Difference between revisions of "Insulators under a high voltage"
Line 9: | Line 9: | ||
;Avalanche formation | ;Avalanche formation | ||
− | Physically is formulated using Townsend's primary ionization coefficient (<math> alpha </math>), a relationship is built combining the number of moving electrons (n) over a distance (dx) to produce a new free electrons (dn): | + | Physically is formulated using Townsend's primary ionization coefficient (<math> \alpha </math>), a relationship is built combining the number of moving electrons (n) over a distance (dx) to produce a new free electrons (dn): |
<math> dn = n .\alpha. dx </math> | <math> dn = n .\alpha. dx </math> |
Revision as of 15:03, 2 November 2010
Introduction
Air is one of insulators that prevent charge exchange between two charged conductors. Parallel plates is an example where the air is insulating the negatively charged plate from he positively charged one. Nevertheless, air does keep this properties when the voltage difference between the plates causes air ionization. the process will produce free electrons accelerates toward the positive plate.Enough number of these electrons will make the air a conductor and sparking is observed on the plates.
Stages of Sparking
Sparking does not happen suddenly, but it microscopically has stages defined as the following:
- Avalanche formation
Physically is formulated using Townsend's primary ionization coefficient (
), a relationship is built combining the number of moving electrons (n) over a distance (dx) to produce a new free electrons (dn):
Solving the equation will give the number of the free electrons produced is calculated as :
References
Dr JP Holtzhausen, Dr WL VoslooHigh "Voltage Engineering Practice and Theory" (online drift copy)