Abstract
Capacitor banks rated 132 kV/ 72 MVAr are installed at the Durban North Substation of
Ethekwini municipality to compensate for inductive power losses. The POW or synchronous switching
technique is used for on-line switching of these banks, in a bid to minimise high magnitude induced
transient voltage and current. in this study, the voltage waveform records and the percentage current
unbalance, measured on and six months post commissioning of the capacitor banks are analysed
in order to test the effectiveness of POW switching method, when implemented with mechanically
linked 3-phase, 3-pole SF6 circuit breakers. The results obtained indicate that within 6 months of
commissioning, capacitive impedance of the banks failed, as result of high magnitude induced transient
current and voltage, and the percentage unbalance level observed in the neutral current grew from 2.3%
to 5.7%.