Gas insulation is important for transmission lines, outdoor insulators and Gas-insulated- Substations (GIS). Understanding the breakdown mechanisms and behaviour of insulation materials is key to the optimum design of insulation systems. The speed distribution function of electrons in a gas containing electrons, ions and atoms is controlled by the electric field strength, E, and can be expressed as fr(E, v) . It satisfies the relationship ſº fv (E, v) dv =1.
Gas insulation is important for transmission lines, outdoor insulators and Gas-insulated- Substations (GIS). Understanding the breakdown mechanisms and behaviour of insulation materials is key to the optimum design of insulation systems. The speed distribution function of electrons in a gas containing electrons, ions and atoms is controlled by the electric field strength, E, and can be expressed as fr(E, v) . It satisfies the relationship ſº fv (E, v) dv =1.
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Gas insulation is important for transmission lines, outdoor insulators and Gas-insulated-
Substations (GIS). Understanding the breakdown mechanisms and behaviour of
insulation materials is key to the optimum design of insulation systems. The speed
distribution function of electrons in a gas containing electrons, ions and atoms is
controlled by the electric field strength, E, and can be expressed as fo (E, v). It
satisfies the relationship of (E, v) dv=1.
i)
ii)
Convert the above electron speed distribution function into an electron
energy distribution function that satisfies the relationship f(E, ɛ) dɛ =1
where & is the electron energy and ƒ(E, ɛ) the electron energy distribution
function.
The electron number density is ne and the atom number density is na in
the gas. The ionisation cross section of the atoms by electron impact is a
function of electron energy, ɛ, and can be written as σ¡ (ɛ). Similarly, the
attachment collision cross section between an electron and an atom is
a(e). For a given electron energy distribution function f₂(E, ɛ) derive,
with sufficient details, a mathematical expression for the ionisation
frequency of the atoms and another expression for the attachment rate of
electrons in a unit volume of the gas.
iii) Collisional processes other than electron impact ionisation of the atoms and
electron-atom attachment are not important. Derive the criterion, in the
form of a mathematical expression, for the onset of electron avalanche in
the gas and comment on the factors that affect the critical field strength Er
of the gas.
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