ABB RED650, Applications Manual

Page: 143 / 454

( )
1
5.3 35.7
SB
Z j
= + W
EQUATION1330 V1 EN-US
Positive sequence source impedance behind B bus
max
1000 S MVA
=
EQUATION1331 V1 EN-US
Maximum expected load in direction from A to B (with minimum
system operating voltage U
min
)
( )
max
cos 0.95
j
=
EQUATION1332 V1 EN-US
Power factor at maximum line loading
max
25
j
= °
EQUATION1333 V1 EN-US
Maximum expected load angle
2.5
si
f Hz
=
EQUATION1334 V1 EN-US
Maximum possible initial frequency of power oscillation
7.0
sc
f Hz
=
EQUATION1335 V1 EN-US
Maximum possible consecutive frequency of power oscillation
The minimum load impedance at minimum expected system voltage is equal to
equation
76 .
2 2
min
min
max
380
144.4
1000
L
U
Z
S
= = = W
EQUATION1337 V1 EN-US
(Equation 76)
The minimum load resistance R
Lmin
at maximum load and minimum system
voltage is equal to equation 77 .
( )
min min max
cos 144.4 0.95 137.2
L L
R Z
j
= × = × = W
EQUATION1338 V1 EN-US
(Equation 77)
The system impedance Z
S
is determined as a sum of all impedances in an
equivalent two-machine system, see figure 67 . Its value is calculated according to
equation 78 .
( )
1 1 1
17.16 154.8
S SA L SB
Z Z Z Z j
= + + = + W
EQUATION1339 V1 EN-US
(Equation 78)
The calculated value of the system impedance is of informative nature and helps in
determining the position of the oscillation center, see figure
68 , which is for a
general case calculated according to equation 79 .
1MRK 505 393-UEN B
Section 7
Impedance protection
Line differential protection RED650 2.2 IEC 137
Application manual