ABB KLF-1, Инструкция

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I.L. 41-748.1F
6
while Z
C
independently fixes the “short reach”.
With the reversing links in the normal position
(+Z
C
) the circle includes the origin; with the oppo-
site link position (-Z
C
) the circle misses the origin.
The following paragraphs explain this compensator
action.
Referring to figure 4 note that X
C
and C
C
cause the
polarizing voltage to be shifted 90˚ in the leading
direction. Thus, when the current is zero, polariz-
ing voltage V
POL
leads the operating voltage V
OP
by 90˚, as shown in figure 6(a). This relation pro-
duces restraining torque. To illustrate how Z
A
fixes
the long reach, assume a relay current which leads
V
AO
by 90˚ and of sufficient magnitude to operate
the relay. This means the apparent impedance is
along the -X axis. Note in figure 6(b) that the Z
A
compensation reverses the operating voltage
phase position. The relay balances when this volt-
age is zero. Note that this balance is unaffected by
the Z
C
compensation, since this compensation
merely increases the size of V
POL
.
For lagging current conditions note in figure 6(c)
how V
POL
Is reversed by the Z
C
compensation. In
this case Z
A
compensation has no effect on the
balance point. This explains why the short reach
point is fixed independently by Z
C
.
Figure 6 assumes that Z
C
is positive (circle
includes origin). If the current coil link is reversed,
the compensation bZ
C
. In figure 6(b) this
change would result in, V
POL
being reduced rather
than increased by the compensation. As the cur-
rent increases V
POL
will finally be reversed,
re-establishing restraining torque. Thus, the cur-
rent need not reverse in order to obtain a
“short-reach” balance point. Instead of the appar-
ent impedance need only move towards the origin
in the -X region to find the balance point. There-
fore, the circle does not include the origin with a
reversed link position.
Figure 5. R-X Diagram Characteristics with Various Z
C
Compensator Settings
tings. Compensators T
A
and T
C
are designed so
that its mutual impedance Z
A
or Z
C
has known and
adjustable values as described below under
CHARACTERISTICS and SETTINGS. The mutual
impedance of a compensator is defined here as
the ratio of secondary induced voltage to primary
current and is equal to T. Each secondary com-
pensator voltage is in series with voltage V
AO
.
Compensator voltages are equal to I
A
Z
A
for long
reach compensator and I
A
Z
C
for short reach com-
pensator, where I, is the relay current.
Figure 5 shows how the compensation voltages
I
A
Z
A
and I
A
Z
C
influence the R-X circle. Note that
Z
A
independently determines the “long reach”,
Figure 6. R-X Diagram Characteristics with Various Z
C
Compensator Settings
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