Schweitzer Engineering SEL-351P - Demand Current Logic Output Application - Raise Pickup for Unbalance Current

Date Code 990215 Breaker/Recloser Monitor, Battery System Monitor, 8-27
Metering, and Load Profile Functions
SEL-351P Manual Técnico
Demand Current Logic Output Application – Raise Pickup for Unbalance Current
During times of high loading, the residual ground overcurrent elements can see relatively high
unbalance current I
G
(I
G
= 3I
0
). To avoid tripping on unbalance current I
G
, use Relay Word bit
GDEM to detect the residual ground (unbalance) demand current I
G(DEM)
and effectively raise the
pickup of the residual ground time-overcurrent element 51G1T. This is accomplished with the
following settings from
Table SECTION 8: .5, pertinent residual ground overcurrent element
settings, and SEL
OGIC Control Equation torque control setting 51G1TC:
EDEM = THM
DMTC = 5
GDEMP = 1.0
51G1P = 1.50
50G5P = 2.30
51G1TC = !GDEM + GDEM * 50G5
Refer to
Figure SECTION 8: .11, Figure SECTION 8: .12, and Figure 3.19.
Figure SECTION 8: .12: Raise Pickup of Residual Ground Time-Overcurrent
Element for Unbalance Current