This part of IEC 60143 concerns internal fuses designed to isolate faulty capacitor elements, to allow operation of the remaining parts of that capacitor unit and the bank in which the capacitor unit is connected. Such fuses are not a substitute for a switching device such as a circuitbreaker, or for external protection of the capacitor bank, or any part thereof. The object of this standard is – to formulate requirements regarding performance and testing; – to provide a guide for coordination of fuse and bank protection. NOTE – External fuses for series capacitors are treated in IEC 60143-1, annex A: "Test requirements and application guide for external fuses and units to be externally fused".