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ESSEX ITALY SpA

CONTINUOUSLY TRANSPOSED CONDUCTORS

ISO 9001-2000 CERTIFICATE CSQ 9125.PIR9 IQNET IT-8970

29.1.2008

ESSEX ITALY SpA Continuously Transposed Conductors – Ed. 3 Rev. 1 29.1.2008

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inside .....

CONTINUOUSLY TRANSPOSED CONDUCTOR 3

PAPERLESS TRANSPOSED CONDUCTOR 4

CORDEX DIMENSIONAL PROPERTIES 5

CORDEX – TYPES OF SPECIAL ARRANGEMENTS 6

CONTROLLED PROOF STRESS COPPER STRAND RANGE 7

ENAMELLED RECTANGULAR WIRES 7

EXTERNAL SPECIAL PAPERS INSULATION 8

BONDING PROPERTIES 9

CTC DATA SHEET 10

CTC DIMENSIONAL DATA 11

MINIMUM WINDING DIAMETER AND TRANSPOSING PITCH 12

DRUMS FOR TRANSPOSED CONDUCTORS 14

ORDERING 14 This information was prepared to help users in selecting the proper material. We supply this information without representation or warranty of any kind. ESSEX ITALY SpA therefore assumes no responsibility and shall have no liability of any kind arising from the supply or use of this information. ESSEX ITALY SpA reserves the right to change this information or to stop the production of its materials without notice. Errors and omissions excepted.


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CONTINUOUSLY TRANSPOSED CONDUCTOR ESSEX ITALY Continuously Transposed Conductor consists of a group of enamelled rectangular wires, generally of FORMVEX or FORMICEMENTEX type, which are connected up parallel to the ends. In this group each strand successively and repeatedly takes on every possible position inside the whole conductor cross-section. The strands as a whole are wrapped generally with pure cellulose paper tapes. This conductor is used for manufacturing low losses windings for electric machines. The number of component strands includes all numbers between 5 and 85, though an odd number can give a greater cross-section for the same stack size. Up to 32 paper tapes are applied as external insulation and this permits any increase of the overall insulation between 0.8 and 6 mm. Transposed Conductors of pure copper, special copper alloys or aluminum are available, both with controlled proof stress bondable FORMICEMENTEX strands for short circuit resistant windings. For dry transformers TENVEX enamelled strands insulated with polyaramid paper are generally used. For special purposes are manufactured CTC without papers with wound monofilament. The growth of the power of electrical machines has increased the need of more efficiency. Regarding the different losses in the transformer, the use of CTC windings has improved this important property of transformers design. The adoption of CTC brings great advantage in reduction of eddy current losses, particularly at the end of the winding. In addition it is possible to have a considerable increase in the space factor of the winding, due to the very small thickness of the insulation of the single conductors and getting a more uniform distribution of the temperature throughout the whole winding. Using CTC, it is important to take into account the increase in temperature of windings due to the higher filling factor and the less uniform external paper insulation than that obtained with coils wound with paper-insulated rectangular conductors, thus restraining in such manner the oil flow. The increased power demand on the transmission and distribution networks gave rise to an increase in the short circuits power due to their interconnection, particularly in countries without stable network and low impedance constructions. The effects of short circuits due to this fact were intensified and many transformers broke down because of their inability to withstand to electrodynamic stresses. In response to these problems ESSEX ITALY developed the use of FORMICEMENTEX CPR3 in CTC and the special CORDEX (paperless CTC). Epoxy bonded Transposed Conductors are made covering the enamelled rectangular wires with special epoxy resins at B-stage (Formicementex wire). This technique enables the user to strongly bond together the conductors in the same standard thermal treatment used for drying the paper insulation of the windings.

Advantages • Transformers improve against unstable electrical

network and the risks of shorts. • Formicementex enamelled rectangular wires used

in Transposed Conductors provide exceptionally strong bond strength in the winding.

• Conductors in the winding become like a solid beam and can withstand strong electrodynamic stresses created during short circuit event.

