Partial discharge (PD) detection is essential for evaluating the insulation condition of power equipment. In this paper, the use of a high-sensitivity giant magnetoresistance (GMR) sensor with designed circuits for non-contacting PD detection is presented. Using this GMR system, magnetic signals have been successfully measured that are emitted in laboratory setups of a cross-linked polyethylene (XLPE) cable section and of a gas-insulated system (GIS) with artificial discharging defects. Comparison with simultaneously detected signals from a high-frequency current transformer (HFCT) demonstrates the high sensitivity and performance of the xMR system for PD detection.