scope:

Applies to cables buried in uniform soil, either directly or in ducts, when carrying a load which varies cyclically over a 24 h period, the shape of each daily cycle being substantially the same. Gives methods for calculating the cyclic rating factors for cables where the internal thermal capacitance can be neglected. Requires for this calculation only a knowledge of the full shape of the load variation for not more than 6 h immediately preceding the time of maximum temperature and an average value for times before that.