SEL Communications Protocols — SEL Protocol, MIRRORED BITS, and Fast Message
Key Takeaway
Overview of SEL native communication protocols — SEL proprietary protocol for configuration, MIRRORED BITS for pilot protection, and Fast Message for automation.
Quick Answer
SEL relays use three proprietary protocols: SEL protocol (ASCII serial for configuration and data extraction), MIRRORED BITS (peer-to-peer Boolean transfer for pilot protection), and Fast Message (high-speed Boolean for automation). Open protocols (DNP3, Modbus, IEC 61850) handle SCADA integration.
SEL Protocol
ASCII-based serial protocol over RS-232/RS-485. Used by ACSELERATOR Quickset. Commands: ACC (access), SHO (show settings), TAR (targets), EVE (events), MET (metering). Access levels via password.
MIRRORED BITS
Peer-to-peer between two SEL relays over dedicated fiber or copper channel. Transfers relay word bits in real time (<1ms on fiber). Used for pilot protection schemes (POTT, DCB) — one relay sends its directional element state to the remote relay.
Fast Message
High-speed sub-cycle Boolean messaging for time-critical automation applications with SEL RTAC.
Protocol Selection
Frequently Asked Questions
Peer-to-peer Boolean transfer between two SEL relays over dedicated channel. Transfers relay word bits in real time for pilot protection schemes.
SEL protocol is proprietary ASCII for configuration and Quickset connections. DNP3 is an open standard for SCADA polling. SEL protocol for maintenance, DNP3 for SCADA.