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Settings for phase-phase current variation subfunction are described below.
OperationCV: On/Off, is set On in most applications
ICV>: Level of fixed threshold given in % of IBase. This setting should be based on fault
calculations to find the current increase in case of a fault at the point on the protected line
giving the smallest fault current to the protection. The phase current shall be calculated for
different types of faults (single phase-to-earth, phase-to-phase to earth, phase-to-phase and
three phase short circuits) at different switching states in the network. In case of switching of
large objects (shunt capacitor banks, transformers, and so on) large change in current can
occur. The
ICV> setting should ensure that all multi-phase faults are detected.
tCV: Time delay of zero sequence overcurrent criterion. Default value 0.002 s is recommended
Settings for zero sequence current criterion subfunction are described below.
Operation3I0: On/Off, is set On for detection of phase-to-earth faults with high sensitivity
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-earthand phase to
phase to earth) 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: On/Off, is set On for detection of faults by means of low phase-to-earth or
phase-to-phase voltage
UPhN<: Level of low phase-earth voltage detection, given in % of UBase. This setting should be
based on fault calculations to find the phase-earth voltage decrease in case of a fault at the
most remote point where the differential protection shall be active. The phase-earth voltages
shall be calculated for different types of faults (single phase-to-earth and phase to phase to
earth) at different switching states in the network. The setting must be higher than the lowest
phase-earth voltage during non-faulted operation.
UPhPh<: Level of low phase-phase voltage detection, given in % of UBase. 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 earth and phase to
phase to earth) 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.
OperationUC: On/Off, is set On when tripping is preferred at energizing of the line if
differential does not behave correctly.
IUC<: 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 505 343-UEN B
Section 6
Differential protection
143
Application manual
Summary of Contents for Relion 670 series
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