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On-load tap-changers, type UCTechnical guide

Manufacturer’s declaration

The manufacturer ABB Components AB

SE-771 80 LUDVIKA

Sweden

Hereby declares that

The products On-load tap-changers

type UC

with motor-drive mechanisms

types BUE and BUL

comply with the following requirements:

By design, the machine, considered as component on a mineral oil filled power transformer, com-

plies with the requirements of

• Machinery Directive 89/392/EEC (amended 91/368/EEC and 93/44/EEC) and 93/68/EEC

(marking) provided that the installation and the electrical connection be correctly realized by the

manufacturer of the transformer (e.g. in compliance with our Installation Instructions) and

• EMC Directive 89/336/EEC regarding the intrinsic characteristics to emission and

immunity levels and

• Low Voltage Directive 73/23/EEC (modified by Directive 93/68/EEC) concerning the built-in

motor and apparatus in the control circuits.

Certificate of Incorporation:

The machines above must not be put into service until the machinery into which they have been

incorporated have been declared in conformity with the Machinery Directive.

Date 1997-02-10

Signed by .........................................................................

Olof Heyman

Title Manager of Division for tap-changers

This Technical Guide has been produced to allow transformer manufacturers, and their designersand engineers, access to all the technical information required to assist them in their selection ofthe appropriate on-load tap-changer and motor-drive mechanism. The guide should be used inconjunction with the Selection Guide and the Design Guides, to allow the optimum selection to bemade.

The technical information pertaining to on-load tap-changers and motor-drive mechanismsmanufactured by ABB Components has been divided and is contained in separate documents,with one document for each type.

The information provided in this document is intended to be general and does not cover allpossible applications. Any specific application not covered should be referred directly toABB Components AB, or its authorized representative.

ABB Components AB makes no warranty or representation and assumes no liability for theaccuracy of the information in this document or for the use of such information. All information inthis document is subject to change without notice.

ABB Components also manufactures the following products:

Transformer bushingsWall bushingsGIS bushings

General Information ____________ 4

Design Principles______________ 6

On-Load Tap-Changer_____________________ 6Diverter Switch ________________________ 6Tap Selector __________________________ 7Diverter Switch Housing and Top Section ___ 8Operating Mechanism __________________ 8Transition Resistors ____________________ 8

Motor-Drive Mechanism____________________ 9Type BUL ____________________________ 9Type BUE ____________________________ 9Special Applications ____________________ 9Accessories __________________________ 9

Principles of Operation _________ 10

On-Load Tap-Changer_____________________ 10Switching Sequence____________________ 10Linear Switching (Type L) _______________ 11Change-over Selector forPlus/Minus Switching (Type R) ___________ 11Change-over Selector forCoarse/Fine Switching (Type D) __________ 11

Characteristicsand Technical Data ____________ 12

On-Load Tap-Changer_____________________ 12Type Designation ______________________ 12Diverter Switches ______________________ 12Tap Selectors _________________________ 12Diverter Switch – Tap SelectorCombinations _________________________ 12Rated Phase Step Voltage _______________ 13Contact Life __________________________ 14Standards and Testing __________________ 15Rating Plate __________________________ 15Insulation Levels ______________________ 15Mechanical Life _______________________ 18Short-circuit Current Strength ____________ 19Highest Phase Service VoltageAcross the Regulating Winding ___________ 19Rated Through Current _________________ 19Occasional Overloading _________________ 19

Table of ContentsOil Temperature _______________________ 20Tie-ln Resistor ________________________ 20

Design, Installationand Maintenance ______________ 21

On-Load Tap-Changer_____________________ 21Design Differences over the UC Rangeof On-Load Tap-Changers _______________ 21Drying _______________________________ 21Painting _____________________________ 21Weights _____________________________ 22Oil Filling ____________________________ 23Installation ___________________________ 23Maintenance __________________________ 23Oil Filter Unit _________________________ 23Pressure Relay ________________________ 23

General Description _________________ 23Operation _________________________ 23Testing ___________________________ 23Installation _________________________ 23

Motor-Drive Mechanism____________________ 24Design ______________________________ 24Installation ___________________________ 24Maintenance __________________________ 24

Dimensions _____________________________ 25Type UCG/C __________________________ 25Type UCG/I __________________________ 26Type UCG/III _________________________ 27Type UCL ____________________________ 28Type UCD/III _________________________ 30Type UCC ___________________________ 32

Appendices:Single-Phase Diagrams _________ 34

Appendix 1:Single-Phase Diagrams for UCG/C ___________ 34Appendix 2:Single-Phase Diagrams for UCG/I ___________ 37Appendix 3:Single-Phase Diagrams for UCG/IIIUCL/III and UCD/III _______________________ 41Appendix 4:Single-Phase Diagrams for UCC _____________ 45

General InformationThe UC types of on-load tap-changers are usuallymounted inside of the transformer tank, suspended fromthe transformer cover. Drive to operate the on-load tap-changer is supplied from the motor-drive mechanism,which is mounted on the outside of the transformer tankaway from the on-load tap-changer. The drive istransmitted by means of shafts and bevel gears.

The UC types of on-load tap-changers come in a widerange of models with a rating suitable for everyapplication.

When the on-load tap-changer operates, arcing occurs inthe diverter switch. To avoid contamination of thetransformer oil, the diverter switch has its own housingseparate from the rest of the transformer. The tapselector, which is mounted beneath the diverter switchhousing, consists of the fine tap selector and usuallyalso of a change-over selector. The operating principlefor the UC range of on-load tap-changers is called thediverter switch principle.

