CYG PRS-7367 - Page 211

Protection Functions
PRS-7367 203
I0neu
*
*
REF
*
*
I0cal=Ia+Ib+Ic
A
B
C
Ia
Ib
Ic
Figure 3.42-1 REF principle diagram
3.42.2.4 Operation Criterion
The operation criteria of REF protection are as follows:










00
00
00
*
/4
d cdqd
dr
Neu cdqd
II
I K I
II
Where:

0 0 0 d Cal Neu
I I I
,
 

0 0 0
max ,
r Cal Neu
I I I
.
0
Cal
I
、
0
Neu
I
are respectively residual current of the
phase currents and neutral measured current. For this device, the ratio restrained coefficient
fixedly takes 0.6.