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Partners in Power
Cast Resin Transformers
Technical Information
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Why Cast Resin Transformers?
The High-Security,
Low-Cost Solution
• Reduced Costs:
Low fire risk permits location near
the load – shortens expensive LV
feeders – reduces volt-drop.
• Planning Flexibility and Safety:
No oil sump – no fire barriers –
no siting restrictions. Thermal
mass less than 15 % of equivalent
oil 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 by
epoxy-resin insulation along their
whole length – no re-pressing or
adjustments required – even under
the most severe load conditions.
• Power Reserves:
Short-time overload capacity
much greater than liquid-filled
transformers.
For longer overloads, forced cooling
is a standard option.
‘AN’ transformers can be equipped
for ‘AF’ just by adding fan assembly
and relay to uprate to 150 %.
• Reliability
More than 10.000 units in service.
Statistics show reliability even
better than oil.
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Design Details
The High-Voltage Winding:
The Low-Voltage Winding:
• Spiral layer copper wire winding in
epoxy/glass fibre insulation, voidfree cast in steel mould.
Full-height copper sheet is wound
in pre-preg insulation and bonded
by a heating process into a strong
cylinder.
• Partial discharge below 10 pc –
every coil and complete transformer
routine tested.
• Cooling ducts not only further
improve cooling, but ensure any
stresses fall in air, not inside
the coil.
Even the most extreme and rapid
temperature fluctuations will not
induce cracking of insulation or
deformation of the winding, due to
the balance of strength and elasticity
of the epoxy/glass fibre combination.
The Core:
Coil clamps:
High-quality, grain-oriented steel,
and ‘step-lap’ laminated mitred joints
reduce no-load losses and noise
emission.
LV-coils are centred against the core
by high-temperature synthetic rubber
spacers.
Copper strip connections are pressure
welded to the sheet winding.
Binding and two-part coating ensures
cohesion of the core laminations –
protects against corrosion – further
reduces noise.
Each coil is tested for radial strength
in a special press which plots a
force-displacement diagram.
The Frame:
Short-circuit stresses are minimised
because the current distributes freely
across the full-height conductor.
Upper and lower steel channel core
clamps are joined by steel tie bars
bound to the core, and the whole
transformer assembly is fixed to a
carriage with bi-directional wheels
and lifting and towing eyes.
HV-coils are centred by upper and
lower coil clamps with hightemperature synthetic rubber pads
which 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 the
upper coil clamps.
Temperature Monitoring:
The complete HV and LV insulation
system exceeds class F – meets USA
ANSI class 150°C/40.000 hrs.
Two PTC’s per phase in conjunction
with TS-O1 relay.
‘Alarm’ for temperature exceeding
that set for calculated life
expectancy. ‘Trip’ for temperature at
thermal limit of temperature class.
For forced cooling (up to 150 %
rating normally) PT 100 in
conjunction with TAA-12 relay
controls fans, and monitors all
components of the system – digital
temperature indication is included.
Also fans are tested automatically
every 30 days.
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Environmental Safety
• Practically maintenance free.
• Unaffected by the most severe
temperature fluctuations.
• Impervious to damp and dust.
• No pollution danger – acceptable
even in water protection areas.
Fire performance
Environmental category
Climatic category
Classifications F0, F1:
Environmental category as standard
= E1 (E2 available up to 24 kV)
(salt spray exposure or immersion
in salt water).
Climatic category C2 as standard –
this is the most onerous test, with
rapid temperature rise from -30°C to
+155°C applied directly to HV coils
(not indirectly applied via LV coil
heat transfer) only epoxy/glass fibre
makes this possible; particle filled
epoxy is brittle and cracks at low
temperatures.
Classifications F0 is standard – meets
all flue-gas requirements – no
restrictions on installation.
Classification F1 is also available
as standard equipment for countries
in which Classification F1 is specified,
or for customers requiring such
specifications.
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(Note: Classification F2 has been
abandoned from standards due to
the fact that suitable test
specifications have not been
defined.)