Fig. 1. Main parts, on-load tap-changers type UC

4

Transformer cover

On-Load Tap-Changer

Motor-Drive Mechanism

Shaft

Bevel gear

Shaft

Transformer tank

Oil conservator

Fig. 2. On-load tap-changer type UCL

5

Earthing terminal

Vent plug

Oil valve

Cover

Lifting eye

Pressure relay withtesting valve

Top section

Shielding-ring

Current terminal

Bottom section

Valve for use atprocessing

Connections fromthe tap selector

Plug-in contacts

Insulating cylinder

Diverter switch

Intermediate gear

Driving disc for thediverter switch

Locating pins

Fixed and movingcontacts

Transition resistors

Shielding-ring

Insulating shaft

Bevel gear withmechanical indicator

Buffer springs

Diverter switch housing

Oil tube

Design PrinciplesOn-Load Tap-ChangerThe on-load tap-changer is built in two separatesections, the diverter switch, which has its own housing,and the tap selector. The tap selector is mounted belowthe diverter switch housing and the complete unit issuspended from the transformer cover.

Diverter Switch

The diverter switch is of the high-speed, spring-operatedtype with resistors as transition impedance.

The diverter switch is designed as a system of movingand fixed contacts. Movement of the moving contactsystem is controlled by a self-locking polygon linksystem with a set of helical springs. The link system isrobust and has been carefully tested. The fixed contactsare placed on the sides of the diverter switch, which aremade of insulated board.

The diverter switch is equipped with plug-in contacts thatautomatically connect the switch with the tap selectorwhen the diverter switch is lowered into the housing.Mechanical coupling to the motor-drive mechanism isautomatically established when the driving pin enters theslot in the driving disc.

The current-carrying contacts are made of copper orcopper and silver, and the breaking contacts ofcopper-tungsten.

The design and dimensioning of the diverter switchoffers high reliability and long life with a minimum ofmaintenance and easy inspection.

Fig. 4. Diverter switch (UCC)Fig. 3. Diverter switch (UCL)

6

L37049 L37050

7

Tap Selector

Although the tap selector for the UC range of on-loadtap-changer is available in various sizes, all have similarfunctions with different ratings.

The fixed contacts are mounted in a circle around thecentral shafts. The moving contacts are mounted on, andare operated by, the shafts in the center of the selector.The moving contacts are connected, via currentcollectors, to the diverter switch by means of paperinsulated copper conductors.

Depending on the load current, the moving contactshave either one, two, or more contact arms in parallelwith one, two or four contact fingers each. The fingersmake contact at one end with the fixed contact, and atthe other with the current collector. The moving contactsslide on the fixed contacts and the current collector rings,giving a wiping action which makes the contacts selfcleaning. This arrangement promotes good conductivityand negligible contact wear.

Fig. 6. Tap selector size III L36700Fig. 5. Tap selector size C L36698

Diverter Switch Housing andTop Section

The top section forms the flange that is used formounting to the transformer cover, and for carrying thegear box for the operating shafts. The top housingincludes a connection for the conservator pipe, drainingand filtering connections, an earthing terminal, thepressure relay, and the cover with its gasket.

The bottom section has locating holes for the diverterswitch, bearings, brackets for the tap selector mountingand the current terminal for the diverter switch. There isalso a draining valve in the bottom which should only beopened during the drying process of the transformer.

The top and bottom section are fixed to a cylinder ofglassfibre reinforced plastic. The bushings through thecylinder wall are sealed by O-ring gaskets with elasticpressure. Each ready-made unit is tested under vacuumand the outside is exposed to helium and checked forleaks with the use of a helium gas detector.

Operating Mechanism

The bevel gear, mounted on the top section flangetransfers the drive from the motor-drive mechanism, viathe vertical shaft, to the intermediate gear for the diverterswitch and the tap selector.

From the intermediate gear, a drive shaft transfers thedrive to the diverter switch through an oil tight gland inthe bottom of the diverter switch housing. When thediverter switch is lowered into the housing (afterinspection), the drive is automatically re-connected by asystem that ensures that the drive shaft and the locatingpin of the diverter mechanism is correctly aligned.

The intermediate gear also drives the geneva gear, ofthe tap selector, via a free wheel connection. Thegeneva gear provides alternate movement to the twovertical shafts of the tap selector.

Transition Resistors

The transition resistors are made of wire, wound oninsulating bobbins, and are located above the diverterswitch contacts. The resistors are robust and designedto withstand an unlimited number of operations.

8

Motor-Drive MechanismThe motor-drive mechanism provides the drive to allowthe on-load tap-changer to operate. As the name implies,drive is provided from a motor through a series of gearsand out through a drive shaft. Several features areincorporated within the mechanism to promote longservice intervals and reliability.

There are two sizes of motor-drive mechanisms that canbe used:

Type BUL

The BUL is for on-load tap-changers types UCG andUCL at star point or single-phase applications. However,when extra space is required for optional accessories thetype BUE might have to be selected due to limited spacein the BUL.

Type BUE

The BUE is for all on-load tap-changers types UCG,UCL, UCC and UCD.

For detailed operation description, see separateTechnical Guides for Motor-Drive Mechanisms typesBUL or BUE, respectively.

If there are any doubts about which type to select,please consult ABB Components.

Special Applications

ABB Components should be consulted for all specialapplication on-load tap-changers.

Accessories

For a list of accessories available for both the on-loadtap-changers and the motor-drive mechanisms, see theSelection Guide or consult ABB Components.

