15 MVA 33/11 kV & 33/6.6 kV On-Load Tap Changer Transformer

Medium Voltage Power Transformer for Substations and Industrial Applications

The 15 MVA 33/11 kV and 33/6.6 kV On-Load Tap Changer Transformer is a high-performance medium voltage power transformer designed for utility substations, industrial power systems, and renewable energy projects. This oil-immersed transformer efficiently steps down 33 kV transmission voltage to 11 kV or 6.6 kV distribution levels, ensuring a stable and reliable power supply for critical infrastructure.

Equipped with an advanced on-load tap changer (OLTC), the transformer can automatically regulate output voltage under load conditions without interrupting power supply. This makes it an ideal solution for modern power grids where voltage stability, efficiency, and operational continuity are essential.

Technical Specifications

Rated Power: 15 MVA power transformer
Transformer Type: Oil immersed transformer
Primary Voltage: 33 kV transformer
Secondary Voltage: 11 kV / 6.6 kV distribution transformer
Phase: Three phase transformer
Frequency: 50 / 60 Hz
Vector Group: Dyn11 / YNd11
Cooling Method: ONAN / ONAF
Tap Changer: On-load tap changer (OLTC)
Tap Range: ±10%
Tap Step: 1.25%
Impedance: 8% – 12%
Insulation Level: IEC standard
Standard: IEC 60076 power transformer

All technical parameters can be customized based on specific project requirements and grid conditions.

Core Engineering Features

On-Load Voltage Regulation

The integrated OLTC system enables real-time voltage adjustment without interrupting the power supply. This function is critical in utility substations and industrial applications where voltage fluctuations can impact equipment performance and grid stability.

Low-Loss Core Design

The transformer core is constructed using high-grade CRGO silicon steel, significantly reducing no-load and load losses. This results in improved energy efficiency, lower operating costs, and enhanced long-term performance in continuous power distribution operations.

Reliable Insulation System

A robust insulation structure combining high-quality transformer oil, electrical insulation paper, and pressboard components ensures excellent dielectric strength. This design guarantees safe and stable operation under high-voltage and heavy-load conditions.

Efficient Cooling Performance

The transformer supports both ONAN and ONAF cooling methods. Under normal load, natural oil and air cooling ensure efficient operation, while forced air cooling enhances heat dissipation during peak load conditions, extending transformer service life.

Heavy-Duty Tank and Protection System

Designed for outdoor installation, the transformer tank features a durable structure suitable for harsh environments. Integrated protection devices include Buchholz relay, oil level indicator, winding temperature indicator, pressure relief device, and silica gel breather, ensuring safe and reliable long-term operation.

Engineering Advantages

The OLTC transformer provides continuous voltage regulation, maintaining stable output even under fluctuating load conditions. Its optimized design reduces total power losses and improves overall system efficiency. High-quality materials and advanced manufacturing processes ensure a long service life of 20 to 30 years with proper maintenance.

This medium voltage transformer is highly adaptable and can be deployed in various power systems, including industrial networks, utility grids, and renewable energy integration projects.

Typical Applications

The 15 MVA power transformer is widely used in utility substations to step down transmission voltage for distribution networks. It is also essential in industrial facilities such as manufacturing plants, mining operations, and heavy industries where stable and continuous power is critical.

In renewable energy systems, including solar and wind power plants, the transformer plays a key role in connecting generation systems to medium voltage grids. It is also suitable for infrastructure projects such as airports, hospitals, data centers, and large commercial complexes requiring reliable power distribution.

Custom Transformer Solutions

We provide customized transformer solutions tailored to project-specific requirements. Options include different voltage configurations such as 33/11 kV and 33/6.6 kV, designs for tropical or coastal environments, corrosion-resistant tanks, and high-efficiency low-loss configurations. Customized OLTC systems are also available to meet various grid regulation needs.

Request a Technical Quotation

As a professional power transformer manufacturer, we offer complete support including technical consultation, custom design, competitive pricing, and global export services. Contact our engineering team today to receive a detailed technical proposal and quotation for your 15 MVA OLTC transformer project.