Partial Discharge Characteristics of C3F7CN Gas Mixture Using the UHF Method

Loizos Loizou, Qinghua Han, Lujia Chen, Qiang Liu, Mark Waldron, Gordon Wilson, Roberto Fernandez Bautista, Malcolm Seltzer-Grant

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Abstract

Manufacturing or assembly defects in gas-insulated equipment can introduce field enhancements that could lead to partial discharge (PD). This paper examines the PD characteristics of SF6 alternatives considered for potential application to retro-filling existing SF6-designed equipment. The PD performance of the C3F7CN/CO2 gas mixture and SF6 were characterised adopting the ultra-high frequency (UHF) method and investigated for different defect configurations, pressures, and gas mediums. Hemispherical rod-plane and plane-to-plane configurations with needle on the high-voltage (HV) and ground electrodes were used to mimic conductor and enclosure protrusion defects, respectively. The results demonstrate that with a needle length of 15 mm, the 20% C3F7CN/80% CO2 gas mixture had almost half the partial discharge inception and extinction voltages (PDIV/EV) of SF6. For less divergent fields, the 20% C3F7CN/80% CO2 gas mixture demonstrated a comparable PDIV/EV performance as SF6. The phase-resolved PD patterns of the 20% C3F7CN/80% CO2 gas mixture demonstrated a 3-stage transition phase that was not observed with SF6, which could be due to the discharge mechanism of the weakly attaching CO2 gas used within the mixture.
Original languageEnglish
Pages (from-to)7731
JournalEnergies
Volume15
Issue number20
Early online date19 Oct 2022
DOIs
Publication statusE-pub ahead of print - 19 Oct 2022

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