Fig. 7a. Motor-drive mechanism type BUE

9

Fig. 7b. Motor-drive mechanism type BULL37166 L37167

Principles of Operation

10

On-Load Tap-ChangerSwitching Sequence

The switching sequence of the on-load tap-changer fromposition 6 to position 5, is shown in the figures below.

The sequence is designated the symmetrical flag cycle.This means that the main switching contact of thediverter switch, breaks before the transition resistors areconnected across the the regulating step. This ensuresmaximum reliability when the switch operates withoverloads.

At rated load the breaking takes place at the first currentzero after contact separation, which means an averagearcing time of approximately 6 milliseconds. The totaltime for a complete sequence is approximately 50milliseconds. The tap change operation time of themotor-drive mechanism is approximately 5 seconds perstep. (10 seconds for through-positions.)

Fig 8a. Position 6

Selector contact V lies on tap 6 and selector contact Hon tap 7. The main contact x carries the load current.

Fig. 8b

Selector contact H has moved in the no-current statefrom tap 7 to tap 5. Fig. 8f. Position 5

The main contact v has closed, resistor Ru is bypassedand the load current passes through the main contact v.The on-load tap-changer is now in position 5.

Fig. 8e

The resistor contact y has opened. The load currentpasses through Ru and contact u.

Fig. 8d

The resistor contact u has closed. The load current isshared between Ry and Ru. The circulating current islimited by the resistance of Ry plus Ru.

Fig. 8c

The main contact x has opened. The load current pas-ses through the resistor Ry and the resistor contact y.

11

ReversingChange-over selector

Linear Switching (Type L)

The regulating range is equal to the voltage of thetapped winding. No change-over selector is used.

Change-over Selector for Plus/MinusSwitching (Type R)

The change-over selector extends the regulating rangeto twice the voltage of the tapped winding, by connect-ing the main winding to different ends of the regulatingwinding.

Change-over Selector for Coarse/Fine,Switching (Type D)

In type D switching the change-over selector extends theregulating range to twice the voltage of the tappedwinding, by connecting or disconnecting the coarseregulating winding.

Fig. 9. Linear switching (Type L)

Fig. 10. Plus/Minus switching (Type R)

Change-over selector,

Coarse/Fine

Fig. 11. Coarse/Fine switching (Type D)

Characteristics and Technical Data

12

On-Load Tap-ChangerType Designation

U C G . . XXXX/YYYY/ZU C L . . XXXX/YYYY/ZU C D . . XXXX/YYYY/ZU C C . . XXXX/YYYY

Example: UCGRE 650/700/C

Type of switchingL LinearR Plus/MinusD Coarse/Fine

Type of connectionN Three-phase star point (one unit)E Single-phase (one unit)T Three-phase fully insulated (three units)B Three-phase delta (two units; single-phase

and two-phase)

Impulse withstand voltage to earthUCG: 380 kV, 650 kV, 750 kV, 1050 kVUCL: 380 kV, 650 kV, 1050 kVUCD, UCC: 380 kV, 650 kV, 1050 kV

Maximum rated through-currentUCG.N, UCG.B: 300 A, 400 A, 500 A, 600 AUCG.E, UCG.T: 300 A, 400 A, 500 A, 600 A,

700 A, 900 A, 1050 A, 1200 A, 1500 A

UCL.N, UCL.B: 600 A, 900 AUCL.E, UCL.T: 600 A, 900 A, 1800 A, 2400 A

UCD.N: 1000 A, 1200 AUCD.E: 1000 A, 1200 A, 1800 A, 2000 A

2400 A, 3000 A, 3600 A 1)

UCC.N: 800 A, 1200 A, 1600 AUCC.E: 3600 A, 4500 A

Tap selector sizeC = UCG tap selectorI = UCG tap selectorIII = UCG, UCL and UCD tap selector

1) with enforced current splitting

Maximum number of positions

UCG, UCL, UCD UCCLinear switching 211) positions 23 positionsPlus/Minus switching 35 positions 35 positionsCoarse/Fine switching 35 positions 35 positions

Diverter Switches

Type Max. rated Impulse withstandthrough-current voltage to earth

UCG.N 300, 500, 600 A 380, 650, 750, 1050 kVUCG.E,T 300, 500, 600,

900, 1200, 1500 A 380, 650, 750, 1050 kVUCG.B 300, 500, 600 A 380, 650, 750, 1050 kV

UCL.N 600, 900 A 380, 650, 1050 kVUCL.E,T 600, 900, 1800, 2400 A 380, 650, 1050 kVUCL.B 600, 900 A 380, 650, 1050 kV

UCC.N 800, 1200, 1600 A 380, 650, 1050 kV

UCC.E 3600, 4500 A 380, 650, 1050 kV

Tap Selectors

Type Connection Max. rated Max. no. Max impulsethrough- of pos. test voltagecurrent across range

C N 400 A 27 350 kVE, T 400, 700, 1050 A 27 350 kVB 400 A 27 350 kV

I N 600 A 35 300 kVE, T 600, 1200, 1500 A 35 300 kVB 600 A 35 300 kV

III N 1000 A 35 550 kVE, T 1000, 1800, 2400

30001) A 35 550 kVB 1000 A 35 550 kV

UCC 2) N 800, 1200, 1600 A 35 500 kVE 3600, 4500 A 35 500 kV

1) with enforced current splitting

2) UCC requires one motor-drive mechanism for each unit and istherefore not available in connection B and T.

Diverter Switch –Tap Selector Combinations

Diverter Switch UCG UCL UCC

Tap selector C, I, III III III, UCC

UCC diverter switch combined with tap selector III iscalled UCD.

