Functions
2.11 Monitoring Functions
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
202
| V
min
| / | V
max
| <
BAL. FACTOR V
as long as | V
max
| >
BALANCE V-LIMIT
. Where V
max
is the highest of the
three voltages and V
min
the smallest. The symmetry factor
BAL. FACTOR V
(address
8103
) represents the
allowable asymmetry of the conductor voltages while the limit value
BALANCE V-LIMIT
(address
8102
) is the
lower limit of the operating range of this monitoring (see Figure 2-67). Both parameters can be set. The dropout
ratio is about 97%.
This malfunction is reported as
„Fail V balance“
.
Figure 2-67
Voltage symmetry monitoring
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 transitions 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
AB
,
V
BC
, V
CA
.
Voltages: V
AB
before V
BC
before V
CA
and
Currents:
I
A
before
I
B
before
I
C
.
Verification of the voltage phase rotation is done when each measured voltage is at least
|V
AB
|, |V
BC
|, |V
CA
| > 40 V.
Verification of the current phase rotation is done when each measured current is at least:
|
I
A
|, |
I
B
|, |
I
C
| > 0.5
I
Nom
.
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 parameter
PHASE 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 2.21.2). The phase-related messages, malfunction values, and mea-
sured values are not affected by this.
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