GE 745-W2-P5-G5-HI Transformer Protection Relay

The GE Multilin 745-W2-P5-G5-HI (also designated with the -AR suffix package) belongs to the 745 Transformer Protection System series. It operates as a high-speed, multi-processor transformer management relay engineered to protect and manage two-winding power transformers within industrial and utility power automation systems. This base unit configuration integrates percentage differential protection, harmonic analysis, overexcitation elements, and programmable control logic into a modular platform.

Hardware Specifications

Backplane Bus Communication Velocity and Firmware Architecture

The multi-processor core inside the 745 series relies on an optimized data bus structure to maintain high communication velocity across its internal backplane. Maintaining precise firmware flash compatibility across all active registers allows the system to continuously capture and cross-reference variables from the 5 A winding inputs, ground transformers, and analog tap changers simultaneously.

Analog signals enter the relay through shielded isolation loops where they are converted into high-resolution digital data streams. The core processing plane ingests these streams in real time to compute percentage differential equations, individual harmonics, and Total Harmonic Distortion (THD). When a fault condition matches the configured parameters, trip commands are executed down to millisecond intervals, bypassing typical bus latency to actuate external breakers while logging waveform captures and diagnostic event states instantly.

Frequently Asked Questions

Q: How does the harmonic monitoring subsystem inside the 745-W2-P5-G5-HI prevent nuisance trips during transformer energization?

A: When a power transformer is first energized, it generates a high-magnitude inrush current that can look like an internal short circuit to standard overcurrent relays. The 745 model computes individual harmonics—specifically targeting the 2nd and 5th harmonic components—and uses a percentage differential blocking function. Because transformer inrush contains high harmonic content compared to actual faults, the relay identifies the state and blocks accidental trip execution.

Q: What safety precautions are integrated into the SR-series draw-out chassis regarding current transformer lines?

A: The SR-series companion outer case features integrated, automatic mechanical shorting bars on its backplane terminal plate. When a technician extracts the inner relay unit for calibration or testing, these shorting mechanisms mechanically bridge the 5 A phase and ground current transformer secondary circuits before they can break connection. This prevents hazardous high-voltage open-circuit arcs across the active current loops.