The load conditions are (a) Normal continuous load, (b) Intermittent load, (c) Short time load and (d) Cyclic load.
By normal continuous load, it is meant that the given load current will be flowing continuously through cables.
If the cable is switched on and off periodically, so that the time between switching ‘off’ , and then ‘On’ is not sufficient to cool the conductor to the ambient temperature during the rest period, then such load is called intermittent load.
When the conductor is allowed to cool down to ambient temperature after the load period then this load is called as short time load.
In variable nature of loading conditions if the peak loads on supply cables are of cyclic nature occurring at fixed periods over a well defined time, it is known as cyclic loading. Cyclic loadings are commonly experienced in industry as for cycle of 8 hours on & 16 hours off or a cycle of 16 hours on & 8 hours off load. For calculating the permissible current rating of a cable in an industry peak cyclic loading is considered from the load curve.