oltc ucg_vucg 1zse 5492-105 technical guide

8/10/2019 OLTC UCG_VUCG 1ZSE 5492-105 Technical Guide

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1ZSE 5492-105 en, Rev. 7

On-load tap-changers, type UC and VUCTechnical guide


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This Technical Guide has been produced to allow transformer manufacturers, and theirdesigners and engineers, access to all the technical information required to assist them in

their selection of the appropriate on-load tap-changer and motor-drive mechanism.

The technical information pertaining to on-load tap-changers and motor-drive mecha-nisms manufactured by ABB 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 coverall possible applications. Any specific application not covered should be referred directlyto the supplier, or its authorized representative.

ABB makes no warranty or representation and assumes no liability for the accuracy ofthe information in this document or for the use of such information. All information in thisdocument is subject to change without notice.

Manufacturers declaration

The manufacturer ABB AB

Components

SE-771 80 LUDVIKA

Sweden

Hereby declares that

The products On-load tap-changers, type UC and VUC

with motor-drive mechanisms, types BUE and BUL

comply with the following requirements:

By design, the machine, considered as component on a mineral oil lled power transformer, complies

with the requirements of

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

ing) provided that the installation and the electrical connection be correctly realized by the manu-

facturer 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 (modied by Directive 93/68/EEC) concerning the built-in motor

and apparatus in the control circuits.

Certicate 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 2008-03-15

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

Folke Johansson

Title Manager of Division for Tap-Changers


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31ZSE 5492-105 en, Rev. 7

ContentsGeneral information ..................................................................... 5

Design principles ......................................................................... 8On-load tap-changer ...................................................................................8

Diverter switches .........................................................................................8Conventional diverter switch...................................................................8Diverter switch with vacuum interrupters ................................................ 8Tap selector ............................................................................................ 10Design differences over the UC range of on-load tap-changers ............10Diverter switch housing and top section ................................................12

Painting .............................................................................................12Operating mechanism ............................................................................12Transition resistors .................................................................................13Special applications, load conditions and environments ........................13Special designs .....................................................................................13On-line oil filtration (for diverter switch with arc quenching in oil only) ...13

Motor-drive mechanism ............................................................................... 14Type BUE ...............................................................................................14Type BUL ................................................................................................14

Accessories .................................................................................................14

Tap-changer principles of operation ............................................ 15Switching sequence, UC ............................................................................ 15Switching sequence, VUCG ........................................................................16Type of regulation ........................................................................................ 18

Linear switching (type L) ....................................................................... 18Change-over selector for plus/minus switching (type R) ........................18Change-over selector for coarse/fine switching (type D) .......................18

Type of connection ......................................................................................19

Three-phase star point (N) .....................................................................19Single-phase (E).....................................................................................19Three-phase delta (B) ............................................................................19Three-phase delta fully insulated (T) ......................................................19Auto transformer (T) ...............................................................................19

Tap-changer characteristics and technical data .......................... 20Type designation .........................................................................................20

Maximum number of positions ...............................................................21Diverter switches .........................................................................................21Tap selectors ...............................................................................................22

Possible combinations of diverter switches and tap selectors ................22Enforced current splitting ............................................................................. 22

In position ...............................................................................................22During operation .....................................................................................23

Rated phase step voltage ............................................................................ 24Coarse fine regulation leakage inductance switching ............................26

Contact life ...................................................................................................26Standards and testing .................................................................................28Rating plate .................................................................................................28Insulation levels ...........................................................................................28Withstand voltages ......................................................................................31

UCG and VUCG with tap selector C.......................................................31UCG and VUCG with tap selector I ........................................................31UCG and VUCG with tap selector III unshielded version .......................32

UCG and VUCG with tap selector III shielded version ...........................32


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UCL with tap selector III unshielded version ..........................................33UCL with tap selector III shielded version ..............................................33UCD with tap selector III unshielded version .......................................... 34UCD with tap selector III shielded version .............................................. 34UCC with tap selector IV ........................................................................35

Short-circuit current strength .......................................................................36

Highest phase service voltage across the regulating winding ....................37Rated through-current .................................................................................37Occasional overloading ...............................................................................37Oil temperature ............................................................................................38Coarse/fine regulation leakage inductance switching ..................................39Tie-in resistor and tie-in resistor switch .......................................................40

Installation and maintenance ....................................................... 42On-load tap-changer ...................................................................................42

Installation ..............................................................................................42Drying .....................................................................................................42Weights ..................................................................................................42Oil filling .................................................................................................44Maintenance ...........................................................................................45Pressure .................................................................................................45

Accessories and protection devices ............................................................45Motor-drive mechanism ............................................................................... 46

Design ....................................................................................................46Installation ..............................................................................................46Maintenance ...........................................................................................46Operating shafts .....................................................................................46

Dimensions ..................................................................................................48Type UCG/C and VUCG/C ..................................................................... 48Type UCG/I and VUCG/I ......................................................................... 49Type UCG/III and VUCG/III.....................................................................50

Type UCL/III ............................................................................................52Type UCD/III ........................................................................................... 55Type UCC/IV ...........................................................................................57Oil conservator .......................................................................................59

Appendices: Single-Phase Diagrams .......................................... 60Appendix 1: Single-phase diagrams for UCG/C .....................................60Appendix 2: Single-phase diagrams for UCG/I ....................................... 65Appendix 3: Single-phase diagrams for UCG/III, VUCG/III, UCL/IIIand UCD/III.............................................................................................72Appendix 4: Single-phase diagrams for UCC/IV.....................................79


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General informationWhen the on-load tap-changer operates, the insulating oil will be contam-inated. To avoid contamination of the transformer oil, the diverter switchhas its own housing separate from the rest of the transformer. The tapselector, which is mounted beneath the diverter switch housing, consists

of the fine tap selector and usually also of a change-over selector. Theoperating principle for the UC and VUC range of on-load tap-changers iscalled the diverter switch principle.

The UC types of on-load tap-changers are usually mounted inside of thetransformer tank, suspended from the transformer cover. Power to oper-ate the on-load tap-changer is supplied from the motor-drive mechanism,which is mounted on the outside of the transformer. The power is trans-mitted by means of shafts and bevel gears.

The UC types of on-load tap-changers come in a wide range of modelswith a rating suitable for every application.

Transformer cover

On-load tap-changer

Oil conservator

Motor-drive mechanism

Shaft

Bevel gear

Shaft

Transformer tank

Fig. 1. Main parts, on-load tap-changers types UC and VUC.

Diverter switch

Tap selector


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6 1ZSE 5492-105 en, Rev. 7

Cover

Lifting eye

Top section

Shielding-ring

Current terminal

Bottom section

Valve for use atprocessing

Connections fromthe tap selector

Plug-in contacts

Insulatingcylinder

Diverter switch

Oil draining tube

Flange for connectionto gas operated relay

Intermediate gear

Driving disc for thediverter switch

Locating pins

Fixed and movingcontacts

Transition resistors

Shielding-ring

Insulating shaft

Bevel gear withposition indicator

Buffer springs

Diverter switch housing

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


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Vacuum interrupters


Spring drivemechanism

Plug-in contacts

Fig. 3. On-load tap-changer type VUCG.


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Design principles

On-load tap-changerWhen the on-load tap changer operates, the oil is contaminated. UC with

conventional arc quenching in oil contaminates the oil heavily while VUCwith arc quenching in vacuum interrupters only contaminates slightly dueto current commutation sparks and heat dissipation from the transitionresistors. To avoid contamination of the transformer oil the on-load tap-changer is built in two separate sections, the diverter switch, which hasits own housing, and the tap selector. The tap selector is mounted belowthe diverter switch housing and the complete unit is suspended from thetransformer cover.

VUC and UC are of the diverter switch type. UC works according to theflag cycle principle and VUC works according to the unidirectional pen-nant cycle principle.

Diverter switchesTwo different types of diverter switches are available, the conventionaltype with arc quenching in oil and the new type with vacuum interrupters.

The diverter switches are equipped with plug-in contacts that automati-cally connect it to the bushings in the diverter switch housing when theswitch is lowered into the housing. Guiding facilities keep the diverterswitch in correct position when lowering it into the housing. Mechanicalcoupling to the motor-drive mechanism is automatically established whenthe driving pin enters the slot in the driving disc.

The design and dimensioning of the diverter switches offer high reliability

and long life with a minimum of maintenance and easy inspection.

Conventional diverter switch

The diverter switch is of the high-speed, spring-operated type with resis-tors as transition impedance.

