Interaction With Fuse Failure Monitor (Ffm) - Siemens SIPROTEC 4 Manual

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Figure 2-24

Interaction with Fuse Failure Monitor (FFM)

2.3.5
False or undesired tripping can be caused by a measuring voltage that can be caused by either short-circuit or
broken wire in the voltage transformer's secondary system or an operation of the voltage transformer fuse.
Failure of the measuring voltage in one or two phases can be detected, and the directional time overcurrent
elements (Dir Phase and Dir Ground) can be blocked, see logic diagrams.
Undervoltage protection, sensitive ground fault detection and synchronization are also blocked in this case.
For additional information on the operation of the fuse failure monitor, see Section
Supervision.
SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
Logic diagram for the directional overcurrent protection: 67-TOC relay element
2.3 Directional Overcurrent Protection 67, 67N
2.11.1 Measurement
Functions
89