Function Description
Logic of the Function
[loreffkt-170712-01.tif, 1, en_US]
Figure 6-264
Logic Diagram of the Restricted Ground-Fault Protection Function
The protection function processes the neutral-point current I
0
* (exactly 3I
0
) and the calculated zero-sequence
current I
0
** (exactly 3I
0
) from the phase currents (see following figure). The protection range extends exclu-
sively over the transformer winding, including current transformer. The amount-adapted (compensated)
currents are described by the * symbol. They are normalized to the rated object current of the respective side.
In case of an internal ground fault, the residual currents flow to the fault location. With an external ground
fault, the fault current inverts itself in the phase current transformers. In this way, the direction of current flow
serves as the decisive criterion for an internal fault.
6.43.3
Protection and Automation Functions
6.43 Restricted Ground-Fault Protection
SIPROTEC 5, Overcurrent Protection, Manual 863
C53000-G5040-C017-8, Edition 07.2017
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