Description
Key Technical Specifications
- Product Model: UR8HH (UR-8HH)
- Manufacturer: GE Multilin
- Product Category: CT/VT Analog Input Module
- Analog Inputs: 8 Channels (Current/Voltage)
- Measurement Accuracy: ±0.1% of Full Scale
- Operating Voltage: 18.5 to 36 VDC
- Ambient Temperature: 0°C to 60°C
- Humidity: 5% to 95% Non-condensing
- Data Capacity: 16 MB
- Physical Weight: 0.29 kg (Module only)
- Product Certification: UL Listed, IEC 60255
- Mounting: Control Room / Relay Chassis Slot
Product Introduction
In substation protection, garbage in means garbage out, and the UR8HH is designed to ensure that never happens. This module serves as the precision analog front-end for GE Multilin UR relays, digitizing signals from current and voltage transformers with ±0.1% accuracy. Whether you’re running differential protection on a power transformer or distance protection on a transmission line, the UR8HH provides the clean, reliable data the protection algorithms depend on to make correct decisions in milliseconds.
I’ve seen too many protection misoperations traced back to noisy or inaccurate analog inputs, which is why I trust this module. The UR8HH includes built-in signal conditioning and filtering that rejects common-mode noise and harmonics that can fool less sophisticated designs. It also supports automatic CT ratio matching and phase shift compensation, which simplifies configuration and reduces the chance of human error during commissioning. Just remember: this is a precision instrument, not a rugged field device. Keep it in a climate-controlled relay room, and it will serve you faithfully for decades.
Quality SOP & Tech Pitfalls
The Lab Report:
We don’t just plug these in and hope. Every UR8HH gets a visual inspection for cracked solder joints, corroded connectors, or damaged backplane pins. We mount it in a live UR test chassis, apply 24V DC, and inject precision test signals to verify accuracy across all 8 channels. We also check the internal self-diagnostics and confirm the module reports correct health status to the relay CPU. Finally, it’s sealed in anti-static packaging with desiccant.
The Engineer’s Warning:
Here is where people get burned: Do not ignore CT polarity. The UR8HH can auto-compensate for phase shift, but it cannot fix reversed CT polarity. I’ve seen a differential relay fail to operate during a through-fault because someone wired one CT backwards and assumed the module would “figure it out.” It won’t. Always verify polarity with primary injection or at least a thorough secondary test. Also, photograph the jumper settings before pulling the old module; some revisions have hardware address jumpers that must match.
Installation & Configuration Guide
- Pre-Installation Safety: ⚠️ SHORT CT SECONDARIES FIRST. This module connects to live CT circuits. You must short-circuit the CT secondaries at the terminal block before disconnecting any wires to prevent dangerous open-circuit voltages. Take a photo of the existing wiring and jumper settings. Do not skip this.
- Removal: Label all CT and VT wires. Release the module retention mechanism. Pull the straight back; do not wiggle or force it, as the backplane connectors are precision-machined.
- Installation: MATCH ALL JUMPER SETTINGS. This prevents 90% of startup failures. Slide the new into the exact same slot, ensuring full backplane engagement. Re-terminate wires to the same terminals, verifying CT polarity and phase rotation.
- Power-On & Testing: Restore control power. Check the relay front panel or software for module recognition and fault codes. Verify all 8 analog channels read correct values in the relay’s metering menu. Perform a secondary injection test to confirm protection logic operates correctly.
GE UR8HH
Compatible Replacement Models
| Model | Compatibility Tier | Notes |
|---|---|---|
| ✅ Drop-in Replacement | Exact hardware/firmware match. Verify 8HH order code. | |
| UR-8HH | ✅ Drop-in Replacement | Same module, alternate part number formatting. |
| UR8LH | ⚠️ Software Compatible | Similar function, different channel count or accuracy. Requires relay reconfiguration. Allow 1 hour. |
| UR6EH | ❌ Hardware Mod Required | Digital I/O module, not analog. Not a replacement. |
Frequently Asked Questions (FAQ)
Can I hot-swap this module while the relay is energized?
No. The does not support hot-swapping. Removing it while the relay is powered can cause communication errors on the backplane and potentially trigger false protection operations. Schedule a maintenance window and short CT secondaries first.
What does the “8HH” order code mean?
The “8HH” specifically identifies this as an 8-channel CT/VT analog input module with ±0.1% accuracy. Other UR analog modules have different codes (like 8LH, 9AH, etc.) that indicate different channel counts, accuracy classes, or input types. Always match the exact code.
Why is my relay showing CT saturation warnings?
Check your CT sizing and burden. The has a fixed input range; if your CT is undersized or the wiring burden is too high, the module will see saturation during faults. Verify your CT ratio and burden calculations match the relay settings. Also check for open circuits or high-resistance connections.
Can I use this module with non-UR series relays?
No. The is designed exclusively for the GE Multilin UR series Universal Relay platform. It uses a proprietary backplane interface and communication protocol that is not compatible with other GE relay families or third-party protection systems.
What is the maximum CT burden this module can handle?
The has a very low input burden, typically less than 0.1 VA per channel at rated current. This allows you to use smaller CTs or longer wiring runs without saturation. Check the module datasheet for exact burden curves at different current levels.
Does this module support harmonic measurement?
Yes. The samples at high speed and can provide harmonic content up to the 64th order for power quality analysis. This is useful for detecting transformer inrush, capacitor switching transients, or nonlinear loads. Verify your relay firmware supports harmonic reporting.
