MEDIUM VOLTAGE

OIL AND CAST RESIN

DISTRIBUTION TRANSFORMERS

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 Product range
Oil filled distribution transformers

Nominal ratings from 25 to 2000 kVA

H.V. reference 7,2 - 12 - 17.5 - 24 kV
H.V. tappings off load ± 2.5% / ± 5%
Connections Dyn11 - Yyn0
Cycles 50-50 / 60-60
Guarantee 24 months

Cast resin distribution transformers

Nominal ratings from 100 to 2500 kVA

H.V. reference 7,2 - 12 - 17.5 – 24 kV
H.V. tappings off load ± 2.5% / ± 5%
Connections Dyn11 - Yyn0
Cycles 50-50 / 60-60
Guarantee 24 months

Three phases oil and cast resin transformers, are manufactured and tested
according to the IEC 60076-1 specifications.
Three phases oil transformers until 24 kV are in accordance with the EN
50588-1 and IEC Standards standards.
Cast resin transformers until 24 kV are in accordance with the EN 50588-1
and IEC 60076-1 standards.
Transformers can be manufactured in accordance with the VDE/DIN 0532,
GOST, BS, NF, NEN particular specifications.

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Manufacturing process of the oil distribution transformers
The cores (for oil and cast resin transformers)
The cores are constructed using thin sheets of cold rolled grain-oriented magnetic steel silicon
insulated on both sides.
Conventional grain oriented steel (CGO steel) is used for transformers with normal no-load losses,
while transformers with reduced no-load losses are built using higher quality HiB steel.
The core sheets are cut at an angle of 45°, thus allowing maximum magnetic flux in the rolling
direction.
Then the sheets are stacked in layers of either single or multiple overlaps. The multiple overlap or
“step-lap” method offers additional benefits in terms of lowering no-load losses and noise levels.
Once the sheets are stacked, the core is compressed and glued to form a firmly bonded whole.

The majority of oil filled transformers have an oval-shaped core section having traditional stepped and
fully filled round shape with a square mid section combined.
This method combines the benefits of a rectangular core section (simplicity of production) with those of
a round core section (excellent short circuit withstand capability of the windings).

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The windings
High voltage windings

The high voltage windings are almost exclusively of layered construction.

The copper conductors are made of one or more round or square wires, completely insulated by pure
cellulose paper or by double enamel.
The insulation between the layers consists of pre-coated kraft paper, applied in sheet form.

Low voltage windings

The low voltage windings are usually made of copper or aluminium (from 400 kVA) sheet conductor
(foil); this reduces the axial stresses produced by short circuit to a minimum.
The maximum voltage between each turn is only a few volts. This allows the insulation needed
between the turns (foils) to be limited to one thermo-hardening epoxy adhesive which cures and bonds
during the drying process.

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The tank
The vast majority of distribution transformer tanks are constructed with cooling fins
In hermetically sealed transformers, the cooling fin design also can withstand the working pressure or
the pressures required during the treatment and filling of the transformers.
This allows the tank to be totally filled (and hermetically sealed), thus guaranteeing a long life of the
transformer and reducing maintenance.
For the oil type power transformers from 4 MVA, the tanks are normally fitted with corrugated panels
and equipped with a conservator.
This cylindrical conservator acts as an expansion tank for the oil when it expands as the windings heat
up. The oil conservator is often fitted with a gauge glass, an air vent, an air dryer and a protection
relay.

After welding, the tank is shot-blasted to remove any scale, oil or other surface impurities, leaving a
clean prepared surface for maximum adhesion of the paint coating. Air-drying paint is then applied by
spraying or flooding.
Several coats of paint are applied, to a total thickness of at least 100 microns, thus guaranteeing
adequate protection against corrosion for indoor or outdoor transformers.
The tanks may be galvanised upon request.

