GE SR750-P5-G5-S5-HI-A20-R-T — Feeder Protection Relay (SR Series 750)

Quick Description

The GE SR750-P5-G5-S5-HI-A20-R-T is a programmable microprocessor-based feeder protection relay from GE’s SR 750 Series. It is designed to protect medium-voltage and low-voltage feeders in utility, industrial, and commercial power distribution systems.
This relay provides advanced protection, metering, event recording, automation logic, and multi-protocol communication, making it suitable for both new substations and retrofit applications.

---

Key Functions & Protection Elements

• Phase & ground overcurrent protection (50/51, 50N/51N)

• Thermal overload protection (49)

• Breaker failure protection (50BF)

• Under/overfrequency & voltage protection (81, 27, 59)

• Demand, energy, and power factor metering

• Trip / close coil supervision & breaker health diagnostics

• Programmable logic (FlexLogic™) for custom automation

• Sequence-of-events, waveform disturbance recorder, and fault logging

  
  

---

Hardware / Option Code Meaning 

Code Section	Meaning
P5	5 Amp CT input rating
G5	Communication option (Ethernet + RS-485 multiprotocol)
S5	Standard I/O package with programmable outputs
HI	HMI with front panel display & keypad
A20	20 records oscillography memory depth
R	Conformal coated board (harsh-environment protection)
T	Harsh temperature rating (ext. industrial range)

---

Technical Parameters 

• Nominal Current Inputs: 1 A or 5 A selectable

• Control Power: 48–250 V DC / 100–240 V AC

• Operating Temperature Range: −40 °C to +70 °C (T-rated)

• Front Display: 40-character multi-line LCD with status LEDs

• Memory & Recording: 20 oscillography event files, 1024 SOE time-stamped events

• Accuracy: IEC 60255 class metering & protection grade

• Communications: Ethernet TCP/IP, Modbus, DNP3, IEC 61850 (G5 option), RS-485 serial

• Mounting Style: Draw-out chassis, 19-inch rack or panel cut-out

• Trip Outputs: Form-C relay contacts, user programmable

• Cybersecurity: Password lockout + role-based access (firmware dependent)

---

Internal Architecture

1. Protection DSP – Executes real-time relay algorithms

2. Metering Stage – True RMS measurement for energy & demand values

3. High-speed Trip Outputs – Mechanical relays rated for breaker coils

4. Event / waveform memory – Non-volatile flash for fault forensics

5. Communication Processor – Manages SCADA, IEC 61850, gateway protocols

6. HMI Panel – Local configuration, alarm acknowledgment, breaker controls

   
   

---

Application Scenarios

• Primary/secondary distribution feeders (3-phase, 50/60 Hz)

• Industrial switchgear / MCC feeder protection

• Ring and radial feeder automation in utilities

• Renewable energy collector circuits (wind, solar, hydro)

• Smart-grid SCADA and substation automation

• Retrofit of legacy electromechanical relays (same form factor cutout)

---

Installation & Commissioning Notes

• Install in draw-out cradle to allow relay replacement without rewiring

• CT polarity and grounding must follow ANSI or IEC wiring diagrams

• Recommended to perform primary injection testing before energizing feeder

• Time sync may be via IRIG-B, SNTP, or SCADA (depending on comms option)

• Configure and upload settings using EnerVista SR configuration software

---

Maintenance & Lifecycle Support

• Relay is self-monitoring; front panel shows “Relay OK / Relay Fail” alarm

• Trip contacts rated for 30,000+ mechanical operations

• Event logs and oscillography can be exported via USB or Ethernet

• Firmware upgradable using GE EnerVista Toolsuite

• Suggested spare inventory: 1 relay for every 10–12 feeders in a station

---

Additional Notes

• The SR750 series is part of the same family as SR469, SR489, SR759, etc.

• UL, CE, CSA, and IEEE C37.90 certified for protection systems

• Still supported by GE Grid Solutions with firmware/security updates