1ZSC000562-AAW en On-load tap-changers, type UC ......and apparatus in the control circuits....

On-load tap-changers, type UCTechnical guide

1ZSC000562-AAW en

Original instruction

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

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

This document must not be copied without our written permission, and the contents thereof must not be imparted to a third party nor be used for any unauthorized purpose. Contravention will be prosecuted.

Manufacturer’s declaration

The manufacturer ABB AB Components 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 a component of a mineral oil filled power transformer, complies 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 are 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 has been declared in conformity with the Machinery Directive.

Date 2012-03-30

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

Hans Linder

Title Manager Tap-Changers, Local Product Group Unit Components

ContentDesign principles .................................................................................................................. 6

On-load tap-changer (OLTC) ........................................................................................... 6Diverter switches ............................................................................................................ 8Motor-drive mechanism .................................................................................................. 11Accessories .................................................................................................................... 11

Tap-changer principles of operation ...................................................................................... 12Switching sequence, UC ................................................................................................ 12Type of regulation ............................................................................................................ 13

Linear switching (type L) ........................................................................................... 13Change-over selector for plus/minus switching (type R) ............................................. 13Change-over selector for coarse/fine switching (type D) ........................................... 13

Type of connection .......................................................................................................... 14Three-phase star point (N) ......................................................................................... 14Single-phase (E) ........................................................................................................ 14Three-phase delta (B) ................................................................................................ 14Three-phase delta fully insulated (T) ........................................................................... 14Auto transformer (T) .................................................................................................. 14

Tap-changer characteristics and technical data .................................................................... 15Type designation ............................................................................................................. 15Type of tap-changer ........................................................................................................ 15Type of switching ............................................................................................................ 15Type of connection .......................................................................................................... 15Impulse withstand voltage to earth .................................................................................. 15Maximum rated through-current ...................................................................................... 15Tap selector size ............................................................................................................. 15Diverter switches ............................................................................................................ 16Tap selectors .................................................................................................................. 16

Possible combinations of diverter switches and tap selectors .................................... 16Maximum number of positions ........................................................................................ 16Enforced current splitting ................................................................................................ 16

In position ................................................................................................................. 16During operation ....................................................................................................... 16

Rated phase step voltage ............................................................................................... 17Coarse fine regulation leakage inductance switching ................................................. 17

Contact life ..................................................................................................................... 18Standards and testing ..................................................................................................... 19Rating plate .................................................................................................................... 19Insulation levels ............................................................................................................... 20

Insulation levels to earth (g1 and g2) .......................................................................... 20

Withstand voltages ......................................................................................................... 21UCG with tap selector C ........................................................................................... 21UCG with tap selector III unshielded version .............................................................. 21UCG with tap selector III shielded version .................................................................. 22UCL with tap selector III unshielded version ............................................................... 22UCL with tap selector III shielded version................................................................... 23UCD with tap selector III unshielded version .............................................................. 23UCD with tap selector III shielded version .................................................................. 24UCC with tap selector IV ........................................................................................... 24

Short-circuit current strength .......................................................................................... 25Highest phase service voltage across the regulating winding .......................................... 25Oil temperature ............................................................................................................... 26Alternative insulating liquids............................................................................................. 26Rated through-current .................................................................................................... 26Occasional overloading ................................................................................................... 26Coarse/fine regulation leakage inductance switching ....................................................... 27Tie-in resistor and tie-in resistor switch ........................................................................... 27

Installation and maintenance ................................................................................................. 29Tap-changer ................................................................................................................... 29

Installation ................................................................................................................. 29Drying ....................................................................................................................... 29Weights ..................................................................................................................... 29

Motor-drive mechanism .................................................................................................. 30Design ....................................................................................................................... 30Installation ................................................................................................................. 30Maintenance ............................................................................................................. 30Operating shafts ........................................................................................................ 30Oil filling .................................................................................................................... 30Maintenance ............................................................................................................. 30Pressure .................................................................................................................... 30

Accessories and protection devices ................................................................................ 30

Dimensions ........................................................................................................................... 32Oil conservator ................................................................................................................ 41

Appendices: Single-phase diagrams ..................................................................................... 42Appendix 1: Single-phase diagrams for UCG/C .............................................................. 42Appendix 2: Single-phase diagrams for UCG/III, UCL/III and UCD/III ............................... 48Appendix 3: Single-phase diagrams for UCC/IV .............................................................. 55

6 Technical guide UC | 1ZSC000562-AAW en

On-load tap-changer (OLTC)When the on-load tap-changer operates, the insulating oil is contaminated. The UC types, with arc quenching in oil, contaminate the oil heavily. To avoid contamination of the transformer oil the tap-changer is built in two separate sections: the diverter switch, which has its own housing separate from the rest of the transformer, and the tap selector. The tap selector, which is mounted beneath the diverter switch housing, consists of the fine tap selector and usually also of a change-over selector.

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 type UC.

Diverter switch

Tap selector

Design principles

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

The UC types come in a wide range of models with a rating suitable for every application.

1ZSC000562-AAW en | Technical guide UC 7

Cover

Lifting eye

Top section

Shielding-ring

Current terminal

Bottom section

Valve for use at processing

Connections from the tap selector

Plug-in contacts

Insulating cylinder

Diverter switch

Oil draining tube

Flange for connection to gas operated relay

Intermediate gear

Driving disc for the diverter switch

Guide pins

Fixed and moving contacts

Transition resistors

Shielding-ring

Insulating shaft

Bevel gear with position indicator

Buffer springs

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


Diverter switchesThe diverter switches with arc quenching in oil, are of the high-speed, spring-operated type with resistors as transition impedance. They are equipped with plug-in contacts that automatically connect the switch to the bushings in the diverter switch housing when it is lowered into the housing. Guiding facilities keep the diverter switch in the correct position when lowering it into the housing. Mechanical coupling to the motor-drive mechanism is automatically established when the 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.

