The minimum load resistance R
Lmin
at maximum load and minimum system voltage is
equal to equation 403.
( )
min min max
cos 144.4 0.95 137.2
L L
R Z
j
= × = × = W
EQUATION1338 V1 EN (Equation 403)
The system impedance Z
S
is determined as a sum of all impedance in an equivalent two-
machine system, see figure
226. Its value is calculated according to equation 404.
( )
1 1 1
17.16 154.8
S SA L SB
Z Z Z Z j= + + = + W
EQUATION1339 V1 EN (Equation 404)
The calculated value of the system impedance is of informative nature and helps
determining the position of oscillation center, see figure 227, which is for general case
calculated according to equation 405.
EQUATION1340 V1 EN (Equation 405)
In particular cases, when
EQUATION1342 V1 EN (Equation 406)
resides the center of oscillation on impedance point, see equation 407.
( )
1
7.43 33.9
2
S
CO SA
Z
Z Z j= - = + W
EQUATION1341 V1 EN
(Equation 407)
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 439
Application manual
To Next Page
Loading...
