Basler BE1-87T Transformer Differential Relay

The Basler BE1-87T (style E1EA1KD0S0F) is a solid‑state differential relay specifically designed for protection of power transformers. This relay provides fast and reliable protection against internal transformer faults such as turn‑to‑turn faults, winding short circuits, and core faults, ensuring rapid clearing and minimizing damage.

The BE1-87T employs percentage differential protection with harmonic restraint to prevent maloperation during transformer energization and overexcitation. It features adjustable pickup, slope, and harmonic restraint settings, allowing precise coordination with transformer characteristics. The relay is housed in a rugged enclosure suitable for panel mounting in substations and industrial control rooms.

Technical Specifications

• Model: BE1-87T (E1EA1KD0S0F)

• Protection type: Percentage differential

• Current sensing: 1/5 A CT inputs (primary and secondary)

• Pickup range: 0.1‑2.0 A (adjustable)

• Slope setting: 0‑40% (adjustable)

• Harmonic restraint: Second harmonic (15‑30%) and fifth harmonic (optional)

• Response time: < 20 ms (typical)

• Output contacts: 2 form C (trip and alarm)

• Power supply: 24‑240 V AC/DC (universal)

• LED indicators: Power, differential pickup, trip

• Operating temperature: -40°C to +70°C

• Certifications: CE, UL, RoHS

Functional Features

• Percentage differential protection: Provides sensitive fault detection while maintaining stability for external faults.

• Harmonic restraint: Blocks tripping during transformer inrush and overexcitation.

• Fast operation: Trip times less than one cycle.

• Adjustable settings: Pickup, slope, and harmonic restraint can be field‑adjusted.

• Target indicators: Seal‑in flags for trip indication.

Typical Applications

• Power transformers: Protection of two‑winding and three‑winding transformers.

• Generator step‑up transformers: Protection for unit‑connected generators.

• Industrial transformers: Protection for large furnace and rectifier transformers.

Installation and Configuration

Mount the relay on a panel. Connect CT inputs from both sides of the transformer, power supply, and output contacts. Configure the pickup, slope, and harmonic restraint settings using the front‑panel controls.

Compliance

Complies with IEEE C37.91, IEC 60255, CE and UL approved, RoHS compliant.

Conclusion

The Basler BE1-87T provides reliable, high‑speed differential protection for power transformers, ensuring rapid fault clearing and preventing costly damage.