What Is an Overcurrent?

Overcurrent Current exceeding the rated current. All loop currents greater than the rated load current of the loop conductor are overcurrents. It includes overload current and short-circuit current. The difference is that the overcurrent before the circuit insulation is damaged is called the overload current; the overcurrent after the insulation is damaged is called the short-circuit current.

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Overcurrent of electrical equipment is a form of failure. When the overload is not serious, it can not be cut off immediately, and the other is longer. If the overload is more serious, the delay is shorter. This is equivalent to a time limit.

Overcurrent is a fault in the line, but it is not in the protection range of quick-break. Generally it is single-phase grounding, etc., and it is required to trip within a certain time.

Overload is the excessive load of the line, which is not a fault. It only introduces a warning signal. Generally, it will appear in the summer when the factory starts. At the same time, everyone is using air conditioners, which exceeds the rated load of the equipment. When the load is too large, the service life of the primary equipment will be shortened, especially the transformer overload.

The protection purposes of the two are different. Overcurrent protection is protection against short-circuit faults. Overload protection is essentially against the thermal capacity of the device itself. For high-voltage transmission lines, the system must be stable. The overcurrent protection should cooperate with the protection section for short-circuit faults in the adjacent device, and the overload is matched with the equipment's hot load capacity. ^[4]

The action outlets of the two are not the same. Overcurrent protection is for short-circuit faults. The final outlet is to isolate the protection range. For the line, sometimes the reclosing will be activated; and for overload, the reclosing will not be activated, sometimes it may There are connected designs.

There are two main differences between overcurrent protection and overload protection: one is that the setting action value is different, and the other is that the action time is different.

The setting value of the overload protection is much lower than the setting value of the overcurrent protection, but it is greater than the normal load to prevent the equipment from overloading, and a certain delay must be added in order to avoid the equipment starting current. When the overcurrent protection is rejected for some reason, the overload protection can also be used as a backup protection for the overcurrent protection.