Home > 11–35kV Oil Immersed Distribution Transformer
Product Description:
STELLAR high-efficiency oil immersed distribution transformers operate at rated voltages from 11kV to 35kV with capacities ranging from 30kVA to 2,500kVA. The core is constructed using premium cold-rolled grain-oriented silicon steel to minimize losses. Windings are available in high-conductivity copper or aluminum with Dyn11 or Yyn0 connections. We offer both hermetically sealed and conservator-type tank structures to suit different project requirements. These units are highly reliable for outdoor and indoor installations in urban, rural, and industrial distribution networks operating at 50Hz or 60Hz.
Available Configurations
• Single phase and three phase
• Hermetically sealed (corrugated tank) or conservator type
• No-load tap changer ±5% or ±2×2.5%
• On-load tap changer optional
• ONAN cooling standard, ONAF optional for higher loads
• Special environment codes: P (plateau), C (anti-corrosion), T (dry tropics), H (humid tropics)
Ordering Information
Tell us your rated voltage (HV/LV), capacity, frequency, winding material preference, connection group, installation altitude, and ambient temperature range. Our engineering team will confirm the full specification and provide a GA drawing for your approval before production.
| TECHNICAL PARAMETERS (11-35kV OIL IMMERSED TRANSFORMER) | |
|---|---|
| Rated Voltage (HV) | 11kV - 35kV |
| Rated Capacity | 30 - 2500 kVA |
| Rated Frequency | 50Hz / 60Hz |
| Vector Group | Dyn11, Yyn0 |
| Cooling Method | ONAN / ONAF |
| Tank Type | Hermetically Sealed / Conservator Type |
| Installation Environment | Outdoor / Indoor |
The core is meticulously stacked from high-quality cold-rolled grain-oriented silicon steel laminations, cut at 45-degree mitered joints to significantly reduce flux leakage at the corners. The laminations are coated with a specialized insulating film and securely clamped with robust steel structural parts. This precise clamping design not only controls core vibration but also ensures the operating noise is kept to a minimum while maintaining high energy efficiency.
High voltage windings utilize a multi-layer cylindrical construction with oxygen-free copper wire or electrical-grade aluminum wire, depending on your specifications. Low voltage windings feature foil winding or layer winding based on the current rating. All windings undergo a rigorous vacuum drying and vacuum oil impregnation process to completely remove moisture and air pockets from the insulation, ensuring maximum dielectric strength.
Hermetically Sealed: These units feature corrugated tank walls that naturally expand and contract with oil temperature fluctuations. Without a conservator or breather, the oil never comes into contact with the atmosphere, ensuring a maintenance-free lifespan and preventing oil degradation.
Conservator Type: Designed with a separate oil expansion tank equipped with a silica gel breather, this traditional setup is ideal for specific utility standards requiring atmospheric breathing and easy oil sampling.
This distribution transformer is engineered for reliable outdoor or indoor installation under standard conditions. If your site falls outside these ranges, STELLAR can customize the design with derating, enhanced insulation, or special environmental protection.
• Ambient temperature: -25°C to +40°C
• Altitude: ≤1000m above sea level (derating applied above 1000m per IEC guidelines)
• Humidity: monthly average ≤90%, daily average ≤95%
• Installation environment: no severe vibration, no explosive or corrosive gases
For plateau, anti-corrosion, dry tropic, or humid tropic conditions, we apply the corresponding environmental treatment to the insulation and paint systems.
Our 11-35kV oil immersed distribution transformers are widely used in urban and rural power grids, industrial plants, infrastructure projects, and commercial facilities to step down high voltage transmission lines to usable distribution voltages.
A hermetically sealed tank uses corrugated fins to absorb oil expansion and isolates the oil entirely from the air, making it virtually maintenance-free. A conservator type uses a separate expansion tank with a breather, which is often preferred by certain utility standards for easy oil level monitoring and sampling.
Yes, STELLAR offers full customization. Depending on your budget and technical requirements, we can manufacture the windings using either high-conductivity oxygen-free copper or electrical-grade aluminum, with capacities ranging from 30kVA up to 2500kVA.
The standard units operate reliably between -25°C and +40°C. For extreme environments like high-altitude plateaus, highly corrosive coastal areas, or tropical zones, STELLAR applies specialized anti-corrosion paints and enhanced insulation designs to ensure long-term stability.
