Basler Electric BE1-50/51B-107 – Advanced Overcurrent Protection Relay

The Basler Electric BE1-50/51B-107 (catalogue reference 9 2520 00 107, model T214016) is a solid‑state overcurrent relay that integrates both instantaneous (50) and time‑overcurrent (51B) functions in a single compact unit. Designed for primary and backup protection of feeders, transformers, and distribution lines, this relay offers high accuracy, fast response, and flexible settings to accommodate a wide range of system configurations.

Functional Overview

The instantaneous element provides high‑speed tripping for severe faults, while the time‑overcurrent element operates with an inverse‑time characteristic that coordinates with downstream protective devices. The relay measures phase currents via standard current transformers and compares them against user‑adjustable pickup thresholds. When the current exceeds the set level, the timer initiates a trip output after a delay determined by the time dial setting. This dual‑element design ensures both rapid fault clearance and selective coordination.

• Phase current inputs: 1 A or 5 A nominal (field‑selectable)

• Instantaneous pickup range: 2–40 A (in 0.1 A steps)

• Time‑overcurrent pickup: 0.5–12 A (adjustable)

• Time dial: 0–10 (continuous adjustment)

• Curve types: inverse, very inverse, and definite time

• Output contacts: two Form‑C relays, rated 5 A at 250 V AC

• Power supply: 120/240 V AC or 125/250 V DC

• Operating temperature: –20 °C to +65 °C

Application Scenarios

This relay is commonly deployed in medium‑voltage switchgear, motor control centres, and generator protection panels. Its instantaneous element is ideal for clearing close‑in faults that could cause severe equipment damage, while the time‑overcurrent element handles less severe overloads. The BE1-50/51B-107 is also used in transformer differential protection schemes as a backup overcurrent stage, ensuring that transformer faults are cleared if the main differential relay fails.

Installation and Configuration

The relay is housed in a standard draw‑out case with a transparent cover for easy viewing of target indicators and setting dials. Front‑panel controls allow quick adjustment of pickup values and time dial without special tools. A test jack facilitates secondary injection testing to verify calibration and timing. The relay includes a manual reset pushbutton and an electrical reset function for remote operation.

Reliability and Standards Compliance

Built with Basler’s proven analog and digital hybrid technology, the BE1-50/51B-107 offers excellent surge withstand capability and thermal stability. It meets or exceeds ANSI/IEEE C37.90 and IEC 60255 standards for protective relays. The solid‑state construction eliminates moving parts, reducing maintenance and extending service life. This relay is a trusted choice for utilities and industrial plants seeking dependable overcurrent protection.

In summary, the Basler Electric BE1-50/51B-107 provides a cost‑effective, reliable solution for overcurrent protection, combining instantaneous and time‑overcurrent functions in a robust, field‑adjustable package.