The diverter switch is designed as a system of moving and fixed contacts. Movement of the moving contact system is controlled by a self-locking polygon link system with a set of helical springs. The link system is robust and has been carefully tested. The fixed contacts are placed on the sides of 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.

Fig. 3. Example of diverter switch type UCG.

Tap selectorsAlthough the tap selector for the UC range of tap-changer is available in various sizes, all have similar functions with different ratings.

The fixed contacts are mounted around the central shafts. The moving contacts are mounted on, and are operated by, the shafts in the center of the selector. The moving contacts are connected, via current collectors, to the 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 fingers each. The fingers make contact at one end with the fixed contact, and at the other with the current collector. The moving contacts slide on the fixed contacts and the current collector rings, giving a wiping action which makes the contacts self cleaning. This arrangement promotes good conductivity and negligible contact wear.

Fig. 4. Tap selectors, size C and size III.


L (m)

3

2

1

UCG.N/C650 kV

UCG.N/III650 kV

UCL.N/III650 kV

UCD.N/III650 kV

UCC.N650 kV

Design differences across the UC range of on-load tap-changersThe UC range of tap-changers consists of four diverter switches and three tap selectors.

The diverter switches, in order from the smallest to the biggest, are UCG, UCL, UCD and UCC, which all have arc quenching in oil.

The tap selectors, in order from the smallest to the biggest, are C, III and IV. Tap selector C can be combined with UCG diverter switches. Tap selector III can be combined with all diverter switches except UCC. Tap selector IV can be combined with UCC only.

For correct selection, use this Technical Guide or the ABB selection program “Compas”.

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

UCL manages star connected transformers up to 500 – 600 MVA and auto transformers 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 UCC must have its own motor-drive mechanism.

In tap selector IV the fixed contacts are mounted on insulating bars, whereas the C and III types use a complete, undivided glass fiber reinforced epoxy cylinder.

Fig. 5. On-load tap-changers type UC, size comparison.


Diverter switch housing and top section The top section forms the flange that is used for mounting to the transformer cover, and for carrying the gear box for the operating shafts. The top section includes a connection for the conservator pipe, draining and filtering connections, an earthing terminal, the supervisory device, and the cover with its gasket. The top section is available in two designs, one for cover mounting and one for pre-mounting (yoke-mounting) on the transformer’s active part.

The diverter switch housings have high quality seals that guarantee vacuum and overpressure-proof performance under all service conditions. In case of material ageing after extremely long service the seals can be re-tightened.

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

The drive shafts and bevel gears are placed beside the diverter switch cylinders, 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 the diverter switch. There is also a drain valve in the bottom which should only be opened during the drying process of the transformer.

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

PaintingThe diverter switch housing top sections are finish coated with a blue-grey color, Munsell 5,5 B 5,5/1,25, corrosion class C3 according to SS-EN ISO 12944-2 and SS-EN-ISO 9223. For higher corrosion classes such as C4 or C5, please contact ABB for further information.

Operating mechanismThe bevel gear, mounted on the top section flange transfers the drive from the motor-drive mechanism, via the vertical insulated shaft, to the intermediate gear for the diverter switch and the tap selector.

From the intermediate gear, a drive shaft transfers the energy to the diverter switch through an oil tight gland in the bottom of the diverter switch housing. When the diverter switch is lowered into the housing (after inspection), the drive is easily re-connected by a simple procedure that ensures that the drive shaft and the guide pin of the diverter mechanism are correctly aligned.

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

The external drive shaft, which does not need to be removed during maintenance work, minimizes the risk of misalignment in the system. However a mechanical end limit stop for the tap selector is available on request.

Special shaft systems are also available on request.

Transition resistorsThe transition resistors are made of wire and located above the diverter switch contacts. The resistors are robust and designed to last the lifetime of the mechanism under normal service conditions.

Special applications, load conditions, environments and insulating liquidsPlease contact the supplier for advice in the following cases:

– For applications other than network. (Restrictions in number of operations might be valid.)

– In case of unusual load conditions such as overloads beyond IEC 60076-7 or IEEE C57.91-1995, extreme inductive or capacitive loads or loads beyond the given data in this document.

– In case of requirement of other insulating liquids than mineral oil.

– Current measurement in phase before star point.


Special designsOn request, the UC tap-changers are also available for regulation with bias winding and for Y/D regulation.

On-line oil filtrationOn-line oil filtration is not required in any application and does not extend lifetime of contacts, but can give benefits for on-load tap-changers with arc quenching in oil in certain applications such as:

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

– High voltage line end applications (maintains the high dielectric withstand of the insulating liquid)

– Whenever short outage time is important when carrying out maintenance

– At any application with a high number of operations or high dielectric stresses.

The ABB on-line oil filtration works with continuous low flow filtration giving the best filtration result, less risk of gas bubbles and requires less control equipment. Filter cartridges are easily replaced without taking the transformer out of service.

The filtration reduces the number of particles and keeps the moisture level at a dielectric safe level.