The diverter switch is designed as a system of moving and fixed contacts.Movement of the moving contact system is controlled by a self-lockingpolygon link system with a set of helical springs. The link system is robustand has been carefully tested. The fixed contacts are placed on the sidesof the diverter switch, which are made of insulated board.

The current-carrying contacts are made of copper or copper and silver,

and the breaking contacts of copper-tungsten.

Diverter switch with vacuum interrupters

Combines all the advantages of the conventional type with improvedbreaking capacity, increased contact life and reduced maintenance.

It works according to the unidirectional pennant cycle, which gives thelowest complexity. A mechanical rectifier ensures operation in only thedirection that gives the lowest breaking stresses and contact wear.


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Fig. 4. Examples of diverter switches UCG and VUCG.

The load is commutated from one tap to the other by aid of the vacuuminterrupters and auxiliary contacts. The auxiliary contacts are also able tobreak the load current in the unlikely event of a vacuum interrupter failureshould occur.

In service position the current is transferred through the auxiliary contacts

and the vacuum interrupters. All current carrying contacts are made oflow resistance material.

The vacuum interrupters have a very long life time but yet mounted foreasy replacement when needed, for instance in industrial applicationswhen the number of operations might be extremely high.

The contact system is powered by a compact mechanical system withintegrated driving springs, mechanical rectifier, robust mechanical sys-tem for vacuum interrupter actuating and geneva gears for operating theauxiliary contacts.

All manufactured conventional UCGs can be easily replaced by thevacuum diverter switch and gain benefit of the improvements made on

this type.


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Tap selector

Although the tap selector for the UC range of on-load tap-changer isavailable in various sizes, all have similar functions with different ratings.

The fixed contacts are mounted around the central shafts. The movingcontacts are mounted on, and are operated by, the shafts in the center ofthe selector. The moving contacts are connected, via current collectors, tothe diverter switch by means of paper insulated copper conductors.

Depending on the load current, the moving contacts have either one,two, or more contact arms in parallel with one, two or four contact fingerseach. The fingers make contact at one end with the fixed contact, andat the other with the current collector. The moving contacts slide on thefixed contacts and the current collector rings, giving a wiping action whichmakes the contacts self cleaning. This arrangement promotes good con-ductivity and negligible contact wear.

Fig. 5. Tap selectors: size C and size III.

Design differences over the UC range of on-load tap-changers

The UC range of tap-changers consists of five diverter switches and fourtap selectors.

The diverter switches, from the smallest to the biggest type, are UCG,VUCG, UCL, UCD and UCC. VUCG has arc quencing in vacuum, all oth-ers have arc quencing in oil.

The VUCG diverter switch fits without modification in all UCG tap-chang-ers as manufactured 1977 and later, which enables all UCG tap-changersto be easily upgraded to vacuum technology.


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L (m)

3

2

1

UCG.N/C

VUCG.N/C

UCG.N/I

VUCG.N/I

650 kV

UCG.N/III

VUCG.N/III

650 kV

UCL.N/III

650 kV

UCD.N/III

650 kV

UCC.N

650 kV

Fig. 6. On-load tap-changers type UC, size comparison.

The tap selectors, from the smallest to the biggest type, are C, I, III andIV. Tap selectors I and C can be combined with UCG and VUCG diverterswitches. Tap selector III can be combined with all diverter switches ex-cept UCC. Tap selector IV can be combined with UCC only.

For correct selection, use this Technical Guide or the ABB selection pro-

gram Compas.UCG is available in two versions (standard and short) and manages 200 300 MVA star connected transformers and up to approximately 500MVA Auto transformers.

UCL manages star connected transformers up to 500-600 MVA and Autotransformers up to 1000 MVA.

UCD and UCC manages star connected transformers >600 MVA and>1000 MVA respectively. For winding connections where three single-phase tap-changers are needed, each single phase of the UCD and UCCmust have it-s own motor-drive mechanism.

In tap selectors I and IV the fixed contacts are mounted on insulating

bars, whereas the C and III types use a complete, un-divided glass fibrereinforced epoxi cylinder.


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Diverter switch housing and top section

The top section forms the flange that is used for mounting to the trans-former cover, and for carrying the gear box for the operating shafts. Thetop section includes a connection for the conservator pipe, draining andfiltering connections, an earthing terminal, the supervisory device, and

the cover with its gasket. The top section is available in two designs, onefor cover mounting and one for pre-mounting (yoke-mounting) on thetransformers active part.

The diverter switch housings have high quality sealings that guaranteevacuum and overpressure-proof performance under all service condi-tions. In case of material ageing after extremely long service the sealingscan be re-tightened.

The bottoms and heads of the cylinders are made of cast aluminium.

The driving shafts and bevel gears are placed beside the diverter switchcylinders, thereby providing easy access to the diverter switches.

The bottom section has locating holes for the diverter switch, bearings,brackets for the tap selector mounting and the current terminal for thediverter switch. There is also a draining valve in the bottom which shouldonly be opened during the drying process of the transformer.

The top and bottom sections are fixed to a cylinder of glassfibre rein-forced plastic. The bushings through the cylinder wall are sealed by O-ring gaskets with elastic pressure. Each ready-made unit is tested undervacuum and the outside is exposed to helium and checked for leaks withthe use of a helium gas detector.

Painting

The diverter switch housing top sections are finish coated with a blue-

grey colour, Munsell 5,5 B 5,5/1,25, corrosion class C3 acc. to SS-ENISO 12944-2. For the motor drives, the painting can be chosen betweenprimary coating corrosion class C3 or finish coated with a blue-greycolour, Munsell 5,5 B 5,5/1,25, corrosion class C3 acc. to SS-EN ISO12944-2.

Operating mechanism

The bevel gear, mounted on the top section flange transfers the drivefrom the motor-drive mechanism, via the vertical shaft, to the intermedi-ate gear for the diverter switch and the tap selector.

From the intermediate gear, a drive shaft transfers the energy to the di-verter switch through an oil tight gland in the bottom of the diverter switch

housing. When the diverter switch is lowered into the housing (afterinspection), the drive is automatically re-connected by a system that en-sures that the drive shaft and the locating pin of the diverter mechanismis correctly aligned.

The intermediate gear also drives the geneva gear of the tap selector, viaa free wheel connection. The geneva gear provides alternate movementto the two vertical shafts of the tap selector.

The external drive shaft, that does not need to be removed during main-tenance work, minimizes the risk for misalignment in the system. Howevera mechanical end limit stop for the tap selector is available on request.

Special shaft systems are also available on request.


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The transition resistors are made of wire and located above the diverterswitch contacts. The resistors are robust and designed to withstand thelifetime of the mechanism under normal service conditions.

Special applications, load conditions and environmentsPlease contact the supplier for advisory in the following cases:

For special applications such as:

Arc furnace

HVDC

Rectifiers

Shunt reactors

Series reactors

Phase shifters

Traction

Industrial applications in general

OLTCs working in parallel

In case of unusual load conditions such as overloads beyond IEC60076-7, IEC 60354 or IEEE C57.131-1995, extreme inductive orcapacitive loads or loads beyond the given data in this document.

In case of service in extreme environments such as very high humid-ity, very high or low temperatures, indoors, etc.

Special designs

On request, the UC and VUC tap-changers are also available for regula-

tion with bias winding and for Y/D regulation.

On-line oil filtration (for diverter switch with arc quenching in oil only)

On-line oil filtration is not required in any application and does not extendlifetime of contacts, but can give benefits for OLTCs with arc quenching inoil in certain applications such as:

Arc furnace applications (prolongs mechanical life and maintenanceinterval and shortens maintenance time)

High voltage line end applications (maintains the high dielectric with-stand of the insulating liquid)

Whenever short outage time is important when carrying outmaintenance

At any application with a high number of operations or high dielectricstresses.

The on-line oil filtration works with continuous low flow filtration givingthe best filtration result, less risk of gas bubbles and requires less con-trol equipment. Filter cartridges are easily replaced without taking thetransformer out of service. For further information about the oil filter, seemanual 1ZSC000562-AAA.

The filtration reduces the number of particles and keeps the water level ata dielectric safe level.

-

-

-

-

-

-

-

-

-


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Motor-drive mechanismThe motor-drive mechanism provides the drive to allow the on-load tap-changer to operate. Energy is provided from a motor through a series ofgears and out through a drive shaft. Several features are incorporatedwithin the mechanism to promote long service intervals and reliability.

There are two sizes of motor-drive mechanisms that can be used. If thereare any doubts about which type to select, please consult the supplier.

