PD measurement of open air HV cable termination at the ground plate without coupling capacitor

XLPE insulated cable terminations are particularly sensitive to partial discharges (PD), therefore the on-site measurement of PD during cable commissioning tests is of particular interest to the grid operators. In some cases, the use of a coupling capacitor is not possible or not practicable. Lacking the coupling capacitor, the decoupling circuit does not fulfill the prerequisites of IEC standard 60270. The coupling circuit is only closed through the very low stray capacitances of the cable termination. The aim of the current paper is to answer the question whether - notwithstanding the existing standards - scalable partial discharge measurement can still be performed. In the first stage of investigation a laboratory model for cable termination and an appropriate model for computer simulation were developed. Based on this experience and the results of an on-site measurement, a digital termination model was created. Following the validation of the created models, a series of simulations were done, investigating the main influencers on PD sensitivity and on the error in the measured apparent charge.