Siemens SIPROTEC 4 7SJ61 - Accuracy limiting factors

Accuracy limiting factors
Betriebs- und Nennüberstromziffer
Required minimum effective accuracy limiting
factor
but at least 20
mit
n' Minimum effective accuracy limiting factor
Ι>>
Anr
Primary pickup value of the high-current
element
Ι
pN
Primary nominal transformer current
Resulting rated accuracy limiting factor
with
K
ALF
Rated accuracy limiting factor
R
BC
Connected burden resistance (device and
cables)
R
BN
Nominal burden resistance
R
Ct
Transformer internal burden resistance
Calculation example according to IEC 60044–1
Ι
sNom
= 1 A
K
ALF
= 20
R
BC
= 0.6 Ω (device and cables)
R
Ct
= 3 Ω
R
BN
= 5 Ω (5 VA)
K
ALF
set to 10,
so that: 5P10, 5 VA
mit
Ι
sNom
= secondary transformer nominal current
D.1
Current Transformer Requirements
D.1 Accuracy limiting factors
370 SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016