Basler BE3‑25 Time Overcurrent Relay

The Basler BE3‑25 is a solid‑state time overcurrent relay designed for protection of distribution feeders, transformers, and motors. This model, with configuration BE3‑25‑1S1N4 (also referenced as BE3251S1N4), provides reliable detection of phase and ground faults with adjustable time‑current characteristics. It is part of Basler Electric's BE3 series, known for compact design and high accuracy.

Key Features

The relay features a wide pickup current range, selectable inverse‑time and definite‑time curves, and a high reset ratio. It includes a target indicator for fault identification and test points for calibration. The relay provides both instantaneous and time‑delayed trip outputs. Its solid‑state design ensures long‑term stability and immunity to vibration.

Technical Specifications

CT secondary rating: 5 A or 1 A. Pickup range: 0.5‑20 A (for 5 A CT). Time dial: adjustable from 0 to 10. Time‑current curves: IEC or IEEE inverse, very inverse, extremely inverse, and definite time. Instantaneous element: adjustable from 2‑40 times pickup. Output contact rating: 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 the current from CTs. When the current exceeds the pickup setting, the timing circuit initiates. The time delay is determined by the selected curve and time dial setting. If the fault persists, the output relay trips the breaker. The instantaneous element operates without intentional delay for high‑current faults.

Applications

This relay is used in utility substations, industrial power systems, and commercial buildings for feeder and motor protection.

Installation and Configuration

Mount the relay in a standard panel cutout. Connect the CT leads, auxiliary power, and trip circuits. Set the pickup, time dial, and instantaneous pickup using the front‑panel controls. A secondary injection test is recommended.

Maintenance and Reliability

Routine maintenance includes visual inspection and periodic calibration checks. The solid‑state design provides high reliability with no moving parts.

Conclusion

The Basler BE3‑25 time overcurrent relay offers dependable overcurrent protection with flexible settings, making it a versatile choice for modern power distribution systems.