250kVA 33kv To 400V Oil Immersed Three Phase Distribution Transformer

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250kVA 33kv To 400V Oil Immersed Three Phase Distribution Transformer

The 250kVA 33kV to 400V Oil Immersed Three Phase Distribution Transformer is designed for medium-voltage power distribution in industrial facilities, commercial buildings, utility networks, and local distribution systems. With a rated capacity of 250kVA, a primary voltage of 33kV, and a secondary voltage of 400V, the transformer provides a practical solution for stepping down medium-voltage electricity to a low-voltage supply for downstream loads.

The transformer uses a cold-rolled grain-oriented silicon steel (CRGO) core and carefully designed windings to provide stable electrical performance and controlled transformer losses. The oil immersed construction provides insulation and heat dissipation for the core and windings, while the ONAN (Oil Natural Air Natural) cooling method allows heat to be removed through the natural circulation of insulating oil and surrounding air.

The transformer is suitable for applications where reliable 33kV to 400V power conversion is required. Depending on the project requirements, the unit can be configured with different tap ranges, vector groups, impedance values, winding materials, protection devices, and monitoring accessories.

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Model:
S-250-33/0.4
Brand:
YAWEI
Code:
-

250kVA Distribution Transformer 33kV 400V Transformer Oil Filled Transformer

PRODUCT CATEGORY

>> Product Introduction

>> Technical Parameters

>> Product Uses

>> Product Operate Guide

>> FAQ

>> Product Introduction

The 250kVA 33kV to 400V Oil Immersed Three Phase Distribution Transformer is designed to step down a 33kV medium-voltage supply to 400V for local power distribution and low-voltage electrical loads. With a compact three-phase oil immersed construction, the transformer provides reliable voltage conversion and stable power delivery for industrial facilities, commercial buildings, local substations, infrastructure projects, and other distribution applications.

The transformer uses an oil immersed insulation and cooling system to provide effective heat dissipation for the core and windings during normal operation. Its practical structure allows the transformer to be installed in different distribution environments while maintaining reliable electrical and mechanical performance. The transformer can be configured according to project requirements, including tap range, vector group, impedance, winding material, protection devices, and monitoring accessories.

Designed for 33kV medium-voltage distribution systems, the transformer provides a suitable solution where a 400V low-voltage supply is required for downstream equipment, lighting systems, motors, pumps, and general electrical loads.

Product Advantage

1. Reliable 33kV to 400V Voltage Conversion

The transformer converts the 33kV medium-voltage supply to 400V low-voltage power, providing a suitable voltage level for local distribution networks and downstream electrical equipment.

Its three-phase configuration is suitable for balanced three-phase loads and can be integrated into industrial, commercial, utility, and infrastructure power systems. The voltage ratio and tap arrangement can be configured according to the requirements of the electrical network.

2. Compact Oil Immersed Construction

The oil immersed design combines electrical insulation and heat dissipation in a single system. Transformer oil transfers heat generated by the core and windings to the tank and cooling surfaces, helping maintain appropriate operating temperatures during continuous service.

The relatively compact structure of the 250kVA transformer makes it suitable for local substations and distribution installations where available space and equipment footprint are important considerations.

3. Stable Electrical Performance

The magnetic core is manufactured using cold-rolled grain-oriented silicon steel (CRGO), while the windings can be supplied with copper or aluminum conductors according to the approved technical specification.

The core and winding structure is designed to provide stable voltage transformation, appropriate insulation clearances, and reliable mechanical strength. The transformer's impedance, vector group, and other electrical parameters can be selected according to the characteristics of the connected power system.

4. Natural Cooling and Simple Operation

The transformer can adopt an ONAN (Oil Natural Air Natural) cooling arrangement. Under normal operating conditions, insulating oil circulates naturally inside the tank, transferring heat from the active parts to the external cooling surfaces.

This cooling method has a relatively simple construction and does not require forced oil circulation or cooling fans for normal operation, reducing auxiliary equipment requirements and simplifying routine maintenance.

5. Protection and Monitoring Options

The transformer can be equipped with protection and monitoring components according to the installation requirements. Available options may include:

Oil temperature indicator
Oil level indicator
Pressure relief device
Buchholz relay, where applicable
High-voltage and low-voltage bushings
Grounding terminals
Oil drain and sampling valves
Surge protection
Overcurrent and short-circuit protection
Optional transformer monitoring system

The final protection configuration can be selected according to the customer's electrical protection scheme and applicable project standards.

6. Flexible Configuration for Distribution Projects

The 250kVA 33kV to 400V Oil Immersed Three Phase Distribution Transformer can be configured for different installation and operating conditions.

