frako PQC - Page 33

Installation | 33
FRAKO | Operating Manual | Power Quality Controller – PQC
5.3.4.1 Connection type
With the connection type, the phase angle of the current and voltage measurement
paths is indicated. It can be found from the table below:
Connection type Connection to voltage path
L/N – L L/N – L L/N – L
0 L1 – N L2 – N L3 – N
1 L1 – L3 L2 – L1 L3 – L2
2 N – L3 N – L1 N – L2
3 L2 – L3 L3 – L1 L1 – L2
4 L2 – N L3 – N L1 – N
5 L2 – L1 L3 – L2 L1 – L3
6 N – L1 N – L2 N – L3
7 L3 – L1 L1 – L2 L2 – L3
8 L3 – N L1 – N L2 – N
9 L3 – L2 L1 – L3 L2 – L1
10 N – L2 N – L3 N – L1
11 L1 – L2 L2 – L3 L3 – L1
Current transformer in:

L1

L2

L3
Example:
The current transformer is installed in phase L2, while the voltage is measured
between the phase L3 and N. It is therefore connection type 4.
If the current transformer is installed or connected the wrong way round, this can be
corrected for by the choice of connection type, i.e. by adding 6 to the connection type
number given by the table. In the above example, this gives the connection type 10. If
the result of this addition were to be greater than 11, the rule is to subtract 6 from the
connection type number instead.
5.3.4.2 Calculation of c/k
To operate the system, the value of c/k (response current) must be determined. This
equals 65 % of the nominal current of the smallest capacitor stage and is to be
detected in the PQC current measurement path.
The c/k value can be calculated from the following formula:
IA=0.65 ·
Qsmallest stage
V · √3 · k
· 1000 ≈ 0.375 ·
Qsmallest stage
V · k
· 1000 [mA]
IA = response current in mA to be set
Qsmallest stage = capacitive power of smallest stage in var (not the total capacitive power
of the system)