Type BUE

The BUE is for all on-load tap-changers types UC and VUC.For detailed operation descrip-tion, see Technical Guide forMotor-Drive Mechanisms typeBUE.

Fig. 7a. Motor-drive mechanism

type BUE

Type BUL

The BUL is for on-load tap-changers types UCG, VUCGand UCL at star point orsingle-phase applications.

However, when extra spaceis required for optional acces-sories the type BUE mighthave to be selected due tolimited space in the BUL. Fordetailed operation descrip-tion, see Technical Guidefor Motor-Drive Mechanismstype BUL.

Fig. 7b. Motor-drive mechanism type BUL

AccessoriesFor a list of accessories available for both the on-load tap-changers andthe motor-drive mechanisms, consult the supplier.


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Tap-changer principles of operation

Switching sequence, UCThe switching sequence of the on-load tap-changer from position 6 to

position 5, is shown in the figures below.

The sequence is designated the symmetrical flag cycle. This means thatthe main switching contact of the diverter switch, breaks before the transi-tion resistors are connected across the the regulating step. This ensuresmaximum reliability when the switch operates with overloads.

At rated load the breaking takes place at the first current zero after con-tact separation, which means an average arcing time of approximately4-6 ms. The total time for a complete sequence is approximately 50 mil-liseconds. The tap change operation time of the motor-drive mechanismis approximately 5 s/step. (10 s for through-positions.)

Fig 8a. Position 6

Selector contact V con-nects tap 6 and selectorcontact H on tap 7. Themain contact x carriesthe load current.

Fig. 8b

Selector contact H hasmoved in the no-loadstate from tap 7 to tap 5.

Fig. 8c

The main contact x hasopened. The load cur-rent passes throughthe resistor Ry and theresistor contact y.

Fig. 8d

The resistor contact uhas closed. The loadcurrent is shared be-tween Ry and Ru. Thecirculating current islimited by the resistanceof Ry plus Ru.

Fig. 8e

The resistor contact yhas opened. The loadcurrent passes throughRu and contact u.

Fig. 8f. Position 5

The main contact v hasclosed, resistor Ru isbypassed and the loadcurrent passes throughthe main contact v. Theon-load tap-changer isnow in position 5.


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MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

Switching sequence, VUCGBy using an auxiliary contact system (MC, RC) in combination with thevacuum interrupters (MVI, RVI) only two vacuum interrupters are requiredper phase.

Fig. 9a shows the current path during normal operation, from x to the starpoint (could also be to the next phase). When commuting the load from xto v, the first part of the operation sequence is to open the main vacuuminterrupter (MVI) and hence let the current flow through the transitionresistor (TR), Fig. 9b. The main contact (MC) is then rotated (Figs. 9c and9d) in order to connect to v. The main vacuum interrupter then closes,leading to an associated circulating current driven by the difference involtage potential, Fig. 9e. In Fig. 9f, the transition resistor is disconnectedwhen opening the resistor vacuum interrupters (RVI). The load current isnow via the normal path from v to the star point. The resistor contact (RC)is then rotated and put in position according to Fig. 9g. Finally, the se-quence is completed and next service position is reached when the resis-tor vacuum interrupter is closed, see Fig. 9h.

Fig. 9a.

Fig. 9b.

Fig. 9c.


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MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

MVI

MC

RVITR

RC

x

v

Fig. 9d.

Fig. 9e.

Fig. 9f.

Fig. 9g.

Fig. 9h.


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Change-over selector for plus/minus switching (type R)

The change-over selector extendsthe regulating range to twice the

voltage of the tapped winding, byconnecting the main winding todifferent ends of the regulatingwinding.

Fig. 11

Change-over selector for coarse/fine switching (type D)

In type D switching the change-over selector extends the regu-lating range to twice the voltageof the tapped winding, by con-necting or disconnecting thecoarse regulating winding.

Fig. 12

ReversingChange-over selector

Change-over selector,coarse/fine

Type of regulation

Linear switching (type L)

The regulating range is equal to thevoltage of the tapped winding. No

change-over selector is used.

Fig. 10


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191ZSE 5492-105 en, Rev. 7

Type of connection

Three-phase star point (N)

Only one unit is required for all threephases. The transformers neutral

point is in the OLTC.

Single-phase (E)

Only one unit is required

Three-phase delta (B)

Two units required. Driven by a com-mon motor-drive. One unit commonfor two phases.

Three-phase delta fully insulated (T)

Three units required. Driven by acommon motor-drive.

Auto transformer (T)

Several configurations of auto trans-formers exist. This example showsthe tap-changer in auto-tap.


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Tap-changer characteristics and technical data

Type designation

UC... Diverter switch with arc quenching in oil

VUC... Diverter switch with vacuum interrupters

Example UCGRE 650/700/C

Type of tap-changer

UC... Diverter switch with arc quenching in oil

VUC... Diverter switch with vacuum interrupters

Type of switching

L Linear

R Plus/Minus

D Coarse/Fine

Type of connection

N 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 earth

UCG, VUCG: 380 kV, 650 kV, 750 kV, 1050 kVUCL: 380 kV, 650 kV, 750 kV, 1050 kV

UCD, UCC: 380 kV, 650 kV, 1050 kV

Maximum rated through-current

See tables for diverter switches and tap selectors respectively. The lowest rating ofthe two determines the overall rating.

Tap selector size

C tap selector for UCG and VUCG only

I tap selector for UCG and VUCG only

III tap selector for UCG, VUCG, UCL and UCDIV tap selector for UCC

UCG . . XXXX/YYYY/ZVUCG . . XXXX/YYYY/Z

UCL . . XXXX/YYYY/Z

UCD . . XXXX/YYYY/Z

UCC . . XXXX/YYYY


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Maximum number of positions

Table 1. Maximum number of positions.

Type of switching Tap selector Max. number of positions

Linear C 14

I 18

III 22

IV 18

Plus/minus C 27

I 35

III 35

IV 35

Coarse/fine C 27

I 35

III 35

IV 35

Diverter switches

Table 2. Diverter switches.

Type Max. rated through-current

VUCG.N, B 700 A

VUCG.E, T 1600 A1)

VUCG.N, B, short version2) 600 A

VUCG.E, T, short version

2)

1000 AUCG.N, B 300, 500, 600 A

UCG.E, T 300, 500, 600, 1200, 15001)A

UCG.N, B, short version2) 300 A

UCG.E, T, short version2) 900 A

UCL.N, B 600, 900 A

UCL.E, T 600, 900, 1800, 24001)A

UCD.N3) 1000 A

UCD.E3) 1600 A

UCC.N3) 1600 A

UCC.E3) 1600 A

1) See also section Enforced current splitting.2) Shorter diverter switch housings, see dimension drawings in this guide. See also limits in

Fig. 14.3) UCC and UCD requires one motor-drive mechanism for each OLTC unit. Thus, three-

phase delta requires two UCC/D.E and three phases fully insulated requires threeUCC/D.E.


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Tap selectors

Table 3. Tap selectors.

Type Connection Max. rated through-current Max impulse test voltage

across range

C N, B 400 A 350 kV

E, T 400, 700, 1050, 12001)A 350 kV

I N, B 600 A 300 kV3)

E, T 600, 1200, 1500, 1600 A 300 kV3)

III N, B 1000 A 550 kV3)

E, T 1000, 1800, 24001)A 550 kV3)

IV2) N, E 1600 A 500 kV

1) With enforced current splitting in position.2) UCC requires one motor-drive mechanism for each unit and is therefore not available in

connection B and T.3) Note that for certain positions, these values are lower. See Insulating levels.

Possible combinations of diverter switches and tap selectors

Diverter switch UCG, VUCG UCL UCD UCC

Tap selector C I III IV

Enforced current splittingIn certain applications, two or more poles of an on-load tap-changer, ormore than one on-load tap-changer can work in parallel. However, it is im-portant to make this in a correct way. It differs between whether it shouldwork in position (not during operation) only or if it should operate duringoperation.

In position

Enforced current splitting in position is used only between poles withinone on-load tap-changer for operation in one phase. It is used when hav-ing a tap selector with a lower current rating than the diverter switch . Byhaving the same number of conductors through the regulating winding asthere are poles in the tap selector and connect each of them to one pole

of the tap selector, the rating for one pole times the number of poles canbe made use of. (Otherwise a certain reduction in current rating has to bedone due to unequal current splitting between the poles. For instance, a1050 A tap selector C can be used for 400 x 3=1200 A when the condi-tions for enforced current splitting are fulfilled).


