8-2 C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUALARRANGEMENT OF SHUNT CAPACITOR BANKS CHAPTER 8: APPLICATION OF SETTINGS8Figure 8-1: Externally fused shunt capacitor bank and capacitor unit8.1.3 Internally fused capacitorsEach capacitor element is fused inside the capacitor unit. A simplified fuse is a piece of wire sized to melt under the faultcurrent, and encapsulated in a wrapper able to withstand the heat produced by the arc during the current interruption.Upon the capacitor failure, the fuse removes the affected element only. The other elements, connected in parallel in thesame group, remain in service but with a slightly higher voltage across them.The figure illustrates a typical capacitor bank utilizing internally fused capacitor units. In general, banks employinginternally fused capacitor units are configured with fewer capacitor units in parallel, and more series groups of units thanare used in banks employing externally fused capacitor units. The capacitor units are built larger because the entire unit isnot expected to fail.Figure 8-2: Internally fused shunt capacitor bank and capacitor unit8.1.4 Fuseless capacitorsA fuseless capacitor bank typically is the most prevalent design. The capacitor units in the bank are connected in seriesstrings between phase and neutral. The higher the bank voltage, the more capacitor elements in series.phase Aphase Bphase C834753A1.CDRphase Aphase Bphase C834754A1.CDR