The unit (diverter switch or tap selectors) with thelowest rating in any combination as per above,determines the type designation of the on-loadtap-changer.

1) Only tap selector III is available up to 21 positions withlinear switching.

13

Short versionUCG.E, T

Short versionUCG.N, E, T, B

UCG.E, TUCG.N, B

UCL.N, BUCL.E, T

Step voltage

Step voltage

Rated Phase Step Voltage

The maximum permitted step voltage is limited by theelectrical strength and the switching capacity of thediverter switch. The rated phase step voltage is a functionof the rated through current as shown in the diagramsbelow.

Fig. 12. Rated phase step voltage for type UCG

Fig. 14. Rated phase step voltage for type UCD Fig. 15. Rated phase step voltage for type UCC

Fig. 13. Rated phase step voltage for type UCL

Rated throughcurrent, A


15

00

A

10

50

A

12

00

A

70

0A

60

0A

50

0A

30

0A

90

0A

18

00

A

24

00

A

60

0A

90

0A

UCD.N

UCD.EStep voltage

3600A

2)


2) With enforced current splitting

18

00

A

12

00

A1

00

0A

20

00

A

30

00

A

24

00

A

UCC.NUCC.EStep voltage

Rated through current, A

12

00

A

16

00

A

36

00

A

80

0A

4500

A

Contact Life

The predicted contact life of the fixed and moving contactof the diverter switch, is shown as a function of the ratedthrough current in the diagrams below. It is based on thetype test with 50000 switching operations, and a currentcorresponding to the maximum rated through current. Thecontact life is stated on the rating plate.

14

Fig. 16. Contact life for type UCG

Fig. 19. Contact life for type UCC

Fig. 17. Contact life for type UCL


UCG. E, TUCG.N, B

Rated through current, A

12

00

A

60

0A

90

0A

50

0A

30

0A

Fig. 18. Contact life for type UCD

Rated through current, A1) R1 3000 without current splitting.2) R1 3600 with enforced current splitting.

70

0A

15

00

A

10

50

A

UCD. NUCD. E

10

00

A1

20

0A

18

00

A

3000A

1)

24

00

A

36

00

A2

)

Contact lifeNumber ofoperations


UCC. N

UCC. E

36

00

A

4500

A

80

0A

12

00

A

16

00

A


UCL. E, T

UCL. N, B


24

00

A

18

00

A

90

0A

60

0A


15

Fig. 22. Reversing switching:Contact designations in Tables 1-3

Reversing b1 and b2 are to theR corresponding contacts

in the next phase

Fig. 21. Linear switching:Contact designations in tables 1-31) See note 1 for UCC.

Fig. 23. Coarse/Fine switching:Contact designations in tables 1-3

Coarse/Fine b1, b2 and d1 are to theD corresponding contacts

in the next phase

Linear b1 and b2 are to theL corresponding contacts

in the next phase

Standards and Testing

The on-load tap-changers made by ABB Componentsfulfil the requirements according to IEC standards,publication 214.

The type tests include:

Contact temperature rise testSwitching testsShort-circuit current testTransition impedance testMechanical testsDielectric tests

The routine tests include:

Check of assemblyMechanical testSequence testAuxiliary circuits insulation testVacuum testFinal inspection

Rating Plate

Insulation Levels

The insulation levels are indicated as:

1.2/50 µs impulse withstand voltage (kV)–powerfrequency withstand voltage (kV).

The tests were carried out according to IEC 214 clause8.6. with a new on-load tap-changer and clean insula-tion oil class 2 according to IEC Publication 296. Thewithstand voltage value of the oil was higher than160 kV/cm.

Insulation Levels to Earth

For UCG 380–150 kV, 650–275 kV750–325 kV and 1050–460 kV.

For UCL 380–150 kV, 650–275 kVand 1050–460 kV.

For UCC and UCD 380–150 kV650–275 kV1050–460 kV.

Fig. 20. Example of Rating Plate

16

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0-1

60

55

0-1

80

11

13

15

42

0-1

50

48

0-1

60

35

0-1

40

35

0-1

40

50

0-1

60

55

0-1

80

17

35

0-1

40

40

0-1

50

30

0-1

25

30

0-1

25

18

R,

D9

49

0-1

60

55

0-1

80

40

0-1

50

40

0-1

50

60

0-2

00

60

0-2

00

50

0-1

60

55

0-1

80

60

0-2

00

60

0-2

00

11

13

42

0-1

50

48

0-1

60

50

0-1

60

15

35

0-1

40

40

0-1

50

35

0-1

40

17

-19

49

0-1

60

55

0-1

80

40

0-1

50

40

0-1

50

60

0-2

00

60

0-2

00

50

0-1

60

55

0-1

80

60

0-2

00

60

0-2

00

21

-23

25

-27

29

-31

42

0-1

50

48

0-1

60

35

0-1

40

35

0-1

40

50

0-1

60

50

0-1

60

33

-35

35

0-1

40

40

0-1

50

30

0-1

25

30

0-1

25

18

UCC

Table 3. Withstand Voltage within UCC on-load tap-changers

Within one phase Between phases for the neutral point type

Type of a2 a3 c1 e1, b2 b1 d1switching between ends of between any other across between open between open between open fixedand (fine) regulating electrically change-over contacts in fixed contacts in contacts in coarsenumber of winding non-adjacent taps selector diverter switch tap selector change-overpositions selector

US S US S US S US and S US S US S

L 9–23 300–125 300–1251) –– –– 200–80 300–125 – –9–15 500–170 500–170 500–170

R, D9–35 300–125 500–170 160–75 250–85 300–125 600–200 200–80 300–125 500–170 350–150 600–200

US = Unshielded contacts, S = Shielded contacts

1) For 17–23 positions, the withstand voltage between contacts on adjacent ribs is 180–100 kV.

