Power Over Ethernet Interoperability Guide

Hi-Pot Testing for PoE

Figure 9.10 seems to be based on the old method of testing multioutput AC-DC silver-box power supplies. In hi-pot testing, all the output cables were physically “tied” together, and a high-voltage was applied between that clump of output cables and the metal enclosure of the power supply. The underlying philosophy was that all the paths between output and earth ground were now in parallel, and so the weakest link, whichever it was, would at some voltage level, break down and pass current. This seems to have been carried over to PoE testing without much thought. Because we now realize that connecting all the possible breakdown paths in parallel works, but only provided those paths are truly independent. If there is a “sneak” ...