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During operation

Enforced current splitting during operation can be used when the diverterswitch has a lower current rating than the tap selector or when two ormore on-load tap-changers work in parallel in the same phase.

By having the same number of conductors in parallel through the wind-ings as there are poles or on-load tap-changers in parallel, parallel work-ing conditions can be made to work. However, the impedance betweenthese parallel paths must be such that the current through any of thepoles or any of the on-load tap-changers must not exceed the rating ofany of them. The reason is that the poles in the diverter switch or the di-verter switches do not operate at exactly the same time.

To achieve this impedance, it is normally required that the parallel con-ductors are kept separated through both the regulating and the mainwinding. However, the impedance between them must be calculated bythe transformer manufacturer in each case where enforced current split-ting during operation should be made use of.

See also IEC 60214-2, paragraph 6.2.9 for information.


24/84

24 1ZSE 5492-105 en, Rev. 7

Rated through-current (A)

Step

voltage

(V)

500

0

1000

1500

2000

2500

3000

3500

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300

UCG.E,T

Short version

UCG.N,B

UCG.N,B

Short version

UCG.E,T

1400 1500


Ste

p

voltage

(V)

500

0

1000

1500

2000

2500

3000

3500

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

VUCG.E,T

Short version

1600

VUCG.N,B

VUCG.N,B

Short version

VUCG.E,T

Rated phase step voltageThe maximum permitted step voltage is limited by the electrical strengthand the switching capacity of the diverter switch. The rated phase stepvoltage is a function of the rated through current as shown in the dia-grams below.

For arc furnace transformers, only up to 75 % of the given step voltagesbelow are allowed. In case the current during electrode short circuitsexceeds twice the rated through-current, please contact the supplier foradvice.

UCG and VUCG in short version have a 220 mm shorter diverter switchhousing, see dimension drawings in this document. For short version,there might be restrictions in applications other than network.

Fig. 13. Rated phase step voltage for type UCG.

Fig. 14. Rated phase step voltage for type VUCG.


25/84

251ZSE 5492-105 en, Rev. 7


Step

voltage

(V)

500

0

1000

1500

2000

2500

3000

3500

0 200 400 6 00 800 10 00 1400 1600

3500

4500

5000

UCL.N,B

UCL.E,T

1200 1800 2000 2200 2400 2600

. ,. ,


Step

voltage

(V)

500

0

1000

1500

2000

2500

3000

3500

0 200 400 600 800 1 000 1200 1400 1600

UCC.N

3500

4500

5000UCC.E

For higher valuescontact ABB


Step

voltage

(V)

500

0

1000

1500

2000

2500

3000

3500

0 200 400 600 800 1000 1200 1400 1600

UCD.N

3500

4500

5000UCD.E

.

.

Fig. 15. Rated phase step voltage for type UCL.

Fig. 17. Rated phase step voltage for type UCD.

Fig. 16. Rated phase step voltage for type UCC.


26/84

26 1ZSE 5492-105 en, Rev. 7


No.o

foperations

50000

0

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

UCG.N,B100% load

80% average load

80% average load

UCG.E,T100% load


No.o

f

operations

100000

0

200000

300000

400000

500000

600000

700000

800000

900000

1000 000

0 100 200 300 600 800 900 1000 1100

VUCG.N,B

400 500 700 1200 1300 1400 1500 1600 1700

VUCG.E,T

Coarse fine regulation leakage inductance switching

When operating from the ends of the fine or the coarse winding a highleakage inductande might appear causing a phase shift between theswitched current and the recovery voltage. This value has to be givenwhen ordering an OLTC so a proper dimensioning is possible.

The leakage inductance value can be given in our order data sheetor be calculated by us from active part dimensions and number ofturns. For more information, see IEC 60214-2 or product information1ZSC000498-ABB.

Contact lifeThe predicted contact life of the fixed and moving contact of the diverterswitch, is shown as a function of the rated through current in the dia-grams below. It is based on the type test with 50000 switching operations,and a current corresponding to the maximum rated through current. Thecontact life is stated on the rating plate.

Fig. 18. Contact life for type UCG.

Fig. 19. Contact life for type VUCG.


27/84

271ZSE 5492-105 en, Rev. 7


No.o

foperations

50000

0

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 250 500 750 1000 1250 1500 1750 2000 2250

UCL.N,B100% load

80% average load

80% average load

UCL.E,T 100% load

2500


No.o

foperations

50000

0

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 200 400 600 800 1000 1200 1400 1600

80% average load

UCC.N 100% load

UCC.E100% load


No.o

f

operations

50000

0

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 200 400 600 800 1000 1200 1400

UCD.N 100% load

1600

UCD.E 100% load

Fig. 20. Contact life for type UCL.

Fig. 22. Contact life for type UCD.

Fig. 21. Contact life for type UCC.


28/84

28 1ZSE 5492-105 en, Rev. 7

Standards and testingThe on-load tap-changers made by ABB fulfil the requirements accordingto IEC 60214-1, 2003-02, and IEEE C57.131-1995.

The type tests include:

Contact temperature rise testSwitching tests

Short-circuit current test

Transition impedance test

Mechanical tests

Dielectric tests

The routine tests include:

Check of assembly

Mechanical test

Sequence test

Auxiliary circuits insulation testVacuum test

Final inspection

Rating plate

Insulation levelsLI is the lightning impulse (1.2/50 s) to earth. pf is the power frequencytest voltage to earth (60 s). The insulation levels are indicated as impulsewithstand voltage power frequency withstand voltage.

The tests were carried out according to IEC 60214-1, 2003-02, with anew on-load tap-changer and clean insulation transformer oil I -30 C ac-cording to IEC 60296. The withstand voltage value of the oil was higherthan 40 kV/2.5 mm (IEC 60156).

Fig. 23. Example of rating plate

fm_00299


29/84

291ZSE 5492-105 en, Rev. 7

a2

a1

b1

b2e1

g1

b1

a2 a1

b1

b2e1

g1

b1

Fig. 24. Linear switching.

correspondingcontact inadjacentphase

Linear

L

Insulation levels to earth

For UCG 380150 kV, 650275 kV, 750325 kV and1050460 kV

For UCL 380150 kV, 650275 kV, 750325 kV and1050460 kV

For UCC and UCD 380150 kV, 650275 kV and 1050460 kV

Lightning impulse levels (LI) and power frequency levels (Pf) correspondsto the following U

m-values acc. to IEC:

LI (kV) Pf (kV) Um (kV)

380 150 72,5

650 275 145

750 325 170

1050 460 300

Fig. 25. Reversing switching.

correspondingcontacts inadjacent phase

Reversing

R


30/84

30 1ZSE 5492-105 en, Rev. 7

a2 a1 f1

d1

b2e1

g1

b1

c1

f2

d1

a1 Between electrically adjacent contacts in the tap selector, notconnected.

a2 Between the ends of the fine regulating winding (across range). Forcoarse/fine switching in minus position, this means between thefreely oscillating end of the coarse winding and any end of the finewinding.

b1 Between not connected taps of different phases in the fine selector

b2 Between open contacts of different phases in the diverter switch.

c1 Between ends of the coarse winding in coarse/fine switching

d1 Between not connected taps of different phases in the coarse selec-tor (coarse/fine switching)

e1 Between preselected tap and connected tap of one phase in the di-verter switch and in the tap selector.

f1 Between any end of the coarse winding and connected tap

f2 Between any end of the coarse winding and the middle of the finewinding.

g1 Connected tap to earth

Fig. 26. Coarse/Fine switching.

correspondingcontacts inadjacent phase

Coarse/Fine

D


31/84


32/84

32 1ZSE 5492-105 en, Rev. 7

UCG and VUCG with tap selector III unshielded version

All values given as 1.2/50 s impulse withstand voltage (kV) power frequency withstand voltage (kV).

