SR735 Feeder Protection Relay (Industrial-Grade Microprocessor Control)

The GE 735-5-5-HI-485 represents a proven solution in feeder circuit protection, combining microprocessor intelligence with RS485 Modbus RTU connectivity for modern substation environments. This SR735 series device delivers multi-function protection including phase overcurrent, ground fault detection, and directional elements—engineered to safeguard medium-voltage distribution feeders against electrical faults while maintaining operational continuity.

Designed for utility substations, industrial power distribution centers, and renewable energy facilities, this relay addresses the critical challenge of coordinating protection across complex radial and networked feeder configurations. System integrators and electrical engineers rely on the 735-5-5-HI-485 for its field-proven reliability, flexible CT/VT inputs, and seamless SCADA integration capabilities that reduce downtime and enhance grid visibility.

Key differentiators include programmable protection curves compliant with ANSI/IEEE standards, a 40-character backlit LCD interface for on-site diagnostics, and wide-range auxiliary power input (20-300V AC/DC) that simplifies installation across diverse voltage environments. The integrated RS485 port enables real-time data exchange with supervisory systems, supporting predictive maintenance strategies and rapid fault analysis.

Core Protection Functions & Technical Advantages

→ Multi-Stage Overcurrent Protection
Configurable time-overcurrent (TOC) and instantaneous overcurrent (IOC) elements for phase and ground faults. Supports IEC, IEEE, and customizable trip curves with 0.01-second resolution, ensuring selective coordination with upstream/downstream devices to isolate faults without cascading outages.

→ Directional Fault Discrimination
Built-in directional overcurrent logic prevents nuisance tripping in parallel feeder or loop configurations. Voltage-polarized directional elements accurately determine fault direction, critical for maintaining service continuity in interconnected distribution networks.

→ RS485 Modbus RTU Connectivity
Native Modbus protocol (300-19200 bps) facilitates integration with legacy and modern SCADA platforms. Retrieve real-time measurements, fault records, and relay status remotely—reducing site visits and enabling centralized monitoring across multiple substations.

✓ Flexible CT/VT Configuration
Accepts 1A or 5A secondary current inputs with programmable primary ratios up to 50000:1. Voltage inputs accommodate phase-phase or phase-neutral connections, adapting to various transformer and feeder configurations without hardware modifications.

✓ Event Recording & Fault Analysis
Stores up to 40 time-stamped event records with pre-fault and post-fault waveform capture. Oscillography data aids root-cause analysis, helping engineers optimize protection settings and identify recurring system weaknesses.

✓ Rugged Industrial Construction
Operates reliably in harsh environments (-40°C to +85°C) with IEC 60255 compliance for shock, vibration, and EMI immunity. Panel-mount or rack-mount options suit both retrofit and new-build substation projects.

Industrial Application Scenarios

Utility Distribution Substations
Protect 11kV-33kV outgoing feeders in primary substations serving urban and rural networks. The relay's directional elements prevent false trips during backfeed conditions, while Modbus integration enables utility operators to monitor feeder loading and fault statistics across geographically dispersed sites.

Manufacturing & Process Industries
Safeguard critical production feeders in chemical plants, steel mills, and automotive facilities where unplanned outages result in costly production losses. Programmable I/O contacts trigger automatic load shedding or backup generator start sequences during fault conditions.

Renewable Energy Installations
Coordinate protection for solar farm inverter feeders and wind turbine collector systems. The relay's sensitive ground fault detection (down to 5% of rated current) meets stringent grid code requirements for distributed generation interconnection.

Data Centers & Mission-Critical Facilities
Provide backup protection for UPS-fed distribution boards and generator tie feeders. Fast fault clearing (sub-cycle trip times) minimizes arc flash energy and equipment damage, supporting uptime SLAs in Tier III/IV facilities.

Mining & Heavy Industry
Withstand extreme temperature swings and vibration in underground substations and mobile equipment feeders. The relay's sealed front panel (IP52 rating) resists dust and moisture ingress common in mining environments.

