SEL-787

The SEL-787 is a versatile transformer protection relay engineered to deliver high-speed differential protection for two-winding and three-winding transformers. It incorporates advanced CT compensation, harmonic restraint, and adaptive filtering to ensure reliable fault detection under challenging system conditions. Beyond protection, it includes extensive monitoring, thermal modeling, and data recording functions that improve transformer reliability and asset management. The relay supports multiple I/O options, IEC 61850 communications, and customizable logic for automation. The SEL-787 is suitable for utilities seeking dependable transformer protection that integrates seamlessly with SCADA and digital substation architectures. Rugged construction ensures dependable performance in harsh industrial and substation environments.

Key Features

• Transformer differential protection

• Thermal and overcurrent protection

• Harmonic restraint (2nd/5th)

• IEC 61850, DNP3, Modbus

• Bayesian CT compensation

• Event reports, SER, and oscillography

Applications

• Distribution and sub-transmission transformers

• Two- or three-winding transformer protection

• OLTC monitoring and alarming

• Industrial plant transformer protection

Keywords

SEL-787, transformer differential relay, SEL protection relay, IEC 61850 transformer relay