Description
The Woodward IRI1-I5E05D is a microprocessor-based earth fault relay from the HighPROTEC IRI series, originally developed by SEG and continued under Woodward following the acquisition . As a dedicated ground fault protection device (ANSI 50N/51N), the IRI1-I5E05D provides high-sensitivity earth fault detection for generators, transformers, high-voltage motors, and switchgear in industrial AC systems .
The IRI1-I5E05D operates with a 5 A CT secondary input and offers configurable trip thresholds from 5 to 50 mA, making it suitable for restricted earth fault protection applications where low-level ground leakage currents must be reliably detected while maintaining stability against external faults .
Application Scenarios
In a refinery power generation unit, a 50 MW synchronous generator operates with a resistance-grounded neutral system. The generator’s star point CT provides a 5 A secondary signal to the protection relay. However, the existing protection scheme lacks sensitive earth fault detection—a developing insulation fault in the stator winding could allow leakage current to flow undetected until it escalates into a phase-to-ground fault, causing catastrophic generator damage and an unplanned outage costing hundreds of thousands of dollars per day.
The Woodward IRI1-I5E05D addresses this gap by continuously monitoring the star point CT signal for earth fault current. When leakage current exceeds the set threshold—configurable from 5 mA upward—the relay initiates a trip signal to the generator breaker. The high sensitivity of the IRI1-I5E05D allows it to detect insulation degradation in its earliest stages, before the fault current reaches levels that would cause winding damage. The relay’s stabilizing resistor compatibility ensures it remains stable during external faults, preventing nuisance trips that could unnecessarily disconnect a healthy generator from the grid .
In transformer protection applications, the IRI1-I5E05D is commonly applied for restricted earth fault (REF) protection of the transformer star point. Its ability to discriminate between internal faults and through-faults makes it valuable for protecting large power transformers where conventional overcurrent protection may lack sufficient sensitivity .
