Delta-connected banks are generally used only at distribution voltages and are configured with a single series group of capacitors rated at line-to-line voltage.
Delta-connected banks require a two bushing capacitor or single-bushing units with insulated racks.
Delta-connected banks are frequently used at 2400 V because capacitor units for wye connection at 2400 V are not readily available.
With only one series group of units, no overvoltage occurs across the remaining capacitor units from the isolation of a faulted capacitor unit.
Therefore, unbalance detection is not required for protection, but may be used to detect the outage of units within the bank.
No zero-sequence or third harmonic currents can flow into a delta-connected capacitor bank.
Where one series group per leg is used, the individual capacitor fuses shall be capable of interrupting the system short-circuit phase-to-phase fault current. This design may necessitate current-limiting fuses.
If internally fused capacitor units are used, unbalance detection is required to detect a capacitor with failed elements. There is no visible indication of a blown fuse.
Two or more series groups are normally required in each capacitor unit to enable the internal fuses to interrupt the fault current.
Static var compensator usually uses the delta connection for the thyristor-switched capacitors (TSCs) to simplify the controls and optimize the use of the thyristor valve.