Which fields are truly essential?

At minimum: the power in kVA, the primary (MV) and secondary (LV) voltages, the technology (oil-immersed or dry-type) and the environment (indoor or outdoor). With those four we can already frame; everything else refines.

Can I just send my own document?

Yes: send your specification as it stands, in any format. We map it onto these fields with you, fill the gaps together, and only then price.

What is the short-circuit impedance (Ucc) for?

It sets the short-circuit current downstream (which sizes your protections) and conditions parallel operation between transformers. Common values are 4 or 6 percent depending on the rating.

Who completes the missing fields?

We do, with you: leave the French defaults where you are unsure, or flag the point in the comments. Nothing is priced before the specification is coherent.

Specifying a distribution transformer

1 · Power and voltages

Power (kVA): in the standard series (…400, 630, 800, 1000, 1250, 1600…), with a margin of about +25 %; the method is in the sizing guide.
Primary voltage (MV): most often 15 or 20 kV in France, with off-circuit taps (typically ±2×2.5 %) to match the network voltage.
Secondary voltage (LV): 400 / 230 V, at 50 Hz.

2 · Vector group and earthing

The default vector group is Dyn11 (LV neutral available); see vector groups & Dyn11. Also state the LV installation's earthing system (in France, often TT for public-network connection, TN in private installations), as it conditions the treatment of the neutral.

3 · Impedance and losses

Short-circuit impedance (Ucc): often 4 % or 6 % depending on the rating; it drives the downstream short-circuit current and parallel operation.
Losses: no-load and load, compliant with Tier 2 (Regulation (EU) 548/2014) and EN 60076.

4 · Dielectric, cooling, regulation

Dielectric: mineral oil or ester depending on the environment.
Cooling: ONAN (natural) or ONAF (fan-assisted); see cooling modes.
Voltage regulation: DETC (off-circuit) or OLTC (on-load).

5 · Protections and environment

Protections (oil-immersed): DGPT2 (gas, pressure, temperature detection), very common in France, Buchholz relay, thermometer.
Environment: indoor or outdoor, IP rating, altitude and temperature extremes, ambience (pollution, coastal exposure).

6 · Tests, compliance, logistics

Tests: routine and type (IEC / EN 60076), with KEMA / TÜV witness tests if wished.
Compliance: CE, Tier 2, EN 60076 and WEEE, under our manufacturer's responsibility.
Quantity, deadline, delivery: number of units, target date, place and Incoterm.

Our configurator is exactly this checklist, structured. It walks these fields one by one, with the French defaults (MV 15/20 kV, LV 400/230 V, 50 Hz, Dyn11, Tier 2) and an "Other / let me specify" exit everywhere. You end up with a clean summary, ready to price.

Missing some of it?

Fill in what you know and leave the defaults on the rest, or send your own document. We complete the missing fields with you before pricing anything.

Values and orders of magnitude given as guidance for the French context; final characteristics and applicable clauses are confirmed with your project, the factory and, where relevant, the DSO.

Specifying a distribution transformer, field by field