Cast Resin Transformers

Cast Resin TransformersCast Resin TransformersTechnical Information

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SGB_GH_engl.qxd 14.11.2001 9:50 Uhr Seite 1

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Why Cast Resin Transformers?

The High-Security,Low-Cost Solution

• Reduced Costs:Low fire risk permits location nearthe load – shortens expensive LVfeeders – reduces volt-drop.

• Planning Flexibility and Safety:No oil sump – no fire barriers – no siting restrictions. Thermal mass less than 15 % of equivalentoil transformer. No special building work.

• Maintenance Free:No oil, radiator, or tank problems –only needs air for cooling. Completely sealed windings –impervious to damp and dust.Windings are held securely byepoxy-resin insulation along theirwhole length – no re-pressing oradjustments required – even underthe most severe load conditions.

• Power Reserves:Short-time overload capacity much greater than liquid-filledtransformers.For longer overloads, forced coolingis a standard option. ‘AN’ transformers can be equippedfor ‘AF’ just by adding fan assemblyand relay to uprate to 150 %.

• ReliabilityMore than 10.000 units in service.Statistics show reliability evenbetter than oil.


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The Core: Coil clamps:

Design Details

High-quality, grain-oriented steel, and ‘step-lap’ laminated mitred jointsreduce no-load losses and noiseemission.

Binding and two-part coating ensurescohesion of the core laminations –protects against corrosion – furtherreduces noise.

The Frame:

Upper and lower steel channel coreclamps are joined by steel tie barsbound to the core, and the wholetransformer assembly is fixed to acarriage with bi-directional wheelsand lifting and towing eyes.

LV-coils are centred against the core by high-temperature synthetic rubberspacers.

HV-coils are centred by upper andlower coil clamps with high-temperature synthetic rubber padswhich adjust the HV and LV coil position both radially and axially.

The support clamps are porcelain for optimal insulation and to reduce thermal mass.The rubber allows thermal expansion,and reduces noise.Individual adjusters are fitted to theupper coil clamps.

• Spiral layer copper wire winding inepoxy/glass fibre insulation, void-free cast in steel mould.

• Partial discharge below 10 pc –every coil and complete transformerroutine tested.

• Cooling ducts not only furtherimprove cooling, but ensure anystresses fall in air, not inside the coil. Even the most extreme and rapid

temperature fluctuations will notinduce cracking of insulation ordeformation of the winding, due tothe balance of strength and elasticityof the epoxy/glass fibre combination.

The complete HV and LV insulationsystem exceeds class F – meets USAANSI class 150°C/40.000 hrs.

Full-height copper sheet is wound in pre-preg insulation and bondedby a heating process into a strongcylinder.

Copper strip connections are pressurewelded to the sheet winding.

Each coil is tested for radial strengthin a special press which plots aforce-displacement diagram.

Short-circuit stresses are minimisedbecause the current distributes freelyacross the full-height conductor.

The High-Voltage Winding: The Low-Voltage Winding:

Temperature Monitoring:

Two PTC’s per phase in conjunctionwith TS-O1 relay.‘Alarm’ for temperature exceedingthat set for calculated life expectancy. ‘Trip’ for temperature atthermal limit of temperature class.For forced cooling (up to 150 %rating normally) PT 100 in conjunction with TAA-12 relaycontrols fans, and monitors allcomponents of the system – digitaltemperature indication is included.Also fans are tested automaticallyevery 30 days.


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Environmental category Climatic category

Fire performanceEnvironmental Safety

Classifications F0 is standard – meetsall flue-gas requirements – no restrictions on installation.

Classification F1 is also available as standard equipment for countriesin which Classification F1 is specified,or for customers requiring such specifications.

(Note: Classification F2 has beenabandoned from standards due tothe fact that suitable test specifications have not been defined.)

Classifications F0, F1:

• Practically maintenance free.

• Unaffected by the most severetemperature fluctuations.

• Impervious to damp and dust.

• No pollution danger – acceptableeven in water protection areas.

Environmental category as standard= E1 (E2 available up to 24 kV)(salt spray exposure or immersionin salt water).

Climatic category C2 as standard –this is the most onerous test, withrapid temperature rise from -30°C to+155°C applied directly to HV coils(not indirectly applied via LV coilheat transfer) only epoxy/glass fibremakes this possible; particle filledepoxy is brittle and cracks at lowtemperatures.


