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Transformer Protection Relay

Protect and monitor most transformer applications with the powerful SEL-487E Transformer Protection Relay. Apply up to 5 three-phase restraint inputs, three independent restricted earth fault (REF) protection elements, and 2 three-phase voltage inputs, all with synchrophasors. Limit transformer damage by responding to internal fault conditions in less than 1.5 cycles. Avoid catastrophic transformer failure by detecting turn-to-turn faults involving as little as 2 percent of the total winding. Minimize commissioning time and eliminate costly errors with software that recommends matrix compensation settings. Through-fault and thermal monitoring allow you to track transformer wear and schedule maintenance as necessary. Breaker wear monitoring reduces inefficient and costly breaker maintenance, saving time and money. Optional Time-Domain Link (TiDL) technology transforms the way you modernize your substation.

Starting At

6,750 USD

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Multiwinding Protection—Configure the SEL-487E for transformer differential protection in transformer applications using up to five restraint currents. This includes single transformers with tertiary windings. Use three independent REF elements for protection of grounded-wye windings.

Sensitive Turn-to-Turn Fault Detection—Avoid catastrophic transformer failure. Detect turn-to-turn faults involving as little as two percent of the total winding with the patented negative-sequence differential element.

High-Speed, Adaptive Differential Protection—Implement a two-stage slope that automatically adapts to internal or external fault conditions, even with CT saturation and heavily distorted waveforms, for fast, sensitive, dependable, and secure differential protection. The adaptive differential element responds to internal fault conditions in less than 1.5 cycles.

Diverse Transformer Applications—Protect large transformers with breaker-and-a-half high- and low-side connections. Also, configure for a typical two-winding transformer application, and use the remaining three-phase current inputs for feeder backup protection.

Generator Step-Up Protection—Protect generator step-up (GSU) transformers, and apply the built-in thermal elements (requires the SEL-2600 RTD Module) for monitoring generator and transformer winding temperatures simultaneously.

Advanced Asset Monitoring—Track transformer wear with through-fault and thermal monitoring. Reduce inefficient and costly breaker maintenance with advanced breaker monitoring. Monitor substation dc power systems for out-of-tolerance voltage levels or excessive voltage ripple.

Station Phasor Measurement Unit (PMU)—Improve power system quality with SEL synchrophasors (IEEE C37.118) from all 24 analog channels (6 voltage and 18 current sources) in your relay. Use synchrophasors over serial or Ethernet communications to easily detect reactive loop flows, turn state estimation into state measurement, and provide early warning of potential system instability. Implement real-time control by receiving synchrophasor messages from two PMUs, and take action based on local and remote messages.

Dependable Backup Protection—Provide backup protection with five phase, negative-sequence, and zero-sequence overcurrent elements and ten configurable time-overcurrent elements. Quickly identify the faulted phase with faulted-phase indications for each overcurrent element. Set up breaker failure protection with subsidence detection to rapidly detect breaker failure and minimize system coordination times.

TiDL Technology—Modernize your substation by applying the TiDL-enabled SEL-487E with the SEL-2240 Axion TiDL nodes. In a TiDL system, the Axion node provides remote I/O and digitizes analog signals over fiber optics for the relay. This simple and secure digital substation solution is easy to implement, with no external time source or network engineering required. Replacing copper with fiber increases safety, reduces costs associated with using copper, improves reliability, and limits the impact of an electromagnetic pulse.



Send IEEE C37.118 synchrophasor messages over serial or Ethernet communications to detect reactive loop flows, turn state estimation into state measurement, and provide early warning of potential system instability. Apply control functions based on phase angles, currents, and voltages for basic or advanced applications. Multicast synchrophasor data to simplify system architecture and improve system operations. For applications requiring a dedicated phasor measurement unit (PMU), choose the SEL-487E-4 Station Phasor Measurement Unit.

Current Differential Protection With Two to Five Restraints
Achieve fast, sensitive, dependable, and secure differential protection. A two-stage slope adapts to internal or external fault conditions automatically, even with CT saturation and heavily distorted waveforms.

