ABB RET670 - Application; Setting Guidelines

3.6.8.1 Application
The operation of transmission networks today is in many cases close to the stability
limit. Due to environmental considerations the rate of expansion and reinforcement of
the power system is reduced for example, difficulties to get permission to build new
power lines.
The ability to accurate and reliable classifying the different types of fault so that single
pole tripping and autoreclosing can be used plays an important roll in this matter.
Faulty phase identification with load encroachment for mho (FMPSPDIS) function is
designed to accurately select the proper fault loop in the Distance protection function
dependent on the fault type.
The heavy load transfer that is common in many transmission networks may in some
cases be in opposite to the wanted fault resistance coverage. Therefore, FMPSPDIS has
an built-in algorithm for load encroachment, which gives the possibility to enlarge the
resistive setting of both the Phase selection with load encroachment and the measuring
zones without interfering with the load.
The load encroachment algorithm and the blinder functions are always activated in the
phase selector. The influence from these functions on the zone measurement
characteristic has to be activated by switching the setting parameter LoadEnchMode
for the respective measuring zone(s) to Enabled.
3.6.8.2 Setting guidelines
IBase: IBase is normally set to the current value of the primary winding of the CT, but
can also be set to the rated current of the bay. It is by default set to 3000 A and shall be
adapted to the actual application.
VBase: VBase is set to the voltage value of the primary winding of the VT. It is by
default set to 400 kV and shall be adapted to the actual application.
INRelPG: The setting of INRelPG for release of the phase-to-ground loop is by default
set to 20% of IBase. The default setting is suitable in most applications.
The setting must normally be set to at least 10% lower than the setting of
3I0BLK_PPto give priority to open phase-to-ground loop. INRelPG must be above the
normal un-balance current (3I
0
) that might exist due to un-transposed lines.
The setting must also be set higher than the 3I
0
that occurs when one pole opens in
single pole trip applications.
3I0BLK_PP: The setting of 3I0BLK_PP is by default set to 40% of IBase, which is
suitable in most applications.
Section 3 1MRK504116-UUS C
IED application
312
Application manual