GE Multilin UR8LH Relay Output Module – UR Series

GE Multilin UR8LH: Mixed-Contact Relay Output Module for UR-Platform Protection Systems

The UR8LH is a factory-configured relay output module engineered for the GE Multilin Universal Relay (UR) platform — a slot-based, modular protection architecture deployed across transmission substations, industrial switchgear, and generation facilities worldwide. Within a single rear-panel I/O slot, the UR8LH delivers four independent relay output contacts in a mixed configuration: two Form A (SPST-NO) and two Form C (SPDT changeover). This contact topology is not arbitrary — it reflects the practical wiring requirements of protection panels where trip coil circuits demand dedicated normally-open contacts, while alarm annunciators and SCADA digital inputs require changeover contacts to monitor both energized and de-energized states simultaneously.

The module interfaces with the UR chassis backplane via a keyed rear-panel slot connector. Contact assignments are configured entirely within the relay’s FlexLogic™ programmable logic environment, where each of the four output contacts can be independently mapped to any protection element operand, virtual output bit, or user-defined logic gate — without hardware modification. The UR8LH draws its operating power from the chassis backplane; no external auxiliary supply is required, and no jumper configuration is needed at the module level.

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Technical Parameters

Hardware Logical Analysis

The UR8LH’s internal architecture centers on four electromechanical relay elements mounted on a single PCB substrate, each driven by an isolated coil circuit that receives its switching signal from the UR chassis backplane logic bus. The separation between the coil drive circuit and the output contact circuit is maintained by a 2,000 VAC dielectric barrier — a design requirement for protection relay output modules operating in environments where contact circuits may carry 125 VDC trip bus voltage while the relay’s internal logic operates at 3.3 V or 5 V CMOS levels.

EMC Design: The module’s PCB layout incorporates ground plane segmentation to prevent high-frequency transients on the contact side from coupling into the backplane logic bus. Transient suppression components are placed at the coil drive inputs to clamp inductive kickback generated when relay coils de-energize — a critical consideration in dense I/O configurations where multiple output modules share a common backplane. The UR platform’s compliance with IEEE C37.90.2 (radiated immunity) and IEC 61000-4-4 (electrical fast transient) confirms that the UR8LH’s EMC design is validated under the high-frequency burst conditions typical of substation environments with capacitor bank switching and disconnect operations.

Contact Architecture — Form A vs. Form C: The two Form A contacts on the UR8LH are optimized for trip coil circuits. A Form A contact presents zero series resistance in the open state and a low, stable contact resistance (typically < 100 mΩ) in the closed state — characteristics that minimize voltage drop across the contact when driving 125 VDC trip coils with inrush currents of 1–3 A. The two Form C contacts provide both NO and NC terminals, enabling the UR8LH to simultaneously drive an alarm relay (via NO) and provide a healthy-state monitoring signal to a SCADA RTU (via NC) from a single contact element. This eliminates the need for auxiliary interposing relays in many panel designs.

Backplane Interface and Auto-Detection: The UR8LH communicates its module identity to the UR CPU via the chassis backplane’s module identification bus — a low-speed serial protocol that the UR firmware polls at startup and during runtime. When the firmware detects a UR8LH in a given slot, it automatically configures the FlexLogic™ output assignment table to expose four output operands for that slot. This auto-detection mechanism eliminates manual slot configuration and ensures that a replacement UR8LH is recognized without firmware re-flashing or settings file modification, provided the FlexLogic™ output assignments in the existing settings file are compatible with the physical wiring.

Thermal Management: The relay coil drive circuits generate localized heat during sustained energization. The UR8LH’s PCB thermal design routes heat through copper pours to the module housing, which acts as a passive heat spreader. The −40 °C to +85 °C operating range is validated under continuous duty conditions, covering arctic outdoor switchgear enclosures and tropical substation control rooms without derating.

System Integration Benefits

• Single-Slot Mixed Output: The 2 Form A + 2 Form C configuration within one slot reduces slot consumption in densely populated UR chassis, freeing adjacent slots for additional I/O or communication modules without expanding the relay housing.
• Direct Trip Coil Drive: Form A contacts rated to IEC 60255-23 Class III eliminate the need for interposing relays in standard 125 VDC trip circuits, reducing panel wiring complexity and potential failure points in the trip path.
• FlexLogic™ Assignment Flexibility: Each contact is independently assignable to any protection element, virtual output, or user logic gate within the UR’s FlexLogic™ environment — enabling the same physical module to serve different functional roles across relay models (C60, F60, T60, G60, etc.) without hardware changes.
• Firmware Auto-Detection: The UR firmware identifies the UR8LH at slot level on startup, eliminating manual slot configuration steps and reducing commissioning time during module replacement in live substations.
• Deterministic Operate Time: The < 8 ms typical operate time is consistent across the rated temperature range, ensuring that protection trip signals are not delayed by thermal variation — a critical requirement for high-speed line differential and bus protection schemes.
• Dual-Standard EMC Compliance: Simultaneous compliance with IEC 61000-4 series and IEEE C37.90.1/C37.90.2 allows the UR8LH to be deployed in both IEC-standard international substations and IEEE-standard North American utility installations without hardware modification.
• Seismic Qualification: IEEE 693 Moderate Level seismic qualification supports installation in seismically active regions, including Pacific Rim substations and industrial facilities in earthquake-prone zones, without additional mechanical isolation measures.
• Long Mechanical Life: The ≥ 10,000,000 mechanical operation rating ensures multi-decade service life in protection relay applications where output contacts cycle infrequently — typically fewer than 100 operations per year in normal substation service — making premature contact wear a non-issue over a 20–30 year asset lifecycle.
• Wide Temperature Qualification: The −40 °C to +85 °C operating range covers the full spectrum of substation environments from arctic outdoor switchgear to tropical indoor control rooms, eliminating the need for environmental derating calculations in most installation scenarios.
• Backplane Power Supply: The module draws operating power entirely from the UR chassis backplane, eliminating the need for external auxiliary power wiring to the output module and simplifying panel design and maintenance procedures.

Quality Assurance & Global Logistics

Every UR8LH unit supplied through siemensplc.com is sourced as genuine GE Multilin hardware — not third-party compatible or rebranded substitute components. Units are procured through documented supply channels including authorized GE Multilin distributors and certified MRO partners with traceable service histories. Prior to dispatch, each module undergoes a structured pre-shipment inspection protocol: visual examination of the housing, connector pins, and label integrity; verification of the module’s firmware version and serial number against GE Multilin’s published hardware revision records; and functional contact continuity verification across all four output contacts.

Shipments originate from our warehouse in Xiamen, China — a major international logistics hub with direct access to DHL Express, FedEx International Priority, and UPS Worldwide Expedited services. Standard export documentation is prepared for every international order: commercial invoice, packing list, certificate of origin, and — where required — CITES or dual-use export compliance declarations. For bulk orders of five or more units, sea freight consolidation via Xiamen Port is available with full container load (FCL) and less-than-container load (LCL) options. Typical DHL Express transit times are 3–5 business days to Europe, 4–6 business days to North America, and 2–4 business days to Southeast Asia and the Middle East. All shipments are fully insured and tracked from dispatch to delivery confirmation.

A 12-month warranty covers each unit against manufacturing defects and contact failure under rated load conditions. Warranty claims are processed within 5 business days of receipt of the returned unit, with replacement dispatch or credit note issued upon verification. Serial number traceability is maintained for all units, supporting IEC 61850 asset management records and utility procurement audit requirements.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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