NOTE: a1 Between electrically adjacent taps. The insulation withstands 200–80 kV.

Mechanical Life

The mechanical life is based on an endurance test whichshowed that the mechanical wear was negligible, andthat the on-load tap-changers were still mechanicallysound after one million operations.

Rated Through Current

The rated through-current of the on-load tap-changer isthe current which the on-load tap-changer is capable oftransferring from one tapping to the other at the relevantrated step voltage, and which can be carriedcontinuously whilst meeting the technical data in thisdocument. The rated through current is normally thesame as the highest tapping current.

The rated through-current is limited by the step voltageaccording to the curves in the diagrams, Fig. 12 toFig. 15.

The rated through-current determines the dimensioningof the transition resistors and the contact life.

The rated through-current is stated on the rating plate,Fig. 20.

Occasional Overloading

If the rated through-current of the tap-changer is not lessthan the highest value of tapping current of the tappedwinding of the transformer, the tap-changer will notrestrict the occasional overloading of the transformer,according to IEC 354 ”Loading guide for oil-immersedtransformers” (1991), ANSI/IEEE C57.92 ”Guide forloading mineral-oil-immersed power transformers” andCAN/CSA-C88-M90.

To meet these requirements, the UC models have beendesigned so that the contact temperature rise over thesurrounding oil does not exceed 20 K when loaded witha current of 1.2 times the maximum rated through cur-rent of the tap-changer.

The contact life stated on the rating plate is given withconsideration to that currents of maximum 1.5 times therated through current occur during a maximum of 3% ofthe tap-change operations. Overloading beyond thesevalues, results in increased contact wear and shortercontact life.

19

Short-circuit Current Strength

The short circuit current strength is verified with threeapplications of 2 seconds duration, without moving thecontacts between the three applications. Each appli-cation has an initial value of 2.5 times the rms value.

Type Max rated Three applications Reinforcedthrough of 2 secondscurrent, rms duration 1), rms

UCG 300 A 7.0 kA400 A 7.0 kA500 A, 600 A 7.0 kA700 A 7.0 kA900 A 9.0 kA

1050 A 10.5 kA1200 A, 1500 A 15.0 kA

UCL 600 A 9.0 kA900 A 9.0 kA

1800 A 26.0 kA2400 A 26.0 kA

UCD 1000 A 13.0 kA1200 A 12.0 kA1800 A 26.0 kA2000 A 24.0 kA2400 A 32.0 kA3000 A 36.0 kA

UCC 800 A 13.4 kA1200 A 13.4 kA1600 A 16.6 kA 21 kA3600 A 30.0 kA4500 A 36.0 kA 66 kA

1) With an initial peak current of 2.5 times the rms value andwithout moving the contacts between the three applications.

Table 4. Short-circuit current strength

Highest Phase Service Voltage Acrossthe Regulating Winding

The table below show the highest permissible phaseservice voltage, in kV, for the different types of con-nections.

Across the Across theregulating coarse and finewinding winding

Contact shieldings: with without with without

Tap-changer,connection

UCC.N 52 35 75 45UCD.N IIIUCL.NUCG.N III – –UCC.E 60 45 80 60UCD.E,UCL.T, E, BUCG.T, E, B III – –UCG.N C, I – 35 – 40UCG.T, E, B C, I – 35 – 45

Table 5. Highest permissible phase service voltageacross the regulating winding

Oil Temperature

The temperature of the oil surrounding the on-load tap-changer shall be between -25 and +105 oC for normaloperation, as illustrated below. The range can beextended to -40 oC provided that the viscosity is between2-800 mm2/s (=cst).

Tie-ln Resistor

If the service voltages and the winding capacitances aresuch that the potential of the tapped winding exceeds thevalues in table 6, it should be limited to this value bymeans of a tie-in resistor connected between the diverterswitch and the mid tap of the tap selector.

On-load tap-changer Voltage (kV)

UCG.. /C 35UCG.. /I 25UCG.. /III 35UCL.. /III 35UCD.. /III 35UCC.. 35

Table 6.

In order to eliminate the losses in the tie-in resistor, a tie-in resistor switch (S), which connects the resistor onlywhen the change-over selector is moving, can be addedto the bottom of the tap selector. The tie-in resistorswitch is not available for tap-selector C. The tie-inresistor is normally mounted separate from the on-loadtap-changer, but in some cases it can be mounted belowthe tap selector.

20

Fig. 25. Tie-in resistor connection

Design information on tie-in resistors is provided in aseparate document, On-Load Tap-Changer Tie-inResistors, 5492 0030E-28.

Fig. 24. On-load tap-changer oil temperature

1)

2)

3)

4)

5)

1) No operations allowed

2) Emergency overloading.The on-load tap-changer will notrestrict the occasional overloadingof the transformer accordingto the standards above.

3) Normal operating range

4) When operating within this range,no overload is allowed

5) Operation with de-energizedtransformer only

Design, Installation and MaintenanceOn-Load Tap-ChangerDesign Differences over the UC Rangeof On-Load Tap-Changers

The most obvious difference between the models in theUC range of on-load tap-changers is the size (seeFig. 26). Other differences are less obvious but includethe use of different materials in the manufacture of thetop sections (welded steel in the UCG and UCC/Dmodels, casted alloy in the UCL model). The cylinder isglued in the UCG range, and riveted in the rest of themodels.

