Basler Electric BE1-50/51M-109 Overcurrent Relay

The Basler Electric BE1-50/51M-109 is a solid-state overcurrent relay that provides both instantaneous (50) and time-delayed (51) overcurrent protection, with characteristics tailored for motor and generator applications. The 'M' designation indicates that the relay includes features specific to motor protection, such as thermal memory and locked-rotor detection. This relay is part of Basler's BE1 series, known for its high accuracy, reliability, and ease of coordination.

Key Features

• Instantaneous element with adjustable pickup and reset

• Time-delayed element with selectable inverse time curves (IEC or IEEE)

• Thermal memory for motor starting and repeated overloads

• Locked-rotor protection with separate setpoint

• Adjustable time dial for coordination

• High current withstand for CT saturation

• Output relay contacts for trip and alarm

• LED indicators for pickup and trip status

Technical Specifications

The relay accepts 5 A or 1 A CT secondary inputs at 50/60 Hz. Instantaneous pickup range: 2 to 80 A (for 5 A input). Time overcurrent pickup range: 0.5 to 20 A. Time dial range: 0.1 to 10. Accuracy: ±5 percent for instantaneous, ±3 percent for time-delayed. Auxiliary power: 120/240 VAC or 24 to 125 VDC. Operating temperature: -20 to +65 degrees Celsius. The relay meets ANSI C37.90 and IEC 60255 standards.

Protection Functions

The instantaneous element provides fast clearing for severe faults. The time-delayed element uses inverse-time characteristics to ensure coordination with downstream protection. Thermal memory prevents nuisance tripping during motor starting while providing protection against repeated overloads. The locked-rotor function detects abnormal current during start-up and trips before damage occurs.

Installation and Configuration

Panel mount with rear connections. Settings are made via DIP switches and potentiometers. The relay includes a target indicator that remains latched after a trip for fault analysis. Commissioning requires testing with a secondary injection test set.

Applications

Primarily used for protection of medium-voltage motors, but also applicable for generator backup, feeder protection, and transformer protection. The BE1-50/51M-109 is widely employed in industrial plants, pumping stations, and HVAC systems.

Reliability and Maintenance

Solid-state construction ensures long-term stability. The relay is self-supervising and includes a watchdog circuit. Routine maintenance is limited to periodic functional tests.

Conclusion

Basler Electric BE1-50/51M-109 overcurrent relay delivers comprehensive motor and generator overcurrent protection with both instantaneous and time-delayed elements. Its special motor-oriented features and robust design make it a reliable choice for critical industrial applications.