Type of

switching

No. of

positions

Within one phase Between phases for neutral

point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 490-150 - - - 100-20 100-20 500-160 -

L 15-16 300-125 420-150 - - - 100-20 100-20 500-160 -

L 17-18 300-125 350-140 - - - 100-20 100-20 500-160 -

R -11 300-125 490-150 - - - 100-20 100-20 500-160 -

R 12-13 300-125 420-150 - - - 100-20 100-20 500-160 -

R 14-15 300-125 350-140 - - - 100-20 100-20 500-160

R 16-27 300-125 490-160 - - - 100-20 100-20 500-160 -

R 28-31 300-125 420-150 - - - 100-20 100-20 500-160 -

R 32-35 300-125 350-140 - - - 100-20 100-20 500-160 -

D -11 300-125 490-160 600-200 600-200 600-200 100-20 100-20 500-160 600-200

D 12-13 300-125 420-150 600-200 600-200 600-200 100-20 100-20 500-160 600-200

D 14-15 300-125 350-140 600-200 600-200 600-200 100-20 100-20 500-160 600-200

D 16-27 300-125 490-160 600-200 600-200 600-200 100-20 100-20 500-160 600-200

D 28-31 300-125 420-150 600-200 600-200 600-200 100-20 100-20 500-160 600-200

D 32-35 300-125 350-140 600-200 600-200 600-200 100-20 100-20 500-160 600-200

UCG and VUCG with tap selector III shielded version


Type of

switching

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 550-180 - - - 100-20 100-20 550-180 -

L 15-16 300-125 480-160 - - - 100-20 100-20 550-180 -

L 17-18 300-125 400-150 - - - 100-20 100-20 550-180 -

L 19-22 300-125 350-125 - - - 100-20 100-20 550-180 -

R -11 300-125 550-180 - - - 100-20 100-20 550-180 -

R 12-13 300-125 480-160 - - - 100-20 100-20 550-180 -

R 14-15 300-125 400-150 - - - 100-20 100-20 550-180 -

R 16-27 300-125 550-180 - - - 100-20 100-20 550-180 -

R 28-31 300-125 480-160 - - - 100-20 100-20 550-180 -R 32-35 300-125 400-150 - - - 100-20 100-20 550-180 -

D -11 300-125 550-180 600-200 600-200 600-200 100-20 100-20 550-180 600-200

D 12-13 300-125 480-160 600-200 600-200 600-200 100-20 100-20 550-180 600-200

D 14-15 300-125 400-150 600-200 600-200 600-200 100-20 100-20 550-180 600-200

D 16-27 300-125 550-180 600-200 600-200 600-200 100-20 100-20 550-180 600-200

D 28-31 300-125 480-160 600-200 600-200 600-200 100-20 100-20 550-180 600-200

D 32-35 300-125 400-150 600-200 600-200 600-200 100-20 100-20 550-180 600-200


33/84

331ZSE 5492-105 en, Rev. 7

UCL with tap selector III unshielded version

All values given as 1.2/50 s impulse withstand voltage (kV) power frequency withstand voltage(kV).

Type of

switching

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 490-150 - - - 130-20 130-20 500-160 -

L 15-16 300-125 420-150 - - - 130-20 130-20 500-160 -

L 17-18 300-125 350-140 - - - 130-20 130-20 500-160 -

R -11 300-125 490-150 - - - 130-20 130-20 500-160 -

R 12-13 300-125 420-150 - - - 130-20 130-20 500-160 -

R 14-15 300-125 350-140 - - - 130-20 130-20 500-160 -

R 16-27 300-125 490-160 - - - 130-20 130-20 500-160 -

R 28-31 300-125 420-150 - - - 130-20 130-20 500-160 -

R 32-35 300-125 350-140 - - - 130-20 130-20 500-160 -

D -11 300-125 490-160 600-200 600-200 600-200 130-20 130-20 500-160 600-200

D 12-13 300-125 420-150 600-200 600-200 600-200 130-20 130-20 500-160 600-200

D 14-15 300-125 350-140 600-200 600-200 600-200 130-20 130-20 500-160 600-200

D 16-27 300-125 490-160 600-200 600-200 600-200 130-20 130-20 500-160 600-200

D 28-31 300-125 420-150 600-200 600-200 600-200 130-20 130-20 500-160 600-200

D 32-35 300-125 350-140 600-200 600-200 600-200 130-20 130-20 500-160 600-200

UCL with tap selector III shielded version

All values given as 1.2/50 s impulse withstand voltage (kV) power frequency withstand voltage

(kV).Type of

switching

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 550-180 - - - 130-20 130-20 550-180 -

L 15-16 300-125 480-160 - - - 130-20 130-20 550-180 -

L 17-18 300-125 400-150 - - - 130-20 130-20 550-180 -

L 19-22 300-125 350-125 - - - 130-20 130-20 550-180 -

R -11 300-125 550-180 - - - 130-20 130-20 550-180 -

R 12-13 300-125 480-160 - - - 130-20 130-20 550-180 -

R 14-15 300-125 400-150 - - - 130-20 130-20 550-180 -

R 16-27 300-125 550-180 - - - 130-20 130-20 550-180 -

R 28-31 300-125 480-160 - - - 130-20 130-20 550-180 -

R 32-35 300-125 400-150 - - - 130-20 130-20 550-180 -

D -11 300-125 550-180 600-200 600-200 600-200 130-20 130-20 550-180 600-200

D 12-13 300-125 480-160 600-200 600-200 600-200 130-20 130-20 550-180 600-200

D 14-15 300-125 400-150 600-200 600-200 600-200 130-20 130-20 550-180 600-200

D 16-27 300-125 550-180 600-200 600-200 600-200 130-20 130-20 550-180 600-200

D 28-31 300-125 480-160 600-200 600-200 600-200 130-20 130-20 550-180 600-200

D 32-35 300-125 400-150 600-200 600-200 600-200 130-20 130-20 550-180 600-200


34/84

34 1ZSE 5492-105 en, Rev. 7

UCD with tap selector III unshielded version


Type of

switching

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 490-150 - - - 200-20 200-20 500-160 -

L 15-16 300-125 420-150 - - - 200-20 200-20 500-160 -

L 17-18 300-125 350-140 - - - 200-20 200-20 500-160 -

R -11 300-125 490-150 - - - 200-20 200-20 500-160 -

R 12-13 300-125 420-150 - - - 200-20 200-20 500-160 -

R 14-15 300-125 350-140 - - - 200-20 200-20 500-160 -

R 16-27 300-125 490-160 - - - 200-20 200-20 500-160 -

R 28-31 300-125 420-150 - - - 200-20 200-20 500-160 -

R 32-35 300-125 350-140 - - - 200-20 200-20 500-160 -

D -11 300-125 490-160 600-200 600-200 600-200 200-20 200-20 500-160 600-200

D 12-13 300-125 420-150 600-200 600-200 600-200 200-20 200-20 500-160 600-200

D 14-15 300-125 350-140 600-200 600-200 600-200 200-20 200-20 500-160 600-200

D 16-27 300-125 490-160 600-200 600-200 600-200 200-20 200-20 500-160 600-200

D 28-31 300-125 420-150 600-200 600-200 600-200 200-20 200-20 500-160 600-200

D 32-35 300-125 350-140 600-200 600-200 600-200 200-20 200-20 500-160 600-200

UCD with tap selector III shielded version


Type of

switching

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L -14 300-125 550-180 - - - 200-20 200-20 550-180 -

L 15-16 300-125 480-160 - - - 200-20 200-20 550-180 -

L 17-18 300-125 400-150 - - - 200-20 200-20 550-180 -

L 19-22 300-125 350-125 - - - 200-20 200-20 550-180 -

R -11 300-125 550-180 - - - 200-20 200-20 550-180 -

R 12-13 300-125 480-160 - - - 200-20 200-20 550-180 -

R 14-15 300-125 400-150 - - - 200-20 200-20 550-180 -

R 16-27 300-125 550-180 - - - 200-20 200-20 550-180 -

R 28-31 300-125 480-160 - - - 200-20 200-20 550-180 -R 32-35 300-125 400-150 - - - 200-20 200-20 550-180 -

D -11 300-125 550-180 600-200 600-200 600-200 200-20 200-20 550-180 600-200

D 12-13 300-125 480-160 600-200 600-200 600-200 200-20 200-20 550-180 600-200

D 14-15 300-125 400-150 600-200 600-200 600-200 200-20 200-20 550-180 600-200

D 16-27 300-125 550-180 600-200 600-200 600-200 200-20 200-20 550-180 600-200

D 28-31 300-125 480-160 600-200 600-200 600-200 200-20 200-20 550-180 600-200

D 32-35 300-125 400-150 600-200 600-200 600-200 200-20 200-20 550-180 600-200


35/84

351ZSE 5492-105 en, Rev. 7

UCC with tap selector IV


Type of

switching

Shielded

(s)/unshielded

(us)

