Siemens SIPROTEC 4 User Manual page 67

In order to avoid an unwanted operation in case of a voltage transformer fault, a function blocking is imple-
mented via a binary input controlled by the voltage transformer protection breaker as well as via the device-
internal measuring voltage failure detection ("Fuse Failure Monitor").
The following two figures show the logic diagrams for the inverse time overcurrent protection with under-
voltage consideration.
[7sjx_logic_51-phase-schleife-aktiv, 1, en_US]
Figure 2-14
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016
Logic diagram of the voltage-controlled inverse time overcurrent protection
2.2 Overcurrent Protection 50, 51, 50N, 51N
Functions
67