PowerNex power transformers are high-performance oil-immersed power transformers engineered for medium voltage power systems up to 35 kV, supporting both step-up transformers and step-down transformer applications. Designed for utility power transformers, industrial power transformers, and infrastructure substations, our solutions deliver stable voltage transformation, low loss performance, and long-term operational reliability.
Covering a broad range of kVA ratings, three-phase power transformer configurations, and customized voltage ratios within ≤35 kV, PowerNex supplies liquid-immersed power transformers built to meet ANSI, IEC, and IEEE standards. As a trusted power transformer manufacturer and supplier, we provide factory-direct production, project-based customization, and global delivery for utility grids, industrial plants, renewable energy facilities, and transmission-distribution networks worldwide.
Oil-Immersed Medium Voltage Power Transformers for Utility and Industrial Systems
Power transformers rated up to 35 kV are a critical component of medium-voltage power networks, enabling stable and efficient voltage transformation between sub-transmission and distribution levels. These transformers are widely used in utility substations, industrial power systems, renewable energy facilities, and infrastructure projects where long-term reliability, thermal stability, and electrical safety are essential.
PowerNex designs and manufactures oil-immersed power transformers for medium-voltage applications up to 35 kV, covering commonly used voltage classes such as 6.6 kV, 10 kV, 11 kV, 13.8 kV, 20 kV, 22 kV, and 35 kV. Each unit is engineered for continuous-duty operation and outdoor service, delivering dependable performance under diverse grid and environmental conditions.
Technical Specifications – Power Transformers (Up to 35 kV)
General Electrical Parameters
| Item | Specification |
|---|---|
| Transformer Type | Oil-Immersed Medium Voltage Power Transformer |
| Rated Voltage Class | Up to 35 kV |
| Rated Capacity Range | 500 kVA – 40 MVA |
| Phase | Three Phase |
| Frequency | 50 Hz / 60 Hz |
| Cooling Method | ONAN (standard) / ONAF (optional) |
| Insulating Fluid | Mineral Oil (standard), Natural Ester / Synthetic Ester (optional) |
| Installation | Outdoor (standard), Indoor on request |
| Duty | Continuous duty (24/7 operation) |
Voltage Ratings
| Side | Voltage Options |
|---|---|
| High Voltage (Primary) | 6.6 kV / 10 kV / 11 kV / 13.8 kV / 20 kV / 22 kV / 35 kV |
| Low / Medium Voltage (Secondary) | 0.4 kV / 3.3 kV / 6.3 kV / 6.6 kV / 10 kV / 11 kV / 13.8 kV / 20 kV |
| Voltage Function | Step-Down or Step-Up |
| Tap Changer | Off-Circuit Tap Changer (OCTC) / On-Load Tap Changer (OLTC, optional) |
| Tapping Range (Typical) | ±2×2.5% / ±5% (customizable) |
Insulation & Thermal Performance
| Item | Specification |
|---|---|
| Insulation System | Oil-paper insulation |
| Insulation Class | Class A (standard) |
| Temperature Rise (Oil / Winding) | 60K / 65K (or as specified by standard) |
| Ambient Temperature | Up to 40 °C (higher on request) |
| Altitude | ≤1000 m (higher altitude design available) |
Core & Winding
| Item | Specification |
|---|---|
| Core Material | CRGO Silicon Steel |
| Core Construction | Step-lap core, low loss design |
| Winding Material | Copper (standard) / Aluminum (optional) |
| Short-Circuit Strength | Designed to meet IEC / IEEE short-circuit withstand requirements |
| Sound Level | Compliant with IEC / IEEE limits |
Tank & Accessories
| Item | Specification |
|---|---|
| Tank Type | Welded steel tank |
| Surface Treatment | Shot blasting + anti-corrosion coating |
| Protection Devices | Oil level indicator, temperature indicator, pressure relief device |
| Monitoring (Optional) | Winding temperature sensors, remote alarm contacts |
| Enclosure Protection | Outdoor weatherproof design |
Standards & Testing
| Item | Specification |
|---|---|
| Design Standards | IEC 60076 / ANSI / IEEE C57 |
| Routine Tests | Ratio, resistance, losses, insulation, applied & induced voltage |
| Type / Optional Tests | Temperature rise, lightning impulse, sound level |
| Quality Control | Factory testing before shipment |
Electrical Ratings and Design Scope
Rated Power Range
PowerNex power transformers are available across a broad capacity range to meet the needs of different load centers and system configurations:
-
Rated Capacity: 500 kVA to 40 MVA
-
Phase: Three-phase
-
Frequency: 50 Hz / 60 Hz
Custom capacity ratings and special duty designs are available upon request.
