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Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
With the Blk. w. inrush curr. detect. parameter, you specify whether the operate is blocked during
detection of an inrush current.
Siemens recommends disabling the blocking. The fundamental component of the zero-sequence voltage is a
reliable criterion for the ground fault and remains unaffected by an enabling procedure.
Parameter: Directional mode
•
Default setting (_:106) Directional mode = forward
When a fault is detected, the selection of the parameter Directional mode defines whether the pickup of
the stage occurs in forward or reverse direction.
When the parameter Directional mode is set as non-directional, the direction determination is not
considered. The pickup condition depends only on the absolute values 3I0 and V0 and the respective thresh-
olds. The forward direction is the direction towards the motor.
Parameter: Rotation angle of ref. volt.,Forward section +/-
•
Default setting (_:104) Rotation angle of ref. volt. = -45°
•
Default setting (_:103) Forward section +/- = 88°
With the Rotation angle of ref. volt. and Forward section +/- parameters, you set the direc-
tion characteristic, that is, the areas of forward and reverse. With this, you set the direction characteristic
according to the system conditions and the neutral-point treatment.
Typical settings for the Rotation angle of ref. volt.parameter are:
•
Arc-suppression-coil-ground system: 0°
•
Isolated system: +45°
•
Grounded system: -45°
The Forward section +/- parameter can normally be left at its default setting. A reduction of the forward
area by a few degrees is practical, for example, in an arc-suppression-coil-ground system with long cable
feeders, that generate high capacitive fault currents.
Parameter: Min. V0> for dir. determ.
•
Default setting (_:102) Min. V0> for dir. determ. = 2.000 V
With the Min. V0> for dir. determ. parameter, you determine the minimum voltage V0 necessary for
the release of the direction determination that must be attained within the time delay Dir. determina-
tion delay.
Parameter: 3I0> threshold value
•
Default setting (_:101) 3I0> threshold value = 0.050 A
The 3I0> threshold value parameter allows you to set the ground-current sensitivity of the stage. Set
the threshold value lower than the minimum absolute value of the ground-fault current 3I0 that must still be
detected.
Parameter: Dir. determination delay
•
Default setting (_:105) Dir. determination delay = 0.10 s
The start of the ground fault normally shows a significant transient behavior. This can lead to an incorrect
direction decision. The direction determination can be delayed from the occurrence of the zero-sequence
voltage with the Dir. determination delay parameter to achieve steady-state measurands. The dura-
tion of the transient cycle is determined from the system conditions and the respective fault characteristics. If
you have no knowledge of a suitable time delay, Siemens recommends keeping the default setting.
Parameter: Operate delay
•
Default setting (_:6) Operate delay = 0.50 s
590
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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