GEAFOL Cast-Resin TransformersTop Technology all Round

GEAFOL cast-resin transformers – reliable technology

Wherever distribution transformers have

to assure the utmost safety in areas

frequented by people, GEAFOL® cast-

resin transformers are the ideal solution.

With GEAFOL, the limitations of liquid-

filled transformers are avoided, but the

proven characteristics such as operating

safety and service life are retained.

Not for nothing are GEAFOL cast-resin

transformers used, above all, wherever

there can be no compromises with

regard to safety.

They are to be found in high-rise build-

ings, hospitals, road and underground

railway shafts, in offshore installations

and mines and so on

and so on . . .

It is not surprising that the superior

GEAFOL technology is produced under

licence by many trans-

former manufacturers

all over the world.

Well over 80,000 GEAFOL cast-resin

transformers have proved

their worth in power

distribution all round the globe.

The diagram on the facing page shows

the power rating and voltage range

developments achieved since 1966 as

a result of continuous innovation.

20

18

16

14

12

10

8

6

4

2

01966 1970 1975 1980 1985 1990 1995

200

180

160

140

120

100

80

60

40

20

0

MVA

kV

22

24

30

2000

GEAFOL transform-ers cover an outputrange from 50 kVAto 30 MVA withoperating voltagesup to 36 kV.

Power ratingin MVA

Operatingvoltage in kV

Rated lightning im-pulse withstandvoltage in kV

2

Development of voltageand power ratings

3

GEAFOL transformers, with their environmentally sustainable technology and versatility, ensure efficient energy distribution at load centers.

Potting the winding inthe vacuum furnace

U

Foil winding

The voltage remains constantThe interturn voltage can addup to twice the interlayer voltage

U

2 2 133445 6

6

7

7

8

8

Round-wire winding

5

6

7

81

2

3

4

4

2 3 4 5 6 7 8

1 2 3 4 5 6 7

2 4 6 8

1 3 5 7

GEAFOL – perfect technology

The GEAFOL principle has succeededin producing transformers with excellentelectrical, mechanical and thermal char-acteristics, which have also proved tobe particularly compatible with the envi-ronment.

GEAFOL transformers are insulated withan epoxy resin/quartz powder mixture.

This is an environmen-tally acceptable materialthat makes the windingsmaintenance-free, mois-

ture-resistant, tropicalized, flame-retardant and self-extinguishing. Evenwhen the insulation is exposed to arcing,no toxic gases are gen-erated. The windings areclamped between resil-ient spacers that provideeffective vibration insulation both from the iron core and mutually between windings. The result: GEAFOL transformers are as quiet as oil- immersed types.

Versatility

Safe

Environmentally acceptable

The coils of the high-voltage windingsare of aluminum foil. Why foil windings?Because foil windings combine a simplewinding technique with a high degreeof electrical safety. The insulation issubjected to less electrical stress thanin other types of windings. In a conven-tional round-wire winding, the interturnvoltage can add up to twice the interlayervoltage, while in a foil winding it neverexceeds the plain voltage per turn be-cause each layer consists of only onewinding turn. The result: High powerfrequency and impulse voltage withstandcapability.Why aluminum? The thermal expansioncoefficients of aluminum and cast resinare so similar that thermal stresses dueto load changes are kept to a minimum.The high-voltage windings are pottedwith epoxy resin under vacuum at a hightemperature. This procedure preventsundesirable gas inclusions. The qualityof the potting combined with the electri-cal advantages of the foil winding playsa decisive role in providing freedom frompartial discharges (up to about doublethe rated voltage).The low-voltage strip winding is also ofaluminum. The width of the aluminumstrip is equal to the length of the coil.This considerably reduces axial short-circuit forces in the transformer. Theconductor strip and the insulation materialare bonded together by heating, andthus form a compact unit with sufficientstrength to withstand radial forces reli-ably.

Dry-type transformers must be markedwith proven environmental, climate andfire resistance ratings. Our GEAFOL cast-resin transformers are suitable for uni-versal use and satisfy the requirementsof the highest defined classes:• Environmental class E2• Climate category C2 *)• Fire resistance class F1*) For outdoor installation, IP 23 degreeof protection must be maintained.

5

Partially potted HVwinding with magnifiedcross-section of coil

LV HV

Optional methodsof connectionSpecial version:LV connection atthe bottom

GEAFOL standardprotective casings,e.g. to IP 20 degreeof protection.Optionally modifiedcasing designs arepossible.

Radial-flow fans in-crease performance byup to 50 %

GEAFOL – perfect technology

Flexible

Economical

6

Radial-flow fans with temperature-dependent control can be installed toprovide capacity reserves and to coverpeak load periods.

In this way, the transformer outputcan be raised by up to 50%(continuous operation!)

To simplify installation and connection,the transformer is optionally availablewith connection on either the HV or LVside, top or bottom. Plug connectionsare also available.

Planning with GEAFOL does away withthe limitations imposed by conventionaltransformer technology. Since thesetransformers can be installed withoutdifficulty at load centers, optimum supplysystem concepts are possible. No specialsafety features are required (such ascoolant-collecting troughs).

Since the GEAFOL transformers needless space than liquid-filled and gas-insulated transformers, a higher outputcan be accommodated in the same area.

The modular design of the transformeris another economical feature. Windings,for instance, can be mounted andreplaced on the spot.

GEAFOL transformers are maintenance-free. Once connected, they can be leftto get on with their job.

If the advantages of GEAFOL trans-formers are taken into consideration asearly as at the planning stage, the overallcosts of a power supply system can oftenbe considerably reduced.

GEAFOLtransformer technologyat a glance

7

Three-limb coremade of grain-oriented low-loss electro-laminations insulated on both sides

LV windingof aluminum strip, windings fully coveredwith bonded insulating sheet

HV windingconsisting of individual vacuum-pottedcoils of aluminum foil. See magnifiedcross-section on page 5

LV terminals

HV terminals

HV tapping links(on LV side) permitting adjustment tosystem conditions; can be reconnectedin de-energized state

Resilient spacersto provide insulation for core and wind-ings against mechanical vibrations, result-ing in low noise emissions

Yoke clamping frame and truckRollers can be swung round forlengthways and sideways travel

Epoxy resin/quartz powder insula-tion makes the transformer maintenance-free, moisture-proof and tropicalized,flame-resistant and self-extinguishing

Temperature monitoringby PTC thermistor detectors in the LVwinding

Paint finish on steel parts:Multiple coating, RAL 5009. Optionally:Two-component paint system or hot gal-vanizing (for particularly corrosive envi-ronments)

Modular designe.g. windings can be mounted andreplaced on the spot

1

2

3

4

5

6

7

8

Outside and part section-al view of a 630-kVAGEAFOL cast-resintransformer, Um=24 kV

5

6

7

8

1

2

3

4

Siemens AGPower Transmission andDistribution GroupTransformers DivisionTransformatorenwerk KirchheimHegelstrasse 20D-73230 Kirchheim/Teck

www.ev.siemens.dePower

to the

Siemens Aktiengesellschaft Order No. E50001-U413-A13-X-7600Printed in GermanyDispo-Stelle 1920161D6370 Ra/Br 101844 PA 06003.

Subject to change without prior notice