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# IEEE Transactions on Dielectrics and Electrical Insulation

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Displaying Results 1 - 25 of 27
• ### Laser triggering of electric breakdown in liquids

Publication Year: 1994, Page(s):680 - 691
Cited by:  Papers (13)
| | PDF (980 KB)

Electric breakdown in semihomogeneous geometries has been studied in n-hexane and transformer oil using a laser triggering method for fields far below the spontaneous breakdown field. The method uses a laser-produced plasma to initiate the breakdown. Strong self focusing in the liquids was limited by increasing the numerical aperture of the laser beam to >0.20 prior to focusing. Electrical brea... View full abstract»

• ### Potential buildup in samples charged by successive low-energy pulses

Publication Year: 1994, Page(s):563 - 568
| | PDF (348 KB)

We present a calculation for the charging of a dielectric sample submitted in open circuit to a series of consecutive, identical, electron pulses of low energy. The calculation is based on deep trap kinematics and takes full account of space charge effects. Electric field profiles and the potential buildup after n⩽10 pulses are presented, allowing one to infer the important parameter μτ... View full abstract»

• ### Self-trapping of electrons in liquid nitrogen

Publication Year: 1994, Page(s):724 - 727
Cited by:  Papers (7)
| | PDF (216 KB)

A possibility of electron self trapping in nitrogen is discussed. It is found that electrons are free when injected in liquid N2 near the triple point and localized inside bubbles and in the gaseous phase, far enough from the critical point. On the saturation line near the critical point a transition of electrons from bound to free states takes place View full abstract»

• ### Bubble formation in synthetic insulating liquids in a pulsed divergent electric field

Publication Year: 1994, Page(s):672 - 679
Cited by:  Papers (10)
| | PDF (552 KB)

This is a study of high field conduction phenomena in two aromatic insulating liquids (monobenzyltoluene and dibenzyltoluene) in a point-plane electrode geometry. These liquids behave qualitatively like saturated hydrocarbons; current instability (electron avalanche) for high enough fields near the negative point giving rise to a current pulse regime, which causes the formation of bubbles by local... View full abstract»

• ### The electric moment contribution to the piezoelectricity of PVDF

Publication Year: 1994, Page(s):553 - 562
Cited by:  Papers (10)
| | PDF (744 KB)

Basically the piezoelectric constant is composed of two contributions, i.e. of mechanical load-induced changes of the sample electric moment at fixed sample shape (moment term') and of mechanical load induced changes of the sample shape at fixed sample electric moment (shape term'). In the present paper, the contribution of the material's permittivity to the moment terms of the hydrostatic piezo... View full abstract»

• ### Loss and recovery of hydrophobicity on RTV coating surfaces

Publication Year: 1994, Page(s):604 - 614
Cited by:  Papers (19)
| | PDF (776 KB)

Studies are reported on decay and recovery of hydrophobic properties on clean and contaminated surfaces of silicone rubber based RTV coating. Treatment that led to hydrophobicity losses were water immersion and water condensation with and without a presence of dc electric field. Contact angles (receding angles) and surface leakage currents were measured on the treated surfaces. A suppression of th... View full abstract»

• ### Initiation and propagation thresholds of positive prebreakdown phenomena in hydrocarbon liquids

Publication Year: 1994, Page(s):702 - 708
Cited by:  Papers (43)  |  Patents (1)
| | PDF (476 KB)

This paper presents an experimental study of the initiation of positive streamers under step voltage in point-plane geometry, in a number of hydrocarbon liquids. The experimental conditions (point tip radius, pulse risetime, gap length) were strictly controlled in order to take valid measurements of the initiation fields and threshold propagation voltages of streamers. Transient currents associate... View full abstract»

• ### Influence of co-field motion on the conduction current in oil under nonuniform dc fields

Publication Year: 1994, Page(s):734 - 740
Cited by:  Papers (5)
| | PDF (440 KB)

The effect of enforced co-field motion on conduction current in transformer oil was studied using a point-to-plane electrode geometry. Tests were carried out on degassed oil and gas-saturated oil for negative and positive point polarities using both a solid and a mesh-plane electrode, and gaps ranging from 200 to 900 μm. For stationary oil the presence of oxygen decreased the conduction current... View full abstract»

• ### Dielectric behavior of highly conducting perfluoropolyether water-in-oil microemulsions

Publication Year: 1994, Page(s):716 - 723
Cited by:  Papers (7)
| | PDF (420 KB)

