ABB REQ650 User Manual

current of the phase overcurrent protection. The inrush current has a large second
harmonic content. This can be used to avoid the unwanted operation of the protection.
Therefore, OC4SPTOC (51/67) function has a possibility of a second harmonic
restrain if the level of this harmonic current reaches a value above a set percentage of
the fundamental current.
Choice of delay time characteristics: There are several types of delay time
characteristics available such as definite time delay and different types of inverse time
delay characteristics. The selectivity between different overcurrent functions is
normally enabled by co-ordination between the function time delays of the different
functions. To enable optimal co-ordination between all overcurrent functions, they
should have the same time delay characteristic. Therefore a wide range of
standardized inverse time characteristics are available: IEC and ANSI.
The time characteristic for step 1 and 4 can be chosen as definite time delay or inverse
time characteristic. Step 2 and 3 are always definite time delayed and are used in
system where IDMT is not needed.
6.4.3 Setting guidelines
When inverse time overcurrent characteristic is selected, the operate
time of the stage will be the sum of the inverse time delay and the set
definite time delay. Thus, if only the inverse time delay is required, it
is important to set the definite time delay for that stage to zero.
The parameters for four step phase overcurrent protection phase segregated output
OC4SPTOC are set via the local HMI or Protection and Control IED Manager
(PCM600).
The following settings can be made for the four step phase overcurrent protection
phase segregated output.
Common base IED values for primary current (setting IBase), primary voltage
(UBase) and primary power (SBase) are set in a Global base values for settings
function GBASVAL.
Setting GlobalBaseSel: Used to select a GBASVAL function for reference of base
values.
MeasType: Selection of discrete Fourier filtered (DFT) or true RMS filtered (RMS)
signals. RMS is used when the harmonic contents are to be considered, for example in
applications with shunt capacitors.
Operation: The protection can be set to Off or On
HarmRestrain: Off or On, enables blocking from harmonic restrain.
1MRK 505 291-UEN A Section 6
Current protection
105
Application manual

ABB REQ650 Specifications

General

Brand	ABB
Model	REQ650
Category	Protection Device
Language	English