What are practical breakdown process in composite dielectrics?
A Breakdown in Composite Dielectrics generally consists of a large number of layers arranged one over the other. This is called “the layered construction” and is widely used in cables, capacitors and transformers: Three properties of composite dielectrics which are important to their performance are given below.
What is composite dielectric?
Composite dielectrics represent, in general, a heterogeneous system of multiconstituent materials. This host-inclusion system could be formed by a combination (or a mixture) of dielectric-dielectric, dielectric-conductor, and/or dielectric-semiconductor phases.
What is Dielectric breakdown?
Dielectric breakdown is the failure of an insulating material to prevent the flow of current under an applied electrical stress. The breakdown voltage is the voltage at which the failure occurs, and the material is no longer electrically insulating.
What is tracking and treeing?
Tracking is the formation of a permanent conducting path across the surface of an insulation. The spreading of spark channels during tracking in the form of the branches of tree is called treeing. With organic insulating materials such as paper and Bakelite, the dielectric carborizes at the sparking regions.
What is Townsend theory?
Townsend theory and Streamer theory are the present two types of theories which explain the mechanism of breakdown under different conditions as pressure, temperature, electrode field configuration, nature of electrode surfaces and availability of initial conducting particles.
What are the properties of composite dielectric?
The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction.
How does dielectric breakdown occur?
Dielectric breakdown occurs when electrical potential across a material exceeds the dielectric strength of the material, resulting in partial ionization. If breakdown occurs in a gas, the ionization sharply reduces the electrical insulation properties of the gas, resulting in a spark or arc.
What is intrinsic breakdown?
Intrinsic breakdown depends upon the presence of free electrons which are capable of migration through the lattice of the dielectric. When an electric field is applied, electrons gain energy from the electric field and cross the forbidden energy gap from the valence band to the conduction band.
What is cable tracking?
Tracking is defined as a process that produces localised irreversible deterioration on the surface of an insulator, resulting in the loss of the insulating function by the formation of a conductive path on the surface of the insulator.