Omron K2WR-R-S5 Reverse Power Relay | 110/220V 5A Marine Grade

Omron K2WR-R-S5: The Gold Standard in Marine Power Protection

The Omron K2WR-R-S5 is a specialized induction-type relay used primarily in parallel generator operations. When a prime mover (like a diesel engine or steam turbine) fails or loses power, the generator can begin acting as a motor, drawing power from the busbar. This “motoring” effect can cause catastrophic mechanical damage. The K2WR-R-S5 detects this reversal of power flow with surgical precision, tripping the circuit breaker to isolate the fault before damage occurs.

Specifications

Engineer Expert’s Guide

1. The 10% Rule: In marine applications, we typically set the reverse power trip at roughly 5% to 10% of the generator’s rated capacity. Setting it too low (too sensitive) leads to blackout risks during heavy sea states when the governor is hunting.
2. Phase Sequence Awareness: The most common error I see during installation is incorrect CT (Current Transformer) polarity. If your K2WR-R-S5 trips immediately upon synchronization, check your phase sequence and CT orientation. A reversed CT will make the relay “think” the generator is motoring when it’s actually exporting.
3. Maintenance Testing: During your annual PMS (Planned Maintenance System), don’t just look at the relay. Use a secondary injection test set to verify the trip timing. Induction discs can accumulate dust or “sticky” spots over a decade of service; a quick puff of dry air and a functional test ensure it’s ready for a real emergency.