A leakage current detecting sensor apparatus for detecting leakage current in a post-type insulator of an electrical power system, the apparatus comprising: a collection band adapted to be connected to an exterior surface of the insulator; and a sensor unit having a housing, the sensor unit comprising: a sensor assembly (144, 244) operable to generate an analog signal proportional to a received leakage current; an electronics module; a transfer lead interconnecting the sensor assembly and the collection band, the transfer lead operable to transfer leakage current, from the insulator, from the collection band to the sensor assembly; and a communications system; the apparatus being characterised in that the electronics module includes an analog peak detector circuit configured to detect a peak value of the analog signal during a first interval; the electronics module further includes an analog to digital converter operable to convert the peak value of the analog signal into a digital value; the electronics module is operable to assign the digital value to one of a plurality of bins based on the magnitude of the digital value, wherein each of the plurality of bins represents a predetermined range of magnitudes of leakage current; the electronics module further includes a counter for each bin; wherein each time the digital value is assigned to the assigned bin, the bin count of the assigned bin is incremented; and wherein the communication system is operable to wirelessly transmit the bin counts to an external receiver at a predetermined second time interval. a collection band adapted to be connected to an exterior surface of the insulator; and a sensor unit having a housing, the sensor unit comprising: a sensor assembly (144, 244) operable to generate an analog signal proportional to a received leakage current; an electronics module; a transfer lead interconnecting the sensor assembly and the collection band, the transfer lead operable to transfer leakage current, from the insulator, from the collection band to the sensor assembly; and a communications system; the apparatus being characterised in that the electronics module includes an analog peak detector circuit configured to detect a peak value of the analog signal during a first interval; the electronics module further includes an analog to digital converter operable to convert the peak value of the analog signal into a digital value; the electronics module is operable to assign the digital value to one of a plurality of bins based on the magnitude of the digital value, wherein each of the plurality of bins represents a predetermined range of magnitudes of leakage current; the electronics module further includes a counter for each bin; wherein each time the digital value is assigned to the assigned bin, the bin count of the assigned bin is incremented; and wherein the communication system is operable to wirelessly transmit the bin counts to an external receiver at a predetermined second time interval. a sensor assembly (144, 244) operable to generate an analog signal proportional to a received leakage current; an electronics module; a transfer lead interconnecting the sensor assembly and the collection band, the transfer lead operable to transfer leakage current, from the insulator, from the collection band to the sensor assembly; and a communications system; the apparatus being characterised in that the electronics module includes an analog peak detector circuit configured to detect a peak value of the analog signal during a first interval; the electronics module further includes an analog to digital converter operable to convert the peak value of the analog signal into a digital value; the electronics module is operable to assign the digital value to one of a plurality of bins based on the magnitude of the digital value, wherein each of the plurality of bins represents a predetermined range of magnitudes of leakage current; the electronics module further includes a counter for each bin; wherein each time the digital value is assigned to the assigned bin, the bin count of the assigned bin is incremented; and wherein the communication system is operable to wirelessly transmit the bin counts to an external receiver at a predetermined second time interval.