Static Mho Distance and Pilot Relaying

The functional requirements for high-speed transmission-line relaying are outlined, and a new principle for coordinating ultrahigh-speed tripping units in a pilot relay system is described. Application to 3-terminal lines is reviewed in principle and illustrated by an example. Factory and field tests and a lightning season´s field experience are recorded, showing tripping times of 6 to 16 msec (milliseconds) for the pilot relaying and 0.1 to 15 msec for the phase-backup relaying.