GE Multilin 750-P1-G1-S1-HI-A20-G – Feeder Protection Relay for Reliable MV/LV Distribution

The GE Multilin 750-P1-G1-S1-HI-A20-G is a feeder management relay designed for dependable overcurrent and ground fault protection on medium and low-voltage feeders. From my experience, the 750 series strikes a good balance between protection depth, metering detail, and day-to-day maintainability. It typically suits switchgear upgrades where you want modern communications and event records without overcomplicating the scheme.

• Feeder and Ground Protection – Time/instantaneous overcurrent with dedicated ground fault elements for fast clearing and coordination.

• P1 current inputs (1 A nominal) – The P1 code indicates 1 A CT inputs, which is ideal when your existing scheme is built around 1 A secondary CTs.

• High-range universal control power (HI) – Typically 90–300 VDC or 70–265 VAC, so it adapts well to most substation DC supplies and station service AC.

• Analog transducer outputs (A20) – 4–20 mA analog outputs for SCADA/PLC metering, helpful when an analog input card is already in place.

• Serial communications (S1) – RS485/RS232 for Modbus RTU; in many cases DNP3 is supported on this platform for utility integration.

• Event and fault records – Time-stamped logs and oscillographic data to speed up root cause analysis and improve coordination studies.

• Configurable I/O – Opto-isolated digital inputs and Form-C outputs, typically used for breaker status, trip, close, and interlocks.

• Draw-out cradle (G) – You might notice the draw-out case makes testing and replacement simpler without disturbing the panel wiring harness.

• Clear front HMI – Local measurements, targets, and diagnostics available without needing a laptop, which seems to be a time saver for operations.

The 750 series is at home in metal-clad switchgear, MCC incomer feeders, and plant distribution panels. In most cases, it’s used on feeders from 3.3 kV up to 33 kV, but it’s equally useful on critical low-voltage distribution where selective coordination matters.

• Utility and industrial substations – Feeder protection with SCADA tie-in over RS485.

• Oil, gas, and chemicals – Reliable trip logic for process-critical distribution.

• Data centers and hospitals – Fast fault isolation to protect UPS and downstream breakers.

• Mining and metals – Rugged draw-out design simplifies maintenance in harsh environments.

• Water/wastewater – Straightforward Modbus mapping to existing PLC/SCADA systems.

• Fits legacy 1 A CT schemes – The P1 input rating reduces retrofit friction and CT replacement costs.

• Universal power supply – Fewer variants to stock and simpler BOMs for projects with mixed DC/AC control power.

• Maintenance-friendly – Draw-out case and clear front HMI cut down outage time during testing.

• SCADA-ready – Serial comms and 4–20 mA outputs integrate quickly with existing DCS/PLC infrastructure.

• Lifecycle support – Widely deployed platform; spare parts, test plugs, and knowledge base are easy to find.

“We swapped older electromechanical relays for the 750s and kept our 1 A CTs. Commissioning went smoother than expected, and the Modbus points dropped straight into our existing SCADA tags.” — Maintenance Supervisor, power distribution upgrade

• Panel and cabinet – Mount in a clean, ventilated enclosure; allow clearance at the rear for wiring and heat dissipation. Avoid high-vibration zones where practical.

• Wiring – Observe CT polarity and shorting practices; use twisted/shielded pairs for serial comms (RS485). Keep control power within the HI range.

• Grounding – Bond the relay chassis and cable shields at one end to minimize noise and nuisance operations.

• Testing – Use a secondary injection set; verify pickup, time curves, and trip logic before energization. Draw-out design typically supports safer isolation during tests.

• Routine care – Periodic dust cleaning, functional tests each outage cycle, and configuration backups. Firmware updates should be applied following vendor release notes and site change-control.

• CE compliant; UL/cUL and CSA certifications are commonly associated with this series.

• RoHS alignment on most modern builds of the platform.

• Manufacturer’s warranty typically multi-year (region and supply program dependent); extended service plans available in many cases.

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If you’re matching this relay to an existing protection scheme, the model breakdown here is practical: P1 (1 A CTs), G1 (ground package), S1 (serial comms), HI (universal power), A20 (4–20 mA outputs), G (draw-out). If your site needs Ethernet or different I/O counts, we can suggest adjacent 750 configurations or the compatible 760 variant.