Technical Parameters & Selection Criteria

Selection Guidelines: Choose the 735-5-5-HI-485 when your application requires directional overcurrent protection with Modbus connectivity. For feeders without directional requirements, consider non-directional SR735 variants. If IEC 61850 protocol is mandatory, evaluate GE's newer MiCOM or UR-series relays. Verify CT secondary ratings match your existing installation (1A vs 5A) to avoid field modifications.

Advanced Integration & Customization Options

SCADA System Integration: The relay's Modbus register map provides access to 100+ data points including real-time currents, voltages, power measurements, and protection element status. Configure polling intervals and exception reporting to balance network bandwidth with data freshness requirements.

Custom Protection Schemes: Utilize programmable logic equations to create application-specific interlocks, such as blocking reclosure during maintenance mode or coordinating with upstream sectionalizers. The relay supports up to 16 user-defined logic gates combining analog measurements and digital inputs.

Cybersecurity Considerations: While RS485 Modbus lacks native encryption, deploy the relay behind secure network gateways or protocol converters with VPN/firewall capabilities when connecting to enterprise IT networks. Implement password protection and access logging via the relay's security settings.

Delivery Timeline & Service Commitments

Standard Lead Time: 3-5 business days for in-stock units (express shipping available to major industrial hubs). Custom-configured relays with factory programming require 10-15 business days.

Warranty Coverage: 12-month manufacturer's warranty covering material defects and workmanship. Extended warranty plans available for critical infrastructure applications.

Technical Support: Lifetime access to our application engineering team for configuration assistance, protection coordination studies, and firmware updates. On-site commissioning services available upon request.

Documentation Package: Each relay ships with instruction manual, quick-start guide, Modbus register map, and AutoCAD panel cutout drawings. Relay setting files (.735 format) compatible with GE's EnerVista SR735 Setup software (free download).

Frequently Asked Questions

How does the RS485 Modbus interface connect to my existing SCADA system?
The relay provides a 2-wire RS485 port (terminals TB3-1 and TB3-2) supporting Modbus RTU slave mode. Connect to your SCADA master via twisted-pair cable (Belden 3105A or equivalent), observing proper termination resistors (120Ω) at network endpoints. Configure slave address (1-247) and baud rate (9600 bps typical) via the front-panel HMI or EnerVista software.

Can I retrofit this relay into panels originally designed for electromechanical relays?
Yes—the 1/2 rack width form factor matches legacy GE/Westinghouse relay footprints. Verify panel cutout dimensions (96mm × 144mm) and ensure adequate depth clearance (185mm behind panel). CT/VT wiring typically requires minimal changes, though you may need to add auxiliary power supply if not already present.

What CT accuracy class is required for proper relay operation?
Minimum 5P10 or C100 class CTs recommended for protection applications. For sensitive ground fault settings below 20% pickup, consider 5P20 or higher accuracy class to maintain performance during through-fault conditions. The relay's wide dynamic range (0.05-40× rated current) accommodates most standard protection-class CTs.

Does the relay support DNP3 or IEC 61850 protocols?
The 735-5-5-HI-485 model is limited to Modbus RTU. For DNP3 Level 2 compliance, investigate GE's UR-series relays (e.g., UR F35). IEC 61850 Edition 2 support requires MiCOM P14x or newer GE Grid Solutions products. Protocol converters can bridge Modbus to DNP3/61850 if hardware replacement isn't feasible.

What is the typical commissioning time for a single relay installation?
Experienced technicians complete installation and basic commissioning in 3-4 hours, including CT/VT verification, protection setting entry, and functional testing. Complex applications with custom logic or SCADA integration may require an additional 2-3 hours for validation and documentation.

How do I update relay firmware or retrieve fault records?
Connect a PC running EnerVista SR735 Setup software to the relay's front RS232 port (RJ45 connector) using a null-modem adapter. The software enables firmware uploads, setting file transfers, and oscillography download. Alternatively, retrieve basic event logs via Modbus registers 4000-4999 for remote diagnostics.

Order Your GE SR735 Feeder Protection Relay Today

Secure your electrical distribution infrastructure with the proven reliability of GE Multilin technology. Our technical sales team is ready to assist with protection coordination studies, relay configuration templates, and volume pricing for multi-unit projects. Contact us now to discuss your specific feeder protection requirements and receive a detailed quotation within 24 hours.

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