At least three zones of protection are provided for distance relays. Typically, it is set to cover 80% of the line length. Distance relays measure impedance (Z = V/I) to detect faults. Many important issues, such as coordination of settings, operating times, characteristics of. The time delay of zone 2 and zone 3 elements should be set to coordinate with time-step protection at both the remote and local buses. Settings for zone 3. Core idea: Transmission line protection detects faults and trips the correct breakers so the faulted line section is removed without unnecessarily de-energizing healthy equipment. Engineering use: Protection engineers use distance, differential, directional overcurrent, pilot, and backup schemes to. I.
[PDF Version]