Your Switch is not doing exactly nothing...is it a PoE model, isn't?
So maybe, just a guess here (due to fact that PSED acronym resembles something like PSE Deamon in my head), the PSED Task would be the deamon which is supervising the PSE PoE status (issue a display poe pse command to see PoE PSE health info)...so...it would totally make sense to see it draining some (<10%) of the total CPU capacity even if the Switch is not currently doing switching.
Just curious: which specific PoE Firmware version is your JG962A Switch running now? 145 or what?