Setting Guidelines - ABB Relion REC670 Applications Manual

Section 7
Current protection
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 2nd harmonic content. This can be used to avoid
unwanted operation of the protection. Therefore, OC4PTOC 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.
The phase overcurrent protection is often used as protection for two and three phase short
circuits. In some cases it is not wanted to detect single-phase earth faults by the phase
overcurrent protection. This fault type is detected and cleared after operation of earth fault
protection. Therefore it is possible to make a choice how many phases, at minimum, that have
to have current above the pick-up level, to enable operation. If set
high current in one phase only. If set
7.2.3

Setting guidelines

The parameters for the directional phase overcurrent protection, four steps OC4PTOC are set
via the local HMI or PCM600.
The following settings can be done for OC4PTOC.
GlobalBaseSel : Selects the global base value group used by the function to define ( IBase ),
UBase ) and ( SBase ).
(
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 On or Off .
AngleRCA : Protection characteristic angle set in degrees. If the angle of the fault loop current
has the angle RCA, the direction to the fault is forward.
AngleROA : Angle value, given in degrees, to define the angle sector of the directional function,
shown in Figure 43.
StartPhSel : Number of phases, with high current, required for operation. The setting
possibilities are:
IMinOpPhSel : Minimum current setting level for releasing the directional start signals in % of
IB . This setting should be less than the lowest step setting. The default setting is 7% of IB .
2ndHarmStab : Operate level of 2nd harmonic current restrain set in % of the fundamental
current. The setting range is
106
2 of 3 or 3 of 3 single-phase earth faults are not detected.
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.
1 out of 3 , 2 out of 3 and 3 out of 3 . The default setting is 1 out of 3 .
5 - 100 % in steps of 1%. The default setting is 20%.
1MRK 511 358-UEN A
1 of 3 it is sufficient to have
Application manual
IP14982-1 v1
M12982-4 v14