ABB RELION 650 SERIES, Руководство по применению

Страница: 252 / 262

a lANS I
S N CT ANS I S N CT S N bANS I
E
20 I R V 20 I R 20 I Z =
× × + = × × + × ×
EQUATION1682 V1 EN-US
(Equation 39)
where:
Z
bANSI
The impedance (that is, with a complex quantity) of the standard ANSI burden for the specific C class ( W )
V
ANSI
The secondary terminal voltage for the specific C class (V)
The CTs according to class C must have a calculated rated equivalent limiting secondary e.m.f.
E
alANSI
that fulfils the following:
alANSI alreq
E max imum of E
>
EQUATION1384 V1 EN-US
(Equation 40)
A CT according to ANSI/IEEE is also specified by the knee point voltage V
kneeANSI
that is graphically
defined from an excitation curve. The knee point voltage V
kneeANSI
normally has a lower value than
the knee-point e.m.f. according to IEC and BS. V
kneeANSI
can approximately be estimated to 75 % of
the corresponding E
al
according to IEC 61869-2. Therefore, the CTs according to ANSI/IEEE must
have a knee point voltage V
kneeANSI
that fulfills the following:
E
kneeANSI
>
0.75 · (maximum of E
alreq
)
EQUATION2101 V1 EN-US
(Equation 41)
The following guide may also be referred for some more application aspects of ANSI class CTs:
IEEE C37.110 (2007), IEEE Guide for the Application of Current Transformers Used for Protective
Relaying Purposes.
16.2 Voltage transformer requirements
M11608-3 v5
The performance of a protection function will depend on the quality of the measured input signal.
Transients caused by capacitive Coupled voltage transformers (CCVTs) can affect some
protection functions.
Magnetic or capacitive voltage transformers can be used.
The capacitive voltage transformers (CCVTs) should fulfill the requirements according to the IEC
61869-5 standard regarding ferro-resonance and transients. The ferro-resonance requirements of
the CCVTs are specified in chapter 6.502 of the standard.
The transient responses for three different standard transient response classes, T1, T2 and T3 are
specified in chapter 6.503 of the standard. CCVTs according to all classes can be used.
The protection IED has effective filters for these transients, which gives secure and correct
operation with CCVTs.
Section 16 1MRK 505 287-UUS B
Requirements
246 Busbar protection REB650
Application manual
© Copyright 2013 ABB. All rights reserved