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The active parts
The windings are pushed over the core legs and wedged up to fill the spaces between the core and
winding as much as possible.
Interleaving the laminations of the upper yoke with the laminations of the core legs completes the
magnetic circuit.
The porcelain or the plug-in bushings are mounted on the cover, which are then fixed onto the
assembled active part.
The next step consists of connecting the windings to the bushings.
The transformers are fitted with an off load tap changer. This switch allows the increase or decrease of
a certain number of turns while the transformer is disconnected from the electric system.

The voltage ratio of the active part is then tested, and the assembly is dried in a forced air oven to
remove the moisture from the insulating materials. Once the active part has been dried in the forced-
air oven, it is given a final comprehensive quality inspection and placed into the tank.
The top cover is then bolted onto the tank. The transformers are placed in a vacuum chamber and
filled with pre-treated oil (filtered, dried and degassed) under deep vacuum. This ensures optimum
impregnation of the insulation materials by the oil, giving the insulation structure maximum dielectrical
strength.
The transformers are filled with a high quality mineral oil, which fully complies with the requirements of
IEC standard 296

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Fittings and accessories
 Over-pressure valve applied above the cover of the tank
 Lifting hooks to draw out the inside part and the tank
 Base support with translation wheels and hooks to drag the transformer
 Rating plate
 Drain oil valve
 Thermometer pocket

Options

 Dial thermometer with two electrical contacts

 Protective block for hermetic transformers (DMCR or pressostat)
 MV voltage resin terminals to connect plug-in terminals
 Low voltage protecting terminals with protecting hoods
 And other on request

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 Three phase oil - immersed and hermeticaly sealed transformers
160 - 1000 kVA, 17,5 kV, Ecodesign 2 (2021), AA0Ak max., AL winding

Technical data Eletrical characteristics

Standard EN 60076, EN 50588 - 1 Rated power 160 - 1000 kVA

EU Ecodesign Regulation 019/1783 (n˚ 548/2014) High voltage (HV) 10,6 - 11,4 - 12,3 - 15,375 kV
Transformer design Completely oil - filled, hermetically sealed Tapping range HV
± 2 x 2,5 %
Corrugated tank, cover bolted off circiut
Indoor and outdoor use Low voltage (LV) 420/242 V
Continous loading Overload capacity - IEC 60076 - 7 Frequency 50 Hz
Cooling system ONAN, mineral oil - EN 60296 Insulation level Um 17,5 kV LI/AC 95/38
Ambient temperature ≤ 40°C , altitude ≤ 1000 m Um 1,1 kV LI/AC - /3
Thermal class 105 (A) - temperature rise winding/oil 65/60 K Vector group Dyn11
Corrosion protection Coating system - class C3 - EN ISO 12944-5
Standard RAL 7033

Rated power kVA 160 250 315 400 500 630 800 1000
Type aTOHn 3110/22 3310/22 3410/22 3510/22 3610/22 3710/22 3810/22 3910/22
No- load losses AA0 max. Po (W) 189 270 324 387 459 540 585 693
No- load curent I0 (%) 0,5 0,4 0,35 0,3 0,25 0,2 0,15 0,1
Load losses Ak max. Pk75°C (W) 1750 2350 2800 3250 3900 4600 6000 7600
Impedance voltage uk 75°C (%) 4 4 4 4 4 4 6 6
Sound level
- pressure (0,3 m) LpA dB(A) 33 36 38 39 40 41 42 44
- power LWAdB(A) 43 46 48 49 50 51 52 54
Dimensions
- lenght (mm) A 1130 1180 1195 1250 1315 1360 1475 1470
- width (mm) B 690 760 845 820 885 870 940 960
- height (mm) C 1240 1380 1475 1525 1605 1655 1710 1915
Oil 195 245 305 320 380 380 495 560
Weight [ kg ]
Total 1135 1480 1670 1940 2250 2520 3015 3330
Cotrabel bvba, Vlasmarkt 12, 9000 Gent, BE Belgium, tel. 00.32.473.83.90.20 Mail: sales@cotrabel.com

