Basler BE1‑81O Under / Over Frequency Relay

The Basler BE1‑81O is a solid‑state frequency relay that provides both underfrequency and overfrequency protection in a single unit. This model, with configuration BE1‑81O/UT3EE1KA7N1F (also referenced as BE181OUT3EE1KA7N1F), offers comprehensive monitoring and tripping functions to protect generators, turbines, and power systems from abnormal frequency excursions. It is essential for ensuring system stability and equipment safety.

Key Features

The relay features independent underfrequency and overfrequency elements with adjustable pickup setpoints and time delays. It includes high‑accuracy frequency sensing with minimal drift. The unit provides multiple output contacts for stage‑based tripping. Front‑panel LEDs and a target indicator display status and trip events. The relay is housed in a rugged draw‑out case.

Technical Specifications

Input voltage: 120 or 240 VAC, 50/60 Hz. Frequency measuring range: 40‑65 Hz. Underfrequency settings: 45‑60 Hz (adjustable). Overfrequency settings: 50‑65 Hz (adjustable). Time delay range: 0.1‑10 seconds per stage. Trip accuracy: ±0.05 Hz. Output contact rating: 5 A at 250 VAC resistive. Operating temperature: -20°C to +55°C. Auxiliary supply: 120/240 VAC or 48/125 VDC.

Operating Principles

The relay continuously measures the input frequency using digital counting techniques. If the frequency falls below the underfrequency setpoint or rises above the overfrequency setpoint, the corresponding timer starts. If the frequency remains outside the limits for the set delay, the output relay energizes. Multiple stages can be configured for sequential protection.

Applications

This relay is used in generator sets, utility substations, and industrial plants to protect against both low and high frequency conditions. It is critical for load shedding, generator tripping, and turbine protection.

Installation and Configuration

Mount the relay in a standard panel cutout. Connect the voltage inputs and output circuits. Adjust frequency setpoints and time delays using front‑panel potentiometers. A calibration check with a precision frequency source is recommended.

Maintenance and Reliability

Solid‑state construction ensures high reliability. Periodic testing verifies trip accuracy. Routine inspection of connections is sufficient.

Conclusion

The Basler BE1‑81O under/over frequency relay provides comprehensive frequency protection with flexible settings, ensuring safe and stable operation of power systems.