Siemens SIPROTEC 7UT63 series User Manual

A Appendix
540
7UT613/63x Manual
C53000-G1176-C160-2
Current Transform-
er in accordance
with
BS 3938/IEC 60044-
1 (2000)
The values of an IEC class P transformer can be converted to the values for an IEC
class PX (BS class X) transformer by using the following formula:
Example: IEC 60044: 600/1, 5P10, 15VA, R
ct
= 4 Ω
IEC PX or BS class X:
Current Transform-
er 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
s.t.max
= 20 • 5A • R
b
• K
ssc
/20
with:
R
b
= P
b
/I
sn
2
and I
sn
= 5A
one derives at
U
s.t.max
= P
b
• K
ssc
/5A
Example: IEC 60044: 600/5, 5P20, 25VA
ANSI C57.13:
U
s.t.max
= 25VA • 20/5A = 100V, in accordance with class C100
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.
Relay type transient
dimensioning factor K
td
minimum required factor
K'
SSC
min. required
kneepoint voltage
7UT613/63x Transf.
3
BB/line
3
Gen./Motor
5

Siemens SIPROTEC 7UT63 series Specifications

General

Brand	Siemens
Model	SIPROTEC 7UT63 series
Category	Protection Device
Language	English