The structure of high voltage crosslinked polyethylene (XLPE) cable and the characteristics of partial discharge (PD) mean that such discharges are very likely to happen in cable accessories due to insulation defects. The authors designed a wideband inner capacitive coupler for PD detection in cable accessories, and analyzed the characteristics of the coupler using an equivalent circuit model. The frequency response characteristics of the coupler were measured by square wave response. In addition, the measured results of the surface discharge produced along the dielectric interface in joints are given in 110 kV XLPE cable accessories. It is shown that the couplers work well in bands up to 500 MHz and can detect nanosecond transient pulse signals effectively. The couplers are available for ultrahigh frequency (UHF) measurement of PD in cables and cable accessories.