Drying

The on-load tap-changer must be stored indoors and leftin its plastic shipping cover until time for assembly. Forfurther instructions refer to the Installation Guide.

Painting

The standard painting on the top section consists of aprimer of two-component epoxy type of max. thickness60 µm.The on-load tap-changer may be delivered in thisstate for finish coating by the customer, or it can bedelivered with a grey/blue finishing coat outside. Specialpainting will be quoted for on request.

21

There are also differences in the design and operation ofthe tap selector. For tap selectors sizes C and I, themoving contacts are driven by two parallel ribs in onecage. For tap selectors size III, the moving contacts aredriven by two concentric shafts. For UCC, the systemconsists of two cages with one driving shaft in each.

Fig. 26. On-load tap-changers type UC, size comparison

UCG.N/CUCG.N/I UCG.N/III UCL.N/III UCD.N/III UCC.N650 kV 650 kV 650 kV 650 kV 650 kV

22

Weights

The tables below shows all the weights of the UC rangeof on-load tap-changers.

On-load tap-changer Approximately weight in kgType designation Tap-changer Required Total

without oil 1) oil

UCL.N 380/600, 900 480 260 740650/600, 900 500 300 8001050/600, 900 510 340 850

UCL.T 380/600, 900 1230 3x260 2010380/1800 1350 3x260 2130380/2400 1440 3x260 2220650/600, 900 1290 3x300 2190650/1800 1410 3x300 2310650/2400 1500 3x300 24001050/600, 900 1320 3x340 23401050/1800 1440 3x340 24601050/2400 1530 3x340 2550

UCL.B 380/600, 900 850 2x260 1370650/600, 900 890 2x300 14901050/600, 900 910 2x340 1590

UCL.E 380/600, 900 410 260 670380/1800 450 260 710380/2400 480 260 740650/600, 900 430 300 730650/1800 470 300 770650/2400 500 300 8001050/600, 900 440 340 7801050/1800 480 340 8201050/2400 510 340 850

1) The weight of the diverter switch, approximately 120 kg, isincluded.

Table 8. Weights for type UCL

On-load tap-changer Approximately weight in kgType Designation Tap-changer Required Total

without oil 1) oil

UCG.N 380-750/300-600 425 150 5751050/300-600 435 185 620

UCG.T 380-750/300-900 1025 3x150 1475380-750/1050-1500 1190 3x150 16401050/300-900 1090 3x185 16451050/1050-1500 1225 3x185 1780

UCG.B 380-750/300-600 760 2x150 10601050/300-600 780 2x185 1150

UCG.E 380-750/300-900 360 150 510380-750/1050-1500 410 150 5601050/300-900 370 185 5551050/1050-1500 425 185 610


Table 7. Weights for type UCG

On-load tap-changer Approximately weight in kgType designation Tap-changer Required Total

without oil 1) oil

UCD.N 380/1000 950 710 1660650/1000 980 790 17701050/1000 1010 910 1920

UCD.E 380/1000 890 710 1600380/1800 920 710 1630380/2400 950 710 1660650/1000 920 790 1710650/1800 950 790 1740650/2400 980 790 17701050/1000 950 910 18601050/1800 980 910 18901050/2400 1010 910 1920


Table 9. Weights for type UCD

On-load tap-changer Approximately weight in kgtype designation Tap-changer Required Total

without oil 1) oil

UCC.N 380/800, 1200 1130 710 1840380/1600 1220 710 1930650/800, 1200 1160 790 1950650/1600 1250 790 20401050/800, 1200 1190 910 21001050/1600 1280 910 2190

UCC.E 380/3600 1130 710 1840380/4500 1220 710 1930650/3600 1160 790 1950650/4500 1250 790 20401050/3600 1190 910 21001050/4500 1280 910 2190


Table 10. Weights for type UCC

Oil Filling

For details of oil filling, consult the appropriate Installa-tion Guide.

Installation

The on-load tap-changers can be delivered for cover-mounting method or yoke-mounting method onto thetransformer.

For detailed installation instructions, consult the appro-priate Installation Guide.

Maintenance

The UC range of on-load tap-changers have beendeveloped over many years to provide a maximum ofreliability. The simple and rugged design gives a servicelife that equals the service life of the transformer. Aminimum of maintenance is required for absolutelytrouble-free operation. The only parts that requiremaintenance during the service life are the diverterswitch contacts that may need to be replaced, and themotor-drive mechanism. The oil in the diverter switchhousing has also to be cleaned with certain intervals.

Maintenance is easy to carry out since the designprovides for quick and easy access and inspection. Foroverhaul, the top cover is removed and, if necessary, thediverter switch can be lifted out without furtherdismantling.

An annual inspection should be carried out to read thecounting device. These readings are used to determinewhen overhaul is due. Overhaul shall normally becarried out every seven years, and consists of checkingthe dielectric strength, filtering the oil, and checking thecontacts (and replace them if they are worn). The motor-drive mechanism should also be checked and lubricated,and the pressure relay checked.

The appropriate Maintenance Guide should be consultedif you need further information.

Oil Filter Unit

The on-load tap-changer can be equipped with an oilfilter unit for continuous oil filtration. For furtherinformation, see manual 1ZSE 5492-152.

Pressure Relay

General Description

Protection for the on-load tap-changer is provided by apressure relay which is mounted on the on-load tap-changer top section. In the event of an over-pressure inthe tank, the relay will, if correctly connected, trip thetransformers main circuit breakers. After a pressure relaytrip, the on-load tap-changer must be carefullyinvestigated. Faults, if any are located, should berepaired before the transformer is energized.

