Line Current Differential Protection and Automation System

Use the SEL-311L Line Current Differential Relay with integral four-zone distance backup for easy-to-apply, high-speed line protection.

Apply subcycle current differential protection with included four-zone distance and directional overcurrent backup. Use single or dual differential channels for reliability. Apply the SEL-311L on two- or three-terminal lines. Unique measuring elements provide coordination with tapped loads. Reduce total project construction and operation costs through integration of the included four-shot recloser and relay logic operators into your automation system.

Improve protection system reliability with continuous checks of communications quality, breaker wear, battery voltage, and relay health. Use the included LCD display in place of traditional panel meters.

Applications

Line Current Differential Protection—Apply single- or three-pole subcycle differential protection. A vector ratio of the local and remote phase and sequence currents provides high-speed protection independent of line loading, CT saturation, or tapped load. Use a true hot-standby differential channel for increased dependability and security. Loss of the primary channel does not cause loss of protection.

Distance and Overcurrent Backup—Enable up to four zones of phase and ground mho distance elements plus four zones of ground quadrilateral distance elements. Distance protection plus directional and nondirectional overcurrent elements provide a full backup protection system. Apply distance and overcurrent functions in communications-assisted and stepped-distance schemes.

Direct Fiber or Multiplexed Communications—Provide reliability and security with one or two differential communications channels. Select from ITU-T G.703 or EIA-422 electronic interfaces, IEEE C37.94, 1300 nm single-or multimode optical fiber, or 1550 nm single-mode optical fiber. The Alpha Plane restraint characteristic accommodates channel asymmetry and switching without loss of security or sensitivity.

Three-Terminal and Tapped Lines—Accommodate three-terminal lines, even with weak infeed. Tapped line settings make maximum use of communications for secure protection.