SEL-311C Transmission Protection System

Model: SEL-311C

Transmission Protection System

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

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.

Feature Distance ProtectionIncrease 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 ProtectionAdd three zones of high-speed phase mho and ground mho distance elements with the SEL-311C-3 to provide subcycle tripping times.

Breaker Failure DetectionQuickly 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.

ReclosingRestore 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 SheddingOperate 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.


Subcycle Distance Elements
Increase transmission line loading, reduce equipment damage, and improve system stability with subcycle phase and ground distance elements.

Reclosing Control
Apply four-shot reclosing with sequence coordination, synchronism check, and voltage check.

Fault Locator
Calculate accurate distance-to-fault measurements using the impedance-based fault locator.

Fast Dropout Breaker Failure Element
High-speed breaker failure element and native breaker failure logic enhance breaker failure detection.


IEC 61850 Communications Protocol
Apply optional IEC 61850 communications to the SEL-311C Transmission Protection System for guaranteed performance of substation automation and control. Streamline configurations of IEC 61850 enabled relays with acSELerator Architect SEL-5032 Software.

Mirrored Bits Communications Technology
Provide fast and reliable relay-to-relay communication for advanced communications-assisted protection, network reconfiguration, pilot protection, and restoration schemes.

Modbus, DNP3, and ASCII Protocols
Easily integrate into new or existing networks with these popular protocols. SCADA links, local HMI, and dial-in modems can access important relay data.

Simple Network Time Protocol (SNTP)
Simplify wiring and installation by receiving a time signal over existing Ethernet networks. SNTP makes a good backup to more accurate IRIG-B time synchronization. The 5 ms accuracy is ideal for basic time synchronization throughout a substation.

Built-In IEEE C37.118 Synchrophasors
Monitor distribution and transmission networks to detect potential cascading voltage collapse before it happens. IEEE C37.118 synchrophasors, at up to 60 messages per second, allow access to system values for wide-area monitoring and control. The IEEE C37.118 standard simplifies communication and data coordination between synchrophasor measurement units.

Monitoring and Metering

Enhanced Breaker Monitoring
Inspect reports for the most recent trip and close operating times and average operating times, or gather trending data for up to 128 previous operations. This information allows timely and economical scheduling of breaker maintenance.

Metering and Reporting
Apply these advanced features: event reports, Sequential Events Recorder (SER), circuit breaker contact wear monitor, substation battery monitor, instantaneous and demand metering, and local display panel.

Built-In Web Server
Access basic relay information on a standard Ethernet network with the built-in web server. View relay status, SER data, metering information, and settings for easy access within a local network. Web server access requires a relay password and is limited to read-only viewing of information.


  • 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

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