UR8NH is a CT/VT signal acquisition module matching GE Multilin UR universal relay series. Developed for power protection and Mark VIe control systems of turbine units, it serves as a CT/VT signal acquisition controller assembly responsible for analog signal collection, preconditioning and backplane data forwarding of current and voltage signals from instrument transformers.

Compatible with racks of the full range of UR universal protection devices, it allows simultaneous connection of multiple sets of 1A/5A current transformer and voltage transformer circuits. It converts primary-side electrical quantities into digital sampling data recognizable by the main unit, and integrates on-line diagnostic logic for circuit wire breakage, overcurrent and overvoltage.

Model Decoding of UR8NH

Breakdown of the full model code, with each character corresponding to a defined hardware function: UR: Universal Relay, unified series prefix for GE Multilin universal relay auxiliary modules, compatible with racks of all UR-series protection mainframes 8: Channel quantity identifier, meaning the module is equipped with 8 independent CT/VT acquisition channels, each channel matching one set of current plus voltage transformer circuits N: Hardware isolation grade code, representing an enhanced electromagnetic isolation architecture with EMC immunity meeting standards for Class 2 power substations H: Hot-swap function marker, indicating the module supports live plug-and-play within the rack; identical-spec modules without the "H" suffix do not feature hot-swap capability

Product Features

Electrical Acquisition Performance

1. CT inputs support both 1 A and 5 A rated secondary currents; the channels withstand up to 20 times short-term overload current without burnout under fault conditions.
2. VT voltage acquisition range covers 0–120 V AC, suitable for secondary sampling of medium and low-voltage bus potential transformers (PT).
3. Sampling accuracy reaches Class 0.2, satisfying both metering-grade and protection-grade data output requirements; it synchronously transmits RMS values, harmonic components and phase angle data.
4. Built-in customizable broken-circuit detection thresholds; maintenance staff can configure the CT open-circuit alarm trigger current via software.

Hardware Structure Features

1. Rack-mounted card design for single-slot installation in standard UR racks. Partitioned front terminals for C/T/V wiring clearly separate earthing, current and voltage terminals to prevent miswiring.
2. High-density gold-finger backplane bus interface; each module forwards up to 1,000 sampling data packets per second, with synchronous sampling time difference below 1 microsecond across multiple modules.
3. Full-metal shielding enclosure with bottom heat-conduction passive cooling; no internal cooling fans to eliminate consumable failure points.
4. Independent fuse protection per channel: a short circuit on one circuit only blows its dedicated channel fuse, leaving the other seven acquisition channels fully operational.

Communication & Security Features

1. Natively interfaced with UR mainframes via backplane; forwards data to SCADA systems over IEC 61850, Modbus TCP and DNP3 protocols simultaneously.
2. Built-in hardware self-diagnosis including power-on self-test and periodic runtime self-checks; fault codes are displayed both on front-panel LEDs and the software interface.
3. Compliant with NERC CIP power grid cybersecurity standards; encrypted verification is applied to transmitted acquisition data to avoid tampering.
4. Synchronized sampling for Sequence of Events (SOE) logging; fault sampling data carries high-precision timestamps for post-fault oscillography analysis.

Application Industries

1. Thermal / Gas Turbine Generating Units: Matched with Mark VIe turbine control systems to collect CT and PT signals at generator terminals for unit protection and load monitoring.
2. Substation Power Transmission & Distribution Systems: Bay protection in 35 kV, 110 kV and 220 kV substations, signal acquisition auxiliary for line, capacitor bank and transformer protection devices.
3. New Energy Power Stations: Instrument transformer signal collection for centralized wind and photovoltaic booster stations, supporting grid-connected protection equipment.
4. Petrochemical On-Site Power Plants: Comprehensive protection sampling for plant high-voltage buses and large high-voltage motors, deployed inside control cabinets for explosion-proof plant areas.
5. Rail Transit Traction Substations: Real-time current and voltage collection for traction power supply systems, overcurrent and short-circuit fault monitoring.

6. Metallurgical & Steel Mill Private Power Grids: Pre-processing acquisition of electrical quantities for high-voltage supply circuits serving rolling mills and steelmaking furnaces.

