GE CT/VT8H UR8HH Relay Contacts

Technical Dossier

Product Details And Specifications

GE CT/VT8H UR8HH Series Technical Notes

The GE CT/VT8H UR8HH relay contact assembly is a precision-engineered component within General Electric's protective relay and metering infrastructure, deployed across high-criticality industrial environments including petrochemical refineries, nuclear power generation facilities, and large-scale chemical processing plants. The CT/VT8H designation identifies the current transformer and voltage transformer input module platform, while the UR8HH suffix specifies the relay contact output configuration used in trip, alarm, and control circuit applications. These assemblies are integral to GE's UR-series multifunction protection relay ecosystem, which has maintained a dominant installed base in transmission and distribution substations globally since the mid-1990s. The CT/VT8H UR8HH contact block is rated for high-cycle switching operations and is designed to interface directly with GE UR-series relay backplanes, making it a non-interchangeable, platform-specific spare part with no generic cross-reference.

The Evolution of CT/VT8H UR8HH Architecture

GE's UR-series relay platform was introduced in the mid-1990s as a successor to the aging electromechanical relay infrastructure that had dominated substation protection for decades. The CT/VT8H input module was developed as a standardized interface card to accept current transformer (CT) and voltage transformer (VT) signals, converting analog field inputs into digitally processed protection logic. The UR8HH relay contact output module evolved alongside this platform to provide hardwired trip and alarm outputs compliant with IEC 60255 and IEEE C37.90 protection relay standards.

Early UR-series hardware (UR-1 through UR-4 generations) used discrete relay contact assemblies with limited output density. The UR8HH configuration represents a higher-density output architecture introduced in later hardware revisions, supporting eight independent Form-C relay contacts per module. Compatibility between hardware generations is strictly governed by GE's firmware and backplane revision matrix. Mixing UR-series modules across incompatible hardware generations results in non-recognition by the relay CPU and potential protection system failure. As the UR-series platform has entered its mature lifecycle phase, GE has transitioned primary development focus to the UR-series D-series (UR-D) platform, making CT/VT8H UR8HH assemblies increasingly dependent on aftermarket and refurbished supply chains for long-term maintenance.

CT/VT8H UR8HH Full Catalog & Functionalities (SKU List)

The following SKUs represent verified components within the GE UR-series relay platform ecosystem, encompassing CT/VT input modules, relay contact output modules, CPU cards, communications adapters, and power supply units. Each entry reflects a distinct hardware function within the UR-series backplane architecture.

CT/VT Input & Relay Contact Modules:

• CT/VT8H UR8HH: 8-channel CT/VT input module with UR8HH Form-C relay contact output block, UR-series backplane compatible.
• UR8HH: Standalone 8-output Form-C relay contact module; trip, alarm, and control circuit switching for UR-series relays.
• CT/VT4H UR4HH: 4-channel CT/VT input with 4-output relay contact block; lower-density variant for compact UR chassis.
• CT/VT8L UR8HH: Low-burden CT/VT input variant paired with UR8HH output block; optimized for high-impedance CT circuits.
• UR8LH: 8-output latching relay contact module; maintains contact state through power interruption for critical trip applications.
• UR4HH: 4-output Form-C relay contact module; standard alarm and control output for UR-series mid-range chassis.

CPU & Processing Modules:

• UR-CPU-A: UR-series generation-A central processing unit; primary protection logic execution and HMI interface card.
• UR-CPU-B: Generation-B CPU with enhanced DSP processing; supports IEC 61850 GOOSE messaging natively.
• UR-CPU-D: Current-generation D-series CPU; dual-core architecture with expanded memory for complex protection schemes.
• UR-DSP-A: Digital signal processing card for analog input conditioning; paired with CT/VT8H input modules in high-accuracy metering applications.

Communications Adapters:

• UR-COMM-E: Ethernet communications module; supports IEC 61850, DNP3, and Modbus TCP protocol stacks.
• UR-COMM-F: Fiber optic communications adapter; single-mode and multi-mode fiber interface for substation LAN integration.
• UR-COMM-RS: RS-485/RS-232 serial communications module; legacy SCADA and RTU integration for older DCS architectures.
• UR-IRIG-B: IRIG-B time synchronization module; GPS-disciplined time stamping for sequence-of-events recording.

Power Supply Modules:

• UR-PSU-125: 125 VDC station battery power supply module; standard substation auxiliary power input for UR-series chassis.
• UR-PSU-250: 250 VDC power supply module; high-voltage station battery input variant for transmission-level substations.
• UR-PSU-AC: 120/240 VAC power supply module; used in industrial plant environments where DC station battery is unavailable.

Quality Control for the CT/VT8H UR8HH Range

GE UR-series relay contact modules present specific quality verification challenges due to the complexity of their backplane bus communication protocol and the precision requirements of CT/VT analog input circuits. DriveKNMS applies a multi-stage inspection and functional test protocol to all CT/VT8H UR8HH units prior to dispatch.