There is voltage reduction due to line impedance in 250 meter cable for PoE. What should I do?

Answer:

Make sure your POE switch is connected to a 57V power supply so the powered device can get the full 25W after the 250M voltage reduction.
PoE output power table:

(Base on CAT-5e cable)

It is suggested to pre-test the function before deployment. The maximum available transmission distance of PoE depends on the negotiation result of PD and PSE. Some PDs using EtherWAN PoE/PSE switches may only support a standard distance of 100 meters. Contact EtherWAN if assistanee is needed.