Complete Guide to 66kV Power Transformers: Core Features, Advantages, and Applications
Time：2025-12-19 Auther：ZTelec-www.ztelectransformer.com
With the growth of interconnected regional power grids, the integration of renewable energy sources, and the rapid upgrade of urban grids, 66kV power transformers have become essential for medium- and high-voltage transmission and distribution systems. These transformers enhance grid stability, improve transmission efficiency, and optimize operational economics. Compared to 35kV and 110kV transformers, 66kV units offer a balanced approach in terms of investment cost, technological maturity, and operational flexibility, making them suitable for a wide range of power projects.
Overview of 66kV Power Transformers
A 66kV power transformer operates at a rated high-voltage of 66kV and is mainly used for voltage conversion between regional transmission and distribution networks. It is widely adopted in regions such as Asia, Eastern Europe, the Middle East, and Africa, especially for medium-distance power transmission and regional grid nodes. Common types include 66kV oil-immersed transformers, two-winding or three-winding structures, and on-load (OLTC) or off-load (NLTC) tap-changing configurations.
Core Features of a 66kV Power Transformer
Structural Design
The transformer employs a multi-layered oil-paper insulation system for long-term stable operation. High-permeability, low-loss cold-rolled silicon steel cores reduce no-load losses and operating noise. Winding structures are designed as interlocking or continuous coils to improve short-circuit withstand capacity and operational stability. Cooling systems vary from oil-immersed self-cooling (ONAN) to oil-immersed air-cooling (ONAF), with large-capacity units using forced oil circulation systems.
Main Technical Parameters
Capacity ranges from 5MVA to 60MVA, with custom capacities available. Impedance voltage typically ranges from 8% to 12%, ensuring sufficient short-circuit performance. Voltage regulation can be achieved via no-load or on-load tap changers (OLTC), generally with a regulation range of ±8×1.25% or ±10%. Outdoor transformers are recommended to have a protection class of IP55 or higher for dustproof and waterproof reliability.
Intelligent Functions
66kV transformers integrate sensors for oil temperature, winding temperature, gas-in-oil analysis (DGA), and partial discharge, enabling real-time monitoring. They support IEC61850 protocols and can connect to intelligent substation control systems. Built-in health assessment algorithms allow predictive maintenance, reducing unexpected outages.
Technical Advantages
Balanced Transmission Efficiency and Economy
Compared to 35kV systems, 66kV transformers reduce transmission losses, while their construction costs are more controllable than 110kV systems, making them ideal for medium-sized grids.
Strong Environmental Adaptability
Sealed structures, moisture-proof design, and high-quality insulating oil ensure reliable operation in high/low temperatures, humid, dusty, and polluted environments.
Low Maintenance and Long Service Life
Rationally designed 66kV oil-immersed transformers offer service lifespans of 25-40 years with minimal maintenance requirements.
Support for New Energy Integration
66kV transformers serve as intermediate voltage equipment in wind, photovoltaic, and energy storage substations, enhancing grid flexibility and stability.
Typical Applications
Regional and urban main grids: Used in substations and key nodes for 110kV/66kV or 66kV/35kV conversion, ensuring reliable power distribution. Industrial and mining enterprises: Provides stable medium-voltage supply for steel, mining, chemical, cement, and other continuous-production industries. Renewable energy projects: Widely used in wind and solar farms, energy storage, and booster stations. Infrastructure and public works: Ideal for electrified railways, rail transit projects, and large-scale water conservancy projects.
Selection and Installation Considerations
Key Selection Factors
Analyze load characteristics, including load curves, harmonics, and impulse loads. Assess the installation environment considering space, temperature, and altitude. Reserve expansion capacity to accommodate future growth and ensure energy efficiency standards, prioritizing Level 1 efficiency products.
Installation Precautions
Foundations must be stable to support the transformer’s weight and short-circuit forces. Ensure sufficient clearance and ventilation for heat dissipation and maintenance. Strictly follow manufacturer guidelines for on-site testing and commissioning.
As power systems evolve toward high efficiency, intelligence, and low-carbon operations, 66kV power transformers continue to be vital for medium- and high-voltage transmission and distribution. Their mature technology, economic efficiency, and versatility make them essential equipment for public grids, renewable energy integration, and industrial power projects.
