

Reverse two of the phases of the incoming supply.

WARNING

Dangerous voltage!

2.3.3 Miscellaneous

Error condition Fault ﬁnding procedure

Corrosion and/or condensa-

tion in the motor-drive mecha-

nism cabinet.

1. Check the function of the heater. Refer to section

Heater in the Maintenance guide.

2. Check that the air vents not have been blocked.

Water in the motor-drive

mechanism cabinet.

1. Adjust the hinges on the cabinet door.

2. Replace the door gasket on the cabinet.

1ZSE 5492-129 en, Rev. 6

Continuation contact is only included when the on-load tap-changer has through positions.

Closed when the on-load tap-changer is in through positions.

fm_00236

Fig. 4. Standard circuit diagram BUE.

For actual information use the circuit diagram delivered with your on-load tap-changer.

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

fm_00237

Fig. 5. Contact timing diagram BUE.

2. Trouble-shooting

1ZSE 5492-129 en, Rev. 6

Continuation contact is only included when the on-load tap-changer has through positions.

Closed when the on-load tap-changer is in through positions.

fm_00238

Fig. 6. Standard circuit diagram BUL.

For actual information use the circuit diagram delivered with your on-load tap-changer.

2. Trouble-shooting

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ABB UC Series User manual

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Model: UC Series

Type: User manual

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