The lifespan of a transformer refers to the time it takes for its insulation system to lose its insulating properties due to heat aging. Dry-type transformers are classified according to the heat resistance of their insulation materials as follows: Temperature Class – Class B (130℃), Class F (155℃), Class H (180℃), Class C (220℃). ① Class B insulation products are early manufactured products with poor performance indicators, failing to meet the requirements of modern power supply. ② Class F products have relatively better performance and are easier to industrialize. The main representative is the Class F thin-insulated epoxy resin vacuum-cast product. my country imported this production technology extensively in the late 1980s and early 1990s, therefore, most dry-type transformers currently used domestically are of this type. ③ Class H insulation products are a new technology from the 1990s in China, at a world-leading level. They are widely used in developed countries such as the United States, where they account for approximately 70% of the dry-type transformer market. Although China started later, its outstanding reliability, safety, economy, and environmental friendliness have attracted widespread attention, leading to its application in many important settings, such as Tiananmen Square, the Secretariat of the Central Committee of the Communist Party of China in Zhongnanhai, the Chinese Academy of Sciences, and the Diaoyutai State Guesthouse in Beijing. Compared to the SCB10 epoxy-cast dry-type transformer, the SGB10 open-ventilated dry-type transformer has the following characteristics:
1. H-class insulation: The SGB10 open-ventilated dry-type transformer achieves an insulation heat resistance class of H or even higher, class C. The epoxy-cast dry-type transformer (SCB10 type) is class F. This means that under normal operating conditions, the SGB10 type has a longer service life than the SCB10 type, and possesses stronger resilience and self-breakdown capability under extreme conditions such as output load short circuits;
2. Safety: The SGB10 dry-type transformer is currently the safest dry-type transformer available. All insulation materials are flame-retardant, self-extinguishing, and non-toxic. Its combustible content is less than 10% of that in epoxy-cast products. Even after prolonged combustion at 800℃, no toxic fumes are produced, overcoming the defect of the original epoxy-cast dry-type transformer (SCB10 type) which produced a large amount of toxic gases during combustion. The SGB10 dry-type transformer is widely used in subways, airports, buildings, residential areas, ships, chemical plants, and metallurgical plants.
3. Reliability: The special coil design, process, and materials of the SGB10 dry-type transformer give it excellent three-proof performance (moisture-proof, mildew-proof, and salt spray-proof), making it more resistant to thermal shock, crack-free, and virtually free of partial discharge (unlike epoxy resin cast dry-type transformers which may experience minor partial discharge).
4. Environmental Protection: The SGB10 is recyclable after reaching its lifespan, overcoming the environmental pollution caused by the resin and glass fibers of epoxy resin cast transformers, which are not decomposable after their lifespan due to the fusion of resin and glass fibers.
5. Strong Overload Capacity: The SGB10 dry-type transformer adopts a new structure, new materials, and new process, with excellent heat dissipation, long thermal life, and extremely strong overload capacity. It can operate in an IP23 (water spray) environment and can operate safely and reliably for a long time under 120% overload. 6. No forced air cooling is required, yet it can still operate at full load for extended periods (while all manufacturers advise against long-term full-load operation of the SCB10 model, and it requires intelligent temperature control with forced air cooling to ensure operation under relative overload conditions, and can operate normally in an environment with 95% relative humidity);
7. Smaller size and lighter weight: The SGB10 dry-type transformer uses NOMEX paper as the main insulation material and incorporates mixed insulation at the hottest points of the transformer, resulting in a size and weight reduction of more than 2% compared to epoxy-cast transformers of the same capacity;
8. New non-magnetic structure: The SGB10 dry-type transformer uses low-magnetic-permeability materials for clamps, tie plates, etc., eliminating stray losses, reducing load losses, and improving the economic efficiency of transformer operation.
References and materials:
1. GB 1094.1-1996 "Power Transformers - Part 1: General Principles"
2. GB 1094.5-2008 "Power Transformers - Part 5: Short Circuit Withstand Capacity"
3. GB1094.11-2007 "Power Transformers - Part 11: Dry-Type Transformers" (replacing GB6450-86)
4. GB/T10228-2008 "Technical Parameters and Requirements for Dry-Type Power Transformers"
