Oil-immersed transformers come in a wide variety of models and specifications, covering different capacities, voltage levels, and structural types. The following provides a detailed explanation from five aspects: model classification, parameter ranges, structural characteristics, energy efficiency grades, and selection recommendations.

　　I. Model Classification and Representative Products

　　1. Non-enclosed Oil-immersed Transformers

　　Models: S8, S9, S10, S13, etc.

　　Characteristics: Simple structure, low cost, suitable for general applications in industrial and mining enterprises, agriculture, and civil buildings.

　　Example: S13-1000/10 (capacity: 1000 kVA, voltage level: 10 kV).

　　2. Enclosed Oil-immersed Transformers

　　Models: S9-M, S10-M, etc.

　　Characteristics: Enhanced sealing performance to prevent oil contamination and chemical erosion, suitable for harsh environments such as petroleum and chemical industries.

　　Example: S9-M-630/10 (capacity: 630 kVA, fully sealed structure).

　　3. Sealed Oil-immersed Transformers

　　Models: BS9, S11-MR, SH, SH12-M, etc.

　　Characteristics: Utilize corrugated tank full-sealing technology to automatically adjust oil volume changes, enabling maintenance-free operation and suitable for various power distribution scenarios.

　　Example: SH15-M-500/10 (capacity: 500 kVA, amorphous alloy core, energy-saving type).

　　II. Parameter Ranges and Specifications

　　1. Capacity Ratings

　　Small Transformers: ≤630 kVA (e.g., 160 kVA, 250 kVA, 400 kVA).

　　Medium Transformers: 800 kVA–6300 kVA (e.g., 800 kVA, 1000 kVA, 1600 kVA).

　　Large Transformers: 8000 kVA–63000 kVA (e.g., 10000 kVA, 20000 kVA).

　　Extra-large Transformers: ≥90000 kVA (e.g., 120000 kVA, 180000 kVA).

　　2. Voltage Levels

　　Input Voltage: 220 kV, 110 kV, 35 kV, 10 kV (commonly used).

　　Output Voltage: 35 kV, 10 kV, 6 kV, 0.4 kV (commonly 10 kV/0.4 kV).

　　3. Dimensions (Examples)

　　1000 kVA Transformer: Length × Width × Height ≈ 1865 mm × 1295 mm × 1650 mm (specific dimensions vary by model and manufacturer).

　　6300 kVA Transformer: Length × Width × Height ≈ 6400 mm × 5600 mm × 5900 mm (110 kV class).

　　III. Structural Characteristics and Design

　　1. Core Materials

　　Utilize imported cold-rolled silicon steel sheets or amorphous alloys to reduce no-load losses and operational noise.

　　Example: The core losses of the S11 transformer are reduced by over 30% compared to the S9 model.

　　2. Winding Structures

　　High-Voltage Side: Multi-layer cylindrical design with a Dyn11 connection group to minimize grid harmonic effects.

　　Low-Voltage Side: Configured with double-layer cylindrical or spiral windings based on capacity to balance mechanical strength and heat dissipation performance.

　　Example: The S11-2000/10 transformer features a multi-layer cylindrical design on the high-voltage side and a spiral winding on the low-voltage side.

　　3. Cooling Methods

　　Oil-Immersed Natural Cooling (ONAN): Suitable for small to medium-capacity transformers, relying on natural convection for heat dissipation.

　　Oil-Immersed Forced Cooling (ONAF): Optional for large-capacity transformers, using fans for forced heat dissipation.

　　IV. Energy Efficiency Grades and Standards

　　1. Energy Efficiency Classification

　　Grade 1 (Highest Efficiency): S22, SCB18 (lowest losses, significant energy-saving effects).

　　Grade 2 (Balanced Performance and Cost): S20, SCB14.

　　Grade 3 (Basic Energy-Saving Models): S13, SCB12.

　　Example: The S22-M-630/10 (Grade 1 efficiency) reduces no-load losses by approximately 20% compared to the S13 model.

　　2. Applicable Standards

　　National Standards: GB 1094 (General Requirements for Power Transformers), GB/T 6451 (Technical Parameters for Three-Phase Oil-Immersed Transformers).

　　Industry Specifications: GB/T 15164 (Load Guide), JB/T 501 (Test Guide).

　　V. Selection Recommendations

　　1. Capacity Matching

　　Reserve a margin based on load type; motor starting requires an additional 20%–30% capacity.

　　Example: To drive a 500 kW motor, an 800 kVA transformer is recommended (accounting for starting current).

　　2. Voltage Compatibility

　　Ensure the high-voltage side matches the mine grid voltage and the low-voltage side supports the equipment connection method (Y/Δ).

　　Example: For a mine grid voltage of 10 kV and equipment requiring 400 V (Δ connection), a 10/0.4 kV transformer should be selected.

　　3. Environmental Adaptability

　　Altitude: ≤1000 m (derating required for higher altitudes).

　　Temperature: Maximum ambient temperature of +40°C, minimum of -25°C (forced oil circulation cooling required for high-temperature environments).

　　Humidity: Relative humidity ≤95% (at 25°C).

　　Protection Level: IP45 (dust and water resistance) or higher (e.g., IP54 for specific scenarios).

　　4. Special Requirements

　　Explosion-Proof Requirements: For mine environments, select explosion-proof transformers (e.g., ExdIIBT4).

　　Customization: Contact manufacturers for non-standard capacities, voltages, or tap ranges (e.g., ±4×2.5%).