In the intricate network of urban and rural power grids, S11 series oil-immersed transformers stand as the unassuming workhorses—bridging high-voltage transmission and low-voltage supply to ensure stable electricity reaches homes, factories, and public facilities. As a landmark energy-saving model in the power equipment industry, this series has earned its reputation with three core advantages: low-loss energy efficiency, hermetic sealing structure, and wide-scenario adaptability, becoming a cornerstone of reliable power distribution.
At the heart of the S11 series lies its low-loss energy efficiency, a trait achieved through innovative core design and material selection. Unlike traditional power transformers, it adopts either fully inclined three-seam stacked iron cores or seamless toroidal cores, where silicon steel sheets are continuously wound to optimize magnetic circuit distribution and minimize magnetic hysteresis loss. This design cuts no-load loss by 20% to 30% compared to older S9 series models and reduces no-load current by 60% to 80%—translating to significant electricity savings for utility companies during long-term operation. For example, a 1000 kVA S11 transformer has a no-load loss as low as 1.15 kW, far outperforming the energy consumption benchmarks of its era. This efficiency not only aligns with early national energy-saving policies but also laid the groundwork for subsequent high-efficiency transformer development.
The hermetic sealing structure is another defining feature that ensures the S11 series’ long-term reliability. It abandons the traditional oil conservator, instead using fully welded corrugated oil tanks where the tank cover and flange are either completely welded or bolted tightly. This design isolates the transformer oil from air and moisture, preventing oxidation and moisture absorption that would degrade insulation performance. The corrugated tank walls also act as natural radiators, enhancing heat dissipation efficiency to keep temperature rise 16-20K lower than conventional models. Combined with anti-corrosion treatments—including oil removal, derusting, phosphating, and triple anti-paint coating—the transformer resists industrial pollutants, coastal salt spray, and humid environments, making it suitable for metallurgy, petrochemical, and mining scenarios. Well-maintained units boast a service life of over 20 years, with no need for core lifting during maintenance, greatly reducing operational costs.
Strong wide-scenario adaptability has made the S11 series a staple in power distribution projects worldwide. Covering a capacity range of 30 kVA to 31500 kVA and voltage grades up to 35 kV, it fits diverse needs from residential communities to large industrial parks. Its compact size and lightweight design save installation space, while low noise (reduced by over 10 decibels compared to traditional models) make it ideal for urban residential areas. In rural power grid upgrades, it withstands harsh conditions like extreme temperatures and transportation vibrations thanks to reinforced internal positioning structures and locked fasteners. Even in renewable energy supporting systems, early S11 models laid the groundwork for subsequent adaptations, providing stable voltage conversion for distributed power generation nodes.
While the 2025 implementation of the new national standard GB 20052-2024 has phased out the S11 series from new production due to stricter energy efficiency requirements, its legacy endures in the vast number of in-service units and its influence on transformer design. Its integration of low-loss technology, hermetic reliability, and scenario flexibility set a benchmark for cost-effective power distribution equipment. For power engineers and maintenance teams, understanding the S11 series’ characteristics remains crucial for optimizing existing grid operations and appreciating the evolution of transformer energy efficiency.
In essence, the S11 series oil-immersed transformers are more than just electrical components—they are a symbol of the power industry’s shift toward energy conservation and reliability. Through low-loss energy efficiency, hermetic sealing structure, and wide-scenario adaptability, they have powered decades of urban development and rural electrification, cementing their status as a classic in power distribution history.
