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.

Silicon steel (electrical steel) • Characteristics: Silicon steel is the most traditional core material. By adding silicon (typically 3% to 5%), the resistivity is increased to reduce eddy current losses while maintaining high magnetic permeability. Cold-rolled silicon steel sheets have grain orientation, which can further optimize the magnetic flux path. • Advantages: Low cost, high mechanical strength, and mature manufacturing process, suitable for power frequency (50/60Hz) applications. • Disadvantages: Iron losses significantly increase at high frequencies (hysteresis loss + eddy current loss), and efficiency is lower than that of new materials. • Applications: • Power transformers (distribution and transmission systems); • Industrial transformers (medium and low-frequency equipment). 2. Amorphous Alloy (Amorphous Steel) • Characteristics: Metal glass structure with disordered atomic arrangement (such as iron-boron-silicon alloy), isotropic magnetism, significantly reducing eddy current and hysteresis losses. Iron loss is 70% to 80% lower than that of silicon steel. • Advantages: Ultra-high efficiency (extremely low no-load loss), environmentally friendly and energy-saving. • Disadvantages: High mechanical brittleness, difficult processing, relatively low saturation magnetic flux density (about 1.5T), and cost is 1.5 to 2 times that of silicon steel. • Applications: • High-efficiency distribution transformers (especially in energy-saving scenarios); • Renewable energy systems (photovoltaic inverters, wind power transformers).   3. Ferrite •Characteristics: Ceramic material (MnZn/NiZn-based), high resistivity (>10^6 Ω·m), naturally suppresses eddy currents, but magnetic permeability varies significantly with temperature. •Advantages: Excellent high-frequency performance (1kHz - 1MHz), small size, moderate cost. •Disadvantages: Low saturation flux density (<0.5T), brittle, not suitable for high-power low-frequency applications. • Applications: • Switching power supplies (SMPS), RF transformers; • Consumer electronics (chargers, TVs, communication devices). 4.Nanocrystalline Materials • Characteristics: Nanoscale crystalline structure (iron-based alloys), combining high saturation flux density (over 1.2T) with low high-frequency losses and good temperature stability. • Advantages: Comprehensive performance surpasses ferrite, high-frequency losses comparable to amorphous alloys. • Disadvantages: High cost, complex mass-production processes. • Applications: • High-end high-frequency transformers (medical equipment, aerospace); • Electric vehicle charging modules.   Other Materials • Iron Powder Cores: Used in mid-frequency inductors, strong anti-saturation capability but higher losses. • Permalloy (Nickel-Iron Based): Extremely high initial permeability, used in precision instruments, but with exceptionally high cost.