The dielectric and conductive properties of a new ternary water-in-oil microemulsion consisting of perfluoropolyether (PFPE) oil, PFPE surfactant and water, were investigated by an impedance analysis technique in the frequency range of 5 Hz to 100 MHz. The trend of both the electrical conductivity and the static permittivity was analyzed as a function of the temperature in the interval from -10 to... View full abstract»

• ### Measurement of the 2-dimensional electric field vector in dielectric liquids

Publication Year: 1994, Page(s):747 - 753
Cited by:  Papers (19)
| | PDF (424 KB)

A new measurement technique for two-dimensional electric field vectors (electric field intensity and its direction) in liquid dielectrics has been developed in this study. The theoretical equation for measuring the electrical field vector is derived for the optical system which consists of a He-Ne laser, polarizer, quarter-wave plate, test cell with nonuniform electric field, nonpolarizing beam sp... View full abstract»

• ### Basic electrical processes in dielectric liquids

Publication Year: 1994, Page(s):630 - 643
Cited by:  Papers (32)
| | PDF (1072 KB)

The basic processes of electrical conduction in dielectric liquids are reviewed, attention being drawn to the similarities between conductive electrolytes and insulating liquids. The concepts of the electronic amorphous solid state are employed to provide a framework for the review. The conditions at metal electrodes can be incorporated naturally into the scheme, and it is known that the space cha... View full abstract»

• ### High-speed photography of PMMA breakdown under ns pulse voltages

Publication Year: 1994, Page(s):754 - 756
Cited by:  Papers (2)
| | PDF (168 KB)

The electrical breakdown process in polymethyl methacrylate for a point-to-plane gap configuration has been studied using an image convertor camera and a nanosecond rectangular HV pulse generator. The propagation velocity of the breakdown channel for positive polarity is estimated to be ~80 km/s. The velocity is of the same order as that of secondary fast streamers in several hydrocarbon liquids View full abstract»

• ### Some steps toward the automation of the design of composite dielectric structures

Publication Year: 1994, Page(s):663 - 671
Cited by:  Papers (9)
| | PDF (688 KB)

Based on the physical mechanisms believed to underlie the ac electrical breakdown of liquid/solid structures, a volume theory of failure is used to justify the application of a semi-empirical cumulative stress criteria for the assessment of dielectric integrity. The method advocated is extended through the use of a complex Laplace equation to permit the analysis of structures having simultaneous c... View full abstract»

• ### Comparison between water-treed and deteriorated regions. Electrical tree precursor

Publication Year: 1994, Page(s):597 - 603
Cited by:  Papers (19)
| | PDF (488 KB)

When polyethylene is subjected to high fields in the presence of water, a water tree may be formed. However, under dry conditions a `deteriorated region' is gradually formed before the initiation of an electrical tree. The experimental results suggest some similarities in structure and properties between the deteriorated and the water-treed regions. FTIR analysis shows that there are common polar ... View full abstract»

• ### Prebreakdown phenomena in mineral oil under step and ac voltage in large-gap divergent fields

Publication Year: 1994, Page(s):692 - 701
Cited by:  Papers (32)
| | PDF (668 KB)

This paper presents an experimental study of the propagation of prebreakdown phenomena in transformer oil, in large point-plane gaps (5 to 20 cm), in positive polarity under step and ac voltages. The prebreakdown phenomena are characterized via the simultaneous recordings of transient currents, charges, photocurrents, and high-speed photographs of the emitted light. In these experimental condition... View full abstract»

• ### Control of corona characteristics with third electrode and bias voltage

Publication Year: 1994, Page(s):569 - 577
Cited by:  Papers (5)
| | PDF (520 KB)

A novel corona control system consisting of a point-to-plate air gap with a cylindrical third electrode has been proposed. Negative and positive coronas from a point-to-plate air gap with a cylindrical third electrode set up close to the corona point of the needle have been investigated with emphasis on the role of the cylindrical third electrode, the bias voltage amplitude and polarity. It was fo... View full abstract»

• ### Flow electrification in power transformers. Explanation of the wall-current measurements

Publication Year: 1994, Page(s):728 - 733
Cited by:  Papers (15)
| | PDF (352 KB)

The aim of our work is to understand better the mechanisms of flow electrification due to oil circulating inside a rectangular pressboard channel. This research has been done because of technical incidents in power transformers in which oil is flowing past pressboard with a velocity in the range of several meters per second. A possible explanation of the wall current observed along the channel is ... View full abstract»

• ### Electrical strength of paper-oil insulation subjected to composite voltages

