Fundamental basis for d.c.-supplyless distance relays with ferrite cores for transmission line protection

A mathematical basis is established for realising various distance-relay characteristics for transmission-line protection. Phase sequences of a set of three voltage signals provide the criteria for relay operation. A ferrite-core version, modelled as a phase-sequence indicator, is manipulated to realise the conventional as well as unusual operating characteristics. Such versions have been designed and constructed without the requirements of a d.c. supply ¿a decided advantage over semiconductor units.