134.A_ 02.02.2021
 Legend

1. Oil filling plug

pressure switch
pressure relief valve
2. Oil drain valve DIN
3. Thermometer pocket
thermometer 2C
4. Tap changer handler
5. Rating plate
6. Earthing terminal
7. Pulling plug
8. Lushing eye
9. Lifting lug
LV Terminals 10. LV Bushing EN 50386
connecting eye
11. HV plug - in terminal EN 50180
Fixing parts EN 50180
12. Trade marke
13. Oil level gauge

Dimensions
Rated power (kvA) 160 250 315 400 500 630 800 1000
Type - aTOHn 3110/22 3310/22 3410/22 3510/22 3610/22 3710/22 3810/22 3910/22
d ( mm ) 125 125 125 125 125 125 125 160
s ( mm ) 40 40 40 40 40 40 40 50
c1 ( mm ) 157,5 157,5 160,5 160,5 160,5 160,5 160,5 202,5
c2 ( mm ) 60 60 60 60 60 60 60 60
c3 ( mm ) 978 1078 1170 1220 1260 1310 1365 1448
c4 (mm ) 1143 1283 1375 1425 1505 1555 1610 1773
a ( mm ) 520 520 670 670 670 670 670 820
e ( mm ) 85 85 85 85 85 85 85 85
f ( mm ) 165 205 205 205 245 245 245 325
g ( mm ) 265 265 265 265 265 265 265 265
n ( mm ) 125 150 150 150 150 150 150 150
The manufacturer reserves the right to change the final dimensions and weights without prior notice.
Cotrabel bvba, Vlasmarkt 12, 9000 Gent, BE Belgium, tel. 00.32.473.83.90.20 Mail: sales@cotrabel.com

134.A_ 02.02.2021
Manufacturing process of the cast resin transformers
The windings
High voltage windings

The high voltage windings are made out of aluminum or copper strips and are designed to avoid that
thermal expansion causes slips between conductors and resin.
The method of manufacture guarantees a perfect distribution of the electrical field and the absence of
partial discharges as well as an excellent resistance to impulse stress.
Guarantees have also been given that the windings resist the external dynamic effects of short-
circuits.
The dielectric materials used (resin, conductors, and insulators) are of class F.
The transformer has a working temperature rise limit of 100°K (Class F).

Low voltage windings

The low voltage windings are obtained from aluminum or copper strips with the same height of the
primary limb to reduce to a minimum the axial strain due to short circuit currents. A class F insulating
block insulates the coils.
Before mounting, the LV windings are immersed in alkyd resin and then polymerized at 150°C. This
process guarantees excellent resistance to external agents (humidity and pollution of the atmosphere).
The winding is designed and made out so that the maximum working temperature rise at full load is
equal to class F (delta T=100°K).
The concentric shapes of the two windings (HV and LV) are maintaining by special spacers - a support
which allows the supply of the flux to be uniformly distributed and avoids the onset of abnormal
vibrations.
The resin used in the casting system is an epoxy resin charged with very fine quartz powder, given the
transformer the necessary characteristics to pass every test successfully.
The computerized monitoring ensures the accurate control of all phases of the process, from the
preparation of the resin to the temperature control in the polymerization.
The epoxy resin used is of the class F thermal stability and the product is manufactured in conformity
with the temperature limits given by the IEC 60726 standards.

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Fittings and accessories

Optional fittings
Standard Fittings

• Lifting hooks • PT 100 thermal resistance

• Base structure with translation • Hermetic sealed box for electric
Wheels. connections
• H.V. Terminals • Forced air cooling
• L.V. Terminals • Digital temp. control with
• Rating plate auxiliary contacts
• Ground plate • Protection box for indoor
• 6 PTC sensors with an electronic installations.
converter.

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 Cast resin dry type transformers - type aTSE
100 - 3150 kVA, 17,5, ECO design 2 (2021), AA0Ak max.

