Siemens SIPROTEC 4 User Manual page 184

Functions
2.12 Monitoring Functions
[stromsymmetrieueberwachung-020313-kn, 1, en_US]
Figure 2-71
Voltage Symmetry
During normal system operation, balance among the voltages is expected. Since the phase-to-phase voltages
are insensitive to ground faults, the phase-to-phase voltages are used for balance monitoring. If the device is
connected to the phase-to-ground voltages, then the phase-to-phase voltages are calculated accordingly,
whereas, if the device is connected to phase-to-phase voltages and the displacement voltage V
phase-to-phase voltage is calculated accordingly. From the phase-to-phase voltages, the device generates the
rectified average values and checks the balance of their absolute values. The smallest phase voltage is
compared with the largest phase voltage.
Asymmetry is recognized if
| V | / | V | < BAL. FACTOR V as long as | V
min max
three voltages and V
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 2-70). Both parameters can be set. The
dropout ratio is about 97%.
This fault is signalled after settable delay time with
[spannungssymmetrieueberwachung-020313-kn, 1, en_US]
Figure 2-72
184
Current symmetry monitoring
the smallest. The symmetry factor BAL. FACTOR V (address 8103) represents the
min
Voltage symmetry monitoring
| > BALANCE V-LIMIT. Where V
max
Fail V balance .
C53000-G1140-C207-8, Edition 08.2016
, then the third
0
is the highest of the
max
SIPROTEC 4, 7SJ62/64, Manual