II. Product Structure Options for 3.15 MVA Transformers

• 3.15 MVA Three-Phase Oil-Immersed Power Transformer (6kV – 35kV):
  The standard solution for outdoor substations. Features a corrugated tank or radiator-based cooling system (ONAN/ONAF) for excellent heat dissipation. Ideal for main step-down substations in factories and utility grids.
• 3.15 MVA Epoxy Resin Cast Dry-Type Transformer (6kV – 35kV):
  Designed for indoor or environmentally sensitive areas. Offers inherent flame retardancy, high short-circuit strength, and zero risk of oil leaks. Perfect for high-rise buildings, underground railways, and critical process industries.
• 3.15 MVA Pad-Mounted Transformer Substation (2.4kV – 34.5kV):
  A fully enclosed, tamper-proof unit integrating the transformer, HV switchgear, and LV distribution into a single weatherproof cabinet. Optimized for urban aesthetics, public parks, and commercial districts where ground space is limited.

III. Core Technical Advantages & Value Proposition

• Ultra-High Efficiency & Global Compliance:​ Achieves operating efficiency greater than 99%, comfortably meeting the stringent European Ecodesign Tier 2 energy efficiency regulations (2015/2014/548/EC). This translates to significant long-term energy savings and reduced carbon footprint.
• Maintenance-Free Hermetic Design (IP65):​ The tank is engineered with a fully sealed, IP65-rated enclosure. This prevents moisture ingress and oxidation of the insulating oil, virtually eliminating the need for routine oil maintenance and ensuring a robust service life exceeding 25 years.
• Enhanced Overload Capacity:​ The use of high-purity copper windings allows the 3.15 MVA transformer to handle short-term overloads up to 150%​ of its rated capacity for up to 2 hours. This provides critical headroom during peak demand periods or emergency contingencies, with continuous oil temperature monitoring (≤ 95°C) recommended.
• Eco-Friendly & Sustainable Operation:​ Optionally available with FR3 Natural Ester (Vegetable) Oil. This biodegradable fluid offers a higher flash point for improved fire safety and significantly extends the paper insulation life, aligning with green building and corporate sustainability goals.

IV. Price Factors & Industrial Purchasing Considerations

• Winding Material:​ Copper windings provide superior conductivity, lower load losses, and higher mechanical strength, representing a premium but high-value investment compared to aluminum alternatives.
• Cooling Method:​ ONAN (natural cooling) is standard for many applications, while ONAF (forced air cooling) adds fan units to boost continuous output capacity, increasing the unit cost.
• Regulation & Taps:​ On-Load Tap Changers (OLTC) allow for voltage regulation without disconnecting the load, adding complexity and cost compared to standard Off-Circuit Tap Changers (OCTC).
• Accessory Package:​ The inclusion of advanced monitoring (winding temperature indicators), protective relays (Buchholz, PRV), and specialized bushings will influence the overall price.
• Global Metal Markets:​ Fluctuations in the spot prices of copper and CRGO silicon steel directly impact the transformer’s final quotation.

• Main power distribution for medium-to-large factories and industrial parks.
• Primary power supply for large commercial buildings, hospitals, or university campuses.
• Voltage step-down in community-wide distribution systems and rural power grids.
• Step-up or step-down applications in solar farms and wind turbine collection systems.

• High Voltage (HV) Side:​ 10 kV (standard distribution voltage)
• Low Voltage (LV) Side:​ 0.4 kV (400V/230V three-phase four-wire system)

• High Voltage Side (10 kV):​ I = 3150 kVA / (1.732 * 10 kV) = 181.87 A
• Low Voltage Side (0.4 kV):​ I = 3150 kVA / (1.732 * 0.4 kV) = 4546.63 A

• Foundation:​ Must be level and capable of supporting the total weight (oil weight approx. 2000 kg for this size).
• Ventilation:​ Excellent airflow is required; maintain a minimum clearance of 0.8 meters from walls and ensure no obstructions above the radiator.
• Safety:​ Install away from flammable materials. Outdoor units require a rain cover or security fence.
• Protection:​ Mandatory fitting of a Buchholz relay, pressure relief valve, surge arrestors, and a proper grounding system (resistance ≤ 4Ω).