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Stage with Definite-Time Overcurrent Protection, Undervoltage Seal-In
6.4.5
6.4.5.1
Description
Logic of the Stage
[lo_Seal-in_20150215, 2, en_US]
Figure 6-29
Undervoltage Seal-In
In generators where the excitation voltage is derived from the machine terminals, the short-circuit current
decreases quickly in the event of close-in faults (for example, in a generator or a generator-transformer
range). The current decreases to a value below the current threshold within a few seconds because of the
absence of the excitation voltage. To avoid a dropout of the relay, the positive-sequence voltages are used as
an additional criterion for detecting a short circuit.
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
Logic Diagram of the Definite-Time Overcurrent Protection, Undervoltage Seal-in
Protection and Automation Functions
6.4 Voltage-Dependent Overcurrent Protection, Phases
369
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