Monitoring of the Current Flow
Address 170 50BF can be set in such a way that either the current criterion can already be met by a single
phase current (setting Enabled) or that another current is taken into consideration in order to check the plau-
sibility (setting enabled w/ 3I0>), see Figure 2-97.
The currents are filtered through numerical filters to evaluate only the fundamental harmonic. They are moni-
tored and compared to the set threshold values. Besides the three phase currents, two additional currents are
provided to enable a plausibility check. Separate threshold values can be used for this plausibility check if this
is configured accordingly. To detect ground faults more quickly, the threshold value for the ground current
can also be used for checking the plausibility of the phase currents. This function is activated via binary input
>50BFactiv.3I0>
(see Figure 2-97).
The ground current I
N
(3·Ι
0
) is preferably used as plausibility current. Via the parameters 613 you decide
whether the measured (Ignd (measured)) or the calculated (3I0 (calcul.)) values are to be used. In
case of system faults not involving ground currents, no increased ground currents/residual currents are
flowing, and therefore the calculated triple negative sequence current 3·I2Ι
2
or a second phase current is used
as plausibility current.
[7sj80-plausibilitaet-i-sv-20061218, 1, en_US]
Figure 2-97
Monitoring of the current flow
Functions
2.17 Breaker Failure Protection 50BF
236 SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
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