Setting Notes - Siemens SIPROTEC 7SD610 Manual

Functions
2.5 Restricted Earth Fault Protection (optional)
Figure 2-34 Logic diagram of the restricted earth fault protection (simplified)
2.5.3

Setting Notes

General
The restricted earth fault protection can only operate if this function has been set during configuration of the
functional scope (Section 2.1.1.2) under address 141 REF PROT. on Enabled. Operation requires the
address 143 TRANSFORMER to be set on YES and the address 220 I4 transformer on IY starpoint.
The address 221 I4/Iph CT must be set under margin heading „Connection of the Currents" as described in
section 2.1.2.1.
The earth fault differential protection can be activated (ON) or deactivated (OFF) under address 4101 REF
PROT..
Note
When delivered from factory, the restricted earth fault protection is switched OFF. The reason is that the pro-
tection 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> (address 4111). This is the earth fault current
that flows through the starpoint lead of the transformer. Any other earth current which may be supplied from the
network does not influence the sensitivity.
The set pickup value can be additionally increased in the tripping zone (stabilization by the sum of all current
magnitudes) which is set at address 4113 SLOPE. This setting can only be made in DIGSI under Display Ad-
ditional Settings. The default value 0 is usually adequate.
For special applications, it may be advantageous to delay the trip command of the protection. This can be done
by setting an additional delay time (address 4112 T I-REF>). This setting can only be made in DIGSI under
Display Additional Settings. Normally, this additional delay is set to 0. This setting value is an additional delay
time which does not include the inherent measuring time of the protection function.
The value indication 5827 „REF S:" is the restraining quantity resulting from the tripping characteristic, and
is not identical with the measured value 30655 „IrestREF=".
88
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011