• No special treatment is needed by the user. FORMICEMENTEX CPR3 CTC is characterised by the following properties: • Copper with high mechanical characteristics

(generally CPR3 with a proof stress 0.1 % of 220÷260 MPa) - in order to withstand the electrodynamic stresses in case of short circuits.

• Rectangular wires enamelled with special polyvinylformol enamels resistant to transformer oils.

• Epoxy coating over the enamelled rectangular wires (FORMICEMENTEX) - a thin layer of tack-free cresol-free epoxy B-stage that bond the strands together after the thermal treatment of the winding, getting a solid monolithic winding in order to withstand the electrodynamic stresses in case of short circuits.

• Wrapping the transposed conductors by special insulation papers (thermally upgraded calendered crepe paper) internally in contact with the strands and externally, in order to give the best geometry (well defined oil ducts) allowing good cooling performance of the transformers or in some helical coil constructions without paper (paperless technique).

Other constructions can be made with individual CTC Customers in order to improve particular performances required for the winding.


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PAPERLESS TRANSPOSED CONDUCTOR1 Our CORDEX is the best paperless CTC for transformers windings. Materials and production methods offer the best thermal exchange between the conductor and the oil, with the lowest presence of foreign substances. These properties allow the maximum efficiency and durability. CORDEX CTC is a special TRANSPOSED CONDUCTOR without insulation paper but just with a transformer oil resistant polyester monofilament, wrapped around it. The ESSEX ITALY paperless CTC has been designed with the intent to reduce transformer production costs. Main advantages a) No bulging of the paper b) CTC free from oil pocket among the windings c) Better cooling efficiencies – reduction of heat resistance between 4 and 7°C/W d) Better space factor of the windings allowed by a reduction of the oil ducts from 5-6 mm to 2

mm. e) Smaller O.D. of the transformer with the same section in a smaller space, getting possible to

design one radial winding instead of two. f) Better working productivity due to the improving in winding time depending on the design. g) Finally more efficient transformers, smaller for the same power; from 1 to 3% of the total

transformer cost, also for less copper inside (approx. 10 ton for 600 MVA). The absence of paper, which is subject to bagging, allows a reduction of need of space for the oil channel and hence the space between turns by 25-33%. The low friction coefficient improves the oil circulation. This allows the overall size of the winding to be reduced with consequent saving in material cost. The absence of paper, in low voltage windings, and the reduced quantity of polyester monofilament around the bundle improves the heat dissipation, so reducing the cost for cooling the transformer (for example by allowing smaller radiators). This configuration gives the best mechanical performances and reliability together with low transformer oil pollution in comparison with competitors. This CTC is reducing the winding time, improving productivity. This design allows a reduction on cable length (less scrap). The CTC design is generally considered for helical winding up to 125 kVp, especially for low voltage windings. The Transposed Conductor is wound with one or more oil-resistant plastic monofilaments (generally 2 or 3 wires close together in two directions). Papers can be set on one side in order to allow the direct contact of the CTCs of sequential winding turns. A protection paper is given in order to avoid contamination and it is easily removed just before the winding point, pulling a plastic wire inserted along the Transposed Conductor. An adhesive tape keeps together the pieces of the cut sacrifice paper.

1 Patent IT01290307 WO9836431 EP859381


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CORDEX dimensional properties Plastic monofilament covering: polyester monofilament (generally 2 or more cross polyester monofilaments, depending on the CTC size). For Rp0.2 % proof stress copper greater than 200 MPa or CTC with more than 35 strands the covering is usually with 6 crossed polyester monofilaments, three wires close together for each direction, in order to improve the contact surface, increasing the mechanical strength (see picture). Calculation of the axial and radial dimension is done according to the following formulas: Dimension in axial direction:

( ) ( ) TOLLcHicipihkH ±+++Ε+××= 2 Tolerance ± 0.15 mm

n k iC iP cH 11 - 85 1.01 0.45 0.10- 0.30 0.15 b ≥ 2.10 mm h ≥ 9.30 mm k= 1.02 Dimension in radial direction

