Description
Product Parameters
- Model Number: SR745-W2-P5-G5-HI-A
- Series: SR745 (745 Series)
- Winding Configuration (W2): 2-Winding Transformer Support
- Phase Current Inputs (P5): 5A Secondary Phase CTs
- Ground Current Inputs (G5): 5A Secondary Ground CTs
- Control Power (HI): 88–300V DC / 70–265V AC
- Analog Outputs (A): 0–20mA, 4–20mA, or 0–1mA (Configurable)
- Mounting: 19-inch Rack Mount (Horizontal)
- Weight: 18.1 lbs (8.2 kg)
- Dimensions: 8.8 in x 19.0 in x 9.3 in (22.3 cm x 48.3 cm x 23.6 cm)
GE SR745-W2-P5-G5-HI-A
GE SR745-W2-P5-G5-HI-A
GE SR745-W2-P5-G5-HI-A
The GE Multilin SR745-W2-P5-G5-HI-A is a high-speed, three-phase, microprocessor-based relay designed for the comprehensive protection and management of two-winding power transformers. It integrates multiple protective functions—such as percent differential, overcurrent, and restricted earth fault (REF) protection—into a single unit. Beyond protection, this relay provides advanced monitoring features, including harmonic analysis and an internal “Loss of Life” calculator that tracks transformer insulation aging based on load and temperature data.
Model Comparison
The SR745-W2 is designed for standard two-winding transformers, whereas the SR745-W3 variant is required for three-winding (autotransformer) applications. The P5-G5 designation indicates it is built for 5A CT secondaries; if your plant uses 1A secondaries, you would require the P1-G1 model. The HI power supply is the most common for industrial substations due to its wide input range, distinguishing it from the LO (24–48V DC) version. Compared to the newer 845 series, the SR745 remains a legacy standard due to its proven reliability and extensive install base in older power grids.
Operation Tips
- CT Ratio Configuration: Ensure the Phase and Ground CT ratios are entered correctly in the “System Setup” menu; incorrect ratios will lead to false differential trips or failure to trip during a genuine fault.
- Harmonic Restraint: Utilize the 2nd and 5th harmonic restraint settings to prevent nuisance tripping during transformer energization (inrush current) or over-excitation.
- Battery Check: The SR745 uses an internal lithium battery to maintain the event recorder and clock. Check the “Relay Healthy” status; if the battery fails, the relay will still protect the transformer, but historical event data will be lost during power cycles.
- Firmware Verification: When integrating into a DCS or SCADA system via Modbus, verify the firmware revision. Some older SR745 units require specific memory map adjustments to communicate correctly with modern 800xA or similar control platforms.
