A comprehensive guide to practical line current differential schemes using digital
communications. Operating principles, synchronization methods, channel requirements, current
transformer requirements, external time reference requirements, backup considerations, testing
considerations, and troubleshooting are included. This guide also provides specific guidelines for
various application aspects including multi-terminal lines, series compensated lines, mutually
coupled lines, line charging current, in-zone transformers and reactors, single-phase tripping and
reclosing, as well as communications channel requirements.