High-temperature immersed Transformers are designed to incorporate mature structures and processes traditionally used in transformers, retaining the reliability, excellent craftsmanship, and cost-effectiveness associated with traditional transformers. The key difference lies in the thoughtful consideration of the actual temperature distribution within the transformer. By using different insulation materials of varying temperature resistance levels according to the rational temperature distribution, a hybrid insulation system is formed.
Leveraging transformer temperature field simulation technology,it accurately determines the temperature distribution (primarily around windings and nearby areas), allowing the selection of insulation materials of different temperature grades based on varying temperature ranges. This maximizes the high-temperature resistance characteristics of the materials while maintaining good cost-effectiveness. The maximum operating oil temperature of this immersed transformer is set at 95°C, ensuring its excellent safety, thermal performance margins, and an extended expected lifespan.
For the temperature design of the entire transformer unit, we have introduced and adhered to the concept of "Seven-Step Temperature Control Technology" as a design principle. This involves dividing the design into five levels extending from the hottest winding hotspot to the cooler external regions and considering short-circuit and overload conditions to form a seven-level thermal state for temperature control design:
1. Insulation Temperature Control Technology: Different insulation materials are used for winding and body insulation based on their respective temperature areas. Controls the winding hotspot temperature.
2. Liquid Flow Circuit Temperature Control Technology: This integrates the temperature and flow rate fields of the liquid, determining and controlling the temperature of various liquid flows. Controls the boundary layer liquid temperature near the winding hotspot and the top layer liquid temperature.
3. Overload Temperature Control Technology: Controls temperature rise at various transformer parts under overload conditions. Temperature distribution under overload is different from that under rated load operation; changes in temperature rise under overload conditions should be taken into account during design.
4. Iron Core Temperature Control Technology: Controls the temperature of insulation components in contact with the Iron core.
5. Sealing Temperature Control Technology: Manages the thermal expansion, deformation, strength, etc., of fully sealed oil tanks, and their effects and controls with temperature variations, ensuring normal operation within the allowed temperature range.
6. Component Temperature Control Technology: Selects insulation materials of corresponding grades for components based on their location's temperature, such as sealing gaskets.
7. Short-Circuit Temperature Control Technology: When a short-circuit fault occurs in the transformer, a large short-circuit current flows through the winding, but for a very short time. It is generally calculated using adiabatic process considerations. Accumulation and heat dissipation effects should be considered under repeated short-circuit reclosure conditions. Generally, NOMEX® paper boasts excellent high-temperature resistance, mechanical strength, and minimal variation in dielectric constant and dielectric loss with temperature changes. Even under multiple short-circuit reclosure conditions, it does not cause mechanical damage or electrical faults due to temperature rise, nor does it compromise the insulation material's lifespan.