Technical Requirements for Mine Transformers

　　Mine transformers, as core power supply equipment in explosive environments such as coal mines, must meet stringent technical requirements centered on explosion safety, environmental adaptability, performance reliability, and regulatory compliance. The specific technical requirements are as follows:

　　1. Explosion-Proof Performance Requirements

　　a. Flameproof Structural Design

　　The enclosure joint surfaces must comply with explosion-proof standards (e.g., GB 3836.1-2021) and withstand internal explosion pressures (typically ≥0.8 MPa) without rupture, preventing flame and hot gas escape.

　　High-voltage/low-voltage outlet boxes shall incorporate electrical interlock mechanisms to automatically cut off power when opened, accompanied by "No Live Opening" warning labels.

　　Emergency Stop Button: The high-voltage side terminal box must be equipped with an emergency stop button for rapid disconnection of the high-voltage input power.

　　b. Enclosure Protection Rating

　　The overall enclosure must pass a 1 MPa hydrostatic pressure test for 1 minute without leakage or deformation.

　　Protection rating shall reach IP54 or higher to prevent dust and water ingress, with certain models (e.g., KBSGZY series) supporting IP68 submersible operation.

　　2. Environmental Adaptability Requirements

　　a. Temperature and Humidity Tolerance

　　Operable ambient temperature range: -5°C to +40°C, with relative humidity ≤95% (at +25°C).

　　Windings shall use Class H insulation materials (temperature resistance ≥180°C) to adapt to high-temperature underground environments.

　　b. Mechanical Strength and Seismic Resistance

　　The enclosure shall adopt a corrugated steel plate structure for high mechanical strength, capable of withstanding vibrations and impacts during transportation and operation.

　　The oil tank of general-purpose mine transformers must resist 0.1 MPa pressure without deformation to ensure stable internal oil pressure.

　　c. Corrosion and Moisture Resistance

　　The enclosure shall be constructed from stainless steel or galvanized steel plates, with flameproof surfaces treated with phosphating for rust prevention.

　　Windings shall be impregnated with moisture-resistant insulating varnish to prevent insulation degradation due to moisture ingress.

　　3. Electrical Performance Requirements

　　a. Voltage and Capacity Matching

　　Input voltage: 6 kV/10 kV; output voltage: 400 V, 660 V, 1,140 V, 3,450 V, etc., to meet underground equipment demands.

　　Capacity range: 2.5 kVA to 2,500 kVA, selected based on load type (e.g., lighting, coal mining machines, ventilation fans).

　　Example: The KBSG-315/10 transformer has a capacity of 315 kVA, a primary voltage of 10 kV, a secondary voltage of 3.3 kV, and a short-circuit impedance of 5%.

　　b. Energy Efficiency and Losses

　　Priority shall be given to Class 1 energy efficiency models (e.g., SH15-M series), which reduce no-load losses by 80% and load losses by 15% compared to S9 series.

　　No-load loss example: The KBSG-400/10 transformer has no-load losses ≤1,350 W.

　　c. Overload Capacity

　　Short-term overload of 20%–30% (for 2 hours) is permitted to accommodate underground load fluctuations.

　　Temperature rise limit: Winding temperature rise ≤80 K (Class F insulation) to ensure long-term operational stability.

　　4. Safety Protection and Monitoring

　　a. Temperature Monitoring

　　Temperature sensors shall be embedded in the windings for real-time monitoring, with data transmitted to a superior control system.

　　Alarms or trips shall be triggered if temperatures exceed rated values to prevent overheating-induced accidents.

　　b. Multi-Layer Protection Functions

　　Equipped with sudden pressure relays and pressure relief valves to prevent excessive internal tank pressure.

　　Short-circuit impedance and load losses must comply with standards (e.g., KBSG-500/6 has a short-circuit impedance of 4.5%) to avoid short-circuit damage.

　　c. Oil Level and Pressure Regulation

　　Traditional oil conservators are eliminated, with automatic oil level and pressure regulation achieved via expansion radiators.

　　The oil level indicator integrates oil injection, vacuum evacuation, and oil replenishment functions to prevent moisture ingress.

　　5. Structural and Installation Requirements

　　a. Low-Profile Design

　　Adapted to underground tunnel height limitations, featuring a larger core diameter and cold-rolled silicon steel sheets to reduce noise and no-load losses.

　　Example: The KS9 transformer measures 950 × 600 × 850 mm and weighs 365 kg, facilitating rail transportation.

　　b. Cable Terminal Boxes

　　High-voltage/low-voltage inlets and outlets shall use cable terminal boxes filled with insulating compound for sealing.

　　Cable outer diameter compatibility range: 32–95 mm² for main circuits (rubber-sheathed cables) and 14.5–21 mm² for control circuits.

　　c. Flameproof Surface Treatment

　　All flameproof surfaces must undergo phosphating for rust prevention, with bolts of strength grade ≥8.8 to ensure long-term explosion-proof performance.

　　6. Regulatory Compliance and Certification

　　a. National Standard Compliance

　　Must adhere to standards such as GB 3836 (explosive environment equipment) and MT/T 661 (coal mine electrical equipment).

　　General-purpose mine transformers must comply with AQ 1070-2009 safety technical requirements.

　　b. Certification and Markings

　　Must obtain a Mine Product Safety Mark Certificate (MA mark) and explosion-proof certification.

　　Factory testing shall include DC resistance imbalance tests and induced voltage withstand tests.

　　7. Maintenance and Reliability

　　a. Periodic Inspections

　　Quarterly testing of insulation resistance (≥100 MΩ) and grounding resistance (≤4 Ω).

　　Annual oil analysis and infrared inspections to monitor busbar connections and bushing integrity.

　　b. Long-Life Design

　　Fully sealed structures prevent oil degradation, with a service life ≥20 years.

　　Core-free inspection design reduces on-site maintenance workload.