Siemens SIPROTEC 7UT63 series - Page 438

4 Technical Data
438
7UT613/63x Manual
C53000-G1176-C160-2
Figure 4-3 Restraining influence of n-th harmonic in transformer differential protection
I
diff
differential current = |I
1
+ I
2
|
I
NObj
Nominal current of protected object
I
fN
Current at nominal frequency
I
nf
Current at n times the frequency (n = 3 or 4)
Figure 4-4 Frequency influence in transformer differential protection
I
diff
Differential current = |I
1
+ I
2
|
I
NObj
Nominal current of the protected object
I
Xf
Current at any frequency within specified range