Comprehensive Comparison of Energy Efficiency Standards for Three-Phase Power Transformers

1. Overview

The national standard for "Minimum Allowable Values of Energy Efficiency and the Energy Efficiency Grades for Power Transformers" has undergone a major update. The new version, GB 20052-2024, was issued on April 29, 2024, and is scheduled for official implementation on February 1, 2025, at which time it will fully replace the current GB 20052-2020.

This revision aligns with China's "Dual Carbon" goals, aiming to further enhance the energy efficiency of power equipment, phase out outdated capacity, and incorporate transformers in the renewable energy sector into the management scope for the first time.

2. Key Technical Differences

2.1 Expanded and Adjusted Scope

GB 20052-2024 has made significant adjustments to its scope to adapt to modern power grid structures:

• New Inclusion: Specifically includes transformers designed for Photovoltaic (PV) and Wind Power generation. This will directly impact equipment selection for renewable energy power plants.
• Explicit Exclusions: Further clarifies that it does not apply to gas-insulated transformers (SF6), tower-mounted transformers, and nacelle transformers (usually constrained by heat dissipation and space).
• Refinement: Provides more detailed classifications for distribution and power transformers across voltage levels of 10kV, 35kV to 220kV.

2.2 "Upward Shift" of Energy Efficiency Grade Definitions

The new standard effectively sets the high-efficiency levels of the old standard as the new "entry-level" thresholds.

Note: Legacy models such as S11 and SCB10/11, which were widely used, now fall below the minimum allowable energy efficiency limit (Level 3) and will be prohibited from production and sale after February 2025.

2.3 Tightening of Loss Limits (P0​,Pk​)

The 2024 standard focuses on controlling No-load loss (P0​), encouraging the use of amorphous alloys and high-permeability silicon steel.

Comparison for a typical 10kV / 1000kVA transformer (approximate values):

2.4 Changes in Testing and Evaluation Criteria

• Renewable Energy Specific Evaluation: Accounting for the low-load operational characteristics (intermittency) of PV and wind power transformers, the new standard emphasizes reducing no-load losses to improve "all-day efficiency."
• Categorized Evaluation: The evaluation paths for oil-immersed and dry-type transformers are more distinct, considering their different thermal characteristics.
• Material Verification: Stronger requirements for verifying core materials (e.g., Amorphous Alloy vs. Silicon Steel) during the energy efficiency grading process.

3. Implementation and Recommendations

• Key Date: February 1, 2025.
• Existing Equipment: Equipment manufactured and labeled with energy efficiency stickers before this date can still be sold and used.
• Project Planning: It is recommended that electrical engineers adopt equipment complying with the GB 20052-2024 standard (especially for renewable energy projects) in current and future designs to ensure grid acceptance and potential green finance support.

4. Conclusion

The release of the GB 20052-2024 standard marks the official entry of China's transformer industry into the "High Energy Efficiency" era. For electrical engineers, it is necessary to focus not only on the efficiency improvements of traditional distribution transformers but also on technical selection for renewable energy supporting transformers, particularly in optimizing core materials and design processes to meet increasingly stringent no-load loss requirements.