ABB RELION REX640 Technical Manual page 592

Section 4
Protection functions
586
RED 615
400A/1
33kV

1 1 . 500 kVA

I
F
 
3 33 kV . 0
 
96 . 23 A

I * 1A
 

400 A
 
GUID-77AD6F06-C112-481C-BF8C-7F2ADBE4DD3E V1 EN
Figure 325: Influence of the short circuit current at LV side of the tapped
transformer to the differential current
Detection of the inrush current during transformer start-up
When the line is energized, the transformer magnetization inrush current is seen as
differential current by the line differential protection and may cause malfunction of
the protection if not taken into account. The inrush situation may only be detected on
one end but the differential current is always seen on both ends. The inrush current
includes high order harmonic components which can be detected and used as the
blocking criteria for the stabilized stage. The inrush detection information is changed
between two ends so that fast and safe blocking of the stabilized stage can be issued
on both ends.
500kVA
Z=10%

96 . 23 A
10
 
. 0 24 A 24 %
1MRS759142 C
RED 615
400A/1
REX640
Technical Manual