Setting Guidelines - ABB RET670 Applications Manual

Section 3
IED application
3.7.4.2
424
For some protection applications there can be a need to change the current pickup level
for some time. Therefore there is a possibility to give a setting of a multiplication
factor INxMult to the residual current pick-up level. This multiplication factor is
activated from a binary input signal MULTPUx to the function.
Power transformers can have a large inrush current, when being energized. This inrush
current can have residual current components. The phenomenon is due to saturation of
the transformer magnetic core during parts of the cycle. There is a risk that inrush
current will give a residual current that reaches level above the pickup current of the
residual overcurrent protection. The inrush current has a large second harmonic
content. This can be used to avoid unwanted operation of the protection. Therefore,
EF4PTOC (51N_67N) has a possibility of second harmonic restrain 2ndHarmStab if
the level of this harmonic current reaches a value above a set percentage of the
fundamental current.

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 the four step residual overcurrent protection, zero or negative
sequence direction EF4PTOC (51N/67N) are set via the local HMI or PCM600.
The following settings can be done for the four step residual overcurrent protection.
Operation: Sets the protection to Enabled or Disabled.
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
transformer where the current measurement is made.
VBase: Base voltage level in kV. This voltage is given as a phase-to-phase voltage and
this is the reference for voltage related settings of the function. The residual voltage is
used as reference voltage for the directional function. Normally the setting should be
chosen to the rated phase-to-phase voltage of the voltage transformer feeding the
protection IED.
Settings for each step (x = 1, 2, 3 and 4)
DirModeSelx: The directional mode of step x. Possible settings are Disabled/Non-
directional/Forward/Reverse.
1MRK504116-UUS C
Application manual