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

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


Switching sequence, UC The switching sequence of the on-load tap-changer from position 6 to position 5, is shown in Figs. 8 - 13.

The sequence is designated the flag cycle. This means that the main switching contact of the diverter switch breaks before the transition resistors are connected across the regulating step. This ensures maximum reliability for non-vacuum types when the switch operates with overloads.

Fig 8. Position 6

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

Fig. 9

Selector contact H has moved in the no-load state from tap 7 to tap 5.

Fig. 10

The main contact x has opened. The load current passes through the resistor Ry and the resistor contact y.

Fig. 11

The resistor contact u has closed. The load current is shared between Ry and Ru. The circulating current is limited by the resistance of Ry plus Ru.

Fig. 12

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

Fig. 13. Position 5

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

Tap-changer principles of operation

At rated load, the breaking takes place at the first current zero after contact separation, which means an average arcing time of approximately 4-6 ms. The total time for a complete sequence is approximately 50 ms. The tap change operation time of the motor-drive mechanism is approximately 5 s/step. (10 s for through-positions).


Type of regulationLinear switching (type L) The regulating range is equal to the voltage of the tapped winding. No change-over selector is used. Fig. 14.

Fig. 14.

Reversing Change-over selector

Fig. 15.

Change-over selector, coarse/fine

Fig. 16.

Change-over selector for plus/minus switching (type R)The change-over selector extends the regulating range to twice the voltage of the tapped winding, by connecting the main winding to different ends of the regulating winding. Fig. 15.

Change-over selector for coarse/fine switching (type D) In type D switching the change-over selector extends the regulating range to twice the voltage of the tapped winding, by connecting or disconnecting the coarse regulating winding. Fig. 16.


Type of connectionThree-phase star point (N)Only one unit is required for all three phases. The transformers neutral point is in the tap-changer.

Single-phase (E)Only one unit is required

Three-phase delta (B)Two units required. Driven by a common motor-drive. One unit common for two phases.

Three-phase delta fully insulated (T)Three units required. Driven by a common motor-drive, except tap-changer types UCC and UCD.

Auto transformer (T)Several configurations of auto transformers exist. This example shows the tap-changer in auto-tap.

Fig. 17.

Fig. 18.

Fig. 19.

Fig. 20.

Fig. 21.


Type designation

Example UCGRE 650/700/C

Type of tap-changerUC... Diverter switch with arc quenching in oil

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, 750 kV, 1050 kVUCD, UCC: 380 kV, 650 kV, 1050 kV

Maximum rated through-currentSee tables for diverter switches and tap selectors respectively. The lower rating of the two determines the overall rating.

Tap selector sizeC tap selector for UCG onlyIII tap selector for UCG, UCL and UCDIV tap selector for UCC

UCG . . XXXX/YYYY/Z UCL . . XXXX/YYYY/Z UCD . . XXXX/YYYY/Z UCC . . XXXX/YYYY/Z

Tap-changer characteristics and technical data


Diverter switchesType Max. rated

through-current

UCG.N, B 400, 500, 600 A

UCG.E, T 500, 600, 900, 1200, 1500, 1800 4) A

UCG.N, B, short version 1) 300 A

UCG.E, T, short version 1) 600, 900 A

UCL.N, B 600, 900, 925 A

UCL.E, T 600, 900, 1800, 2400, 2700 4) A

UCD.N 2) 1000 A

UCD.E 2) 1600 A 3)

UCC.N 2) 1600 A

UCC.E 2) 1600 A 3)

Table 1. Diverter switches.1) Shorter diverter switch housings, see dimension drawings in this guide. See also

limits in Fig. 22.2) UCC and UCD require one motor-drive mechanism for each tap-changer unit.3) For higher ratings, please contact ABB.4) Requires enforced current splitting during operation. See section Enforced current

splitting.

Tap selectorsType Connection Max. rated through-current Max impulse

test voltage

across range

C N, B 600 A 350 kV 2)

E, T 600, 1200, 1500 A 350 kV 2)

III N, B 1000 A 550 kV 2)

E, T 1000, 1800, 2400 A 550 kV 2)

IV 1) N, E 1600 A 500 kV

Table 2. Tap selectors.1) UCC requires one motor-drive mechanism for each unit and is therefore not available

in connection B and T.2) Note that for certain positions, these values are lower. See Insulating levels.

Possible combinations of diverter switches and tap selectors

Diverter switch UCG UCL UCD UCC

Tap selector C III IV

Maximum number of positionsType of switching Tap selector Max. number of positions

Linear C 18

III 22

IV 18

Plus/minus C 35

III 35

IV 35

Coarse/fine C 35

III 35

IV 35

Table 3. Maximum number of positions.

Enforced current splittingIn certain applications, two or more poles of a tap-changer, or more than one tap-changer can work in parallel. However, it is important to implement this in a correct way. There is a difference between whether it should work in position (not during operation) only or if it should work during operation.

In positionEnforced current splitting in position is used only between poles within one tap-changer for operation in one phase. It is used when having a tap selector with a lower current rating than the diverter switch. By having the same number of conductors through the regulating winding as there are poles in the tap selector and connecting each of them to one pole of the tap selector, the rating for one pole times the number of poles can be made use of. Otherwise a certain reduction in current rating has to be done due to unequal current splitting between the poles.

During operationEnforced current splitting during operation can be used when the diverter switch has a lower current rating than the tap selector or when two or more tap-changers work in parallel in the same phase.

