2.5 Restricted Earth Fault Protection (optional)
87
7SD610 Manual
C53000-G1176-C145-4
Note
When delivered from factory, the restricted earth fault protection is switched OFF. The
reason is that the protection must not be in operation unless at least the assigned side
and CT polarity have been properly set before. Without proper settings, the device
may show unexpected reactions (incl. tripping)!
The sensitivity of the protection is determined by the I-REF> setting (address 4111).
The earth fault current which flows through the starpoint lead of the transformer is de-
cisive. A further earth current which may be supplied from the network does not influ-
ence the sensitivity.
The set value can be increased in the tripping quadrant depending on the arithmetic
sum of the currents (stabilization by the sum of all current magnitudes) which is set
under address 4113 SLOPE. This parameter can only be altered in DIGSI at Addition-
al Settings. The preset value 0 is normally adequate.
For special applications, it may be advantageous to delay the trip command of the pro-
tection. This can be done by setting an additional delay time (address 4112 T I-
REF>). This parameter can only be altered in DIGSI at Additional Settings. Normally,
this additional delay time is set to 0. This setting is a pure delay time which does not
include the inherent operating time of the protection.
The value indication 5827 „REF S:“ is the restraining quantity resulting from the trip-
ping characteristic, and is not
identical with the measured value 30655
„IrestREF=“.
Value message 5826 „REF D:“ is the tripping value stabilized via the tripping curve.
The reported values „REF S:“ and „REF D:“ refer to the time when the output
message 5816 „REF T start“ is reported, i.e. the starting time of T I-REF> (ad-
dress 4112).
The following relations apply for calculating the quantities (see section 2.5 margin
heading „Evaluation of the measured quantities“):
REF S = |3I
0
'-3I
0
''| - |3I
0
'+3I
0
''|
REF D = |3I
0
'| for REF S ≤ 0
REF D = |3I
0
'| - k · REF S for EDS S > 0 (with k = 4)
2.5.4 Settings
Addresses which have an appended "A" can only be changed with DIGSI, under Ad-
ditional Settings.
The table indicates region-specific presettings. Column C (configuration) indicates the
corresponding secondary nominal current of the current transformer.
Addr. Parameter C Setting Options Default Setting Comments
4101 REF PROT. OFF
ON
OFF Restricted Earth Fault Pro-
tection
4111 I-REF> 1A 0.05 .. 2.00 A 0.15 A Pick up value I REF>
5A 0.25 .. 10.00 A 0.75 A
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