Each capacitor unit or bank shall be provided with a directly connected discharge device. The discharge device shall reduce the residual voltage from the crest value of the rated value UN to 50 V or less within 1 min, after the capacitor is disconnected from the source of supply. There must be no switch, fuse or any other isolating device between the capacitor unit and the discharge device.

A discharge device is not a substitute for short-circuiting the capacitor terminals together and to earth before handling.

Where:

t = time for discharge from UN Jr to UR(s),
R = equals discharge resistance
C = rated capacitance (pF) per phase,
U_N = rated voltage of unit (V),
U_R = permissible residual voltage
k = coefficient depending on both resistance and capacitor unit connections, Value of k to be taken as per IS13340

Configuration of Capacitor bank

A delta-connected bank of capacitors is usually applied to voltage classes of 2400 volts or less.

In a three-phase system, to supply the same reactive power, the star connection requires a capacitor with a capacitance three times higher than the delta connected capacitor. In addition, the capacitor with the star connection results to be subjected to a voltage √3 lower and flows through by a current √3 higher than a capacitor inserted and delta connected.