The charge storage properties of corona-charged biaxially oriented polypropylene (BOPP) and unoriented polypropylene (PP) films have been studied. Thermally stimulated charge decay and open and short circuit thermally stimulated currents, were measured. A half-value charge decay temperature for BOPP was T/sub 0.4/=118 degrees C, 20 degrees C higher than for PP, hence giving greater charge storage stability for BOPP. The charge storage in BOPP is attributed predominantly to impurity trapping and space charge mechanisms. X-ray and differential scanning calorimetry methods were employed to obtain structural information. >
{"title":"Study of charge storage properties in biaxially oriented polypropylene","authors":"P. Karanja, R. Nath","doi":"10.1109/14.212254","DOIUrl":"https://doi.org/10.1109/14.212254","url":null,"abstract":"The charge storage properties of corona-charged biaxially oriented polypropylene (BOPP) and unoriented polypropylene (PP) films have been studied. Thermally stimulated charge decay and open and short circuit thermally stimulated currents, were measured. A half-value charge decay temperature for BOPP was T/sub 0.4/=118 degrees C, 20 degrees C higher than for PP, hence giving greater charge storage stability for BOPP. The charge storage in BOPP is attributed predominantly to impurity trapping and space charge mechanisms. X-ray and differential scanning calorimetry methods were employed to obtain structural information. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82622643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The commenters raise some questions regarding the measurements reported in the above titled paper (ibid., vol.27, pp.1026-39, October 1992) and their meaning. J.K. Nelson answers some of the questions in terms of the paper's objectives. >
{"title":"Discussion, with reply, on `Assessment of deterioration in epoxy/mica machine insulation' by Y.J. Ki","authors":"M. Danikas","doi":"10.1109/14.212256","DOIUrl":"https://doi.org/10.1109/14.212256","url":null,"abstract":"The commenters raise some questions regarding the measurements reported in the above titled paper (ibid., vol.27, pp.1026-39, October 1992) and their meaning. J.K. Nelson answers some of the questions in terms of the paper's objectives. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86325313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The sparkover characteristics of rod-rod and rod-plane gaps in air under DC voltages are reviewed. The linear characteristics of both configurations are associated with the prominence of streamer discharges during the prebreakdown phase. The limits of linearity are shown to be a function of humidity, gap spacing and electrode profile, all of which determine the predischarge mode. It is shown that the rod-plane gap offers a wider range of linearity than the rod-rod gap and that it can have a valid role as a DC voltage measurement tool. >
{"title":"Dielectric breakdown in nonuniform field air gaps","authors":"N. L. Allen, M. Boutlendj, H. A. Lightfoot","doi":"10.1109/14.212243","DOIUrl":"https://doi.org/10.1109/14.212243","url":null,"abstract":"The sparkover characteristics of rod-rod and rod-plane gaps in air under DC voltages are reviewed. The linear characteristics of both configurations are associated with the prominence of streamer discharges during the prebreakdown phase. The limits of linearity are shown to be a function of humidity, gap spacing and electrode profile, all of which determine the predischarge mode. It is shown that the rod-plane gap offers a wider range of linearity than the rod-rod gap and that it can have a valid role as a DC voltage measurement tool. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80660927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-speed streak photography of surface breakdown or flashover events along the surface of monocrystalline quartz and polycrystalline alumina specimens is reported. The initiation of visible luminosity was observed to be a function of surface properties of the samples. It has been shown that light could originate independently at the anode as well as at the cathode, indicating that the initiation of surface flashover could start in any region. The propagation rate of luminosity, bridging the electrodes completely, was found to vary depending upon the location at which the light originated. The initiation of light at the cathode is discussed on the basis of an electron induced collision-ionization process and of radiative recombination of electrons in the conduction band with the empty or positively charged traps or defect centers. The emission of light at the anode end is discussed along the lines of a recombination process involving field ionized traps or defect centers and conduction electrons and of the hole-induced excitation of activator or defect centers by inelastic collision. >
{"title":"Streak photography of the dynamic-electrical discharge behavior on insulator surfaces in vacuum","authors":"T. Asokan, T. Sudarshan","doi":"10.1109/14.192245","DOIUrl":"https://doi.org/10.1109/14.192245","url":null,"abstract":"High-speed streak photography of surface breakdown or flashover events along the surface of monocrystalline quartz and polycrystalline alumina specimens is reported. The initiation of visible luminosity was observed to be a function of surface properties of the samples. It has been shown that light could originate independently at the anode as well as at the cathode, indicating that the initiation of surface flashover could start in any region. The propagation rate of luminosity, bridging the electrodes completely, was found to vary depending upon the location at which the light originated. The initiation of light at the cathode is discussed on the basis of an electron induced collision-ionization process and of radiative recombination of electrons in the conduction band with the empty or positively charged traps or defect centers. The emission of light at the anode end is discussed along the lines of a recombination process involving field ionized traps or defect centers and conduction electrons and of the hole-induced excitation of activator or defect centers by inelastic collision. