ABB REL650 - Page 165

GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
99001019_ansi.vsd
~~
E
A
d
A
= const
d
B
= f(t)
E
B
A B
Z
SA
Z
SB
Z
L
R
ANSI99001019 V1 EN
Figure 76: Protected power line as part of a two-machine system
Reduce the power system with protected power line into equivalent two-machine system
with positive sequence source impedances Z
SA
behind the IED and Z
SB
behind the remote
end bus B. Observe a fact that these impedances can not be directly calculated from the
maximum three-phase short circuit currents for faults on the corresponding busbar. It is
necessary to consider separate contributions of different connected circuits.
The required data is as follows:
400
r
V kV=
EQUATION1728 V1 EN
Rated system voltage
min
380V kV=
EQUATION1729 V1 EN
Minimum expected system voltage under critical system
conditions
60
n
f Hz=
EQUATION1730 V1 EN
Rated system frequency
400
3
p
V kV=
EQUATION1731 V1 EN
Rated primary voltage of voltage protection transformers used
0.115
3
s
V kV=
EQUATION1732 V1 EN
Rated secondary voltage of voltage instrument transformers used
1200
p
I A=
EQUATION1326 V1 EN
Rated primary current of current protection transformers used
Table continues on next page
1MRK 506 334-UUS A Section 6
Impedance protection
159
Application manual