Method of measurement for detecting a fault of a three-phase zone

System for protecting an electrical energy distribution box the electrical energy distribution box comprising a set of distribution bars comprising distribution bars intended to be connected between a generator and loads, each of the bars of the set being able to transfer at least a part of the electrical energy passing through it to at least one other bar of the set of bars, wherein the system comprises means for measuring current disposed upstream and downstream of a single distribution bar and processing means adapted for comparing the currents measured by the measuring means and to detect a fault in any one of the distribution bars of the set of bars on the basis of the currents measured in the said single distribution bar.