Guys,
I'm going to go out on a limb here.
I was under the impression that P-P voltage was used as the maximum voltage that the system cable insulation had to withstand?
In a pure sine wave there is a simple mathematical relationship between P-P and RMS, so when you chose one the other can be directly inferred. It just so happens that everything in the power world is done based on RMS voltage not P-P.
Most cable insulation (i.e. THHN) is rated for 600V if this was a P-P value then we could not use it on ungrounded 480V RMS systems and definitely not on 600V ones. Now if you mean that the cable is tested, as opposed to rated, based on P-P you could be correct, after all a megger only puts out P-P (actually DC). But again a P-P voltage can easily be converted to RMS.
In the US the NEC says that all systems are to be referred to by their nominal RMS voltage.
