Basler BE1‑Z2 Directional Overcurrent Relay

The Basler BE1‑Z2 is a solid‑state directional overcurrent relay designed for phase fault protection in distribution and sub‑transmission systems. This model, identified by configuration BE1‑Z2JA0N2F, combines overcurrent detection with directional sensing to discriminate between faults in the forward and reverse directions. It is essential for protecting radial and looped networks where fault current can flow in both directions.

Key Features

The relay features independent overcurrent pickup and time delay adjustments, as well as directional element settings. It includes selectable time‑current curves (inverse, very inverse, extremely inverse, and definite time). The directional element uses voltage polarization for reliable operation. The unit provides a target indicator, test points, and LED status lights. It is housed in a compact draw‑out case for easy maintenance.

Technical Specifications

CT secondary: 5 A or 1 A. Pickup range: 0.5‑20 A (adjustable). Time dial: 0‑10. Time‑current curves: IEC and IEEE standard curves. Directional characteristic: forward or reverse with adjustable MTA (maximum torque angle). Output contacts: 2 form‑C rated at 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 measures both phase current and phase voltage (or uses memory voltage for close‑in faults). The directional element compares the phase angle between current and voltage to determine fault direction. If the fault is in the forward direction and the current exceeds the pickup setting, the timing circuit initiates. If the fault persists for the set time delay, the output relay trips the breaker. The relay provides selective coordination with upstream and downstream devices.

Applications

This relay is used in utility distribution feeders, industrial power systems, and generator protection schemes. It is ideal for applications where fault current direction is critical, such as parallel feeders, ring networks, and co‑generation interconnections.

Installation and Configuration

Mount the relay in a standard panel cutout. Connect CT leads, PT voltage inputs, auxiliary power, and trip circuits. Set the pickup current, time dial, directional angle, and characteristic curve using front‑panel controls. A secondary injection test is recommended to verify both directional and overcurrent operations.

Maintenance and Reliability

Solid‑state design provides high reliability. Periodic testing and calibration are recommended. Routine visual inspection of connections is sufficient.

Conclusion

The Basler BE1‑Z2 directional overcurrent relay offers reliable and selective phase fault protection with directional discrimination, making it a versatile solution for modern power distribution networks.