Transformer Protection Relay

Protect and monitor most two-, three-, and four-winding transformers with the versatile SEL-787 platform. It provides advanced automation and flexibility, asset management data, and easy retrofitting of most electromechanical relays. The 5-inch, 800 × 480 color touchscreen display option allows you to directly set, monitor, and control your system, including up to five two- or three-position disconnect switches.

The SEL-787-2E/-21/-2X models offer two-winding differential protection, and the SEL-787-3E/-3S models offer three-winding differential protection. Select the SEL-787-4X for current-based four-winding differential protection.

Applications

Multiwinding Protection—Select the SEL-787 for standard dual-slope differential protection with harmonic blocking and restraint for most two-, three-, and four-winding transformers. The SEL-787 offers as many as three independent restricted earth fault (REF) elements for sensitive ground-fault detection in grounded-wye transformers. The relay also comes with a variety of overcurrent elements for backup protection, including phase, negative-sequence, residual-ground, and neutral-ground elements. Breaker failure protection for as many as four 3-pole breakers is also standard.

Frequency Tracking—Choose the SEL-787 for generator step-up and variable-frequency applications. The relay has voltage inputs to provide volts/hertz protection with frequency tracking from 20 to 70 Hz. Over-/underfrequency and over-/undervoltage elements allow you to implement load shedding and other control schemes with the relay.

Synchronism Check/Station DC Battery Monitor—Program the VS/VBAT voltage channel in the SEL-787-3S to perform a synchronism check across a circuit breaker or to monitor dc voltage levels of the substation battery.

Through-Fault Monitoring and Protection—Measure accumulated through-fault levels with the transformer through-fault monitor. Additionally, the optional 4–20 mA or resistance temperature detector (RTD) thermal inputs can monitor ambient, load tap changer (LTC) tank, and transformer oil temperatures.

Reliable Protection in Harsh Environments—The SEL-787 operates in extreme conditions, with an operating temperature of –40° to +85°C (–40° to +185°F), and it is designed and tested to exceed applicable standards, including vibration, electromagnetic compatibility, and adverse environmental conditions. In addition, the SEL-787 is ATEX-certified and Underwriters Laboratories (UL) Class I, Division 2-certified for use in hazardous and potentially explosive environments.

Metering and Reporting—Eliminate separately mounted metering devices with the built-in metering functions. You can analyze Sequential Events Recorder (SER) reports and oscillographic event reports for rapid commissioning, testing, and post-fault diagnostics. You can also transfer event files in COMTRADE and CEV formats and transfer CID files, settings, and reports. The unsolicited SER protocol allows station-wide collection of binary SER messages.

Local/Remote Operator Controls—Employ eight programmable front-panel pushbuttons, each with two programmable tricolor LEDs, for a wide variety of uses, including easy trip/close control and status indication for all the breakers. With the operator control interface pushbuttons, you can easily implement local and remote operator control schemes using 32 local and 32 remote control bits. SELogic control equations and slide-in, configurable front-panel labels allow you to change the function and identification of target LEDs and operator control pushbuttons and LEDs.

Integration and Automation—Select from a wide array of communications protocols and media to support all your integration and automation solutions. You can quickly integrate the SEL-787 into serial- or Ethernet-based communications schemes with IEC 61850 Edition 2, IEC 60870-5-103, the IEC 62439 Parallel Redundancy Protocol (PRP), EtherNet/IP, the IEEE 1588 Precision Time Protocol (PTP), Mirrored Bits communications, Modbus, DNP3, and other protocols. You can choose English or Spanish front panels, with optional Spanish language support in the PC software, ASCII ports, and HMI.