Idmt Zero Sequence Overcurrent Protection; Directional Element For Zero Sequence Overcurrent Protection - NR Electric PCS-9611 Instruction Manual

"50/51Gx.Dir" (x: 1~4) denotes the status of the zero sequence directional element, see
Section 3.5.3 for more details about the directional element;
"50/51Gx.HmBlk" (x: 1~4) denotes the status of the harmonic blocking element, see Section
3.5.4 for more details about the harmonic blocking element.

3.5.2 IDMT Zero Sequence Overcurrent Protection

The stage 3 and 4 zero sequence overcurrent protections also can be used as zero sequence
inverse definite minimum time (IDMT) overcurrent protection. They have the same inverse time
characteristic with the IDMT overcurrent protection (see Section 3.3.2), and the setting
[50/51Gx.Opt_Curve] (x: 3 or 4) can be used to select the expected curve.
The logic diagram of the No.1 stage 4 zero sequence IDMT overcurrent protection is shown as
below. The zero sequence overcurrent block is a level detector that detects whether the current
magnitude is above the threshold.
I > [50/51G4.3I0_Set]
01
50/51G4.Dir
50/51G4.HmBlk
[50/51G4.En]
[50/51G4.En1]
[50/51G4.Opt_Curve] = 0
[50/51G4.Blk]
Figure 3.5-2 Logic diagram of the No.1 stage 4 IDMT ROC protection
Where:
[50/51G4.3I0_Set] is the current setting of the No.1 stage 4 ROC protection;
[50/51G4.En] is the logic setting of the No.1 stage 4 ROC protection;
[50/51G4.En1] is the binary signal for enabling the No.1 stage 4 ROC protection;
[50/51G4.Blk] is the binary signal for blocking the No.1 stage 4 ROC protection;
[50/51G4.Opt_Curve] is the setting for selecting the inverse time characteristic curve;
"50/51G4.Dir" denotes the status of the zero sequence directional element for the No.1 stage
4 zero sequence overcurrent protection, see Section 3.5.3 for more details about the
directional element;
"50/51G4.HmBlk" denotes the status of the harmonic blocking element for the No.1 stage 4
zero sequence overcurrent protection, see Section 3.5.4 for more details about the harmonic
blocking element.
The stage 3 zero sequence overcurrent protection has the same logic diagram with the stage 4
zero sequence overcurrent protection, but the operation threshold is its own setting threshold.

3.5.3 Directional Element for Zero Sequence Overcurrent Protection

The residual voltage is used to polarize the directional earth fault (DEF) protection. With earth
PCS-9611 Feeder Relay
&
IDMT
&
Date: 2014-04-08
3 Operation Theory
[50/51G4.St]
[50/51G4.Op]
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