Publication Year: 1994, Page(s):615 - 623
Cited by:  Papers (13)
| | PDF (608 KB)

The results of a composite voltage, ac with lightning impulse (LI) tests of a paper-oil insulation model are presented. It was demonstrated that the presence of the background ac voltage leads to a decrease in LI breakdown voltage. This is particularly conspicuous at opposite polarities. The dispersion of LI breakdown voltages decreases save for the case when the LI is superimposed on the opposite... View full abstract»

• ### Thermal bubble breakdown in liquid nitrogen under nonuniform fields

Publication Year: 1994, Page(s):709 - 715
Cited by:  Papers (12)
| | PDF (412 KB)

The electrical forces acting on thermally induced bubbles in nonuniform field gaps with/without fins and the correlation between bubble behavior and dielectric characteristics in liquid nitrogen are studied. The results show that the gradient force and Maxwell stress strongly affect the bubble dynamics and bubble shape in the gap. Especially the pronounced gradient force near the fin tip reduces t... View full abstract»

• ### Effect of electrode ice layer on prebreakdown current in liquid nitrogen

Publication Year: 1994, Page(s):741 - 746
Cited by:  Papers (5)
| | PDF (316 KB)

The effect of ice on dc prebreakdown events was investigated using a needle-to-plane electrode system in liquid nitrogen at 77.3 K. It was found that H2O ice has marked effects on prebreakdown current, corona onset voltage and breakdown voltage. The breakdown voltage at atmospheric pressure depends on microscopic cracks in H2 O ice View full abstract»

• ### Laser-induced breakdown characteristics of nonuniform dc corona discharge fields

Publication Year: 1994, Page(s):590 - 596
| | PDF (408 KB)

Laser-induced breakdown of nonuniform field gaps in atmospheric air was caused by an XeCl excimer laser. This laser beam was focused on the center of a rod-to-plane, needle-to-plane or hemisphere-to-plane gap with dc voltage. The laser energy dependency of breakdown voltage was investigated for positive and negative applied voltages and gap lengths of 15 to 25 mm. It was found that the positive br... View full abstract»

• ### Fast and slow electrons in liquid Ar and N2 mixtures

Publication Year: 1994, Page(s):644 - 647
Cited by:  Papers (3)
| | PDF (220 KB)

Fast and slow electron current signals in N2/Ar liquid mixtures have been observed. From the fast signal, the drift velocity and life time of delocalized electrons in the liquid with N2 molar fractions X=N2/(N2+Ar) below 20 mol% were obtained for field strengths E between 5 and 45 kV/cm. The mobility for delocalized electrons in the liquids was shown to ... View full abstract»

• ### Effect of partial discharges on impregnated polypropylene films

Publication Year: 1994, Page(s):578 - 584
Cited by:  Papers (4)
| | PDF (492 KB)

The effect of partial discharges in benzyltoluene upon impregnated polypropylene films has been studied in a sphere/plane electrode geometry. It is shown that discharges even with a small apparent charge (~1 pC) cause a significant decrease of the breakdown strength of the film. The addition of an epoxy compound to the liquid notably reduces the film degradation characterized by the breakdown volt... View full abstract»

• ### Insulation thickness determination of polymeric power cables

Publication Year: 1994, Page(s):624 - 629
Cited by:  Papers (6)
| | PDF (448 KB)

An analytical expression has been derived for calculating insulation wall thicknesses of single-core polymeric power cables from considerations of discharges in voids. For 10 to 30 kV cables of small conductors (16 to 50 mm2), good agreement has been obtained between the thicknesses calculated by the expression and those specified in the IEC Standard, provided that 50 μm is defined a... View full abstract»

• ### Work functions for a HV cathode in nonpolar liquids

Publication Year: 1994, Page(s):657 - 662
Cited by:  Papers (6)
| | PDF (388 KB)

When negative HV is applied to a needle of small radius of curvature (rp<0.2 μm) in nonpolar liquids, a detectable field emission current (I>×10-12 A) is observed above a voltage UFN, the Fowler-Nordheim law. For larger point radii, only a regular current pulse regime is detected above a threshold voltage Us (Trichel regime). Analysis of t... View full abstract»

## Aims & Scope

IEEE Transactions on Dielectrics and Electrical Insulation contains topics that are concerned with dielectric phenomena and measurements, with development and characterization of gaseous, vacuum, liquid and solid electrical insulating materials and systems; and with utilization of these materials in circuits and systems under condition of use.

Full Aims & Scope

Editor-in-Chief
Reuben Hackam