Schweitzer Engineering Laboratories SEL-351 - Page 59

Date Code 20001006 Installation 2-19
SEL-351 Instruction Manual
1. Voltage Channel VS does not need to be connected. It is used only in voltage and synchronism check elements
and voltage metering.
2. Current Channel IN does not need to be connected. Channel IN provides current I
N
for the neutral ground
overcurrent elements. Separate from Channel IN, the residual ground overcurrent elements operate from the
internally derived residual current I
G
(I
G
= 3I
0
= I
A
+ I
B
+ I
C
). But in this residual connection example, the neutral
ground and residual ground overcurrent elements operate the same because I
N
= I
G
.
Figure 2.9: SEL-351 Relay Provides Directional Overcurrent Protection and Reclosing for a
Transmission Line
Courtesy of NationalSwitchgear.com