ABB Relion REC670, Applications Manual

Page: 454 / 658

Assume that we want to achieve that
j
2
= -90°, then:
0
1 1
( ) 90
0
1
0
1
90
90
j j j j
j j
j j
+ -
D = ´
ß
D = ´ =
ß
-
= +
ß
= - -
j j j j
V Z I
Ve Ze Ie ZIe
EQUATION1983-ANSI V1 EN-US
(Equation 124)
If for example cos
j
= 0.8 then
j
= arcos 0.8 = 37°. With the references in figure 181 ,
j
will be negative (inductive load) and we get:
0 0 0
1
( 37 ) 90 53
j
= - - - = -
EQUATION1939 V1 EN-US
(Equation 125)
To achieve a more correct regulation, an adjustment to a value of
j
2 slightly less than
-90° (2 – 4° less) can be made.
The effect of changing power factor of the load will be that
j
2 will no longer be close
to -90° resulting in V
L
being smaller or greater than V
B
if the ratio Rline/Xline is not
adjusted.
Figure 182 shows an example of this where the settings of Rline and Xline for
j
= 11°
from figure 181 has been applied with a different value of
j
(
j
= 30°).
Section 14
1MRK 511 401-UUS A
Control
448 Bay control REC670 2.2 ANSI
Application manual