ABB REG670 Applications Manual

are to be detected with the selected CT ratio. It should also be verified that the
maximum possible fault current is within the limits of the IED.
The current error of the current transformer can limit the possibility to use a very
sensitive setting of a sensitive residual overcurrent protection. If a very sensitive
setting of this function will be used it is recommended that the current transformer
should have an accuracy class which have an current error at rated primary current that
is less than ±1% (for example, 5P). If current transformers with less accuracy are used
it is advisable to check the actual unwanted residual current during the
commissioning.
24.1.6 Rated equivalent secondary e.m.f. requirements
With regard to saturation of the current transformer all current transformers of high
remanence and low remanence type that fulfill the requirements on the rated
equivalent limiting secondary e.m.f. E
al
below can be used. The characteristic of the
non remanence type CT (TPZ) is not well defined as far as the phase angle error is
concerned. If no explicit recommendation is given for a specific function we therefore
recommend contacting ABB to confirm that the non remanence type can be used.
The CT requirements for the different functions below are specified as a rated
equivalent limiting secondary e.m.f. E
al
according to the IEC 61869-2 standard.
Requirements for CTs specified according to other classes and standards are given at
the end of this section.
24.1.6.1 Guide for calculation of CT for generator differential protection
This section is an informative guide describing the practical procedure when
dimensioning CTs for the generator differential protection IED. Two different cases
are of interest. The first case describes how to verify that existing CTs fulfill the
requirements in a specific application. The other case describes a method to provide
CT manufacturers with necessary CT data for the application. Below is one example
for each case.
~
GDP
Ext fault
CT1 CT2
I
tf
I
tf
IEC11000215-1-en.vsd
IEC11000215 V1 EN
1MRK 502 071-UEN - Section 24
Requirements
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 747
Application manual

ABB REG670 Specifications

General

Brand	ABB
Model	REG670
Category	Protection Device
Language	English