What is the function of a Fuse Tube?
I. Core Functions and Roles
Overload and Short Circuit Protection: When a protected circuit (such as a distribution transformer or an outgoing line) experiences a severe overload or short circuit fault, the fuse inside the fuse holder will rapidly melt due to the heat generated by the huge current.
Disconnecting the Faulty Circuit: After the fuse melts, an electric arc is generated, which is quickly extinguished by the special arc-extinguishing material (such as silica sand) inside the fuse, thus safely and completely disconnecting the fault current and preventing the fault from escalating.
Isolating the Fault Point: After melting, the fuse holder itself provides a visible, physical disconnection point (usually indicated by an indicator popping out or a change in the appearance of the fuse), clearly indicating the circuit where the fault occurred, facilitating quick location and repair by maintenance personnel.
II. Main Application Scenarios
Fuse holders are typically not used for main incoming line protection, but rather for protecting branch circuits or specific valuable equipment. The most common combination is:
Transformer Protection: This is the most classic application. In "load switch-fuse combination switchgear" cabinets (commonly found in ring main units), fuse tubes are specifically used to protect 10kV or 35kV distribution transformers.
Principle: When a short circuit occurs inside the transformer, the short-circuit current is enormous. However, the short-circuit current supplied by the system may not be sufficient to cause the upstream circuit breaker to trip quickly. At this time, a fuse tube specifically selected for the transformer parameters can melt rapidly within milliseconds, preemptively cutting off the current and protecting the transformer from burnout.
Voltage transformer protection: Used to protect the voltage transformers inside the cabinet, preventing internal faults from affecting the main busbar.
Small outgoing line protection: Used in some smaller capacity outgoing line circuits where protection sensitivity requirements are not high or cost control is strict.
