Siemens 7SC80 - Accuracy Limiting Factors

Accuracy limiting factors
Effective and Rated Accuracy Limiting Factor
Required minimum effective accuracy limiting
factor
but at least 20
with
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
with
Ι
sNom
= secondary transformer nominal current
D.1
Current Transformer Requirements
D.1 Accuracy limiting factors
606 SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017