Basler BE1‑50/51B‑107 Combination Overcurrent Relay

The Basler BE1‑50/51B‑107 is a solid‑state relay that combines instantaneous (50) and time‑overcurrent (51B) protection in a single unit. This model, referenced as BE15051B107, provides comprehensive phase and ground fault protection for distribution feeders, transformers, and motors. It offers adjustable pickup settings and time‑current characteristics, making it a versatile solution for utility and industrial power systems.

Key Features

The relay features independent instantaneous and time‑overcurrent elements with separate pickup and time dial adjustments. It includes a target indicator for fault identification and test points for calibration. The relay provides both normally open and normally closed output contacts. Its solid‑state design ensures high accuracy and reliability.

Technical Specifications

CT secondary: 5 A or 1 A. Instantaneous pickup: 1‑40 A (adjustable). Time overcurrent pickup: 0.5‑20 A. Time dial: 0‑10. Time‑current curves: IEC or IEEE inverse, very inverse, extremely inverse, definite time. Output contacts: 2 form‑C rated 5 A at 250 VAC. Operating temperature: -20°C to +55°C. Auxiliary supply: 120/240 VAC or 48/125 VDC.

Operating Principles

The relay continuously monitors current from CTs. If the current exceeds the instantaneous pickup, the relay trips without intentional delay. For lower overcurrents, the time‑overcurrent element initiates timing based on the selected curve and time dial. If the fault persists, the relay trips after the calculated time delay. This combination provides fast protection for high faults and coordinated timing for lower faults.

Applications

This relay is used for feeder protection, transformer protection, and motor protection in distribution networks. It is suitable for utility substations, industrial plants, and commercial buildings. The combination function reduces panel space and simplifies wiring.

Installation and Configuration

Mount the relay in a standard panel cutout. Connect CT leads, auxiliary power, and trip circuits. Set the instantaneous pickup, time overcurrent pickup, and time dial using front‑panel knobs. Perform a secondary injection test to verify both instantaneous and time characteristics.

Maintenance and Reliability

Routine inspection and periodic calibration are recommended. The solid‑state design ensures long‑term reliability with no moving parts.

Conclusion

The Basler BE1‑50/51B‑107 combination overcurrent relay offers integrated instantaneous and time‑overcurrent protection, providing flexible and reliable protection for critical power system components.