Dielectric constant vs voltage breakdown
Dielectric constant vs voltage breakdown
(OP)
Hi,
I know that higher dielectric constant (relative permittivity) yields higher capacitance. So I always assumed that the higher dielectric constant, the better insulation material it is...therefore, higher voltage breakdown.
But I just came across some references showing that voltage breakdown has inverse relationship with dielectric constant. So dielectric breakdown actually drops as the constant goes up. Could somebody explain? Thanks.
Albert
I know that higher dielectric constant (relative permittivity) yields higher capacitance. So I always assumed that the higher dielectric constant, the better insulation material it is...therefore, higher voltage breakdown.
But I just came across some references showing that voltage breakdown has inverse relationship with dielectric constant. So dielectric breakdown actually drops as the constant goes up. Could somebody explain? Thanks.
Albert






RE: Dielectric constant vs voltage breakdown
However, how far they move is proportional to how strongly the electrons are bound to the nuclei. The weaker that force, the more they move, but the more easily they can be ripped completely free. Ripping an electron free is dielectric breakdown.
RE: Dielectric constant vs voltage breakdown
Based on this, correct me if I"m wrong, I can say that a new EPDM insulated cable should have less capacitance than an aged EPDM insulated cable. Is this a legit assumption?
Thanks.
RE: Dielectric constant vs voltage breakdown
I expect that most aging processes will increase the capacitance. The exception would be some sort of "foamy" process that fluffs up the insulation, decreasing its density. You'd want to do lots of testing to see what aging does in the real world.
I see a possible complication: the effect of changing geometry on capacitance as the cable settles under its own weight. For horizontal cables, I'd expect them to squish together over time, gradually increasing the capacitance. For vertical cables, I'd expect them to splay out over time, decreasing the capacitance. Changes in a liquid environment would also have a big effect, as for buried cables. Again, you should do lots of experiments to characterize the background changes.