Power Over Ethernet Interoperability Guide

The PoE Hi-Pot Test

We discussed this in Chap. 9 too. Here we will get into more detail. As per Section 5.2.2 of the safety standard IEC 60950-1, to which the PoE standard IEEE 802.3at refers (see Fig. 10.1), we need to apply 1500 V RMS AC (50 or 60 Hz) for 60 s across the boundary that needs to be tested. This is the high-potential or hi-pot test. We are thereby testing the voltage-withstanding capability of everything that separates the following two circuits—TNV-1 (PoE/MDI side) and SELV (host side). Note that “everything” includes circuit components (like the data transformers and the high-voltage Y-caps we talked about previously), the interposing air (leading to the concept of minimum physical separations), and the PCB itself where TNV-1 ...