3-60 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Power Elements Logic Operation
_
+
_
+
_
+
_
+
|V
A
|
10 V sec
|I
A
|
0.1
×
I
nom
|V
A
|
40 V sec
|I
A
|
0.01
×
I
nom
_
+
2-cycle
average
Phase A
Reactive Power
2-cycle
average
Phase A
Real Power
Switch in this
position if
PWRnT =
+WATTS, -WATTS
multiply by -1
×
(-I)
Switch in this
position if
PWRnT =
+VARS , -VARS
Switch in this
position if
PWRnT =
+WATTS, +VARS
Switch in this
position if
PWRnT =
-WATTS , -VARS
Single-phase VA sec
Setting
PWRnP
PWRnD
0
Sufficient
Signal
Relay
Word
bit
PWRAn
n = 1, 2, 3, or 4
I
nom
= 1 A sec or 5 A sec
Repeat for Phases B and C
DWG: M351196
Figure 3.34: Power Elements Logic (+VARS Example Shown)
Courtesy of NationalSwitchgear.com
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