Compared to oil-immersed transformers, Dry-type transformers have significant advantages in four core dimensions: fire safety, flexible installation, environmental friendliness and maintenance-free operation, and suitability for special environments.   1. Intrinsically Safe: Oil-free, Non-flammable, and Non-explosive No flammable liquids: Dry-type transformer windings are directly insulated with epoxy resin or NOMEX paper, eliminating the risk of leakage, combustion, or explosion. Zero Firefighting Burden: No need for emergency oil tanks, sump pits, sprinkler systems, or firewalls; can be directly installed in buildings, basements, shopping malls, hospitals, data centers, subway stations, and other densely populated areas. In the event of a fire in an oil-immersed transformer, the oil will spread, burn, and release toxic fumes; Dry-type transformers completely avoid this.   2. Extremely Flexible Installation Location Can be installed close to the load center: Dry-dry transformers can be placed in the middle of a floor, inside a shaft, or in a corner of the machine room, without requiring a separate transformer room (provided ventilation is sufficient). Unrestricted by height/number of floors: Oil-cooled transformers are generally only installed on the ground floor or one basement level (considering oil tank and transportation), while dry-dry transformers can be installed on the roof or equipment floor of high-rise buildings. Small footprint: Without oil tankers, radiators, oil conservators, gas relays, and other accessories, the structure is compact.   3. Simple Operation and Maintenance, No Leakage Risk Oil-Free Handling: No need for regular oil sample filtering, oil breakdown voltage testing, oil level replenishment, or leak repair. No Seal Aging Issues: Oil-lubricated transformers are most susceptible to leaks due to aging gaskets; Dry-type transformers completely eliminate this problem. Routine Inspections Only Require Checking the Temperature Controller and Fan; Almost No Consumables Required.   4. Environmental Protection and Cleanliness No Oil Pollution: Even after dismantling, there is no waste oil disposal issue, and copper and silicon steel sheets are recycled more cleanly. No Odor or Oil Vapor Emissions: Suitable for air-sensitive environments such as food factories, pharmaceutical workshops, and precision electronics cleanrooms.   5. Strong Short-Circuit Resistance (Under Certain Structures) The windings of resin-cast Dry-type transformers are integrally cured, resulting in extremely high mechanical strength. Their ability to withstand short-circuit electrodynamic forces is superior to that of hydraulic transformers of the same capacity (hydraulic transformer windings are loose and secured by pressure pins). In industrial and mining power distribution systems subjected to frequent short-circuit impacts, Dry-type transformers often have a lower failure rate.   6. Controllable Partial Discharge Level The vacuum casting process can control partial discharge to a very low level (≤5 pC), and its tolerance to high-frequency harmonics and operating overvoltages is better than that of oil-cooled transformers (partial discharge in oil-cooled transformers tends to increase with the deterioration of oil quality).

1. No-load loss Po – basically at the same level Po mainly depends on the core material and the design magnetic flux density. For the same efficiency class, Oil-immersed transformers and Dry-type transformers use the same level of cold-rolled grain-oriented silicon steel sheets (CRGO) or even amorphous alloys, so Po can be very close. 2. Load Loss Pk – Oil-immersed transformers have an advantage at "actual operating temperature" This is the key point of divergence: Oil-immersed: Winding heat is quickly carried away by the oil, resulting in uniform oil temperature and more controlled hot spot temperatures. Resistance temperature rise is relatively controllable ⇒ R(T) in Pk = I²R(T) won't spike too high. Dry-immersed (epoxy resin cast SCB): Although F-class (155℃)/H-class (180℃) insulation materials allow for higher temperatures, for lifespan management, the control system usually keeps the winding temperature within a more conservative range (e.g., ≤120~130℃ long-term). Once it approaches the threshold, it will limit the load or force the fan to stop running at full speed. Result: With the same conductor quantity and design margin, the Pk of an oil-immersed transformer is more likely to stabilize at a lower effective value during long-term high-load operation – this is not due to "different copper wires," but rather a more powerful heat sink. 3. Heat dissipation determines a hidden efficiency factor: "Available Overload Efficiency". This means that if your load characteristics are consistently high (>75%), the overall operating efficiency curve of a hydraulic transformer will look better and be more durable than that of a dry-type transformer. Conversely, if the load rate fluctuates at a low to medium level year-round, the efficiency difference between the two will be minimized.   In short, efficiency isn't a difference in label between oil-immersed and Dry-type transformers, but rather a difference in the matching of operating conditions. Oil-immersed transformers excel in "lower overall losses and larger thermal margins under high load rates and long operating times"; Dry-type transformers excel in "maintenance-free operation, cleanliness, safety, and comparable efficiency under reasonable load rates (avoiding pushing the limits). What truly drags down efficiency is never the type itself, but rather—two mismatches: overloading (powering up a small load while the transformer is underutilized) or underloading (overheating and limiting the load capacity).

