Technical Parameters
Parameter Specification
Manufacturer ABB
Model / Type PR121/P‑LI
Product Category Electronic Overcurrent Trip Unit
Application Protection for ABB low-voltage air circuit breakers
Protection Functions • L – Long-time overload protection
• I – Instantaneous short-circuit protection
Adjustability Adjustable pickup levels and time settings for L and I
Trip Output Drives breaker trip coil to open the breaker under fault conditions
User Interface Front-panel dials, switches, or software configuration depending on implementation
Indication LED or display indicators for protection status and trip cause
Auxiliary / Control Supply AC or DC supply to power electronics and indicators
Poles Protected 3-phase (L1, L2, L3)
Rated Frequency 50 / 60 Hz
Mounting Installed within the breaker’s protection slot/interface
Standards Compliance IEC low-voltage overcurrent protection standards
Typical Supported Breaker Ratings Mid- to high-current frames, depending on breaker model
Optional Features Remote signaling, communication via breaker interface (if supported)
The ABB PR121/P‑LI is an electronic overcurrent protection trip unit designed for integration into compatible ABB low-voltage air circuit breakers. It provides adjustable and coordinated protection for three-phase distribution systems, safeguarding against overloads and instantaneous short-circuit faults. The trip unit is suitable for industrial, commercial, and utility applications, ensuring reliable current protection and system safety.