Fully enclosed power transformer

　　Fully Enclosed Power Transformers (Fully Sealed Transformers)

　　Fully enclosed power transformers are electrical devices that completely seal transformer oil, windings, and cooling systems within a metal enclosure, achieving complete isolation from the external environment through reliable sealing structures and high-voltage insulation materials. Their core advantages, technical features, and typical applications are outlined below:

　I. Core Advantages

　　1. Environmental Protection and Safety

　　The fully sealed structure prevents transformer oil leakage, avoiding soil and water contamination while reducing fire risks.

　　Suitable for environments with stringent environmental requirements, such as urban centers, residential areas, and ecologically sensitive zones.

　　2. Adaptability to Harsh Environments

　　Resistant to high altitudes, extreme cold, humidity, and salt spray corrosion, enabling stable operation at elevations above 2,000 meters and in temperatures ranging from -40°C to +50°C.

　　Typical Applications: Plateau regions, coastal wind farms, and chemical industrial parks.

　　3. Long Lifespan and Low Maintenance

　　Isolation of internal oil and insulation materials from air slows oxidation and moisture absorption, extending service life to over 20 years.

　　Designed for core-free inspection, reducing on-site maintenance workload and lowering lifecycle costs.

　　4. High Efficiency and Energy Savings

　　Certain models (e.g., SH15 series) reduce no-load losses by 80% and load losses by 15% compared to S9 series, meeting Class 1 energy efficiency standards.

　　Ideal for long-term operation, delivering significant electricity cost savings.

　　II. Technical Features

　　1. Structural Innovations

　　Elimination of Oil Conservator: Utilizes expansion radiators to automatically adjust tank pressure and oil level with temperature changes, avoiding leakage risks associated with traditional conservators.

　　Sealed Tank Cover and Flange: Features a dual-seal structure (e.g., rubber O-rings + sealant) to ensure long-term sealing performance and prevent ingress of external moisture and dust.

　　Anti-Loosening Fasteners: Internal bolts incorporate anti-loosening spring washers to prevent structural component loosening during transportation and operation.

　　2. Materials and Processes

　　High-Voltage Insulation Materials: Employs heat-resistant, arc-resistant epoxy resin or Nomex paper to enhance insulation reliability.

　　Nitrogen Filling: Pressurized nitrogen is filled inside the sealed enclosure to balance with the insulating oil, preventing oil degradation.

　　Protection Ratings: Enclosure protection reaches IP54 or higher, with some models (e.g., SRN-MD series) supporting submersible operation (IP68).

　　3. Intelligent Protection Systems

　　Equipped with sudden pressure relays, pressure relief valves, and temperature controllers for real-time monitoring of tank pressure and oil temperature, triggering alarms or trips during abnormalities.

　　Oil Level Indicator: Integrates oil injection, vacuum evacuation, and oil replenishment functions, serving as the sole external interface while maintaining a sealed state to prevent moisture ingress.

　　III. Typical Applications

　　1. Urban Power Grids

　　Used in municipal distribution networks to step down 10 kV high voltage to 400 V low voltage for residential and commercial supply.

　　Typical Model: SCBH15 series (dry-type, capacity: 30–3,150 kVA, voltage: 10 kV/35 kV).

　　2. Industrial and Renewable Energy

　　Industrial Power: Steps down high voltage for motors, furnaces, and other equipment.

　　Wind/Solar Power: Converts high voltage generated by renewable systems into transmission-ready low voltage.

　　Typical Model: SH15 series (oil-immersed, capacity: 30–2,500 kVA, voltage: 10 kV/20 kV).

　　3. Special Environments

　　Underground Substations: Models like SRN-MD series feature fully sealed designs to prevent flood damage, suitable for metro systems and tunnels.

　　High Overload Demands: Photovoltaic step-up transformers support 1.5× short-term overload, with sealed structures ensuring stability under high temperatures.

　　Railway Power Systems: Steps down 25 kV contact line voltage for locomotive use.

　IV. Selection Recommendations

　　1. Capacity Matching

　　Select a capacity 1.2–1.5× the total load power to avoid prolonged overload operation.

　　Example: A 1,000 kVA transformer can support approximately 800 kW of load.

　　2. Voltage Ratings

　　Choose 10 kV, 20 kV, or 35 kV based on grid requirements, ensuring high-voltage side compatibility with line voltage and low-voltage side alignment with equipment voltage.

　　3. Energy Efficiency Ratings

　　Prioritize Class 1 energy efficiency models (e.g., SCBH19, SH15-M) for lower long-term operational costs.

　　Example: A 1,000 kVA dry-type transformer (SCB14) has no-load losses ≤ 0.45 kW and load losses ≤ 3.2 kW.

　　4. Environmental Adaptability

　　Humid/Corrosive Environments: Opt for dry-type transformers (SCBH/SGBH series) with enhanced protective coatings.

　　Outdoor/High-Altitude Areas: Select oil-immersed transformers (SH15 series) with upgraded insulation (e.g., Class F).

　　Explosion-Proof Requirements: Choose mine-explosion-proof models (KSG series) or retrofit with explosion-proof enclosures.

　　5. Manufacturer and Certifications

　　Verify compliance with national standards such as GB/T 6451 (oil-immersed) and GB/T 10228 (dry-type).

　　Key Test Reports: No-load test, short-circuit test, and partial discharge (≤10 pC for dry-type).