Numerical simulation of partial discharge current pulse: Comparison between SF6, Fluoronitrile - CO2 mixture and Fluoroketone - CO2 mixture

Fluoronitrile (FN) - CO
₂
, Fluroroketone (FK) - CO
₂
mixtures present interesting properties such as: high dielectric strength, non-flammability, and low Global Warming Potential. Thus, these mixtures could be good candidates to replace SF
₆
in high voltage equipment, in particular in Gas Insulated Switchgear (GIS). However, all developed GIS monitoring systems, in particular partial discharge (PD) measurement, are specified for equipment filled with SF
₆
. To verify the applicability of existing systems for new gases, especially in DC condition, fundamental understanding of PD phenomena is essential. 2D axis symmetric simulation was thus performed for SF
₆
, FN-CO
₂
5% and FK-CO
₂
5% in negative DC polarity at room temperature and at SF6 equivalent dielectric strength to investigate the influence of gas composition to the PD pulse waveform. The swarm parameters of different gases are summarized and used in the simulation. The first simulated PD current showed the highest amplitude and the subsequence pulses showed amplitudes much smaller. The rise time for the first PD pulse current is 0.25ns, 0.37ns and 0.54ns for SF
₆
, FN-CO
₂
5% and FK-CO
₂
5%, respectively. The different rise time of PD current pulse might lead to a difference in term of performance between different PD measurement systems, especially the UHF system which is based on very high frequency component of PD pulse.