html{display:none} SEL-787Z High-Impedance Differential Relay and SEL-HZM High-Impedance Module | Schweitzer Engineering Laboratories


High-Impedance Differential Relay and SEL-HZM High-Impedance Module

The SEL-787Z combines high-impedance protection principles with advanced numerical technologies to provide high-impedance differential protection. Apply the SEL-787Z and SEL-HZM for a comprehensive single-zone bus protection solution.

Multiple resistor options in the SEL-HZM allow you to customize the device to fit your application. An optional bypass relay and 7.8 kJ metal oxide varistors (MOVs) in the SEL-HZM protect the relay from fault currents. The three independent high-impedance elements in the SEL-787Z can also be used to provide sensitive restricted earth fault (REF) protection on transformers with grounded-wye connections. Overcurrent elements provide backup transformer protection.

Use the 5-inch (12.7 cm) color touchscreen to configure settings, access event data, and manually reclose breakers at the relay without using a laptop. Perform these functions remotely and simplify interconnections using a variety of common communications protocols, such as DNP3, Modbus, and IEC 61850 protocols.

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High-Impedance Differential Protection—Provide high-speed, economical bus protection with a single three-phase differential zone. The highly secure high-impedance differential element in the SEL-787Z supports both per-phase voltage and current inputs. Apply independent high-impedance elements to single-zone bus protection, reactors, generators, and large motors, or use single elements on grounded transformer windings as REF protection.

SEL High-Impedance Module (SEL-HZM)—Gain complete high-impedance bus protection with a safe and space-saving high-impedance module. Choose from three resistor options in the SEL-HZM to provide security against CT saturation during through faults. The built-in MOV in the SEL-HZM limits voltage across the stabilizing resistor during bus faults.

Flexible Communications—Simplify interconnections using protocols like IEC 61850 Edition 2, DNP3, Modbus, EtherNet/IP, the Rapid Spanning Tree Protocol (RSTP), and more. Use communications protocols for remote device management, including downloading event reports, upgrading firmware, and resetting the relay. Four selectable settings groups in the SEL-787Z can cover a wide range of protection and control contingencies, increasing the adaptability of systems requiring frequent settings changes.

High-Resolution Event Records—Increase system visibility and simplify maintenance schemes with high-resolution event records containing 40 data samples per cycle at 60 Hz (48 data samples per cycle for 50 Hz applications). Use these records to help simplify root-cause analysis.

Arc-Flash Detection (AFD)—Install and monitor up to eight point sensors or clear-jacketed fiber sensors in switchgear and other equipment with the SEL-787Z. Optional fast hybrid outputs provide fast-acting trip outputs to the circuit breaker (less than 50 µs), significantly reducing the incident energy of an arc-flash event. Each AFD channel continually self-tests and monitors optical circuits to detect and alarm for any malfunction, ensuring arc-flash protection for personnel and equipment.

Integrated Web Server—Use the integrated web server and a web browser to access read-only settings information, verify self-test status, inspect metering data, download event reports, and upload firmware. Multilevel password protection separates access to read-only data reports and settings information from interfaces used to upgrade device firmware.

5-Inch (12.7 cm) Color Touchscreen Display—Access metering data, view event records, control relay operations, edit settings, and more, without a laptop. The SEL-787Z touchscreen can be configured to display an English or Spanish language interface. The color touchscreen clearly indicates breaker and primary equipment status, improving safety during maintenance operations.


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      The 5-inch (12.7 cm), 800 × 480 display offers direct navigation via a capacitive touchscreen available in both English and Spanish.

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      Folders and applications provide quick access to bay screens, metering and monitoring data, reports, settings, and more.

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      The home pushbutton allows you to easily return to the default home screen.

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      Programmable front-panel LEDs with user-configurable labels alert operators to faulted phases and element operation.

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      Programmable operator pushbuttons with user-configurable labels allow front-panel customization.

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      Large, 2 × 16 character LCD.

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      Default messages or up to 32 customizable display labels notify personnel of power system events or the relay status.

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      Programmable front-panel LEDs with user-configurable labels alert operators to faulted phases and element operation.

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      Programmable operator pushbuttons with user-configurable labels allow front-panel customization.

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      User-configurable label kit.

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      Two programmable tricolor LEDs per pushbutton.

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      Power supply options include 110–250 Vdc/110–240 Vac or 24–48 Vdc.

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      A variety of communications protocols and media provide flexibility to communicate with other devices and control systems.

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      Integrated web server enables direct relay access for metering and monitoring data.

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      The optional fiber-optic serial port provides quick and easy engineering access.

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      Card slots include positions for optional I/O or eight arc-flash detection inputs.

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      Phase current and optional phase voltage inputs are on one card, freeing up space for additional SELect I/O card options.

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      LED indicates bypass relay status.

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      Three phase-segregated, high-impedance inputs.

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      Bypass relay power supply and control.



