ABB RELION REX640 Technical Manual page 1057

1MRS759142 F
Power calculation
This module calculates the apparent power based on the selected voltage and
current measurements as described in
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
PhsA, PhsB, PhsC
Arone
Pos Seq
PhsAB
PhsBC
PhsCA
PhsA
PhsB
Table continues on the next page
REX640
Technical Manual
Table 991 Measurement mode setting
. The
Power calculation
. .
* *
S U I U I

a a b b
( )
P Re S
=
*
S U I U I
= ⋅ − ⋅
ab a bc c
( )
P Re S
=
*
S U I
3
= ⋅ ⋅
1 1
( )
P Re S
=
(
*
S U I I
= 3 ⋅ ⋅ −
ab
a
( )
P Re S
=
(
*
S 3 U I I
= ⋅ ⋅ −
bc
b
( )
P Re S
=
(
*
S U I I
= 3 ⋅ ⋅ −
ca
c
( )
P Re S
=
*
S 3 U I
= ⋅ ⋅
a a
( )
P Re S
=
*
S U I
3
= ⋅ ⋅
b b
Protection functions
.
*
U I
c c
*
)
*
b
)
*
c
)
*
a
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