EN
The selection of cast resin dry transformers is no longer a simple matter of merely considering capacity and voltage. In 2026, with the full implementation of the new energy efficiency standard GB/T 10228-2023 and the tightening of global carbon emission policies, the selection of transformers also needs to take into account the entire life cycle of the transformers. The following five key factors are the selection dimensions that engineers and purchasing personnel must review one by one in 2026.
1. Energy Efficiency Grade
Energy efficiency is the top priority in the selection process for 2026. According to national standards, dry-type transformers are classified into three levels of energy efficiency: level one, level two, and level three. The higher the level, the lower the no-load loss and load loss. Many purchases only compare the purchase price but ignore the characteristic of the transformer operating continuously for 24 hours. Taking an 800kVA transformer as an example, compared with level three energy efficiency, the annual electricity cost can be saved by several thousand yuan. The saved electricity cost over 3 to 5 years can cover the purchase price difference. For facilities such as hospitals and data centers that operate non-stop throughout the year, energy efficiency selection should give priority to level one or level two energy efficiency.
II. Insulation and Heat Resistance Classifications of Cast Resin Dry Transformer
The insulation class directly determines the transformer's ability to withstand high temperatures and its service life. Currently, the mainstream choices are F class (155℃) and H class (180℃). The F class has a balanced cost-performance ratio and is suitable for regular indoor factories and building power distribution; the H class has stronger resistance to high temperatures and overload, and is suitable for high-temperature workshops, poorly ventilated or high-humidity environments with harsh conditions. If the insulation class is selected too low, the equipment will easily age rapidly and even suffer insulation breakdown in high-temperature environments.
III. Short-circuit Impedance and Anti-Short-circuit Capacity
The short-circuit impedance (Uk%) is a key parameter that affects the safety and voltage stability of the system. Standard distribution transformers usually adopt a value of 4% to 6%. For large-capacity or systems requiring parallel operation, a recommended value of 6% to 8% is suggested. If the impedance is too low, the short-circuit current will be excessively large, which may easily damage the equipment; if the impedance is too high, the voltage loss will increase. In addition, the short-circuit tolerance capacity of the transformer must be verified - products that comply with the GB 1094.5 standard and can withstand a 2-second short-circuit impact can be used to cope with sudden grid failures and prevent winding deformation or equipment damage.
IV. Protection Level and Environmental Adaptability
Dry-type transformers are sensitive to the environment and their protection level must match the installation scenario. IP00 is only suitable for clean dedicated power distribution rooms; IP20 is the most common indoor option, which can prevent finger contact and foreign object intrusion; IP23 and above have the ability to resist rain and moisture, and are suitable for semi-outdoor or high-humidity environments. Choosing a low protection level for poor environmental conditions will cause the equipment to easily accumulate dust and get damp, leading to frequent faults such as leakage and tripping, and increasing maintenance costs.
V. Connection Group
The connection group directly affects the power supply quality, especially its adaptability to non-linear loads. Dyn11 is currently the mainstream choice, which can effectively suppress third harmonic, withstand three-phase unbalanced loads, and is suitable for scenarios with precision equipment such as data centers, hospitals, and office buildings; Yyn0 is only applicable to simple resistive loads like lighting and is not recommended for use in scenarios involving non-linear equipment such as frequency converters and rectifiers. Choosing the wrong group may lead to hidden problems such as equipment interference and tripping.
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Summary: In the selection of dry-type transformers for 2026, a comprehensive assessment based on five dimensions - energy efficiency, insulation, impedance, protection, and group classification - is required. The decision-making should be based on the total life cycle cost rather than solely focusing on the purchase price.
Jiangsu Unita Electric Equipment Co.,Ltd. can customize and provide 35kV and below distribution transformers according to your project requirements. If you need more information, please feel free to contact us at any time.
