Measuring Voltage Failure Detection - Siemens SIPROTEC 7SK80 Manual

Phase Sequence of Voltage and Current
To detect swapped phase connections in the voltage and current input circuits, the phase sequence of the
phase-to-phase measured voltages and the phase currents are checked by monitoring the sequence of same
polarity zero crossing of the voltages.
Direction measurement with normal voltages, path selection for fault location, and negative sequence detection
all assume a phase sequence of "abc". Phase rotation of measurement quantities is checked by verifying the
phase sequences. For that purpose, the phase-sequence monitoring uses the phase-to-phase voltages V
V , V .
BC CA
Voltages: V
AB
Currents: I beforeI
A
Verification of the voltage phase rotation is done when each measured voltage is at least
|V |, |V |, |V
AB BC
Verification of the current phase rotation is done when each measured current is at least:
|I |, |I |, |I | > 0.5 I
A B C
For abnormal phase sequences, the messages „Fail Ph. Seq. V" or „Fail Ph. Seq. I" are issued,
along with the switching of this message „Fail Ph. Seq.".
For applications in which an opposite phase sequence is expected, the protective relay should be adjusted via
a binary input or the respective parameterPHASE SEQ. (address 209). If the phase sequence is changed in
the relay, phases B and C internal to the relay are reversed, and the positive and negative sequence currents
are thereby exchanged (see also Section 2.16.2). The phase-related messages, malfunction values, and mea-
sured values are not affected by this.

2.10.1.5 Measuring Voltage Failure Detection

Requirements
The measuring voltage failure detection function - referred to as Fuse Failure Monitor (FFM) - only operates if
parameter 213 VT Connect. 3ph is set to Van, Vbn, Vcn or Vab, Vbc, VGnd. With all other voltage
transformer connection modes, FFM is not operative.
With a capacitive voltage connection, FFM and broken wire monitoring of the voltage transformer circuits are
not available.
Tasks of the Fuse Failure Monitor
In the case of a measuring voltage failure caused by a short-circuit or broken wire in the secondary voltage
transformer system, a zero voltage can be simulated to individual measuring loops.
The displacement voltage element of the (sensitive) ground fault detection, the time overcurrent protection
ground and the undervoltage protection can thereby obtain incorrect measuring results.
The blocking of this function by the FFM is configurable.
The FFM can become effective in grounded as well as in isolated systems provided that the connection mode
Van, Vbn, Vcn or Vab, Vbc, VGnd was set. Of course, the miniature circuit breaker and FFM can also be
used for the detection of a measuring voltage failure at the same time.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
before V before V and
BC CA
beforeI .
B C
| > 40 V.
CA
.
Nom
Functions
2.10 Monitoring Functions
,
AB
161