The Calculated Risk of Operating Capacitors Without Individual Fuses

The development of power capacitors has proceeded along the line of relatively small individual units for sound engineering reasons, and the performance of capacitor units as individuals has been very satisfactory. When capacitors are grouped in banks, this individuality or independence may be retained by fusing each unit. When group protection only is sulpplied, as by the use of bank fuses or circuit breakers the installation is no longer a collection of individuals but a consolidated group whose performance may be decidedly different. It is shown in this paper how the performance characteristic of the individual unit changes with the size of the group. Since the selection of protective methods and equipment may be dictated largely by economical considerations, the risk of operating groups of capacitors without individual fuses is evaluated.