Basler BE1‑81 Underfrequency Relay

The Basler BE1‑81 is a solid‑state underfrequency relay designed to protect power systems from frequency decay. This model, identified by configuration BE1‑81‑T1E‑E1C‑A0N1F and part number 9106400, provides precise monitoring and trip functions to initiate load shedding or generator tripping when frequency falls below a set threshold. It is essential for maintaining system stability in utility, industrial, and co‑generation applications.

Key Features

The relay features adjustable frequency pickup setpoints and independent time delays for multiple stages. It includes high‑accuracy frequency sensing with minimal drift over temperature. The unit provides both instantaneous and time‑delayed output contacts. Front‑panel LEDs and a target indicator display status and trip events. The relay is housed in a rugged draw‑out case for ease of maintenance.

Technical Specifications

Input voltage: 120 or 240 VAC, 50/60 Hz. Frequency measuring range: 40‑65 Hz. Underfrequency trip settings: 45‑60 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. When the frequency drops below the setpoint, the corresponding timer starts. If the frequency remains below the threshold for the entire delay, the output relay energizes. Multiple stages can be configured for sequential load shedding based on severity.

Applications

This relay is used in generator sets, utility substations, and industrial plants to prevent system collapse during frequency decay. It is critical for underfrequency load shedding schemes and to protect turbines and generators from damage.

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 BE1‑81 underfrequency relay provides dependable frequency protection with flexible staging, making it a key component for system stability.