Siemens SIPROTEC 4 7UT6 Series Manual page 525

[wdl-anf-vk-1, 1, en_GB]
Example: IEC 60044: 600/1, 5P10, 15VA, R
IEC PX or BS cass X:
[wdl-anf-vk-2, 1, en_GB]
Current Transformer in accordance with ANSI/IEEE C 57.13
Class C of this standard defines the CT by its secondary terminal voltage at 20 times rated current, for which
the ratio error shall not exceed 10%. Standard classes are C100, C200, C400 and C800 for 5A rated secondary
current.
The approximate terminal voltage can be derived from the IEC values, as follows:
ANSI transformer definition
U = 20 • 5A • R
s.t.max
mit:
R = P /Ι 2 and Ι
b b sn
one derives at
U = P • K
s.t.max b ssc
Example: IEC 60044: 600/5, 5P20, 25VA
ANSI C57.13:
U = 25VA • 20/5A = 100V, acc. to class C100
s.t.max
Relay type
dimensioning factor K
7UT6x Transf.
3
The calculations listed above are simplified in order to facilitate a quick and safe CT calculation/verification. An
accurate calculation/verification can be carried out with the Siemens CTDIM program as from V3.21. The
results of the CTDIM program have been released by the device manufacturer.
Mismatching factor for 7UT6x, (limited resolution of the measurement)
[wdl-anf-fadap, 1, en_GB]
where:
= rated current of the protected object
Ι
nO
(in relation to the parameterised rated current)
U = parameterised rated current of the protected object
nO
= nominal device current
Ι
Nrelay
S = maximum (rated) power of the protected object
Nmax
(for transformers: side with the largest (rated) load)
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
ct
• K /20
b ssc
= 5A
sn
/5A
Transient
td
BB/line Gen./Motor
3 5
= 4 Ω
Min. required factor
K'
SSC
Current Transformer Requirements
D.1 General Requirements
Min. required
kneepoint voltage
525