Summary
Transformers immersed in insulating fluid with natural self cooling (ONAN), three-phase, 50/60 Hz.
For indoor or outdoor use.
Hermetically sealed, CRGO Silicon steel, High-strength cold-rolled steel tank.
Standard
The transformers described in this catalogue are designed and tested in accordance to IEC/BSEN 60076.
Features
Common power ratings:
30, 50, 80,100,125,160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500 kVA.
This transformer is designed for voltages of ≤ 36 kV. Specific figures are not given for this parameter because of the wide variety of voltages used. Transformers can be supplied on demand to run at two different primary voltages, the shift between these input voltages has two
basic alternatives:
• with a primary tap changer which can be switched with no load and no applied voltage
• or by changing terminals under the cover.
The secondary voltage under no load is allocated at 400V, 415V, 433V, though other voltages can be supplied on demand.
When usage requires two voltages, transformers with two simultaneous voltages can be supplied. In this case the no-load voltages are set to 400V(230V),415V(240V),433V(230V) .
The connections normally used are as follows:
• For rated power levels of 160 kVA or less: Yyn0
• For rated power levels over 160 kVA: Dyn11.
• Dyn5, Yd11 and others can customaized.
As per IEC /BSEN 60076 standards these are
set in accordance with the highest voltage for the material,
being the level immediately above the rated voltage.
| Material maximum admissible voltage |
12kV |
17,5kV |
24kV |
36kV |
| Withstand voltage |
28kV |
38kV |
50kV |
70kV |
| Basic insulation level |
75kV |
95kV |
125kV |
170kV |
As per IEC/BSEN 60076 , in normal operating mode:
• 60º K max. in oil
• 65º K average in windings
Other temperature rise levels on demand.
Transformers covered must have one of the following oil expansion systems:
a) an external conservator tank
b) an air chamber under the cover
c) a hermetically sealed elastic tank
ROOQ recommends option (c), which is the one considered in this catalogue, as it has the following advantages:
1.Smaller size, as there is no need for an conservator tank or air chamber, making for easier transformer transportation and placement.
2.Lower overall weight.
3.Increased sturdiness and less risk of leaks, there being no weak points such as welds between the expansion tank and the cover, oil level gauge, Silicagel air breather, etc.
4.Low maintenance due to the absence of elements such as the drier, over-pressure valves and liquid level indicators.
5.No degradation of insulating liquid (oil) by oxidation or absorption of moisture, as there is no contact with the air. The liquid therefore remains in ideal condition.
6.Better conservation of seals due to lack of contact with air, which means that they stay more flexible.
Construction details
I- MAGNETIC CIRCUIT
Oriented grain, very low loss magnetic plate is used following IEC/BSEN 60076. The type or class of plate is chosen on the basis guaranteed noise level and losses. The net cross section is maintained constant in limbs and yokes throughout the magnetic circuit, as a special configuration does away with the need for cross-section reducing grip bolts (section reduction).
The limbs and yokes are joined by 45º lugless joints, with complete one-piece yoke, and stacking is arranged so that each plate profile is staggered with regard to the previous one, thus minimising the effect of the gap. The profile is stepped, with the number of steps required to obtain the best coefficient of useful surface area.
II- LOW VOLTAGE WINDING
This winding is located next to and concentric with the magnetic circuit. Two clearly different types of wire are used depending on the allocated current:
- Rectangular cross-section with rounded edges.
- Strips with conditioned edges.
In the former case each wire is insulated with thermal class A cellulose paper or class H enamel. Strips are used bare.
The rectangular wire winding is set up in a complete layer configuration with one or more concentric channels for cooling.
The insulation between layers is always B status resin impregnated.
The width of the strip on strip type winding with conditioned edges covers the whole axial width of the coil, so that each turn is a layer of winding. As the strip is wound a layer of type B resin impregnated paper is wound with it. This polymerises during the drying cycle, giving the winding the strength to withstand the mechanical stresses entailed by short circuits as per IEC 60076 standards.
