Siemens SIPROTEC 4 7SD80 User Manual

[lo-drahtbruch-110428, 1, en_US]
Figure 2-68
Broken-wire monitoring
Voltage Phase Rotation
Phase rotation of measured voltages is checked by verifying the phase sequences of the voltages
V
A
leads V
B
leads V
C
.
This check takes place if each measured voltage has a minimum magnitude of
|V
A
|, |V
B
|, |V
C
| > 40 V/√3
In case of negative phase rotation, the indication
Fail Ph. Seq. (no. 171) is issued.
Rapid Measuring Voltage Failure "Fuse Failure Monitor"
In the event of a measuring voltage failure due to a short circuit fault or a broken conductor in the voltage
transformer secondary circuit, certain measuring loops may mistakenly see a voltage of zero. Simultaneously
existing load currents may then cause spurious pickup.
If fuses are used instead of a secondary miniature circuit breaker (VT mcb) with connected auxiliary contacts,
then the “Fuse-Failure-Monitor” can detect problems in the voltage transformer secondary circuit. Of course,
the miniature circuit breaker and the “Fuse-Failure-Monitor” can be used at the same time.
Figure 2-69 and Figure 2-70 show the logic of the “Fuse-Failure-Monitor”.
Functions
2.14 Monitoring Functions
154 SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018

Siemens SIPROTEC 4 7SD80 Specifications

General

Brand	Siemens
Model	SIPROTEC 4 7SD80
Category	Power distribution unit
Language	English