Functions
2.14 Monitoring Functions
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
166
Figure 2-65
Current symmetry monitoring
Voltage Balance
During healthy system operation, a certain balance of the voltages can be assumed. The monitoring of the
measured values in the device checks this balance. The smallest phase-to-phase voltage is compared to the
largest. Imbalance is recognized if
|V
min
| / | V
max
| <
BAL. FACTOR V
as long as | V
max
| >
BALANCE V-LIMIT
Where V
max
being the largest of the 3 phase-to-phase voltages and V
min
the smallest. The balance factor
BAL.
FACTOR V
(address
2903
) represents the permitted imbalance of the conductor voltages while the limit value
BALANCE V-LIMIT
(address
2902
) is the lower limit of the operating range of this monitoring (see Figure 2-
66). The dropout ratio is about 97%.
After a settable time, this disturbance is signaled with
„Fail V balance“
(no. 167).
Figure 2-66
Voltage symmetry monitoring