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91061922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thermally stimulated depolarization current (TSDC) and thermally stimulated polarization current (TSPC) measurements and the differential scanning calorimetry (DSC) method have been used for the investigation of thermal transitions in thermotropic poly( gamma -stearyl- alpha , L-glutamate). The beta peak (-80 degrees C) and alpha /sub 1/ and alpha '/sub 1/ peaks registered between -50 degrees C and 25 degrees C were attributed to movements of side chain dipoles. The alpha /sub 2/ peak, observed approximately=43 degrees C, was indicative of the melting of paraffinic side chains. The activation energies were determined for beta peaks and alpha /sub 2/ peaks at different heating rates. A good correlation between heating rate and the square of the maximum peak temperature was found, showing that these peaks are of dipolar origin. The alpha /sub 1/ and alpha /sub 2/ peaks were strongly influenced by thermal treatments. The position of alpha /sub 2/ was close to that determined by DSC. Depending on the thermal history of samples, the paraffinic side chain segments melted and crystallized over a large temperature range, suggesting the formation of crystallites with different dimensions. >
{"title":"Dielectric relaxations in thermotropic liquid crystalline polypeptides","authors":"E. Neagu, R. Neagu, W. Daly, I. Negulescu","doi":"10.1109/14.192248","DOIUrl":"https://doi.org/10.1109/14.192248","url":null,"abstract":"Thermally stimulated depolarization current (TSDC) and thermally stimulated polarization current (TSPC) measurements and the differential scanning calorimetry (DSC) method have been used for the investigation of thermal transitions in thermotropic poly( gamma -stearyl- alpha , L-glutamate). The beta peak (-80 degrees C) and alpha /sub 1/ and alpha '/sub 1/ peaks registered between -50 degrees C and 25 degrees C were attributed to movements of side chain dipoles. The alpha /sub 2/ peak, observed approximately=43 degrees C, was indicative of the melting of paraffinic side chains. The activation energies were determined for beta peaks and alpha /sub 2/ peaks at different heating rates. A good correlation between heating rate and the square of the maximum peak temperature was found, showing that these peaks are of dipolar origin. The alpha /sub 1/ and alpha /sub 2/ peaks were strongly influenced by thermal treatments. The position of alpha /sub 2/ was close to that determined by DSC. Depending on the thermal history of samples, the paraffinic side chain segments melted and crystallized over a large temperature range, suggesting the formation of crystallites with different dimensions. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72817042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dielectric properties of ferroelectric ceramic loaded P(VDF/TFE) polymer were studied in the frequency range 20 Hz to 1 GHz and at temperatures from 110 to 420 K. A simple relaxation with activation energy of 1.8 eV, observed at temperatures from 225 to 275 K and frequencies from 20 Hz to approximately 5 kHz, is related to the dielectric absorption in the amorphous phase of the polymer. At higher frequencies and temperatures complex and non-Arrhenius behavior of the main absorption of the O3-type composite is observed. Moreover, in the frequency range >
{"title":"Dielectric behavior of O3-type piezoelectric composites","authors":"J. Wolak","doi":"10.1109/14.192247","DOIUrl":"https://doi.org/10.1109/14.192247","url":null,"abstract":"Dielectric properties of ferroelectric ceramic loaded P(VDF/TFE) polymer were studied in the frequency range 20 Hz to 1 GHz and at temperatures from 110 to 420 K. A simple relaxation with activation energy of 1.8 eV, observed at temperatures from 225 to 275 K and frequencies from 20 Hz to approximately 5 kHz, is related to the dielectric absorption in the amorphous phase of the polymer. At higher frequencies and temperatures complex and non-Arrhenius behavior of the main absorption of the O3-type composite is observed. Moreover, in the frequency range >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89459043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The authors present the results of investigations concerning thermally stimulated depolarization currents and measurements of permittivity, loss factor and DC conductivity from X-ray and gamma -ray irradiated commercial 125 mu Estrofol polyethylene terephthalate films. Samples were irradiated with three different doses in different gaseous environments (air and N/sub 2/) and the electrical properties were measured as a function of time. A distribution of activation energies of relaxation processes responsible for the alpha and rho peaks was found by applying partial heating techniques. >
{"title":"Influence of X-rays and gamma -rays on the electrical properties of PET films","authors":"A. Gubanski, R. Stankiewicz","doi":"10.1109/14.192252","DOIUrl":"https://doi.org/10.1109/14.192252","url":null,"abstract":"The authors present the results of investigations concerning thermally stimulated depolarization currents and measurements of permittivity, loss factor and DC conductivity from X-ray and gamma -ray irradiated commercial 125 mu Estrofol polyethylene terephthalate films. Samples were irradiated with three different doses in different gaseous environments (air and N/sub 2/) and the electrical properties were measured as a function of time. A distribution of activation energies of relaxation processes responsible for the alpha and rho peaks was found by applying partial heating techniques. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90680835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An anomalous discharge has been found for poly(vinylidene fluoride) of form II and vinylidene fluoride copolymers in the paraelectric phase. The anomaly consists of a current peak during isothermal discharge. The peak time, i.e., the time at which the maximum current occurs in the discharge transient, depends not only on temperature and the electric field on charging, but also on the amount of ions in polymer samples and the thickness of the specimen. The amount of charge associated with the current peak is almost independent of the applied field, but depends on temperature. Study of the charge process revealed that poly(vinylidene fluoride) and vinylidene fluoride/trifluoroethylene copolymers exhibit polarization reversal or dielectric hysteresis at high temperatures and a low electric field. Thus, the anomalous discharge process is related to retarded discharge of the ionic charge bound or trapped in the crystalline regions of these copolymers. Polarization reversal at low electric field may be responsible for the anomalous behavior in homopolymer and copolymers of vinylidene fluoride. >
