23
5.6 Response Current (c/k)
The Control Relay RM 9606 calculates a
control characteristic from the power
factor, the parallel shift and the limitation
(in Figure 4 to Figure 10 shown as a
dotted line) and has a tolerance band of
0.65 times the smallest stage in inductive
as well as in capacitive direction (marked
with bold line). The control relay
consistently achieves this control band by
switching on and off systematically. It is
assumed that the connected capacitor-
stages are sufficiently dimensioned.
The response current corresponds to half
the width of the tolerance band, within
which the reactive current can change
without capacitor stages being switched
on or off.
This is essential to ensure that the system
does not oscillate. The total width of the
tolerance band is selected in such a way
that it corresponds to approx. 1.3 times
the reactive current of the smallest
capacitor stage.
When setting the automatic stage current
identification to "OFF" the response cur-
rent can be set between 0.02 and 2.0 A in
steps of 0.01 A. The correct setting for a
400 V voltage system and a current trans-
former with 5A secondary current can be
taken from Table 3.
In the case of other voltages or current
transformers for which the primary or
secondary current is not given, the
response current can be calculated from
the general equation:
Equation 1:
kU
Q
kU
Q
kc
×
×≈
××
×= 375.0
3
65.0/
c/k = response current (Amps) to be set
Q = capacitor stage rating in var of the
smallest stage (not the complete system)
U = mains voltage (V) on the primary side of
the current transformer
k = transformer ratio
(primary /secondary current)
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