html{display:none} SEL-311C Transmission Protection System | Schweitzer Engineering Laboratories


Transmission Protection System

Apply the SEL-311C Relay for protection, reclosing, monitoring, and control of transmission lines.

Features include a four-shot recloser, patented capacitance voltage transformer (CVT) transient overreach logic to enhance security of Zone 1 distance elements, and overcurrent elements with directional control, monitoring, and metering. Apply three-pole tripping logic, or select the SEL-311C-3 for single-pole tripping. The SEL-311C comes standard with EIA-232 serial ports as well as a 10/100 BASE-T Ethernet port for local/remote access and system integration. IEEE C37.118 compliant synchrophasors are included for improved situational awareness.

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Distance Protection—Increase transmission line loading, reduce equipment damage, and improve system stability with phase and ground distance elements. The SEL-311C Transmission Protection System provides four zones of phase mho, ground mho, and ground quadrilateral distance elements. The SEL-311C-1 features the ability to connect either wye or delta voltage transformers (VTs) for phase distance protection.

Subcycle Distance Protection—Add three zones of high-speed phase mho and ground mho distance elements with the SEL-311C-3 to provide subcycle tripping times.

Breaker Failure Detection—Quickly detect failed circuit breakers with the built-in breaker failure detection elements and logic. The high-speed breaker failure element drops out less than one cycle after successful breaker operation, even with subsidence current.

Reclosing—Restore service following transient faults by using programmable four-shot breaker autoreclosing with synchronism and voltage check logic. The synchronism check function compensates for breaker close time, frequency, magnitude, and angle differences between the two voltage sources used for synchronism.

Fault Location—Calculate accurate distance-to-fault measurements with the impedance-based fault locator. Obtain fault resistance calculations for enhanced fault studies.

Load Shedding—Operate six levels of frequency elements as either an under- or overfrequency element. The frequency elements are suited for applications such as underfrequency load shedding and restoration control systems.

Communications-Assisted Tripping Schemes—Configure protection for transmission lines without any need for external coordination devices. The SEL-311C includes settings for permissive overreaching transfer trip (POTT), directional comparison unblocking (DCUB), and directional comparison blocking (DCB) schemes.

Out-of-Step Blocking and Tripping—Detect stable or unstable power swings with out-of-step detection logic. Enhance security with out-of-step blocking to block distance elements during stable swing conditions. Implement out-of-step tripping during unstable power swing conditions to maintain a generation load balance.

Innovative Logic for Secure Operation—Use loss-of-potential logic to detect blown potential transformer (PT) fuses and disable distance and directional elements that are affected by voltage. Recognize coupling capacitor voltage transformer (CCVT) transients during Zone 1 faults with built-in CCVT detection logic. Delay the distance element during CCVT transients to prevent a Zone 1 distance overreach and improve sensitivity.


    1. 1

      Simplify local connection and speed up relay communications with the front-panel USB port

    2. 2

      Use default displays, or program custom messages

    3. 3

      Optional field-configurable, programmable operator pushbuttons with user-configurable labels

    4. 4

      Optional programmable front-panel LEDs for custom alarms

    5. 5

      Optional independent SafeLock® trip/close pushbuttons with high-visibility indication

    6. 6

      Mirrored Bits communications

    7. 7

      Built-in phasor measurement unit

    8. 8

      Advanced SELogic control equations

    1. 1

      High-current interrupting output contacts

    2. 2

      Standard multisession Modbus TCP and DNP3. Optional IEC 61850

    3. 3

      Standard dual copper, optional single or dual fiber-optic Ethernet ports, or one copper and one fiber-optic Ethernet port

    4. 4

      Standard EIA-485 or fiber-optic serial port, or optional fiber-optic serial port

    5. 5

      Independent terminals for SafeLock trip/close pushbuttons

    6. 6

      Optional expanded I/O



  • High-speed distance elements
  • Single-pole trip with three-pole reclosing
  • Vertical panel-mount hardware package
  • Horizontal panel-mount hardware package
  • Vertical rack-mount hardware package
  • Front USB port
  • Dual Ethernet ports—10/100BASE-T and 100BASE-FX
  • EIA-485 port
  • SEL-2812-compatible, fiber-optic serial port
  • SafeLock trip/close pushbuttons
  • Programmable operator controls and target LEDs
  • Additional inputs and additional standard outputs, high-current interrupting outputs, or high-speed, high-current interrupting outputs
  • IEC 61850 communications protocol
  • Conformal coating protects 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-311C-1 R508-V4 SEL-311C-1-R508-V4-Z104101-D20210917 9/28/21 ~1212710001 or ~3212710001
SEL-311C-2 R508-V4 SEL-311C-2-R508-V4-Z104101-D20210917 9/28/21 ~1212710001 or ~3212710001
SEL-311C-3 R508-V4 SEL-311C-3-R508-V4-Z104101-D20210917 9/28/21 ~1212710001 or ~3212710001

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

Minimum Software Version

3xx Software Tab

Configuration Software

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 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 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.

Product Certifications