Description
GE SR745-W3-P5-G5-HI-ALR-E-H — Transformer Protection Relay
Product: SR745-W3-P5-G5-HI-ALR-E-H, Numerical Transformer Protection Relay
Manufacturer: GE (General Electric) — now part of GE Vernova (Grid Solutions)
Product Line: Multilin 745 Series
Primary Application: A comprehensive numerical protection relay specifically designed for the protection, control, and monitoring of two-winding power transformers in utility substations, industrial plants, and renewable energy installations.
1. Core Overview & Positioning
The GE Multilin SR745 is a sophisticated numerical relay engineered specifically for power transformer management. The extended order code «SR745-W3-P5-G5-HI-ALR-E-H» defines the exact hardware configuration, communication options, and feature set for this unit. It integrates multiple protection functions, advanced monitoring, and control capabilities into a single device, replacing numerous discrete relays and meters.
Key Value: It provides complete transformer management with advanced protection algorithms, extensive metering, and flexible communication options, ensuring maximum equipment protection, availability, and grid code compliance.
2. Key Protection & Control Functions
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Transformer Differential Protection (87T): Percentage-restrained, dual-slope differential protection as the primary scheme, with 2nd and 5th harmonic blocking/restraint for secure operation during transformer inrush and overexcitation.
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Restricted Earth Fault (64REF): High-sensitivity ground fault protection for the transformer windings.
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Overcurrent Protection:
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Phase Time Overcurrent (51) and Instantaneous (50).
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Ground Time Overcurrent (51N/G) and Instantaneous (50N/G).
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Neutral Time Overcurrent (51N).
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Transformer-Specific Protection:
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Thermal Overload (49): Implements a dual-time constant thermal model (IEEE/ANSI) to protect the transformer from overheating damage.
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Overexcitation (Volts/Hertz) Protection (24).
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Over/Under Voltage (59/27) and Frequency (81O/U) protection.
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Control & Automation:
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Breaker Failure Protection (50BF).
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Programmable Logic (FlexLogic™): Allows creation of custom control schemes, interlocking, and automation sequences without external hardware.
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Multiple Setpoint Groups: For changing protection settings based on topology (e.g., different settings for different tap positions or system configurations).
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3. Monitoring, Metering & Diagnostics
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Comprehensive Measurement: All phase currents and voltages, sequence components, real/reactive/apparent power (P, Q, S), power factor, frequency, and energy (kWh, kVArh) with pulse outputs.
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Disturbance & Event Recording: High-resolution oscillographic fault recording (COMTRADE format) and time-stamped event logs for post-mortem analysis.
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Transformer Monitoring: Can interface with RTDs (via optional module) for direct winding and oil temperature monitoring, and calculate a simulated hotspot temperature.
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Advanced Diagnostics: Continuous self-diagnostics for hardware and software integrity.
4. System Integration
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Engineering Tools: Configured using GE’s Enervista UR Setup software. All protection settings, FlexLogic™ schemes, and communication mapping are defined here.
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Communication: Acts as an IEC 61850 Intelligent Electronic Device (IED) on the substation LAN. It reports to SCADA via IEC 61850 MMS or DNP3.0, and can exchange high-speed peer-to-peer signals using GOOSE for interlocking or breaker failure schemes.
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Wiring: Connects directly to transformer HV and LV side CTs (5A as per
P5), voltage transformers (VTs), and the circuit breaker trip/close circuits via its output relays (G5).
5. Typical Applications
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Utility Substations: Protection of step-up (generator) and step-down (distribution) transformers.
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Industrial Plants: Primary protection for main plant transformers and large process transformers.
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Renewable Energy: Protection of the main power transformer in wind farms or solar PV plants.
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Autotransformers: Can be applied with appropriate configuration and careful consideration of the common winding.
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