ABB RELION REX640 - Page 1057

Power calculation
This module calculates the apparent power based on the selected voltage and
current measurements as described in Table 991 . The Measurement mode setting
determines which voltage and current measurements are to be used.
It is also possible to use positive-sequence components for calculating apparent
power, which makes the determination of power insensitive to the possible
asymmetry in currents or voltages and corresponds to the real load of the prime
mover of the generator. S¯¯‾s‾
Table 991: Power calculation
Measurement mode setting Power calculation
PhsA, PhsB, PhsC
S U I U I U I
a a b b c c
+
*
. .
* *
.
P S=
( )
Re
Arone
S U I U I
ab a bc c
= ⋅ − ⋅
* *
P S=
( )
Re
Pos Seq
S U I= ⋅ ⋅3
1 1
*
P S=
( )
Re
PhsAB
S U I I
ab a b
= ⋅ ⋅ −
( )
3
* *
P S=
( )
Re
PhsBC
S U I I
bc b c
= ⋅ ⋅ −
( )
3
* *
P S=
( )
Re
PhsCA
S U I I
ca c a
= ⋅ ⋅ −
( )
3
* *
P S=
( )
Re
PhsA
S U I
a a
= ⋅ ⋅3
*
P S=
( )
Re
PhsB
S U I
b b
= ⋅ ⋅3
*
Table continues on the next page
1MRS759142 F Protection functions
REX640
Technical Manual
1057