No. of

positions


point

a1 a2 c1 f1 f2 e1 b2 b1 d1

L us -16 200-80 300-125 - - - 200-20 200-20 300-125 -

L s -16 200-80 500-170 - - - 200-20 200-20 500-170 -

L us 17-18 200-80 300-125 - - - 200-20 200-20 300-125 -

L s 17-18 200-80 450-150 - - - 200-20 200-20 500-170 -

R us -13 200-80 300-125 300-125 - - 200-20 200-20 300-125 -

R s -13 200-80 500-170 600-200 - - 200-20 200-20 500-170 -

R us 14-15 200-80 250-95 300-125 - - 200-20 200-20 300-125 -

R s 14-15 200-80 400-150 600-200 - - 200-20 200-20 500-170 -

R us 16-27 200-80 300-125 300-125 - - 200-20 200-20 300-125 -

R s 16-27 200-80 500-170 600-200 - - 200-20 200-20 500-170 -

R us 28-35 200-80 250-95 300-125 - - 200-20 200-20 300-125 -

R s 28-35 200-80 400-150 600-200 - - 200-20 200-20 500-170 -

D us 16-27 200-80 300-125 300-125 350-150 350-150 200-20 200-20 300-125 350-150

D s 16-27 200-80 500-170 600-200 600-200 600-200 200-20 200-20 500-170 600-200

D us 28-35 200-80 250-95 300-125 350-150 350-150 200-20 200-20 300-125 350-150

D s 28-35 200-80 400-150 600-200 600-200 600-200 200-20 200-20 500-170 600-200


36/84

36 1ZSE 5492-105 en, Rev. 7

Short-circuit current strengthThe short circuit current strength is verified with three applications of 2 or 3 seconds duration, with-out moving the contacts between the three applications. Each application has an initial value of atleast 2.5 times the rms value.

Table 4.

Diverter

switch

Tap selector Max rated

through-current,

A rms

Type of

connection

2 s duration,

kA rms

3 sduration,

kA rms

Peak value,

kA

UCG C 300 N,B,E,T 7 6 18

C 400 N,B,E,T 7 6 18

C 500 E,T 10 10 25

C 600 E,T 10 10 25

C 700 E,T 15 15 38

C 900 E,T 16 16 40

C 1050 E,T 16 16 40I 300 N,B,E,T 71) 61) 18

I 500 N,B,E,T 71) 61) 18

I 600 N,B,E,T 71) 61) 18

I 900 E,T 17 17 43

I 1200 E,T 17 17 43

I 1500 E,T 18 18 45

III 300 N,B,E,T 71) 61) 18

III 500 N,B,E,T 71) 61) 18

III 600 N,B,E,T 71) 61) 18

III 900 E,T 10 10 25

III 1200 E,T 17 17 43

III 1500 E,T 18 18 45

VUCG C 400 N,B,E,T 7 7 20

C 700 E,T 10 10 25

C 1050 E,T 16 16 40

I 600 N,B,E,T 81) 81) 22

I 1200 E,T 15 15 38

I 1500 E,T 16 16 43

III 700 N,B,E,T 81) 81) 22

III 1600 E,T 16 16 43

UCL III 600 N,B,E,T 111)

111)

30III 900 N,B,E,T 111) 111) 30

III 1800 E,T 24 24 64

III 2400 E,T 27 27 79

UCD III 1000 N,B,E,T 18 182) 45

III 1600 E,T 18 182) 45

UCC IV 1600 N,E 18 182) 45

1) In case of UC..E,T or VUC..E,T higher values are possible on request.

2) Available for reinforced performance with 24 kArms

and 60 kApeak

.


37/84

371ZSE 5492-105 en, Rev. 7

Highest phase service voltage across the regulating windingThe table below show the highest permissible phase service voltage forthe different types of connections.

Table 5. Highest permissible phase service voltage across the regulatingwinding.

Across the regulatingwinding (kV)

Across the coarse and finewinding (kV)

Contact shieldings: with without with without

Tap-changer,

tap selector

UCC.N IV 52 35 75 45

UCD.N III

UCL.N III

UCG.N III

UCC.E IV 68 45 80 60

UCD.E, III

UCL.T, E, B III

UCG.T, E, B III

UCG.N C, I - 35 - 40

UCG.T, E, B C, I - 35 - 45

VUCG.T, E, B III 68 45 80 60

VUCG.N C, I - 35 - 40

VUCG.T, E, B C, I - 35 - 45

Rated through-currentThe rated through-current of the on-load tap-changer is the current which

the on-load tap-changer is capable of transferring from one tapping to theother at the relevant rated step voltage, and which can be carried continu-ously whilst meeting the technical data in this document. The rated throughcurrent is normally the same as the highest tapping current. The ratedthrough-current is limited by the step voltage according to the curves in thediagrams, Figs. 13 - 17. The rated through-current determines the dimen-sioning of the transition resistors and the contact life. The rated through-current is stated on the rating plate, Fig. 23.

Occasional overloadingIf the rated through-current of the tap-changer is not less than the high-est value of tapping current of the tapped winding of the transformer, thetap-changer will not restrict the occasional overloading of the transformer,according to IEC 60076-7, 2005-12, and ANSI/IEEE C57-91-1995.

To meet these requirements, the UC models have been designed so thatthe contact temperature rise over the surrounding oil does not exceed 20K when loaded with a 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 with consideration thatcurrents of maximum 1.5 times the rated through current occur during amaximum of 3 % of the tap-change operations. Overloading beyond thesevalues, results in increased contact wear and shorter contact life.

For more information about overloading, read the appropriate parts of IEC60214-2, 2004-10.


38/84

38 1ZSE 5492-105 en, Rev. 7

Oil temperatureProvided that insulating oil of class Transformer oil -30 C according toIEC 60296, 2003-11, is used, the temperature of the oil surrounding theon-load tap-changer shall be between -25 and +105 C for normal opera-tion, as illustrated below. The range for UC (not VUC!) can be extended to

-40 C provided that the viscosity does not exceed 2500 mm 2/s (=cst).

Individual brands need to be evaluated from case to case because of dif-ferences in viscosity compared to transformer grade mineral oil and thesubsequent difference in heat dissipation. Also dielectric strengths andinfluence form moisture needs to be considered. Switching in vacuumgenerally opens for use of a wider range of insulating fluids.

No operations allowed.

Emergency overloading. The on-load tap-changer will not restrict the

occasional overloading of the transformer according to the standardsstated in section Occasional overloading.

Normal operating range.

UC: When operating within this range, no overloading is allowed.VUC: Operation with de-energized transformer only.

UC: Operation with de-energized transformer only.VUC: No operation allowed.

1)

2)

3)

4)

5)


39/84

391ZSE 5492-105 en, Rev. 7

Coarse/fine regulation leakage inductance switchingWhen changing from the end of the fine winding to the end of the coarsewinding, a high leakage inductance can be set up with the two wind-ings in series. The critical moment occurs at switching the tap-changersmechanical mid-position, as the circulating current is passing through not

only one loop but also the entire coarse and fine tap winding.

The leakage inductance that occurs from one loop, Fig. 28, is neglectiblebut can be substantial from the complete coarse and fine winding, Fig. 29.

This leakage inductance causes a phase shift between switching currentand recovery voltage that makes the breaking more severe. The OLTCmust be dimensioned accordingly. The leakage inductance shall be speci-fied in the ordering data sheet.

For certain winding configurations, such as coarse and fine windings lo-cated axially, this value might be that high that it requires a larger OLTCthan would be needed otherwise. For more information, see product in-formation 1ZSC000498-AAR as well as IEC 60214-2, 2004-10, or consult

the supplier for advice.

Main winding

Coarse winding

Fine winding

Fig. 28. Normal operation Fig. 29. Operation with high leakage inductance.


40/84

40 1ZSE 5492-105 en, Rev. 7

Tie-in resistor and tie-in resistor switchWhen the change-over selector operates, the tapped winding is discon-nected for a short time. The voltage of that winding is then determined bythe voltage of and the capacitances to the surrounding windings or tankwall/core. For certain winding layouts, voltages and capacitances, the

capacitive controlled voltage will reach magnitudes that are too high forthe change-over selector. In these cases potential controlling resistors, socalled tie-in resistors, should be connected according to Fig. 30.

The tie-in resistor is connected between the middle of the tapped wind-ing and the connection point on the bottom of the diverter switch housing,see single phase diagrams in this document. This means that power iscontinuously dissipated in the resistors that add to the no-load losses ofthe transformers. The resistors must also be dimensioned for the powerdissipation.

The tie-in resistors are normally mounted separate from the OLTC but

can be mounted under the tap selector provided that tie-in resistor switchis not used. Please contact the supplier for advice in such case!

