DIN EN 60255-121:2015-01

This standard specifies minimum requirements for the distance protection function typically used in line applications for three-phase power systems. It covers the distance protection function whose operating characteristic can be defined on an impedance plane and includes specifications of the protection function, measurement characteristics, phase selection, directionality, starting and time delay characteristics. The test methodologies for verifying performance characteristics and accuracy are included in this standard. The standard defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions. It also includes the instrument transformer requirements for the protection function. The general requirements for measuring relays and protection equipment are defined in DIN EN 60255-1 (VDE 0435-300). The responsible committee is DKE/K 434 "Messrelais und Schutzeinrichtungen" ("Measuring relays and protection equipment") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.