( ) ( ) ( ) TOLLDnXcBicibnkB ±++++⎥⎦

⎤⎢⎣

⎡Ε+×⎟

⎠⎞

⎜⎝⎛ +

×=2

1' Tolerance ± 0.50 mm

for strands with h ≤ 6.0 mm tolerance is + 0.30 mm – 0.80 mm

n K' iC cB nX D 11 - 21 1.04 0.45 0.15 0.13 0.15 23 - 27 1.035 0.45 0.15 0.13 0.15 29 - 37 1.03 0.45 0.15 0.13 0.15 39 - 49 1.025 0.45 0.15 0.13 0.15 51 - 85 1.015 0.45 0.15 0.13 0.15 Where: H = Axial cable dimension (100 N/cm²); B = Radial cable dimension (100 N/cm²) h = Axial strand dimension; b = Radial strand dimension k = 1.01 Axial shape factor (for b > 2.10 mm and h > 9.30 mm k =1.02) k’ = Radial shape factor (values in table ) n = Number of strands in the cable iE = Increase in dimensions due to enamel (typical values: 0.12 mm for enamelled strands and 0.17 mm for

enamelled + epoxy coated strands) ip = Thickness of separator between the strands stacks (0.10 up to 0.30 mm according to Customer requirements) ic = plastic wire covering (typical 1.06 x 0.36 mm - 0.45 mm thickness after 1 N/mm² pressure) cH = side separator ( 2 calendered crepe papers 0.075 mm ) TOLL = tolerance (axial or radial ) cB = top or bottom separator ( 2 calendered crepe paper 0.075 mm ) nX = adhesive aramid tape - bottom side ( 0.13 mm ) Note: if an aramid tape is required on the CTC bottom side, 2 calendered crepe papers are placed between the

strands and the cordex wire. ( nX + cB ) Please take note that during the measuring under pressure there is a penetration of the plastic monofilament in the spacer. Then the axial measure is reduced by 0.25-0.30 mm. There is no experience for cordex CTC less than 11 strands.


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CORDEX – types of special arrangements Cordex is available with the following arrangements:

ARRANGEMENT APPLICATION PROPERTIES PIC.

CORDEX only with protection paper

LV winding See page 4

CORDEX1 with 2 layers papers at the bottom in radial dimension

LV winding when its better to split CTC in two due to the big radial dimension

With the same single width of the strand it is possible to reach very high radial dimension

1

CORDEX2 with 2 layers papers in axial dimension

Layer winding It is possible to increase the cooling, reducing spaces

2

CORDEX3, same as CORDEX1 plus aramid paper at the bottom in radial dimension for easy winding (only for width greater than 11 mm - this paper has a cold stick acrylic adhesive)

LV and HV disk winding Increasing cooling reducing spaces in LV and HV

3

For the right use of these products please contact our Technical dept. Picture 1

Picture 2

Picture 3


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CONTROLLED PROOF STRESS COPPER STRAND RANGE The single strand is generally E-Cu58 copper but can be also produced in aluminium and silver bearing copper. When cold worked, the required minimum yield strength will be on the order document with a tolerance of

Minimum yield strength range

Tolerance MPa

60-(130) + 30 130-160 + 50

> 160 + 30 MPa or + 20% which ever is higher or it can be produced according to EN 13601:2002 (CPR Rp0.1% designation) or to other designation (Rp0.2%):

In bold compulsory values Maximum Rp0.2% is 280 MPa.

1

2

3

4

2 4 6 8 10

b (mm)

h (mm)