The following limits apply to the change-over selectors of the different tapselectors:

Tap selector Max recovery voltage (kV rms) Max capacitive current (mA rms)

C 35 200

I 35 200

III 35 300

IV 35 300

The capacitive current is the current going through the change-over se-

lector before it opens.

Diverter switch

Tie-in resistorswitch

Tie-in resistor

Tap selector

Main winding

Regulating windingwIth change-overselector

Fig. 30. Tie-in resistor example.


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411ZSE 5492-105 en, Rev. 7

HV

C1

RW

C2

+ -

U

In the figure above is a switch, the tie-in resistor switch, that connectsthe tie-in resistors only when they are needed. The switch is a part of thetap selector and is mounted on the bottom plate of the tap selector, seedimension drawings in this document.

This switch is used when the no-load losses must be kept low or/and

when the continuous power in the tie-in resistors is too high. The tie-inresistor switch is available for all tap selectors except tap selector C.

When ordering, give the winding layout and information according to theexample below and the supplier will calculate whether tie-in resistors areneeded or not. If needed, the supplier will choose the correct tie-in resis-tors. If a tie-in resistor switch is needed for limiting the no-load losses,give that information in the ordering data sheet! If anything is unclear,contact the manufacturer.

Example

C1 = Capacitance between HV and RWC2 = Capacitance between tank and RWFrequency 50 Hz

Winding Phase voltage Connection

High voltage (HV) 132 kV (H1) Delta

Regulating winding (RW)(Voltage across)

13.3 kV (U) Plus/Minus

Tank


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42 1ZSE 5492-105 en, Rev. 7

Installation and maintenance

On-load tap-changer

InstallationThe on-load tap-changers can be delivered for cover-mounting method oryoke-mounting method onto the transformer.

For detailed installation instructions, consult the appropriate Installationand Commissioning Guide.

Drying

The on-load tap-changer must be stored indoors and left in its plasticshipping cover until time for assembly. The OLTC should be subjected todrying before taken into service. The diverter switch should not partici-pate in the drying process. For further instructions refer to the Installation

Guide.

Weights

The tables below shows all the weights of the UC range of tap-changers.

Table 7. Weights for type UCG.

On-load tap-changer

type designation

Approximate weight in kg

Tap-changerwithout oil1)

Required oil Total

UCG.N 380-750/300-600 425 185 610

1050/300-600 435 230 665

UCG.T 380-750/300-900 1025 3x185 1580

380-750/1050-1500 1190 3x185 1745

1050/300-900 1090 3x230 1780

1050/1050-1500 1225 3x230 1915

UCG.B 380-750/300-600 760 2x185 1130

1050/300-600 780 2x230 1240

UCG.E 380-750/300-900 360 185 545

380-750/1050-1500 410 185 595

1050/300-900 370 230 600

1050/1050-1500 425 230 655

1) The weight of the diverter switch, approximately 90 kg, is included.


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431ZSE 5492-105 en, Rev. 7

Table 8. Weights for type VUCG.

On-load tap-changertype designation


Tap-changer

without oil1)Required oil Total

VUCG.N 380-750/400-600 450 185 635

380-750/700 500 185 6851050/400-600 460 230 690

1050/700 510 230 740

VUCG.T 380-750/400-1200 1100 3x185 1655

380-750/1500-1600 1250 3x185 1805

1050/400-1200 1165 3x230 1855

1050/1500-1600 1315 3x230 2005

VUCG.B 380-750/400-600 810 2x185 1180

380-750/700 910 2x185 1280

1050/400-600 830 2x230 1290

1050/700 930 2x230 1390

VUCG.E 380-750/400-1200 385 185 570

380-750/1500-1600 435 185 620

1050/400-1200 395 230 625

1050/1500-1600 445 230 675


Table 9. Weights for type UCL.

On-load tap-changer

type designation


Tap-changerwithout oil1)

Required oil Total

UCL.N 380/600, 900 480 260 740

650/600, 900 500 300 8001050/600, 900 510 340 850

UCL.T 380/600, 900 1230 3x260 2010

380/1800 1350 3x260 2130

380/2400 1440 3x260 2220

650/600, 900 1290 3x300 2190

650/1800 1410 3x300 2310

650/2400 1500 3x300 2400

1050/600, 900 1320 3x340 2340

1050/1800 1440 3x340 2460

1050/2400 1530 3x340 2550

UCL.B 380/600, 900 850 2x260 1370

650/600, 900 890 2x300 1490

1050/600, 900 910 2x340 1590

UCL.E 380/600, 900 410 260 670

380/1800 450 260 710

380/2400 480 260 740

650/600, 900 430 300 730

650/1800 470 300 770

650/2400 500 300 800

1050/600, 900 440 340 780

1050/1800 480 340 820

1050/2400 510 340 850



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44 1ZSE 5492-105 en, Rev. 7

Table 10. Weights for type UCD.

On-load tap-changertype designation


Tap-changer


UCD.N 380/1000 900 700 1600

650/1000 940 760 17001050/1000 960 860 1820

UCD.E 380/1000 840 700 1540

380/1800 870 700 1570

380/2400 900 700 1600

650/1000 880 760 1640

650/1800 910 760 1670

650/2400 940 760 1700

1050/1000 900 860 1760

1050/1800 930 860 1790

1050/2400 960 860 1820

1)The weight of the diverter switch, approximately 250 kg, is included.

Table 11. Weights for type UCC.

On-load tap-changer

type designation


Tap-changer


UCC.N 380/1600 1140 700 1840

650/1600 1180 760 1940

1050/1600 1200 860 2060

UCC.E 380/1600 1040 700 1740

650/1600 1080 760 1840

1050/1600 1100 860 1960)The weight of the diverter switch, approximately 250 kg, is included.

Oil filling

For details of oil filling, consult the appropriate Installation andCommissioning Guide.


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451ZSE 5492-105 en, Rev. 7

Maintenance

For information about maintenance, the appropriate Maintenance Guideshould be used.

Pressure

During drying, the on-load tap-changers should have no pressure dif-ference to the transformer. This is obtained by opening the VP-valvein the bottom, see the Installation and commissioning guide for furtherinformation.

During oil filling and testing, up to 200 kPa pressure difference to the at-mosphere is allowed. During service, max. 150 kPa pressure difference tothe atmosphere is allowed.

The pressure difference to the transformer tank during oil filling and test-ing is allowed to be max 100 kPa. During service, the pressure is recom-mended to be as low as possible and not more than 50 kPa and thenpreferably higher in the transformer tank. For higher pressures, contact

the supplier.

Accessories and protection devicesThe tap-changer can be equipped with various protection devices. Thestandard protection device is the pressure relay. An oil flow relay is alsoavailable.

Pressure relief device with alarm signal is also available as well as someother supervisory sensors.

For more information about accessories and protection devices see tech-nical description 1ZSC000562-AAD.


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46 1ZSE 5492-105 en, Rev. 7

Motor-drive mechanism

Design

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

Installation

The motor-drive mechanism is fitted to the outside of the transformertank, and connected to the on-load tap-changer by drive shafts and bevelgears.

For the correct installation procedure, consult the appropriate InstallationGuide.

Maintenance

The motor-drive mechanism should be visually inspected anually.

For the correct inspection and maintenance procedures, consult the ap-propriate Maintenance Guide.

Operating shafts

Length L1 (mm) L2 (mm) L3 and L4 (mm) Motor-drivemechanism

Min/max 500/3100 525/3100 900/2700 BUE

500/3100 600/3100 BUL

The minimum and maximum lengths refer to mechanical design only. ForL2 vertical shaft see following pages. Other shaft arrangements are avail-able on request.

For standard shaft arrangements, the maximum angle (totally in two di-rections) is 4. For larger angles, special couplings are needed.


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471ZSE 5492-105 en, Rev. 7

Fig. A

L1

UCG.N, EVUCG.N, EUCL.N, EUCD.N, EUCC.N, E

Fig. B

L1

Fig. C

L3 L1

UCG.BVUCG.BUCL.B

Fig. D

L1 L3

Fig. E

L4 L3 L1

UCG.TVUCG.TUCL.T

Fig. F

L1 L3 L4

Fig. 31. Positioning of motor-drive mechanism.

For singel units(UC..E, N andVUC..E, N) thegear box of thetap-changer mightbe mounted in the

angle given below.


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48 1ZSE 5492-105 en, Rev. 7

Dimensions

Type UCG/C and VUCG/C

Dimensions in mm. The design, technical data and dimensions are sub-ject to alteration without notice. For more information, see the dimension

drawings.

