2 Functions
132
7UM61 Manual
C53000-G1176-C127-3
Figure 2-46
Logic Diagram of 100% Stator Earth Fault Protection
2.21.2 Setting Notes
General
The 90% stator earth fault protection is only fully effective and available if address
150
S/E/F PROT.
is set to
directional
,
non-dir. U0
or
non-dir. U0&I0
during
configuration. If
non-dir. U0
was selected, the parameters affecting the earth
current are not displayed. If one of the options
directional
or
non-dir. U0&I0
was selected, the parameters affecting the earth current are accessible. For machines
in busbar connection, one of the latter options must enabled since differentiation
between a power system earth fault and a machine earth fault is only possible by way
of the earth current. If used as "earth current differential protection", address
150
S/E/F PROT.
=
non-dir. U0&I0
is set. If the function is not required
Disabled
is set. Address
5001
S/E/F PROT.
serves to switch the function
ON
or
OFF
or to block
only the trip command (
Block relay
).
Displacement
Voltage
The criterion for the occurrence of an earth fault in the stator circuit is the emergence
of a neutral displacement voltage. Exceeding the set value
5002
U0>
therefore
causes pickup for stator earth protection.
The setting must be chosen such that the protection does not pick up because of op-
erational asymmetries. This is particularly important for machines in busbar connec-
tion since all voltage asymmetries of the network affect the voltage starpoint of the ma-
chine. The pickup value should be at least twice the value of operational asymmetry.
A value between 5% and 10% of the full displacement value is normal.
For machines in unit connection, the pickup value has to be chosen such that displace-
ments during network earth faults which affect the stator circuit via the coupling capac-
itances of the unit transformer, do not lead to pickup. The damping effect of the loading
resistor must also be considered here. Instructions for the dimensioning the loading
resistor are given in the publication "Planning Machine Protection Systems", Order
No. E50400- U0089-U412-A1-7600. The setting value is twice the displacement
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Содержание Siprotec 7UM611
Страница 16: ...Contents 16 7UM61 Manual C53000 G1176 C127 3 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 232: ...2 Functions 232 7UM61 Manual C53000 G1176 C127 3 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 292: ...3 Mounting and Commissioning 292 7UM61 Manual C53000 G1176 C127 3 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 410: ...A Appendix 410 7UM61 Manual C53000 G1176 C127 3 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 412: ...Literature 412 7UM61 Manual C53000 G1176 C127 3 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...