Inspection guaranteed

Technical capacity

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The reduction of air-transmitted noise caused by transformers isbeing taken more and more intoconsideration.

Therefore, SGB cast resintransformers are offered not only instandard design in accordance withDIN 42 523 but also with reducedlosses and noise suppression.

In addition to the choice of inductionand core material, the overlapping ofcore legs and yokes in a „Step-lap“design has a positive effect on theemission of noise as well as on thetransformer losses.

As characteristic noise values for castresin transformers without enclosuresin AN operation, the following maybe utilised in practical applications.

A-weighted sound pressure level

LPA in dB

A-weighted sound power level

LWA in dB

and adjunct level of measuring surface

LS in dB

LWA and LPA with LS have a specifiedinterrelationship found in DIN 45 635 / Section 30

LWA = LPA + LS

Noise measurements are carried outas special test at regular intervals.

Silence is a transformer priority

Transformer ratings, specifications,standards

The most important data on therating plate of the cast resintransformer are documented by testreports. They are based on order-related and associated national andinternational standards andregulations such as IEC 76 and 726,VDE 0532, NF C52-726, BS 7806, ANSI C57-1291, CENELEC HD 464.

The following routine tests arecarried out on each transformer:

• Winding resistance• Ratio and polarity• Impedance voltage• Load losses• No-load losses and current• Induced overvoltage test• Winding test• Partial discharge test

Type tests and Routine tests

Impulse tests are carried out as typetests based on customer specifications and as sampling testswithin the quality assurance system.Cast resin transformers have beensuccessfully tested and supplied for asystem voltage of Um = 36 kV with alightning impulse voltage of 200 kV.

Subsequent to impulse tests, partial-discharge measurements are alwayscarried out to check for the properdielectric state before the unit issupplied to the customer.

Short-circuit strength

LV foil windings which are bonded toform a cylinder bloc in combinationwith the HV cast-resin windings provide the highest possiblestrength levels for generated electrodynamic short-circuit forces.Type tests carried out by recognisedindependent international instituteshave substantiated this fact. Basedon our winding design, the knowledge derived from testing hasled to a simplification of centeringand support.

Additional type tests and routinetests include:• Heat run test• Zero phase-sequence impedance• Capacity

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Distance is 1m

Measurement pathReference surface

1 m

Arrangement of measurement points for noisemeasurements on dry type transformers

with enclosure.


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Protection enclosures

Standard enclosure

• Free-standing or installed on carriage.

• For indoor or outdoor installationIP 20 to IP 33 outdoors.

For installation in enclosed electricaloperating areas, enclosures are tobe provided with type of protectionIP 20 and IP 23 respectively.Enclosure IP 33 is required wheninstalling in fabrication halls.Customer specifications can be metusing modular systems.

For further information please referto our detailed brochure „Standard enclosures for cast resintransformers“.

All-around protection


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Manufacture and delivery of:• Oil immersed transformers up to

and including 1.000 MVA, service voltage up to 525 kV in compliancewith all relevant standards and for special designs

• Regulating transformers with on-load tap changers

• Cast resin transformers up to and including 24 MVA, rated voltages up to 36 kV

• System enclosures for cast resin transformers

• Transformers with line drop or parallel regulation

• Pole-mounted transformers• Earthing transformers and

Petersen coils• Rectifier and furnace transformers• Resonant-circuit reactances,

coupling transformers and reactors for AF ripple control systems

• Shunt reactors and current limiting reactors

• Compact stations

Subject to technical modifications

Manufacturing range

STARKSTROM-GERÄTEBAU GMBH

Ohmstraße 10 • 93055 RegensburgTelefon: +49 (0)9 41/78 41-0Telefax: +49 (0)9 41/7 17 21E-Mail: [email protected]

SÄCHSISCH-BAYERISCHE STARKSTROM-GERÄTEBAU GMBHOhmstraße 1 • 08496 NeumarkTelefon: +49 (0)3 76 00 / 83-0Telefax: +49 (0)3 76 00 / 34 14E-Mail: [email protected]

SMIT TRANSFORMATOREN B.V.

Groenestraat 336 • NL – 6531 JC NijmegenTelefon: 0031 / 24 - 356 89 11Telefax: 0031 / 24 - 356 87 64E-Mail: [email protected]

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