Reliable installation of alternative capacitor banks against reactive power shortage

The present paper deals with the capacitor banks installed at the medium voltage buses of the transmission substations on the Greek island Crete. The needs in reactive power of the Cretan network are outlined. The installed capacitors compensate the reactive power of the network and improve the 150 kV voltage levels of the substations. The typical Double Wye Ungrounded externally fused capacitor bank is first presented; the standardization and the classification of the existing banks are cited. Two alternative types of capacitive banks, i.e. Single Wye Grounded externally fused and Double Wye Ungrounded internally fused, recently installed are presented and analyzed, regarding load flow and protection issues. These cases in spite of not meeting the typical specifications, proved to solve satisfactorily the urgent problem of the voltage profile at the island´s autonomous grid. A vertical comparison is attempted, among all three categories of capacitor banks. Analytical and computer aided engineering tools are presented.