Technical data Electrical characteristics

Standards EN IEC 60076 - 11, EN 50588 - 1 Rated power 100 kVA - 3150 kVA*
o
Ecodesign regulation EU 2019/1783, n 548/2014 High voltage (HV) 10,6-11,4-12,3-15,375 kV
Indoor use Tapping range HV ± 2 x 2,5 % off- circuit
Continuous loading Low voltage (LV) 400/231 V, 420/242 V
Cooling system AN, ANAF - rated power + 40 % with fans Frequency 50 Hz*
Ambient temperature ≤ 40°C *, altitude ≤ 1000 m * Insulation level Um 17,5 kV LI/AC95/38
Thermal class 155 (F) - Temperature rise 100 K Um 1,1 kV LI/AC - /3
Climatic class C2 Thermal shock - 60°C Impedance voltage 6% *
Environmental class E2 Vector group Dyn1*
Fire behaviour class F1 HV windings - Aluminium wire, strip, casted in resin
Partial discharges ≤ 10 pC LV windings - Aluminium wire,tape, impregnated
Degree of protection IP 00 - without housing
Corrosion protection metal parts hot - dip galvanized

Rated power kVA 100 160 250 400 630 800 1000 1250 1600 2000 2500 3150
Type aTSE 698/22 718/22 738/22 758/22 778/22 788/22 798/22 808/22 818/22 828/22 838/22 848/22

No-load losses AA0 max. P0 (W) 252 360 468 675 990 1170 1395 1620 1980 2340 2790 3420
No-load current I0 (%) 0,6 0,5 0,4 0,3 0,25 0,23 0,2 0,19 0,18 0,15 0,1 0,1
Load losses Ak max. Pk75°C (W) 1565 2260 2955 3915 6175 6955 7825 9565 11305 13915 16520 19130
Pk120°C (W) 1800 2600 3400 4500 7100 8000 9000 11000 13000 16000 19000 22000
Sound level
Presure (1 m) LpA dB(A) 35 38 41 44 45 46 49 51 52 54 55 58
Power LWA dB(A) 50 53 56 59 61 63 64 66 67 69 70 73

Total weight [kg] 785 965 1280 1765 2125 2560 2875 3410 4250 4620 5955 7485

Cotrabel bvba, Vlasmarkt 12, 9000 Gent, BE Belgium, tel. 00.32.473.83.90.20 Mail: sales@cotrabel.com

150.A_02.02.2021
 Dimensions [mm]
[kVA] 100 160 250 400 630 800 1000 1250 1600 2000 2500 3150
aTSE 698/22 718/22 738/22 758/22 778/22 788/22 798/22 808/22 818/22 828/22 838/22 848/22
A 1150 1200 1300 1450 1480 1550 1610 1720 1780 1940 2030 2180
B 690 690 715 830 835 980 970 970 980 1270 1270 1270
C 1190 1290 1430 1660 1775 1890 1930 2035 2205 2355 2555 2615
D 125 125 125 125 125 1605 160 160 160 200 200 200
E 520 520 520 670 670 820 820 820 820 1070 1070 1070
F 520 520 520 670 670 820 820 820 820 1070 1070 1070
G 40 40 40 40 40 50 50 50 50 70 70 70
H 390 405 440 490 500 525 545 580 605 620 680 730

Standard fittings Optional fittings HV Terminal

▪ 4 bi - directional flat rollers ▪ Temperature senzors in the LV windings -

▪ 4 lifting holes 2 PTC thermistors or PT 100/phase
▪ 4 haulage holes on the underbase and tripping contacts and cooling fans control
▪ 2 earthing points ▪ Temperature monitoring device with alarm
▪ 1 rating plate (on HV site) ▪ Dial thermometer
▪ AF cooling system (+ 40 %) with the fans
▪ Antivibrations pads
▪ Placement of the LV/HV terminals

Dimensions [mm]
LV Terminal [kVA] 100 160 250 400 630 800 1000 1250 1600 2000 2500 3150
aTSE 698/22 718/22 738/22 758/22 778/22 788/22 798/22 808/22 818/22 828/22 838/22 848/22
a 14 14 14 14 18 18 18 18 18 18 18 18
b 40 40 60 80 100 100 100 120 120 120 125 160
c 5 5 5 8 10 10 12 12 15 16 20 20
d 20 20 30 20 30 30 25 30 30 30 32,5 30
e 15 15 20 20 30 30 25 30 30 30 32,5 35
f - - - 40 40 40 50 60 60 60 60 50
g - - - 40 40 40 50 60 60 60 60 50
h - - - - - - - - - - - 50

Manufacturer reserves the right to modify data without notice.

