Current Differential Relay

The SEL-587 Current Differential/Overcurrent Relay provides protection for any two-input apparatus, such as transformers, motors, generators, and reactors. Apply it for differential and overcurrent protection and use event reports for quick post-event analysis.

Applications

Two-Winding Differential Protection—Provide current differential protection with programmable single- or dual-slope percentage restraint for two-winding transformers, reactors, generators, large motors, and other two-terminal apparatus. Automatic tap calculations simplify settings.

Comprehensive Overcurrent Protection—Apply individual winding phase, residual, and negative-sequence overcurrent elements to expand beyond basic transformer protection. In addition, backup overcurrent protection provides high-speed operation, even with severe CT saturation, using the SEL Adaptive Overcurrent Element.

Differential Element Supervision—Use second- and fourth-harmonic blocking or restraint along with dc blocking to supervise differential elements during transformer energization conditions. The calculated fifth harmonic can be used to supervise differential element operations during transformer overexcitation events.