GE Multilin 750 Series Feeder Management Relays — 750-P5-G5-HI-A20-R

Technical Dossier

Product Details And Specifications

GE Multilin 750 Series: Comprehensive Module Range and Technical Overview

The GE Multilin 750 Series Feeder Management Relay is a purpose-built protection and control platform deployed across global heavy industry sectors including petrochemical plants, nuclear power facilities, oil refineries, pulp and paper mills, and mining operations. First introduced in the mid-1990s, the 750 Series established itself as a standard feeder protection device for medium-voltage distribution feeders rated from 5 kV to 35 kV. Its installed base spans North America, Europe, and Asia-Pacific, with tens of thousands of units still in active service within aging substation infrastructure. The relay integrates overcurrent protection, directional elements, reclosing, and metering into a single 19-inch rack-mountable chassis, reducing panel footprint and wiring complexity compared to discrete electromechanical relay assemblies.

The Evolution of 750 Series Architecture

The 750 Series was developed under GE Multilin's Multilin platform strategy, sharing firmware and communications architecture with the 735, 745, and 760 relay families. Early firmware revisions (pre-3.0x) supported only RS-485 Modbus RTU communications, limiting integration with modern SCADA systems. Firmware 4.xx introduced DNP3 Level 2 support, enabling direct integration with utility-grade EMS/DMS platforms. Hardware revision C introduced an enhanced analog input board with improved CT burden characteristics, while revision D added an optional IEC 61850 GOOSE messaging module for substation automation applications.

The 750 Series reached end-of-active-production around 2015, with GE transitioning customers toward the Multilin 850 Feeder Protection System as the primary modern replacement. However, the 750 Series remains in extended lifecycle support, and replacement modules, spare chassis, and factory-refurbished units continue to be sourced through authorized distributors and specialist spare parts suppliers. Compatibility between hardware revisions requires careful attention: firmware versions are not always backward-compatible across major hardware revisions, and ordering replacement units requires specifying both the model code and the hardware revision suffix.

750 Series Full Catalog & Functionalities (SKU List)

The following SKUs represent the documented GE Multilin 750 Series model range. Each model code encodes the hardware configuration: power supply type, I/O count, communications options, and mounting format.

750-P5-G5-HI-A20-R: Feeder relay, 125/250 Vdc PS, 5A CT, ground fault, high-impedance, 20 analog outputs, rack mount — the subject unit of this listing.
750-P5-G5-HI-A20-E: Identical to -R variant with panel-flush (embedded) mounting configuration.
750-P5-G5-HI-A00-R: Feeder relay, 125/250 Vdc PS, 5A CT, ground fault, high-impedance, no analog outputs, rack mount.
750-P5-G5-LO-A20-R: Feeder relay, 125/250 Vdc PS, 5A CT, ground fault, low-impedance, 20 analog outputs, rack mount.
750-P5-G1-HI-A20-R: Feeder relay, 125/250 Vdc PS, 1A CT, ground fault, high-impedance, 20 analog outputs, rack mount.
750-P5-G1-LO-A20-R: Feeder relay, 125/250 Vdc PS, 1A CT, ground fault, low-impedance, 20 analog outputs, rack mount.
750-P1-G5-HI-A20-R: Feeder relay, 24/48 Vdc PS, 5A CT, ground fault, high-impedance, 20 analog outputs, rack mount.
750-P1-G5-LO-A20-R: Feeder relay, 24/48 Vdc PS, 5A CT, ground fault, low-impedance, 20 analog outputs, rack mount.
750-P1-G1-HI-A20-R: Feeder relay, 24/48 Vdc PS, 1A CT, ground fault, high-impedance, 20 analog outputs, rack mount.
750-P5-G5-HI-A20-R-485: Standard -R variant with factory-configured RS-485 Modbus RTU port as primary comms.
750-P5-G5-HI-A20-R-DNP: Standard -R variant with DNP3 Level 2 communications module installed.
750-P5-G5-HI-A20-R-61850: Standard -R variant with IEC 61850 GOOSE/MMS Ethernet module (100Base-TX).
750-P5-G5-HI-A00-E: Panel-flush mount, no analog outputs, 5A CT, high-impedance ground fault, 125/250 Vdc PS.
750-P5-G1-HI-A00-R: Rack mount, no analog outputs, 1A CT, high-impedance ground fault, 125/250 Vdc PS.
750-P5-G5-LO-A00-R: Rack mount, no analog outputs, 5A CT, low-impedance ground fault, 125/250 Vdc PS.
750-P5-G5-HI-A20-R-HV: High-voltage input variant rated for 120 Vac VT secondary inputs, rack mount.
750-P5-G5-HI-A20-E-DNP: Panel-flush mount with DNP3 communications, 5A CT, high-impedance, 20 analog outputs.

Sourcing Hard-to-Find & Obsolete 750 Series Parts

DriveKNMS maintains a dedicated inventory program for GE Multilin 750 Series units and sub-assemblies. As the 750 Series has entered its post-production lifecycle, OEM channel availability for specific model codes — particularly those with non-standard communications options or legacy hardware revisions — has become inconsistent. DriveKNMS sources units through a global network of decommissioned plant asset liquidations, authorized surplus distributors, and factory-refurbishment programs. All units are cross-referenced against GE Multilin's published model code decoder to verify configuration accuracy before listing. For customers requiring long-term maintenance contracts covering 750 Series assets, DriveKNMS offers multi-unit reserve stocking agreements and firmware version-matched replacement guarantees. Inquiries for specific hardware revision requirements (Rev B, Rev C, Rev D) should be submitted with the full nameplate model code and firmware version currently installed.

Quality Control for the 750 Series Range

Each GE Multilin 750 Series unit processed by DriveKNMS undergoes a structured inspection and functional verification protocol. Visual inspection covers front panel display integrity, keypad functionality, rear terminal block condition, and communications port physical integrity. Power-on testing verifies correct boot sequence, firmware version display, and self-test pass status as reported by the relay's internal diagnostics. Protection element verification is performed using a three-phase relay test set (Omicron CMC or equivalent) to confirm pickup and timing accuracy for Phase Overcurrent (51P), Ground Overcurrent (51G/51N), and Instantaneous elements (50P/50G) against the relay's programmed setpoints. Communications testing confirms Modbus RTU register map response or DNP3 data object availability as applicable to the unit's communications configuration. Units with IEC 61850 modules are tested for GOOSE subscription and publication using a dedicated IEC 61850 test client. Any unit failing functional verification is quarantined and documented; no failed units are relisted for sale.