Isolation Requirements
Under any typical overvoltage spike, such as we may see on TNV-1/ PoE/MDI circuits, we do not want the insulation between the PoE/ MDI side and the host side to break down, because that would allow the transients to come on to the easily accessible metal surfaces. In other words, we want the interposing dielectric/insulators to be able to withstand a typical overvoltage spike (~2 kV). That is the purpose of the hi-pot test conducted in PoE and telecom in general (discussed in Chap. 9), and the reason for the first row in Fig. 10.1.
We must point out that in PoE, there are actually no specific requirements in terms of any insulators, their thicknesses, their voltage ratings, physical separations, or grounding concerns. ...

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