Performance Of Insulation Systems Research Articles

Integrated performance of insulation systems: the experience and technical know-how of Totalproof

Integrated performance of insulation systems: the experience and technical know-how of Totalproof

The Streamers Dynamics Study by an Intelligent System Based on Neural Networks

The formation and propagation of streamers is an important precursor to determine the characteristics of electrical breakdown of many HV electrode configurations. Understanding of the study of the interaction between the polymer surface and the development process of the streamer is of major importance when we want to improve internal and external performance insulation systems. In this context, a numerical tool using neural networks is developed. This model allows evaluating the speed of streamers as a function of the amplitude of voltage initiation and the nature of the insulating materials. For this, a database was created to train the neural model from a laboratory model. This investigation builds a database for predicting the propagation of streamers on the polymers surface by different neuronal methods and this presents an interesting tool for estimating the propagation phenomena in functions of very important parameters

Partial Discharges in Motor Fed by Inverter: From Detection to Winding Configuration

This paper reports non-intrusive partial discharge (PD) investigations on aeronautic and electric vehicle motors fed by inverter drive under variable environmental conditions. A representative test procedure and experimental setup based on operating aeronautic conditions are essential to ensure the accuracy and reliability of PD test on aircraft systems to make informed decisions on insulation system design choice. The aim of this paper is to demonstrate the feasibility of PD test of the insulation system on a different type of motor under such conditions, both electrically and environmentally. To do so, a study of the pressure influence on the frequency spectrum of discharges was carried out. This analysis defines the ability of the non-intrusive measurement system to detect PDs in equipment operating at low pressure. This paper also presents some tests on an industrial test bench to validate the ability of the non-intrusive test method and the associated numerical signal processing to detect PD in motors fed by PWM voltage. Then, an analysis is carried out on a motor to find out which voltage magnitude trigger PD events. The study helps to realize the benefits of using an inverter based test method to find the limits of the insulation system. It is shown that a representative insulation system performance picture could be drawn experimentally and used to enhance insulation design and manufacturing choices. The paper concludes with an analysis of results and thoughts about future work regarding advanced test procedure.

Aerogel blankets: From mathematical modeling to material characterization and experimental analysis

One of the most feasible solutions for reducing the global energy consumption and associated CO2 emissions, is through usage of more efficient insulation systems in buildings and refrigeration units. Commercialization of high-performance thermal insulation will significantly contribute to environmentally sustainable future development. Aerogel composites provide superior thermal resistance and enable new design approaches for high performance insulation systems. This paper presents a theoretical and experimental study on the effective thermal conductivity of aerogel composites. The analytical model represents aerogel composites with a unit cell consisting of a cylindrical fiber surrounded by a packed bed of aerogel particles. The model accounts for various heat transfer mechanisms, namely conduction in the solid, gas conduction, and radiation. The properties and microstructure of two types of aerogel composites (Cryogel® Z and ThermalWrap™) were studied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and Fourier transform infrared spectroscopy (FTIR). The apparent thermal conductivity of the samples of aerogel blanket were measured using heat flow meter (HFM) at mean temperature ranging from −20°C to 80°C and the results polished thorough two-thickness method to de-convolute the effect of thermal contact resistance (TCR), between the sample and HFM hot and cold plates, from the apparent thermal conductivity values. The effective thermal conductivity results were found to increase from 0.0135 to 0.0175Wm−1K−1 for Cryogel® Z and 0.0188 to 0.0271Wm−1K−1 for ThermalWrap™ at mentioned temperature range. The analytically predicted variation in the effective thermal conductivity as a function of temperature agreed well with the experimental data. Using the proposed model, parametric studies were performed to investigate the effect of blanket porosity and fiber thermal conductivity on the effective thermal conductivity of aerogel composites.

Study on voltage-number characteristics of transformer insulation under transformer invading non-standard lightning impulses

According to the IEC Standard, the insulation performances of power apparatus under lightning impulse voltages are evaluated by the withstand test of standard lightning impulse voltage, with the wave front/tail time of 1.2/50 μs. However, the standard lightning impulse voltage originally obtained from the transmission lines or triggering lightning towers, is quite different from the invading lightning impulse voltage in the power transformers. Hence, in this work, an attempt has been made to obtain the waveform characteristics of invading lightning impulses in power transformers using an overvoltage online monitoring system. Energy Method was then proposed to convert the recorded oscillatory waveform into double-exponential waveform defined by IEC Standard. And the statistical waveform parameters of recorded invading lightning impulses, namely, the non-standard lightning impulses, were determined based on the Energy Method. Current insulation assessment methods, for example, the V-t characteristics, are far from satisfactory to meet the demand of insulation design for the power apparatus, whereas the impulse breakdown voltage-number of voltage applications characteristics (V-N characteristics) could well evaluate the long term performance of insulation system. Therefore, we experimentally identified the V-N characteristics of oil paper insulation under impulse voltage with different waveforms, including non-standard lightning impulse voltage, and then mathematically analyzed the obtained data. At last, the influence of wave front/tail time on the V-N characteristics of oil paper insulation was experimentally studied. The test results indicate that the insulation performances of oil paper insulation under repeated nonstandard lightning impulse voltages and under standard switching impulse voltages were better than that under repeated standard lightning impulse voltages. And the capacity to withstand repeated voltage became increasingly stronger with the increase in wave front time or the decrease in wave tail time. The breakdown voltage, however, was only related to the wave front time of applied impulse voltage.

