DT-O
Oil-immersed distribution transformer, ≤ 5 MVA
DT-O
- Hermetically sealed, welded tank with high corrosion protection for low maintenance over the whole service life
- Low-loss designs compliant with EU Ecodesign Directive 2009/125/EC and Regulation (EU) 2019/1783
- Available with biodegradable ester insulating liquids — fire point above 300 °C, K-class rating per IEC 61039
- High withstand capability against harmonics; vibration, tank-rupture and short-circuit tested designs
- Sensformer® digital monitoring available across the fluid-immersed distribution transformer range
Distribution grid substationsIndustrial and urban power distributionOnshore and offshore wind farmsPV and battery energy storage plants
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DT-O covers up to 50 kV of the distribution transformers range (≤ 52 kV across the category, √ scale).
Specifications
Main
| Product type | Fluid-immersed (oil-immersed) distribution transformer |
| Family | Siemens Energy fluid-immersed distribution transformer portfolio (FITformer® — brand shown on the REN and WIND variants in the source documents) |
| Function | Conversion of medium voltage to low voltage at identical frequency |
| Applications | Distribution grids (DSOs, municipalities), industrial and urban areas; renewables (wind, PV, BESS) via REN variants |
| Insulating liquid | Mineral oil; synthetic or natural ester optional (readily biodegradable) |
| Delivery condition | Fully assembled and fluid-filled; plug-and-play solutions available |
Electrical ratings
| Rated power | 50 kVA – 5,000 kVA (this family; wider fluid-immersed portfolio up to 30 MVA) |
| Max system voltage | Up to 36 kV |
| Rated frequency | 50 or 60 Hz |
| Voltage regulation option | Regulated version with MR ECOTAP®: up to 100 A rated current, up to 9 taps, 825 V step voltage |
| Losses | Low no-load and load losses per EU Ecodesign; ultra-low-loss designs available |
| Harmonics | High withstand capability against harmonics |
Mechanical & environment
| Tank | Hermetically sealed, welded tank; high corrosion protection |
| Type-test evidence | Vibration, tank-rupture and short-circuit tested designs |
| Noise | Low noise level designs (optimized noise and losses) |
| Ester fluid benefits | Fire point > 300 °C, higher moisture tolerance, tank-rupture prevention improved up to 20%, readily biodegradable (OECD 301) |
| Digital option | Sensformer® Basic connectivity/monitoring on request |
Standards & certifications
| Product standards | IEC and EN (per factory portfolio slides); IEC 60076-14 high-temperature design applied on the ester-filled 66 kV WIND variant |
| Ecodesign | EU Ecodesign Directive 2009/125/EC and Regulation (EU) 2019/1783 |
| Fluid classification | K-class insulating liquid rating per IEC 61039 (ester option) |
| Factory certifications | ISO 9001, ISO 14001, ISO 45001, ISO 50001, ISO 3834-2 (Budapest DT factory) |
Options & variants
Rows from Siemens Energy fluid-immersed DT factory-portfolio slides (Budapest ≤ 5 MVA family; REN range from the Weiz factory slides) and the 66 kV FITformer WIND flyer. Full fluid-immersed portfolio spans up to 30 MVA / 145 kV.
| Variant | Rated power | Max system voltage | Notes |
|---|---|---|---|
| FITformer® — standard distribution | 50 – 5,000 kVA | 36 kV | Distribution grids; IEC/EN; 50 or 60 Hz |
| Regulated (MR ECOTAP®) | up to 100 A rated current | 36 kV | On-load voltage regulation, up to 9 taps, 825 V step voltage |
| Self-protected (TPC) | 50 – 250 kVA | 24 kV | Self-protected compact design |
| FITformer® REN (renewables) | up to 20 MVA | 145 kV Um | Wind on/offshore, PV, BESS; water cooling and flat-wall tank options |
| FITformer® WIND 66 kV | 8.2 MVA | 66 kV | Nacelle-mounted offshore wind; ester-filled, IEC 60076-14 high-temperature design, weight < 20 t |
Compatible accessories
Digital monitoring
Sensformer® Basic digital connectivity and monitoring
Monitoring & diagnostics
SITRAM® H2Guard Lite online hydrogen (DGA) monitor, 25–5000 ppm, Modbus/DNP3.0
Voltage regulation
MR ECOTAP® on-load voltage regulation (up to 9 taps, 825 V step voltage)
Insulating fluid option
Biodegradable ester insulating liquid (synthetic or natural, K-class per IEC 61039)
Documents & downloads
Presentation Fluid-immersed distribution transformers — family overview & factory network
Presentation Distribution Transformers — portfolio, variants & technical innovations
Fact sheet SITRAM H2Guard Lite — online hydrogen monitoring for liquid-filled transformers
Also covered in the technical library
Brochure Transformers digitalization — Noedra Node suite for substation digitalization
Ordered designations
Representative orderable type designations of this family — searchable via the catalog search.
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