Siemens siprotec SJ62 User Manual page 189

2 Functions
Current Symmetry
187
Figure 2-58 Current sum monitoring
During normal system operation, symmetry among the input currents is expected. The
symmetry is monitored in the device by magnitude comparison. The smallest phase
current is compared to the largest phase current. Asymmetry is detected if | Imin | / |
Imax | < BAL. FACTOR I as long as Imax / I
Thereby I is the largest of the three phase currents and I
max
metry factor BAL. FACTOR I represents the allowable asymmetry of the phase cur-
rents while the limit value BALANCE I LIMIT is the lower limit of the operating range
of this monitoring (see Figure 2-59). Both parameters can be set. The dropout ratio is
about 97%.
This malfunction is reported as „Fail I balance".
Figure 2-59 Current symmetry monitoring
> BALANCE I LIMIT / I
Nom
the smallest. The sym-
min
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
is valid.
Nom