Basler Electric BE1‑50/51B‑207 – Combined Overcurrent Relay

The Basler Electric BE1‑50/51B‑207 is a microprocessor‑based overcurrent relay that integrates both instantaneous (50) and time‑overcurrent (51) protection functions in a single compact unit. Designed for feeder, motor, and transformer protection in distribution and industrial systems, this relay offers high accuracy, wide setting ranges, and robust construction.

Protection Functions

The instantaneous element (50) provides high‑speed tripping for severe short‑circuit faults, with a pickup current range of 2 to 80 times the nominal CT secondary current (1 A or 5 A). The time‑overcurrent element (51) uses an inverse‑time characteristic (IEC or IEEE curves) with pickup settings from 0.5 to 4 times the nominal current, and time dial settings from 0.1 to 10. The combination ensures coordinated protection with downstream devices.

Current Sensing and Accuracy

Inputs are from standard CTs with 1 A or 5 A secondary ratings. The relay has a measurement accuracy of ±2% of setting for overcurrent and ±3% for time delay. It features a wide frequency tolerance of 45‑65 Hz, suitable for various grid conditions. The unit includes a built‑in current unbalance detection for motor protection.

Setting and Configuration

Settings are entered via a front‑panel keypad and LCD display, or remotely via communication. The BE1‑50/51B‑207 stores up to two setting groups for dual‑mode operation (e.g., normal and emergency). A password‑protected lock prevents unauthorized changes. The relay also provides a test mode for verification without tripping.

Output Contacts and Indications

Two independent output relays are provided: one for trip (normally open) and one for alarm (changeover). Additionally, a target indicator with manual reset flags the operation. LED indicators show power, pickup, and trip status. The relay can be wired for latching or non‑latching tripping.

Communication and Integration

An optional RS‑485 port supports Modbus RTU, allowing the relay to communicate with SCADA systems for remote monitoring and setting adjustments. The unit also has an IRIG‑B input for time synchronization if required.

Mechanical and Environmental

The relay is housed in a rugged DIN‑rail or panel‑mount enclosure, with dimensions suitable for standard switchgear. It operates from -40 °C to +85 °C and is rated IP40. The auxiliary power supply is 24‑250 V AC/DC, ensuring compatibility with control battery systems. The relay complies with IEC 60255 and ANSI C37.90 standards.

Typical Applications

This relay is commonly used for primary and backup overcurrent protection on medium‑voltage feeders, transformer incomers, and large motors. Its combined instantaneous and time characteristics provide effective fault discrimination and reduced damage.

Maintenance and Life

Solid‑state design ensures long life with no moving parts. Periodic testing of pickup and timing accuracy is recommended. The relay features self‑diagnostics that detect internal faults and output a warning.

In conclusion, the Basler Electric BE1‑50/51B‑207 offers dependable, flexible, and accurate overcurrent protection, making it a valuable asset for any power protection scheme.