National Standard for Transformer Methyl Silicone Oil Under Revision; Fire Resistance and Insulation Performance to Be Enhanced


      The National Energy Administration has recently issued its 2024 plan for formulating and revising industry energy standards, notably including the revision of the standard for "Insulating Oil – Methyl Silicone Oil." This signals that with the rapid development of urban power grids and offshore wind power, stricter requirements are being placed on the fire safety and long-term operational reliability of insulating oils for transformers and other power equipment, positioning methyl silicone oil as a key material due to its excellent flame-retardant properties and environmental friendliness.
      Conventional mineral transformer oil, while inexpensive, has a low flash point (typically below 160°C). An internal arc discharge within a transformer can easily lead to fire or explosion. In contrast, high-purity methyl silicone oil has a flash point exceeding 300°C, an auto-ignition temperature above 400°C, and releases less heat during combustion than mineral oil. Classified by the International Electrotechnical Commission (IEC) as a K-class (high fire point) insulating liquid, it is becoming mandatory for use in high fire-risk locations such as urban underground substations, indoor distribution rooms of high-rise buildings, and nacelles of offshore wind turbines. Methyl silicone oil is gradually replacing certain synthetic ester insulating liquids as the preferred choice for these scenarios, offering superior cost-effectiveness.
      However, some technical shortcomings of methyl silicone oil in practical applications must be addressed. For instance, its low tolerance for moisture means that trace amounts of water can significantly reduce its breakdown voltage. Furthermore, compatibility issues with certain rubber seals inside transformers can lead to swelling or shrinkage with long-term exposure. A key focus of this standard revision is to add detailed test methods and limit values for moisture content, dielectric dissipation factor, and compatibility with sealing materials. The revision also encourages the use of modified methyl silicone oils with polar groups to improve electrical stability in micro-water environments. With the implementation of the new national standard, it is expected that the penetration rate of high-quality methyl silicone oil in high-end distribution equipment will increase from the current level below 15% to over 30%.