12

transposable strand range

preferred range for 33 to 85 strands

h/b <2.5

h/b >6 5

Controlled proof stress

copper

EN 13601 designation

Rp(0.2%) Typical

MPa annealed R200 60-100 CPR05 R200 90-120

CPR05/1 ------ 120-150 CPR1 R230 150-210 CPR2 R250 180-230 CPR3 R280 230-280

CuAg 0.1 Check availability

ENAMELLED RECTANGULAR WIRES

DESIGNATION TYPE OF ENAMEL GRADE INCREASE IN DIMENSIONS

(mm) FORMVEX Polyvinylformol resins 1

2 0.09 ± 0.02 0.12 ± 0.03

TENVEX 200 Polyesterimide+polyamideimide resins 1 2

0.09 ± 0.02 0.15 ± 0.03

FORMICEMENTEX polyvinylformol + B-stage epoxy resins 1 2

0.13 ± 0.03 0.17 ± 0.03

IEC 60317-0-2 increase in dimensions are considered under Customer request. B-stage epoxy coating 0.03-0.05 mm allows good adhesion of the strands for treatment at (120±10)°C 24 h for storage at temperature not greater then 32°C up to 8 months (or up to 6 months for treatment at (110±10)°C 48 h). Good bonding is achieved in Lab specimens after treatment at (130±10)°C for 16 hours or (120±10)°C for 24 hours or (110±10)°C for 48 hours. Industrial treatment conditions should be defined after practical tests. Grade1 is considered if not otherwise specified in the order. IEC 60851 test methods, IEC60317-0-2 General Requirements, IEC 60317-18 (Formvex and Formicementex), IEC 60317-28 (Tenvex H) and IEC 60317-29 (Tenvex 200), if not otherwise specified in the order.


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EXTERNAL SPECIAL PAPERS INSULATION TYPE OF PAPER RECOMM.

THICKNESS (µm)

APPLICATIONS MAIN PROPERTIES

Kraft 65 - 80 general purposes high purity 5A2-1M3 High density 110 general purposes high Tgδ, high density and dielectric strength High density thermally upgraded crepe

75 inner and outermost layers (*)

high mechanical and thermal properties

Thermally upgraded paper

65 - 80 - 105 - 130

inner and outermost layers (*)

high thermal properties

Epoxy coated kraft 75 inner and outermost layers

bonding purposes and reducing bagging effect

Aramid paper 50 thermal class 200 high temperature resistant PET film 50 Gas transformers Glass fabric tape 120 external protection Monofilament 450 paper-less application No bulging of the paper; CTC free from oil

pocket among the windings; better cooling efficiencies; better space factor of the windings; smaller transformer O.D.

(*) also for general purposes All papers for electrical applications according to IEC 60554. Other types of papers are available on request Papers arrangement Unless otherwise agreed with Customer, the insulation shall consist of at least three layers of 80 µm kraft paper. The paper covering shall be applied according to the following arrangement or according to Customer request: • Papers are wound • up to 8 papers, in the same direction • above 8 papers, in opposite direction, in groups of maximum 8 papers.

• The inner layers papers shall be butt lapped and staggered from 25 to 40 %. The two outmost layers shall be wound interlocked by 50%.

Agreement with the Customer will be required in case of change of thickness of one or more papers or the type of arrangement, in order to reach the required paper insulation thickness.


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BONDING PROPERTIES Epoxy bonded Transposed Conductors are made covering the enamelled rectangular wires with special epoxy resins at B-stage (Formicementex wire). This technique enables the user to strongly bond together the conductors in the same standard thermal treatment used for drying the paper insulation of the windings.

FORMICEMENTEX® Characteristics Epoxy is a thermosetting resin. Enamelled wires are covered with a thin layer of epoxy tack-free cresol-free resin at B-stage. ESSEX ITALY epoxy system is characterised by the following properties. • Uniform melting • High grade curing • Stability of B-stage (more than 6 months at 32°C) • Strands bonding during the drying process of the winding • Available for medium (100-110 °C) and high (110-120 °C) operative temperature

Advantages • Transformers improve against unstable electrical network and the risks of shorts. • Formicementex enamelled rectangular wires used in Transposed Conductors provide exceptionally

strong bond strength in the winding. • Conductors in the winding become like a solid beam and can withstand strong electrodynamic stresses

created during short circuits event. • Epoxy resin cure in the same thermal treatment for drying paper (100-130°C) • The best oil resistance • Each single strand has better insulation • Tack-free surface and then dust-free and easy handling of the strip without powder residues • No-pollution because the B-stage resin does not contain residues of harmful solvents • Small thickness of coating needed in order to achieve very strong bonding (0.02-0.05 mm) • Better sliding among the strands, improving the CTC windability

