Figure 4.4-3 The dead-line detection logic
If any of the two criteria is fulfilled, 3POLE_OPEN signal is activated.
When PTS_Chk_Mod signal is 1, the voltage and current in any phase are below the
respective set values of PTS_NoUL and 0.04In.
When PTS_Chk_Mod signal is 0, the current in any phase is below the value of 0.04In and
the position of min CB is open, that is to say, PTS_Chk_Mod signal is 0.
This prevents the blocking of the impedance protection by fuse failure detection during the
dead-line condition. This also occurs during single pole auto-reclosing. The drop-off timer prolongs
the dead-line condition after the line energization to prevent the blocking of the impedance
protection for unequal pole closing. The time is decided by the set value PTS_3PO_Reset_T.
Fuse failure criteria
The fuse failure based on positive-sequence criterion is detected if the measured positive
sequence voltage is less than the set PTS_NoU1 value as 3POLE_OPEN signal is deactivated.
The fuse failure based on negative-sequence criterion is detected if the measured negative
sequence voltage exceeds the set PTS_U2 value and the measured negative-sequence current is
below the set PTS_I2 value.
If the positive-sequence criterion or the negative-sequence criterion is fulfilled, VT_InsAlm output
signal is activated instantly to block all the voltage-related functions. VT_Alm output signal is
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