2000 kVA Oil Immersed Transformer for Photovoltaic and Storage Stations
Nov 04, 2025
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2000 kVA Oil Immersed Transformers for Solar and Storage Stations
A 2000 kVA oil immersed transformer is the step-up interface between the low voltage output of a photovoltaic inverter or a battery energy storage converter and the medium voltage collection network of a solar farm or storage station. It is built as an oil immersed distribution transformer with a two-winding layout, a grain oriented silicon steel core and copper or aluminium windings, and it is normally specified with a Dyn11 vector group so that the inverter side stays isolated from the network zero sequence path. Oil immersion keeps the winding hot spot under control during the daily load cycling that is typical of photovoltaic duty.
Electrical Specification Envelope
The flexible part of the specification is capacity and voltage; the rest of the envelope is fixed by the application.
| Parameter | Value |
|---|---|
| Transformer type | Oil immersed distribution transformer |
| Rated capacity | Customized, including 2000 kVA units |
| Rated voltage, HV / LV | Up to 35 kV / customized low voltage side |
| Frequency | 50 Hz or 60 Hz |
| Impedance | 4-6% |
| Cooling method | ONAN, ONAF or customized |
| Tapping range | Plus or minus 2 x 2.5%, customizable |
| Vector group | Dyn11, customizable |
| Winding material | Copper or aluminium |
| Core material | Grain oriented silicon steel |
| Insulation level | In accordance with IEC requirements |
| Temperature rise | Customized to site conditions |
| Protective enclosure | IP00, IP20 or IP23 |
| Winding type | Two-winding |
Loss, Impedance and No-Load Current by Rating
Loss data for the larger ratings of the series is summarised below. Load loss is stated at 75 °C and the pair of values reflects the copper and aluminium winding options; no-load loss is quoted in watts.
| Rated power (kVA) | No-load loss (W) | Load loss at 75 °C (W) | Short circuit impedance (%) | No-load current (%) |
|---|---|---|---|---|
| 630 | 570 | 6820 | 6 | 0.8 |
| 800 | 700 | 8250 | 6 | 0.7 |
| 1000 | 830 | 12000 | 6 | 0.6 |
| 1250 | 970 | 13200 | 6 | 0.6 |
| 1600 | 1170 | 15950 | 6 | 0.5 |
| 2000 | 1380 | 19140 | 6 | 0.5 |
| 2500 | 1640 | 22220 | 6 | 0.4 |
At 2000 kVA the no-load loss is about 1380 W and the load loss at 75 °C is about 19140 W, with a short circuit impedance of 6% and a no-load current of about 0.5%. Loss figures vary with the winding material and with the tapping position, so the routine test report for the delivered unit is the governing document.
Core and Winding Construction
Core: the magnetic circuit is built from high quality cold rolled grain oriented silicon steel sheet with high permeability, using full 45 degree mitred lamination so that no-load loss and no-load current are reduced.
LV winding: foil conductors or 100% copper wire are used to obtain better ampere-turn balance and to cut transverse leakage flux, which improves short circuit withstand. A well designed oil passage structure increases heat dispersion and improves overload capability.
HV winding: copper conductor wire with fibreglass reinforced insulation, in an optimised structure that improves the electric field distribution; lightning impulse wave behaviour is analysed during design to strengthen the insulation margin.
Insulation construction: a Class A insulation system with the HV and LV coils arranged on the same centre, separated by a thin paper cylinder and a small oil clearance.
Tank, Oil and Protective Fittings
Tank: fabricated from high quality steel, with the surface de-rusted by phosphating and finished in an anti-corrosion paint system that resists oil and chemical attack, which suits long term outdoor installation with limited maintenance.
Fittings: high voltage and low voltage bushings, oil release valve, earthing terminal, lifting plates, nameplate and pressure relief valve. Units above 800 kVA are additionally fitted with a signal thermometer and a gas relay.
Insulating oil: grade 25 oil is standard, while grade 45 oil is specified where the minimum ambient temperature drops below -25 °C.
Cooling and enclosure: ONAN is the base cooling mode, with ONAF available where higher loading is expected, and IP00, IP20 or IP23 enclosures chosen according to the exposure of the installation site.
These transformers are used at the generation side of photovoltaic, wind and energy storage plants, replacing a conventional distribution unit where the inverter output must be raised to the collection voltage. Sizing usually follows the inverter rating with a margin for the local ambient temperature and altitude, and the tapping range allows the secondary voltage to be trimmed once the plant is energised.
Frequently Asked Questions
Q: What is the typical impedance of a 2000 kVA oil immersed transformer?
Units in this series are supplied with a short circuit impedance of 6% at 2000 kVA, while the wider range of ratings is offered between 4% and 6%.
Q: Which vector group is used for photovoltaic and storage duty?
Dyn11 is the standard connection, and other groups including Yyn0 can be produced where the network protection scheme requires them.
Q: What losses should be expected at 2000 kVA?
No-load loss is approximately 1380 W and load loss at 75 °C is approximately 19140 W, with a no-load current of about 0.5% of rated current.
Q: Which insulating oil grade is required?
Grade 25 oil covers ordinary ambient conditions, while grade 45 oil is used where the minimum ambient temperature is below -25 °C.
Q: Can the high voltage side reach 35 kV?
Yes. High voltage ratings up to 35 kV are available, with 50 Hz or 60 Hz operation and a tapping range of plus or minus 2 x 2.5% as standard.
Q: What degree of enclosure protection is available?
The transformer can be supplied as an open IP00 unit or with an IP20 or IP23 protective enclosure, and cooling can be arranged as ONAN or ONAF to match the load profile.