{"title":"Anomalous discharge in copolymers of vinylidene fluoride","authors":"Y. Murata, N. Koizumi","doi":"10.1109/14.192249","DOIUrl":"https://doi.org/10.1109/14.192249","url":null,"abstract":"An anomalous discharge has been found for poly(vinylidene fluoride) of form II and vinylidene fluoride copolymers in the paraelectric phase. The anomaly consists of a current peak during isothermal discharge. The peak time, i.e., the time at which the maximum current occurs in the discharge transient, depends not only on temperature and the electric field on charging, but also on the amount of ions in polymer samples and the thickness of the specimen. The amount of charge associated with the current peak is almost independent of the applied field, but depends on temperature. Study of the charge process revealed that poly(vinylidene fluoride) and vinylidene fluoride/trifluoroethylene copolymers exhibit polarization reversal or dielectric hysteresis at high temperatures and a low electric field. Thus, the anomalous discharge process is related to retarded discharge of the ionic charge bound or trapped in the crystalline regions of these copolymers. Polarization reversal at low electric field may be responsible for the anomalous behavior in homopolymer and copolymers of vinylidene fluoride. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86498701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Breakdown tests were conducted on a variety of polyethylenes and polypropylenes. High density polyethylene (HDPE) and polypropylene random copolymers (PPR) exhibited the highest breakdown strengths among the examined polyolefins. Model cables insulated with HDPE and PPR were manufactured, and the impulse breakdown strength of the HDPE cables made under some specific manufacturing conditions was 1.6*larger than that of conventional crosslinked polyethylene (XLPE). However, improvements were not observed in the impulse breakdown strength of PPR. The AC breakdown strength of HDPE and PPR cables also did not improve. The reason for the improvement in impulse breakdown strength of HDPE is the increased crystallinity of the insulating material, is brought about by the heat annealing applied to the cable in a manufacturing process. >
{"title":"Studies on the improvement of breakdown strength of polyolefins","authors":"T. Niwa, M. Hatada, H. Miyata, Takahashi Toru","doi":"10.1109/14.192237","DOIUrl":"https://doi.org/10.1109/14.192237","url":null,"abstract":"Breakdown tests were conducted on a variety of polyethylenes and polypropylenes. High density polyethylene (HDPE) and polypropylene random copolymers (PPR) exhibited the highest breakdown strengths among the examined polyolefins. Model cables insulated with HDPE and PPR were manufactured, and the impulse breakdown strength of the HDPE cables made under some specific manufacturing conditions was 1.6*larger than that of conventional crosslinked polyethylene (XLPE). However, improvements were not observed in the impulse breakdown strength of PPR. The AC breakdown strength of HDPE and PPR cables also did not improve. The reason for the improvement in impulse breakdown strength of HDPE is the increased crystallinity of the insulating material, is brought about by the heat annealing applied to the cable in a manufacturing process. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84326562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The variation of current densities on a plane cathode in air has been investigated in a positive point-plane gap configurations. This work is concerned with the effects of gap spacing, point diameter and humidity variations on the current density profiles, according to the type of corona regime produced at the point anode during predischarge development. Cases are considered where the point electrode is energized by a positive DC voltage producing either a pure glow or streamers, according to given particular experimental conditions such as point-plane gap spacing, point diameter and ambient absolute humidity. The results obtained show that the current density variation for positive corona in air does not always follow Warburg's law but depends upon the type of corona regime generated at the HV point anode. Comparisons are made with negative point-plane gaps. >
{"title":"Current-density distribution on a plane cathode in DC glow and streamer corona regimes in air","authors":"M. Boutlendj, N. L. Allen","doi":"10.1109/14.192243","DOIUrl":"https://doi.org/10.1109/14.192243","url":null,"abstract":"The variation of current densities on a plane cathode in air has been investigated in a positive point-plane gap configurations. This work is concerned with the effects of gap spacing, point diameter and humidity variations on the current density profiles, according to the type of corona regime produced at the point anode during predischarge development. Cases are considered where the point electrode is energized by a positive DC voltage producing either a pure glow or streamers, according to given particular experimental conditions such as point-plane gap spacing, point diameter and ambient absolute humidity. The results obtained show that the current density variation for positive corona in air does not always follow Warburg's law but depends upon the type of corona regime generated at the HV point anode. Comparisons are made with negative point-plane gaps. >","PeriodicalId":13105,"journal":{"name":"IEEE Transactions on Electrical Insulation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1993-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78793399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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