Icar CRA BS7 Mode D'emploi page 18

Pressing the "+" button commands the step to be turned on, while with the "-" button
commands it to be turned off.
A command given and not yet performed (due to reconnection and/or switching time), can
be cancelled by pressing the opposite command.
To exit the function, "AUTO/MAN" should be pressed again twice in quick succession or
wait 30 seconds without pressing any button.
13. Medium voltage system power factor correction
With a proper setting, the CRA BS7/BS14 power factor correction equipment can be easily
used for improving the power factor in medium voltage systems.
Since the maximum voltage signal applicable to the CRA BS7/BS14 is 500Vac, for higher
voltages a volt transformer with output normalised at 100Vac is used.
For the correct operation of the equipment, it is necessary to calculate the value of the
smallest capacitor bank to be set.
Example:
The rated voltage of the system to be set must be 100Vac.
The rated voltage of the capacitors must be suitably proportioned to the system's rated
voltage. E.g. if the rated voltage of the capacitors is 18,000V, a value calculated as follows
should be adopted during set-up: (100/15,000)*18,000=120V.
Given the high power of the capacitor banks in medium-voltage systems, it is often
necessary to alter the step switching interval between the step and the maximum and
minimum limits of the reconnection time.
Low voltage system power correction factor with TA on on the medium voltage
To set the correct value of the C.T.'s primary in the set up, it is necessary to bear in mind
the transformation ratio of the power transformer. All the other parameters are set
normally:
Example:
C.T. (step-down transformer) 1.200/5A
Mains voltage
Capacitor bank 5.000kvar
Volt transformer 15.000/100V
Calculation
Value to be set
Mains voltage
B.T. network 400V
Calculation
Value to be set
24
15.000V
(100/15.000)*5.000=33.33kvar
33.33kvar
15.000V
(15.000/400)*120=4.500A
4.500A