Small capacitors banks are made with single phase capacitors without internal fuses, they are connected in delta and protected by means of HRC limiting current fuses.
Capacitors banks of higher power are made up of at least six single phase capacitors or three split-phase, without internal fuses, with capacitor bank connected in insulated double star and unbalance protection.
In case of capacitors without internal fuses, higher power capacitor banks use one single external expulsion fuse for each capacitor; this fuse, which is specific for power capacitors, is very easy and effective, and it allows an immediate evidence of faulty capacitor. In these type of banks the number of capacitors is chosen so to allow the bank to keep on service even in the case one capacitor has been insulated by its fuse melting.
An unbalance protection, which works out a lower priority protection, will provide the capacitor bank disconnection after a certain number of capacitors are out of order. Capacitors without internal fuses, which have smaller losses than those with internal fuses, are designed to lower dielectric withstand and are so much more robust and reliable.