Product Core Brief
- Model: UR8NH
- Brand: GE (Multilin / GE Vernova)
- Series: UR Universal Relay Modular I/O Platform
- Core Function: Digitize eight isolated CT secondary current signals and feed processed values to UR series relay CPUs over internal backplane
- Product Type: Horizontal slot rack-mounted analog current acquisition PCB
- Key Specs: 8 CT input channels | 2500 V reinforced field-to-backplane isolation | 16-bit ADC resolution ⚠️ EOL — limited stock remaining
Product Introduction
GE accepts raw 1 A or 5 A CT secondary signals, filters grid noise, and converts analog readings to digital frames for host UR protection CPUs. It includes automatic CT shorting logic during live module removal. This unit differs from voltage-focused UR8LV by omitting VT terminals and adding saturation detection algorithms. It completes a full 8-channel scan in 0.8 ms and maintains 0.2 % full-scale measurement accuracy across -40 °C to +70 °C cabinet ranges.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Supported CT secondary ratings | Software selectable 1 A / 5 A AC |
| Total isolated CT input count | 8 independent field channels |
| Field-to-backplane isolation rating | 2500 V AC reinforced galvanic separation |
| Analog conversion resolution | 16-bit per-channel ADC sampling |
| Full channel scan cycle | 0.8 ms across all eight CT loops |
| Auxiliary power source | UR chassis backplane 24 V DC SELV |
| Maximum continuous power consumption | 7.2 W |
| Built-in diagnostic functions | Open CT, CT saturation, polarity reversal, overrange detection |
| Hot-swap capability | Yes; auto-shorts CT terminals during insertion/removal |
| Operating cabinet temperature | -40 °C to +70 °C |
| Storage temperature range | -40 °C to +85 °C |
| Mechanical form factor | Standard single-width UR chassis horizontal slot |
| Net unit weight | 0.90 kg |
| Compliance standards | IEC 61003-0, IEC 61000-6-2, UL 61010, CE certified |
Quality Control Process Process (Engineer’s Perspective)
- Incoming Verification: Cross-reference serial numbers against GE Multilin UR spare asset database to flag counterfeit hardware. Inspect front CT terminal blocks and backplane gold edge pins with a 10x magnifier for oxidation or bent contacts; log serial numbers for substation traceability.
- Live Functional Test: Seat the unit on a UR test rack paired with a UR9HH CPU and variable AC current simulators. Inject full 0–5 A CT signal ranges, run continuous 26-hour load testing while logging cabinet temperature swings and ADC reading deviation.
- Electrical Parameter Test: Use a 500 V Megger to measure insulation resistance between CT high-potential terminals and chassis ground; pass threshold set at >10 MΩ. Verify PE protective ground loop resistance below 0.5 Ω with a Fluke 115 multimeter.
- Firmware Verification: Record onboard signal processing firmware revision printed on PCB silkscreen. Photograph backplane bus termination jumper positions for field commissioning reference.
- Final QC & Packaging: Wipe the unit plastic housing with anti-static microfiber cloth, cap all CT terminal blocks with plastic dust covers. Seal inside a shielding ESD bag, attach a QC Passed label stamped with full test completion date.
Replacement Pitfall Guide
❗ Firmware Mismatch: firmware v2.4 drops backward compatibility with UR9HH CPUs running v7.0 or older build code. Match exact firmware builds before rack power-up, or all CT readings lock at zero indefinitely. ❗ DIP Switch / Jumper Misconfiguration: Factory default backplane bus termination resistor is disabled. Most multi-module substation racks require the resistor enabled on the last I/O card in the slot chain; missed settings create cyclic Modbus packet loss under peak feeder load. ❗ Terminal / Cable Incompatibility: This unit uses 2.5 mm spring CT terminals, unlike high-power URSHA 4 mm blocks. Undersized wire strands create loose CT wiring and intermittent current dropout; always short CT terminals before disconnecting field wiring per GE service manuals. ❗ Power Supply Mismatch: Full 8-channel CT measurement load draws 7.2 W peak backplane power. Calculate rack power budget with 20 % overhead; undersized UR chassis power supplies trigger low-voltage lockout and missing metering values. ❗ ESD Damage: Dry cabinet environments above 40 % relative static risk degrade internal ADC chips on the unit. Use an anti-static mat and grounded wrist strap when handling exposed PCB edge connectors and CT terminal pins. Keep these in mind and you’ll cut 90% of rework time.
Compatibility Matrix & Benchmarks
Compatibility Matrix
- UR8LV → : Needs Adaptation — UR8LV accepts VT voltage signals, terminal pin layout differs for CT wiring
- UR9HH Protection CPU → : Direct — identical backplane communication, no rack slot modification required
- URRHH Power Supply → : Direct — shares standard UR chassis backplane power rails, no voltage adaptation needed
- V7768-312000 VME SBC → : Incompatible — separate VME64 backplane architecture, no shared signal mapping
