A detection system to detect disconnection of a powered device from a link of a power over Ethernet system is disclosed. The detection system can include closed-loop control configured to supply a predetermined test current to an electrically conductive path that includes at least a portion of the link via which the powered device is connectable for receiving power. A detector is configured to monitor the closed-loop control, the loop detector providing a disconnect signal if the closed-loop control is outside of expected operating parameters, thereby indicating that the powered device has been disconnected from the link.