7.0 x 1.8 mm conductor02468

10

MPa

7.0 x 1.8 mm conductor

Comparison of adhesive force in epoxy coated conductors with differentmechanical properties

Annealed (R0.1=50-80 MPa)CPR1 (R0.1=140-200MPa)CPR3(R0.1=220-260MPa)


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CTC DATA SHEET

Enamelled rectangular wire Transposed Conductor Number of strands From 5 to 81 Separator thickness 0.10 0.20 0.30 Max. width 12.5 Max. radial dimension 802

Min. width 2.8 Min. radial dimension 4 Max. Thickness 3.75 Max. axial dimension 25 Min. Thickness 1.12 3 Min. axial dimension 5 Preferred ratio h/b 2.0-6.5 Preferred ratio

B/H =( ) ( )

( )n b i

h i+ × +× +1

4Ε

Ε

Radial /Axial ratio less or equal

to 7

All dimensions are in mm

2 dimension without insulation paper 3 depending on the preferred ratio value


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CTC DIMENSIONAL DATA

B

ic/2 h

Hip

EPOXY

ENAMEL COPPER Calculation of the cable outer dimensions Maximum dimension in axial direction:

( ) KhicipihH +++Ε+×= 2 (1.1) b

Maximum dimension in radial direction

( ) KbicibnB ++⎥⎦

⎤⎢⎣

⎡Ε+×⎟

⎠⎞

⎜⎝⎛ +

=2

1 (1.2)

Where: H = Axial cable dimension; B = Radial cable dimension h = Axial strand dimension; b = Radial strand dimension Kh = Maximum plus tolerance 0.10 mm for axial dimension Kb = Maximum plus tolerance for radial dimension (values in table ) n = Number of strands in the cable iE = Increase in dimensions due to enamel ( typical value 0.12 mm for pva and 0.17 mm for pva plus

epoxy ) ip = Thickness of separator between the strands stacks ic = Paper covering (in case of cable without paper ic/2 is the thickness of the plastic wire) Table: Kb values

Number of strands S/h ≥ 7 and b < 2 mm and Rp02< 180MPa

All other cases

Up to 21 0.20 0.30 From 23 to 27 0.25 0.50 Form 29 to 35 0.35 0.60

Greater than 35 0.70 1.00 S = Transposing distance (Transposing pitch), distance between two transpositions Interleaving paper According to the axial pressure applied to final winding, if necessary, in order to prevent tilting effect, an interleaving paper can be used. This paper is inserted between the two stacks, if required by the Customer. We suggest 0.11 mm thickness if there is no specified value by the Customer. 0.11 mm paper should be inserted if

( ) ( )Wn b

for PVA CTC or for Formicementex CTC=− × +

> >3

210 25

Ε

Standard Thickness are 0.10 - 0.20 - 0.30 - 0.40 mm. Width of the paper is the W value with approximation to the lowest pair unit (example: if W = 7.36 we select 6 mm paper, but this is the minimum value that we suggest to use). External dimensional tolerances External dimensions, obtained by formulas (1.1 and 1.2), are tested under pressure of 1 MPa or the value required by the Customer.


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MINIMUM WINDING DIAMETER AND TRANSPOSING PITCH The first property to satisfy is the windability of CTC on the transformer core. Generally the length in which there is a complete transposition of one strand (called stranding pitch) should be less than the circumference of the core. This requirement is due to the flexibility of the CTC in order to avoid any damage of the CTC structure. We define 3 elements: transposition pitch, transposition length, stranding pitch. Minimum winding diameter is in relationship with the dimensional characteristics and the stranding pitch by the following formula: π × = ×Di S n stranding pitch S M h= × transposing pitch Where: S = Transposing distance (Transposing pitch), distance between two transpositions M = S/h = Proportionality coefficient - transposing factor (if less than 5, Kb shall be agreed during the contract review).

lt S< ×05.

