Key Technical Specifications

• Product Model: UR7KH
• Manufacturer: GE Multilin
• Module Type: 2-Channel Fiber Optic Transmitter
• Transmitter Technology: ELED (Edge-Emitting Light Emitting Diode)
• Wavelength: 1300 nm
• Fiber Type: Single-Mode
• Channel Count: 2 Channels (TX1/RX1, TX2/RX2)
• Form Factor: UR Series Plug-in Module
• Target Relay Platforms: GE L90, B30, G60
• Slot Configuration: Slot X (Communications)

 

Product Introduction

Line current differential relays like the GE L90 rely entirely on their communication links to make split-second trip decisions. When that fiber link goes down or degrades, you lose your primary protection scheme. The UR7KH was engineered specifically to bridge this gap, providing two independent channels of 1300nm single-mode optical transmission for long-haul fiber runs. I’ve pulled dozens of these from aging protection panels over the years, and they are workhorses for substation communication.Engineers stick with this specific module because single-mode ELEDs offer a much better distance-to-cost ratio than older multimode LED setups. Hitting that 1300nm window means you can push signals further down the fiber without needing expensive optical amplifiers. One thing to keep in mind from the field: this specific revision is notoriously sensitive to dirty fiber connectors. A single speck of dust on the TX1 port will drop your optical power budget instantly, so keep your cleaning wipes handy.

Quality SOP & Tech Pitfalls

• The Lab Report (SOP): Every UR7KH we ship goes through a strict bench test. We start with a visual inspection of the SC/LC ports for physical damage. Next, it gets racked into a live L90 test chassis to verify channel handshake and TX optical output levels. We check insulation resistance with a Fluke 1587 FC to ensure no internal shorts. Finally, it gets logged, sealed in anti-static packaging, and shipped.
• The Engineer’s Warning (Pitfalls): Never plug a single-mode ELED module into a multimode fiber patch panel without verifying the link loss. I once saw a tech spend six hours chasing a phantom relay misoperation, only to find out someone had swapped a single-mode patch cord for a multimode one during a routine outage. Also, always take a photo of the DIP switches before pulling the old module. Guessing the configuration is a great way to guarantee a callback at 2 AM.

 

Installation & Configuration Guide

1. Pre-Installation: ⚠️ Lockout/Tagout the relay. Wait a full 60 seconds for internal capacitors to discharge. Before touching anything, take a clear photo of the existing module’s DIP switches and fiber routing.
2. Removal: Label both TX and RX fibers clearly. Gently squeeze the DIN rail clip and slide the module out. Never yank the fiber cables directly.
3. Installation: Copy the DIP switch settings exactly from your photo. This step prevents 90% of startup communication failures. Slide the UR7KH into Slot X until the backplane connector seats fully, then lock the DIN clip.
4. Power-On & Testing: Restore control power. Watch the front panel LEDs for the normal boot sequence. Check the relay’s front panel or EnerVista software to verify that both Channel 1 and Channel 2 report valid optical receive levels and no synchronization errors.

Compatible Replacement Models

• ✅ Drop-in Replacement: UR7KH (Exact match. If you find a New Surplus unit with the same suffix, it requires zero configuration changes.)
• ⚠️ Software Compatible: UR7JH (2-Channel 1300nm Single-Mode LASER). This is a direct hardware upgrade. It uses a LASER instead of an ELED, which provides a higher optical power budget. Requires verifying the relay’s fiber configuration settings in the software, but no logic changes are needed.
• ❌ Hardware Mod Required: UR7AH / UR7BH (Multimode LED modules). These use completely different wavelengths and fiber types. Do not attempt to use these unless you are replacing the entire fiber plant back to multimode.

 

Frequently Asked Questions (FAQ)

• Can I hot-swap this module while the relay is energized?
  No. Pulling a communication module on a live L90 or B30 will cause an immediate loss-of-channel alarm and can block your protection scheme. Always schedule a maintenance window and de-energize the relay first.
• Will this work with standard multimode patch cables?
  No. The UR7KH is strictly a single-mode module. Using multimode fiber will cause massive signal attenuation and link failure. Verify your fiber plant is OS1 or OS2 single-mode before installing.
• Is this module still manufactured by GE?
  No, the UR7KH is obsolete. The units currently available are New Surplus or refurbished. If you need a current-production equivalent, look at the LASER-based UR7JH module.
• What if my receive optical power is hovering right at the threshold?
  Clean the fiber connectors first. I can’t stress this enough. A quick wipe with a one-click cleaner fixes marginal optical levels more often than you’d think. If it’s still borderline, your fiber run might be degrading, or you need to upgrade to the LASER version.
• Does this module support both TX/RX on a single strand?
  No, this is a dual-fiber transceiver. You need separate TX and RX strands for each of the two channels. Single-strand operation requires different optics entirely.
• What warranty do you provide on obsolete spares?
  We back every UR7KH with a 1-year warranty. If it fails under normal operating conditions, we replace it. No questions asked.