Principle Of Operation - ABB Relion 670 Series Technical Reference Manual

1MRK505222-UUS C
6.14.2
Technical reference manual

Principle of operation

Automatic switch onto fault logic, voltage and current based function (ZCVPSOF) can
be activated externally by Breaker Closed Input or internally (automatically) by using
VI Level Based Logic see figure 196.
The activation from the Dead line detection function is released if the internal signal
deadLine from the VILevel function is activated at the same time as the input ZACC is
not activated during at least for a duration tDLD and the setting parameter AutoInit is
set to Enabled.
When the setting AutoInit is Disabled, the function is activated by an external binary
input BC. To get a trip one of the following operation modes must also be selected by
the parameter Mode:
Mode = Impedance; trip is released if the input ZACC is activated (normal connected
to non directional distance protection zone).
Mode = VILevel; trip is released if VILevel detector is activated.
Mode = VILvl&Imp; trip is initiated based on impedance measured criteria or VILevel
detection.
The internal signal deadLine from the VILevel detector is activated if all three phase
currents and voltages are below the setting IPhPickup and UVPickup.
VI Level based measurement detects the switch onto fault condition even though the
voltage is very low. The logic is based on current and voltage levels. The internal
signal SOTF VILevel is activated if a phase voltage is below the setting UVPickup and
corresponding phase current is above the setting IPhPickup longer than the time
tDuration.
ZCVPSOF can be activated externally from input BC and thus setting AutoInit is
bypassed.
The function is released during a settable time tSOTF.
The function can be blocked by activating the input BLOCK.
Section 6
Impedance protection
369