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Protection and Automation Functions
6.42 Circuit-Breaker Restrike Protection
The input signals
transient spurious signal to the binary inputs is expected due to the design of the external binary-input control
circuits and environmental conditions, the filtering time can be extended.
Parameter: Position recognition delay
•
Default setting (_:105) Position recognition delay = 0.02 s
With the parameter Position recognition delay, you define how long the circuit breaker must be
detected as open (via the circuit-breaker auxiliary contacts) before the monitoring time is started. This defini-
tion is a safety feature to ensure that the monitoring is not started too early. For example, in case that due to a
non-standard auxiliary-contacts configuration, the circuit-breaker is already detected as open while current
flow is still present.
The setting depends on the circuit-breaker auxiliary-contacts configuration. If it can be ensured that the auxil-
iary contacts announce the circuit breaker as open after the current flow is interrupted, the time can be set to
zero.
Parameter: Monitoring duration
•
Default setting (_:104) Monitoring duration = 200.00 s
With the parameter Monitoring duration , you define how long the current signal is monitored regarding
restriking after the circuit breaker has been opened.
With ongoing discharging of the capacitor bank, the probability of restriking is decreasing. There is no need to
set the monitoring time longer than the discharging time. Siemens recommends setting the monitoring time
in the range of 0.5 * discharging time to 1 * discharging time.
Parameter: Threshold
•
Default setting (_:3) Threshold = 0.250 A
After opening of the circuit breaker, the phase currents are compared with the threshold value. If no restriking
takes place, the current is zero. Consequently the threshold for detecting restriking can be set much smaller
than the operating current. A typical value is 25 % of the operating current.
With a threshold below the operating current, a falsely-given start directly cause tripping. For minimizing this
risk, Siemens recommends applying a release criterion additionally. Refer to
tional Plausibility Release Criteria , Page
Parameter: Dropout delay
•
Default setting (_:7) Dropout delay = 0.05 s
The parameter Dropout delay ensures that a short dropping below the current threshold does not cause
the operate delay timers to be reset.
Since restriking is normally a periodical effect, the dropout delay can be set to a rather small time. Siemens
recommends applying the default value of 50 ms.
Input signal:
>CB defect
The input signal
signal from becoming effective in the case of a transient activation of the physical binary input, which can be
caused by the pressure change when the circuit breaker opens.
This time can be set to 0 if such a transient response of the physical binary input can be excluded due to the
circuit-breaker design.
Parameter: Retrip after T1
•
Default setting (_:106) Retrip after T1 = start T2 after T1
858
>Start , >release , and >Stop have a filtering time of 20 ms as default setting. If a
857.
>CB defect has a preset filtering time of 20 ms. This filtering time prevents the input
Parameter: Switch On or Off Addi-
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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