Schweitzer Engineering Laboratories SEL-751 - Figure 4.2 Instantaneous Overcurrent Element Logic

4.14
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
q To Figure 4.41; w From Figure 4.35; e From Figure 4.34; r From Figure 4.40; t Residual Current Magnitude lIGl
is the calculated residual current. Not shown in the figure, Relay Word bit ORED50T is asserted if any of the 50PnT, 67PnT,
50NnT, 67NnT, 50GnT, 67GnT, 50QnT or 67QnT Relay Word bits are asserted (n = 1 to 4).
Figure 4.2 Instantaneous Overcurrent Element Logic
When For Trip For Pickup Nonfunctional
EDIR := Y or AUTO Use 67PnT, 67NnT, 67QnT,
and 67GnT
Use 67 Pn P, 67 N nP, 67 Qn P,
and 67GnP
50PnT, 50NnT, 50QnT, 50GnT,
50PnP, 50NnP, 50QnP, and 50GnP
EDIR := N or
a
a
When the directional control option is not ordered and EDIR is automatically set to N and hidden.
Use 50PnT, 50NnT, 50QnT,
and 50GnT
Use 50PnP, 50NnP, 50QnP,
and 50GnP
67PnT, 67NnT, 67Q nT, 67 GnT,
67 Pn P, 67N nP, 67Q nP, a n d 67 Gn P
IA
IB
IC
IN
PHROT
IG
Current
Magnitude
Calculations
Settings
|IP|
(Maximum Phase Current Magnitude)
|IN|
(Core-Balance Current Magnitude)
|IG|
(Residual Current Magnitude)
(Negative-Sequence Current Magnitude)
|3I2|
|IA|
(A-Phase Current Magnitude)
|IB|
(B-Phase Current Magnitude)
(C-Phase Current Magnitude)
|IC|
Negative-Sequence
Current Calculation
50P1TC
50P1P
|IA|
50A1P
50B1P
|IC|
50C1P
Relay
Word
Bits
|IB|
4
5
5
5
5
5
5
5
5
50PnP
67PnT/50PnT
50NnP
67NnT/50NnT
67NnP/50NnP
67PnP/50PnP
|IN|
|IP|
50PnTC
67QnT/50QnT
50GnP
67GnT/50GnT
67GnP/50GnP
|IG|
50QnP
|3I2|
50GnTC
50QnTC
67QnP/50QnP
50PnD
0
50GnD
0
50NnD
0
50QnD
0
PnDIR
1
GnDIR
3
50NnTC
NnDIR
2
QnDIR