ABB RELION 670 Series Applications Manual page 162

Section 7
Current protection
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.
7.2.3 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).
GlobalBaseSel : Selects the global base value group used by the function to define ( IBase ), ( VBase )
SBase ).
and (
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
The setting range is 5-100% of IBase in steps of 1%. Default setting is 20%.
HarmRestrainx : Disabled/Enabled , enables blocking from harmonic restrain.
7.2.3.1 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.
Table 28: Inverse time delay characteristics
Curve name
ANSI Extremely Inverse
ANSI Very Inverse
ANSI Normal Inverse
ANSI Moderately Inverse
ANSI/IEEE Definite time
ANSI Long Time Extremely Inverse
ANSI Long Time Very Inverse
Table continues on next page
156
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.
1MRK 505 337-UUS A
SEMOD127939-1 v1
SEMOD127941-4 v4
SEMOD127941-18 v4
Application manual