Decomposition Characteristics of SF6 under Arc Discharge and the Effects of Trace H2O, O2, and PTFE Vapour on Its By-Products

Abstract

The research on decomposition characteristics of SF6 and its by-products have great significance to the operation, maintenance, condition assessment and fault diagnosis of power equipment. In this paper, the particle composition models of SF6, SF6/polytetrafluoroethylene (PTFE), SF6/PTFE/O2, SF6/PTFE/H2O, and SF6/PTFE/O2/H2O were established by using Gibbs free energy minimization method, and the effects of trace H2O and O2 impurities and PTFE vapour on SF6 by-products were studied by the models. In order to verify the correctness of the simulation results, a series of breaking experiments were carried out on a 40.5 kV SF6 circuit breaker, and a gas chromatograph was used to detect and analyse the SF6 by-products. It was found that when PTFE vapour is involved in the arc plasma, the main by-product after arc quenching is CF4, and the molar fractions of C2F6 and C3F8 are very low. When O2 is involved, the main by-products are SOF2, SO2 and SO2F2, and a small amount of CO and CO2 was also produced. When H2O is involved, the main by-products in simulation are SOF2, SO2 and HF, and a small amount of SO2, CO2, CO, SO2F2 and H2 was also produced. The experimental results are in good agreement with the above results.

Characterization of the Airflow Distribution near a Circuit Breaker’s Cu-Ag-Alloy Electrode Surface during and after Breakdown

“…A circuit breaker's breakdown process is a multi-physical field coupling process; the process studied in this work includes the distribution of the thermal airflow process through three physical fields, electromagnetic-thermal, fluid heat transfer, and fluid flow, for the model building and initial boundary conditions. The first is the electromagnetic-thermal process, where all domains of the model satisfy the current conservation equations [32][33][34].…”

“…There is currently no publicly available information or theoretical research on insulation breakdown and the recovery processes between switch contacts under multiple lightning overvoltage conditions. Furthermore, there are no technical references or solutions available for the related engineering issues, highlighting the urgent need for further research in this area [31,32].…”

SF6Decomposed Component Analysis for Partial Discharge Diagnosis in GIS: A Review

“…Limited studies have carried out to investigate the influence of some traces in SF6 decomposition under arc discharge. In [37], the effects of trace H2O and O2 impurities and polytetrafluoroethylene (PTFE) vapour on SF6 by-products were studied. Results obtained have found that the main products after arc quenching were CF4 under PTFE, SOF2, SO2 and SO2F2 when O2 is involved, and SOF2, SO2 and HF when H2O is involved.…”

Evolution of Elements on Electrode Surfaces in Gas-Insulated Systems under Electrical Heating

“…For circuit breakers, under the high temperature conditions of the breaking arc, SF 6 gas and insulating materials (CkHy) such as graphite (C), polytetrafluoroethylene (Teflon or PTEE), contact material (Cu and W), arc-extinguishing structural materials, shell materials (Al), etc., will produce chemical reactions [25], and they mainly include the following.…”