By having the same number of conductors in parallel through the windings as there are poles or tap-changers in parallel, parallel working conditions can be made to work. However, the impedance between these parallel paths must be such that the current through any of the poles or any of the tap-changers must not exceed the rating of any of them. The reason is that the poles in the diverter switch or the diverter switches do not operate at exactly the same time.

To achieve this impedance, it is normally required that the parallel conductors are kept separated through both the regulating and the main winding. However, the impedance must be calculated by the transformer manufacturer in each case where enforced current splitting during operation should be made use of.

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


500

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UCD.N

UCD.E

Rated phase step voltageThe maximum permitted step voltage is limited by the electrical strength and the switching capacity of the diverter switch. The rated phase step voltage is a function of the rated through current as shown in the diagrams below.

For arc furnace transformers, only up to 75 % of the given step voltages below are allowed. In the event the current during electrode short circuits exceeds twice the rated through-current, please contact the supplier for advice.

UCG in the short version has a 220 mm shorter diverter switch housing, see dimension drawings in this document. For short versions, there might be restrictions in applications other than network.

Coarse fine regulation leakage inductance switchingWhen operating from the ends of the fine or the coarse winding, a high leakage inductance might appear causing a phase shift between the switched current and the recovery voltage. This value has to be given when ordering a tap-changer so that proper dimensioning is possible.

The leakage inductance value can be given in our order data sheet or can be calculated by us from active part dimensions and number of turns. For more information, see IEC 60214-2 or product information 5492 0031-100.

If values higher than acceptable for UC tap-changers are obtained, the VUC tap-changer is an alternative since it withstands higher values.

Fig. 22. Rated phase step voltage for type UCG. Fig. 23. Rated phase step voltage for type UCL.

Fig. 25. Rated phase step voltage for type UCD.Fig. 24. Rated phase step voltage for type UCC.

UCG.N,B

UCC.N For higher values contact ABB

UCD.N For higher values contact ABB

UCL.N,B

UCG.E,T

UCC.E UCD.E

UCL.E,T

Ste

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olta

ge

(V)

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(V)

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p v

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(V)

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p v

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(V)

Rated through-current (A)

Rated through-current (A) Rated through-current (A)


UCG.N,B,E,Tshort version

UCG.E,Tshort version


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Contact lifeThe predicted contact life of the fixed and moving contacts of the diverter switch, are shown as a function of the rated through current in the diagrams below. It is based on the type test with 50,000 switching operations, and a current corresponding to the maximum rated through current. The contact life is stated on the rating plate.

Fig. 26. Contact life for type UCG. Fig. 27. Contact life for type UCL.

Fig. 28. Contact life for type UCC. Fig. 29. Contact life for type UCD.

UCG.N,B 100% load

UCC.N 100% load

UCL.N,B 100% load

UCDL.N 100% load

UCG.E,T 100% load

UCC.E 100% load

UCL.E,T 100% load

UCD.E 100% load

80% average load

80% average load

80% average load

80% average

load

80% average load

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nsN

o. o

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ions

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Standards and testingThe on-load tap-changers made by ABB fulfill the requirements according to IEC 60214-1, and IEEE C57.131-1995.

The type tests include:

– Contact temperature rise test – Switching 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 test – Vacuum test – Final inspection

Fig. 30. Example of rating plate.

Rating plate


a2

a1

b1

b2e1

g1

b1

a2 a1

b1

b2e1

g1

b1

a2 a1 f1

d1

b2

g2

e1

g1

b1

c1

f2

d1

Insulation levelsLI is the lightning impulse (1.2/50 µs). pf is the power frequency test voltage (60 s). The insulation levels are indicated as impulse withstand voltage – power frequency withstand voltage.

The tests were carried out according to IEC 60214-1, with a new tap-changer and clean insulation transformer oil I -30 °C according to IEC 60296. The withstand voltage value of the oil was higher than 40 kV/2.5 mm (IEC 60156).

Insulation levels to earth (g1 and g2)For UCG and UCL 380-150 kV, 650-275 kV, 750-325 kV

and 1050-460 kVFor UCC and UCD 380-150 kV, 650-275 kV and

1050-460 kV

Lightning impulse levels (LI) and power frequency levels (Pf) correspond to the following Um-values acc. to IEC:

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

380 150 72.5 1)

650 275 145

750 325 170

1050 460 300

Table 4.1) Covers 76 kV that is not an IEC value.

a1 Between any electrically adjacent contacts in the tap selector, not connected.

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

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 selector (coarse/fine switching)

e1 Between preselected tap and connected tap of one phase in the diverter 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 fine winding.

g1 Connected tap to earthg2 Pre-selected tap to earth

Fig. 31. Linear switching (L).

corresponding contact in adjacent phase

Fig. 32. Reversing switching (R).

corresponding contacts in adjacent phase

Fig. 33. Coarse/Fine switching (D).

corresponding contacts in adjacent phase


Withstand voltagesUCG with tap selector CAll values given as 1.2/50 µs impulse withstand voltage (kV) – power frequency withstand voltage (kV).

a1 is not valid since the contact locations are such that electrically adjacent contacts are never physically adjacent, see connection diagrams in this document.

