Typically, in laboratory and diagnostics tests focused on measuring partial discharges, a pure sinusoidal voltage waveform is assumed. However, practice the spectral content of applied rarely so ideal additional components have significant impact discharge behavior electrical insulation systems. In this paper influence harmonics pattern evolution analyzed. The presented experiments were conducted transformer installed municipal network specimens representing defects system, form micro blade...

This paper describes a novel approach to understanding partial discharge (PD) dynamics and mapping of the channels in void. During long term PD exposure, discharges develop inside within void, leading variation area on void wall as well clustering effect. In this paper, development method for identifying localized changes dielectric structure, through detection dispersed with reduced resistivity which occur due multichannel discharges, is described. Discharge spots selected ranges surface...

This paper describes the influence of AC harmonics in HVDC systems on one main indicators high voltage insulation deterioration, partial discharge. may be subject to various disturbances including and ripples form pulsating voltages. Experiments, performed model void specimen at DC with selected superimposed harmonics, are described. A novel approach for recording discharges DC, based synchronization is proposed. In this way individual discharge pulses, occurring during a given measurement...

Three-dimensional printing technology is constantly developing and has a wide range of applications; one application electrical insulation, where the standard uses polymer-based filaments. Thermosetting materials (epoxy resins, liquid silicone rubbers) are broadly used as insulation in high-voltage products. In power transformers, however, main solid based on cellulosic (pressboard, crepe paper, wood laminates). There vast variety transformer components that produced using wet pulp molding...

Power electronics switching devices currently represent the dominant technology for supplying low voltage (LV) electric motors. The fast processes exert a different class of stress on dielectric insulating materials than standard sinusoidal excitations. Such stresses result in an increase dynamic activity working field, which turn lead to increased likelihood partial discharges (PD). stator design motor is often form random-wound windings, where magnet wires (copper or aluminum round coated...

A novel investigation into the behavior of interface between an insulating material and a conductor subjected to sinusoidal stimulus is presented. Both copper aluminum wires are used in windings electrical machines also as power cable conductors. During in-service operation, partial discharges (PD) may be initiated insulation systems. The paper presents experimental results showing interaction different kinds conductors dielectric materials on mechanism system. dedicated test setup designed...

This paper describes a new and intriguing observation relating to partial discharges specifically those which occur despite the absence of an applied voltage within chopped sequence. The discharge pulses, are referred as Partial Discharge Echoes, appeared in intervals where no was being applied, immediately after specimen had been exposed sinusoidal above inception level. measurements were performed on specimens with embedded void insulating or cross-linked polyethylene. In order capture...

An investigation is made of the influence an accumulated charge sprinkled on surface epoxy resin plate in corona mode partial discharge inception and its forms as analyzed by optical imaging at DC voltage. The effects polarities both deposited hetero- homocharges were investigated. occurrence first streamer discharges was detected electrically observed imaging. various streamers acquired associated with polarity intensity charges. Surface sprinkling specimen quantitatively evaluated mapping....

Partial discharges (PD) are influencing electrical insulating systems of high voltage devices.Typically, in laboratory and diagnostics AC tests focused on measuring analysis PD, a pure sinusoidal waveform is assumed.However, practice the spectral content working rarely so ideal additional components have significant impact discharge behaviour insulation systems.In this paper influence harmonics PD phase-resolved patterns evolution analysed.The presented experiments were conducted specimen...

A special group of exploitation stresses electrical insulation systems occurs at PWM (Pulse Width Modulated) inverter supply. The fast switching in drive applications, which has fundamental components 50/60 Hz, produces complex transients that the cable and motors insulation. Such conditions have essential influence on inception development partial discharges (PD) insulating subjected to non-sinusoidal stimuli. intensity dynamics these processes is a consequence local working electric field...

In order to investigate partial discharge behavior, its mechanism and dynamics, a novel methodology - chopped discharges has been elaborated. Typically, either during laboratory measurements or at on-site field testing, are detected by applying continuous sinusoidal excitation, most regularly 50/60 Hz other frequency according certain standards. A sequence consists of number packets base waveform, separated variable time delay. The waveform may be sinusoidal, square-like, trapezoidal with...

This study presents phase-resolved observations of partial discharge (PD) formation in air non-uniform electric field at various pressure conditions. The needle–plane equivalent electrode system refers both to external components high-voltage insulating systems and micro-sharpening the internal structure those systems. ionisation zone, accumulation space charge corresponding current pulses depend on configuration, voltage level, pressure, temperature humidity air. influence mechanism a...

