How many times the rated current can a cable handle momentarily?
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What is the maximum instantaneous current that the cable can handle? Generally, the instantaneous current is 2-7 times higher; can an excessively high instantaneous current damage the cable?
The selection of cables generally needs to meet two requirements: 1. The cross-sectional area chosen must be sufficient to handle the load capacity; under normal operating conditions, powering the load should not cause the cable to overheat and get damaged； 2. Calculate the short-circuit current of the power supply system; the cross-sectional area of the cables must be sufficient to ensure dynamic and thermal stability under short-circuit conditions in the maximum operating mode. Does the term \"several times the instantaneous current\" mentioned by the poster refer to the short-circuit current required to ensure dynamic and thermal stability?
2. Calculate the short-circuit current of the power supply system; the cross-sectional area of the cables must be sufficient to ensure dynamic and thermal stability under short-circuit conditions in the maximum operating mode. Could you give an example to illustrate?
For example, if one day a short circuit occurs in a feeder circuit on a certain 6 kV bus, with a short-circuit current of 25 kA, and assuming that this value does not reach the setting for the instantaneous overcurrent protection, or if no such protection is installed on that feeder, or yet if the feeder’s instantaneous overcurrent protection fails to operate, then the fault will have to be cleared by the overcurrent protection of the bus incoming switch. In this way, the short-circuit current lasts for a few seconds. If the dynamic and thermal stability of the incoming cable does not meet the requirements, an explosion will occur during those few seconds when the short circuit persists, thereby expanding the scope of the accident.