I have not been following this topic closely but some contributors have missed the point that PRIMARY Circuits are subject to high voltage transients and SECONDARY circuits are subject only to continuous stress.
This is why 8mm Reinforced is reasonable (and necessary) in a primary circuit whereas only a couple of mm's may be all that is required in a secondary circuit. Insulation has a limited life - life testing on high voltage pulse transformers will show that - and whereas constant stress will (eventually) cause breakdown transients will also. This is analogous to the relationship of Failure Rate to constant stress and also to Switching Stress. (Note that light bulbs will give much longer life with not switched but left on permanently. ALSO - if a high (transient) voltage causes an electrical breakdown it is quite likely that local ionization will occur and permit the arc to be maintained by a much lower voltage (like the normal applied mains voltage). Hence Primary insulation >>Secondary Insulation. Best regards Gregg PLEASE NOTE: We are currently experiencing serious problems with our service provider PLEASE reply only to gr...@test4safety.com and ignore any reference to pgtv.net, Thank you. Basically, I start with 1Mv/meter STP and work down from there. Therefore, 1mm means 1Kv. Now, throw in a x2 safety factor and you get 2mm spacing. Now increase to 1.5Kv and you end up with 2.5mm? Well, okay. Surface contamination sets in over time? Well, okay again. Obviously, I've been doing some extreme fudging, but it ends up darn close most of the time. list"