Product Comparison

UR8NH vs UR8FH

UR8NH supports hot swapping and adopts enhanced electromagnetic isolation, suited for harsh environments such as generator units and outdoor substations with higher precision for per-channel broken-circuit diagnosis. UR8FH does not feature hot-swap capability and only comes with basic isolation design. It is merely for conventional indoor power distribution rooms at a lower procurement cost, without diagnostic optimization for heavy-load operating conditions.

UR8NH vs UR16NH

UR8NH is an 8-channel compact module occupying a single rack slot, ideal for small switchgears with fewer bay points. UR16NH is a 16-channel acquisition module requiring dual-slot mounting, designed for main transformer bays with centralized multi-circuit signal collection, and its overall power consumption is higher than UR8NH.

UR8NH vs UR-AI

UR8NH is dedicated to electrical quantity acquisition from CT/VT instrument transformers and embedded with broken-circuit protection logic. UR-AI is a universal analog input module that only accepts 4–20 mA transmitter signals and cannot be directly connected to secondary circuits of current transformers. The two models are non-interchangeable for application scenarios.

Matching Supporting Products

1. UR Series Universal Mainframes: C60, L90, D60, T35 protection relays, serving as the core for data processing and logic calculation.
2. Terminal Base Boards: TBTC, TBTA wiring terminal boards for transitioning secondary wiring of instrument transformers to UR8NH terminals.
3. Power Supply Module: UR-SHA rack power module that supplies stable power to all cards including UR8NH in the entire rack.
4. Communication Expansion Card: UR-COM Ethernet communication module for uploading acquired data to the monitoring background system.
5. Configuration Software: EnerVista UR configuration software for module parameter setup, fault diagnosis and oscillography viewing.
6. Rack Accessories: Standard 12-slot / 24-slot mounting racks of UR series, fixing clips and spare channel fuses.

FAQ

Q1 How to verify if UR8NH is compatible with existing UR protection relays before purchase?

A1 Check the firmware version of the main relay unit. All firmware V7.40 and above offer full compatibility. Units running firmware versions below V7.40 require a firmware upgrade. In addition, confirm the rack is equipped with a hot-swap power supply circuit; legacy racks do not support live module replacement.

Q2 Can UR8NH directly replace UR8FH?

A2 They share identical slot dimensions for physical installation, yet UR8FH lacks hot-swap capability and enhanced electromagnetic isolation. Live plugging/unplugging after replacement will interrupt system sampling. Direct replacement is not recommended for outdoor bays or critical generator unit bays.

Q3 The module triggers a CT broken-circuit alarm while no wire damage is found on on-site transformer circuits. What are the causes?

A3 Inspect three items: loose terminal bolts, blown channel fuses, or incorrect CT ratio parameters configured in software. Replace the channel fuse first, retighten all secondary wiring, then refresh sampling data.

Q4 How to handle drastic fluctuations of sampling values on operating UR8NH?

A4 Follow these steps sequentially:

1. Verify the shield ground wire is firmly connected to the C terminal;
2. Identify interference sources such as high-voltage switches and inverters on site, and deploy shielded cables;
3. Enable the digital filtering function in software to stabilize sampling readings.

Q5 What is the maximum quantity of UR8NH modules installable in one single rack?

A5 A standard 24-slot UR rack can hold up to 12 UR8NH modules. The remaining slots shall be reserved for communication and digital I/O expansion modules. Exceeding this limit will lead to data congestion on the backplane bus.

Q6 Do I need to specify separate UR8NH hardware versions for 1 A and 5 A CTs during procurement?

A6 No separate hardware models are required. UR8NH features universal hardware support. The rated current (1 A / 5 A) is merely switched via parameter settings inside EnerVista software, and one single module works with both types of transformer circuits.

Recommended Models of the Same Brand

UR8NH: CT/VT Acquisition Controller Module UR8FH: Basic CT/VT Acquisition Module UR16NH: 16-Channel Instrument Transformer Acquisition Module UR-SHA: UR Series Rack Power Supply Module