Westinghouse Type HZM Distance Relay Manual

This document provides installation, operation, and maintenance instructions for the Westinghouse Type HZM distance relay, a three-unit high-speed relay used for phase fault protection on transmission systems. It details the relay's construction, including impedance units, offset transformers, a synchronous timer, and a directional unit, and explains how its adjustable impedance characteristics can be set to prevent tripping on synchronizing surges and heavy load conditions.