Novar 300 - SETTING OF C;K VALUE

NOVAR 300 Operation & Maintenance Manual NOVAR_CM
Page 18 of 29
3.4 SETTING OF C/K VALUE
The c/k potentiometer should be set according to the following equation;
C/k
Smallest Capacitor
Step Size in vars
3VI
5=
××












×
where: V = nominal primary system voltage
I = primary rating of the current transformer
This is indicated on the display by the small c symbol in the upper part of digit 4 if the
expanded display mode is selected on models having displays.
3.4.1 Examples of Calculation and C/K Settings
Example 1
A 25 kvar capacitor operating on a 415 V, 3 phase supply, is controlled by a single stage
controller operating via a 200/5 CT but without a VT.
C = 25,000 vars, V = 415 V, I = 200 A
C/k
25,000 5
3 415 200
0.87=
×
××
=
The NOVAR 300 is scaled to give a deadband of 150 % nominal capacitor size.
(i.e. NOVAR 300 will switch capacitors in circuit when the input lagging vars exceed three
quarters of a capacitor step size . NOVAR 300 will switch capacitors out of circuit when the
input leading vars exceed three quarters of a capacitor step size .)
The value of C/K can be directly entered into the unit.
Example 2
A multi-stage unit controls a 6 stage capacitor bank. Each stage is rated at 100 kvar. The
voltage is 415 V and the CT is 1000/5. There is no VT.
C = 100,000 vars, V = 415 V, I = 1,000 A
C/k
100,000 5
3 415 1,000
0.70=
×
××
=
As above, this value can be directly entered into the unit.