Distribution transformers
2500 kVA transformer
A 2500 kVA transformer delivers 3,608 A at 400 V into a 4000 A incomer. At this size the low voltage board is usually the harder part of the specification.
- Rated current at 400 V
- 3,608 Acalculated
- Rated current at 480 V
- 3,007 A60 Hz systems
- Incomer frame at 400 V
- 4000 Awith busbar trunking to the board
- Fault level at 400 V, at 6 %
- about 60.1 kAtransformer alone, upper bound
- EU load loss ceiling, liquid
- ≤ 18,500 WTier 2, Table I.1
- EU no load loss ceiling, liquid
- ≤ 1,575 WTier 2, Table I.1
Near the limit of one board
2500 kVA sits near the upper end of what one low voltage board is asked to take from one transformer. It supplies large production lines, data hall blocks and distribution centres.
On IEC networks the unit takes a 10, 11 or 20 kV primary and a 400 or 433 V secondary. On 60 Hz systems with a 480 V secondary the same rating delivers 3,007 A.
At a 50 °C site, the design temperature DEWA and Kahramaa use, IEC 60076-2 takes 10 K off every temperature rise limit. A 2500 kVA unit there needs more cooling surface or a lower rating than the same unit in Europe. DEWA's standards add that equipment ratings are expressed at a 55 °C ambient.
Rated currents at 2500 kVA
| Primary | Secondary | Primary current | Secondary current |
|---|---|---|---|
| 11 kV | 400 V | 131 A | 3,608 A |
| 20 kV | 400 V | 72 A | 3,608 A |
| 33 kV | 400 V | 44 A | 3,608 A |
| 13.8 kV | 480 V | 105 A | 3,007 A |
One 2500 kVA unit or two smaller ones
A single 2500 kVA unit keeps the substation compact. Two units of 1250 or 1600 kVA on separate boards keep each board's current and fault level lower, and one side stays live when the other is out of service.
Your designer makes the choice from the redundancy the site needs, the fault level the boards can be built for and the space available. We can request offers for both arrangements, so the difference in cost is visible.
Low voltage fault current, upper bound
| Secondary | Rated current | At uk 6 % |
|---|---|---|
| 400 V | 3,608 A | 60.1 kA |
| 433 V | 3,333 A | 55.6 kA |
Rated current divided by uk, the short circuit impedance, with an infinite source upstream. The fault study, run with the impedance of the unit offered, gives the real value, which is lower.
The 4000 A board
3,608 A calls for a 4000 A incomer and busbar trunking from transformer to board. At 6 percent impedance the transformer alone can drive about 60.1 kA into a fault at 400 V, before the upstream network is counted.
The board and every device on it are verified for the fault level the study returns. At this rating that board takes a larger share of the project cost than at any smaller one.
EU loss ceilings at 2500 kVA
| Construction | Load losses Pk | No load losses P0 |
|---|---|---|
| Liquid immersed | ≤ 18,500 W | ≤ 1,575 W |
| Dry type, cast resin | ≤ 19,000 W | ≤ 2,790 W |
Commission Regulation (EU) No 548/2014 as amended by (EU) 2019/1783, Annex I, Tables I.1 and I.2, Tier 2, from 1 July 2021.
Loss ceilings and transport
For a liquid immersed unit within the table scope, the EU ceilings at 2500 kVA are 18,500 W load losses and 1,575 W no load losses. A 33 kV primary moves the unit into the corrected table, and the offer states the ceiling for its configuration.
Transport is planned from the drawing and mass of the unit offered. The quotation states whether it travels filled and what the site needs for offloading and positioning.
Beyond the UK operators' specification
ENA TS 35-1, the UK network operators' specification for distribution transformers, stops at 2000 kVA, so a 2500 kVA unit is specified outside it, to the owner's own document. Its GB loss ceilings fell at Tier 2 from 22,000 W load and 1,750 W no load losses to 18,500 W and 1,575 W.
What a 2500 kVA transformer request needs
- One unit or two, and the redundancy the site needs
- The fault level the low voltage board is being built for
- A 33 kV primary where that is the network, so the corrected loss table applies
- Offloading and positioning limits on site
Specification template
Fill it in on screen or by hand, then upload it with your request.
Questions buyers ask
What is the full load current of a 2500 kVA transformer?
3,608 A at 400 V, 3,333 A at 433 V and 3,007 A at 480 V. On the primary it is about 131 A at 11 kV and 72 A at 20 kV.
Why do some sites use two smaller transformers instead of one 2500 kVA unit?
To keep the current and fault level of each board lower, and to keep part of the supply available during maintenance or a fault. The designer weighs that against the space and cost of a second unit.
Which specifications matter most for a 2500 kVA transformer?
The voltage pair and tapping range, the impedance, the declared losses against the ceiling, the construction and cooling, the vector group and the low voltage connection. Weight and dimensions follow from those and come with the offer.