ABB Relion 650 Series Applications Manual page 78

Section 7
Current protection
overcurrent protections, 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.
Power transformers can have a large inrush current, when being energized. This phenomenon is
due to saturation of the transformer magnetic core during parts of the period. There is a risk that
inrush current will reach levels above the pick-up current of the phase overcurrent protection. The
inrush current has a large 2nd harmonic content. This can be used to avoid unwanted operation of
the protection. Therefore, OC4PTOC (51/67) have a possibility of 2nd harmonic restrain if the level
of this harmonic current reaches a value above a set percentage of the fundamental current.
7.1.3 Setting guidelines
The parameters for Four step phase overcurrent protection 3-phase output OC4PTOC (51/67) are
set via the local HMI or PCM600.
The following settings can be done for OC4PTOC (51/67).
GlobalBaseSel : Selects the global base value group used by the function to define ( IBase ), ( VBase )
SBase ).
and (
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 Disabled or Enabled
2ndHarmStab : Operate level of 2nd harmonic current restrain set in % of the fundamental current.
The setting range is
72
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.
5 - 100 % in steps of 1%. Default setting is 20%.
© Copyright 2013 ABB. All rights reserved
1MRK 505 287-UUS B
M12982-4 v9
Busbar protection REB650
Application manual