VARIMETER PRO RL 9877 / RN 9877 Phase Monitor Manual

This document describes the VARIMETER PRO phase monitors (models RL 9877 and RN 9877), which are measuring relays for monitoring overvoltage, undervoltage, voltage range, phase asymmetry, phase failure, and phase sequence in three-phase or single-phase AC systems. The devices feature internal power supply from all phases, selectable monitoring functions via a rotary switch, adjustable hysteresis and switching delay, and a changeover contact output, enabling preventive maintenance and safe plant monitoring.