III- HIGH VOLTAGE WINDING
This is wrapped around the low voltage winding to lie concentric with it, separated by an insulation structure giving the level of insulation desired.
The conductors used are of two types:
• circular cross-section wire
• rectangular cross section strips.
The conductors are insulated with thermal class H enamel. The rectangular section wires or strips have thermal class A paper or thermal class H enamel. With both types of wire, the winding configuration is anti-resonant in one section, making it highly resistant to ray type pulse waves.
The insulation between layers is resin impregnated, polymerising during drying to give the winding the strength to withstand the mechanical stresses entailed by short circuits.
IV- ACTIVE PART
This is the name given to the set of elements which can be removed from the tank of the transformer. Apart from the core and windings,the main elements are:
• fixing and guide structure
• tap changer
• cover
• cover bushing
V- TANK
The distribution transformer tank is elastic, enabling it to absorb the increase in volume of insulating fluid as it heats up due to the transformer operation without experiment permanent deformations. It comprises the following components:
• supporting frames
• base
• cooling fins
• outer frame
- The supporting frames are welded to the base in a continuous, watertight bead to prevent rusting. They have holes for attaching wheel heads and dragging the transformer.
- The base is bath shaped, with earth connections and a drainage device on the sides.
- The cooling fins are the fundamental part of the tank: they form the corrugated side walls and give it the required elasticity.They are made of cold-rolled steel plate between 1 and 5 mm thick, bent without drawing. Elasticity is obtained by a suitable combination of height, depth, plate thickness and resulting internal pressure.
- The outer frame of the tank is made of L-section steel, welded to the top of the corrugated side walls. The top of this frame houses the pressure limiters for the seal and bear the holes for the cover/tank fixing screws.
The two tables below indicate the guaranteed rated figures as per IEC60076 standards.
These figures are valid for a single secondary voltage, even if there is more than one primary voltage.
Highest voltage for material: ≤ 12 kV
| Rated capacity (kVA) |
H.V.
(kV) |
Tapping range |
L.V. (kV) |
Vector group |
Loss(kW) |
No-load current (%) |
Impedance voltage (%) |
Weight (kg) |
| Load loss |
No-load loss |
oil |
Total |
| 10 |
6 10 11 |
±5% or ±2*2.5% |
0.4 0.415 0.433 |
Dyn11 or Yyn0 |
0.26 |
0.09 |
3.2 |
4 |
45 |
172 |
| 20 |
0.44 |
0.10 |
3.0 |
65 |
240 |
| 30 |
0.63 |
0.13 |
2.3 |
65 |
245 |
| 50 |
0.91 |
0.17 |
2.0 |
80 |
330 |
| 63 |
1.09 |
0.20 |
1.9 |
90 |
365 |
| 80 |
1.31 |
