- High-Speed, Secure Line Current Differential Protection
Differential elements provide subcycle operating times to improve system stability. Line charging current compensation provides an accurate response for long or short lines. Apply the proven Alpha Plane operating principle for reliable and secure operation. Multiterminal lines and transformers in the differential zone are protected. Communicate using either serial or Ethernet channels.
- Multiterminal Protection With Fault Location
The line current differential protection provides high-speed protection for multiterminal lines, even with two breakers per terminal. Protect up to three terminals using serial communications or up to four terminals using Ethernet. In addition, the unique fault location algorithm uses information from all terminals to identify the faulted branch.
- Reliable Distance Protection
Complete distance and directional elements provide standalone protection or backup protection in differential schemes in the event communications are lost. All the features of the SEL-421 Relay are included in addition to the differential protection.
- Complete Reclosing System With Synchronism Check and High-Speed Breaker Failure Detection for Two Breakers
Dual CT and PT input logic and settings are included for control of two circuit breakers. Settable voltage inputs provide flexible operation. Open-pole detection in less than 5/8 of a cycle allows the use of shorter breaker failure margin times. Independent current inputs provide protection for two circuit breakers.
- Synchrophasor Measurements to Increase Asset Utilization
Validate system load flow and fault models using instantaneous voltage angles. Use system-state measurements to increase stable system loading through reduced margin requirements. Use IEEE C37.118 format with 1–60 messages per second or SEL Fast Message format for interleaved communications. Apply direct relay-to-relay synchrophasors for wide-area-based control without additional devices.
- True Digital Fault Recorder (DFR) Functionality
Use binary COMTRADE event reports sampled at 8 kHz directly from the relay without expensive auxiliary equipment.
- Traveling-Wave Fault Location
Accurately pinpoint faults with time-synchronized traveling-wave fault location. Save time and money by sending maintenance crews to the tower nearest the fault.
- Flexible Communications
An Ethernet card option provides two copper or fiber ports for communication with failover redundancy. Simplify Ethernet network topology and reduce external equipment with dual Ethernet ports that offer a switched mode for looped Ethernet networks. Available Ethernet communications protocols include FTP, Telnet, DNP3 LAN/WAN, the IEEE 1588 Precision Time Protocol Version 2 (PTPv2), IEC 61850, IEEE C37.118 synchrophasors, and the Parallel Redundancy Protocol (PRP).