Abstract: A partial discharge sensor includes a first current transformer having an opening. A conductive shield is disposed within the opening of and proximate to the first current sensor. The conductive shield has an opening. The concentric openings of the first current sensor and the conductive shield are structured to receive a first medium voltage power conductor. A second conductor is electrically connected to the conductive shield. The second conductor is structured to be electrically connected to ground. A second sensor cooperates with the second conductor and is structured to sense signals associated with partial discharge activity. An electronic monitoring circuit receives the output of the second sensor. The electronic monitoring circuit is structured to provide on-line monitoring of a partial discharge occurring within the first medium voltage power conductor.