According to one aspect, embodiments described herein provide a sensor comprising a housing configured to be coupled around a portion of the transmission line, at least one probe capacitor configured to encircle the portion of the transmission line with the housing coupled around the portion of the transmission line, a measurement capacitor configured to encircle the portion of the transmission line with the housing coupled around the portion of the transmission line, a capacitance acquisition system, and a voltage measurement system, wherein the capacitance acquisition system is configured to determine a first value related to capacitance of the at least one probe capacitor, and based on the first value, determine a second value related to capacitance of the measurement capacitor, and wherein the voltage measurement system is configured to receive a signal providing the second value and calculate a third value related to a voltage level of the transmission line.