UR8MH

The UR replacement-module order-code structure identifies 8M as a sensitive-ground 4CT/4VT module with enhanced diagnostics. The horizontal replacement-module family provides the ordering context for UR-8M-H. Compatibility depends on the complete relay order code and installed hardware; protection elements, communications and output functions belong to the configured relay rather than to this input module alone.

The sensitive ground-current input is ten times more sensitive than the ground input of a standard CT/VT module, while the phase CT and phase VT inputs retain the regular module characteristics. UR current inputs support 1 A or 5 A CT secondaries through the corresponding terminals, with configured CT primary values from 1 to 50000 A. Each AC current input has an isolating transformer and an automatic shorting mechanism on module withdrawal; current inputs have no internal ground connection.

CT/VT channels are arranged in groups of four. Channels 1 and 5 correspond to phase A, 2 and 6 to phase B, and 3 and 7 to phase C; channels 4 and 8 provide ground-current IG or auxiliary-voltage VX connections according to the input group. Enhanced diagnostics can detect CT/VT hardware failure and take the host relay out of service. Match the terminal schedule, ratios and host settings, then verify phase and ground measurements during the approved protection commissioning procedure.