A sensor device for detecting voltage in a conductor cable includes a sense electrode to be disposed over a surface of the conductor cable to cover a sense region having a sense axial width and a sense circumferential length and a reference electrode to be disposed over the surface of the conductor cable to cover a reference region. The reference region has an axial position adjacent the axial position of the sense region and has a reference circumferential length greater than the sense circumferential length. The sensor device further includes a charge measurement circuit connected in series between the sense electrode and the reference electrode to measure a charge measurement and circuitry to compare the charge measurement to a threshold to detect a presence of the voltage in the conductor cable.