Type of

switching

No. of

positions

Within one phase Between phases for neutral point

a2 c1 f1 f2 e1 b2 b1 d1

L -14 350-140 400-150 400-150 400-150 100-20 100-20 400-150 400-150

L 15-16 290-120 350-140 350-140 350-140 100-20 100-20 300-125 350-140

L 17-18 250-95 350-140 350-140 350-140 100-20 100-20 300-125 350-140

R -13 350-140 400-150 400-150 400-150 100-20 100-20 400-150 400-150

R 14-15 250-95 350-140 350-140 350-140 100-20 100-20 300-125 350-140

R 16-27 350-140 400-150 400-150 400-150 100-20 100-20 400-150 400-150

R 28-31 290-120 350-140 350-140 350-140 100-20 100-20 300-125 350-140

R 32-35 250-95 350-140 350-140 350-140 100-20 100-20 300-125 350-140

D -13 350-140 400-150 400-150 400-150 100-20 100-20 400-150 400-150

D 14-15 250-95 350-140 350-140 350-140 100-20 100-20 300-125 350-140

D 16-27 350-140 400-150 400-150 400-150 100-20 100-20 400-150 400-150

D 28-31 290-120 350-140 350-140 350-140 100-20 100-20 300-125 350-140

D 32-35 250-95 350-140 350-140 350-140 100-20 100-20 300-125 350-140

Table 5. Withstand voltages, UCG with tap selector C.

UCG with tap selector III unshielded versionAll values given as 1.2/50 µs 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

Table 6. Withstand voltages, UCG with tap selector III unshielded version.


UCG with tap selector III shielded versionAll values given as 1.2/50 µs 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 - - - 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

Table 7. Withstand voltages, UCG with tap selector III shielded version.

UCL with tap selector III unshielded versionAll values given as 1.2/50 µs 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

Table 8. Withstand voltages, UCL with tap selector III unshielded version.


UCL with tap selector III shielded versionAll values given as 1.2/50 µs 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

Table 9. Withstand voltages, UCL with tap selector III shielded version.

UCD with tap selector III unshielded versionAll values given as 1.2/50 µs 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 - - - 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

Table 10. Withstand voltages, UCD with tap selector III unshielded version.


UCD with tap selector III shielded versionAll values given as 1.2/50 µs 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 - - - 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

Table 11. Withstand voltages, UCD with tap selector III shielded version.

UCC with tap selector IVAll values given as 1.2/50 µs impulse withstand voltage (kV) – power frequency withstand voltage (kV).

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 - - - 200-20 200-20 300-125 -

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

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

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

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

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

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

R s 28-35 200-80 400-150 - - - 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

Table 12. Withstand voltages, UCC with tap selector IV.


Short-circuit current strengthThe short circuit current strength is verified with three applications of 2 or 3 seconds duration, without moving the contacts between the three applications. Each application has an initial value of at least 2.5 times the rms value.

Diverter switch Tap selector Max rated through-current,

A rms

Type of connection 2 s duration, kA

rms

3 s duration, kA

rms

Peak value, kA

UCG C 300, 400 N,B 6 6 15

C 500, 600 N,B,E,T 6 1) 6 1) 15

C 900, 1200 E,T 12 1) 12 1) 30

C 1500 E,T 18 18 45

C 1800 3) E,T 18 18 45

III 300, 400 N,B 8 8 20

III 500, 600 N,B,E,T 8 1) 8 1) 20

III 900 E,T 12 12 30

III 1200, 1500 E,T 20 20 50

III 1800 3) E,T 20 20 50

UCL III 600 N,B,E,T 11 1) 11 1) 27,5

III 900, 925 N,B,E,T 11 1) 11 1) 27,5

III 1800 E,T 24 24 64

III 2400 E,T 27 27 67,5

III 2700 3) E,T 33 33 82,5

UCD III 1000 N,E 12 12 30

III 1600 E 18 18 2) 45

UCC IV 1600 N,E 18 18 2) 45

Table 13.1) In case of UC..E,T higher values are possible on request.2) Available for reinforced performance with 24 kArms and 60 kApeak. Maximum rated through current is then reduced to 1500 A.3) Requires enforced current splitting during operation. See section Enforced current splitting.

Highest phase service voltage across the regulating winding The table below show the highest permissible phase service voltage for the different types of connections.

Across the regulating winding

(kV)

Across the coarse and fine

winding (kV)

Contact shieldings: with without with without

Tap-changer,

tap selector

UCG.N C - 35 - 40

UCG.N III 1) 52 35 75 45

UCL.N III 1) 52 35 75 45

UCD.N III 1) 52 35 75 45

UCC.N IV 52 35 75 45

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

UCG.T, E, B III 1) 68 45 80 60

UCL.T, E, B III 1) 68 45 80 60

UCD.E III 1) 68 45 80 60

UCC.E IV 68 45 80 60

Table 14. Highest permissible phase service voltage across the regulating winding.

1) Higher values available on request. Please contact ABB.


Rated through-currentThe rated through-current of the tap-changer is the current which the tap-changer is capable of transferring from one tapping to the other at the relevant rated step voltage, and which can be carried continuously whilst meeting the technical data in this document. The rated through current is normally the same as the highest tapping current. The relation between rated through-current and step voltage is shown in Figs. 22 - 25. The rated through-current determines the dimensioning of the transition resistors and the contact life. The rated through-current is stated on the rating plate, Fig. 30.

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

To meet these requirements, the UC models have been designed so that the contact temperature rise over the surrounding oil does not exceed 20 K when loaded with a current of 1.2 times the maximum rated through current of the tap-changer.

The contact life stated on the rating plate is given with the consideration that currents of a maximum 1.5 times the rated through current occur in a maximum of 3 % of the tap-change operations. Overloading beyond these values, results in increased contact wear and shorter contact life.

For more information about overloading, read the appropriate parts of IEC 60214-2.

