Influence of Insulating Material Properties on Partial Discharges at DC Voltage

Abstract

Understanding a partial discharge mechanism at direct current (DC) is an actual research topic that requires both modeling, simulations and measurements. This paper describes an influence of insulating material properties on partial discharges at DC voltage. Modifications of the traditional model reflecting the conditions of partial discharges (PD) inception and post discharge processes at DC voltage have been proposed. The aim was to show the partial discharge mechanisms and draw attention to the role of parameters of insulation materials adjacent to the cavity at DC voltage. The investigations were performed on two kinds of dielectric material used in power cables. Various combinations of specimens were designed to reveal the effect of the material resistivity on the PD activity. Key observations referred to the impact of the void adjacent material resistance on the partial discharge inception voltage threshold at DC voltage. The modified PD model was applied to analyze both inception and post discharge recovery stage. The role of dielectric properties of material adjacent to the void was investigated, highlighting its impact during static inception stage and in charging stage. Despite many simplifications introduced in the model, measurement results have confirmed the role of the dielectric material surrounding the void on partial discharge dynamics. The average time interval between PD pulses revealed a systematic relationship with respect to the applied voltage and specimen resistivity. This value can be considered in the future research for diagnostic indicator at DC voltage.

Partial Discharge-Originated Deterioration of Insulating Material Investigated by Surface-Resistance and Potential Mapping

“…Due to the intensive accelerated deterioration test (high-frequency and high-electric field stress), the spatial distribution of the PD filamentary channels became more and more uniform in their shapes. The mechanism of these effects also referred to the memory mechanism that was related to the individual PD events [12,21,27,35].…”

“…A locally accumulated space charge may elevate operational stresses in HVDC polymeric cable systems-especially during polarity inversion [7]. The actions of partial discharges in gaseous inclusions result in changes in void surface conditions (for example, their conductivity, morphology, or roughness), which impacts the charge accumulation and transport effects [8][9][10][11][12][13]. Special attention is paid to investigations related to effective discharge and memory effects [10,[14][15][16].…”

Impact of heterogeneous cavities on the electrical constraints in the insulation of high-voltage cables

“…As a result, cables, cable terminations and cable connections can be further compressed and lead to insulation failure. Florkowski, [11] Florkowski, describes the influence of insulating material properties on DC partial discharge. The author is demonstrated the partial discharge mechanism and draw attention to the role of the parameters of the insulating material next to the cavity in the dc voltage.…”

Surface discharge imaging in presence of deposited space charges in non‐uniform DC electric field

“…The topic is still exciting for researchers because charge accumulation in such structures has a direct impact on the electric withstand capabilities assessed by partial discharges (PDs) and flashover. The topic is multithreaded, comprising research on the following: gas/bulk conduction mechanisms [8,15,17,18], changes in volume resistivity and the non-linear effects of surface resistivity [17,18], the influences of temperature [19], humidity [15,20,21], and contamination, the presence of particles and microdischarges [22,23], surface erosion processes [24], the impact of surface treatment (i.e. roughness and coatings) [15], insulator shape optimization [25], and the mapping of surface charge distribution [5,6].…”