17
Requirements
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A CT according to ANSI/IEEE is specified in a little different way. For example a CT
of class C has a specified secondary terminal voltage U
ANSI
. There is a few standard-
ized value of U
ANSI
(e.g. for a C400 the U
ANSI
is 400 V). The rated equivalent limiting
secondary e.m.f. E
alANSI
for a CT specified according to ANSI/IEEE can be estimated
as follows:
(Equation 7)
The CT requirements are fulfilled if:
(Equation 8)
Often an ANSI/IEEE CT also has a specified knee-point voltage U
kneeANSI
. This is
graphically defined from the excitation curve. The knee-point according to ANSI/IEEE
has normally a lower value than the knee-point according to BS. The rated equivalent
limiting secondary e.m.f. E
alANSI
for a CT specified according to ANSI/IEEE can be
estimated to:
(Equation 9)
The current transformers must have a knee-point voltage U
kneeANSI
that fulfills the fol-
lowing:
where
Z
bANSI
The impedance (i.e. complex quantity) of the standard ANSI burden for the specific C
class (
Ω)
U
ANSI
The secondary terminal voltage for the specific C class (V)
E
alANSI
20
I
sn
R
CT
U
ANSI
+
⋅
⋅
20
I
sn
R
CT
20
I
sn
Z
bANSI
⋅
⋅
+
⋅
⋅
=
=
E
alANSI
maximum of E
alreq
>
E
alANSI
1.3 U
kneeANSI
⋅
≈
1.3 U
kneeANSI
maximum of E
alreq
>
⋅
Содержание REO 517
Страница 10: ... RQWHQWV ...
Страница 16: ...6 Introduction to the application manual KDSWHU QWURGXFWLRQ ...
Страница 64: ...54 Blocking of signals during test KDSWHU RPPRQ IXQFWLRQV ...
Страница 88: ...78 Scheme communication logic ZCOM KDSWHU LQH LPSHGDQFH ...
Страница 100: ...90 Time delayed phase and residual overcurrent protection TOC1 KDSWHU XUUHQW Equation 36 Iset IsSEC I1b 100 ...
Страница 146: ...136 Unbalance protection for capacitor banks TOCC KDSWHU XUUHQW ...
Страница 166: ...156 Dead line detection DLD KDSWHU 3RZHU V VWHP VXSHUYLVLRQ ...
Страница 171: ...161 About this chapter KDSWHU RQWURO KDSWHU RQWURO ERXW WKLV FKDSWHU This chapter describes the control functions ...
Страница 293: ...283 About this chapter KDSWHU RJLF KDSWHU RJLF ERXW WKLV FKDSWHU This chapter describes the logic functions ...
Страница 378: ...368 Monitoring of DC analog measurements KDSWHU 0RQLWRULQJ ...
Страница 379: ...369 About this chapter KDSWHU 0HWHULQJ KDSWHU 0HWHULQJ ERXW WKLV FKDSWHU This chapter describes the metering functions ...
Страница 384: ...374 Pulse counter logic PC KDSWHU 0HWHULQJ ...
Страница 412: ...402 Serial communication modules SCM KDSWHU DWD FRPPXQLFDWLRQ ...
Страница 440: ...430 LED indication module KDSWHU DUGZDUH PRGXOHV ...