The "All-film" H.V. capacitor generally comes in the form of a single-phase unit (sometimes three-phase, but for max. voltages of 12 kV).
To form high power banks, there are three possible wiring or connection modes for combinations of unit capacitors, i.e.:

• Delta wiring (fig. 1)
  This type of wiring is used for low power banks and of nominal voltages less than 12 kV. These banks are generally designed for direct compensation on HV motor terminals. The capacitor(s) is/are  generally three-phase.

• Double star wiring (fig. 2)
  This type of wiring is suitable for banks of all powers and voltages (in this case, single-phase capacitors are subjected to a single voltage).
  An unbalance protection device (current relay and transformer) continuously monitors the unbalance current between two neutral points and, in the event of faults in a capacitor, opens the bank control device.

• H wiring (fig. 3)
  This type of wiring is designed for high power single-phase H.V. banks and V.H.V. three-phase banks. For three-phase banks, the unbalance is monitored on each phase.
  This unbalance monitoring system applies to both star and delta banks.