Siemens 7SC80 Manual page 318

Functions
2.18 Breaker Failure Protection 50BF
Monitoring of the Current Flow
Address 170 50BF can be set so 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 plausibility (setting
enabled w/ 3I0>), see the following figure. With the setting Enabled w/o I>, only the circuit breaker
auxiliary contacts are evaluated. The current criterion CB Icrit.closed is not included in the logic.
The currents are filtered through numerical filters to evaluate only the fundamental harmonic. They are moni-
tored and compared to the set limit values. Besides the 3 phase currents, 2 additional currents are provided to
enable a plausibility check. For this plausibility check, separate threshold values can be used if this is config-
ured accordingly (see
The ground current Ι
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·Ι
as plausibility current.
[7sc80-plausibilitaet-i-sv-20110722, 1, en_US]
Figure 2-105
Monitoring of the Circuit Breaker Auxiliary Contacts
Evaluation of the circuit breaker's auxiliary contacts depends on the type of contacts, and how they are
connected to the binary inputs:
•
the auxiliary contacts for circuit breaker "open" (4602
•
only the auxiliary contact for circuit breaker "open" is configured (4602
•
only the auxiliary contact for circuit breaker "closed" is configured (4601
•
none of the two auxiliary contacts is configured.
318
Figure 2-105).
(3·Ι ) is preferably used as plausibility current. Via the parameters 613 you decide
N 0
Monitoring of the current flow
or a second phase current is used
2
>52-b ) and "closed" (4601 >52-a ) are configured,
>52-b ),
>52-a ),
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017