Advantages and disadvantages of Oil-Immersed Transformers：*Advantages: Strong heat dissipation and overload capacity: The insulating oil has extremely high heat dissipation efficiency, can withstand short-term overloads, and is suitable for applications with large load fluctuations. Large capacity and high voltage level: Mature technology allows for the manufacture of transformers with extremely large capacity and extremely high voltage levels, making it the core of power transmission and transformation systems. Good insulation performance: The oil dielectric has high insulation strength, effectively protecting the internal windings. Lower initial cost: For the same capacity, its manufacturing and purchase costs are generally lower than those of dry-type transformers. Low operating noise: The oil dampens the vibration of the core and windings, resulting in relatively quiet operation.   *Disadvantages: Fire Risk: Insulating oil is flammable and may cause fires or even explosions in the event of a malfunction, requiring extremely high fire safety standards. Complex Maintenance: Requires regular monitoring of oil level, temperature, and quality (e.g., water content, acidity), and professional maintenance such as oil filtration and replenishment. Leakage Risk: Aging seals may lead to oil leaks, polluting the environment and requiring remediation. High Installation Requirements: Typically requires a separate distribution room or outdoor platform, and an emergency oil tank. Environmental Issues: Waste insulating oil is hazardous waste and requires professional recycling and disposal.   Advantages and disadvantages of Dry-type transformers： *Advantages: Safe and Fireproof: Contains no flammable liquids, especially the epoxy resin cast type which is flame-retardant and explosion-proof, allowing direct installation at load centers (e.g., indoors, within buildings). Maintenance-Free and Easy Installation: Requires no oil level or quality monitoring, essentially maintenance-free; simple structure and easy installation. Environmentally Friendly and Clean: No risk of oil leaks, no toxic gases, environmentally friendly. Good Overload Capacity (New Models): Modern design with improved heat dissipation significantly enhances overload capacity. High Adaptability: Excellent moisture resistance, suitable for harsh environments such as humid and dusty conditions (requires appropriate protection level).   *Disadvantages: Lower heat dissipation efficiency: Relying on air cooling, its heat dissipation capacity is inferior to oil cooling, and its overload capacity is still inferior to Oil-Immersed Transformers transformers of the same capacity. Limited capacity and voltage: Due to limitations in heat dissipation and insulation materials, the capacity and voltage rating of a single unit are usually lower than those of Oil-Immersed Transformers transformers. Higher initial cost: For the same capacity, the price is usually higher than that of Oil-Immersed Transformers transformers. Higher operating noise: Vibrations of the core and windings are directly transmitted through the air, resulting in relatively high noise levels. Sensitive to the operating environment: Open-ventilated (non-enclosed) types are susceptible to dust and moisture, requiring the environment to be kept clean.   In summary: The key to choosing a substation lies in balancing safety, cost, and the environment. For outdoor or stand-alone substations prioritizing large capacity, low cost, and high efficiency, choose Oil-Immersed Transformers; for indoor or densely populated locations prioritizing high safety, maintenance-free operation, and environmental friendliness, choose dry-type substations.