Oil temperatureProvided that insulating oil of class “Transformer oil -30 °C” according to IEC 60296, is used, the temperature of the oil surrounding the tap-changer shall be between -25 and +105 °C for normal operation, as illustrated below. The range for UC can be extended to -40 °C provided that the viscosity does not exceed 2500 mm2/s (=cst).

Alternative insulating liquidsIndividual brands need to be evaluated from case to case because of the differences in viscosity compared to transformer grade mineral oil and the subsequent difference in heat dissipation. Also dielectric strengths and influence from moisture needs to be considered. Switching in vacuum generally opens for use of a wider range of insulating fluids.

1. No operations allowed.2. Emergency overloading. The tap-changer will

not restrict the occasional overloading of the transformer according to the standards stated in section Occasional overloading.

3. Normal operating range.

4. When operating within this range, no overloading is allowed.

5. No operation allowed.

Fig. 34. Oil temperature.


Coarse/fine regulation leakage inductance switchingWhen changing from the end of the fine winding to the end of the coarse winding, a high leakage inductance can be set up with the two windings in series. The critical moment occurs at switching the tap-changers mechanical mid-position, as the circulating current passes through not only one loop but also the entire coarse and fine tap winding.

The leakage inductance that occurs from one loop, Fig. 35, is neglegible but can be substantial from the complete coarse and fine winding, Fig. 36.

This leakage inductance causes a phase shift between switching current and recovery voltage that makes the breaking more severe. The tap-changer must be dimensioned accordingly. The leakage inductance shall be specified in the ordering data sheet.

For certain winding configurations, such as coarse and fine windings located axially, this value might be so high that it requires a larger tap-changer than would be needed otherwise. In general, vacuum type tap-changers are less sensitive to this and might be an alternative for high values of leakage inductance. For more information, see IEC 60214-2, or consult the supplier for advice.

Main winding

Main winding

Coarse winding

Coarse winding

Fine winding

Fine winding

Fig. 35. Normal operation. Fig. 36. Operation with high leakage inductance.

Tie-in resistor and tie-in resistor switchWhen the change-over selector operates, the tapped winding is disconnected for a short time. The voltage of that winding is then determined by the voltage of, and the capacitances to, the surrounding windings or tank wall/core. For certain winding layouts, voltages and capacitances, the capacitive controlled voltage will reach magnitudes that are too high for the change-over selector. In these cases potential controlling resistors, so called tie-in resistors, should be connected according to Fig. 37.

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

The tie-in resistors are normally mounted separately from the tap-changer but can be mounted underneath the tap selector provided that tie-in resistor switch is not used. Please contact the supplier for advice in such cases!


HV

C1

RW

C2

+ -

UH1

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

Tap selector Max recovery voltage

(kV rms)

Max capacitive current

(mA rms)

C 35 200

III 35 300

IV 35 300

Table 15.

The capacitive current is the current going through the change-over selector before it opens.

In Fig. 37 there is a switch, the tie-in resistor switch, which connects the tie-in resistors only when they are needed. The switch is a part of the tap selector and is mounted on the bottom plate of the tap selector, see dimension 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-in resistor switch is available for all tap selectors except tap selector C.

When ordering, give the winding layout and information according to the example in Fig. 38 and Table 16, and the supplier will calculate whether tie-in resistors are needed or not. If needed, the supplier will choose the correct tie-in resistors. When a tie-in resistor switch is needed to limit the no-load losses, give that information in the ordering data sheet. If anything is unclear, contact the manufacturer.

Winding Phase voltage Connection

High voltage (HV) 132 kV (H1) Delta

Regulating winding (RW)

(Voltage across)

13.2 kV (U) Plus/Minus

Table 16. Example of winding layout and information.

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

Diverter switch

Tie-in resistor switch

Tie-in resistor

Tap selector

Main winding

Regulating winding with change-over selector

Fig. 37. Tie-in resistor example.

Tank

Fig. 38. Example of winding layout and information.


Installation and maintenance

Tap-changerInstallationThe tap-changers can be delivered for cover-mounting or yoke-mounting onto the transformer. For detailed installation instructions, consult the appropriate Installation and commissioning guide.

DryingThe tap-changer must be stored indoors and left in its plastic shipping cover until time for assembly. The tap-changer should be subjected to drying before taken into service. The diverter switch should not participate in the drying process. For further instructions refer to the Installation and commissioning guide.

WeightsThe tables below show all the weights of the UC range of tap-changers.

On-load tap-changer

type designation

Approximate weight in kg

Tap-changer

without oil1)

Required

oil

Total

UCG.N 2) 380-750/300-600 425 185 610

1050/300-600 435 230 665

UCG.T 2) 380-750/500-900 1080 3x185 1635

380-750/1200-1500 1230 3x185 1785

1050/500-900 1110 3x230 1800

1050/1200-1500 1275 3x230 1965

UCG.B 2) 380-750/300-600 750 2x185 1120

1050/300-600 770 2x230 1230

UCG.E 2) 380-750/500-900 360 185 545

380-750/1200-1500 410 185 595

1050/500-900 370 230 600

1050/1200-1500 425 230 655

Table 17. Weights for type UCG.1) The weight of the diverter switch, approximately 90 kg, is included.2) If tap selector III is used, add 100 kg to the weight without oil.

