Fire Safety Standards for Oil-Immersed Transformers
Oil-immersed transformers use insulating oil as both a cooling and insulating medium, posing fire risks. Therefore, strict adherence to fire safety standards in design, installation, and operation is critical. Below are key fire safety standards and related measures:
I. International Standards
1. IEC 60076 Series (Power Transformer Standards)
- Specifies fire-resistant design, temperature rise limits, and overload protection requirements.
- Emphasizes sealing, pressure relief devices, and fire isolation measures for oil-immersed transformers.
2. NFPA 850 (Fire Protection Standard for Power Plants)
- Requires safe distances between transformers and buildings, along with automatic fire suppression systems (e.g., water spray, foam systems).
- Defines fire-safe designs for oil containment facilities (e.g., oil pits must hold 100% of the transformer oil volume).
II. Chinese National Standards and Industry Codes
1. GB 50229 (Code for Fire Protection Design of Fossil Fuel Power Plants and Substations)
- Fire Separation Distance: Minimum spacing between oil-immersed transformers and buildings (e.g., ≥10 meters for single transformers with oil volume ≥1000 kg).
- Pressure Relief Facilities: Transformer rooms must include emergency oil drainage systems and barriers to prevent oil fire spread.
- Fire Suppression Systems: Large transformers require water spray, foam systems, or oil drainage and nitrogen injection systems.
2. GB 50148 (Code for Construction and Acceptance of Electrical Equipment Installation: Power Transformers)
- Installation requirements: Transformer foundations must be elevated to prevent flooding; oil containment facilities (e.g., pits, pipes) must meet fire safety standards.
3. DL/T 5218 (Technical Code for Design of 220kV–750kV Substations)
- Mandates firewalls or fire-resistant barriers between oil-immersed transformers in substations, with safe distances between multiple units.
III. Fire Protection Measures and Technical Requirements
1. Fire Separation and Layout
- Maintain safe distances between transformers, buildings, and other equipment (typically 5–15 meters, depending on oil volume).
- Install firewalls or barriers between multiple transformers (height ≥ oil conservator level).
2. Pressure Relief and Oil Containment
- Provide emergency oil sumps or pits with capacity ≥110% of the transformer oil volume.
- Equip with rapid oil drainage valves to divert oil to safe zones during fires.
3. Fire Suppression Systems
- Automatic Water Spray Systems: Activated by temperature or smoke detectors, covering the transformer body and oil conservator.
- Oil Drainage and Nitrogen Injection Systems: Drain oil and inject nitrogen to suppress combustion during fires.
- Foam Fire Extinguishing Systems: Suitable for oil fires (must maintain safe distances from transformers).
- Portable Fire Extinguishers: Place dry powder or CO₂ extinguishers near transformers.
4. Monitoring and Alarms
- Install gas relays (light gas alarms, heavy gas tripping), temperature sensors, and flame detectors.
- Integrate with fire alarm systems for real-time monitoring.
5. Fire-Resistant Materials and Structures
- Use fire-rated walls (≥2-hour fire resistance rating) and fire doors in transformer rooms.
- Seal cable trenches and pipe penetrations with fireproof sealants.
IV. Operational and Maintenance Requirements
1. Regularly inspect oil levels, temperature, and bushing seals to prevent leaks.
2. Clear flammable materials (e.g., weeds, debris) around transformers and ensure unobstructed fire access.
3. Test fire suppression and alarm systems annually and conduct fire drills.
V. Special Scenarios
- Underground Substations: Enhance mechanical ventilation and explosion-proof designs to prevent oil vapor accumulation.
- High-Risk Areas: Use flame-retardant insulating oils (e.g., β-fluid) or dry-type transformers as alternatives.