The SEL-387A Current Differential and Overcurrent Relay offers restrained and unrestrained differential protection for two terminals. Second-, fourth-, and fifth-harmonic elements, augmented by the dc element, provide security during transformer energization and overexcitation conditions in a user-defined choice of either harmonic restraint or harmonic blocking. Overcurrent elements provide backup protection that contributes to the versatility of the SEL-387A.
Two-, Three-, and Four-Winding Current Differential Protection
Sensitive current differential protection with programmable single- or dual-slope percentage restraint, supervised by a choice of second- and fourth-harmonic blocking or restraint elements, plus fifth-harmonic and dc blocking elements for secure protection of up to four windings. Phase current harmonic blocking is set for either common or independent winding basis. Unrestrained high-set differential elements provide fast operation for high-magnitude internal faults. "Around the clock" phase angle compensation settings and automatic tap calculations simplify settings.
Individual Winding Overcurrent Protection
Torque-controllable overcurrent elements, including one instantaneous, one definite-time, and one inverse-time element each for phase, negative-sequence, and residual ground currents, provide comprehensive overcurrent protection on each winding input. Combined current feature sums current from two CTs for ring-bus and breaker-and-a-half overcurrent applications.
Through-Fault Recording and Monitoring
Through-fault duty is recorded and accumulated for use in SELogic control equations or manual monitoring.
Protection and Control Logic
Restricted Earth Fault (REF) logic for sensitive grounded-wye winding ground fault protection. SELogic Control Equations with SELogic variables, timers, latch bits, and remote control elements for customizing advanced protection and control schemes. Local programmable control elements and programmable text display points for advanced local operator interface.
Metering and Reporting
Oscillographic event reports (up to seven 60-cycle reports), Sequential Events Recorder (SER) reporting, and accurate metering eliminate or reduce external recorder and metering requirements. Station battery voltage monitor and circuit breaker contact wear monitor provide important data for Reliability Centered Maintenance (RCM) programs.
acSELerator QuickSet SEL-5030 Software
Develop relay settings off-line, program SELogic control equations, and analyze post-fault event reports.