Depending on the project requirements, options may include different:

Tap ranges
Vector groups
Short-circuit impedance values
Winding materials
Insulation levels
Protection devices
Monitoring systems
Cooling configurations

This flexibility allows the transformer to be adapted to different industrial, commercial, utility, and infrastructure distribution systems.

>> Technical Parameters

Type	Three‑phase oil‑immersed distribution transformer
Model	S-250-33/0.4
Installation	Outdoor
Altitude	≤1000m
Rated Power	2800 kVA KVA or others
Cooling Method	ONAN
Primary Voltage	33 kV
Secondary Voltage	0.4 kV
Rated Frequence	50/60HZ
Insulation oil	Mineral oil
Tapping Range	±2×2.5%/±5%
Temperature rise℃)	65 K
Connection Group
Total weight(kg)	~ 1866 kg (depends on final design)

>> Product Uses

1. Urban Power Distribution

Steps down 33kV medium-voltage power to 400V for residential communities, commercial buildings, public facilities, and local distribution networks. Its three-phase configuration provides a practical solution for supplying low-voltage feeders from medium-voltage grid systems.

2. Industrial Power Supply

Provides 400V power for factories, workshops, processing facilities, pumps, motors, lighting systems, and other industrial loads. The oil immersed design offers effective insulation and heat dissipation for continuous operation under normal industrial loading conditions.

3. Commercial & Building Applications

Suitable for shopping centers, office buildings, hotels, schools, and other commercial or public facilities requiring a reliable 400V electrical supply. The transformer can be integrated with downstream switchgear, distribution panels, motor control equipment, and other low-voltage systems.

4. Rural & Remote Electrification

The 33kV/400V voltage ratio makes the transformer suitable for local substations and rural electrification projects where medium-voltage power needs to be distributed to low-voltage users. Its oil immersed construction provides a practical solution for long-term outdoor or substation operation when properly configured for the installation environment.

5. Infrastructure & Utility Projects

Suitable for water treatment plants, transportation facilities, municipal buildings, communication facilities, and other infrastructure projects requiring dependable medium-voltage to low-voltage power conversion. Optional monitoring and protection equipment can be supplied according to the project's electrical system and operating requirements.

>> Product Operate Guide

1. Transportation

Instructions for lifting, handling, loading, unloading, and transportation of the transformer. The unit should be handled using the designated lifting points and protected against excessive vibration, impact, tilting, and mechanical damage.

2. Delivery Inspection

Inspection of the transformer and supplied accessories upon arrival, including the tank, bushings, radiators, valves, terminals, nameplate, packing list, factory test documents, and other components. Any transportation damage, oil leakage, deformation, or missing accessories should be recorded before installation.

3. Storage

Requirements for temporary or extended storage before installation. The transformer should be stored in a suitable location and protected against moisture, dust, contamination, corrosion, and mechanical damage.

4. Installation Environment Requirements

Requirements for the installation foundation, ventilation, drainage, grounding, electrical clearances, ambient temperature, altitude, humidity, pollution level, and available maintenance space. The actual installation conditions should comply with the approved technical documentation.

5. Electrical Installation

Instructions for connecting the 33kV high-voltage side and 400V low-voltage side, including phase identification, cable connections, grounding, protection circuits, control wiring, and terminal tightening. All electrical connections should be inspected before energization.

6. Common Components

Overview of commonly supplied transformer components and accessories, which may include:

High-voltage bushings
Low-voltage bushings
Oil tank
Radiators
Oil level indicator
Oil temperature indicator
Pressure relief device
Buchholz relay, where applicable
Tap changer
Grounding terminals
Oil drain and sampling valves
Protection and monitoring devices

The actual configuration shall be based on the approved transformer drawings and technical specification.

Product Video

>> FAQ

How long do Yawei transformers last?

Built for 40 years with routine care. Quality core materials and winding techniques keep thermal stress low, extending insulation life beyond typical industry averages.
What upkeep is needed?

Check oil level/temp daily; test oil annually; inspect bushings and seals yearly; perform major filtration every 5 years; replace dial gauges at decade intervals.
How does it work?

AC in the primary creates a varying magnetic field in the core, inducing voltage in secondary coils. Our split design gives two separate 0.6 kV outputs from one 10 kV input.
How to pick the right model?

Match primary/secondary voltages and kVA to your load; consider cooling, altitude, and ambient range. Our Dy11d0 type excels with harmonic‑heavy loads like VFDs.
Why choose Yawei transformers?

Over 31 years in business, 240 k m² facility, IEC/IEEE compliance, full customization, 2.5 billion RMB annual sales, and proven reliability in utilities and industry worldwide.