On-load tap-changer

type designation


Tap-changer

without oil1)

Required

oil

Total

UCL.N 380/600, 900, 925 480 260 740

650/600, 900, 925 500 300 800

1050/600, 900, 925 510 340 850

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, 925 850 2x260 1370

650/600, 900, 925 890 2x300 1490

1050/600, 900, 925 910 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

Table 18. Weights for type UCL.1) The weight of the diverter switch, approximately 120 kg, is included.

On-load tap-changer

type designation


Tap-changer

without oil1)

Required

oil

Total

UCD.N 380/1000 900 700 1600

650/1000 940 760 1700

1050/1000 960 860 1820

UCD.E 380/1000 840 700 1540

380/1600 870 700 1570

650/1000 880 760 1640

650/1600 910 760 1670

1050/1000 900 860 1760

1050/1600 930 860 1790

Table 19. Weights for type UCD.1) The weight of the diverter switch, approximately 250 kg, is included.


On-load tap-changer

type designation


Tap-changer

without oil1)

Required

oil

Total

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

Table 20. Weights for type UCC.1) The weight of the diverter switch, approximately 250 kg, is included.

Oil filling For details of oil filling, consult the appropriate Installation and commissioning guide.

MaintenanceMaintenance is normally carried out after 1/5 of the contact life or every 7th year, whichever comes first. For more information, consult the appropriate Maintenance guide.

PressureDuring drying, the tap-changers should have no pressure difference to the transformer. This is obtained by opening the vapor phase (VP) valve in the bottom, see the Installation and commissioning guide for further information.

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

The pressure difference to the transformer tank during oil filling and testing is allowed to be max 100 kPa. During service, it is recommended that the pressure be as low as possible and not more than 50 kPa and then preferably higher in the transformer tank. For higher pressures, contact the supplier.

Accessories and protection devicesThe tap-changer can be equipped with various protection devices. The standard protection device is the pressure relay. An oil flow relay is also available.

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

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

Motor-drive mechanismDesignFor detailed design description, see separate Technical guides for motor-drive mechanisms types BUE or BUL, respectively.

InstallationThe motor-drive mechanism is fitted to the outside of the transformer tank, and connected to the tap-changer by drive shafts and bevel gears. For the correct installation procedure, consult the appropriate Installation and commissioning guide.

MaintenanceThe motor-drive mechanism should be visually inspected annually. For the correct inspection and maintenance procedures, consult the appropriate Maintenance guide.

Operating shaftsLength L1 (mm) L2 (mm) L3 and L4

(mm)

Motor-drive

mechanism

Min/max 500/3100 525/3100 900/2700 BUE2/BUE3

500/3100 600/3100 – BUL/BUL2

Table 21.

The minimum and maximum lengths refer to mechanical design only. For L2 vertical shaft see the dimension prints on the following pages. Other shaft arrangements are available on request.

For standard shaft arrangements, the maximum angle (totally in two directions) is 4°. For larger angles, order design is required.

For single units (UC..E, N) the gear box of the tap-changer might be mounted at the angle given in Fig. 39. The angle must be stated when ordering.

Fig. 39. Mounting angle, single unit

Permitted range

0°

a

-10°190°


Fig. A

L1

UCG.N, E

UCL.N, E

UCD.N, E

UCC.N, E

Fig. B

L1

Fig. C

L3 L1

UCG.B

UCL.B

Fig. D

L1 L3

Fig. E

L4 L3 L1

UCG.T

UCL.T

Fig. F

L1 L3 L4

Fig. 40. Positioning of motor-drive mechanism.


Fig. 41. Dimensions, type UCG/C.

C/L Tap selector C/L Diverter switch

Section A – APlus/Minus andCoarse/Fine switching

Section A – ALinear switching

80

R210

570

570

615D=420

615

R210

L2

2907)

L1H32)

A A

205

D=600

D=470

345

30

H2

70

4057)

1)

1)

D=420

332

D=740

111

16O

H1

DimensionsDimensions in mm. The design, technical data and dimensions are subject to alteration without notice. For more information, see the dimension drawings.

Dimensions for motor-drive mechanism, see Fig. 49.

Type UCG.N and type UCG.E


Fig. 42. Dimensions, type UCG/III.

Model for mounting on transformer’s 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)1)

1)

For tap

selector

size

Impulse withstand

voltage to earth (kV)

H1

(mm)

H1,

short

version

(mm)

H3 2)

(mm)

H3 2),

short

version

(mm)

C 380, 650, 750 1192 972 1400 1200

1050 1492 1272 1700 1500

III 380, 650, 750 1354 1134 1400 1200

1050 1654 1434 1700 1500

Table 22. Diverter switch housings UCG.

For tap-changer

type

Max rated through-

current (A)

H2, size C

(mm)

H2, size III

(mm)

UCG.N 300-600 959 1160

UCG.E, UCG.T 5) 500-600 519 552

UCG.E, UCG.T 900 739 552

1200 739 856

1500 959 856

UCG.B 6) 300-600 Single-phase

unit 519

Two-phase

unit 739

Single-phase

unit 552

Two-phase

unit 856

Table 23. Tap selectors for UCG.

1) Shielding rings are used only for insulation levels 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 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 for UCL.B.7) Space required for protective equipment.


Fig. 43. Dimensions, type UCL/III.

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

Section A – APlus/Minus andCoarse/Fine switching

Section A – ALinear switching

3017)

1)

1)

4808)



Fig. 44. Dimensions, type UCL/III.

Design for premounting on the active part of the transformer

Type UCL.B (three-phase, delta)

4)

4)

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

380 1415 1500

650 1615 1700

1050 1815 1900

For mounting on active part 5) H1+85 H3+100

Table 24. Diverter switch housings UCL.