23

The pressure relay is mounted on a three-way valve. Onthe other two outlets of the valve there is a connectionflange on one side, and a connection for test equipmenton the other.

The relay is made of copper-free aluminium alloy and isexternally coated with an enamel. A stainless steel modelcan be provided on request.

The pressure relay has been pre-set by the manu-facturer. The pressure relay is sealed to avoidunauthorized entrance. The electrical connection shall bemade to the terminal box mounted onto the pressurerelay.

Operation

When the pressure acting on the face of the pistonexceeds the spring load of the piston, the piston willmove and activate the switching element.

The operation time is less than 10 ms. The operationtime is the time it takes from the pressure in the tap-changer tank exceeds the function pressure, until thepressure relay gives a stable signal for operation of thetransformer main switch.

The function pressure (trip pressure) is shown intable 11.

H 1) Function pressure(trip pressure)

< 7 m 100 kPa (14.5 Psi)7 – 20 m 100-230 kPa (14.5-33.5 Psi) 2)

1) The height (H) is the distance between the level of the pressurerelay and the oil level in the oil conservator.

2) Option when H is 7-20 m.

Table 11. Function pressure (trip pressure)

Testing

Before the commissioning of the transformer and fortesting the pressure relay, reference should be made tothe specific instructions regarding the pressure relay, orto the appropriate Installation Guide.

Installation

The pressure relay is to be mounted directly on to the on-load tap-changer tank, using the flange and fittingsprovided. Caution should be used when handling therelay to avoid damage. The relay should be stored in itsprotective box until attaching to the on-load tap-changer.

Caution should also be applied when attaching the relayto the on-load tap-changer tank, and the appropriateInstallation Guide should be consulted.

Piston

Switching contact

Connection fortest equipment

Adjusting nut

Spring

One single-poleswitching contact

Two single-poleswitching contacts

NO NC C NO NC C64 66 65 61 63 62

NO NC C61 63 62

24

Fig. 28. Positioning of motor-drive mechanism

Operating shafts

Length L1 L2 L3 and L4 Motor-drivemm mm mm mechanism

Min/max 500/3100 525/3100 900/2700 BUE500/3100 600/3100 – BUL

The minimum and maximum lengths refer to mechanicaldesign only. See Fig 28. L2 vertical shaft see followingpages. Also other shaft arrangements on request.

Fig. 27. Pressure relay

Motor-Drive MechanismDesign

For detailed design description, see separate TechnicalGuides for Motor Drive Mechanisms types BUL or BUE,respectively.

Installation

The motor-drive mechanism is fitted to the outside of thetransformer tank, and connected to the on-load tap-changer by drive shafts and bevel gears.

For the correct installation procedure, consult theappropriate Installation Guide.

Maintenance

The motor-drive mechanism should be inspected atregular intervals and at the same time as the on-loadtap-changer is inspected.

For the correct inspection and maintenance procedures,consult the appropriate Maintenance Guide.

��

ABB Components

30 54 67

Cable gland~200~35

110

~155

15

32

11

DimensionsType UCG/C

Dimensions in mm. The design, technical data anddimensions are subject to alteration without notice.

Section A – ALinear switching

Section A – APlus/Minus andCoarse/Fineswitching

145

(BUE1) 233(BUE2) 353

80

230

134

(BUE1) 320(BUE2) 440

C/L Tap selector C/L Diverter switch

R210

570

570

615D=420

615

R210

(BUE1) 592(BUE2) 818

194

36

75

157

L2

290

L1H32)

H1

A A

205

D=600

D=470

345

390

30

H2

70

405

1)

1)

D=420

332

D=740

25


For tap Impulse with- H1 H1, H3 H3selector stand voltage short shortsize to earth version version

kV mm mm mm mm

C 380, 650, 750 1192 972 1400 12001050 1492 1272 1700 1500

Fig. 29. Dimensions, type UCG

Tap selector

For on-load Max rated H2, size Ctap-changer through currenttype A mm

UCG.N 400 959

UCG.E, UCG.T 3) 400 519700 739

1 050 959

UCG.B 4) 400 Single-phase unit519

Two-phase unit739

1) Shielding-rings are used only for insulation level650-275 kV and higher.

2) Space required for lifting the diverter switch, excludingthe lifting equipment.

3) UCG.T consists of three single-phase units.

4) UCG.B consists of one single-phase and one two-phaseunit arranged as shown in the dimension drawing forUCL.B (page 29).

111

16O

26

DimensionsType UCG/I




3) Dimension without shielding-ring.

4) For tie-in resistor switch add 360 mm.





36

1)

610

19475

157

L2

L1

H1

H2

405

D=600

D=470

1)

1)

30

6053)

665

3903)

500

500 4103)

4203) 530

332

290

390

145

(BUE1) 233(BUE2) 353

(BUE1) 592(BUE2) 818

23016O

80

(BUE1) 320(BUE2) 440

4)

70

30

195

H32)

185

D=740

134

AA

111

27

Type UCG/III


Operating shaftsThe minimum and maximum lengths refer to mechanicaldesign only.


Min/max 500/3100 525/3100 900/2700 BUE500/3100 600/3100 – BUL

L3 and L4 for UCG.T, see Fig. 28, page 24.


