1. Basic Information

Model: Recommended as KS11-M-2000/10(6), or customized according to customer requirements. (“M” denotes mining use, and “10(6)” indicates that the high-voltage side can accommodate either a 10 kV or 6 kV system; this is an example.)

Product Name: General-Purpose Oil-Immersed Power Transformer for Mining Applications (with Oil Conservator).

Rated capacity: 2000 kVA.

Number of phases: 3-phase.

Frequency: 50 Hz or 60 Hz (must be specified; China uses 50 Hz, while some countries use 60 Hz).

2. Voltage and Tap Settings

High-voltage side voltage (HV): 10 kV or 6.6 kV, 11 kV, 13.8 kV, etc. (must be fully compatible with the target country’s grid voltage level). Common configurations include on-load or no-excitation tap changers with a regulation range of ±2×2.5% or ±5% at 10 kV.

Low-voltage side voltage (LV): 0.4 kV (400 V) or 0.69 kV (690 V). The 690 V rating is commonly used in the international mining industry to reduce losses due to high currents.

Winding connection group designation: Dyn11 is strongly recommended. Its advantages include suppression of third-harmonic currents, provision of a stable neutral point, and strong capability to withstand unbalanced loads; it is the internationally accepted standard.

3. Performance Parameters

Impedance voltage (Uk): 6% or 6.5%. This value must be matched to the protection settings of downstream equipment (such as switchgear) and provide adequate short-circuit current limitation.

Cooling method: ONAN (oil-immersed self-cooling).

Insulation level:

High-voltage side (LI/AC): For a 10 kV system, it is typically 75 kV / 35 kV.

Low-voltage side (LI/AC): For example, in a 0.4 kV system, it is typically 5 kV / 3 kV.

Must comply with IEC 60076 or an equivalent standard.

4. Losses and Efficiency (Key Economic Indicators)

No-load loss (Po): Must comply with the low-loss or high-efficiency class requirements specified in IEC 60076-1 (e.g., Ck or C0k values). For a 2000 kVA transformer, Po shall not exceed 1800 W (the exact value is dependent on the silicon steel sheet material and manufacturing process and constitutes a key negotiation point).

Load loss (Pk at 75°C): shall not exceed 17,000 W (dependent on copper usage and design).

No-load current (Io): typically < 0.8%.

5. Structural and Material Requirements (Critical for Export and Mining Applications)

Core: Made from high-quality, low-loss, grain-oriented cold-rolled silicon steel sheets, such as 30ZH120 or higher grades.

Windings: Both the high-voltage and low-voltage windings shall use electrolytic copper conductors (a specific requirement to prevent the substitution of aluminum for copper). Vacuum impregnation or continuous winding methods shall be employed to enhance mechanical strength and short-circuit withstand capability.

Insulating oil: high-quality mineral oil compliant with IEC 60296. Oil sample test reports are provided. In consideration of environmental protection requirements, biodegradable ester-based oils may be specified.

Fuel Tank and Protection:

Fuel tank: fully sealed corrugated-type fuel tank (maintenance-free) or fuel tank with an oil conservator and desiccant breather. Given the harsh mining environment, it is recommended to equip the tank with an oil conservator to ensure pressure balance.

Protection rating: IP65 (dustproof and waterproof) or at least IP54. The enclosure must be robust, with marine-grade, heavy-duty anti-corrosion paint (C5-M environmental standard) to withstand maritime salt spray and underground dampness.

Protection device:

Gas relay (Buchholz relay): Must be provided for protection against internal faults.

Pressure relief valve: Must be provided.

Oil level gauge: magnetic oil level gauge with temperature indication.

Thermometers: winding thermometer (WTI) and oil-surface thermometer (OTI), with 4–20 mA output and alarm/trip contacts.

Terminals: The high-voltage bushings and low-voltage terminal blocks shall be securely fastened and easy to connect. Given the large currents on the low-voltage side, the dimensions of the copper busbars must be clearly specified.