Circuits operation control and overloads protection: power cables equivalent ampacities

The evaluation of the ampacity of electric power cables and the overload protection are currently based on criteria to which the operation of the circuits will have to satisfy each time like the first time, without self-memory of the way of life, without discounts or debts correspondent to the actual profile-load, and certainly different from a steady-state line. The number and the duration of the emergency overload events are taken statistically into account (IEC rules) or are fixed in advance for an allowable average time per year over the life of the cable (ICEA approach). To enhance these criteria, the paper suggests a method to define an equivalent prospective power cables ampacity, based on the global allowable cables life-loss and considering the performance in time. Since monitoring and memorizing the actual life of power cables are still not possible, the paper proposes a simple and quick evaluation method for the duty cycles characterized or approximated by load-phases of continuous currents. Efforts at coordination between the protective device behavior and actual cable performance in time could induce progress in the development of a new protection joined to an operation control that allows evaluation of actual load duties and memorizing the actual age of the circuits