Description
Hard-Numbers: Technical Specifications
- CT Channel Count: 8 isolated current inputs (expandable to 24 CTs with 3 modules)
- VT Channel Count: 0 (CT-only; pair with UR-8LV/8LH for voltage inputs)
- CT Nominal Rating: Software selectable 1A / 5A secondary
- Operating Temperature: -40°C to +70°C ambient cabinet rating
- Isolation Rating: 2500Vrms reinforced isolation, field to backplane
- Maximum Power Draw: 7.2 Watts, backplane supplied
- Sample Resolution: 16-bit high-resolution ADC per CT channel
- Hot-Swap Capability: Live insert/remove with automatic CT shorting logic
- Measurement Accuracy: 0.2% full scale (protection + metering grade)
- Diagnostic Coverage: CT saturation, open CT, phase imbalance, polarity error, overrange
The Real-World Problem It Solves
Standard 4CT modules (UR-8LM/8LV) lack sufficient channels for multi-feeders or transformer banks. Dedicated 8CT solutions with diagnostics were previously unavailable, forcing costly system upgrades.
Where you’ll typically find it:
- Transmission substations (230kV–500kV) with multiple feeders and bus sections
- Large industrial plants (steel, oil/gas) with 6–8 medium-voltage motors
- Generator switchyards requiring separate phase + neutral current monitoring
- Distribution hubs with 3+ parallel feeders needing individual CT supervision
Bottom line: It’s the high-density 8CT solution—enhanced diagnostics, metering accuracy, no VT overhead, perfect for current-heavy applications.
Hardware Architecture & Under-the-Hood Logic
UR-8NH uses a dedicated 8-channel analog front-end with shared DSP, galvanically isolated from the UR backplane. Same slot footprint as 4CT modules, optimized for current density.
- 8 CT secondary signals enter independent surge suppression and current-limiting circuits.
- Precision burden resistors and low-noise amplifiers condition signals for protection/metering.
- Eight 16-bit ADCs convert analog waveforms to digital samples simultaneously.
- Onboard DSP runs real-time diagnostics: flags saturation, open circuits, phase imbalance.
- Time-aligned, fault-checked data transfers across isolated backplane to host CPU.
- Factory calibration stored in non-volatile memory; retains settings during hot-swap.
Field Service Pitfalls: What Rookies Get Wrong
Confusing UR-8NH with 4CT Modules During ReplacementTechs mix up 8CT (NH) and 4CT (LM/LV) modules. NH has double the channels, different wiring, and higher power draw—causing miswiring and backplane overload.
- Field Rule: Verify part number; NH labeled “8CT” on edge connector; 4CT modules have no such marking.
Forgetting Voltage Inputs (NH = CT-Only)New techs deploy NH alone expecting voltage monitoring. It has zero VT channels—protection functions (e.g., distance) fail without voltage.
- Quick Fix: Pair UR-8NH with one UR-8LV/8LH (4CT/4VT) for complete 3-phase voltage + 12CT current coverage.
Overloading CT Bushing CapacityTechs wire 8 CTs into standard terminal blocks rated for 4–6 circuits. Overheating and loose connections occur under vibration.
- Field Rule: Use high-density 12-terminal blocks; torque CT wires to 1.2 N·m; inspect annually for thermal discoloration.
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
