Siemens SIPROTEC 4 User Manual page 492

Technical Data
4.17 Ground Fault Detection (Sensitive/Insensitive)
Logarithmic Inverse Trip Time characteristic with knee point
[7sj6x_portugal_kennlinie-010704-he, 1, en_US]
Figure 4-12
492
Trip-time characteristics of the inverse-time ground fault protection with logarithmic inverse
time characteristic with knee point (example for 51Ns= 0.004 A)
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016