C/L Tap selector C/L Diverter switch

Section A APlus/Minus andCoarse/Fineswitching

Section A ALinear switching

145

353

80

230

134

440

R210

570

570

615

D=420

615

R210

818

194

36

75

157

L2

2907)

L1H32)

A A

205

D=600

D=470

345

390

30

H2

70

4057)

1)

1)

D=420

332

D=740

111

16O

H1

BUL

BUL

BUE2

BUE2


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491ZSE 5492-105 en, Rev. 7

Type UCG/I and VUCG/I

Dimensions in mm. The design, technical data and dimensions are sub-ject to alteration without notice.

C/L Tap selector C/L Diverter switch



36

1)

610

19475

157

L2

L1

H1

H2

D=600

D=470

1)

1)

30

6053)

665

3903)

500

500 4103)

4203) 530

332

3397)

390

145

353

818

23016

80

440

4)

70

30

195

H32)

205

D=740

134

AA

111

4057)

BUL

BUL

BUE2

BUE2


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50 1ZSE 5492-105 en, Rev. 7

Type UCG/III and VUCG/III


Model for mounting ontransformers active part

Model for cover mounting

C/L Diverter switchC/L Tap selector

Section B - BLinear switching

Section B - BPlus/Minus andCoarse/Fine switching

H2

H1

BB

85

H1+106

30

385

5864903)

8403)

293

936

4903)

4903) 580

2453)

580

4)


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511ZSE 5492-105 en, Rev. 7

Tables UCG and VUCG


For tap

selector size

Impulse withstand

voltage to earth (kV)

H1

(mm)

H1, short

version (mm)

H3 2)(mm)

H3 2), shortversion (mm)

C 380, 650, 750 1192 972 1400 1200

1050 1492 1272 1700 1500

I 380, 650, 750 1317 1097 1400 1200

1050 1617 1397 1700 1500

III 380, 650, 750 1354 1134 1400 1200

1050 1654 1434 1700 1500

Tap selector

For on-load tap-changer type

Max ratedthrough-current

(A)

H2, size C (mm) H2, size I (mm) H2, size III (mm)

UCG.N, VUCG.N 400 959 - -

300-600 - 1026 1160

UCG.E, UCG.T5),VUCG.E, VUCG.T5)

400 519 - -

300-600 - 526 552

700 739 - -

900 - - 552

1050 959 - -

1200 - 756 856

1500 - 1026 856

UCG.B6), VUCG.B6) 400 Single-phase unit 519

Two-phase unit 739

- -

300-600 - Single-phase unit 526Two-phase unit 776

Single-phase unit 552Two-phase unit 856

1) Shielding rings are used only for insulation level 650-275 kV and higher.2) Space required for lifting the diverter switch, excluding the lifting equipment.

3) Dimension without shielding ring.

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

5) UCG.T and VUCG.T consists of three single-phase units.6) UCG.B and VUCG.B consists of one single-phase and one two-phase unit arranged as shown in the dimension drawing

for UCL.B.

7) Space required for protective equipment.


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52 1ZSE 5492-105 en, Rev. 7

Type UCL/III


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



3018)

4808)


53/84


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54 1ZSE 5492-105 en, Rev. 7

Tables UCL


Impulse withstand voltage to earth (kV) H1 (mm) H3 2)(mm)

380 1415 1500

650 1615 17001050 1815 1900

For mounting on active part5) H1+85 H3+100

Tap selector

For on-load tap-changer type Max rated through-current (A) H2, size III (mm)

UCL.N 600-900 1160

UCL.E, UCL.T6) 600-900 552

1800 856

2400 1160

UCL.B7) 600-900 Single-phase unit H22 = 552

Two-phase unit H21 = 856

1) Shielding rings are used only for insulation level 650-275 kV and higher.

2) Space required for lifting the diverter switch, excluding the lifting equipment.3) Dimension without shielding-ring.


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 unit and one two-phase unit.8) Space required for protective equipment.


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551ZSE 5492-105 en, Rev. 7

Type UCD/III


2046)

7886)


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56 1ZSE 5492-105 en, Rev. 7

Tables UCD



380 1594 1700

650 1734 1900

1050 1934 2200

Tap selector


UCD.N 1000 1160

UCD.E 1000 552

1800 856

2400 11601) Shielding rings are used only for insulation level 650-275 kV and higher.

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

3) Dimension without shielding ring.4) For tie-in resistor switch add 370 mm.5) When two or three units are fitted together (three-phase delta and three-phase fully insulated respectively) the distance

between the units (c) must be at least 1340 mm from mechanical point of view. For final dimensioning, check theinsulation distance required.

6) Space required for protective equipment.


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Type UCC/IV



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58 1ZSE 5492-105 en, Rev. 7

Tables UCC



380 1540 1700

650 1680 1900

1050 1880 2200

Tap selector


UCC.N 1200 1282

1600 1522

UCC.E 1600 1282

1) Shielding rings are used only for insulation level 650-275 kV and higher.2) Space required for lifting the diverter switch, excluding the lifting equipment.3) Dimension without shielding ring.


5) When two or three units are fitted together (three-phase delta and three-phase fully insulated respectively) the distancebetween the units (c) must be at least 1340 mm from mechanical point of view. For final dimensioning, check theinsulation distance required.


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591ZSE 5492-105 en, Rev. 7

Oil conservator

The transformer manufacturer must provide a conservator for the tap-changer. Consider the below as a guideline for the design.

The breathing device should prevent moisture from getting intothe tap-changer compartment and let gases from the arcings out.

The oil volume should be such that the oil level always is withinthe range of the oil level indicator at all predictable temperatures.

X corresponds to a height giving a max permissible pressure dif-ference between the tap-changer tank and the transformer tank of50 kPa.

H corresponds to a height giving a max pressure difference be-tween the tap-changer and the atmosphere of 150 kPa.

The oil level for the tap-changer should be equal or below the oillevel of the transformer. Temporary during service the value is al-lowed to be negative.

Vacuum proof conservator if the tap-changer should be oil filledunder vacuum with the conservator mounted.

Note that separate oil conservators for the transformer and the tap-changer (also for the vacuum tap-changer) are recommended. Both oiland air side should be separated. For transformers with common con-servator for both the transformer and the tap-changer a filter should bemounted in the pipe from the tap-changer to the conservator.

1.

2.

3.

4.

5.

6.


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60 1ZSE 5492-105 en, Rev. 7

Appendices: Single-Phase DiagramsThe basic connection diagrams illustrate the different types of switchingand the appropriate connections to the transformer windings. The dia-grams illustrate the connections with the maximum number of turns in thetransformer winding, with the tap-changer in position 1.

The tap-changer can also be connected in such a way that position 1gives a minimum effective number of turns in the transformer winding withthe tap-changer in position 1.

Appendix 1: Single-phase diagrams for UCG/C

Linear Plus/Minus Coarse/Fine

4 steps

Number of loops:

4

Number of tap positions:

5

5 steps

Number of loops:

5


6


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611ZSE 5492-105 en, Rev. 7


6 steps

Number of loops:

6


7

7 steps

Number of loops:

7


8

8 steps

Number of loops:8 4 4 + 4


9 9 9


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62 1ZSE 5492-105 en, Rev. 7


10 steps

Number of loops:

10 5 5 + 5


11 11 11

12 steps

Number of loops:

12 6 6 + 6


13 13 13

13 steps

Number of loops:13


14


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631ZSE 5492-105 en, Rev. 7


16 steps

Number of loops:

8 8 + 8


17 17

18 steps

Number of loops:

10 9 + 10


19 19

20 steps

Number of loops:10 10 + 10


21 21


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64 1ZSE 5492-105 en, Rev. 7


22 steps

Number of loops:

12 11 + 12


23 23

24 steps

Number of loops:

12 12 + 12


25 25

26 steps

Number of loops:14 13 + 14


27 27


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651ZSE 5492-105 en, Rev. 7

Appendix 2: Single-phase diagrams for UCG/I


4 steps

Number of loops:

4


5

5 steps

Number of loops:

5


6

6 steps

Number of loops:

6


7


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671ZSE 5492-105 en, Rev. 7


12 steps

Number of loops:

12 6 6 + 6


13 13 13

14 steps

Number of loops:

14 7 7 + 7


15 15 15

16 steps

Number of loops:16 8 8 + 8


oltc ucg_vucg 1zse 5492-105 technical guide

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