ABB Relion 670 Series Applications Manual page 165

1MRK 505 370-UUS Rev. K
inverse time characteristics are available: IEC and ANSI. It is also possible to programme a user defined
inverse time characteristic.
Normally it is required that the phase overcurrent function shall reset as fast as possible when the current
level gets lower than the operation level. In some cases some sort of time delayed reset is required.
Therefore three different kinds of reset time characteristics can be used.
For some protection applications there can be a need to change the current pick-up level for some time.
A typical case is when the protection will measure the current to a large motor. At the start up sequence
of a motor the start current can be significantly larger then the rated current of the motor. Therefore there
is a possibility to give a setting of a multiplication factor to the current pick-up level. This multiplication
factor is activated from a binary input signal to the function.
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 second harmonic content. This can be used to avoid unwanted operation of the protection.
Therefore the Four step phase overcurrent protection (OC4PTOC, 51/67) function have a possibility of
second harmonic restrain if the level of this harmonic current reaches a value above a set percentage of
the fundamental current.
7.2.4 Setting guidelines
The parameters for the four step phase overcurrent protection function (OC) are set via the local HMI or
Protection and Control IED Manager (PCM 600).
Common base IED values for the primary current (IBase), primary voltage (VBase) and primary power
(SBase) are set in global base values for settings function GBASVAL.
GlobalBaseSel: Selects the global base value group used by the function to define IBase, VBase and
SBase. Note that this function will only use IBase value.
The following settings can be done for the four step phase overcurrent protection.
Operation: Off/On
IBase: Base current in primary A. This current is used as reference for current setting. It can be suitable
to set this parameter to the rated primary current of the protected object.
2ndHarmStab: Operate level of 2
setting range is 5-100% of IBase in steps of 1%. Default setting is 20%.
HarmRestrainx: Disabled/Enabled, enables blocking from harmonic restrain.
7.2.4.1 Settings for each step (x = 1-4)
Characteristx: Selection of time delay characteristic for step x. Definite time delay and different types of
inverse time delay characteristics are available according to table 28.
Busbar protection REB670
Application manual
A typical starting time delay of 24ms is subtracted from the set trip time delay, so that the
resulting trip time will take the internal IED start time into consideration.
nd
harmonic current restrain set in % of the fundamental current. The
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Section 7
Current protection
SEMOD127939-1 v1
SEMOD127941-4 v4
SEMOD127941-18 v5
159