ABB RELION REX640 Technical Manual page 968

Section 4
Protection functions
962
I_A
I_B
I3P
I_C
I
1
U_AB
U_BC
U3P
U_CA
U
1
BLOCK
GUID-4C8DED4D-A6AC-4130-8DDB-55683D928577 V1 EN
Figure 520: Functional module diagram
Power calculation
This module calculates the apparent power based on the selected voltages and
currents. The Measurement mode setting determines which voltages and currents are
used. It is also possible to use positive-sequence components for calculating the
apparent power which makes the determination of power insensitive to a possible
asymmetry in currents or voltages and corresponds to the real load on the prime mover
of the generator.
Table 899: Power calculation
Measurement mode setting
PhsA, PhsB, PhsC
Arone
Pos Seq
PhsAB
PhsBC
PhsCA
Table continues on next page
Level
detector
Power
calculation
Directional
calculation
Power calculation
S U I
=
P
Re
=
S U
=
P Re
=
S 3
= ⋅
P Re
=
S
=
P Re
=
S
=
P Re
=
S
=
P Re
=
1MRS759142 C
Timer
OPERATE
t
START
* * *
U I U I
⋅ + + + ⋅
a a b b c c
S
( )
* *
I U I
⋅ − ⋅
ab a bc c
S
( )
*
U I
⋅
1 1
S
( )
* *
U I I
3
( )
⋅ ⋅ −
ab
a b
S
( )
* *
3 U I I
( )
⋅ ⋅ −
bc
b c
S
( )
* *
3 U I I
( )
⋅ ⋅ −
ca
c a
S
( )
Technical Manual
REX640