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Technical capacity
Silence is a
transformer priority
Transformer ratings, specifications,
standards
Type tests and Routine tests
Short-circuit strength
The most important data on the
rating plate of the cast resin
transformer are documented by test
reports. They are based on orderrelated and associated national and
international standards and
regulations such as IEC 76 and 726,
VDE 0532, NF C52-726, BS 7806,
ANSI C57-1291, CENELEC HD 464.
Impulse tests are carried out as type
tests based on customer
specifications and as sampling tests
within the quality assurance system.
Cast resin transformers have been
successfully tested and supplied for a
system voltage of Um = 36 kV with a
lightning impulse voltage of 200 kV.
LV foil windings which are bonded to
form a cylinder bloc in combination
with the HV cast-resin windings
provide the highest possible
strength levels for generated
electrodynamic short-circuit forces.
Type tests carried out by recognised
independent international institutes
have substantiated this fact. Based
on our winding design, the
knowledge derived from testing has
led to a simplification of centering
and support.
Subsequent to impulse tests, partialdischarge measurements are always
carried out to check for the proper
dielectric state before the unit is
supplied to the customer.
Additional type tests and routine
tests include:
• Heat run test
• Zero phase-sequence impedance
• Capacity
The reduction of air-transmitted
noise caused by transformers is
being taken more and more into
consideration.
As characteristic noise values for cast
resin transformers without enclosures
in AN operation, the following may
be utilised in practical applications.
Therefore, SGB cast resin
transformers are offered not only in
standard design in accordance with
DIN 42 523 but also with reduced
losses and noise suppression.
In addition to the choice of induction
and core material, the overlapping of
core legs and yokes in a „Step-lap“
h
design has a positive effect on the
emission of noise as well as on the
transformer losses.
A-weighted sound pressure level
MA
LPA in dB
A-weighted sound power level
Core height
Inspection guaranteed
DWA
and adjunct level of measuring
surface
LS in dB
LWA and LPA with LS have a specified
interrelationship found in
DIN 45 635 / Section 30
Arrangement of measurement points for noise
measurements on dry type transformers
with enclosure.
Reference surface
Measurement path
The following routine tests are
carried out on each transformer:
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•
•
•
•
•
•
•
1m
Winding resistance
Ratio and polarity
Impedance voltage
Load losses
No-load losses and current
Induced overvoltage test
Winding test
Partial discharge test
Distance is 1m
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LWA in dB
LWA = LPA + LS
Noise measurements are carried out
as special test at regular intervals.
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Protection enclosures
All-around protection
Standard enclosure
• Free-standing or installed on
carriage.
• For indoor or outdoor installation
IP 20 to IP 33 outdoors.
For installation in enclosed electrical
operating areas, enclosures are to
be provided with type of protection
IP 20 and IP 23 respectively.
Enclosure IP 33 is required when
installing in fabrication halls.
Customer specifications can be met
using modular systems.
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For further information please refer
to our detailed brochure
„Standard enclosures for cast resin
transformers“.
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CREATIV CONCEPT REGENSBURG
SGB_GH_engl.qxd
Partners in Power
Manufacturing range
Manufacture and delivery of:
• Oil immersed transformers up to
and including 1.000 MVA, service
voltage up to 525 kV in compliance
with all relevant standards and for
special designs
• Regulating transformers with onload 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
Ohmstraße 10 • 93055 Regensburg
Telefon: +49 (0)9 41/78 41-0
Telefax: +49 (0)9 41/7 17 21
E-Mail: sgb@sgb-trafo.de
www.sgb-trafo.de
SÄCHSISCH-BAYERISCHE
STARKSTROM-GERÄTEBAU GMBH
Ohmstraße 1 • 08496 Neumark
Telefon: +49 (0)3 76 00 / 83-0
Telefax: +49 (0)3 76 00 / 34 14
E-Mail: sgb@sgb-neumark.de
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www.sgb-trafo.de
SMIT TRANSFORMATOREN B.V.
Groenestraat 336 • NL – 6531 JC Nijmegen
Telefon: 0031 / 24 - 356 89 11
Telefax: 0031 / 24 - 356 87 64
E-Mail: sales@smit-trafo.nl
www.smittransformers.com
Druckschrift BTt 43/01
STARKSTROM-GERÄTEBAU GMBH