Field Experience of Sampling and Laboratory Analyses of C4-FN/CO2 Insulating Gas Mixture

Utilities have installed non-SF6 gas blends in gas insulated switchgear (GIS) as a step towards Net Zero. The present work attempts to investigate the stability of fluoronitrile (C4-FN, CAS No. 42532-60-5) based insulating gas blend in power asset. Field experience of sampling procedure of 4% C4-FN / 96% CO2 gas blend from gas zones in an operational 400 kV GIS substation is presented. Samples were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) and Fourier Transform - Infrared Spectroscopy (FT-IR) at three different labs. The results indicate minimal formation of decomposition by-products showing the gas blend is relatively stable within the operational range and during the period of its use in gas zones.