The SEL-387E Current Differential and Voltage Relay provides protection to two- or three-winding power transformers. Voltage inputs for power metering, overexcitation protection, and over-/underfrequency load shedding provide versatile solutions for power apparatus protection. Automation features reduce total project construction and operation costs through elimination of traditional external control switches, meters, and indicating lamps.
Three-Winding Current Differential Protection—Protect two- to three-winding power transformers 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.
Overexcitation Protection—Detect overexcitation conditions to prevent overheating and damage in the protected apparatus with the volts-per-hertz elements. Choose definite-time elements, multiple curves, and custom programmable curves for alarm and tripping applications.
Overcurrent Protection—Each three-phase current input terminal has a total of 11 overcurrent elements, 9 of which are torque-controllable, providing comprehensive overcurrent protection on each winding input. For backup overcurrent protection in ring-bus or breaker-and-a-half configurations, two combined overcurrent elements operate on the sum of the currents from Windings 1 and 2. The combined currents from two separate breaker CTs emulate the current as if from a single bushing CT applied on the transformer.
Restricted Earth Fault (REF) Protection—The REF function compares the directions of neutral current and winding residual current for sensitive ground fault detection in grounded–wye or autotransformer–connected windings.
Two- and Three-Winding Current Differential Protection
The SEL-387E offers 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 three 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. The combined overcurrent feature sums current from two inputs 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.
Overexcitation (V/Hz) Protection
Volts-per-hertz elements detect overexcitation conditions in the protected apparatus. Choose from multiple curves (including user-defined) and definite-time elements for alarm and tripping applications.
There are six available frequency elements. The user sets the desired number of frequency elements.
Restricted Earth Fault
REF logic provides sensitive protection of grounded wye windings.
Built-In Web Server
Access basic relay information on a standard Ethernet network with a built-in web server. View relay status, Sequential Events Recorder (SER) information, metering information, and settings through easy access within a local network. Web server access requires a relay password and is limited to read-only viewing of information.
SELogic control equations with SELogic variables, timers, latch bits, and remote control elements are used for customizing advanced protection and control schemes. Local programmable control elements and programmable text display points provide an advanced local operator interface.
Metering and Reporting
Oscillographic event reports (up to seven 60-cycle reports), Sequential Events Recorder (SER) reporting, and accurate three-phase power metering eliminate or reduce external recorder and metering requirements. Station battery monitor and circuit breaker contact wear monitor provide important data for Reliability Centered Maintenance (RCM) programs.
EIA-232 and EIA-485 serial ports provide local/remote access and system integration. Download event reports using the optional Ethernet port. Quickly move information with the IEC 61850 protocol, which includes a Select-Before-Operate function for added operational security. Increase communications dependability with dual failover Ethernet.
acSELerator QuickSet SEL-5030 Software
Develop relay settings offline, program SELogic control equations, and analyze post-fault event reports.
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