System for calculating an electrical magnitude, transformer station including such a system and method for calculating an electrical magnitude with such a system

This calculation system (20) is adapted for calculating an electrical quantity relating to an electrical installation comprising several secondary electrical conductors (42A,..,48C) electrically connected to a primary electrical conductor (34 ; 36 ; 38). This system comprises a first module (60) comprising a radio transmitter (70) and a plurality of second modules (62A, 62B, 62C). These second modules comprise a radio transceiver (86A, 86B, 86C) and a sensor (83A, 83B, 83C) of the intensity (IA1, IA2, IA3, IB1, IB2, IB3, IC1, IC2, IC3) of the current flowing in a corresponding conductor among the primary and secondary conductors. The first module comprises first means (72, 74) of transmission, intended for each second module, of a first message (M1) of temporal synchronization. Each second module comprises first means (84A, 88A ; 84B, 88B ; 84C, 88C) of reception of the first message (M1) and second means of transmission (84A, ... 88C), intended for a third module (63), of a second message (M2A, M2B, M2C) containing at least one value of the intensity measured by the corresponding current sensor. The intensity values are measured quasi-simultaneously, preferably with a synchronization error margin of less than 10µs, and the third module comprises a radio receiver (101), second means (102, 104) of reception of the second messages (M2A, M2B, M2C) and a calculating unit (104) of the electrical quantity from the intensity values received via said second messages.