A system for the detection of discharges over high voltage power-line insulator strings of an electrical grid. A sensor unit is deployed on a non conducting cable of the grid. The sensor feeds an array of band cut-off filters receiving each signals from said at least one sensor unit. An analogue processor is associated with each of the band cut-off filters associated each with a current peak detector. An ADC unit is associated with each one of said analogue processors. In addition a digital processor is provided for calculating data received from each one of the ADCs and one radio transmitter unit sends data to a gateway of a network. A digital processor is adapted to send data processed based on the output of the ADCs, to the radio transmitter for conveying the data to processor associated with a WAN.