Restricted Ground-Fault Protection
Overview of Functions
The Restricted ground-fault protection function (ANSI 87N):
•
Detects ground faults in transformers, shunt reactors, neutral reactors or rotating machinery in which the
neutral point is grounded.
•
Has high sensitivity to ground faults near the neutral point.
•
Is supplemental main protection to longitudinal differential protection.
•
Protects grounding transformers in the protection range. It is required that a current transformer be used
in the case of neutral point feed, that is, between neutral point and grounding conductor. The neutral
point transformer and the phase current transformer define the protection range.
•
Adapts itself to the highest-amperage side with auto transformers and thereby prevents overfunction in
the event of external ground faults.
Structure of the Function
The Restricted ground-fault protection function is used in the Transformer side or Auto transformer
protection function group. Furthermore, you can use the function in the stabilizing winding of the auto trans-
former or also in the Standard UI function. The function depends upon application in the corresponding appli-
cation template preconfigured by the manufacturer or can be copied during the engineering into the corre-
sponding function group.
The Restricted ground-fault protection function is stepless.
[dwstrupt-170712-01.tif, 2, en_US]
Figure 6-263 Structure/Embedding of the Function
6.43
6.43.1
6.43.2
Protection and Automation Functions
6.43 Restricted Ground-Fault Protection
862 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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