Siemens 7SC80 Manual page 116

Functions
2.3 Directional Overcurrent Protection 67, 67N
User-Defined Characteristics
When user-defined characteristic are used, the tripping curve may be defined point by point. Up to 20 value
pairs (current, time) may be entered. The device then approximates the characteristic using linear interpola-
tion.
The dropout curve may be user-defined as well. This is advantageous when the overcurrent protection must
be coordinated with conventional electromechanical overcurrent relays located towards the source. If no user-
defined dropout curve is desired, the element drops out as soon as the measured signal is less than approx.
95% of the pickup setting. When a new pickup occurs, the timer starts at zero again.
The following figure shows by way of an example the logic diagram for the 67-TOC relay element of the direc-
tional inverse time overcurrent protection of the phase currents.
116 SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017