Application Scenarios
At a hydroelectric power station in Canada, the generator protection system relied on legacy electromechanical relays for breaker trip initiation. During a routine audit, engineers discovered contact welding in several units after a close-onto-fault event. They replaced all critical logic relays with ABB 07KR51 220VDC modules mounted on test bases. The new relays provided:
Clear mechanical flag indication when operated
Gold-flashed contacts capable of reliably switching low-energy DC tripping coils
Plug-in design that allowed live testing during maintenance windows
Over five years of operation—including multiple fault-clearing events—the 07KR51 units showed zero failures, significantly improving system dependability and reducing outage risk during generator synchronization sequences.
Key Parameters
Technical Principles and Innovative Values
Innovation Point 1: Dual-Purpose Contacts – The 07KR51 combines high-power switching capability (for breaker trip coils) with ultra-reliable low-level signal handling (for PLC inputs or SCADA status)—eliminating the need for separate signal and power relays.
Innovation Point 2: Fail-Safe Visual Indication – A bright red mechanical flag pops up when the relay operates and stays latched until manually reset. This provides unambiguous fault indication during post-event analysis—critical in black-start or forensic investigations.
Innovation Point 3: Hot-Test Architecture – When installed on a test base like 07KP91. the relay can be fully isolated, jumpered, or simulated without de-energizing the control circuit. This enables functional testing of protection logic during normal operation—complying with NERC PRC-005 requirements.
Typical Industry Applications
Power Generation: Turbine emergency stop logic, generator breaker interlocks, excitation dropout alarms
Transmission Substations: Breaker failure initiation, auto-reclose blocking, bus transfer schemes
Oil & Gas: ESD (Emergency Shutdown) signal distribution, compressor trip sequencing
Rail & Traction: Feeder protection signaling, DC switchgear control
Industrial Plants: Motor control interlocks, boiler fuel cutoff circuits, fire suppression triggers
Related Product Combination Solutions
07KP91: Test plug base with shorting links and test terminals for 07KR51
07KR50: Similar relay with 4 CO contacts (lower density variant)
07KR52: Version with 6 CO + 2 NO contacts for specialized logic
5SHX1440L0001: ABB AC 800PEC I/O module often used alongside 07KR51 in hybrid hardwired/digital protection
REF615 / REL670: ABB protection relays whose output contacts frequently drive 07KR51 coils for logic expansion
PM864A: AC 800M controller that may receive status feedback from 07KR51 auxiliary contacts
Terminal Blocks (TB840 series): For secure wiring of DC control and signal circuits feeding the 07KR51
Installation, Maintenance & Lifecycle Support
Installation requires mounting the 07KR51 onto a compatible test base (e.g., 07KP91) pre-wired into the control panel. The coil is connected to the 220V DC control supply, while contacts interface with trip coils, alarms, or upstream logic. Ensure polarity is observed if the coil includes a suppressor diode (standard in most ABB DC relays).
Maintenance is minimal but highly effective:
Use the front test button to simulate operation during commissioning
After a trip event, inspect the mechanical flag and manually reset it
Periodically check contact resistance (<50 mΩ) using a milliohm meter
Replace every 10–15 years in high-duty-cycle applications as part of obsolescence management
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