SR750 Feeder Protection Relay (Industrial-Grade Distribution Control)

The GE 750-P5-G5-S5-HI-A20-R-T is an enterprise-class feeder management relay engineered to safeguard medium-voltage distribution networks against overcurrent faults, voltage anomalies, and frequency deviations. Built on the proven SR750 platform, this relay delivers multi-function protection, real-time metering, and programmable logic control in a single compact unit.

Designed for electric utilities, industrial power systems, and mission-critical facilities, the 750-P5-G5-S5-HI-A20-R-T addresses the growing complexity of modern distribution grids—including bi-directional power flows from distributed energy resources, dynamic load profiles, and stringent reliability requirements. Its modular architecture supports seamless integration with legacy SCADA infrastructure while providing a migration path to IEC 61850-compliant substation automation.

With 20 programmable output contacts, high-resolution graphical display, and dual-protocol communication (Modbus RTU + DNP3), this relay serves as the intelligent nerve center for feeder circuit monitoring and control. Whether protecting radial feeders in utility substations or managing complex industrial distribution loops, the SR750 delivers the precision, flexibility, and reliability demanded by today's power systems.

Core Features & Technical Advantages

→ Multi-Element Protection Suite: Integrates phase/ground time-overcurrent (51/51N), directional overcurrent (67/67N), under/overvoltage (27/59), and under/overfrequency (81U/O) elements—eliminating the need for multiple discrete relays and reducing panel space by up to 40%.

✓ Directional Sensitivity: Sophisticated directional algorithms distinguish forward vs. reverse fault currents, enabling proper coordination in looped networks, parallel feeders, and systems with distributed generation—critical for preventing nuisance trips and ensuring selective fault isolation.

→ Extensive I/O Capacity: 20 Form-C output relays (A20 configuration) provide independent trip/close/alarm contacts for breakers, reclosers, and annunciation systems. Eight programmable digital inputs (S5) accept remote control commands, breaker status feedback, and external protection signals.

✓ Advanced Metering & Diagnostics: Captures RMS voltage, current, real/reactive/apparent power, energy (kWh/kVArh), power factor, and THD harmonics at 1-second resolution. Built-in oscillography records fault waveforms for post-event analysis and protection scheme validation.

→ Dual-Protocol Connectivity: Native RS485 Modbus RTU and DNP3 Level 2 support enables plug-and-play integration with Schneider Electric, Siemens, ABB, and SEL SCADA platforms. Optional fiber-optic communication modules available for EMI-sensitive environments.

✓ Intuitive HMI: High-contrast graphical LCD (HI display) presents real-time metering, event logs, and protection status without external software. Front-panel keypad allows on-site setting adjustments and relay testing—reducing commissioning time by 30%.

Application Scenarios & Industry Use Cases

Electric Utility Distribution Substations: Primary feeder protection for 4.16kV to 34.5kV radial and looped distribution circuits. Coordinates with upstream transformer differential relays and downstream recloser controls to achieve selective fault clearing. Typical deployment: 12-feeder substation with centralized SCADA monitoring via DNP3 over fiber-optic network.

Industrial Manufacturing Facilities: Critical process feeder monitoring in automotive plants, semiconductor fabs, and chemical processing facilities where unplanned outages cost $50K-$500K per hour. Integrates with motor protection relays, generator controls, and emergency power systems to maintain production continuity during grid disturbances.

Data Centers & Telecom Infrastructure: Feeder-level protection for Tier III/IV data centers requiring 99.982%+ uptime. Works in tandem with automatic transfer switches (ATS), UPS systems, and generator paralleling controls. Real-time power quality monitoring detects voltage sags, swells, and harmonic distortion before IT equipment damage occurs.

Renewable Energy Integration: Bi-directional protection for distribution feeders with solar PV, wind, or battery storage interconnections. Directional overcurrent elements prevent reverse power flow trips while maintaining grid code compliance (IEEE 1547, UL 1741). Supports anti-islanding detection and voltage ride-through requirements.

Mining & Heavy Industry: Ruggedized protection for mobile substations, dragline excavators, and conveyor systems in harsh environments (-40°C to +70°C operating range). Withstands shock, vibration, and electrical noise per IEC 60255-21-1 and IEEE C37.90.2 standards.

Technical Parameters & Selection Guide

Selection Criteria: Choose the 750-P5-G5-S5-HI-A20-R-T when you require maximum I/O flexibility (20 outputs vs. standard 10-output models), graphical display for on-site diagnostics, and IRIG-B time synchronization for multi-relay event correlation. For applications with fewer I/O requirements, consider the 750-P5-G5-S5-HI-A10-R variant. If Ethernet connectivity is preferred over RS485, specify the 750-P5-G5-S5-HI-A20-E-T model.

