Siemens SIPROTEC 7SK80 - Class Conversion; A.4.2 Class Conversion

Appendix
A.4 Current Transformer Requirements
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
425
A.4.2 Class conversion
Table A-1 Conversion into other classes
British Standard BS 3938
ANSI/IEEE C 57.13, class C
I
sNom
= 5 A (typical value)
IEC 60044-6 (transient response), class
TPS
Classes TPX, TPY, TPZ
K≈ 1
K
SSC
≈ K
ALF
Calculation See ChapterA.4.1 Accuracy limiting factors with: K
SSC
≈
K
ALF
T
P
depending on power system and specified closing sequence
with
V
k
Knee-point voltage
R
Ct
Internal burden resistance
R
BN
Nominal burden resistance
I
sNom
Secondary nominal transformer current
KALF Rated accuracy limiting factor
V
s.t.max
Sec. terminal voltage at 20 I
pNom
V
al
Sec. magnetization limit voltage
K Dimensioning factor
K
SSC
Factor syymetr. Rated fault curent
T
P
Primary time constant