Additional Protection
Apply two 3-phase voltage inputs for over- and undervoltage, frequency, synchronism check, and volts-per-hertz protection. Make any overcurrent element directional using voltage-polarized directional elements as torque control inputs to the overcurrent elements. Implement transformer and feeder backup protection using adaptive time-overcurrent (IDMT) elements. Apply three independent REF elements for sensitive ground fault detection in grounded wye transformer applications.

Security and Dependability
Provide maximum security during external faults and transformer magnetizing inrush conditions. Detect internal faults quickly, during energization or normal operating conditions, using combined harmonic-blocking and -restraint differential elements. Detect turn-to-turn winding faults for as little as 2 percent of the total transformer winding with the negative-sequence differential element.

Monitoring and Asset Management
Monitor critical substation assets with the IEEE C57.91 thermal model for mineral oil-immersed transformers. Advanced monitoring features include transformer through fault, substation battery voltage, and comprehensive breaker wear monitoring.

Metering and Reporting
Eliminate external recorder and metering requirements with oscillographic event reports, Sequential Events Recorder (SER) reporting, and three-phase power metering. Apply these tools to simplify post-fault analysis and improve your understanding of protective scheme operations.

Flexible Communications
An Ethernet card option provides two copper or fiber ports for failover redundancy. Available Ethernet communications protocols include FTP, Telnet, DNP3 LAN/WAN, SNTP, the IEEE 1588 Precision Time Protocol Version 2 (PTPv2), IEC 61850, the Parallel Redundancy Protocol (PRP), and IEEE C37.118 synchrophasors.

All four independent EIA-232 serial ports support SEL Fast Message, SEL ASCII, Compressed ASCII, SEL Fast Operate, SEL Fast Meter, SEL Fast SER, enhanced SEL Mirrored Bits communications, DNP3 Level 2 Outstation plus dial-out, Virtual Terminal, and communications with SEL-2600 Series RTD Modules.

Rugged Design
Trust the industry’s widest ambient operating temperature range, –40° to +85°C (–40° to +185°F).

Front-Panel One-Line Diagrams Control and Monitoring
Select your own system bay configuration, and control as many as five breakers and 20 disconnect switches using the built-in mimic diagrams that include programmable analog quantities for readouts as shown on the high- and the low-voltage diagrams below.

Automation and Control
Implement SELogic control equations with SELogic variables, timers, latch bits, and remote control elements for customizing advanced protection and control schemes. Use control logic to replace panel control switches, RTU-to-relay wiring, latching relays, and traditional indicating panel lights.

Time-Domain Link Technology
Apply a TiDL solution, where Axion TiDL nodes are placed in the yard close to the primary equipment to digitize discrete I/O signals and analog data and then transport them over a fiber-optic cable to the SEL-487E in the control house. This innovative technology uses point-to-point connections and a nonroutable protocol, providing a simple and secure solution. Because it does not need an external time source or Ethernet switches, it is easy to implement with no network engineering required. TiDL combines the proven protection of the SEL-400 series relays with the modularity of the Axion, reducing training requirements and providing a scalable and flexible solution. It also provides built-in time synchronization and synchronous sampling, ensuring protection is available in the relay regardless of whether or not an external time signal is available.

  • Station phasor measurement unit (PMU).
  • Screw terminal or Connectorized hardware configuration.
  • Euro Connector with low-energy analog (LEA) voltage measurement interface.
  • 24/48 Vdc, 48/125 Vdc or 120 Vac, and 125/250 Vdc or 120/240 Vac power supply options.
  • AC input card configurations with a choice of 1A, 5A, or combination of 1A and 5A CT inputs.
  • IEC 61850 communications and IEEE 1588 Precision Time Protocol Version 2 (PTPv2).
  • Ethernet connection options for primary and standby connections:
    • 10/100BASE-T
    • 100BASE-FX
  • Vertical (5U chassis size only) or horizontal-, rack-, or panel-mount hardware packages.
  • One or two additional I/O boards with standard, high-interrupting, or high-speed/high-interrupting outputs.
  • Conformal Coating—Protect equipment from harsh environments and airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture.




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