4.23
Date Code 20080213 Instruction Manual SEL-351A Relay
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control for Neutral-Ground and Residual-Ground Overcurrent Elements (Not in SEL-351A-1)
q From Ta b le 4 .2; w to Figure 4.15 and Figure 4.16.
Figure 4.11 Channel IN Current-Polarized Directional Element
Forward Threshold = (Channel I
N
Nominal Rating) • (Phase Channels Nominal Rating) • (0.05)
2
Forward Threshold:
Reverse Threshold = —(Channel I
N
Nominal Rating) • (Phase Channels Nominal Rating) • (0.05)
2
Reverse Threshold:
32IE is highest
w
R32I
(Reverse)
F32I
(Forward)
Best Choice
Ground
Directional
Logic
50GF
Enable
Forward
Threshold
32IE
Reverse
Threshold
50GR
q
Re[I
G
•I
N
*]
I
G
I
N
Relay
Word
Bits
Relay
Word
Bit
Relay
Word
Bit
Relay
Word
Bit
choice that is asserted
(I
G
= 3I
0
)
(Residual)
Courtesy of NationalSwitchgear.com