PU 3I0 : Level of high zero sequence current detection given in % of IBase. This setting
should be based on fault calculations to find the zero sequence current in case of a fault at
the point on the protected line giving the smallest fault current to the protection. The zero
sequence current shall be calculated for different types of faults (single phase-to-
groundand phase to phase to ground) at different switching states in the network.
t3I0: Time delay of zero sequence overcurrent criterion. Default value 0.0 s is
recommended
Setting for low voltage criterion subfunction are described below.
OperationUV: Enabled/Disabled, is set Enabled for detection of faults by means of low
phase-to-ground or phase-to-phase voltage
V_Ph-N: Level of low phase-ground voltage detection, given in % of VBase. This setting
should be based on fault calculations to find the phase-ground voltage decrease in case of
a fault at the most remote point where the differential protection shall be active. The phase-
ground voltages shall be calculated for different types of faults (single phase-to-ground
and phase to phase to ground) at different switching states in the network. The setting must
be higher than the lowest phase-ground voltage during non-faulted operation.
V_Ph-Ph: Level of low phase-phase voltage detection, given in % of VBase. This setting
should be based on fault calculations to find the phase-phase voltage decrease in case of
a fault at the most remote point where the differential protection shall be active. The phase-
phase voltages shall be calculated for different types of faults (single phase to ground and
phase to phase to ground) at different switching states in the network. The setting must be
higher than the lowest phase-phase voltage during non-faulted operation.
tUV: Time delay of undervoltage criterion. Default value 0.0 s is recommended
Settings for low current criterion subfunction are described below.
Operation37: Enabled/Disabled, is set Enabled when tripping is preferred at energizing
of the line if differential does not behave correctly.
PU_37: Level of low phase current detection given in % of IBase. This setting shall detect
open line ends and be below normal minimum load.
tUC: Time delay of undercurrent criterion. Default value is recommended to verify that
the line is open.
1MRK 506 369-UUS - Section 7
Differential protection
Line distance protection REL670 2.2 ANSI 155
Application manual
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