
Functions
2.1 General
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
39
Current Flow Monitoring (Breaker)
Address
212
BkrClosed I MIN
corresponds to the threshold value of the integrated current flow monitoring
system. This parameter is used by several protection functions (e.g. overload protection and auto-reclosure for
motors). If the set threshold current is exceeded, the circuit breaker is considered closed and the power system
is considered to be in operation.
The threshold value setting applies to all three phases, and must take into consideration all used protection
functions.
The pickup threshold for the circuit-breaker failure protection is set separately (see 2.12.2).
When using the device as motor protection and using the overload protection, load jam protection and restart
inhibit, the protective relay can distinguish between a running motor and a stopped motor, as well as take into
account the different motor cooldown behavior. For this application, the set value must be lower than the
minimum no-load current of the motor.
Circuit-breaker Maintenance (Breaker)
Parameters
260
to
267
are assigned to CB maintenance. The parameters and the different procedures are
explained in the setting notes of this function (see Section 2.17.2).
Two-phase Time Overcurrent Protection (Protection Operating Quantities)
The two-phase overcurrent protection functionality is used in grounded or compensated systems where inter-
action of three-phase devices with existing two-phase protection equipment is required. Via parameter
250
50/51 2-ph prot
the time overcurrent protection can be configured to two or three-phase operation. If the
parameter is set to
ON
, the value 0 A instead of the measured value for
I
B
is used permanently for the threshold
comparison so that no pickup is possible in phase B. All other functions, however, operate in three phases.
Ground Fault Protection (Protection Parameters)
With address
613
50N/51N/67N w.
you define whether ground fault protection or breaker failure protection
is to operate using measured values (
Ignd (measured)
) or the quantities calculated from the three phase
currents (
3I0 (calcul.)
). In the first case, the measured quantity at the fourth current input is evaluated. In
the latter case, the summation current is calculated from the three phase current inputs. If the device features
a sensitive ground current input (measuring range starts at 1 mA), the ground fault protection always uses the
calculated variable 3I0. In this case, parameter
613
50N/51N/67N w.
is not available.