For tap Impulse with- H1 H1, H3 H3selector stand voltage short shortsize to earth version version

kV mm mm mm mm

I 380, 650, 750 1317 1097 1400 12001050 1617 1397 1700 1500

III 380, 650, 750 1354 1134 1400 12001050 1654 1434 1700 1500

Tap selector

For on-load Max. rated H2 H2tap-changer through current size I size IIItype A mm mm

UCG.N 300–600 1030 1160

UCG.E, UCG.T 5) 300–600 530 552900 – 552

1200 760 8561500 1030 856

UCG.B 6) 300–600 single- single-phase phase

unit unit532 552

two- two-phase phase

unit unit774 856

5) UCG.T consists of three single-phase units.6) UCG.B consists of one single-phase and one two-phase

unit arranged as shown in the dimension drawing forUCL.B (page 29).

Section B - BLinear switching


Section B - BPlus/Minus andCoarse/Fine switching

Model for mounting ontransformer’s active part

Model for cover mounting

30385

5904903)

8403)

295

940

4903)

4903) 580

H2

H1

BB

78

2553)

H1+106

580

28

Type UCL.N (three-phase, star point) andtype UCL.E (single-phase)


Impulse withstand H1 H3voltage to earth

kV mm mm

380 1415 1500650 1615 1700

1050 1815 19005) For mounting on

active part H1+85 H3+100

Fig. 32. Dimensions, type UCL



DimensionsType UCL/III


29

Type UCL.B (three-phase, delta)

Tap selector

For on-load Max rated H2tap-changer through current size IIItype A mm

UCL.N 600–900 1160

UCL.E, UCL.T 6) 600–900 5521800 8562400 1160

UCL.B 7) 600–900 single-phaseunit

H22 = 552

two-phaseunit

H21 = 856




4) For-tie in resistor switch add 370 mm

5) Model for mounting on transformers active part.

6) UCL.T consists of three single-phase units.

7) UCL.B consists of one single-phase and one two-phaseunit.



Min/max 500/3100 525/3100 900/2700 BUE500/3100 600/3100 – BUL

L3 and L4 for UCL.T, see Fig. 28, page 24.

Design for premountingon the active part of thetransformer

DimensionsType UCD/III


Fig. 33. Dimensions, type UCD

30

31


Length L1 L2mm mm

Min/max 500/3100 525/3100




4) For tie-in resistor switch, add 370 mm.

5) When two or three units are fitted together (three-phasedelta and three-phase fully isolated respectively) thedistance between the units (c) must be at least 1340 mmfrom mechanical point of view. For final dimensioning,check the insulation distance required.



kV mm mm

380 1594 1600650 1734 1750

1050 1934 1950

Tap selector

For on-load Max rated H2tap-changer through current size IIItype A mm

UCD.N 1000 1160

UCD.E 1000 5521800 8562400 1160

Fig. 34. Dimensions, type UCC

32

DimensionsType UCC


33




4) For tie-in resistor switch add 340 mm.

5) When two or three units are fitted together (three-phasedelta and three-phase fully isolated respectively) thedistance between the units (c) must be at least 1340 mmfrom mechanical point of view. For final dimensioning,check the insulation distance required.



kV mm mm

380 1540 1600650 1680 1750

1050 1880 1950

Tap selector

For on-load Max rated H2tap-changer through currenttype A mm

UCC.N 800, 1200 12901600 1530

UCC.E 3600 12904500 1530


Length L1 L2mm mm

Min/max 500/3100 525/3100

Appendices: Single-Phase DiagramsThe tap-changer can also be connected in such a waythat position 1 gives a minimum effective number ofturns in the transformer winding with the tap-changer inposition 1.

The connection diagrams can be downloaded from ourwebsite: www.abb.se/com/

The basic connection diagrams illustrate the differenttypes of switching and the appropriate connections to thetransformer windings. The diagrams illustrate theconnections with the maximum number of turns in thetransformer winding, with the tap-changer in position 1.

34

10 Steps

Appendix 1: Single-Phase Diagrams for UCG/C

Linear Plus/Minus Coarse/Fine 8 Steps

Linear Plus/Minus Coarse/Fine

12 Steps

14 Steps

18 Steps

35

16 Steps


20 Steps

22 Steps

26 Steps

24 Steps

36

37

Appendix 2: Single-Phase Diagrams for UCG/I


8 Steps

10 Steps

12 Steps

14 Steps


16 Steps

20 Steps

18 Steps

22 Steps

38

28 Steps

30 Steps

39

26 Steps


24 Steps


32 Steps

34 Steps

40


8 Steps

12 Steps

10 Steps

14 Steps

41

Appendix 3: Single-Phase Diagrams for UCG/III, UCL/III andUCD/III


16 Steps

20 Steps

22 Steps

42

17 Steps 18 Steps 18 Steps


24 Steps

28 Steps

30 Steps

43

26 Steps


32 Steps

44

34 Steps


8 Steps

12 Steps

14 Steps

45

10 Steps

Appendix 4: Single-Phase Diagrams for UCC


16 Steps

20 Steps

22 Steps

46

18 Steps


24 Steps

28 Steps

30 Steps

47

26 Steps

48


32 Steps

34 Steps

Notes:

_

_

1ZS

E 5

492-

105

en,

Rev

. 5, 2

000-

11-1

5

Printed in Sweden by Globe, Ludvika, 2000

ABB Components ABVisiting address: Lyviksvägen 10Postal address: SE-771 80 Ludvika, SWEDENTel.+46 240 78 20 00Fax +46 240 121 57E-mail: [email protected]/transmission

!zse 5492-105 en, rev. 5...the bevel gear, mounted on the top section flange transfers the drive...

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