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8.25
Date Code 20070117
Instruction Manual
SEL-351-5, -6, -7 Relay
Breaker Monitor, Metering, and Load Profile Functions
Demand Metering
Figure 8.13
Demand Current Logic Outputs
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 51GT. This is accomplished with
the following settings from
, pertinent residual ground overcurrent
element settings, and SEL
OGIC
control equation torque control setting
51GTC:
EDEM =
THM
DMTC =
5
GDEMP =
1.0
51GP =
1.50
50G5P =
2.30
51GTC =
GDEM + GDEM * 50G5
,
, and
PDEM
Relay
Word
Bits
Demand Current
Pickup Settings
(A Secondary)
I
B(DEM)
I
A(DEM)
I
A
I
C(DEM)
I
N(DEM)
Demand
Currents
Instantaneous
Currents
Serial Port
Command
Demand Function
Maximum
Phase
Demand
Current
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
Reset
Demand
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
NDEM
NDEMP
PDEMP
I
N
Demand Function
I
G(DEM)
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
GDEM
GDEMP
I
G
(residual)
Demand Function
3I
2(DEM)
Reset
Demand
Thermal (EDEM = THM)
or
Rolling (EDEM = ROL)
QDEM
QDEMP
3I
2
MET RD
Demand Function
Содержание SEL-351-5
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