Electronic device (60; 62A,..., 62N) for monitoring an electrical quantity from among a voltage (U1, U2, U3) and an intensity (I1A,..., I3N) relative to an alternating current flowing in an electrical conductor (34, 36, 38; 42A, 44A, 46A,..., 42N, 44N, 46N), the alternating current having at least one phase, the device comprising: - a measurement module (66; 76A,..., 76N) configured to measure at least one value of the electrical quantity, - a radioelectric transmitter/receiver (70; 80A,..., 80N), - a transmission module (105; 128A,..., 128N) connected to the radioelectric transmitter/receiver (70; 80A,..., 80N), and - a calculation module (106; 124A,..., 124N) configured to calculate at least one parameter (φ i,j,k, ∥X i,j,k ∥) for monitoring the electrical quantity as a function of at least one measured value of said electrical quantity, characterised in that each monitoring parameter (φ i,j,k, ||X i,j, k ||)is chosen from among an angular phase of the electrical quantity (φ i,j,k) and a modulus of the electrical quantity (∥X i,j,k ∥), the transmission module (105; 128A,..., 128N) being configured to transmit, to another electronic device, a data message (M1; M2A,..., M2N) containing at least one calculated monitoring parameter (φ i,j,k, ∥X i,j,k ∥); the calculation module (106; 124A,..., 124N) being configured to calculate the angular phase (φ i,j,k) of the electrical quantity, for the or each phase of index i, according to the equation: φ i, j, k X = arctan Im X i, j, k Re X i, j, k wherein Re X i,j,k, Im X i,j,k represent real and imaginary coefficients of a Fourier series decomposition of the electrical quantity, i is the index of the corresponding phase, j is the rank of the harmonic for the Fourier series decomposition, the fundamental being of rank equal to 1, and k is an index of a voltage period P voltage during which the value of the electrical quantity is measured; the calculation module (106; 124A,..., 124N) being configured to calculate the modulus (∥X i,j,k ∥) of the electrical quantity, for the or each phase of index i, according to the equation: ‖ X i, j, k ‖ = Re X i, j, k 2 + Im X i, j, k 2 2 wherein Re X i,j,k, Im X i,j,k represent real and imaginary coefficients of a Fourier series decomposition of the electrical quantity, i is the index of the corresponding phase, j is the rank of the harmonic for the Fourier series decomposition, the fundamental being of rank equal to 1, and k is an index of a voltage period P voltage during which the value of the electrical quantity is measured. - a measurement module (66; 76A,..., 76N) configured to measure at least one value of the electrical quantity, - a radioelectric transmitter/receiver (70; 80A,..., 80N), - a transmission module (105; 128A,..., 128N) connected to the radioelectric transmitter/receiver (70; 80A,..., 80N), and - a calculation module (106; 124A,..., 124N) configured to calculate at least one parameter (φ i,j,k, ∥X i,j,k ∥) for monitoring the electrical quantity as a function of at least one measured value of said electrical quantity, wherein Re X i,j,k, Im X i,j,k represent real and imaginary coefficients of a Fourier series decomposition of the electrical quantity, i is the index of the corresponding phase, j is the rank of the harmonic for the Fourier series decomposition, the fundamental being of rank equal to 1, and k is an index of a voltage period P voltage during which the value of the electrical quantity is measured; the calculation module (106; 124A,..., 124N) being configured to calculate the modulus (∥X i,j,k ∥) of the electrical quantity, for the or each phase of index i, according to the equation: wherein Re X i,j,k, Im X i,j,k represent real and imaginary coefficients of a Fourier series decomposition of the electrical quantity, i is the index of the corresponding phase, j is the rank of the harmonic for the Fourier series decomposition, the fundamental being of rank equal to 1, and k is an index of a voltage period P voltage during which the value of the electrical quantity is measured.