GE Multilin SR735-5-5-HI-485 – Feeder Protection Relay with 5 A CTs and RS‑485 Communications

The GE Multilin SR735 is a proven digital protection relay for medium‑ and low‑voltage feeders. The code “-5-5-HI-485” typically indicates 5 A current inputs and a high‑range universal auxiliary power supply, plus a rear RS‑485 port. From my experience, the SR735 is often chosen when teams want dependable 50/51 and ground fault protection, solid metering, and straightforward integration over Modbus RTU—without overcomplicating the scheme. You might notice that it also provides disturbance records and event logs, which can save a lot of troubleshooting time after a nuisance trip.

Company’s Order Placement Process and Guarantees

• Warranty: 365 days
• Delivery: 1 week if in stock; no more than 1 month latest
• Payment: 50% advance; full payment prior to delivery
• Express options: FedEx, UPS, DHL

Key Features

• Feeder overcurrent & earth fault (50/51, 50N/51N) – Time‑ and instantaneous‑overcurrent elements for phase and ground help protect cables, bus ties, and distribution feeders.
• Voltage‑based elements (with PTs) – Undervoltage/overvoltage (27/59) and, in many cases, under/over frequency (81) are available when VT inputs are used.
• Breaker failure logic (BF) – Typically used to back up the trip path if the primary breaker does not clear, improving system selectivity.
• Event, alarm, and waveform records – Sequence of Events (SOE) and oscillography make after‑action analysis faster; maintenance teams usually appreciate the clarity.
• Universal auxiliary power (HI) – Wide‑range AC/DC supply simplifies spares and panel standardization.
• RS‑485 Modbus RTU (485) – Easy SCADA connectivity; many sites tie SR735s into existing RTUs with minimal configuration.
• Metering & demand – Real‑time currents, voltages (with PTs), power, and energy values support operational decisions.
• Programmable logic and I/O – Discrete inputs and Form‑C outputs allow custom trip/alarm schemes without extra hardware.

Technical Specifications

Field note: one utility maintenance lead told us their SR735s “just keep working,” and the SOE logs helped them pinpoint a CT wiring inversion within minutes—something that used to take half a day with legacy electromechanical relays.

Related or Supporting Products

• GE Multilin 750/760 – Newer feeder management relays with enhanced logic and Ethernet options; often chosen when IEC 61850 is required.
• GE Multilin SR745 – Transformer protection; different application focus (differential and thermal models) if you are protecting a power transformer rather than a feeder.
• SEL‑751A – Alternative feeder protection with strong settings software and flexible I/O; Ethernet models available.
• ABB REF615 – Compact IEC 61850 feeder relay; good fit for standardized substation automation schemes.
• Accessories: SR‑series draw‑out test plug, RS‑232/USB configuration cable, CTs (5 A secondary), PTs (120 V L‑N nominal), and trip interposing relays if higher breaking capacity is needed.

Installation & Maintenance

• Cabinet & environment – Mount in a clean, dry, ventilated panel; maintain clear airflow around the relay; typical ambient −20…+60 °C. Follow EMI/EMC best practices with shielded control wiring and a single‑point ground.
• Wiring practices – Observe CT polarity (S1/S2) and short CT secondaries during installation; fuse PT circuits; torque terminals as specified. Keep signal and power wiring separated to minimize noise.
• Settings & checkout – Verify 50/51 curves, pickup, and time multipliers against coordination studies. Validate DI/DO logic and SCADA points over RS‑485 Modbus before energization.
• Routine maintenance – Back up settings after changes; review SOE/oscillography after any trip; perform secondary injection testing every 2–3 years. Firmware updates are typically managed via GE EnerVista tools.
• Safety – De‑energize control power when feasible; use CT shorting blocks; confirm absence of voltage on PT circuits before service. Lockout/tagout procedures apply.

Quality & Certifications

• Designed to meet utility‑grade standards (IEC 60255 class testing in many cases).
• CE and UL/cUL compliance typically available on SR‑series units; manufactured under ISO 9001 quality systems.
• Manufacturer’s warranty is generally 12 months; our supply warranty is 365 days as stated above.

If you’re standardizing on 5 A CTs and need a straightforward RS‑485 Modbus link, the SR735-5-5-HI-485 seems to be a practical fit. Many teams keep one spare on the shelf because it can drop into multiple feeder panels with only minor setting tweaks.