Circuit-Breaker Auxiliary Contact Criterion
Settings allow you to specify whether the circuit-breaker auxiliary contacts are permitted for determining the
circuit-breaker position.
The double-point indication 3-pole position (from the Circuit-breaker function block) is used to deter-
mine whether all 3 poles of the circuit breaker are closed. If the double-point indication is not routed, the
output is an error message. Furthermore, the Health signal changes to the state
Warning
.
The detection of a static disturbed position (not an intermediate position) has the effect that the circuit-
breaker auxiliary contact criterion is not used (the internal signal Aux.co.crit.: CB Clsd is disabled).
[lokriter-140611-01.tif, 1, en_US]
Figure 6-253 Circuit-Breaker Auxiliary Contact Criterion
Pickup/Dropout
After the start, a check is performed whether the circuit breaker is closed. The current-flow criterion and the
circuit-breaker auxiliary contact criterion are available for this purpose.
Even if the circuit-breaker auxiliary contact criterion is permitted, preference is given to the fulfilled current-
flow criterion because the current-flow criterion is the most reliable criterion for detecting whether the circuit
breaker is closed. This means that the circuit breaker is deemed to be closed if it is closed according to the
current-flow criterion but at the same time open according to the circuit-breaker auxiliary contact criterion.
If no current is flowing at the start time, the function can only pick up on the basis of the circuit-breaker auxil-
iary contact criterion. For this purpose, the circuit-breaker auxiliary contacts must be permitted as criterion.
When the current begins to flow after the start, the function switches over to the current-flow criterion.
If the circuit breaker is detected as closed and the starting condition is present, the function picks up.
The pickup starts a time delay (see Delay/Tripping). While the delay is running, the system checks continuously
whether the circuit breaker has opened. In the default setting, the opening of the circuit breaker is checked on
the basis of the currently valid criterion, which is normally the current-flow criterion because it is preferred. If
until expiration of the time delay, no current flow above the set threshold values has been detected, the
circuit-breaker auxiliary contact criterion becomes effective.
The function has also a setting in which dropout is only possible if both criteria detect in parallel the circuit
breaker to be open (dropout with auxiliary contact and current-flow criterion).
In the default setting, the internal starting signal is held (see Figure 6-249 and Figure 6-251). This means that
dropout is controlled solely by the switch or the circuit-breaker auxiliary contact criterion. If dropout is also to
occur on the falling edge of the starting signal (that is, when the pickup signal has a falling edge or the protec-
tion function trips), holding of the start signal must be disabled.
Protection and Automation Functions
6.41 Circuit-Breaker Failure Protection
SIPROTEC 5, Overcurrent Protection, Manual 841
C53000-G5040-C017-8, Edition 07.2017
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