Two-, Three-, and Four-Winding Current Differential, Overcurrent, Voltage, and Breaker Failure Protection
Apply two-, three-, or four-winding dual-slope differential protection with phase, negative-sequence, residual, and neutral overcurrent elements for backup protection. You can set elements in SEL-787-3E/-3S models for voltage- and frequency-based protection. Breaker failure protection for as many as four three-pole breakers comes standard.

Security and Dependability
Provide maximum security during external faults and transformer magnetizing inrush conditions. The SEL-787 can detect internal faults quickly during energization or normal operating conditions by using combined harmonic-blocking and harmonic-restraint differential elements.

Transformer Monitoring
Set the SEL-787 to record and accumulate through-fault duty for use in SELogic control equations or manual monitoring. In addition, you can monitor ambient, LTC tank, and transformer oil temperatures with optional 4–20 mA analog inputs or RTD thermal inputs to extend the life of your transformer.

Operator Control
Use eight programmable front-panel pushbuttons, each with two programmable, tricolored LEDs, for a wide variety of applications, including easy trip-and-close control and status indications for a breaker. You can implement local and remote operator control schemes with 32 local and 32 remote control bits.

Optional Touchscreen Display
The easy-to-use touchscreen interface provides a one-line mimic display for bay control and monitoring. View metered quantities, phasor diagrams, relay settings, event summaries, target statuses, Sequential Events Recorder (SER) data, and more. Extensive testing shows that the robust capacitive touchscreen display meets or exceeds industry standards as well as SEL quality and reliability requirements.

IEC 61850 Test Mode
Test 61850 system components in energized substations without fear of operating control output contacts.

Webserver Access
The built-in webserver enables secure, remote access to the relay with password protection. Download status reports or view metering and relay information remotely. This helps minimize trips to the relay location, which saves time and money.

Accelerate Firmware Downloads
Simplify maintenance by downloading relay firmware via the Ethernet port. This also enables you to access and update all of your network relays simultaneously.

Metering and Reporting
Eliminate separately mounted metering devices with built-in metering functions. You can analyze SER reports and oscillographic event reports in COMTRADE and CEV formats to analyze post-fault diagnostics and for rapid commissioning and testing. You can retrieve COMTRADE files via Ethernet FTP or IEC 61850 MMS, and the unsolicited SER protocol allows station-wide collection of binary SER messages. SEL-787 metered quantities include harmonics, power, frequency, and energy; phase voltages and currents; neutral currents; sequence voltages and currents; and maximum/minimum logging of selected quantities.

Rugged Design
Trust the industry’s widest ambient operating temperature range, –40° to +85°C (–40° to +185°F). The SEL-787 withstands vibration, electrical surges, fast transients, and extreme temperatures, meeting stringent industry standards. A conformal-coating option for the printed circuit boards provides an additional barrier to airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture. In addition, the SEL-787 is ATEX- and Underwriters Laboratories (UL) Class I, Division 2-certified for use in hazardous and potentially explosive environments.