ABB RES670 Applications Manual page 116

Section 7
Impedance protection
110
(
= +
Z 5.3 j 35.7
SB 1
EQUATION1330 V1 EN-US
=
S 1000 MVA
max
EQUATION1331 V1 EN-US
( )
j
=
cos 0.95
max
EQUATION1332 V1 EN-US
j
= °
25
max
EQUATION1333 V1 EN-US
=
f 2.5 Hz
si
EQUATION1334 V1 EN-US
=
f 7.0 Hz
sc
EQUATION1335 V1 EN-US
The minimum load impedance at minimum expected system voltage is equal to
equation 13.
2
U 380
= =
Z min
L min
S 1000
max
EQUATION1337 V1 EN-US
The minimum load resistance R
voltage is equal to equation 14.
(
j
= ×
R Z cos
L min L min
EQUATION1338 V1 EN-US
The system impedance Z
equivalent two-machine system, see figure 46. Its value is calculated according to
equation 15.
= + +
Z Z Z Z
S SA 1 L 1 SB
EQUATION1339 V1 EN-US
The calculated value of the system impedance is of informative nature and helps in
determining the position of the oscillation center, see figure 47, which is for a
general case calculated according to equation 16.
Positive sequence source impedance behind B bus
)
W
Maximum expected load in direction from A to B (with minimum
system operating voltage U
Power factor at maximum line loading
Maximum expected load angle
Maximum possible initial frequency of power oscillation
Maximum possible consecutive frequency of power oscillation
2
= W
144.4
at maximum load and minimum system
Lmin
)
= × =
144.4 0.95 137.2
max
is determined as a sum of all impedances in an
S
( )
= + W
17.16 j 154.8
1
1MRK 511 407-UEN C
)
min
W
Phasor measurement unit RES670 2.2 IEC
Application manual
(Equation 13)
(Equation 14)
(Equation 15)