Siemens SIPROTEC 7SD80 User Manual

Functions
2.14 Monitoring Functions
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
169
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 trans-
former secondary circuit, certain measuring loops may mistakenly see a voltage of zero. Simultaneously exist-
ing 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.

Siemens SIPROTEC 7SD80 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SD80
Category	Protection Device
Language	English