The discharge over dielectric interfaces popularly known as surface discharge is a very common defect type that is associated with its respective discharge pattern under AC voltages. However, the same designs behave differently under DC voltages leading up to erratic PD behavior. To understand the process of surface discharge an equivalent circuit model is developed, and its influencing material parameters such as the volumetric and surface electrical conductivities and the relative permittivity are measured experimentally. This paper describes the methodology and setup of the measurement based on international standards. The final goal is to provide the constituent model parameters that can describe the surface discharge model under DC stress.@en

This paper presents the investigation on surface discharge behavior of various dielectric samples under DC. It sequentially develops the knowledge base for the study and analysis of the partial discharge (PD) defect with the goal of PD defect identification under DC. In order to facilitate this, the material properties of the dielectric are measured. Finite Element (FEM) simulation is used to obtain the preliminary estimates of the electric field and dielectric properties that concern partial discharge behavior. The DC-PD tests performed on the surface dielectric samples demonstrate a highly plausible behavior based on simulation results and other literature. It also displays a great degree of similarity towards the AC surface discharge behavior. The paper concludes by presenting novel partial discharge fingerprints for the surface PD defect that will aid in defect identification under HVDC.@en

Corona is one of the most common forms of partial discharge (PD) occurring in high voltage (HV) energy systems. The corona mechanism in air is not exclusive to the field of energy applications but has also been widely studied by physicists to theorize mechanisms of charge transfer during the different phases of gas discharge. The phases of the discharge and its corresponding behavior with alternating voltage (AC) are well established and represented through various discharge trends, patterns and stages. This not only makes the identification of the PD defect possible but also helps evaluate the risk. This paper investigates corona configurations under DC stress in an attempt to create a similar outline of the defect as exists under AC. The defect is studied in terms of the pulse sequence information. The measurement system requirements are kept within a realistic realm to preserve applicability to industrial measurements. Finally, it makes selective recommendations for the effective identification of the discharge condition under DC stress.@en

This paper presents several approaches to the analysis of partial discharge (PD) data. Three common defects namely corona, surface and floating electrode are studied with the goal of defect identification under DC stress conditions. One of the major concerns with DC-PD testing, is its non-repetitive/erratic pulse pattern. This paper, however, only deals with the repetitive stages of discharge that will allow the study of their resultant patterns and trends. Several unique features such as the formative trend in the probability plot of time between discharges for the three common defect types shows promise in the quest for defect identification under DC. Further, the paper also describes in which way a three-pulse PSA diagram cannot serve as a standalone figure and hence requires a change in perspective by either adding or reducing a dimension. The last part of the paper presents a test methodology to identify the discharge source based on various discharge features.@en

Partial discharge measurements performed according to IEC 60270 has become an essential tool for the quality assurance of HV equipment. The main goal of IEC 60270 is to standardize and unify PD measurements to get comparable results for tests performed at various locations, using different equipment and by different operators. This paper aims at providing clear and unambiguous guidelines on how to perform repeatable and comparable PD measurements in compliance with one of the most popular international testing standards in Europe, the IEC 60270. This paper also discusses the functionality of the various components in the measuring setup. In addition, it makes some invaluable recommendations based on scientific knowledge regarding the selection of proper PD test and evaluation parameters to ensure correctness of obtained test results. The main focus is on the selection of a suitable frequency measurement range, which is a key step in the quasi-integration process involved in the charge estimation of the PD pulse.@en

Asset condition monitoring through Partial Discharge (PD) measurements is widely used for pre-emptive maintenance especially in cable networks. Several monitoring systems rely on measurements in the High Frequency (HF) band using wideband sensors when it comes to PD monitoring to have higher Signal to Noise Ratios (SNR), ignoring the radical attenuation of the higher frequencies by the cable. This paper presents measured values of attenuation from measuring loops and several other important insights that can help in the interpretation of PD measured data. @en

Partial discharge is a prevalent phenomenon under high voltage (HV) where the discharge partially bridges the gap between two electrodes. At increasing voltage levels, physical dimensions and distances between the electrical parts become critical. Designing electrical components for such high voltages and planning of high voltage laboratories/tests need to deliberate this aspect as it could lead to possible complications such as partial discharges (PD) from the floating metal components. Floating electrodes under AC voltages are associated with a distinctive PRPD pattern. However, there is a lack of literature on the physical interpretation of this pattern. Likewise, under DC voltages, no consistent explanation towards the defect behavior has been reported. Therefore, this paper presents an in-depth study of the floating electrode defect configuration under AC and DC voltages. Subsequently, it provides the physical interpretation of the discharge patterns obtained through the stepwise description of the discharge stages under both conditions. By formulating criteria for repetitive discharges and presenting novel PD fingerprints for DC floating electrode configuration, the outcomes published in this paper contribute towards prospective PD defect identification tools under HVDC.@en