This paper describes a correlation of partial discharge phase-resolved patterns with an optical imaging performed in non-uniform electric field configuration. The influence different dielectric barrier materials, placed on the plane electrode, propagation and surface landing was investigated. investigations were focused corona at positive polarity AC high voltage. It found that initial stage is similar for all cases whereas strongly depends material properties. observed streamer modes have...

The paper describes problem related to measurements and interpretation of partial discharges in insulation systems presence voltage harmonics, with special focus on epoxy resin based insulation. Laboratory testing system controlled generation periodic sinusoidal harmonically modified voltages was used. Several month investigations specially prepared samples have been done. Results linked high local electric field obtained point-to-plane electrodes configuration are presented. Due increasing...

This paper presents the methodology for phase-resolved partial discharge measurements in HVDC systems with a DC voltage containing trace AC harmonics or ripple. The measurement result of discharges is an indicator current condition high-voltage power devices’ insulation system. waveforms are not ideal DC, because different disturbances occurring naturally these can affect voltage. related to source voltage, and ripples provided by converter topology, be found proposes novel approach...

The Pulse Width Modulated (PWM) voltage waveforms produce complex overvoltages that stress the insulation of cables and rotating machines more severely than normal sinusoidal voltage. have a form fast switching pulses with very short rise time, composed repetitive sequences. Such conditions influence on inception activity partial discharges (PD) space charge accumulation in insulating systems. Paper presents some aspects this problem investigated for twisted-pair samples low motor wires....

A rising interest in DC systems at various voltage levels is still being observed. Such trends result heightened requirements of insulation stresses levels, and also motivate investigations into partial discharges (PD), initiating degradation processes systems. The mechanism PD forms represent a different class that cannot be directly compared with AC mechanism. depends on many factors determine the condition system, including pressure. Thus, it crucial to continue research phenomena...

The paper presents the effects of gradual temperature curing on dielectric properties epoxy nanocomposite samples. Samples were prepared based Class H resin filled with nano-alumina (Al2O3) for different wt% loadings (0.5 to 5.0 wt%) and two filler sizes (13 nm <50 nm), i.e., specific surface area values. During research, specimen sets cured gradually at increasingly higher temperatures (from 60 °C 180 °C). Broadband spectroscopy (BDS) was used determine characteristics constant loss...

This work presents the results of research on submicro- and nanocomposites with gradient properties, produced in a planned electrophoretic process. Epoxy-resin-based samples were filled TiO2 particles three different sizes (13 nm, 38 <1 µm) at four values average electric field Eav (0.0 Vmm−1, 125 250 500 Vmm−1) for 1 h each. Changes selected dielectric parameters (dielectric constant εr loss factor tanδ) composites analyzed using broadband spectroscopy (10−1 Hz to 105 Hz). The influence...

Exploitation stresses are causing degradation of high voltage insulation systems. The assessment intensity and dynamics these processes, being a consequence local, working electric field strength is considered mainly at the sinusoidal voltage. However in applications where power electronics converters used stress has usually form fast switching pulses composed repetitive sequences. Such pulse trains pose modulated width rise-and fall-times. conditions have essential influence on inception...

The present paper describes the research on mechanism of inrush current formation in a modern single-phase transformer, which insulation system must withstand stresses arising during these transient states. A complete and measurement-verified method for determining transformer waveforms other signals (e.g., fluxes voltages) is developed. This makes it possible to determine steady state solution. However, account electromagnetic phenomena, solving process long. To analyze dynamic response...

Power cables are one of the key components fast-growing HVDC transmission systems. The long-term reliability is closely related to occurrence partial discharges (PDs) in their insulation article analyzes conditions for formation PD pulses gaseous voids located XLPE an cable. For this purpose, MATLAB® procedure and coupled electro-thermal simulation model implemented COMSOL Multiphysics® software were used. FEM was used study effect applied voltage, temperature field (created loaded cable)...

Typically, in laboratory and diagnostics tests focused on measuring partial discharges, a pure sinusoidal voltage waveform is assumed. However, practice the spectral content of applied rarely so ideal additional components have significant impact discharge behavior electrical insulation systems. In this paper influence harmonics pattern evolution analyzed. The presented experiments were conducted specimens representing various defects high system, form protrusion, inclusion, delamination....

Progress in construction of electrical insulation systems needs new investigations partial discharges (PD) mechanisms. Working conditions and exploitation stresses, i.e. overvoltages, harmonics other disturbances have crucial influence on arising PD systems. Their discharge development is different from normal at nominal sinusoidal voltage. In such a cases interpretation measurement results (by classical or phase-resolved images method) could be more difficult. Paper presents non-sinusoidal...