ABB Relion 670 series, Руководство по применению

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all settings are performed in primary values. The impedance transformation factor is
presented for orientation and testing purposes only.
1200 0.11
0.33
1 400
p
s
s p
I
U
KIMP
I U
= × = × =
EQUATION1336 V1 EN-US
(Equation 425)
The minimum load impedance at minimum expected system voltage is equal to equation 426 .
2 2
min
min
max
380
144.4
1000
L
U
Z
S
= = = W
EQUATION1337 V1 EN-US
(Equation 426)
The minimum load resistance R
Lmin
at maximum load and minimum system voltage is equal to
equation 427 .
( )
min min max
cos 144.4 0.95 137.2
L L
R Z
j
= × = × = W
EQUATION1338 V1 EN-US
(Equation 427)
The system impedance Z
S
is determined as a sum of all impedance in an equivalent two-
machine system, see figure 240 . Its value is calculated according to equation 428 .
( )
1 1 1
17.16 154.8
S SA L SB
Z Z Z Z j
= + + = + W
EQUATION1339 V1 EN-US
(Equation 428)
The calculated value of the system impedance is of informative nature and helps determining
the position of oscillation center, see figure 241 , which is for general case calculated according
to equation 429 .
1
1
S
CO SA
B
A
Z
Z Z
E
E
= -
+
EQUATION1340 V1 EN-US
(Equation 429)
In particular cases, when
A B
E E
=
EQUATION1342 V1 EN-US
(Equation 430)
resides the center of oscillation on impedance point, see equation 431 .
( )
1
7.43 33.9
2
S
CO SA
Z
Z Z j
= - = + W
EQUATION1341 V1 EN-US
(Equation 431)
1MRK 505 343-UEN B Section 7
Impedance protection
367
Application manual