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Transformer Protection Relay

Protect and monitor most transformer applications with the powerful SEL-487E. It offers up to five three-phase restraint inputs, three independent restricted earth fault (REF) protection elements, and two three-phase voltage inputs, all with synchrophasors. The SEL-487E limits transformer damage by responding to internal fault conditions in less than 1.5 cycles. The relay also helps avoid catastrophic transformer failure by detecting turn-to-turn faults involving as little as 2 percent of the total winding. You can minimize commissioning time and eliminate costly errors with included 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 and SEL Sampled Values (SV) technology using IEC 61850-9-2 transform the way you modernize your substation.

SEL-400 Series Relay Mimic Diagrams

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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. Three independent REF elements provide protection of grounded-wye windings. You can invert individual or grouped CT or PT polarities to account for field wiring or protection zone changes.

Sensitive Turn-to-Turn Fault Detection—Avoid catastrophic transformer failure by detecting 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. With a typical two-winding transformer application, you can 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 and protecting generator and transformer winding temperatures simultaneously.

Advanced Asset Monitoring—Track transformer wear with through-fault and thermal monitoring. Advanced breaker monitoring helps reduce inefficient and costly breaker maintenance. The SEL-487E can 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. You can use synchrophasors over serial or Ethernet communications to easily detect reactive loop flows, turn state estimation into state measurement, and provide an early warning of potential system instability. By receiving synchrophasor messages from two PMUs, you can implement real-time control 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. The SEL-487E helps you quickly identify the faulted phase with faulted-phase indications for each overcurrent element. You can set up breaker failure protection with subsidence detection to rapidly detect breaker failure and minimize system coordination times.

Digital Secondary System Technologies—Apply the TiDL-enabled SEL-487E-3/-4 with the SEL-2240 Axion TiDL nodes in the field to provide remote I/O and digitize analog signals over fiber optics. This simple and secure solution is easy to implement, with no external time source or network engineering required. Apply the SEL-487E-5 with SV technology to receive IEC 61850-9-2 SV data from a remote merging unit. TiDL and SEL SV technologies for digital secondary systems replace copper with fiber to increase safety, reduce costs associated with using copper, improve reliability, and limit the impact of an electromagnetic pulse.

SEL-487E-3/-4 Protection, Automation, and Bay Control System

487 front visual motion

From the front panel, control and view the status of disconnects and breakers, program operator pushbuttons, and configure labels. LEDs with custom alarms help dispatchers and line crews rapidly restore power.

SEL-487E-3/-4 Without TiDL Technology

487e back visual motion

The 18 current and 6 voltage channels support transformer differential protection for up to 5 three-phase terminals, 3 independent REF elements, and voltage elements. The front and rear EIA-232 serial ports and a rear Ethernet port provide communications.

SEL-487E-3/-4 With TiDL Technology

487e tidl back

Fiber-optic ports on the 4U chassis allow the relay to receive analog and digital data from remote TiDL nodes. Commissioning is easy with a press of a button. LEDs indicate a valid configuration as well as the connection status to a remote TiDL node on a per-port basis.

SEL-487E-5 Relay With IEC 61850-9-2 Sampled Values

487E sv back

Receive digitized current and voltage information from remote merging units. On this 4U chassis, select fiber optics, copper, or mixed Ethernet with separate ports for SV data and engineering access. The Ethernet links are self-monitoring.

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 three-phase voltage inputs for over- and undervoltage, frequency, synchronism check, and volts-per-hertz protection. You can make any overcurrent element directional using voltage-polarized directional elements as torque control inputs to the overcurrent elements. Adaptive time-overcurrent (IDMT) elements allow you to implement transformer and feeder backup protection. Three independent REF elements enable sensitive ground fault detection in grounded wye transformer applications.

Security and Dependability
Provide maximum security during external faults and transformer magnetizing inrush conditions. You can detect internal faults quickly, during energization or normal operating conditions, using combined harmonic-blocking and -restraint differential elements. The SEL-487E can 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 and protect critical substation assets with the IEEE C57.91 and IEC 60255-149 thermal models for mineral oil-immersed transformers. You can use the IEC thermal element to trip a breaker or use either the IEC or the IEEE thermal elements to activate a control action or issue an alarm when the transformer is in danger of excessive insulation aging or loss of life. 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. These tools 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 Edition 2, 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.

Front-Panel One-Line Diagrams Control and Monitoring
Select your own system bay configuration, and control as many as 5 breakers and 20 disconnect switches using the built-in mimic diagrams that include programmable analog quantities for readouts.

Automation and Control
Implement SELogic control equations with SELogic variables, timers, latch bits, and remote control elements for customizing advanced protection and control schemes. Control logic can 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 an external time signal is available.

SEL Sampled Values Technology
Implement an SEL SV solution, where the merging unit (publisher) digitizes analog signals from primary equipment and then transmits them to an SEL-487E-5 Relay (subscriber) in the control house via a fiber-based Ethernet network. The system uses precise time synchronization via IRIG-B or PTP. The SEL-487E-5 Relay offers the traditional protection available in the SEL-487E-3/-4 and can also receive SV data from devices such as the SEL-401 Protection, Automation, and Control Merging Unit or the SEL-421-7 Protection, Automation, and Control System Merging Unit. Because all SEL SV devices are compliant with IEC 61850-9-2 and the UCA 61850-9-2LE guideline, the SEL-487E-5 can be used with other manufacturers’ SV-compliant units.

  • Digital secondary system solutions.
    • SEL-487E-3/-4 Relay with TiDL technology.
    • SEL-487E-5 Relay (subscriber) with IEC 61850-9-2 Sampled Values.
  • 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 Edition 2 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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