GB/T 17623-2017 in English

This standard specifies the method and process for determining the content of dissolved gas components in insulating oil (including H₂, CH₄, C₂H₆, C₂H₄, C₂H₂, CO, CO₂, O₂ and N₂, etc.) by gas chromatography. It is suitable for fault diagnosis of oil-filled equipment such as transformers.

Gas chromatographRequired configuration:

• Dual detector system (TCD+FID)
• Nickel catalytic converter (CO/CO₂ conversion)
• Minimum detection sensitivity must meet the requirements of Table 3 (such as H₂≤2μL/L)

Degassing deviceOptional:

• Constant temperature oscillator (275±5 times/min)
• Vacuum degassing device (efficiency ≥ 90%)
• Automatic headspace sampler (with pressure regulation)

Sample collection

Fully sealed sampling according to GB/T 7597. Transportation must be protected from light and shock. It is recommended to use a 100mL gas-tight syringe (5.4)

Selection of degassing method

Chromatographic analysis conditions

Recommended process:

1. PLOT/Q column for separation of hydrocarbon gases (30m×0.53mm)
2. 5A molecular sieve column for separation of H₂/O₂/N₂
3. Carrier gas flow rate 12mL/min (N₂ or Ar)

Headspace method calculation formula

Gas concentration in oil X_i = 0.929×(P/101.3)×C_is×(Ā_i/Ā_is)×(K_i+V_g'/V_l')

Wherein, the value of K_i can be found in Table 5 (e.g., K_i of C₂H₂=1.02)

Precision control

• Repeatability: when the concentration is >10μL/L, the difference is <10% of the mean value
• Reproducibility: between-laboratory deviation is <15%

Quality control measures

• Verify the recovery rate with standard oil samples every month (Appendix B)
• The secondary equilibrium method is used for unknown oil types (Appendix F)
• Acetone detection requires a DB-WAX capillary column (Appendix G)

Equipment Selection Guide

Preferred choice:

• Chromatograph with automatic valve switching (Table 1 Process 3)
• Vacuum device with degassing efficiency ≥ 95%
• Glass syringe calibrated by gravimetric method