GE Multilin UR-8MH CT/VT Module

General Electric UR-8MH CT/VT Module

The General Electric UR 8MH, also cataloged as the UR 8MH CT/VT module, operates as a dedicated hardware component for transformer‑rated current and voltage scaling within the UR Series Universal Relay system. It provides 4CT/4VT channels with sensitive‑ground measurement capability and diagnostic visibility through the UR backplane.

Hardware Specifications

Backplane Bus Communication Velocity Licenses

The UR-8MH follows GE’s industrial control conventions for deterministic analog data propagation across the UR backplane. CT and VT channels are sampled and transferred through fixed‑rate internal bus cycles, ensuring stable analog delivery to protection elements. The module’s I/O density scaling supports mixed CT/VT allocation without requiring firmware flash compatibility adjustments across UR relay families. Sensitive‑ground CT channels maintain low‑level signal integrity through controlled impedance paths and channel‑to‑system isolation.

Frequently Asked Questions

Q: Can the UR-8MH be hot‑swapped in a UR chassis? A: No. UR CT/VT modules require the relay to be de‑energized before removal or insertion to maintain analog channel integrity and prevent backplane fault conditions.

Q: Does the UR-8MH require a specific CPU hardware revision? A: CT/VT modules must match the relay’s CPU generation. Older CPU cards may not accept newer CT/VT modules, resulting in hardware mismatch alarms.

Q: How are CT and VT channels assigned within the relay? A: Channels 1–4 or 5–8 can be configured for voltage inputs, with phase mapping following standard UR conventions (A/B/C/neutral). Exact wiring diagrams are provided in UR manuals.

Field Installation Guidelines

• Maintain CT polarity orientation and ensure shorting blocks are applied during installation to avoid open‑circuit CT hazards.
• VT wiring should follow phase‑segregated routing to minimize induced noise.
• Shielded cabling must be grounded at a single point to prevent circulating currents.
• Verify terminal torque using standard panel hardware values; do not overtighten CT/VT screw terminals.
• Confirm module seating by applying uniform pressure across the connector edge before energizing the relay.