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Resin rich mica tapes are used in the high voltage rotating equipment industry in a variety of applications, from stator bar insulation to repair work to high voltage connections. There are several types, and manufacturers, of these mica tapes available in the market. The purpose of this paper is to share experiences in the application and processing of common materials, focusing on the critical taping...
This paper presents the potential distribution along the stress-grading system (Roebel Bar Type) under 50 Hz sinusoidal AC voltage based on the finite element method (FEM). In order to reduce the number of mesh elements and simulation time, a comparative study of two different approaches was examined using commercial software based on the Finite Element Method. The first one is a volume approach which...
In this contribution, data from experimental investigations are used to develop a numerical model allowing studying the impact of mineral oils degradation on the cooling of layer-type windings power transformers. From the obtained results, it was confirmed that oil decay products, especially sludge formation are also contributing factors to temperature rise in the transformers.
In recent years, time based maintenance of electrical of power equipment is gradually replaced by condition based maintenance. In China, smart grid acts as the great goal of the electric power industry, in which smart equipment such as smart transformer play important roles. As one part of the smart transformer, a smart multi-functional current sensor was designed to replace the leakage current sensor...
The thermal behavior of an industrial Low Voltage non-segregated three-phase busduct is analyzed by means of the comparison of a 3D numerical model with experimental results. This model has been carried out using COMSOL Multiphysics, software based on finite element method. The numerical model replicates the short-circuit test, using the same geometry configuration and the boundary conditions of the...
This paper conducted thermal aging experiments under 120°C to study the effects of passivator on insulating paper (board). Experiment group (oil containing passivator and typical materials inside transformer) and control group (oil containing typical materials inside transformer but no passivator) were prepared for thermal aging experiments, and the degree of polymerization of insulating paper, furfural...
Addition of metal inhibitor to corrosive transformer oil was employed to prevent the formation of semi-conductive Cu2S on copper surface. The formation of impermeable layer is the key process, however, little attention were paid on this process. Here, we performed aging experiment with benzotriazole and benzimidazole type inhibitors on copper strips in corrosive transformer oil. The experiment shows...
The identification of metrics or ranges of parameters for the detection of partial discharges by the acoustic emission method for the diagnosis and/or classification of power transformers according to their state is essential to support decisions about equipment stoppages at the proper time, i.e., before a failure occurs. This paper discusses these parameters based on the analyses of several field...
The study presents the results of experimental investigation of finding out the limit concentrations of DBDS and sulfur mercaptan for safe and prolonged operation of power transformers in the local environmental conditions of Saudi Arabia. For experimental investigation of limit concentrations of DBDS and sulfur mercaptan, new oil free of sulfur compounds was acquired. Four specimens of this were...
Partial discharge (PD) detection is an effective method for finding insulation defects in HV and EHV power cables. PD apparent charge is typically expressed in picocoulombs (pC) when the calibration procedure defined in IEC 60270 is applied during off-line tests. During on-line PD detection, measured signals are usually denoted in mV or dB without transforming the measured signal into a charge quantity...
In the past years a long-lasting aging experiment on PILC-cables with a nominal voltage of 20 kV has been carried out. In order to verify the results and to make those data utilizable for the asset management, a new project with the focus on field measurements has been started. Thus, a diagnostic system appropriate for field measurements, a cable test van, has been designed comprising both a 50 Hz...
For outdoor covered overhead lines, the service life normally depends on cable weathering and environmental stress. This paper presents the comparison of ageing deterioration of crosslinkable polyethylene compounds for outdoor covered overhead lines by using an accelerated weathering test. The effect of carbon black on crosslinkable polyethylene compounds was correlated as an ultraviolet absorber...
A method for measuring leakage current in LDPE insulated miniature cables containing volatile additives is presented. It is shown that with the presented method the volatiles are sufficiently contained in the test object even at temperatures up to 90 °C. This is achieved through non permeable encapsulation around the outer insulation screen (extruded semiconducting layer). Guard electrodes are adopted...
In this paper, two types of nanocomposites were prepared by ball milling techniquee The first type consists of 5% untreated titanium dioxide (TiO2) incorporated into LDPE. For the second one, 5% commercial TiO2 chemically treated with trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) as dispersant was ball-milled with LDPE. The microscopic observation by Atomic Force Microscopy (AFM)...
The aim of this paper is to study the influence of uneven wetting conditions on the E-field distribution and leakage current along composite insulators under dense cold fog. The tests were carried out in an environmental chamber to simulate natural climate conditions. In the experimental investigation two conditions were considered: the presence of uniform contamination levels and uneven wetting pattern...
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