ABB RET670 - Setting Guidelines

ground 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
1 of 3 it is sufficient to have high current in one phase only. If set 2 of 3 or 3 of 3 single-
phase ground faults are not detected.
3.7.2.2 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
of utmost importance to set the definite time delay for that stage to zero.
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).
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
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 current of the
protected object.
VBase: Base voltage level in kV. This voltage is give as a phase-to-phase voltage and
this is the reference for voltage related settings of the function. Normally the setting
should be chosen to the rated phase-to-phase voltage of the voltage transformer feeding
the protection IED.
AngleRCA: Protection characteristic angle set in degrees. If the angle of the fault loop
current has the angle RCA the direction to fault is forward.
AngleROA: Angle value, given in degrees, to define the angle sector of the directional
function, see figure
183.
PUMinOpPhSel: Minimum current for phase selection set in % of IBase. This setting
should be less than the lowest step setting. Default setting is 7%.
NumPhSel: Number of phases, with high current, required for operation. The setting
possibilities are: Not used,1 out of 3, 2 out of 3 and 3 out of 3. Default setting is 1 out
of 3.
1MRK504116-UUS C Section 3
IED application
403
Application manual