Voltage Configuration
-
High Voltage (Primary): Up to 35 kV
-
Medium / Low Voltage (Secondary):
0.4 kV, 3.3 kV, 6.3 kV, 6.6 kV, 10 kV, 11 kV, 13.8 kV, 20 kV, 22 kV -
Voltage Function: Step-down or step-up transformation
These configurations allow seamless integration into regional utility grids and industrial power systems worldwide.
Oil-Immersed Technology for Medium Voltage Reliability
Insulation System
PowerNex power transformers utilize a proven oil-paper insulation system that delivers high dielectric strength, stable thermal performance, and long service life.
-
Insulating Fluid Options:
-
Mineral oil (standard)
-
Natural ester or synthetic ester (optional for enhanced fire safety and environmental performance)
-
Cooling Methods
-
ONAN (Oil Natural Air Natural) for standard continuous operation
-
ONAF (Oil Natural Air Forced) for higher load or overload requirements
These cooling methods ensure efficient heat dissipation and operational stability in medium-voltage environments up to 35 kV.
Core and Winding Engineering
Magnetic Core Design
-
High-grade CRGO silicon steel
-
Optimized magnetic flux density
-
Reduced no-load losses and low acoustic noise
Winding Structure
-
Copper or aluminum windings
-
Mechanical reinforcement for axial and radial forces
-
High short-circuit withstand capability
This design approach ensures reliable operation during normal service conditions as well as during grid disturbances.
Voltage Regulation and Control
PowerNex power transformers are designed to maintain stable output voltage across varying load conditions.
-
Off-Circuit Tap Changer (OCTC): Standard configuration
-
On-Load Tap Changer (OLTC): Optional for applications requiring dynamic voltage regulation
Tap changer arrangements are customized according to grid requirements and operational needs.
Manufacturing Process and Quality Assurance
Manufacturing Process
Each power transformer is manufactured under strict quality control procedures:
-
Core cutting, stacking, and clamping
-
Precision winding and insulation application
-
Core-coil assembly and vacuum drying
-
Vacuum oil filling and sealing
-
Tank fabrication, surface treatment, and final assembly
Testing and Standards
All PowerNex power transformers are tested in accordance with international standards, including:
-
IEC 60076
-
ANSI / IEEE C57
Routine and type tests verify electrical performance, insulation integrity, thermal behavior, and mechanical strength before delivery.
Applications
PowerNex power transformers up to 35 kV are widely used in:
-
Medium-voltage utility substations
-
Industrial power distribution systems
-
Renewable energy substations (solar and wind)
-
Infrastructure and transportation projects
-
Grid expansion and modernization programs
Customization and Global Supply
As a dedicated medium-voltage power transformer manufacturer, PowerNex provides factory-direct solutions for global customers:
-
Custom voltage ratios and impedance design
-
Selection of cooling methods and accessories
-
Optional ester insulation and protection devices
-
OEM and project-based manufacturing
-
Global logistics and technical support
Our transformers are supplied to projects across North America, South America, Europe, Southeast Asia, the Middle East, and other international markets.
Why Choose PowerNex
-
Specialized focus on power transformers up to 35 kV
-
Proven oil-immersed transformer technology
-
Compliance with international standards
-
Strong engineering and manufacturing capability
-
Reliable long-term performance in utility and industrial applications
PowerNex – Reliable Power Transformation up to 35 kV
PowerNex power transformers deliver stable, efficient, and dependable voltage transformation for modern medium-voltage power systems. Designed for reliability and built to international standards, our transformers support the safe and efficient operation of utility grids and industrial facilities worldwide.
Contact PowerNex today to discuss your project requirements and receive technical support and a factory-direct quotation.