750 kVA Oil-Immersed Distribution Transformer
Nov 06, 2025
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Product Overview
The 750 kVA oil-immersed distribution transformer is a three-phase, 50 Hz unit that steps down a 13.2 kV primary voltage to a 300 V secondary voltage for industrial and utility distribution networks. This model is widely used in urban and rural power grids, substations and factory power distribution systems where a compact, low-maintenance transformer with good overload capability is required.
GNEE Electric manufactures and supplies oil-immersed distribution transformers in the 750 kVA class in accordance with IEC 60076, with copper windings, grain-oriented silicon steel cores and fully sealed tanks.
Key Features
Low no-load loss core built from high-grade grain-oriented silicon steel laminations.
Layered high-voltage winding with high mechanical strength and balanced impulse distribution, giving strong short-circuit withstand capability.
Fully sealed structure with vacuum oil filling, isolating the mineral oil from ambient air to retard aging and moisture ingress.
Standard protection and monitoring accessories: pressure relief valve, oil temperature signal thermometer, gas (Buchholz) relay and oil level gauge.
Corrugated steel tank with good heat dissipation, high mechanical strength and leak-free welding.
Compact footprint and low audible noise for installation close to load centres.
Technical Parameters
| Parameter | Value |
|---|---|
| Model | S11-750-13.2/0.3 |
| Type | Three-phase oil-immersed distribution transformer |
| Rated capacity | 750 kVA |
| Primary voltage | 13,200 V |
| Secondary voltage | 300 V |
| Winding material | Copper |
| Vector group | Dyn11 |
| Frequency | 50 Hz |
| Insulating oil | Mineral oil (IEC 60296) |
| Cooling method | ONAN |
| Impedance voltage | 5.50% |
| Load loss | 8250 W |
| No-load loss | 980 W |
| Reference weight | 2240 kg |
| Reference dimension | 1685 x 1185 x 1340 mm |
| Manufacturing standard | IEC 60076 |
Application Scenarios
Typical installations of a 750 kVA oil-immersed transformer include:
Rural and urban distribution substations.
Industrial plants and mining sites with a 13.2 kV incoming supply.
Commercial complexes and residential districts with medium-voltage distribution.
Export projects for utilities and EPC contractors in Southeast Asia, Africa and Latin America.
Selection and Installation Points
Check the actual load profile: the economic loading range for this class is usually 60-80% of rated capacity.
Verify that the vector group (Dyn11) matches the existing network configuration and protection settings.
Provide adequate ventilation for ONAN cooling and maintain clearance around the tank and bushings.
Perform routine oil sampling and dissolved-gas analysis per IEC 60422 to monitor insulation condition.
FAQ
Q: What does the 5.50% impedance voltage mean?
A: It is the percentage of rated primary voltage needed to circulate rated current with the secondary short-circuited; it determines the fault current level and voltage regulation.
Q: Can the 750 kVA transformer operate at 60 Hz?
A: It is designed for 50 Hz; a 60 Hz application requires a re-designed core and a verification of insulation and loss values by the manufacturer.
Q: What is the difference between the S9, S11 and S13 series?
A: The series number indicates the no-load loss level: S11 has lower no-load loss than S9, and S13 lower still, following the loss grading of GB/T 6451-type requirements.
Q: Is mineral oil the only insulating option?
A: No. Silicone or ester fluids can be specified for high-fire-risk or environmentally sensitive sites, with a modified tank design.
Q: How often should the transformer oil be tested?
A: Typically once a year for distribution transformers, or according to the utility maintenance program, following IEC 60422.
Q: What accessories are fitted as standard?
A: Pressure relief valve, oil thermometer, gas relay, oil level gauge and drain/sampling valve.