Extended Capabilities & System Integration

Programmable Logic Control: Built-in FlexLogic™ engine with 128 logic gates enables custom protection schemes, automatic load transfer, and demand response functions without external PLCs. Example applications include generator synchronization interlocks, capacitor bank switching control, and voltage regulator coordination.

IIoT & Cloud Connectivity: When paired with GE Grid Solutions' ePAC gateway, the SR750 streams real-time data to cloud-based analytics platforms for predictive maintenance, asset health monitoring, and grid optimization. Machine learning algorithms detect incipient faults 6-12 months before catastrophic failure.

Cybersecurity Features: Role-based access control (RBAC), encrypted communication (TLS 1.2), and audit logging comply with NERC CIP-005/007 requirements for critical infrastructure protection. Firmware authentication prevents unauthorized code injection.

Customization Options: Factory configuration services available for pre-programmed protection settings, custom faceplate labeling, and application-specific logic templates. Reduces on-site commissioning time from 8 hours to 2 hours per relay.

Delivery, Warranty & Technical Support

Lead Time: Standard configuration units ship within 3-5 business days from our regional distribution center. Custom-configured relays (pre-programmed settings, special I/O modules) require 2-3 weeks. Expedited shipping available for critical outage replacements.

Warranty Coverage: 12-month comprehensive warranty covers manufacturing defects, component failures, and firmware issues. Extended 3-year and 5-year warranty plans available at 15% and 25% of unit price respectively. Warranty includes firmware updates and technical support.

Technical Support: Unlimited phone/email support from GE-certified protection engineers during warranty period. Remote commissioning assistance via TeamViewer or AnyDesk. On-site commissioning services available at $1,500/day + travel expenses.

Documentation Package: Each relay ships with installation manual (150+ pages), protection setting guidelines, Modbus/DNP3 register maps, AutoCAD panel cutout drawings, and sample SCADA configuration files. Online training videos and webinars available at no charge.

Frequently Asked Questions

Q: What is the maximum CT ratio this relay can accommodate?
A: The 750-P5-G5-S5-HI-A20-R-T supports CT ratios from 50:5 to 6000:5 with 0.01A sensitivity. For higher ratios (up to 12000:5), use external CT interposing transformers. The relay automatically compensates for CT ratio settings in protection and metering calculations.

Q: Can I retrofit this relay into an existing GE SR745 installation?
A: Yes, the SR750 maintains backward compatibility with SR745 panel cutouts (96mm x 96mm) and terminal block layouts. Settings can be migrated using GE's EnerVista SR750 Setup software. Communication protocols (Modbus/DNP3) are fully compatible, requiring no SCADA master station changes.

Q: How does directional overcurrent protection work in systems with distributed generation?
A: The relay calculates fault current direction using voltage and current phasor relationships (wattmetric or reactance method). When solar PV or wind generation causes reverse power flow, the 67/67N elements distinguish between forward faults (trip) and reverse faults (block or alarm). This prevents false trips during islanding conditions or backfeed scenarios.

Q: What communication speed does the RS485 port support?
A: The 'R' communication module supports baud rates from 300 to 115,200 bps (typically configured at 9600 or 19,200 bps for Modbus RTU). DNP3 protocol operates at the same baud rates with configurable data link layer timeouts. Maximum RS485 network distance: 4,000 feet (1,200 meters) without repeaters.

Q: Is this relay suitable for arc flash reduction applications?
A: Absolutely. The SR750's high-speed instantaneous overcurrent elements (50/50N) can trip in 16-33 milliseconds, significantly reducing arc flash incident energy. When combined with zone-selective interlocking (ZSI) using digital inputs, the relay achieves selective coordination while maintaining fast fault clearing for personnel safety.

Q: Can I monitor power quality parameters like voltage harmonics and flicker?
A: Yes, the relay measures total harmonic distortion (THD) for voltage and current up to the 31st harmonic. Individual harmonic magnitudes and phase angles are accessible via Modbus/DNP3 registers. For advanced power quality analysis (flicker, transients, sags/swells), consider pairing with a dedicated PQ meter or upgrading to the SR750 with enhanced metering option.

Ready to Upgrade Your Feeder Protection?

The GE 750-P5-G5-S5-HI-A20-R-T SR750 Feeder Management Relay represents the optimal balance of protection performance, operational flexibility, and lifecycle value for modern distribution systems. Whether you're replacing aging electromechanical relays, standardizing on a multi-vendor protection platform, or designing a greenfield substation, the SR750 delivers proven reliability backed by GE's 130+ years of power system expertise.

Contact our protection specialists today for application engineering support, competitive pricing, and fast delivery. Volume discounts available for multi-unit projects (10+ relays). Trade-in credit offered for legacy GE, ABB, Siemens, and SEL relays.

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