Basler BE1-81 O/U Digital Frequency Relay
The Basler BE1-81 O/U is a digital frequency relay designed to protect generators, motors, and utility systems from abnormal frequency conditions. This relay provides both overfrequency (81O) and underfrequency (81U) protection with independently adjustable pickup levels and time delays. It is essential for preventing damage to turbine blades, generators, and driven equipment when system frequency deviates from nominal values.
The relay features microprocessor-based design with high accuracy (±0.02 Hz) and thermal stability. It includes a front-panel display and keypad for local readings and settings, and supports Modbus communication for remote monitoring. The BE1-81 O/U is housed in a rugged metal enclosure suitable for panel mounting in substations and generator control rooms.
Technical Specifications
Model: BE1-81 O/U
Protection functions: Overfrequency (81O), Underfrequency (81U)
Frequency sensing: 50/60 Hz (selectable)
Overfrequency pickup: 50-65 Hz (adjustable)
Underfrequency pickup: 45-60 Hz (adjustable)
Time delay: 0.1-30 seconds (definite time, programmable)
Accuracy: ±0.02 Hz
Input voltage: 120/240 V AC (from PT)
Output contacts: 2 form C (one for over, one for under)
Communication: Modbus RTU (RS-485)
Power supply: 24-240 V AC/DC (universal)
Operating temperature: -40°C to +70°C
Certifications: CE, UL, RoHS
Functional Features
Independent over/under settings: Each function has its own pickup and time delay.
Frequency rate-of-change (df/dt) detection: Optional feature for rapid frequency deviations.
Digital filtering: Ensures accurate measurement even with distorted waveforms.
Diagnostic LEDs: Status indicators for power, pickup, and trip.
Event recording: Stores last 10 trip events with time stamp.
Typical Applications
Generator protection: Tripping or load shedding during frequency excursions.
Utility intertie: Preventing islanding and damage to parallel systems.
Motor protection: Avoiding overload and overheating due to frequency variations.
Underfrequency load shedding: Automatically disconnecting non-critical loads.
Installation and Configuration
Mount the relay on a panel using the provided brackets. Connect the voltage input from the PT, the power supply, and the output contacts. Configure the nominal frequency, overfrequency pickup, underfrequency pickup, and associated time delays using the front-panel keypad. The relay can be tested using a frequency generator to verify correct operation.
Compliance
Meets IEEE C37.90 and IEC 60255 standards, CE and UL approved, RoHS compliant.
Conclusion
The Basler BE1-81 O/U provides reliable, accurate frequency protection for critical power system assets, with flexible settings and communication capabilities.
