The acquisition parameters of an unconventional Partial Discharge (PD) measuring system affect the way the PD pulses are recorded and in turn, the results of the data processing. The noise based on the oscilloscope's vertical resolution is a feature of the sampled signal that is always present when a digital acquisition system is used. In PD unconventional systems, several parameters such as the sampling frequency Fs, the acquisition time T, the number of samples N and the vertical resolution VR of the digitizer result in a wide oscilloscope-based noise variation, that could be quantified by the signal to noise ratio (snr). The classification map is a tool that came available with the development of unconventional systems, that due to their wide bandwidth are able to resolve PD pulses in time and apply clustering techniques for PD source separation. The equivalent time T_eq and equivalent bandwidth W_eq, used to plot the classification map, attempts to extract features of the PD pulses to form clusters so that classification of sources can be achieved. The classification map is based on the ability of separating PD sources by resorting to the parameters T_eq and W_eq, that are believed to show significant differences for distinct PD sources, while they are clearly consistent for the same source. This paper conducts a set of theoretical analysis and laboratory measurements to evaluate the influence of the oscilloscope-based noise on the results of T_eq and W_eq. The results proved that the classification map is heavily influenced by the signal to noise ratio.

It is almost always the case that multiple partial discharge (PD) sources are active in high-voltage equipment as a result of insulation defects or ageing. Therefore, over the years, different clustering techniques have been tested and used, so that each individual PD source can be separated and subsequently recognized, e.g. by means of the phase resolved PD patterns (PRPD)[1].

Partial discharge (PD) field tests are widely used for cable assessment or cable commissioning. Usually, these tests are carried out by means of off-line tests where PD pulses are measured with capacitively coupled PD sensors. In off-line single-sided cable measurements, time-domain reflectometry (TDR) is used to locate the source of the PD along the cable. However, when the PD pulses are originated at the cable ends, the TDR technique cannot, by itself, properly distinguish between PD pulses produced at the cable near-end or at the far-end. This paper describes three different methods that produce an unambiguous localization of PDs produced at the cable ends, complementing the TDR.

Cellular polymers films have a too soft mechanical characteristic, like elastic compliance due of the internal porosity structure and their high electric insulation that gives the ability of hosting internal electrical dipoles. If a corona discharge is applied to the surface, the high electrical field induces internal discharges which leave a permanent static charge in the polymer cells. A macro dipole of cell dimension is generated producing a quasi-piezoelectric response. The d₃₃ piezoelectric constant can reach values of about many hundreds of pC/N. Thermally stimulated discharge currents (TSDC) are widely used to characterize charge density and stability of dielectric materials. In our work the relationship between TSDC and d₃₃ piezoelectric constant of two cellular polymers based on polyethylene and polypropylene films is investigated. Samples were thermally stretched, charged by corona discharge and metallized on both sides. The d₃₃ piezoelectric constant by quasi-static method was measured and then TSDC were registered. A strong relation between d₃₃ constants and TSDC curves on both cellular polymers was obtained.