0.25 |
1.9 |
95 |
410 |
| 100 |
1.58 |
0.29 |
1.8 |
115 |
490 |
| 125 |
1.89 |
0.34 |
1.7 |
140 |
620 |
| 160 |
2.31 |
0.40 |
1.6 |
155 |
720 |
| 200 |
2.73 |
0.48 |
1.5 |
175 |
810 |
| 250 |
3.20 |
0.56 |
1.4 |
200 |
940 |
| 315 |
3.85 |
0.67 |
1.4 |
215 |
1090 |
| 400 |
4.52 |
0.80 |
1.3 |
240 |
1250 |
| 500 |
5.41 |
0.96 |
1.2 |
285 |
1460 |
| 630 |
6.20 |
1.20 |
1.1 |
4.5 |
345 |
1720 |
| 800 |
7.50 |
1.40 |
1.1 |
390 |
2050 |
| 1000 |
10.30 |
1.70 |
1.0 |
460 |
2430 |
| 1250 |
12.00 |
1.95 |
1.0 |
550 |
2850 |
| 1600 |
14.50 |
2.40 |
0.8 |
690 |
3600 |
| 2000 |
18.00 |
2.60 |
0.7 |
790 |
4300 |
Highest voltage for material: 15-24 kV
| Rated capacity(kVA) |
H.V. (kV) |
Tapping range |
L.V. (kV) |
Vector group |
Loss(kW) |
No-load current (%) |
Impedance voltage (%) |
Weight (kg) |
| Load loss |
No-load loss |
oil |
Total |
| 30 |
15 20 |
±5% or ±2*2.5% |
0.4 0.415 0.433 |
Dyn11 or Yyn0 |
0.60 |
0.10 |
2.1 |
4 |
85 |
350 |
| 50 |
0.87 |
0.13 |
2.0 |
90 |
480 |
| 63 |
1.04 |
0.15 |
1.9 |
110 |
600 |
| 80 |
1.25 |
0.18 |
1.8 |
110 |
660 |
| 100 |
1.50 |
0.20 |
1.6 |
120 |
700 |
| 125 |
1.80 |
0.24 |
1.5 |
130 |
800 |
| 160 |
2.20 |
0.29 |
1.4 |
140 |
940 |
| 200 |
2.60 |
0.33 |
1.2 |
160 |
1130 |
| 250 |
3.05 |
0.40 |
1.2 |
180 |
1290 |
| 315 |
3.65 |
0.48 |
1.1 |
230 |
1400 |
| 400 |
4.30 |
0.57 |
1.0 |
250 |
1550 |
| 500 |
5.15 |
0.68 |
1.0 |
260 |
1780 |
| 630 |
6.20 |
0.81 |
0.9 |
4.5 |
320 |
2100 |
| 800 |
7.50 |
0.98 |
0.8 |
350 |
2560 |
| 1000 |
10.30 |
1.15 |
0.7 |
450 |
2800 |
| 1250 |
12.00 |
1.36 |
0.6 |
490 |
3200 |
| 1600 |
14.50 |
1.64 |
0.6 |
640 |
4000 |
| 2000 |
17.14 |
1.94 |
0.6 |
800 |
4900 |
| 2500 |
20.26 |
2.30 |
0.5 |
1180 |
6300 |
Highest voltage for material: 36 kV
| Rated capacity(kVA) |
H.V. (kV) |
Tapping range |
L.V. (kV) |
Vector group |
Loss(kW) |
No-load current (%) |
Impedance voltage (%) |
Weightb (kg) |
| Load loss |
No-load loss |
oil |
Total |
| 50 |
30 33 35 38.5 |
±5% or ±2*2.5% |
0.4 0.415 0.433 |
Dyn11 Yyn0 Yd11 |
1.27 |
0.21 |
2.0 |
6.5 |
265 |
860 |
| 100 |
2.12 |
0.29 |
1.8 |
310 |
1150 |
| 125 |
2.50 |
0.34 |
1.7 |
320 |
1190 |
| 160 |
2.97 |
0.36 |
1.6 |
360 |
1230 |
| 200 |
3.50 |
0.43 |
1.5 |
390 |
1300 |
| 250 |
4.16 |
0.51 |
1.4 |
425 |
1480 |
| 315 |
5.01 |
0.61 |
1.4 |
460 |
1590 |
| 400 |
6.05 |
0.73 |
1.3 |
490 |
1760 |
| 500 |
7.28 |
0.86 |
1.2 |
540 |
2150 |
| 630 |
8.28 |
1.04 |
1.1 |
620 |
2380 |
| 800 |
9.90 |
1.23 |
1.0 |
780 |
2800 |
| 1000 |
12.15 |
1.44 |
1.0 |
850 |
3410 |
| 1250 |
14.67 |
1.76 |
0.9 |
950 |
3890 |
| 1600 |
17.55 |
2.12 |
0.8 |
1060 |
4620 |
| 2000 |
19.35 |
2.72 |
0.7 |
1195 |
5345 |
| 2500 |
20.70 |
3.20 |
0.6 |
1285 |
5960 |
| 3150 |
24.30 |
3.80 |
0.6 |
7 |
1470 |
6695 |
| 4000 |
28.80 |
4.52 |
0.5 |
1760 |
8350 |
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