Technical description
7 Applications
7.4 Current Transformer Selection
VM265.EN011
VAMP 24h support phone +358 (0)20 753 3264
163
Formula to solve needed CT power SN
By replacing the complex power terms with corresponding
resistances in
Equation 7.4.2-2
L
W
CT
N
CT
ALF
A
R
R
R
R
R
k
k
where the nominal burden resistance is
2
sec
NCT
N
N
I
S
R
R
CT
= Winding resistance (See Figure 7.4.1-1)
R
W
= Wiring resistance (from CT to the relay and back)
R
L
= Resistance of the protection relay input
S
N
= Nominal burden of the CT
I
NCTsec
= Nominal secondary current of the CT
By solving S
N
and substituting k
A
according Equation 7.4.2-2 ,
we get
Equation 7.4.2-3
2
sec
NCT
CT
L
W
CT
NCT
ALF
NTra
SET
N
I
R
R
R
R
I
k
I
cI
S
Содержание 265
Страница 2: ...VM265 EN011...
Страница 214: ...11 Construction Technical description 214 VAMP 24h support phone 358 0 20 753 3264 VM265 EN011 11 Construction...
Страница 219: ...VM265 EN011...