Simulation Study on HST Distribution for ONAN Oil-Filled Transformer

Advanced monitoring system and preventive maintenance introduced on serviced transformer successfully reducing the equipment malfunction and breakdown rate. However, faults that occur and developed inside the transformer can be very unpredictable. One of the measures can be taken is to analyse the hottest spot temperature (HST) of the transformer, because high temperature will affect transformer insulation system performance and its life-span. HST distribution study on the transformer surface body can give better understanding on how HST will behave at inner and outer transformer surface tank, so that it can be correlated to the actual temperature inside the transformer. Therefore, this paper presents a simulation study on 100 KVA ONAN oil-filled type of distribution transformer with three types of HST intensity. Result shows that temperature distribution projectile is tending to go upwards in the insulation oil and inward into the winding. Moreover, location of HST can be identified by comparing the temperature distribution plot with and without HST.

Experimental simulation of effects of copper sulphide on insulation system of transformers

The presence of Corrosive sulphur in mineral transformer oil affects the performance of insulation system of transformers. In this paper results of experimental investigations carried out on voltage current characteristics and insulation resistance of paper oil insulation in presence of copper sulphide are presented and discussed. A model for copper sulphide migration is proposed to explain the increase in leakage current and reduction in insulation resistance. Existence of two regions in voltagecurrent characteristics, one dependent on the insulation properties of paper oil insulation and other due to semi-conducting copper sulphide is discussed and explained.

ANALYSIS ON DEGRADATION AND DEFORMATION OF TRANSFORMER INSULATION SYSTEM

Performance of insulation system of power transformer is essential to ensure better performance of power network. Most of the power and distribution transformers in service are aged and, have experienced several thermal and electrical stresses due to varying loading conditions, in addition to ageing. The rate of degradation and hence, the useful life of the insulation system mainly depends on the variation of operational stresses. Due to the progress in insulation degradation, the dielectric strength of the insulating oil and paper over transformer winding may reach to a point such that it could not withstand any small abnormal currents and voltages. In order to maintain the quality of system operation it is necessary to keep the transformer in good condition. This needs appropriate maintenance based on reliable diagnostics. In this paper experimental results on the application of frequency response analysis (FRA) for the diagnosis of power transformers. Frequency Response of Transformer, also serves for assessing the deformation process.

Study of the effect of the initiation voltage amplitude and the nature of the insulating materials on the evolution of streamers by neural networks

To determine the characteristics of electrical breakdown of many HV electrode configurations, the formation and propagation of streamers is an important precursor to achieve this goal. It’s a major importance, when we want to improve internal and external performance insulation systems, to understand and study the interaction between the polymer surface and the development process of the streamer. A numerical tool using neural networks is developed in this context. This model allows evaluating the speed of streamers as a function of the amplitude of voltage initiation and the nature of the insulating materials. Indeed, a database was created from a laboratory model, to train different neuronal methods for predicting the evolution of streamers on the polymers surface which presents an interesting tool for estimating the propagation phenomena.

Economic thermal insulation thickness for pipes and ducts: A review study

Energy conservation has become an increasingly important issue for all sectors, particularly in industry. Therefore, the thermal performance of insulation systems and their influence on heat loss/gain in various applications in addition to economic considerations have received increased attention in recent years. In this study, a literature review of papers that addressed the optimum economic thickness of the thermal insulation on a pipe or duct with different geometries used in various industries was carried out. The studies related to determining the critical insulation thickness for different geometries including circular shapes were investigated. The heat transfer equations, the basic results, the optimization procedures and the economic analysis methods used in the studies were presented comparatively. Additionally, a practical application example based on optimizing the insulation thickness on a pipe was performed, and the effective parameters of the optimum thickness were investigated.

Performance evaluation of an attic radiant barrier system using three-dimensional transient finite element method

A three-dimensional transient finite element model was developed to evaluate the thermal performance of an attic radiant barrier system as an energy-efficient insulation technology. The finite element model simulates different heat transfer modes including convection, radiation, and conduction. Hourly experimental data collected in a housing complex in Zachary, LA, were used to validate the finite element analysis. Upon validation, the design variables and their influence on the performance of the radiant barrier insulation system were investigated. Among the different design variables, the presence of an air gap on both sides of the radiant barrier had a significant effect on the performance of the insulation system.

Extending the service life of insulation systems through the use of chemically active components

The effect of ageing on the performance of insulation systems is studied. A program has been developed that determines the residual life of polymeric insulation taking into account all of the factors affecting the insulation’s state. Experimental data on the effect of the chemically active components of the substance adsorbed in the insulation microflaws and the effect of the epoxy oligomer on polyarylates during production are presented. A way to remove the structural and production flaws facilitating the active ageing process is considered.

Insulation performance under switched voltage waveforms

The increasing use of IGBT-controlled pulse-width modulated voltage waveforms for motor drive applications has prompted many studies to evaluate their impact on motor insulation system performance. This article provides an overview of the issues raised by examining the individual contributions of the various waveform features.

Two-Dimensional Heat Transfer Effects on Vacuum and Reflective Insulations

Heat transfer in directions normal to the imposed temperature gradi ent can have an important influence on the overall performance of insulation systems. An analysis of two-dimensional heat transfer in vacuum insulations and reflective in sulations is presented.