Sensor part for installation in medium-voltage cable compartments, which sensor part comprises a voltage divider based on the capacitive divider principle, which voltage divider comprises: —a first capacitor, comprising an elongate primary conductor wrapped in a dielectric material and an elongate conducting shield arranged around the dielectric material, which first capacitor has a first capacitance rating; —a second capacitor, having a second capacitance rating, which second capacitor further comprises a first lead conductively connected with the conducting shield of the first capacitor and a second lead conductively connected to a common reference, such as earth; —a voltage output line, conductively connected with the conducting shield of the first capacitor; wherein the second capacitance rating is larger than the first capacitance rating, so that when during use the primary conductor is conductively connected with a live circuit carrying an alternating current, a measurement of a voltage between the common reference and the voltage output line can be taken as a ratio of the voltage between the live circuit and the common reference.