Three-phase connection through a double star.
Formed by single-phase capacitors configured in two stars joined by a common neutral. The purpose of this connection is the possibility of incorporating an unbalance protection for the detection of possible internal defects in the capacitors due to the wear and tear and ageing of the equipment or defects that may occur from the electrical network.
Combined with capacitors with internal fuses, not only high safety, but also greater service continuity is achieved.
The number of capacitors in the double star depends on the mains voltage and the required battery power. In any case it must always be a multiple number of 3 and never less than 6 units.
The batteries may consist of the following components, depending on the characteristics of the installation:
- Metal enclosure.
- Gen. switch Automatic in SF6 of maneuvering (opt).
- Shock ballasts.
- Unbalance current transformer.
- Unbalance relay (optional).
Normally used when the configuration up to 12 kV max. voltage is not feasible due to power level (high power of Reactive Energy demanded) or insulation level (insulation voltages higher than 12 kV due to mains voltages of secondary transformers higher than 11 kV).