Interaction With Fuse Failure Monitor (Ffm) - Siemens 7SK80 Manual

Siprotec motor protection

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Logic diagram of the directional inverse-time overcurrent element 67N-TOC

Interaction with Fuse Failure Monitor (FFM)

Spurious tripping can be caused by a measuring voltage failure due to a short circuit or phase failure in the

voltage transformer secondary system or pickup of the voltage transformer mcb (fuse). In the event of a single-

phase or two-phase failure of the measuring voltage, it is possible to recognize this condition and block the di-

rectional overcurrent time protection elements (ground), see logic diagrams. In such a case, the undervoltage

protection and the sensitive ground fault detection will also be blocked.

For additional information on the operation of the fuse failure monitor, see section 2.10.1 Measured Value Su-

SIPROTEC, 7SK80, Manual

E50417-G1140-C344-A5, Release date 11.2012

2.3 Directional Overcurrent Protection Ground 67, 67N