If M is lower than 5 it can be difficult to produce the CTC for strand width greater than 6 mm, because the pitch can be too small for the transposing machine. If n is large, the pitch must be short but not too short to get M lower than 5. Transposition length - lt lt is the measured length on the CTC between two points where the strand goes from one side to the other side of the CTC stack. The transposition length should be less than 50 % of the transposition pitch to increase the slip among the strands in the transposition area and in order to reduce the value of the radial coefficient Kb.


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Hints for winding Transposed Conductors

barrel

flange

traverse

width CTC drum Core

a) bore

b)

d) c) During winding operations it is necessary to use some criteria in order to get the best winding of the Transposed Conductor on the transformer core, particularly if the CTC has a high ratio H/L. • When the diameter core is greater than 25 times the radial dimension H, it is possible to wind the CTC

leaving it free in the region between CTC and winding core (see figure a). • In case of core with diameter less than 25 times the radial dimension of the CTC, it is possible to wind

the Transposed Conductor using the following hints: • distance between transformer core and the drum axis shall be multiple of the stranding pitch

Pc • CTC shall be held up and driven by pulleys (see figure b) in order to avoid flexions in the

length between core and drum. • In order to avoid CTC twisting, pulleys shall have adjustable flanges (see figure c and

adjustable flanges d). Drying and height adjustment processes after winding. Generally ESSEX ITALY CTC get the best bonding condition after curing in the range between 110 and 130°C. In Laboratory tests are done on epoxy coated strands after 24 h at 120°C in Lab oven. Some Customers use the following cycle since many years without problems: • In a Vacuum oven a pressure of 3-5 N/mm² (on the spacers for the helical coil windings) is applied and the temperature is raised to 115°C for 48-72 h (after 6-7 hours of preheating and 10 h of decreasing temperature). • A dimensional adjustment is got at a pressure of the same previous value in order to reach the final dimension. • Then a curing in vapour phase is done at 130°C for 48 h (after 2-3 h of increasing temperature). • Before the treatment be sure that at the two ends the strands have sufficient separation among them in order to avoid unwished bonding.


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DRUMS FOR TRANSPOSED CONDUCTORS Standard wooden drums (B – returnable type and P- not returnable drums).

Type Max. content

Dimensions (mm)

kg flange barrel bore width traverse B100/400 700 1350 1000 82 400 290 B100/610 1100 1350 1000 82 610 486 B130/810 2100 1650 1290 82 810 686 B140/1010 4000 2000 1400 82 1010 860 B160/1010 3000 2000 1600 82 1010 860 P100/S 1100 1200 800 82 610 490 P100/L 1600 1200 800 82 710 590 P160/S 2000 1600 900 82 610 450 P160/L 2800 1600 900 82 710 550

All dimensions are in mm. Drums type B100-B130-B140-B160 may be fitted with separators to permit parallel winding of 2 or more cables. Other types of not returnable drums are available upon request.

ORDERING When ordering ESSEX ITALY Continuously Transposed Conductors, the following requirements are necessary: • number of strands and their nominal dimensions • type of copper and type of enamelling wires (epoxy or not) • minimum winding diameter • total paper thickness, minimum number of layers and type of papers • interleaving paper and its thickness • required length and type of drum Please use our card for Contract Review (see next page) or ask our Sales Dept. for the use of internet BtoB in www.invexonline.it.


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CONTRACT REVIEW ESSEX ITALY SpA ISO 9001

TRANSPOSED CONDUCTOR (CTC)CustomerSpecification ORDER :

W

Number of conductors N°Conductor Width (mm) mmConductor Thickness (mm) mm B

Corner radius conductor mmMechanical properties N/mm2Paper typesPaper increase (mm) mmNumber of papers N°Type of enamelEnamel increase mm

Type of interleaving paperThick.of interleaving paper mmInner Winding diameter mm

Overall dimensions W= B= mm

N° of lengths Meters per length REEL TYPE No of reels SEP

Total kg Total insulated kg

Order with penalty

Delivery date One way drum

Comment:

DATE _______________________________ CUSTOMER STAMP AND VISA: __________________

MOD / 3.1 ED.3 REV 0 1.11.2007

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