I. Domestic Core Standards (Most Authoritative, Essential)
1. General Principles and Fire Hazard Assessment (Product Level)
NB/T 11307.2-2024 "Guidelines for Fire Hazard Assessment of Electrical Equipment and Materials Part 2: Oil-Immersed Transformers"
Core: The only standard specifically for fire hazard assessment of oil-immersed transformers.
Content: Flash point of insulating oil, electric arc in oil, combustion of solid materials, overall fire risk classification (Levels I–V)
Applicable to: 10kV and above oil-immersed transformers/reactors
2. Insulating Oil Safety Testing (Most Critical)
GB/T 261-2021 "Determination of Flash Point - Binsky-Martin Closed Cup Method"
Judgment: Mineral oil ≥140℃; High flash point oils (esters/silicone oils) ≥250℃
GB 2536 "Electrical Fluids" 1. **Unused Mineral Insulating Oil for Transformers and Switches:** Specifies basic safety indicators for the oil (flash point, ignition point, breakdown voltage, etc.).
NB/T 11307.2 Supporting Standard: Arc Test in Oil (simulates internal fault arc to assess the decomposition/combustion/explosion risk of the oil).
3. **Flame Retardant Testing of Solid Insulating Materials:** GB/T 2408 *Plastics—Determination of Flammability—Horizontal and Vertical Methods* (corresponding to UL 94)
Grades: V-0 (Best), V-1, V-2, HB
GB/T 5169 Series (Fire Hazard Testing for Electrical and Electronic Products)
Glow Wire (IEC 60695-2-12), Needle Flame, Tracking, etc.
GB/T 18380 *Cables—Burning Tests under Flame Conditions* (Winding Insulation, Leads, etc.)
4. **Overall Heat Release and Fire Risk:** ISO 5660-1 / GB/T 16172 *Test Method for Heat Release Rate of Building Materials (Cone Calorimeter)*
Determination: Peak Heat Release Rate (PHRR) ≤ 200 kW/m² (avoid flashover)
GB 50229-2019 *Fire Protection Design Standard for Thermal Power Plants and Substations*
Specifies requirements for fire separation distances, oil containment basins, and fire protection facility configuration (not laboratory testing, but core to fire protection compliance)
II. International Mainstream Standards (Essential for Foreign Trade/Export)
1. IEC System (Globally Applicable)
IEC 61936-1 *Substations*: Fire separation distances and risk levels are classified according to total oil volume.
IEC 60695 Series: Fire Hazard Testing of Electrical Products (Glow Wire, Needle Flame, Hot Wire, etc.)
IEC 61558-2-3: Safety of Power Transformers, Power Supply Equipment, etc. (including limits for toxic gases: HCN ≤ 50 ppm)
2. UL / ASTM System (North American Market)
UL 94: Vertical/Horizontal Burning of Plastic Materials (V-0) (For highest flame retardancy)
ASTM D93: Flash Point Test (corresponding to GB/T 261)
ASTM D635: Horizontal Burning Rate (corresponding to GB/T 2408)
ASTM E84: Surface Burning Characteristics of Building Materials (for enclosures/structural components)
III. Quick Overview of Test Standards and Items (Directly for the Test Checklist)
Table Test Category Core Standard Key Items Acceptance Criteria
Insulating Oil Safety GB/T 261, GB 2536, NB/T 11307.2 Flash Point, Ignition Point, Arc in Oil Flash point ≥140℃; no violent combustion/explosion under arc
Flame Retardancy of Solid Materials GB/T 2408, UL 94, GB/T 5169 Vertical/Horizontal Burning, Glow Wire V-0 Class; does not ignite with a 960℃ glow wire
Overall Heat Release ISO 5660-1, GB/T 16172 Peak Heat Release Rate (PHRR) ≤200kW/m² Fire Hazard Assessment NB/T 11307.2-2024 Comprehensive Classification (Level I–V) Risk level matched to voltage/capacity
Engineering Fire Protection Compliance GB 50229, IEC 61936-1 Fire Separation Distances, Oil Baffles, Fire Protection Meets the required spacing and facility requirements
IV. Summary in One Sentence (For Direct Use by Clients/Tender Documents)
Oil-immersed transformers do not have a unified fire protection rating. Core testing revolves around oil flash point, UL 94 flame retardancy of materials, overall heat release, and NB/T 11307.2 fire hazard classification. The final risk assessment is based on Levels I–V to guide fire protection design and application scenarios.