For tap-changer

type

Max rated through-

current (A)

H2, size III (mm)

UCL.N 600-900 1160

UCL.E, UCL.T 5) 600-900 552

1800 856

2400 1160

UCL.B 6) 600-900 Single-phase unit H22

= 552

Two-phase unit H21

= 856

Table 25. Tap selectors for UCL.

1) Shielding rings are used only for insulation levels 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) UCL.T consists of three single-phase units.6) UCL.B consists of one single-phase unit and one two-phase unit.7) Space required for protective equipment.


Fig. 45. Dimensions, type UCD/III.

2046)

7886)


1)

1)

1)


Fig. 46. Dimensions, type UCD/III.


380 1594 1700

650 1734 1900

1050 1934 2200

Table 26. Diverter switch housings UCD.

For tap-changer type Max rated through-

current (A)

H2, size III (mm)

UCD.N 1000 1160

UCD.E 1000 552

1600 856

Table 27. Tap selectors for UCD.

1) Shielding rings are used only for insulation levels 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 the insulation distance required.

6) Space required for protective equipment.


Fig. 47. Dimensions, type UCC/IV.


1)

1)

1)

2)


Fig. 48. Dimensions, type UCC/IV.


380 1540 1700

650 1680 1900

1050 1880 2200

Table 28. Diverter switch housings UCC.

For tap-changer type Max rated through-

current (A)

H2, size III (mm)

UCC.N 1600 1522

UCC.E 1600 1282

Table 29. Tap selectors for UCC.

1) Shielding rings are used only for insulation levels 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 340 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 the insulation distance required.


49

1274 1197

37

45

79

383

626475

202

75

213

408

BUL2 BUL BUE2

Fig. 49. Dimensions, motor-drive mechanisms.

145246

353174

230366

134

520

440258

818

532

194

128

36

10

75

115 157

157

390

308


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

1. The breathing device should prevent moisture from getting into the tap-changer compartment and allow gases from the arcings out.

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

3. X corresponds to a height giving a max recommended pressure difference between the tap-changer tank and the transformer tank of 50 kPa.

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

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

6. Vacuum proof conservator if the tap-changer should be oil filled under vacuum with the conservator mounted.

Note that separate oil conservators for the transformer and the tap-changer are recommended. Both oil and air side should be separated. For transformers with a common conservator for both the transformer and the tap-changer, a filter should be mounted in the pipe from the tap-changer to the conservator.

Fig. 50.


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

Appendices: Single-phase diagrams

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

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

9 steps

Number of loops:

9


10

10 steps

Number of loops:

10 5 5 + 5


11 11 11



11 steps

Number of loops:

11


12

12 steps

Number of loops:

12 6 6 + 6


13 13 13

13 steps

Number of loops:

13


14

14 steps

Number of loops:

14 7 7 + 7


15 15 15



15 steps

Number of loops:

15


16

16 steps

Number of loops:

16 8 8 + 8


17 17 17

17 steps

Number of loops:

17

Number of tap positions

18

18 steps

Number of loops:

10 9 + 10


19 19



20 steps

Number of loops:

10 10 + 10


21 21

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



28 steps

Number of loops:

14 14 + 14


29 29

30 steps

Number of loops:

16 15 + 16


31 31

32 steps

Number of loops:

16 16 + 16


33 33

34 steps

Number of loops:

18 17 + 18


35 35


Appendix 2: Single-phase diagrams for UCG/III, UCL/III and UCD/III


4 steps

Number of loops:

4


5

5 steps

Number of loops:

5


6

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

9 steps

Number of loops:

9


10

10 steps

Number of loops:

10 5 5 + 5


11 11 11

11 steps

Number of loops:

11


12



12 steps

Number of loops:

12 6 6 + 6


13 13 13

13 steps

Number of loops:

13


14

14 steps

Number of loops:

14 7 7 + 7


15 15 15

15 steps

Number of loops:

15


16



16 steps

Number of loops:

16 8 8 + 8


17 17 17

17 steps

Number of loops:

17


18

18 steps

Number of loops:

18 10 9 + 10


19 19 19

19 steps

Number of loops:

19


20



20 steps

Number of loops:

20 10 10 + 10


21 21 21

21 steps

Number of loops:

21


22

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

28 steps

Number of loops:

14 14 + 14


29 29

30 steps

Number of loops:

16 15 + 16


31 31

32 steps

Number of loops:

16 16 + 16


33 33



34 steps

Number of loops:

18 17 + 18


35 35


Appendix 3: Single-phase diagrams for UCC/IV


8 steps

Number of loops:

8 4


9 9

9 steps

Number of loops:

9


10

10 steps

Number of loops:

10 5


11 11

11 ateps

Number of loops:

11


12

12 steps

Number of loops:

12 6


13 13



13 steps

Number of loops:

13


14

14 steps

Number of loops:

14 7


15 15

15 steps

Number of loops:

15


16

16 steps

Number of loops:

16 8 8 + 8


17 17 17

17 steps

Number of loops:

17


18



18 steps

Number of loops:

10 9 + 10


19 19

20 steps

Number of loops:

10 10 + 10


21 21

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

28 steps

Number of loops:

14 14 + 14


29 29

30 steps

Number of loops:

16 15 + 16


31 31

32 steps

Number of loops:

16 16 + 16


33 33

34 steps



Number of loops:

18 17 + 18


35 35

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