ABB RHEF-P is a specific communication and human-machine interface (HMI) module designation within the ABB Relion® series of protection relays. It is not a standalone relay, but a key component or feature package that constitutes part of high-end ABB digital protection relays such as the REx5xx, REF5xx, and RET6xx series. The "P" typically stands for "Panel-mounted" or "Front-mounted", indicating its design for installation on a control panel or switchgear door.
