Abstract
In recent years, as environmental protection requirements have expanded, SF6/N2 mixed gases have been selected as an insulating medium for high-voltage equipment such as GIL (gas insulated transmission line) without undertaking breaking tasks, which is superior in terms of insulation, economy and environmental protection. The development of streamers and the two-dimensional distribution of positive and negative ions over time in an SF6/N2 mixed gas system are shown in this research. The SF6/N2 mixed gas is adopted as the research object, and the discharge model for a needle-plate electrode under mixed gas conditions is built. COMSOL Multiphysics is used to develop a fluid dynamics model for the SF6/N2 mixed gas discharge in a non-uniform field. The spatio-temporal evolution processes for the electron, positive ion and negative ion densities and the electric field strength during discharge are obtained through numerical simulations. At the same time, the influence of the voltage amplitude and mixed gas ratio on the development process of streamers is studied. The presented simulation results can provide a certain microscopic interpretation for the needle-plate discharge defects that appear in power equipment using SF6/N2 mixed gas.
Highlights
The insulating media that are commonly used in power equipment include gaseous media, liquid media, solid media and composite materials, of which, gas is the most commonly used
SF6 gas is widely used in high-voltage gas insulated metal-enclosed pipe lines (GIL) and circuit breakers due to its excellent insulation and arc extinguishing properties
The SF6 gas is electronegative, so a large number of the free electrons are attached to the molecules in the arc gap to generate negative ions
Summary
The insulating media that are commonly used in power equipment include gaseous media, liquid media, solid media and composite materials, of which, gas is the most commonly used. The movement of negative ions is much slower than that of the free electrons As a result, these negative ions can combine with positive ions to form neutral molecules and atoms, which greatly accelerates the recovery of the arc gap medium strength when the current crosses the zero point.. SF6 gas has superior insulation and arc extinguishing performance, it has many associated problems.10,11 These include: (1) a strong greenhouse effect; (2) a high liquefaction temperature; (3) a sensitivity to inhomogeneities in the electric field; and (4) its decomposition when exposed to arcing. The streamer discharge development process SF6/N2 mixed gases at different mixing ratios is studied using numerical simulations. An electric field model for a needle-plate electrode under for SF6/N2 mixed gases is established.. The simulation results provide a reference for the design and manufacture of power equipment using SF6/N2 mixed gases
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