IEC 61850 Edition 2 Communications Protocol
Combine IEC 61850, an Ethernet network, and the SEL-787Z for the fastest overall performance for substation automation and control. Streamline configuration of IEC 61850-enabled relays with acSELerator Architect SEL-5032 Software. Improve security using the password authentication and session time-out features. Transfer event files in COMTRADE and CEV formats as well as CID files, settings, and reports.

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

Web Server Access
The built-in web server enables secure, remote access to the relay with password protection. You can download status reports or view metering and relay information remotely. This helps minimize trips to the relay location, saving time and money.

Rugged Design
The SEL-787Z withstands vibration, electrical surges, fast transients, and extreme temperatures, including the industry’s widest ambient operating temperature range, –40° to +85°C (–40° to +185°F).

5-Inch (12.7 cm) Color Touchscreen Display
The easy-to-use touchscreen interface provides a one-line mimic display for bay control and monitoring, and it can be configured with either an English or Spanish language interface. View 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.

Flexible Mounting and Installation
Apply the SEL-787Z and SEL-HZM for robust high-impedance protection. The two-box solution offers flexibility in panel mounting and installation.

Customizable I/O
Monitor and control more devices with a wide range of analog and digital I/O configurations in the SEL-787Z.

Versatile SELogic
Simplify configuration by using familiar SELogic control equations for high-impedance applications.

  • Flexible I/O for Local Control and System Applications
    The base system includes three DO and two DI. There are three card slots for optional SELect I/O cards, including the following:
    • 8 arc-flash detector input (AFDI) sensor inputs
    • 14 digital inputs (DI)
    • 4 DI and 4 digital outputs (DO)
    • 4 DI and 4 fast, high-current interrupting DO
    • 4 DI and 1 Form B DO or 2 Form C DO
    • 4 DO, 3 DI, and 1 analog output (AO)
    • 4 analog inputs (AI) and 4 AO
    • 8 AI for dc process values
    • 8 DI
    • 8 DO
  • Integrated Communications
    The SEL-787Z offers many communications media and protocol options. Versatile communications options provide fast integration into both new and existing applications.
    • Communications Media
      • Ethernet 10/100BASE-T
      • Ethernet 100BASE-FX
      • Single- or dual-Ethernet ports
      • EIA-232 serial
      • EIA-485 serial
    • Communications Protocols
      • Mirrored Bits communications
      • IEC 61850 Edition 2
      • IEC 60870-5-103
      • IEC 62439-3 Parallel Redundancy Protocol (PRP) and RSTP for models with dual-Ethernet ports
      • DNP3 LAN/WAN
      • DNP3 serial
      • Modbus TCP
      • Modbus RTU
      • Telnet
      • FTP
      • EtherNet/IP
      • IEEE 1588 Precision Time Protocol (PTP)
      • Simple Network Time Protocol (SNTP)
  • Languages
    Ordering option is available for English or Spanish language support.
    • Resistors—500 ohm, 1,000 ohm, and 2,000 ohm
    • 7.8 kJ MOV
    • Bypass relay
  • Mounting Options
    • Panel mount
    • Rack mount
    • Surface mount
  • Conformal Coating
    Protect equipment from harsh environments and airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture.

Minimum Software Version

Latest Firmware Versions

There are no firmware versions available for this product.

Product Revision Firmware ID Date Available Serial Number
SEL-787Z R302-V3 SEL-787Z-R302-V3-Z001001-D20240329 4/5/24 ~3240980001

The Firmware IDs for older versions of the firmware can typically be found in Appendix A of the instruction manual.

Minimum Software Version

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787Z Software Tab


acSELerator Quickset SEL-5030 Software

QuickSet is a tool for engineers and technicians to quickly and easily configure, commission, and manage power system devices. QuickSet includes a Graphical Logic Editor and a device template tool to reduce configuration time and streamline deployment.

Learn more and download on the Quickset software page.


acSELerator Bay Screen Builder SEL-5036 Software

Bay Screen Builder is an integrated application within QuickSet and acSELerator RTAC SEL-5033 Software that lets you create custom bay screens for SEL devices with touchscreen displays. Screens can also be programmed to display current, frequency, voltage values, and other data.

Learn more and download on the Quickset software page.


acSELerator ARCHITECT SEL-5032 Software

Architect allows users to configure and document IEC 61850 systems that include GOOSE, Sampled Values (SV), or Manufacturing Message Specification (MMS) communications. Architect automatically compares SCL files with IEC 61850 requirements to ensure standard compliance.

Learn more and download on the Architect software page.

Automated Data Collection

SEL Data Management and Automation (DMA) Application Suite

Available on the Blueframe platform, DMA applications automatically collect, store, and manage device-specific information like oscillography, Sequence of Events (SOE) data, device settings, and property information. They also provide automated password rotation and streamlined device audits.

Learn more and download on the DMA software page.

Visualization and Analysis

SEL-5601-2 synchroWAVe Event Software

synchroWAVe Event helps engineers diagnose a protective relay’s behavior during a power system fault. It is a powerful and easy-to-use solution for displaying and analyzing SEL relay event reports and COMTRADE files.

Learn more and download on the synchroWAVe Event software page.