Cotrabel bvba, Vlasmarkt 12, 9000 Gent, BE Belgium, tel. 00.32.473.83.90.20 Mail: sales@cotrabel.com
150.A_02.02.2021
 Standard fittings
▪ 4 bi - directional flat rollers
▪ 4 lifting holes
▪ 4 haulage holes on the underbase
▪ 2 earthing points
▪ 1 rating plate (on HV site)

Optional fittings
▪ Temperature senzors in the LV windings - 2 PTC thermistors or PT 100/phase
▪ Temperature monitoring device with alarm and tripping contacts and cooling fans control
▪ Dial thermometer
▪ AF cooling system (+ 40 %) with the fans
▪ Antivibrations pads
▪ Placement of the LV/HV terminals

HV Terminal LV Terminal

800 - 2500kVA 3150 kVA

Dimensions
[kVA] 800 1000 1250 1600 2000 2500 3150
aTSE 787/22 797/22 807/22 817/22 827/22 837/22 847/22
A 1590 1660 1830 1830 1890 1980 2150
B 830 970 970 970 1270 1270 1270
C 1890 1920 2070 2215 2380 2540 2640
D 150 150 150 150 200 200 200
E 670 820 820 820 1070 1070 1070
F 670 820 820 820 1070 1070 1070
G 50 50 50 50 70 70 70
H 540 560 575 610 640 670 725
Manufacturer reserves the right to modify data without notice.

Cotrabel bvba, Vlasmarkt 12, 9000 Gent, BE Belgium, tel. 00.32.473.83.90.20 Mail: sales@cotrabel.com 137.A_02.09.2019
Transformer testing
All routine tests are performed and special tests required by IEC 60076 can be performed in a modern
and efficient test room.

Approval tests
Approval tests are automatically carried out on each transformer in order to check the compliance with
the guaranteed data. These tests can be realised in front of the customer at extra-charges. A test
report is delivered for each transformer.
The tests consist in particular:

 Measurement of the winding resistance.

 Measurement of the transformation ratio, the connections and polarity check.
 Measurement of the short circuit voltage (main taps) and of the load losses when returning to
the reference temperature.
 Measurement of the losses and no load current.
 Industrial frequency test.
 Insulation test with induced voltage.
 Insulation test on off load commutators and auxiliary circuits, according to IEC 14-4 § 8.8

Type tests and special tests

Type and special tests may be carried out on request and in accordance with the agreement taken
between the company and the customer. These tests will be carried out on one sample and charged in
line with the agreed conditions during the order negotiation.
Type tests:
 Heating test
 BIL test 1,2/50 µ sec test

Special tests
 Insulation tests (IEC 14-4 part III)
 Measurement of the homopolaire impedance on three-phase transformers
 Dynamic resistance test during a short circuit
 Measurement of the noise level
 Measurement of the loadless current harmonics
 Measurement of absorbed power by the fan motors

All these tests, with the exception of the short circuit test, can be performed in house. Short circuit test
shall be performed upon request in official and accredited laboratories.

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 QUALITY MANAGEMENT

Manufacturing and Quality Assurance rules

The transformers are manufactured in accordance with the national and

international standards and laws in force.
Transformers are complying with the IEC standards
We are specialized in adapting the product to the European standards.
The Quality Assurance of our product maintenance, installation and
manufacturing is ensured and certified in line with the ISO 9001 standards.

VLASMARKT, 12
B – 9000 GENT
sales@cotrabel.com

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