by Alexandre Chaillet
Between each pole of an electrical product standards give insulation distances. This is mainly called “Creepage and clearance”. This will avoid to have short circuits or breakdown (sparks) in case of overvoltage and thus for all the life of the product.
These distances are influenced by altitude, moisture, pollution and some other parameters.
If designers does not respect these distances, the worst case could happen: they think it is working because when they powered their system everything is ok. It is ok now but for how many time ?
The video shows a special phenomena called “partial discharge”. This could happen when homogeneity of the plastic molding of a connector for example is not properly done and in this case when there is too much moisture (that’s easier to realize :) ).
Between plastic and air or in his case air and moisture, there is a modification a permittivity that under overvoltage (due to thunder for example), a franc spark will not appear but partial discharges just where are small drops. Each small spark will carbonized a little bit the plastic. And spark after spark, it will create a “carbon path” between 2 poles that is comparable to a copper wire (carbon is a conductor for electricity).
And even if the distances was correct between 2 poles, a big sparks occurs that could bring a lot of trouble in your full system !!
The video shows is at very fast but this phenomena could happen in several weeks or months.
You think it is working but it is not !
Respect creepage and clearance standards and avoid low cost material :)
