Micom P634 - Current Transformer Specifications; Symbols

2.13 Current Transformer Specifications
2.13.1 Symbols
The following symbols are used in accordance with IEC 61869 standards:
I
pn
Rated primary current (nominal primary current) of the CT
I
sn
Rated secondary current (nominal secondary current) of the CT
I
psc
Rated primary (symmetrical) short-circuit current
K
ssc
Rated symmetrical short-circuit current factor:
K
ssc
=
I
psc
I
pn
I
ref
Reference current of IDMT protection element
R
bn
Rated resistive burden (secondary connected) of the CT
P
bn
Equivalent power over the rated resistive burden of the CT for rated
secondary current:
P
bn
= R
bn
·I
sn
2
R
b
Actual resistive burden (secondary connected) of the CT
P
b
Equivalent power over the actual resistive burden of the CT for rated
secondary current:
P
b
= R
b
·I
sn
2
R
ct
Secondary winding resistance of the CT
P
ct
Equivalent power over the secondary winding resistance of the CT for
secondary rated current:
P
ct
= R
ct
·I
sn
2
V
sal
Secondary accuracy limiting voltage (e.m.f.) of the CT
V
k
Rated knee point voltage (e.m.f.) of the CT
n
n
Rated accuracy limit factor of the CT
n
b
Actual accuracy limit factor of the CT:
n
b
= n
n
·
R
ct
+ R
bn
R
ct
+ R
b
= n
n
·
P
ct
+ P
bn
P
ct
+ P
b
2 Technical Data P634
P634/EN M/R-42-A // P634‑311‑653 2-25